Arthroplasty/Joint Replacement

A common entity, osteoarthritis (OA) at the base of the thumb is largely caused by the unique anatomy and biomechanics of the thumb carpometacarpal (CMC) joint.¹ Radiographically evident CMC degeneration occurs in 40% of women and 25% of men over age 75 years, making the thumb CMC joint the most common site of surgical reconstruction for upper extremity OA.^2,3

Over the past 40 years, numerous surgical techniques for managing thumb CMC-OA have been described. These include volar ligament reconstruction, first metacarpal osteotomy, CMC arthrodesis, CMC joint replacement, and trapeziectomy. Trapeziectomy can be performed in isolation or in combination with tendon interposition, ligament reconstruction, or ligament reconstruction and tendon interposition (LRTI).^4-20 The authors of a recent systematic review concluded there is no evidence that any one surgical procedure for CMC-OA is superior to another in terms of pain, function, satisfaction, range of motion, or strength.⁴ Nevertheless, a recent survey found that 719 (62%) of 1156 US hand surgeons used LRTI as the treatment of choice for advanced CMC-OA.²¹

Our detailed literature search yielded no other database studies characterizing current trends in the practice patterns of US orthopedic surgeons who perform interposition arthroplasty for CMC arthritis. Analysis of these trends is important not only to patients but also to the broader orthopedic and health care community.²²

We conducted a study to investigate current trends in CMC interposition arthroplasty across time, sex, age, and region of the United States; per-patient charges and reimbursements; and the association between this procedure and concomitantly performed carpal tunnel syndrome (CTS) and carpal tunnel release (CTR). In addition, we compared incidence of CMC interposition arthroplasty with that of CMC arthrodesis.

Patients and Methods

All data were derived from the PearlDiver Patient Records Database (PearlDiver Technologies), a publicly available database of patients. The database stores procedure volumes, demographics, and average charge information for patients with International Classification of Diseases, Ninth Revision (ICD-9) diagnoses and procedures or Current Procedural Terminology (CPT) codes. Data for the present study were drawn from the Medicare database within the PearlDiver records, which has a total of 179,094,296 patient records covering the period 2005–2011. This study did not require institutional review board approval, as it used existing, publicly available data without identifiers linked to subjects.

PearlDiver Technologies granted us database access for academic research. The database was stored on a password-protected server maintained by PearlDiver. ICD-9 and CPT codes can be searched in isolation or in combination. Search results yield number of patients with a searched code (or combination of codes) in each year, age group, or region of the United States, as well as mean charge and mean reimbursement for the code or combination of codes.

We used CPT code 25447 (arthroplasty, interposition, intercarpal, or CMC joints) to search the database for patients who underwent thumb CMC interposition arthroplasty. Although this code does not specify thumb, we are unaware of any procedure (other than thumb CMC interposition arthroplasty) typically given this code. Our search yielded procedure volumes, sex distribution, age distribution, region volumes, and mean per-patient charges and reimbursements for each CPT code. We then searched the resulting cohort for CTS (ICD-9 code 354.0), endoscopic CTR (CPT code 29848), and open CTR (CPT code 64721) to find CTR performed concomitantly with CMC interposition arthroplasty. Last, patients were tracked in the database past their surgery date to evaluate for postoperative physical or occupational therapy evaluations within 6 months (using CPT codes appearing in at least 1% of the cohort: 97001, 97003, 97004, 97110, 97112, 97124, 97140, 97150, 97350, 97535) and postoperative thumb, hand, or wrist radiographs within 6 months (using CPT codes appearing in at least 1% of the cohort: 73140, 73130, 73110). To ensure adequacy of 6-month postoperative data, we included in this portion of the study only those patients with surgery dates between 2005 and 2010.

For comparative purposes, we also searched the database for patients who underwent thumb CMC arthrodesis within the same period—using CPT codes 26841 and 26842 (arthrodesis CMC joint thumb, with or without internal fixation; with or without autograft) and CPT code 26820 (fusion in opposition, thumb, with autogenous graft).

Overall procedure volume data are reported as number of patients with the given CPT code in the database output in a given year. Age-group and sex analyses are reported as number of patients reported in the database output and as percentage of patients who underwent the CPT code of interest that year. Mean charges and reimbursements are reported as results by the database for the code of interest (CPT 25447). Data for the region analysis are presented as an incidence, as there is an uneven distribution of patient volumes among regions. This incidence is calculated as number of patients in a particular region and year normalized to total number of patients in the database for that particular region or year. Regions are defined as Midwest (IA, IL, IN, KS, MI, MN, MO, ND, NE, OH, SD, WI), Northeast (CT, MA, ME, NH, NJ, NY, PA, RI, VT), South (AL, AR, DC, DE, FL, GA, KY, LA, MD, MS, NC, OK, SC, TN, TX, VA, WV), and West (AK, AZ, CA, CO, HI, ID, MT, NM, NV, OR, UT, WA, WY).

Chi-squared linear-by-linear association analysis was used to determine statistical significance with regard to trends over time in procedure volumes, sex, age group, and region. For all statistical comparisons, P < .05 was considered significant.

Results

In the database, we identified 41,171 unique patients who underwent CMC interposition arthroplasty between 2005 and 2011. Over the 7-year study period, number of patients who had CMC interposition arthroplasty increased 46.2%, from 4761 in 2005 to 6960 in 2011 (P < .0001) (Table 1, Figure 1). Throughout this period, females underwent CMC interposition arthroplasty more frequently than males at all time points (P < .0001). Overall ratio of female to male patients, however, changed significantly. In 2005, 18.1% of all CMC interposition arthroplasties were performed on male patients; this increased to 23.9% of all procedures by 2011 (P < .0001) (Figure 2). Table 1 presents an age-group analysis. There were no significant differences in relative percentage of patients in any given age group who underwent CMC interposition arthroplasty over the study period.

Analysis of overall procedure incidence by region revealed significant increases in all regions (P < .0001), ranging from 18.5% (West) to 54.5% (Northeast) (Figure 3). At all time points, the incidence of CMC interposition arthroplasty was significantly lower in the Northeast than in any other region and compared with the overall average.

Between 2005 and 2011, there were significant increases in both per-patient charges and reimbursements for CMC interposition arthroplasty (Figure 4). Mean per-patient charge increased from $2676 in 2005 to $4181 in 2011 (P < .0001), and mean per-patient reimbursement increased from $1445 in 2005 to $2061 in 2011 (P < .0001). The discrepancy between charge and reimbursement increased throughout the study period: Reimbursement in 2005 was 54.0% of the charge; this decreased to 49.3% by 2011 but was not statistically significant (P = .08).

Overall, 40.9% of patients who underwent CMC interposition arthroplasty also had a CTS diagnosis. Between 15.5% and 17.3% of these patients had concomitant open or endoscopic CTR at time of CMC interposition arthroplasty (Table 2). Percentage of patients who underwent concomitant CTR did not change significantly from 2005 to 2011 (P = .139). Use of postoperative occupational and/or physical therapy increased significantly over the study period, from 33.5% of patients in 2005 to 50.7% of patients in 2010 (P < .0001). Use of postoperative thumb, hand, and/or wrist radiography also increased throughout the study period, from 7.4% of patients in 2005 to 18.7% of patients in 2010 (P < .0001).

We identified 1916 unique patients who underwent thumb CMC arthrodesis between 2005 and 2011. Over the 7-year study period, there was a 19.1% decrease in number of patients who underwent CMC arthrodesis, from 309 in 2005 to 250 in 2011 (P < .0001) (Figure 5). Significantly fewer patients had CMC arthrodesis compared with CMC interposition arthroplasty at all time points, ranging from 6.5% (thumb CMC arthrodesis:CMC interposition arthroplasty) in 2005 to 3.6% in 2011 (P < .0001).

Discussion

Our results demonstrated a significant increase in use of thumb CMC interposition arthroplasty in a US Medicare population, with an increase of more than 46% from 2005 to 2011. This finding supports the findings of a recent cross-sectional survey-based study in which 719 (62%) of 1156 surveyed US hand surgeons reported performing trapeziectomy with LRTI for advanced thumb CMC-OA.²¹ A prior study had similar findings, with 692 (68%) of 1024 American Society for Surgery of the Hand (ASSH) members performing LRTI and 766 (75%) of 1024 performing some type of CMC interposition with trapeziectomy for advanced CMC-OA.²³ This preference for CMC interposition arthroplasty prevails despite the fact that numerous studies have shown no superiority of any surgical procedure to another for CMC-OA in terms of pain, function, satisfaction, range of motion, and strength.^{7,15,18,19,24-34} Our data demonstrated that, not only does CMC interposition arthroplasty remain the most frequently used procedure for thumb CMC-OA, the incidence of CMC interposition arthroplasty continues to increase yearly.

The incidence of thumb CMC-OA is higher in women than in men, with more joint laxity a known contributor and subtle sex differences in trapezium geometry and congruence postulated as additional factors.^3,35,36 This trend was confirmed in the present study, as females underwent significantly more CMC interposition arthroplasties at all time points. It is interesting that the overall ratio of female to male patients changed significantly over the study period, with the percentage of patients who were male increasing from 18.1% in 2005 to 23.9% in 2011. No previous studies have captured such a large cross section of the population to establish this trend. Although this trend is not necessarily intuitive, potential theories include increased acceptance of CMC interposition arthroplasty as a surgical option for male patients, and potentially a larger number of male patients seeking medical care for thumb CMC-OA in recent years.

Increases in procedure incidence were noted in all regions of the United States, but the largest percentage increase occurred in the Northeast. Despite this increase, the Northeast also had significantly lower CMC interposition arthroplasty incidence compared with all other regions and with the average procedure incidence throughout the study period—demonstrating some regional bias as to treatment of thumb CMC-OA. Unfortunately, because of database limitations and lack of specific CPT codes for other treatment options for thumb CMC-OA, we cannot ascertain if other types of surgery are more frequently used in the Northeast.

CTS and thumb CMC-OA often coexist.³⁷ The estimated incidence of concomitant CTS in patients with CMC-OA is between 4% and 43%, but the rate of concomitant CTR and CMC interposition arthroplasty was not previously characterized in the literature.^38,39 Results of the present study supported these findings; 41% of patients who underwent CMC interposition arthroplasty in our study also had a CTS diagnosis, compared with 43% in the 246-patient study by Florack and colleagues.³⁸ We also found that 16% to 17% of patients who underwent CMC interposition arthroplasty underwent concomitant CTR; this rate remained consistent throughout the study period.

Our study demonstrated that, compared with CMC interposition arthroplasties, significantly fewer thumb CMC arthrodesis procedures were performed in the same Medicare population during the same period. Furthermore, the number of thumb CMC arthrodesis procedures declined yearly, with an overall decrease of 19% from 2005 to 2011. In a recent single-blinded, randomized trial, Vermeulen and colleagues⁴⁰ compared thumb CMC arthrodesis and trapeziectomy with LRTI. They found superior patient satisfaction and significantly lower complication rates in women who underwent LRTI versus arthrodesis. The study was terminated prematurely because of these complications and thus was underpowered to determine differences in specific outcome measures. Previous studies comparing arthrodesis and interposition arthroplasties reported inconsistent outcomes. Hart and colleagues⁴¹ found no significant differences in pain or function between CMC arthrodesis and LRTI at a mean 7-year follow-up in a level II randomized controlled trial. Hartigan and colleagues¹⁵ reached similar conclusions in their retrospective comparison of the procedures. Without clear evidence supporting arthrodesis over interposition arthroplasty, the majority of surgeons favor interposition arthroplasty for thumb CMC-OA. Among Medicare patients, use of thumb CMC arthrodesis continues to fall.

This national database study had several limitations, which are common to all studies using the PearlDiver database^22,42-47:

1. The power of the analysis depended on the quality of available data. Potential sources of error included accuracy of billing codes, and miscoding or noncoding by physicians.⁴⁶

2. Although we used this database to try to accurately represent a large population of interest, we cannot guarantee the database represented a true cross section of the United States.

3. For the Medicare population, the PearlDiver database indexes data only in 7-year increments. Although the study period was long enough to detect significant trends, some data may not be accurately captured over a 7-year period.

4. Patients were not randomized to a treatment group.

5. The PearlDiver database does not include any clinical outcome data. Therefore, we cannot comment on the efficacy of the reported evaluations and interventions.

6. There is no specific CPT code for thumb CMC interposition arthroplasty. However, we are unaware of a CMC interposition arthroplasty performed for any area besides the thumb. Theoretically, the study population can include a negligible percentage of patients who had interposition arthroplasty of a CMC joint other than the thumb.

7. The database cannot be searched for use of thumb CMC-OA surgical techniques other than CMC interposition arthroplasty or arthrodesis, as isolated trapeziectomy, volar ligament reconstruction, implant arthroplasty, and metacarpal osteotomy lack specific CPT codes.

Conclusion

Thumb CMC-OA is a common entity among Medicare patients. There are numerous surgical options for cases that have failed conservative treatment. Despite the lack of evidence that thumb CMC interposition arthroplasty is superior to other surgical options, the number of patients who had this procedure increased 46% during the 2005–2011 study period. Although the majority of patients who undergo CMC interposition arthroplasty are female, the percentage of male patients has increased significantly. More than 40% of patients who have CMC interposition arthroplasty are also diagnosed with CTS, and 16% to 17% of patients who have CMC interposition arthroplasty will have a concomitant CTR. CMC arthrodesis is used in significantly fewer patients of Medicare age, and its use has been declining.

A common entity, osteoarthritis (OA) at the base of the thumb is largely caused by the unique anatomy and biomechanics of the thumb carpometacarpal (CMC) joint.¹ Radiographically evident CMC degeneration occurs in 40% of women and 25% of men over age 75 years, making the thumb CMC joint the most common site of surgical reconstruction for upper extremity OA.^2,3

Over the past 40 years, numerous surgical techniques for managing thumb CMC-OA have been described. These include volar ligament reconstruction, first metacarpal osteotomy, CMC arthrodesis, CMC joint replacement, and trapeziectomy. Trapeziectomy can be performed in isolation or in combination with tendon interposition, ligament reconstruction, or ligament reconstruction and tendon interposition (LRTI).^4-20 The authors of a recent systematic review concluded there is no evidence that any one surgical procedure for CMC-OA is superior to another in terms of pain, function, satisfaction, range of motion, or strength.⁴ Nevertheless, a recent survey found that 719 (62%) of 1156 US hand surgeons used LRTI as the treatment of choice for advanced CMC-OA.²¹

Our detailed literature search yielded no other database studies characterizing current trends in the practice patterns of US orthopedic surgeons who perform interposition arthroplasty for CMC arthritis. Analysis of these trends is important not only to patients but also to the broader orthopedic and health care community.²²

We conducted a study to investigate current trends in CMC interposition arthroplasty across time, sex, age, and region of the United States; per-patient charges and reimbursements; and the association between this procedure and concomitantly performed carpal tunnel syndrome (CTS) and carpal tunnel release (CTR). In addition, we compared incidence of CMC interposition arthroplasty with that of CMC arthrodesis.

Patients and Methods

All data were derived from the PearlDiver Patient Records Database (PearlDiver Technologies), a publicly available database of patients. The database stores procedure volumes, demographics, and average charge information for patients with International Classification of Diseases, Ninth Revision (ICD-9) diagnoses and procedures or Current Procedural Terminology (CPT) codes. Data for the present study were drawn from the Medicare database within the PearlDiver records, which has a total of 179,094,296 patient records covering the period 2005–2011. This study did not require institutional review board approval, as it used existing, publicly available data without identifiers linked to subjects.

PearlDiver Technologies granted us database access for academic research. The database was stored on a password-protected server maintained by PearlDiver. ICD-9 and CPT codes can be searched in isolation or in combination. Search results yield number of patients with a searched code (or combination of codes) in each year, age group, or region of the United States, as well as mean charge and mean reimbursement for the code or combination of codes.

We used CPT code 25447 (arthroplasty, interposition, intercarpal, or CMC joints) to search the database for patients who underwent thumb CMC interposition arthroplasty. Although this code does not specify thumb, we are unaware of any procedure (other than thumb CMC interposition arthroplasty) typically given this code. Our search yielded procedure volumes, sex distribution, age distribution, region volumes, and mean per-patient charges and reimbursements for each CPT code. We then searched the resulting cohort for CTS (ICD-9 code 354.0), endoscopic CTR (CPT code 29848), and open CTR (CPT code 64721) to find CTR performed concomitantly with CMC interposition arthroplasty. Last, patients were tracked in the database past their surgery date to evaluate for postoperative physical or occupational therapy evaluations within 6 months (using CPT codes appearing in at least 1% of the cohort: 97001, 97003, 97004, 97110, 97112, 97124, 97140, 97150, 97350, 97535) and postoperative thumb, hand, or wrist radiographs within 6 months (using CPT codes appearing in at least 1% of the cohort: 73140, 73130, 73110). To ensure adequacy of 6-month postoperative data, we included in this portion of the study only those patients with surgery dates between 2005 and 2010.

For comparative purposes, we also searched the database for patients who underwent thumb CMC arthrodesis within the same period—using CPT codes 26841 and 26842 (arthrodesis CMC joint thumb, with or without internal fixation; with or without autograft) and CPT code 26820 (fusion in opposition, thumb, with autogenous graft).

Overall procedure volume data are reported as number of patients with the given CPT code in the database output in a given year. Age-group and sex analyses are reported as number of patients reported in the database output and as percentage of patients who underwent the CPT code of interest that year. Mean charges and reimbursements are reported as results by the database for the code of interest (CPT 25447). Data for the region analysis are presented as an incidence, as there is an uneven distribution of patient volumes among regions. This incidence is calculated as number of patients in a particular region and year normalized to total number of patients in the database for that particular region or year. Regions are defined as Midwest (IA, IL, IN, KS, MI, MN, MO, ND, NE, OH, SD, WI), Northeast (CT, MA, ME, NH, NJ, NY, PA, RI, VT), South (AL, AR, DC, DE, FL, GA, KY, LA, MD, MS, NC, OK, SC, TN, TX, VA, WV), and West (AK, AZ, CA, CO, HI, ID, MT, NM, NV, OR, UT, WA, WY).

Chi-squared linear-by-linear association analysis was used to determine statistical significance with regard to trends over time in procedure volumes, sex, age group, and region. For all statistical comparisons, P < .05 was considered significant.

Results

In the database, we identified 41,171 unique patients who underwent CMC interposition arthroplasty between 2005 and 2011. Over the 7-year study period, number of patients who had CMC interposition arthroplasty increased 46.2%, from 4761 in 2005 to 6960 in 2011 (P < .0001) (Table 1, Figure 1). Throughout this period, females underwent CMC interposition arthroplasty more frequently than males at all time points (P < .0001). Overall ratio of female to male patients, however, changed significantly. In 2005, 18.1% of all CMC interposition arthroplasties were performed on male patients; this increased to 23.9% of all procedures by 2011 (P < .0001) (Figure 2). Table 1 presents an age-group analysis. There were no significant differences in relative percentage of patients in any given age group who underwent CMC interposition arthroplasty over the study period.

Analysis of overall procedure incidence by region revealed significant increases in all regions (P < .0001), ranging from 18.5% (West) to 54.5% (Northeast) (Figure 3). At all time points, the incidence of CMC interposition arthroplasty was significantly lower in the Northeast than in any other region and compared with the overall average.

Between 2005 and 2011, there were significant increases in both per-patient charges and reimbursements for CMC interposition arthroplasty (Figure 4). Mean per-patient charge increased from $2676 in 2005 to $4181 in 2011 (P < .0001), and mean per-patient reimbursement increased from $1445 in 2005 to $2061 in 2011 (P < .0001). The discrepancy between charge and reimbursement increased throughout the study period: Reimbursement in 2005 was 54.0% of the charge; this decreased to 49.3% by 2011 but was not statistically significant (P = .08).

Overall, 40.9% of patients who underwent CMC interposition arthroplasty also had a CTS diagnosis. Between 15.5% and 17.3% of these patients had concomitant open or endoscopic CTR at time of CMC interposition arthroplasty (Table 2). Percentage of patients who underwent concomitant CTR did not change significantly from 2005 to 2011 (P = .139). Use of postoperative occupational and/or physical therapy increased significantly over the study period, from 33.5% of patients in 2005 to 50.7% of patients in 2010 (P < .0001). Use of postoperative thumb, hand, and/or wrist radiography also increased throughout the study period, from 7.4% of patients in 2005 to 18.7% of patients in 2010 (P < .0001).

We identified 1916 unique patients who underwent thumb CMC arthrodesis between 2005 and 2011. Over the 7-year study period, there was a 19.1% decrease in number of patients who underwent CMC arthrodesis, from 309 in 2005 to 250 in 2011 (P < .0001) (Figure 5). Significantly fewer patients had CMC arthrodesis compared with CMC interposition arthroplasty at all time points, ranging from 6.5% (thumb CMC arthrodesis:CMC interposition arthroplasty) in 2005 to 3.6% in 2011 (P < .0001).

Discussion

Our results demonstrated a significant increase in use of thumb CMC interposition arthroplasty in a US Medicare population, with an increase of more than 46% from 2005 to 2011. This finding supports the findings of a recent cross-sectional survey-based study in which 719 (62%) of 1156 surveyed US hand surgeons reported performing trapeziectomy with LRTI for advanced thumb CMC-OA.²¹ A prior study had similar findings, with 692 (68%) of 1024 American Society for Surgery of the Hand (ASSH) members performing LRTI and 766 (75%) of 1024 performing some type of CMC interposition with trapeziectomy for advanced CMC-OA.²³ This preference for CMC interposition arthroplasty prevails despite the fact that numerous studies have shown no superiority of any surgical procedure to another for CMC-OA in terms of pain, function, satisfaction, range of motion, and strength.^{7,15,18,19,24-34} Our data demonstrated that, not only does CMC interposition arthroplasty remain the most frequently used procedure for thumb CMC-OA, the incidence of CMC interposition arthroplasty continues to increase yearly.

The incidence of thumb CMC-OA is higher in women than in men, with more joint laxity a known contributor and subtle sex differences in trapezium geometry and congruence postulated as additional factors.^3,35,36 This trend was confirmed in the present study, as females underwent significantly more CMC interposition arthroplasties at all time points. It is interesting that the overall ratio of female to male patients changed significantly over the study period, with the percentage of patients who were male increasing from 18.1% in 2005 to 23.9% in 2011. No previous studies have captured such a large cross section of the population to establish this trend. Although this trend is not necessarily intuitive, potential theories include increased acceptance of CMC interposition arthroplasty as a surgical option for male patients, and potentially a larger number of male patients seeking medical care for thumb CMC-OA in recent years.

Increases in procedure incidence were noted in all regions of the United States, but the largest percentage increase occurred in the Northeast. Despite this increase, the Northeast also had significantly lower CMC interposition arthroplasty incidence compared with all other regions and with the average procedure incidence throughout the study period—demonstrating some regional bias as to treatment of thumb CMC-OA. Unfortunately, because of database limitations and lack of specific CPT codes for other treatment options for thumb CMC-OA, we cannot ascertain if other types of surgery are more frequently used in the Northeast.

CTS and thumb CMC-OA often coexist.³⁷ The estimated incidence of concomitant CTS in patients with CMC-OA is between 4% and 43%, but the rate of concomitant CTR and CMC interposition arthroplasty was not previously characterized in the literature.^38,39 Results of the present study supported these findings; 41% of patients who underwent CMC interposition arthroplasty in our study also had a CTS diagnosis, compared with 43% in the 246-patient study by Florack and colleagues.³⁸ We also found that 16% to 17% of patients who underwent CMC interposition arthroplasty underwent concomitant CTR; this rate remained consistent throughout the study period.

Our study demonstrated that, compared with CMC interposition arthroplasties, significantly fewer thumb CMC arthrodesis procedures were performed in the same Medicare population during the same period. Furthermore, the number of thumb CMC arthrodesis procedures declined yearly, with an overall decrease of 19% from 2005 to 2011. In a recent single-blinded, randomized trial, Vermeulen and colleagues⁴⁰ compared thumb CMC arthrodesis and trapeziectomy with LRTI. They found superior patient satisfaction and significantly lower complication rates in women who underwent LRTI versus arthrodesis. The study was terminated prematurely because of these complications and thus was underpowered to determine differences in specific outcome measures. Previous studies comparing arthrodesis and interposition arthroplasties reported inconsistent outcomes. Hart and colleagues⁴¹ found no significant differences in pain or function between CMC arthrodesis and LRTI at a mean 7-year follow-up in a level II randomized controlled trial. Hartigan and colleagues¹⁵ reached similar conclusions in their retrospective comparison of the procedures. Without clear evidence supporting arthrodesis over interposition arthroplasty, the majority of surgeons favor interposition arthroplasty for thumb CMC-OA. Among Medicare patients, use of thumb CMC arthrodesis continues to fall.

This national database study had several limitations, which are common to all studies using the PearlDiver database^22,42-47:

1. The power of the analysis depended on the quality of available data. Potential sources of error included accuracy of billing codes, and miscoding or noncoding by physicians.⁴⁶

2. Although we used this database to try to accurately represent a large population of interest, we cannot guarantee the database represented a true cross section of the United States.

3. For the Medicare population, the PearlDiver database indexes data only in 7-year increments. Although the study period was long enough to detect significant trends, some data may not be accurately captured over a 7-year period.

4. Patients were not randomized to a treatment group.

5. The PearlDiver database does not include any clinical outcome data. Therefore, we cannot comment on the efficacy of the reported evaluations and interventions.

6. There is no specific CPT code for thumb CMC interposition arthroplasty. However, we are unaware of a CMC interposition arthroplasty performed for any area besides the thumb. Theoretically, the study population can include a negligible percentage of patients who had interposition arthroplasty of a CMC joint other than the thumb.

7. The database cannot be searched for use of thumb CMC-OA surgical techniques other than CMC interposition arthroplasty or arthrodesis, as isolated trapeziectomy, volar ligament reconstruction, implant arthroplasty, and metacarpal osteotomy lack specific CPT codes.

Conclusion

Thumb CMC-OA is a common entity among Medicare patients. There are numerous surgical options for cases that have failed conservative treatment. Despite the lack of evidence that thumb CMC interposition arthroplasty is superior to other surgical options, the number of patients who had this procedure increased 46% during the 2005–2011 study period. Although the majority of patients who undergo CMC interposition arthroplasty are female, the percentage of male patients has increased significantly. More than 40% of patients who have CMC interposition arthroplasty are also diagnosed with CTS, and 16% to 17% of patients who have CMC interposition arthroplasty will have a concomitant CTR. CMC arthrodesis is used in significantly fewer patients of Medicare age, and its use has been declining.

A common entity, osteoarthritis (OA) at the base of the thumb is largely caused by the unique anatomy and biomechanics of the thumb carpometacarpal (CMC) joint.¹ Radiographically evident CMC degeneration occurs in 40% of women and 25% of men over age 75 years, making the thumb CMC joint the most common site of surgical reconstruction for upper extremity OA.^2,3

Over the past 40 years, numerous surgical techniques for managing thumb CMC-OA have been described. These include volar ligament reconstruction, first metacarpal osteotomy, CMC arthrodesis, CMC joint replacement, and trapeziectomy. Trapeziectomy can be performed in isolation or in combination with tendon interposition, ligament reconstruction, or ligament reconstruction and tendon interposition (LRTI).^4-20 The authors of a recent systematic review concluded there is no evidence that any one surgical procedure for CMC-OA is superior to another in terms of pain, function, satisfaction, range of motion, or strength.⁴ Nevertheless, a recent survey found that 719 (62%) of 1156 US hand surgeons used LRTI as the treatment of choice for advanced CMC-OA.²¹

Our detailed literature search yielded no other database studies characterizing current trends in the practice patterns of US orthopedic surgeons who perform interposition arthroplasty for CMC arthritis. Analysis of these trends is important not only to patients but also to the broader orthopedic and health care community.²²

We conducted a study to investigate current trends in CMC interposition arthroplasty across time, sex, age, and region of the United States; per-patient charges and reimbursements; and the association between this procedure and concomitantly performed carpal tunnel syndrome (CTS) and carpal tunnel release (CTR). In addition, we compared incidence of CMC interposition arthroplasty with that of CMC arthrodesis.

Patients and Methods

All data were derived from the PearlDiver Patient Records Database (PearlDiver Technologies), a publicly available database of patients. The database stores procedure volumes, demographics, and average charge information for patients with International Classification of Diseases, Ninth Revision (ICD-9) diagnoses and procedures or Current Procedural Terminology (CPT) codes. Data for the present study were drawn from the Medicare database within the PearlDiver records, which has a total of 179,094,296 patient records covering the period 2005–2011. This study did not require institutional review board approval, as it used existing, publicly available data without identifiers linked to subjects.

PearlDiver Technologies granted us database access for academic research. The database was stored on a password-protected server maintained by PearlDiver. ICD-9 and CPT codes can be searched in isolation or in combination. Search results yield number of patients with a searched code (or combination of codes) in each year, age group, or region of the United States, as well as mean charge and mean reimbursement for the code or combination of codes.

We used CPT code 25447 (arthroplasty, interposition, intercarpal, or CMC joints) to search the database for patients who underwent thumb CMC interposition arthroplasty. Although this code does not specify thumb, we are unaware of any procedure (other than thumb CMC interposition arthroplasty) typically given this code. Our search yielded procedure volumes, sex distribution, age distribution, region volumes, and mean per-patient charges and reimbursements for each CPT code. We then searched the resulting cohort for CTS (ICD-9 code 354.0), endoscopic CTR (CPT code 29848), and open CTR (CPT code 64721) to find CTR performed concomitantly with CMC interposition arthroplasty. Last, patients were tracked in the database past their surgery date to evaluate for postoperative physical or occupational therapy evaluations within 6 months (using CPT codes appearing in at least 1% of the cohort: 97001, 97003, 97004, 97110, 97112, 97124, 97140, 97150, 97350, 97535) and postoperative thumb, hand, or wrist radiographs within 6 months (using CPT codes appearing in at least 1% of the cohort: 73140, 73130, 73110). To ensure adequacy of 6-month postoperative data, we included in this portion of the study only those patients with surgery dates between 2005 and 2010.

For comparative purposes, we also searched the database for patients who underwent thumb CMC arthrodesis within the same period—using CPT codes 26841 and 26842 (arthrodesis CMC joint thumb, with or without internal fixation; with or without autograft) and CPT code 26820 (fusion in opposition, thumb, with autogenous graft).

Overall procedure volume data are reported as number of patients with the given CPT code in the database output in a given year. Age-group and sex analyses are reported as number of patients reported in the database output and as percentage of patients who underwent the CPT code of interest that year. Mean charges and reimbursements are reported as results by the database for the code of interest (CPT 25447). Data for the region analysis are presented as an incidence, as there is an uneven distribution of patient volumes among regions. This incidence is calculated as number of patients in a particular region and year normalized to total number of patients in the database for that particular region or year. Regions are defined as Midwest (IA, IL, IN, KS, MI, MN, MO, ND, NE, OH, SD, WI), Northeast (CT, MA, ME, NH, NJ, NY, PA, RI, VT), South (AL, AR, DC, DE, FL, GA, KY, LA, MD, MS, NC, OK, SC, TN, TX, VA, WV), and West (AK, AZ, CA, CO, HI, ID, MT, NM, NV, OR, UT, WA, WY).

Chi-squared linear-by-linear association analysis was used to determine statistical significance with regard to trends over time in procedure volumes, sex, age group, and region. For all statistical comparisons, P < .05 was considered significant.

Results

In the database, we identified 41,171 unique patients who underwent CMC interposition arthroplasty between 2005 and 2011. Over the 7-year study period, number of patients who had CMC interposition arthroplasty increased 46.2%, from 4761 in 2005 to 6960 in 2011 (P < .0001) (Table 1, Figure 1). Throughout this period, females underwent CMC interposition arthroplasty more frequently than males at all time points (P < .0001). Overall ratio of female to male patients, however, changed significantly. In 2005, 18.1% of all CMC interposition arthroplasties were performed on male patients; this increased to 23.9% of all procedures by 2011 (P < .0001) (Figure 2). Table 1 presents an age-group analysis. There were no significant differences in relative percentage of patients in any given age group who underwent CMC interposition arthroplasty over the study period.

Analysis of overall procedure incidence by region revealed significant increases in all regions (P < .0001), ranging from 18.5% (West) to 54.5% (Northeast) (Figure 3). At all time points, the incidence of CMC interposition arthroplasty was significantly lower in the Northeast than in any other region and compared with the overall average.

Between 2005 and 2011, there were significant increases in both per-patient charges and reimbursements for CMC interposition arthroplasty (Figure 4). Mean per-patient charge increased from $2676 in 2005 to $4181 in 2011 (P < .0001), and mean per-patient reimbursement increased from $1445 in 2005 to $2061 in 2011 (P < .0001). The discrepancy between charge and reimbursement increased throughout the study period: Reimbursement in 2005 was 54.0% of the charge; this decreased to 49.3% by 2011 but was not statistically significant (P = .08).

Overall, 40.9% of patients who underwent CMC interposition arthroplasty also had a CTS diagnosis. Between 15.5% and 17.3% of these patients had concomitant open or endoscopic CTR at time of CMC interposition arthroplasty (Table 2). Percentage of patients who underwent concomitant CTR did not change significantly from 2005 to 2011 (P = .139). Use of postoperative occupational and/or physical therapy increased significantly over the study period, from 33.5% of patients in 2005 to 50.7% of patients in 2010 (P < .0001). Use of postoperative thumb, hand, and/or wrist radiography also increased throughout the study period, from 7.4% of patients in 2005 to 18.7% of patients in 2010 (P < .0001).

We identified 1916 unique patients who underwent thumb CMC arthrodesis between 2005 and 2011. Over the 7-year study period, there was a 19.1% decrease in number of patients who underwent CMC arthrodesis, from 309 in 2005 to 250 in 2011 (P < .0001) (Figure 5). Significantly fewer patients had CMC arthrodesis compared with CMC interposition arthroplasty at all time points, ranging from 6.5% (thumb CMC arthrodesis:CMC interposition arthroplasty) in 2005 to 3.6% in 2011 (P < .0001).

Discussion

Our results demonstrated a significant increase in use of thumb CMC interposition arthroplasty in a US Medicare population, with an increase of more than 46% from 2005 to 2011. This finding supports the findings of a recent cross-sectional survey-based study in which 719 (62%) of 1156 surveyed US hand surgeons reported performing trapeziectomy with LRTI for advanced thumb CMC-OA.²¹ A prior study had similar findings, with 692 (68%) of 1024 American Society for Surgery of the Hand (ASSH) members performing LRTI and 766 (75%) of 1024 performing some type of CMC interposition with trapeziectomy for advanced CMC-OA.²³ This preference for CMC interposition arthroplasty prevails despite the fact that numerous studies have shown no superiority of any surgical procedure to another for CMC-OA in terms of pain, function, satisfaction, range of motion, and strength.^{7,15,18,19,24-34} Our data demonstrated that, not only does CMC interposition arthroplasty remain the most frequently used procedure for thumb CMC-OA, the incidence of CMC interposition arthroplasty continues to increase yearly.

The incidence of thumb CMC-OA is higher in women than in men, with more joint laxity a known contributor and subtle sex differences in trapezium geometry and congruence postulated as additional factors.^3,35,36 This trend was confirmed in the present study, as females underwent significantly more CMC interposition arthroplasties at all time points. It is interesting that the overall ratio of female to male patients changed significantly over the study period, with the percentage of patients who were male increasing from 18.1% in 2005 to 23.9% in 2011. No previous studies have captured such a large cross section of the population to establish this trend. Although this trend is not necessarily intuitive, potential theories include increased acceptance of CMC interposition arthroplasty as a surgical option for male patients, and potentially a larger number of male patients seeking medical care for thumb CMC-OA in recent years.

Increases in procedure incidence were noted in all regions of the United States, but the largest percentage increase occurred in the Northeast. Despite this increase, the Northeast also had significantly lower CMC interposition arthroplasty incidence compared with all other regions and with the average procedure incidence throughout the study period—demonstrating some regional bias as to treatment of thumb CMC-OA. Unfortunately, because of database limitations and lack of specific CPT codes for other treatment options for thumb CMC-OA, we cannot ascertain if other types of surgery are more frequently used in the Northeast.

CTS and thumb CMC-OA often coexist.³⁷ The estimated incidence of concomitant CTS in patients with CMC-OA is between 4% and 43%, but the rate of concomitant CTR and CMC interposition arthroplasty was not previously characterized in the literature.^38,39 Results of the present study supported these findings; 41% of patients who underwent CMC interposition arthroplasty in our study also had a CTS diagnosis, compared with 43% in the 246-patient study by Florack and colleagues.³⁸ We also found that 16% to 17% of patients who underwent CMC interposition arthroplasty underwent concomitant CTR; this rate remained consistent throughout the study period.

Our study demonstrated that, compared with CMC interposition arthroplasties, significantly fewer thumb CMC arthrodesis procedures were performed in the same Medicare population during the same period. Furthermore, the number of thumb CMC arthrodesis procedures declined yearly, with an overall decrease of 19% from 2005 to 2011. In a recent single-blinded, randomized trial, Vermeulen and colleagues⁴⁰ compared thumb CMC arthrodesis and trapeziectomy with LRTI. They found superior patient satisfaction and significantly lower complication rates in women who underwent LRTI versus arthrodesis. The study was terminated prematurely because of these complications and thus was underpowered to determine differences in specific outcome measures. Previous studies comparing arthrodesis and interposition arthroplasties reported inconsistent outcomes. Hart and colleagues⁴¹ found no significant differences in pain or function between CMC arthrodesis and LRTI at a mean 7-year follow-up in a level II randomized controlled trial. Hartigan and colleagues¹⁵ reached similar conclusions in their retrospective comparison of the procedures. Without clear evidence supporting arthrodesis over interposition arthroplasty, the majority of surgeons favor interposition arthroplasty for thumb CMC-OA. Among Medicare patients, use of thumb CMC arthrodesis continues to fall.

This national database study had several limitations, which are common to all studies using the PearlDiver database^22,42-47:

1. The power of the analysis depended on the quality of available data. Potential sources of error included accuracy of billing codes, and miscoding or noncoding by physicians.⁴⁶

2. Although we used this database to try to accurately represent a large population of interest, we cannot guarantee the database represented a true cross section of the United States.

3. For the Medicare population, the PearlDiver database indexes data only in 7-year increments. Although the study period was long enough to detect significant trends, some data may not be accurately captured over a 7-year period.

4. Patients were not randomized to a treatment group.

5. The PearlDiver database does not include any clinical outcome data. Therefore, we cannot comment on the efficacy of the reported evaluations and interventions.

6. There is no specific CPT code for thumb CMC interposition arthroplasty. However, we are unaware of a CMC interposition arthroplasty performed for any area besides the thumb. Theoretically, the study population can include a negligible percentage of patients who had interposition arthroplasty of a CMC joint other than the thumb.

7. The database cannot be searched for use of thumb CMC-OA surgical techniques other than CMC interposition arthroplasty or arthrodesis, as isolated trapeziectomy, volar ligament reconstruction, implant arthroplasty, and metacarpal osteotomy lack specific CPT codes.

Conclusion

Thumb CMC-OA is a common entity among Medicare patients. There are numerous surgical options for cases that have failed conservative treatment. Despite the lack of evidence that thumb CMC interposition arthroplasty is superior to other surgical options, the number of patients who had this procedure increased 46% during the 2005–2011 study period. Although the majority of patients who undergo CMC interposition arthroplasty are female, the percentage of male patients has increased significantly. More than 40% of patients who have CMC interposition arthroplasty are also diagnosed with CTS, and 16% to 17% of patients who have CMC interposition arthroplasty will have a concomitant CTR. CMC arthrodesis is used in significantly fewer patients of Medicare age, and its use has been declining.

Extensor tendon rupture in chronic Madelung deformity, as a result of tendon attrition on the dislocated distal ulna, occurs infrequently. However, it is often seen in patients with rheumatoid arthritis. This issue has been reported in only a few English-language case reports. Here we report a case of multiple tendon ruptures in a previously undiagnosed Madelung deformity. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 56-year-old active woman presented with 50 days’ inability to extend the fourth and fifth fingers of her dominant right hand. The loss of finger extension progressed, over several weeks, to involve the third finger as well. The first 2 tendon ruptures had been triggered by lifting a light grocery bag, when she noticed a sharp sudden pain and “pop.” The third rupture occurred spontaneously with a snapping sound the night before surgery.

 The patient had observed some prominence on the ulnar side of her right wrist since childhood but had never experienced any pain or functional disability. There was neither history of trauma, inflammatory disease, diabetes mellitus, or infection, nor positive family history of similar wrist deformity.

The physical examination showed a dorsally subluxated distal radioulnar joint, prominent ulnar styloid, and mild ulnar and volar deviation of the wrist along with limitation of wrist dorsiflexion. Complete loss of active extension of the 3 ulnar fingers was demonstrated, while neurovascular status and all other hand evaluations were normal. The wrist radiographs confirmed the typical findings of Madelung deformity (Figure 1).

Repair of the ruptured tendons and resection of the prominent distal ulna (Darrach procedure) was planned. (Given the patient’s age and evidence of degenerative changes in the radiocarpal joint, correction of the Madelung deformity did not seem necessary). At time of surgery, the recently ruptured third finger extensor tendon was easily found and approximated, and end-to-end repair was performed. The fourth and fifth fingers, however, had to be fished out more proximally from dense granulation tissue. After the distal ulna was resected for a distance of 1.5 cm, meticulous repair of the ulnar collateral ligament and the capsule and periosteum over the end of the ulna was performed. Then, for grafting of the ruptured tendons, the extensor indicis proprius tendon was isolated and transected at the second metacarpophalangeal joint level. A piece of this tendon was used as interpositional graft for the fourth extensor tendon, and the main tendon unit was transferred to the fifth finger extensor. The extensor digiti quinti tendon, which was about to rupture, was further reinforced by suturing it side to side to the muscle and tendon of the extensor indicis proprius (Figure 2).

Postoperatively, the wrist was kept in extension in a cast for 3 weeks while the fingers were free for active movement. A removable wrist splint was used for an additional month. At 3-month follow-up, the patient had regained full and strong finger extension and wrist motion.

At 3-year follow-up, the patient was pain-free, and had full extension of all fingers, full forearm rotation, and near-normal motion (better than her preoperative motion). The grip power on the operated right hand was 215 N, and pinch power was 93 N. (The values for the left side were 254 N and 83 N, respectively, using the Jamar hydraulic hand dynamometer [Patterson Medical].) The patient has had no additional tendon rupture (Figure 3).

Discussion

Madelung deformity was first described by Madelung in 1878 and several cases have reported this deformity. However, extensor tendon rupture caused by Madelung deformity is very rare, reported in few cases.¹

Extensor tendon rupture caused by chronic Madelung deformity has been reported few times in the English literature. Goodwin¹ apparently published the first report of such an occurrence in 1979. Ducloyer and colleagues² from France reported 6 cases of extensor tendon rupture as a result of inferior distal radioulnar joint deformity of Madelung. Jebson and colleagues³ reported bilateral spontaneous extensor tendon ruptures in Madelung deformity in 1992.

The mechanism of tendon rupture seems to be mechanical, resulting from continuous rubbing and erosion of tendons over the deformed ulnar head, which has a rough irregular surface⁴ and leads to fraying of the tendons and eventual rupture and retraction of the severed tendon ends. This rupture usually progresses stepwise from more medial to the lateral tendons.² Older patients are, therefore, subject to chronic repetitive attritional trauma leading to tendon rupture.

Tendons may rupture as a result of a variety of conditions, such as chronic synovitis in rheumatoid arthritis, systemic lupus erythematosus, mixed connective tissue disease, or crystal deposition in gout.^5-8 Some other metabolic or endocrine conditions that involve tendon ruptures include diabetes mellitus, chronic renal failure, and hyperparathyroidism. Steroid injection into the tendons also has a detrimental effect on tendon integrity and may cause tendon tear.⁹ Mechanical factors, such as erosion on bony prominences, are well-known etiologies for tendon rupture, as commonly seen in rheumatoid arthritis, and have been reported in Kienböck disease,¹⁰ thumb carpometacarpal arthritis,¹¹ Colles fracture, scaphoid fracture nonunion,¹² and Madelung deformity.

Conclusion

Our case reflects the usual middle-aged female presentation of such a tendon rupture. The tendon ruptures were spontaneous in the reported order of ulnar to radial, beginning with the little and ring fingers, and progressed radially. The patient had isolated Madelung deformity with no other sign of dyschondrosteosis¹³ or dwarfism, conditions commonly mentioned in association with Madelung deformity. This case report should raise awareness about possible tendon rupture in any chronic case of Madelung deformity.

Extensor tendon rupture in chronic Madelung deformity, as a result of tendon attrition on the dislocated distal ulna, occurs infrequently. However, it is often seen in patients with rheumatoid arthritis. This issue has been reported in only a few English-language case reports. Here we report a case of multiple tendon ruptures in a previously undiagnosed Madelung deformity. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 56-year-old active woman presented with 50 days’ inability to extend the fourth and fifth fingers of her dominant right hand. The loss of finger extension progressed, over several weeks, to involve the third finger as well. The first 2 tendon ruptures had been triggered by lifting a light grocery bag, when she noticed a sharp sudden pain and “pop.” The third rupture occurred spontaneously with a snapping sound the night before surgery.

 The patient had observed some prominence on the ulnar side of her right wrist since childhood but had never experienced any pain or functional disability. There was neither history of trauma, inflammatory disease, diabetes mellitus, or infection, nor positive family history of similar wrist deformity.

The physical examination showed a dorsally subluxated distal radioulnar joint, prominent ulnar styloid, and mild ulnar and volar deviation of the wrist along with limitation of wrist dorsiflexion. Complete loss of active extension of the 3 ulnar fingers was demonstrated, while neurovascular status and all other hand evaluations were normal. The wrist radiographs confirmed the typical findings of Madelung deformity (Figure 1).

Repair of the ruptured tendons and resection of the prominent distal ulna (Darrach procedure) was planned. (Given the patient’s age and evidence of degenerative changes in the radiocarpal joint, correction of the Madelung deformity did not seem necessary). At time of surgery, the recently ruptured third finger extensor tendon was easily found and approximated, and end-to-end repair was performed. The fourth and fifth fingers, however, had to be fished out more proximally from dense granulation tissue. After the distal ulna was resected for a distance of 1.5 cm, meticulous repair of the ulnar collateral ligament and the capsule and periosteum over the end of the ulna was performed. Then, for grafting of the ruptured tendons, the extensor indicis proprius tendon was isolated and transected at the second metacarpophalangeal joint level. A piece of this tendon was used as interpositional graft for the fourth extensor tendon, and the main tendon unit was transferred to the fifth finger extensor. The extensor digiti quinti tendon, which was about to rupture, was further reinforced by suturing it side to side to the muscle and tendon of the extensor indicis proprius (Figure 2).

Postoperatively, the wrist was kept in extension in a cast for 3 weeks while the fingers were free for active movement. A removable wrist splint was used for an additional month. At 3-month follow-up, the patient had regained full and strong finger extension and wrist motion.

At 3-year follow-up, the patient was pain-free, and had full extension of all fingers, full forearm rotation, and near-normal motion (better than her preoperative motion). The grip power on the operated right hand was 215 N, and pinch power was 93 N. (The values for the left side were 254 N and 83 N, respectively, using the Jamar hydraulic hand dynamometer [Patterson Medical].) The patient has had no additional tendon rupture (Figure 3).

Discussion

Madelung deformity was first described by Madelung in 1878 and several cases have reported this deformity. However, extensor tendon rupture caused by Madelung deformity is very rare, reported in few cases.¹

Extensor tendon rupture caused by chronic Madelung deformity has been reported few times in the English literature. Goodwin¹ apparently published the first report of such an occurrence in 1979. Ducloyer and colleagues² from France reported 6 cases of extensor tendon rupture as a result of inferior distal radioulnar joint deformity of Madelung. Jebson and colleagues³ reported bilateral spontaneous extensor tendon ruptures in Madelung deformity in 1992.

The mechanism of tendon rupture seems to be mechanical, resulting from continuous rubbing and erosion of tendons over the deformed ulnar head, which has a rough irregular surface⁴ and leads to fraying of the tendons and eventual rupture and retraction of the severed tendon ends. This rupture usually progresses stepwise from more medial to the lateral tendons.² Older patients are, therefore, subject to chronic repetitive attritional trauma leading to tendon rupture.

Tendons may rupture as a result of a variety of conditions, such as chronic synovitis in rheumatoid arthritis, systemic lupus erythematosus, mixed connective tissue disease, or crystal deposition in gout.^5-8 Some other metabolic or endocrine conditions that involve tendon ruptures include diabetes mellitus, chronic renal failure, and hyperparathyroidism. Steroid injection into the tendons also has a detrimental effect on tendon integrity and may cause tendon tear.⁹ Mechanical factors, such as erosion on bony prominences, are well-known etiologies for tendon rupture, as commonly seen in rheumatoid arthritis, and have been reported in Kienböck disease,¹⁰ thumb carpometacarpal arthritis,¹¹ Colles fracture, scaphoid fracture nonunion,¹² and Madelung deformity.

Conclusion

Our case reflects the usual middle-aged female presentation of such a tendon rupture. The tendon ruptures were spontaneous in the reported order of ulnar to radial, beginning with the little and ring fingers, and progressed radially. The patient had isolated Madelung deformity with no other sign of dyschondrosteosis¹³ or dwarfism, conditions commonly mentioned in association with Madelung deformity. This case report should raise awareness about possible tendon rupture in any chronic case of Madelung deformity.

Extensor tendon rupture in chronic Madelung deformity, as a result of tendon attrition on the dislocated distal ulna, occurs infrequently. However, it is often seen in patients with rheumatoid arthritis. This issue has been reported in only a few English-language case reports. Here we report a case of multiple tendon ruptures in a previously undiagnosed Madelung deformity. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 56-year-old active woman presented with 50 days’ inability to extend the fourth and fifth fingers of her dominant right hand. The loss of finger extension progressed, over several weeks, to involve the third finger as well. The first 2 tendon ruptures had been triggered by lifting a light grocery bag, when she noticed a sharp sudden pain and “pop.” The third rupture occurred spontaneously with a snapping sound the night before surgery.

 The patient had observed some prominence on the ulnar side of her right wrist since childhood but had never experienced any pain or functional disability. There was neither history of trauma, inflammatory disease, diabetes mellitus, or infection, nor positive family history of similar wrist deformity.

The physical examination showed a dorsally subluxated distal radioulnar joint, prominent ulnar styloid, and mild ulnar and volar deviation of the wrist along with limitation of wrist dorsiflexion. Complete loss of active extension of the 3 ulnar fingers was demonstrated, while neurovascular status and all other hand evaluations were normal. The wrist radiographs confirmed the typical findings of Madelung deformity (Figure 1).

Repair of the ruptured tendons and resection of the prominent distal ulna (Darrach procedure) was planned. (Given the patient’s age and evidence of degenerative changes in the radiocarpal joint, correction of the Madelung deformity did not seem necessary). At time of surgery, the recently ruptured third finger extensor tendon was easily found and approximated, and end-to-end repair was performed. The fourth and fifth fingers, however, had to be fished out more proximally from dense granulation tissue. After the distal ulna was resected for a distance of 1.5 cm, meticulous repair of the ulnar collateral ligament and the capsule and periosteum over the end of the ulna was performed. Then, for grafting of the ruptured tendons, the extensor indicis proprius tendon was isolated and transected at the second metacarpophalangeal joint level. A piece of this tendon was used as interpositional graft for the fourth extensor tendon, and the main tendon unit was transferred to the fifth finger extensor. The extensor digiti quinti tendon, which was about to rupture, was further reinforced by suturing it side to side to the muscle and tendon of the extensor indicis proprius (Figure 2).

Postoperatively, the wrist was kept in extension in a cast for 3 weeks while the fingers were free for active movement. A removable wrist splint was used for an additional month. At 3-month follow-up, the patient had regained full and strong finger extension and wrist motion.

At 3-year follow-up, the patient was pain-free, and had full extension of all fingers, full forearm rotation, and near-normal motion (better than her preoperative motion). The grip power on the operated right hand was 215 N, and pinch power was 93 N. (The values for the left side were 254 N and 83 N, respectively, using the Jamar hydraulic hand dynamometer [Patterson Medical].) The patient has had no additional tendon rupture (Figure 3).

Discussion

Madelung deformity was first described by Madelung in 1878 and several cases have reported this deformity. However, extensor tendon rupture caused by Madelung deformity is very rare, reported in few cases.¹

Extensor tendon rupture caused by chronic Madelung deformity has been reported few times in the English literature. Goodwin¹ apparently published the first report of such an occurrence in 1979. Ducloyer and colleagues² from France reported 6 cases of extensor tendon rupture as a result of inferior distal radioulnar joint deformity of Madelung. Jebson and colleagues³ reported bilateral spontaneous extensor tendon ruptures in Madelung deformity in 1992.

The mechanism of tendon rupture seems to be mechanical, resulting from continuous rubbing and erosion of tendons over the deformed ulnar head, which has a rough irregular surface⁴ and leads to fraying of the tendons and eventual rupture and retraction of the severed tendon ends. This rupture usually progresses stepwise from more medial to the lateral tendons.² Older patients are, therefore, subject to chronic repetitive attritional trauma leading to tendon rupture.

Tendons may rupture as a result of a variety of conditions, such as chronic synovitis in rheumatoid arthritis, systemic lupus erythematosus, mixed connective tissue disease, or crystal deposition in gout.^5-8 Some other metabolic or endocrine conditions that involve tendon ruptures include diabetes mellitus, chronic renal failure, and hyperparathyroidism. Steroid injection into the tendons also has a detrimental effect on tendon integrity and may cause tendon tear.⁹ Mechanical factors, such as erosion on bony prominences, are well-known etiologies for tendon rupture, as commonly seen in rheumatoid arthritis, and have been reported in Kienböck disease,¹⁰ thumb carpometacarpal arthritis,¹¹ Colles fracture, scaphoid fracture nonunion,¹² and Madelung deformity.

Conclusion

Our case reflects the usual middle-aged female presentation of such a tendon rupture. The tendon ruptures were spontaneous in the reported order of ulnar to radial, beginning with the little and ring fingers, and progressed radially. The patient had isolated Madelung deformity with no other sign of dyschondrosteosis¹³ or dwarfism, conditions commonly mentioned in association with Madelung deformity. This case report should raise awareness about possible tendon rupture in any chronic case of Madelung deformity.

A few days after an incidental cat bite, a patient presented to the emergency department for treatment of poison sumac exposure. He was discharged with oral methylprednisolone for the dermatitis and returned 1 week later with symptoms, examination findings, and laboratory results consistent with sepsis and bilateral upper extremity necrotizing soft-tissue infections. After administering multiple irrigation and débridement procedures, hyperbaric oxygen treatments, and an antibiotic regimen, the patient’s status greatly improved. However, the patient returned 1 month later with a new sternoclavicular joint prominence that was associated with painful crepitus. Additionally, he noted that his wrists were gradually becoming more swollen and painful. Imaging studies showed a lytic destruction of the sternoclavicular joint and erosive changes throughout the carpus and radiocarpal joint bilaterally, consistent with osteomyelitis. The patient was treated with ertapenem for 6 weeks, and his polyarthropathy resolved. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 73-year-old, right-hand–dominant man with no notable medical history presented to the emergency department for treatment of poison sumac exposure, incidentally, a few days after being bitten by a cat on the bilateral distal upper extremities. He was prescribed a course of oral methylprednisolone for dermatitis. A week later, the patient returned to the emergency department with altered mental status, fevers, diaphoresis, lethargy, and polyarthralgia. At the time of presentation, the patient’s vital signs were labile, and he was found to have extensive bilateral upper extremity erythema, blistering, petechiae, purpuric lesions, and exquisite pain with passive range of motion of his fingers and wrists. His leukocyte count was 25.1 × 10⁹/L, and he had elevated C-reactive protein level and erythrocyte sedimentation rate of 150 mg/L and 120 mm/h, respectively. He was admitted for management of sepsis and presumed bilateral upper extremity necrotizing soft-tissue infection.

Broad-spectrum intravenous (IV) antibiotics (vancomycin, piperacillin, tazobactam) were initiated after blood cultures were obtained, and the patient was taken emergently to the operating theatre for irrigation and débridement of his hands and wrists bilaterally. Arthrotomy of the wrist and débridement of the distal extensor compartment and its tenosynovium were performed on the right forearm, in addition to a decompressive fasciotomy of the left forearm. Postoperatively, the patient’s mental status improved and his vital signs gradually normalized. He received multiple hyperbaric oxygen treatments and underwent several additional operative débridement procedures with eventual closure of his wounds. At initial presentation, the differential diagnosis for the severe soft-tissue infection included necrotizing fasciitis or myositis caused by any of a variety of bacterial pathogens. Most notably, it was important to elicit the history of a cat bite to include and consider Pasteurella multocida as a potential pathogen. Initial cultures supported the diagnosis of acute P multocida necrotizing skin and soft-tissue infection, in addition to septic arthritis. The patient’s blood and intraoperative wound cultures grew P multocida. The antibiotic treatment was tailored initially to ampicillin and sulbactam and then to a final regimen of orally administered ciprofloxacin (750 mg twice a day), once susceptibility testing was performed on the cultures. On hospital day 10, the patient was discharged home, receiving a 6-week course of ciprofloxacin to complete the 8-week course of treatment.

At follow-up, approximately 1 month after discharge, the patient noted that he had developed a new right sternoclavicular joint prominence that was associated with painful crepitus. He also noted that his wrists were gradually becoming more swollen and painful bilaterally. Computed tomography scans of the chest were obtained to evaluate the sternoclavicular joint (Figure 1). Repeat radiographs of the wrists were also obtained (Figure 2). Imaging showed lytic destruction of the sternoclavicular joint and erosive changes throughout the carpus and radiocarpal joint, consistent with osteomyelitis. The C-reactive protein level and erythrocyte sedimentation rate at this time were 34 mg/L and 124 mm/h, respectively.

The patient returned to the operating room for débridement and biopsy of the right sternoclavicular joint and left wrist. This patient’s delayed presentation was characterized by a subacute worsening of isolated musculoskeletal complaints. The differential diagnosis then included infection with the same bacterial pathogen versus reactive or inflammatory arthritis. Several intraoperative cultures failed to grow any bacteria, including P multocida, although P multocida was the presumptive cause of the erosive polyarthropathy, considering that symptoms eventually resolved with a repeated course of IV-administered ertapenem for 6 weeks. The patient experienced complete resolution of his joint pain and swelling. He was able to resume his activities of daily living and had no further recurrence of symptoms at follow-up 3 months later.

Discussion

Cat bites often are the source of Pasteurella species infections because the bacteria are carried by more than 90% of cats.¹ These types of infections can cause septic arthritis, osteomyelitis, and deep subcutaneous and myofascial infections because of the sharp and narrow morphology of cat teeth. The infections can progress to necrotizing fasciitis and myositis if not recognized early, as was the case with our patient. Prophylactic antibiotic administration for animal bites is controversial and is not a universal practice.^1,2Pasteurella bacteremia is an atypical progression that occurs more often in patients with pneumonia, septic arthritis, or meningitis. Cases of Pasteurella sepsis, necrotizing fasciitis, and septic arthritis have been reported.^3-7 However, associated progressive septic arthritis and osteomyelitis, despite initial clinical improvement, have not been reported. Severe infection (ie, sepsis and septic shock) can occur in infants, pregnant women, and other immunocompromised patients.⁷ Immune suppression of our patient with steroid medication for poison sumac dermatitis likely contributed to the progression and systemic spread of an initially benign cat bite. Before prescribing steroids, it is imperative to ask about exposures and encourage patients to seek prompt medical attention with worsening or new symptoms. Healthy individuals rarely develop bacteremia; however, in these cases, mortality remains high at approximately 25%.^4,6

The clinical course of this case emphasizes the need for vigilance and thoroughness in obtaining histories from patients presenting with seemingly benign complaints, especially in vulnerable populations, such as infants, pregnant women, and immunocompromised adults. In this case, the progression of symptoms might have been avoided if the patient’s dermatitis had been treated conservatively or with topical rather than systemic steroids.

A few days after an incidental cat bite, a patient presented to the emergency department for treatment of poison sumac exposure. He was discharged with oral methylprednisolone for the dermatitis and returned 1 week later with symptoms, examination findings, and laboratory results consistent with sepsis and bilateral upper extremity necrotizing soft-tissue infections. After administering multiple irrigation and débridement procedures, hyperbaric oxygen treatments, and an antibiotic regimen, the patient’s status greatly improved. However, the patient returned 1 month later with a new sternoclavicular joint prominence that was associated with painful crepitus. Additionally, he noted that his wrists were gradually becoming more swollen and painful. Imaging studies showed a lytic destruction of the sternoclavicular joint and erosive changes throughout the carpus and radiocarpal joint bilaterally, consistent with osteomyelitis. The patient was treated with ertapenem for 6 weeks, and his polyarthropathy resolved. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 73-year-old, right-hand–dominant man with no notable medical history presented to the emergency department for treatment of poison sumac exposure, incidentally, a few days after being bitten by a cat on the bilateral distal upper extremities. He was prescribed a course of oral methylprednisolone for dermatitis. A week later, the patient returned to the emergency department with altered mental status, fevers, diaphoresis, lethargy, and polyarthralgia. At the time of presentation, the patient’s vital signs were labile, and he was found to have extensive bilateral upper extremity erythema, blistering, petechiae, purpuric lesions, and exquisite pain with passive range of motion of his fingers and wrists. His leukocyte count was 25.1 × 10⁹/L, and he had elevated C-reactive protein level and erythrocyte sedimentation rate of 150 mg/L and 120 mm/h, respectively. He was admitted for management of sepsis and presumed bilateral upper extremity necrotizing soft-tissue infection.

Broad-spectrum intravenous (IV) antibiotics (vancomycin, piperacillin, tazobactam) were initiated after blood cultures were obtained, and the patient was taken emergently to the operating theatre for irrigation and débridement of his hands and wrists bilaterally. Arthrotomy of the wrist and débridement of the distal extensor compartment and its tenosynovium were performed on the right forearm, in addition to a decompressive fasciotomy of the left forearm. Postoperatively, the patient’s mental status improved and his vital signs gradually normalized. He received multiple hyperbaric oxygen treatments and underwent several additional operative débridement procedures with eventual closure of his wounds. At initial presentation, the differential diagnosis for the severe soft-tissue infection included necrotizing fasciitis or myositis caused by any of a variety of bacterial pathogens. Most notably, it was important to elicit the history of a cat bite to include and consider Pasteurella multocida as a potential pathogen. Initial cultures supported the diagnosis of acute P multocida necrotizing skin and soft-tissue infection, in addition to septic arthritis. The patient’s blood and intraoperative wound cultures grew P multocida. The antibiotic treatment was tailored initially to ampicillin and sulbactam and then to a final regimen of orally administered ciprofloxacin (750 mg twice a day), once susceptibility testing was performed on the cultures. On hospital day 10, the patient was discharged home, receiving a 6-week course of ciprofloxacin to complete the 8-week course of treatment.

At follow-up, approximately 1 month after discharge, the patient noted that he had developed a new right sternoclavicular joint prominence that was associated with painful crepitus. He also noted that his wrists were gradually becoming more swollen and painful bilaterally. Computed tomography scans of the chest were obtained to evaluate the sternoclavicular joint (Figure 1). Repeat radiographs of the wrists were also obtained (Figure 2). Imaging showed lytic destruction of the sternoclavicular joint and erosive changes throughout the carpus and radiocarpal joint, consistent with osteomyelitis. The C-reactive protein level and erythrocyte sedimentation rate at this time were 34 mg/L and 124 mm/h, respectively.

The patient returned to the operating room for débridement and biopsy of the right sternoclavicular joint and left wrist. This patient’s delayed presentation was characterized by a subacute worsening of isolated musculoskeletal complaints. The differential diagnosis then included infection with the same bacterial pathogen versus reactive or inflammatory arthritis. Several intraoperative cultures failed to grow any bacteria, including P multocida, although P multocida was the presumptive cause of the erosive polyarthropathy, considering that symptoms eventually resolved with a repeated course of IV-administered ertapenem for 6 weeks. The patient experienced complete resolution of his joint pain and swelling. He was able to resume his activities of daily living and had no further recurrence of symptoms at follow-up 3 months later.

Discussion

Cat bites often are the source of Pasteurella species infections because the bacteria are carried by more than 90% of cats.¹ These types of infections can cause septic arthritis, osteomyelitis, and deep subcutaneous and myofascial infections because of the sharp and narrow morphology of cat teeth. The infections can progress to necrotizing fasciitis and myositis if not recognized early, as was the case with our patient. Prophylactic antibiotic administration for animal bites is controversial and is not a universal practice.^1,2Pasteurella bacteremia is an atypical progression that occurs more often in patients with pneumonia, septic arthritis, or meningitis. Cases of Pasteurella sepsis, necrotizing fasciitis, and septic arthritis have been reported.^3-7 However, associated progressive septic arthritis and osteomyelitis, despite initial clinical improvement, have not been reported. Severe infection (ie, sepsis and septic shock) can occur in infants, pregnant women, and other immunocompromised patients.⁷ Immune suppression of our patient with steroid medication for poison sumac dermatitis likely contributed to the progression and systemic spread of an initially benign cat bite. Before prescribing steroids, it is imperative to ask about exposures and encourage patients to seek prompt medical attention with worsening or new symptoms. Healthy individuals rarely develop bacteremia; however, in these cases, mortality remains high at approximately 25%.^4,6

The clinical course of this case emphasizes the need for vigilance and thoroughness in obtaining histories from patients presenting with seemingly benign complaints, especially in vulnerable populations, such as infants, pregnant women, and immunocompromised adults. In this case, the progression of symptoms might have been avoided if the patient’s dermatitis had been treated conservatively or with topical rather than systemic steroids.

A few days after an incidental cat bite, a patient presented to the emergency department for treatment of poison sumac exposure. He was discharged with oral methylprednisolone for the dermatitis and returned 1 week later with symptoms, examination findings, and laboratory results consistent with sepsis and bilateral upper extremity necrotizing soft-tissue infections. After administering multiple irrigation and débridement procedures, hyperbaric oxygen treatments, and an antibiotic regimen, the patient’s status greatly improved. However, the patient returned 1 month later with a new sternoclavicular joint prominence that was associated with painful crepitus. Additionally, he noted that his wrists were gradually becoming more swollen and painful. Imaging studies showed a lytic destruction of the sternoclavicular joint and erosive changes throughout the carpus and radiocarpal joint bilaterally, consistent with osteomyelitis. The patient was treated with ertapenem for 6 weeks, and his polyarthropathy resolved. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A 73-year-old, right-hand–dominant man with no notable medical history presented to the emergency department for treatment of poison sumac exposure, incidentally, a few days after being bitten by a cat on the bilateral distal upper extremities. He was prescribed a course of oral methylprednisolone for dermatitis. A week later, the patient returned to the emergency department with altered mental status, fevers, diaphoresis, lethargy, and polyarthralgia. At the time of presentation, the patient’s vital signs were labile, and he was found to have extensive bilateral upper extremity erythema, blistering, petechiae, purpuric lesions, and exquisite pain with passive range of motion of his fingers and wrists. His leukocyte count was 25.1 × 10⁹/L, and he had elevated C-reactive protein level and erythrocyte sedimentation rate of 150 mg/L and 120 mm/h, respectively. He was admitted for management of sepsis and presumed bilateral upper extremity necrotizing soft-tissue infection.

Broad-spectrum intravenous (IV) antibiotics (vancomycin, piperacillin, tazobactam) were initiated after blood cultures were obtained, and the patient was taken emergently to the operating theatre for irrigation and débridement of his hands and wrists bilaterally. Arthrotomy of the wrist and débridement of the distal extensor compartment and its tenosynovium were performed on the right forearm, in addition to a decompressive fasciotomy of the left forearm. Postoperatively, the patient’s mental status improved and his vital signs gradually normalized. He received multiple hyperbaric oxygen treatments and underwent several additional operative débridement procedures with eventual closure of his wounds. At initial presentation, the differential diagnosis for the severe soft-tissue infection included necrotizing fasciitis or myositis caused by any of a variety of bacterial pathogens. Most notably, it was important to elicit the history of a cat bite to include and consider Pasteurella multocida as a potential pathogen. Initial cultures supported the diagnosis of acute P multocida necrotizing skin and soft-tissue infection, in addition to septic arthritis. The patient’s blood and intraoperative wound cultures grew P multocida. The antibiotic treatment was tailored initially to ampicillin and sulbactam and then to a final regimen of orally administered ciprofloxacin (750 mg twice a day), once susceptibility testing was performed on the cultures. On hospital day 10, the patient was discharged home, receiving a 6-week course of ciprofloxacin to complete the 8-week course of treatment.

At follow-up, approximately 1 month after discharge, the patient noted that he had developed a new right sternoclavicular joint prominence that was associated with painful crepitus. He also noted that his wrists were gradually becoming more swollen and painful bilaterally. Computed tomography scans of the chest were obtained to evaluate the sternoclavicular joint (Figure 1). Repeat radiographs of the wrists were also obtained (Figure 2). Imaging showed lytic destruction of the sternoclavicular joint and erosive changes throughout the carpus and radiocarpal joint, consistent with osteomyelitis. The C-reactive protein level and erythrocyte sedimentation rate at this time were 34 mg/L and 124 mm/h, respectively.

The patient returned to the operating room for débridement and biopsy of the right sternoclavicular joint and left wrist. This patient’s delayed presentation was characterized by a subacute worsening of isolated musculoskeletal complaints. The differential diagnosis then included infection with the same bacterial pathogen versus reactive or inflammatory arthritis. Several intraoperative cultures failed to grow any bacteria, including P multocida, although P multocida was the presumptive cause of the erosive polyarthropathy, considering that symptoms eventually resolved with a repeated course of IV-administered ertapenem for 6 weeks. The patient experienced complete resolution of his joint pain and swelling. He was able to resume his activities of daily living and had no further recurrence of symptoms at follow-up 3 months later.

Discussion

Cat bites often are the source of Pasteurella species infections because the bacteria are carried by more than 90% of cats.¹ These types of infections can cause septic arthritis, osteomyelitis, and deep subcutaneous and myofascial infections because of the sharp and narrow morphology of cat teeth. The infections can progress to necrotizing fasciitis and myositis if not recognized early, as was the case with our patient. Prophylactic antibiotic administration for animal bites is controversial and is not a universal practice.^1,2Pasteurella bacteremia is an atypical progression that occurs more often in patients with pneumonia, septic arthritis, or meningitis. Cases of Pasteurella sepsis, necrotizing fasciitis, and septic arthritis have been reported.^3-7 However, associated progressive septic arthritis and osteomyelitis, despite initial clinical improvement, have not been reported. Severe infection (ie, sepsis and septic shock) can occur in infants, pregnant women, and other immunocompromised patients.⁷ Immune suppression of our patient with steroid medication for poison sumac dermatitis likely contributed to the progression and systemic spread of an initially benign cat bite. Before prescribing steroids, it is imperative to ask about exposures and encourage patients to seek prompt medical attention with worsening or new symptoms. Healthy individuals rarely develop bacteremia; however, in these cases, mortality remains high at approximately 25%.^4,6

The clinical course of this case emphasizes the need for vigilance and thoroughness in obtaining histories from patients presenting with seemingly benign complaints, especially in vulnerable populations, such as infants, pregnant women, and immunocompromised adults. In this case, the progression of symptoms might have been avoided if the patient’s dermatitis had been treated conservatively or with topical rather than systemic steroids.

According to the literature, the rate of deep venous thrombosis after total hip arthroplasty (THA) can be high (45%-63%) without prophylactic anticoagulation.^1-6 A meta-analysis of 13 studies found a rate of 51%.⁷ As lower extremity deep venous thrombi are the initial source of symptomatic pulmonary emboli in about 90% of cases,⁸ THA patients are usually given medication postoperatively focused on prevention of these thromboembolic events.⁹ Chemoprophylaxis may involve warfarin, enoxaparin, or their combination in an anticoagulation bridge. Enoxaparin is one of many low-molecular-weight heparins (LMWHs). All LMWHs exert their anticoagulant effect by binding to antithrombin III.¹⁰ The binding of LMWH to antithrombin III catalyzes the inhibition of factor Xa by antithrombin III, disrupting clot formation.¹¹

In its hydroquinone form, vitamin K is essential as a cofactor for carboxylation of the glutamic acid residues of the amino-terminals of the coagulation proteins II, VII, IX, and X, leading to their activation. Anticoagulation by warfarin is achieved by the inhibition of the reductase enzymes that produce vitamin K hydroquinone in the liver from vitamin K epoxide.¹² This inhibition prevents activation of the clotting proteins.^12,13 Prophylaxis with enoxaparin or warfarin can reduce the rate of venous thromboembolic disease to 3.6% and 3.7%, respectively.² However, these medications inhibit the clotting cascade, and their use risks prolonging the healing process.⁹ The delay increases the risk for wound infection,¹⁴ which can lead to a longer hospital stay and therefore higher costs.

We conducted a study to compare patients who received warfarin only with patients who received warfarin bridged with enoxaparin as antithrombotic chemoprophylaxis after THA. Outcomes of interest were number of days until a dry wound was observed and length of hospital stay. We hypothesized that, compared with warfarin-only therapy, bridged therapy would increase the risk for prolonged wound healing and result in longer hospital stays.

Materials and Methods

At our 746-bed academic medical center, 121 THAs were performed between January 1, 2008 and December 31, 2009. This study was approved by the center’s Office for Human Subjects Protections institutional review board (IRB). The research involved collecting or studying existing data, documents, and records recorded anonymously by the investigator in such a manner that subjects could not be identified, directly or through identifiers linked to the subjects, and therefore patient consent was not needed. Therefore, the IRB waived the need for consent. Relevant data included in this study were extracted from patient medical records, given within 35 days of surgery. For each patient, discharge notes provided data on the hospital course, and nurses’ notes provided data on wound status after THA.

Propensity Score Matching

For accurate analysis, it was important to consider confounding factors in both patient groups. Some covariates that may influence accurate analysis are age,¹⁵ diabetes,¹⁶ sex,^15,17 hypertension,¹⁸ and body mass index.^15,19Propensity score, defined as the conditional probability of receiving treatment, given the observed background covariates, was initially defined by Rosenbaum²⁰ and Rubin.²¹ The motivation behind propensity scores can be understood by considering an idealized situation in which the 2 groups are similar on all background characteristics. In nonexperimental studies, researchers aim to find for each treated individual a comparison individual who looks exactly the same as the treated individual with respect to observed pretreatment covariates. Thus, assuming no hidden bias, any difference in outcomes within these pairs can be attributed to the variable of interest and not to any other differences between the treated and comparison individuals. Our study is a typical nonexperimental retrospective study in which the 2 groups being compared are patients receiving warfarin only or warfarin bridged with enoxaparin. To minimize the influence of background covariates, we used matching procedures and present our results both with and without the use of matching techniques.

Data and Results

There are different matching algorithms aimed at matching groups. In our study, the optimal matching procedure alone could not produce adequately matched data, so we used both optimal matching²⁰ and genetic matching.^22,23 Genetic matching procedure with replacement²² can produce well-matched data—it matched each patient in the warfarin-only group with a patient in the bridged-therapy group and allowed different patients to be matched with 1 similar patient in the control group. However, as the same patients in the bridged-therapy group might be matched multiple times, it would complicate the after-matching analysis. We therefore used a 2-step matching procedure to obtain well-matched data, and a simplified analysis procedure after matching. In the first step, we implemented genetic matching with replacement, as introduced by Abadie and Imbens,²² to match each warfarin-only patient with 1 bridged-therapy patient. In the second step, we applied optimal matching to the 2 groups. This 2-step matching turned out to produce better matched pairs, as denoted by Rubin.²¹ Both matching steps were implemented using the MatchIt function in R.²⁴

The balance of matching is checked using criteria suggested by Rubin²¹: (1) standardized difference of means of propensity score, (2) ratio of variances in propensity score in treated and control groups, and (3) for each covariate, ratio of variance in residuals orthogonal to propensity score in treated and control groups.

Table 1 lists the means of the background covariates for each group before and after matching. Table 2 lists the balance check results suggested by Rubin.²¹ After matching, all standardized differences of means are smaller than 0.25, and the variance ratios are between 0.5 and 2, which are the standards suggested²¹ for regression adjustment to be valid after matching.

After genetic matching, 31 bridged-therapy patients and 57 warfarin-only patients remained. After optimal matching, there were 31 patients in each group. Poisson regressions of datasets before and after matching adjustment were fitted.

Results

Wounds of bridged-therapy patients took longer to heal than wounds of warfarin-only patients both before (odds ratio, 2.16; P < .05) and after matching data (odds ratio, 2.39; P < .05) with respect to confounding factors. In addition, bridged-therapy patients had longer hospital stays both before (odds ratio 1.20; P < .05) and after matching data (odds ratio, 1.27; P < .05) with respect to confounding factors. Figures 1 and 2 are histograms displaying the 2 groups and their outcomes.

Discussion

For patients undergoing THA procedures, several important considerations should be taken into account. Colwell and colleagues² showed that, compared with warfarin, enoxaparin offered a 0.1% higher rate of protection against venous thromboembolic disease after THA. However, patients given enoxaparin may face increased risks.²⁵ Hallevi and colleagues²⁶ demonstrated that, compared with warfarin, enoxaparin bridging increased the risk for serious bleeding in patients with cardioembolic stroke. In our review of the literature, we learned that the benefits of bridge therapy in thromboembolic disease have yet to be investigated in THA.

At our academic hospital, the extra costs associated with bridge therapy can be as much as about $2000²⁷ per day per patient. These costs can go much higher, depending on type of patient and types of resources used. Over the 2-year period covered by our study, the costs of using enoxaparin amounted to about $151,200 ($2000 × 1.2 days per patient). If bridging offers no significant protection against thromboembolic disease, then it would be more cost-effective to use a single anticoagulant, particularly enoxaparin, for high-risk patients.

There are significant risk factors associated with prolonged healing of surgical wounds. Protocols outlining these factors may help reduce costs. In addition, when deciding on the use of aggressive anticoagulation therapy, surgeons must consider the risks for prolonged leakage and infection in addition to the risk for thromboembolic disease. Protocols may aid in this process as well. Our study results showed that, compared with warfarin-only therapy, bridged therapy (enoxaparin and warfarin) was associated with longer hospital stays. Further research should examine whether there are advantages that justify the higher risks of delayed wound healing and subsequent infection. Improving our understanding of risk factors associated with anticoagulation therapy will make orthopedic surgery safer for patients.

According to the literature, the rate of deep venous thrombosis after total hip arthroplasty (THA) can be high (45%-63%) without prophylactic anticoagulation.^1-6 A meta-analysis of 13 studies found a rate of 51%.⁷ As lower extremity deep venous thrombi are the initial source of symptomatic pulmonary emboli in about 90% of cases,⁸ THA patients are usually given medication postoperatively focused on prevention of these thromboembolic events.⁹ Chemoprophylaxis may involve warfarin, enoxaparin, or their combination in an anticoagulation bridge. Enoxaparin is one of many low-molecular-weight heparins (LMWHs). All LMWHs exert their anticoagulant effect by binding to antithrombin III.¹⁰ The binding of LMWH to antithrombin III catalyzes the inhibition of factor Xa by antithrombin III, disrupting clot formation.¹¹

In its hydroquinone form, vitamin K is essential as a cofactor for carboxylation of the glutamic acid residues of the amino-terminals of the coagulation proteins II, VII, IX, and X, leading to their activation. Anticoagulation by warfarin is achieved by the inhibition of the reductase enzymes that produce vitamin K hydroquinone in the liver from vitamin K epoxide.¹² This inhibition prevents activation of the clotting proteins.^12,13 Prophylaxis with enoxaparin or warfarin can reduce the rate of venous thromboembolic disease to 3.6% and 3.7%, respectively.² However, these medications inhibit the clotting cascade, and their use risks prolonging the healing process.⁹ The delay increases the risk for wound infection,¹⁴ which can lead to a longer hospital stay and therefore higher costs.

We conducted a study to compare patients who received warfarin only with patients who received warfarin bridged with enoxaparin as antithrombotic chemoprophylaxis after THA. Outcomes of interest were number of days until a dry wound was observed and length of hospital stay. We hypothesized that, compared with warfarin-only therapy, bridged therapy would increase the risk for prolonged wound healing and result in longer hospital stays.

Materials and Methods

At our 746-bed academic medical center, 121 THAs were performed between January 1, 2008 and December 31, 2009. This study was approved by the center’s Office for Human Subjects Protections institutional review board (IRB). The research involved collecting or studying existing data, documents, and records recorded anonymously by the investigator in such a manner that subjects could not be identified, directly or through identifiers linked to the subjects, and therefore patient consent was not needed. Therefore, the IRB waived the need for consent. Relevant data included in this study were extracted from patient medical records, given within 35 days of surgery. For each patient, discharge notes provided data on the hospital course, and nurses’ notes provided data on wound status after THA.

Propensity Score Matching

For accurate analysis, it was important to consider confounding factors in both patient groups. Some covariates that may influence accurate analysis are age,¹⁵ diabetes,¹⁶ sex,^15,17 hypertension,¹⁸ and body mass index.^15,19Propensity score, defined as the conditional probability of receiving treatment, given the observed background covariates, was initially defined by Rosenbaum²⁰ and Rubin.²¹ The motivation behind propensity scores can be understood by considering an idealized situation in which the 2 groups are similar on all background characteristics. In nonexperimental studies, researchers aim to find for each treated individual a comparison individual who looks exactly the same as the treated individual with respect to observed pretreatment covariates. Thus, assuming no hidden bias, any difference in outcomes within these pairs can be attributed to the variable of interest and not to any other differences between the treated and comparison individuals. Our study is a typical nonexperimental retrospective study in which the 2 groups being compared are patients receiving warfarin only or warfarin bridged with enoxaparin. To minimize the influence of background covariates, we used matching procedures and present our results both with and without the use of matching techniques.

Data and Results

There are different matching algorithms aimed at matching groups. In our study, the optimal matching procedure alone could not produce adequately matched data, so we used both optimal matching²⁰ and genetic matching.^22,23 Genetic matching procedure with replacement²² can produce well-matched data—it matched each patient in the warfarin-only group with a patient in the bridged-therapy group and allowed different patients to be matched with 1 similar patient in the control group. However, as the same patients in the bridged-therapy group might be matched multiple times, it would complicate the after-matching analysis. We therefore used a 2-step matching procedure to obtain well-matched data, and a simplified analysis procedure after matching. In the first step, we implemented genetic matching with replacement, as introduced by Abadie and Imbens,²² to match each warfarin-only patient with 1 bridged-therapy patient. In the second step, we applied optimal matching to the 2 groups. This 2-step matching turned out to produce better matched pairs, as denoted by Rubin.²¹ Both matching steps were implemented using the MatchIt function in R.²⁴

The balance of matching is checked using criteria suggested by Rubin²¹: (1) standardized difference of means of propensity score, (2) ratio of variances in propensity score in treated and control groups, and (3) for each covariate, ratio of variance in residuals orthogonal to propensity score in treated and control groups.

Table 1 lists the means of the background covariates for each group before and after matching. Table 2 lists the balance check results suggested by Rubin.²¹ After matching, all standardized differences of means are smaller than 0.25, and the variance ratios are between 0.5 and 2, which are the standards suggested²¹ for regression adjustment to be valid after matching.

After genetic matching, 31 bridged-therapy patients and 57 warfarin-only patients remained. After optimal matching, there were 31 patients in each group. Poisson regressions of datasets before and after matching adjustment were fitted.

Results

Wounds of bridged-therapy patients took longer to heal than wounds of warfarin-only patients both before (odds ratio, 2.16; P < .05) and after matching data (odds ratio, 2.39; P < .05) with respect to confounding factors. In addition, bridged-therapy patients had longer hospital stays both before (odds ratio 1.20; P < .05) and after matching data (odds ratio, 1.27; P < .05) with respect to confounding factors. Figures 1 and 2 are histograms displaying the 2 groups and their outcomes.

Discussion

For patients undergoing THA procedures, several important considerations should be taken into account. Colwell and colleagues² showed that, compared with warfarin, enoxaparin offered a 0.1% higher rate of protection against venous thromboembolic disease after THA. However, patients given enoxaparin may face increased risks.²⁵ Hallevi and colleagues²⁶ demonstrated that, compared with warfarin, enoxaparin bridging increased the risk for serious bleeding in patients with cardioembolic stroke. In our review of the literature, we learned that the benefits of bridge therapy in thromboembolic disease have yet to be investigated in THA.

At our academic hospital, the extra costs associated with bridge therapy can be as much as about $2000²⁷ per day per patient. These costs can go much higher, depending on type of patient and types of resources used. Over the 2-year period covered by our study, the costs of using enoxaparin amounted to about $151,200 ($2000 × 1.2 days per patient). If bridging offers no significant protection against thromboembolic disease, then it would be more cost-effective to use a single anticoagulant, particularly enoxaparin, for high-risk patients.

There are significant risk factors associated with prolonged healing of surgical wounds. Protocols outlining these factors may help reduce costs. In addition, when deciding on the use of aggressive anticoagulation therapy, surgeons must consider the risks for prolonged leakage and infection in addition to the risk for thromboembolic disease. Protocols may aid in this process as well. Our study results showed that, compared with warfarin-only therapy, bridged therapy (enoxaparin and warfarin) was associated with longer hospital stays. Further research should examine whether there are advantages that justify the higher risks of delayed wound healing and subsequent infection. Improving our understanding of risk factors associated with anticoagulation therapy will make orthopedic surgery safer for patients.

According to the literature, the rate of deep venous thrombosis after total hip arthroplasty (THA) can be high (45%-63%) without prophylactic anticoagulation.^1-6 A meta-analysis of 13 studies found a rate of 51%.⁷ As lower extremity deep venous thrombi are the initial source of symptomatic pulmonary emboli in about 90% of cases,⁸ THA patients are usually given medication postoperatively focused on prevention of these thromboembolic events.⁹ Chemoprophylaxis may involve warfarin, enoxaparin, or their combination in an anticoagulation bridge. Enoxaparin is one of many low-molecular-weight heparins (LMWHs). All LMWHs exert their anticoagulant effect by binding to antithrombin III.¹⁰ The binding of LMWH to antithrombin III catalyzes the inhibition of factor Xa by antithrombin III, disrupting clot formation.¹¹

In its hydroquinone form, vitamin K is essential as a cofactor for carboxylation of the glutamic acid residues of the amino-terminals of the coagulation proteins II, VII, IX, and X, leading to their activation. Anticoagulation by warfarin is achieved by the inhibition of the reductase enzymes that produce vitamin K hydroquinone in the liver from vitamin K epoxide.¹² This inhibition prevents activation of the clotting proteins.^12,13 Prophylaxis with enoxaparin or warfarin can reduce the rate of venous thromboembolic disease to 3.6% and 3.7%, respectively.² However, these medications inhibit the clotting cascade, and their use risks prolonging the healing process.⁹ The delay increases the risk for wound infection,¹⁴ which can lead to a longer hospital stay and therefore higher costs.

We conducted a study to compare patients who received warfarin only with patients who received warfarin bridged with enoxaparin as antithrombotic chemoprophylaxis after THA. Outcomes of interest were number of days until a dry wound was observed and length of hospital stay. We hypothesized that, compared with warfarin-only therapy, bridged therapy would increase the risk for prolonged wound healing and result in longer hospital stays.

Materials and Methods

At our 746-bed academic medical center, 121 THAs were performed between January 1, 2008 and December 31, 2009. This study was approved by the center’s Office for Human Subjects Protections institutional review board (IRB). The research involved collecting or studying existing data, documents, and records recorded anonymously by the investigator in such a manner that subjects could not be identified, directly or through identifiers linked to the subjects, and therefore patient consent was not needed. Therefore, the IRB waived the need for consent. Relevant data included in this study were extracted from patient medical records, given within 35 days of surgery. For each patient, discharge notes provided data on the hospital course, and nurses’ notes provided data on wound status after THA.

Propensity Score Matching

For accurate analysis, it was important to consider confounding factors in both patient groups. Some covariates that may influence accurate analysis are age,¹⁵ diabetes,¹⁶ sex,^15,17 hypertension,¹⁸ and body mass index.^15,19Propensity score, defined as the conditional probability of receiving treatment, given the observed background covariates, was initially defined by Rosenbaum²⁰ and Rubin.²¹ The motivation behind propensity scores can be understood by considering an idealized situation in which the 2 groups are similar on all background characteristics. In nonexperimental studies, researchers aim to find for each treated individual a comparison individual who looks exactly the same as the treated individual with respect to observed pretreatment covariates. Thus, assuming no hidden bias, any difference in outcomes within these pairs can be attributed to the variable of interest and not to any other differences between the treated and comparison individuals. Our study is a typical nonexperimental retrospective study in which the 2 groups being compared are patients receiving warfarin only or warfarin bridged with enoxaparin. To minimize the influence of background covariates, we used matching procedures and present our results both with and without the use of matching techniques.

Data and Results

There are different matching algorithms aimed at matching groups. In our study, the optimal matching procedure alone could not produce adequately matched data, so we used both optimal matching²⁰ and genetic matching.^22,23 Genetic matching procedure with replacement²² can produce well-matched data—it matched each patient in the warfarin-only group with a patient in the bridged-therapy group and allowed different patients to be matched with 1 similar patient in the control group. However, as the same patients in the bridged-therapy group might be matched multiple times, it would complicate the after-matching analysis. We therefore used a 2-step matching procedure to obtain well-matched data, and a simplified analysis procedure after matching. In the first step, we implemented genetic matching with replacement, as introduced by Abadie and Imbens,²² to match each warfarin-only patient with 1 bridged-therapy patient. In the second step, we applied optimal matching to the 2 groups. This 2-step matching turned out to produce better matched pairs, as denoted by Rubin.²¹ Both matching steps were implemented using the MatchIt function in R.²⁴

The balance of matching is checked using criteria suggested by Rubin²¹: (1) standardized difference of means of propensity score, (2) ratio of variances in propensity score in treated and control groups, and (3) for each covariate, ratio of variance in residuals orthogonal to propensity score in treated and control groups.

Table 1 lists the means of the background covariates for each group before and after matching. Table 2 lists the balance check results suggested by Rubin.²¹ After matching, all standardized differences of means are smaller than 0.25, and the variance ratios are between 0.5 and 2, which are the standards suggested²¹ for regression adjustment to be valid after matching.

After genetic matching, 31 bridged-therapy patients and 57 warfarin-only patients remained. After optimal matching, there were 31 patients in each group. Poisson regressions of datasets before and after matching adjustment were fitted.

Results

Wounds of bridged-therapy patients took longer to heal than wounds of warfarin-only patients both before (odds ratio, 2.16; P < .05) and after matching data (odds ratio, 2.39; P < .05) with respect to confounding factors. In addition, bridged-therapy patients had longer hospital stays both before (odds ratio 1.20; P < .05) and after matching data (odds ratio, 1.27; P < .05) with respect to confounding factors. Figures 1 and 2 are histograms displaying the 2 groups and their outcomes.

Discussion

For patients undergoing THA procedures, several important considerations should be taken into account. Colwell and colleagues² showed that, compared with warfarin, enoxaparin offered a 0.1% higher rate of protection against venous thromboembolic disease after THA. However, patients given enoxaparin may face increased risks.²⁵ Hallevi and colleagues²⁶ demonstrated that, compared with warfarin, enoxaparin bridging increased the risk for serious bleeding in patients with cardioembolic stroke. In our review of the literature, we learned that the benefits of bridge therapy in thromboembolic disease have yet to be investigated in THA.

At our academic hospital, the extra costs associated with bridge therapy can be as much as about $2000²⁷ per day per patient. These costs can go much higher, depending on type of patient and types of resources used. Over the 2-year period covered by our study, the costs of using enoxaparin amounted to about $151,200 ($2000 × 1.2 days per patient). If bridging offers no significant protection against thromboembolic disease, then it would be more cost-effective to use a single anticoagulant, particularly enoxaparin, for high-risk patients.

There are significant risk factors associated with prolonged healing of surgical wounds. Protocols outlining these factors may help reduce costs. In addition, when deciding on the use of aggressive anticoagulation therapy, surgeons must consider the risks for prolonged leakage and infection in addition to the risk for thromboembolic disease. Protocols may aid in this process as well. Our study results showed that, compared with warfarin-only therapy, bridged therapy (enoxaparin and warfarin) was associated with longer hospital stays. Further research should examine whether there are advantages that justify the higher risks of delayed wound healing and subsequent infection. Improving our understanding of risk factors associated with anticoagulation therapy will make orthopedic surgery safer for patients.

Restoration of stability with return to activity is generally expected after anterior cruciate ligament (ACL) reconstruction; long-term success rates range from 75% to 95%.¹ However, graft failure occurs most frequently with soft-tissue grafts fixated only with interference screws.^2,3 Fixation failure also occurs more frequently at the tibial site.² This failure has been attributed to extensive graft slippage in cases of soft-tissue fixation with interference screws.² Interference screw fixation alone, with a double-looped hamstring tendon graft, fails at 350 N in young human tibiae.^4,5 However, failure is limited with use of a bone–tendon–bone graft or with backup fixation, particularly at the tibial site.³ The superiority of bicortical fixation has also been proven.^5-7

In addition, as shown in a goat model, ACL graft fixation is a major cause of failure in the immediate postoperative period, before biological incorporation of the graft.⁸ Fixation techniques for soft-tissue grafts must withstand stresses during the healing period (grafts may take up to 12 weeks to incorporate).⁹ Failures may result from forces exerted on the graft—forces that may be as high as 450 to 700 N during daily activities.^10,11 Within the tibial tunnel, various fixation devices are used, including interference screws, staples, pins, buttons, and interference screw/sheath constructs.^12,13 Primary fixation is commonly achieved with interference screws because of their ease of insertion and greater stiffness. However, fixation of the soft-tissue graft is influenced by several variables, including bone density, insertion torque, thread geometry, and interference screw material.^14-16 Many of these variables, which are a source of inconsistency and concern during the immediate postoperative period, have led surgeons to seek alternative methods of backup fixation at the tibial site. Nevertheless, good clinical and subjective results have been found after ACL reconstruction with a 4-stranded semitendinosus tendon at 10-year follow-up.¹⁷

An anchor used in rotator cuff repair is the SwiveLock system (Arthrex). Major advantages of this system include ease and speed of insertion, good strength, and reduced need for later hardware removal.

We conducted a study to biomechanically evaluate 3 methods of tibial-sided fixation for ACL reconstruction: fully threaded interference screw only, interference screw backed with 4.75-mm SwiveLock anchor, and fully threaded bio-interference screw backed with 4.5-mm bicortical screw. We hypothesized that a fully threaded bio-interference screw backed with a 4.75-mm SwiveLock anchor would provide mechanical strength no different from that provided by backup fixation with a bicortical post at the tibial site. We further hypothesized that SwiveLock backup fixation would provide more strength than fixation with bio-interference screw alone.

Materials and Methods

The design of this study was adapted from one used by Walsh and colleagues,³ who compared 3 fixation methods: retrograde interference screw, suture button, and combined fixation. Tibiae inspected before selection showed no signs of injury or abnormality. Bovine extensor tendons, which lacked any defects along their entire length, were stored in saline 0.9% solution. Both the tibiae and the extensor tendons were stored at –20°C before completion of the tibial-sided ACL reconstruction. Thirty fresh-frozen, skeletally mature porcine proximal tibiae were selected and thawed at 4°C before preparation. Specimens were prepared by potting the diaphysis in fiberglass resin, and a tunnel 9 mm in diameter was drilled through the anteromedial aspect of the tibia.

For consistency, one author (CAV) prepared all 30 specimens. Both tails of all 30 bovine extensor tendons were whip-stitched with No. 2 FiberLoop (Arthrex) 9 mm in diameter. Grafts and tibiae were randomly divided into 3 sample groups. The first group was prepared by antegrade graft fixation within the tibial tunnel using a fully threaded 9×28-mm BioComposite interference screw (Arthrex). The second and third groups used the same primary fixation within the tibial tunnel along with 2 types of secondary fixation. These backup fixation groups included a 4.5-mm titanium bicortical post (Arthrex) and a 4.75-mm BioComposite SwiveLock C anchor (Arthrex) (Figure 1). The FiberLoop at the ends of the distal graft tails for backup groups were fixated 1 cm distal to the tibial tunnel and tapped before insertion of backup devices (Figures 2A, 2B). Insertion was completed after 4.5-mm bicortical and 4.75-mm unicortical drilling and tapping of the anteromedial cortices for the titanium posts and SwiveLocks, respectively. The free ends of the whip-stitched No. 2 FiberLoop were tied to the proximal end of the titanium post with a single surgical knot followed by 5 square knots.³ The free ends of the No. 2 FiberLoop were inserted into the eyelet of the 4.75-mm SwiveLock and 1 cm directly inferior to the tibial tunnel. Interference fit of FiberLoop with SwiveLock was achieved within the corticocancellous bone of the tibiae. All samples retained a 30-mm tendon loop superior to the tibial plateau to simulate intra-articular ACL length. Specimens were then stored at –20°C and thawed at 4°C before biomechanical testing.

Each of the 30 tibiae was tested once. Each testing group consisted of 10 porcine tibiae. The tendons were kept moist during the entire testing procedure by spraying them thoroughly with saline 0.9% solution. Mechanical testing was performed with an Instron 8871 system with a 5-kN load cell secured to the crosshead. A fixed-angle aperture, attached to the testing surface, was adjusted so that the tendon would be pulled in line with the tibial tunnel. A hook fixture suspended from clevis and dowel was used to secure the tendon to the crosshead (Figure 3). A small preload of 5 N manually applied to each sample was followed by a precycling regimen of 10 cycles between 10 N and 50 N at 1 Hz. Precycling was performed to remove slack from the system. Mechanical testing consisted of 500 cycles between 50 N and 250 N at 1 Hz followed by pull to failure at 20 mm per minute. Load and displacement data were recorded at 500 Hz.

An a priori power analysis was not performed because 6 specimens per group in the study from which the testing protocol was adapted demonstrated sufficient power among 3 testing categories.³ In addition, other studies have demonstrated similar testing protocols using 10 specimens per testing group.^7,12,13,18 The data for each sample were analyzed with OriginPro 8.0 software (OriginLab). Ultimate load, yield load, stiffness, and cyclic displacement of the 3 sample groups were compared with 1-way analysis of variance (α = 0.05). Holm-Sidak tests were used for post hoc analysis.¹⁹P < .05 was statistically significant.

Results

None of the 30 specimens failed during preloading. Modes of failure were consistent among groups. All 10 specimens in the interference-screw-only group failed by graft slippage past the screw in the tibial tunnel. Nineteen of the 20 specimens in the backup-fixation groups failed by graft slippage past the screw and suture cutout through the distal graft tail. In the bicortical-post backup group, 1 failure was attributed to tendon tearing proximal to whip-stitching. There were no instances of hardware breakage or failure of either titanium screw or SwiveLock anchor.

Mean (SD) cyclic displacement was higher in the interference-screw-only group, 3.5 (2.2) mm, than in the SwiveLock backup group, 2.6 (0.5) mm, and the bicortical-post backup group, 2.1 (0.6) mm; no statistical significance was demonstrated between any 2 of these groups alone (P = .12) (Figure 4). Mean (SD) pullout stiff­ness was higher in the bicortical-post backup group, 192 (48) N/mm, than in the SwiveLock backup group, 164 (53) N/mm, and the screw-only group, 163 (64) N/mm (P = .42) (Figure 5). Mean (SD) initial load at 5 mm of displacement was higher in the bicortical-post backup group, 482 (156) N, and the SwiveLock backup group, 423 (94) N, than in the screw-only group, 381 (169) N (P = .30).

Mean (SD) yield load was higher in the bicortical-post backup group, 829 (253) N, than in the SwiveLock backup group, 642 (172) N, and the interference-screw-only group, 496 (133) N (P = .003). Statistical significance was demonstrated between the screw-only and bicortical-post groups (P = .002) and between the screw-only and SwiveLock groups (P = .048). There was no statistical difference between the bicortical-post and SwiveLock groups (P = .07).

Mean (SD) ultimate load to failure was higher in the bicortical-post backup group, 1148 (186) N, than in the SwiveLock backup group, 1007 (176) N, and the interference-screw-only group, 778 (139) N (Figure 6). The difference was statistically significant, whereby the screw-only group failed at a lower load compared with the bicortical-post group (P < .001) and the SwiveLock group (P = .005). The 2 backup groups were not statistically different (P = .1).

Discussion

We investigated whether a fully threaded bio-interference screw backed with a 4.75-mm SwiveLock anchor would provide mechanically equivalent pullout strength within the tibial tunnel during ACL reconstruction with soft-tissue allografts in comparison either with a fully threaded bio-interference screw backed with a bicortical post or with a fully threaded bio-interference screw without backup fixation. The results of the study support this hypothesis. With SwiveLock used for backup fixation, there was no significant difference in stiffness or cyclic load displacement between the screw-only, SwiveLock, and bicortical-post groups. However, adding backup fixation could particularly help improve fixation consistency. Specifically, although after only 500 cycles there was no statistically significant difference in cyclic displacement, continued cycling may be clinically relevant if graft slippage exceeded limits to allow for healing within the tibial tunnel. Conversely, a significantly larger difference was found between the SwiveLock, bicortical-post, and screw-only groups in yield load and ultimate load to failure. However, there was no significant difference between the SwiveLock and bicortical-post groups.

 In this study, interference screw with SwiveLock backup demonstrated a mean (SD) ultimate load to failure of 1007 (176) N, comparable to that found by Walsh and colleagues³ for retrograde bio-interference screw with suture button, 1027 (157.11) N. In a study comparing quadrupled hamstring tibial graft fixation, Intrafix (DePuy Mitek) and an 8×25-mm Bioscrew (Linvatec) demonstrated mean (SD) single-cycle yield loads of 1332 (304) N and 612 (176) N, respectively.¹³ These results are similar to the ultimate yield loads in the present study: bicortical-post group, 1148 (186) N; SwiveLock group, 1007 (176) N; screw-only group, 778 (139) N. Differences may be attributed to hamstring tendons used in a quadrupled manner in the aforementioned study.^12,13 Last, mean (SD) ultimate load to failure in a study that used only a retrograde bio-interference screw (9×20 mm) was 679.00 (109.44) N,³ similar to the 778 (139) N found for interference-screw-only in the present study. The difference is likely attributable to the longer screw (9×28 mm) in our study. Using SwiveLock C in cortical bone, Barber and colleagues¹⁸ found mean (SD) loads to failure up to 711.9 (89.1) N.

Clinically, it has been shown that a statistically significant increase in anterior laxity occurred between 4 months and 2 years in 10.7% of patients who underwent hamstring ACL reconstruction.²⁰ The knees were clinically categorized as unstable or severely abnormal. The authors concluded that the clinical outcome was more likely influenced by the methods used to fix the free ends of the graft, specifically with 2 staples or a washer. To simulate early postoperative rehabilitation in the present study, cyclic loading of the graft was performed. Ultimate load to failure was then determined in order to evaluate catastrophic failure strength of the backup fixation devices in comparison with the interference-screw-only group without supplementary fixation.

It has been shown in autologous hamstring ACL reconstruction that a centrally placed polyethylene screw with sheath (Intrafix) performed as well as a standard, eccentrically placed metal interference screw with staple.¹⁰ It is therefore logical that backup fixation with use of a similar device (eg, SwiveLock, bicortical post) is necessary to ensure comparable clinical outcomes in relation to a screw/sheath device that has been shown to endure the highest yield loads.^{2,9,12,13,21-23} Potential benefits of using SwiveLock anchors for backup fixation include a statistically significant increased mean (SD) ultimate yield load of 229 (176) N over interference screw only. These results are similar to those in comparable studies: 218.3 (59.7) N²⁴ and 165 (24.15) N²⁵ in healthy bone with a reported bone mineral density (BMD) of 1.39 g/cm², similar to that of skeletally mature porcine tibia (1.220-1.675 g/cm²).³ In addition, ease of insertion of this device over a bicortical post was demonstrated. The titanium post required bicortical drilling as well as measurement with a depth gauge to ensure adequate screw length. This process appeared to require more time during specimen preparation and theoretically could prove to be more dangerous clinically.⁷ However, caution in using a SwiveLock anchor in osteoporotic bone is advised because of reduced pullout strength.²⁶ In this case, bicortical-post backup fixation may be more suitable. Moreover, although not demonstrated in this study, hardware prominence and irritation with a post may cause postoperative morbidity necessitating future removal.²⁰ Hardware removal was the most common reason for additional surgery using hamstring tendons as graft.²⁰ A second surgery for hardware removal was required in 21% of these patients.²⁰ This is unlikely to occur with a SwiveLock, as the anchor is buried within cortical bone.

Limitations

Regarding use of nonhuman tissues in a biomechanical model, porcine tibiae and bovine extensor tendons were used because of availability, consistency among specimens, and cost-effectiveness. However, bovine extensor tendons have been shown to exhibit stiffness and viscoelastic properties similar to those of a human hamstring graft.²⁷ In addition, the BMD of the porcine tibiae used in this study was not tested because of time involved and cost-efficiency. However, it has been shown that average BMD of porcine tibiae, 1.220-1.675 g/cm², is similar to that in a young athletic population, 1.24-1.62 g/cm².^3,28-31 We therefore assumed similarity to a young athletic population and uniformity of BMD of the porcine tibiae used in this study.

In addition, the biomechanical testing protocol did not simulate physiologic loading within the tibial tunnel. Moreover, the testing protocol used loads of only 250 N during cyclic testing for 500 cycles. This simulates only the early rehabilitation period and not the healing period, which may last up to 12 weeks.⁹ In addition, as previously mentioned, forces on the graft may be as high as 450 to 700 N.^11,32 Pullout testing in line with the long axis of the tibia was performed in order to compare mechanical testing results with those of similar studies.^3,12,13 Last, the P of .07 for the comparison of ultimate load to failure between the 2 backup fixation groups suggests that this study may have been underpowered.

Conclusion

This study demonstrated an effective, alternative, and equivalent backup fixation device that can help prevent graft slippage within the tibial tunnel during soft-tissue ACL reconstruction. Potential benefits of using SwiveLock anchors for backup fixation include a significantly increased ultimate yield load (229 N) when supplementing an interference screw, ease of insertion compared with a bicortical post, and the improbable need for future hardware removal. We support using SwiveLock for supplementary fixation at the tibial tunnel site when using soft-tissue grafts in ACL reconstruction.

Restoration of stability with return to activity is generally expected after anterior cruciate ligament (ACL) reconstruction; long-term success rates range from 75% to 95%.¹ However, graft failure occurs most frequently with soft-tissue grafts fixated only with interference screws.^2,3 Fixation failure also occurs more frequently at the tibial site.² This failure has been attributed to extensive graft slippage in cases of soft-tissue fixation with interference screws.² Interference screw fixation alone, with a double-looped hamstring tendon graft, fails at 350 N in young human tibiae.^4,5 However, failure is limited with use of a bone–tendon–bone graft or with backup fixation, particularly at the tibial site.³ The superiority of bicortical fixation has also been proven.^5-7

In addition, as shown in a goat model, ACL graft fixation is a major cause of failure in the immediate postoperative period, before biological incorporation of the graft.⁸ Fixation techniques for soft-tissue grafts must withstand stresses during the healing period (grafts may take up to 12 weeks to incorporate).⁹ Failures may result from forces exerted on the graft—forces that may be as high as 450 to 700 N during daily activities.^10,11 Within the tibial tunnel, various fixation devices are used, including interference screws, staples, pins, buttons, and interference screw/sheath constructs.^12,13 Primary fixation is commonly achieved with interference screws because of their ease of insertion and greater stiffness. However, fixation of the soft-tissue graft is influenced by several variables, including bone density, insertion torque, thread geometry, and interference screw material.^14-16 Many of these variables, which are a source of inconsistency and concern during the immediate postoperative period, have led surgeons to seek alternative methods of backup fixation at the tibial site. Nevertheless, good clinical and subjective results have been found after ACL reconstruction with a 4-stranded semitendinosus tendon at 10-year follow-up.¹⁷

An anchor used in rotator cuff repair is the SwiveLock system (Arthrex). Major advantages of this system include ease and speed of insertion, good strength, and reduced need for later hardware removal.

We conducted a study to biomechanically evaluate 3 methods of tibial-sided fixation for ACL reconstruction: fully threaded interference screw only, interference screw backed with 4.75-mm SwiveLock anchor, and fully threaded bio-interference screw backed with 4.5-mm bicortical screw. We hypothesized that a fully threaded bio-interference screw backed with a 4.75-mm SwiveLock anchor would provide mechanical strength no different from that provided by backup fixation with a bicortical post at the tibial site. We further hypothesized that SwiveLock backup fixation would provide more strength than fixation with bio-interference screw alone.

Materials and Methods

The design of this study was adapted from one used by Walsh and colleagues,³ who compared 3 fixation methods: retrograde interference screw, suture button, and combined fixation. Tibiae inspected before selection showed no signs of injury or abnormality. Bovine extensor tendons, which lacked any defects along their entire length, were stored in saline 0.9% solution. Both the tibiae and the extensor tendons were stored at –20°C before completion of the tibial-sided ACL reconstruction. Thirty fresh-frozen, skeletally mature porcine proximal tibiae were selected and thawed at 4°C before preparation. Specimens were prepared by potting the diaphysis in fiberglass resin, and a tunnel 9 mm in diameter was drilled through the anteromedial aspect of the tibia.

For consistency, one author (CAV) prepared all 30 specimens. Both tails of all 30 bovine extensor tendons were whip-stitched with No. 2 FiberLoop (Arthrex) 9 mm in diameter. Grafts and tibiae were randomly divided into 3 sample groups. The first group was prepared by antegrade graft fixation within the tibial tunnel using a fully threaded 9×28-mm BioComposite interference screw (Arthrex). The second and third groups used the same primary fixation within the tibial tunnel along with 2 types of secondary fixation. These backup fixation groups included a 4.5-mm titanium bicortical post (Arthrex) and a 4.75-mm BioComposite SwiveLock C anchor (Arthrex) (Figure 1). The FiberLoop at the ends of the distal graft tails for backup groups were fixated 1 cm distal to the tibial tunnel and tapped before insertion of backup devices (Figures 2A, 2B). Insertion was completed after 4.5-mm bicortical and 4.75-mm unicortical drilling and tapping of the anteromedial cortices for the titanium posts and SwiveLocks, respectively. The free ends of the whip-stitched No. 2 FiberLoop were tied to the proximal end of the titanium post with a single surgical knot followed by 5 square knots.³ The free ends of the No. 2 FiberLoop were inserted into the eyelet of the 4.75-mm SwiveLock and 1 cm directly inferior to the tibial tunnel. Interference fit of FiberLoop with SwiveLock was achieved within the corticocancellous bone of the tibiae. All samples retained a 30-mm tendon loop superior to the tibial plateau to simulate intra-articular ACL length. Specimens were then stored at –20°C and thawed at 4°C before biomechanical testing.

Each of the 30 tibiae was tested once. Each testing group consisted of 10 porcine tibiae. The tendons were kept moist during the entire testing procedure by spraying them thoroughly with saline 0.9% solution. Mechanical testing was performed with an Instron 8871 system with a 5-kN load cell secured to the crosshead. A fixed-angle aperture, attached to the testing surface, was adjusted so that the tendon would be pulled in line with the tibial tunnel. A hook fixture suspended from clevis and dowel was used to secure the tendon to the crosshead (Figure 3). A small preload of 5 N manually applied to each sample was followed by a precycling regimen of 10 cycles between 10 N and 50 N at 1 Hz. Precycling was performed to remove slack from the system. Mechanical testing consisted of 500 cycles between 50 N and 250 N at 1 Hz followed by pull to failure at 20 mm per minute. Load and displacement data were recorded at 500 Hz.

An a priori power analysis was not performed because 6 specimens per group in the study from which the testing protocol was adapted demonstrated sufficient power among 3 testing categories.³ In addition, other studies have demonstrated similar testing protocols using 10 specimens per testing group.^7,12,13,18 The data for each sample were analyzed with OriginPro 8.0 software (OriginLab). Ultimate load, yield load, stiffness, and cyclic displacement of the 3 sample groups were compared with 1-way analysis of variance (α = 0.05). Holm-Sidak tests were used for post hoc analysis.¹⁹P < .05 was statistically significant.

Results

None of the 30 specimens failed during preloading. Modes of failure were consistent among groups. All 10 specimens in the interference-screw-only group failed by graft slippage past the screw in the tibial tunnel. Nineteen of the 20 specimens in the backup-fixation groups failed by graft slippage past the screw and suture cutout through the distal graft tail. In the bicortical-post backup group, 1 failure was attributed to tendon tearing proximal to whip-stitching. There were no instances of hardware breakage or failure of either titanium screw or SwiveLock anchor.

Mean (SD) cyclic displacement was higher in the interference-screw-only group, 3.5 (2.2) mm, than in the SwiveLock backup group, 2.6 (0.5) mm, and the bicortical-post backup group, 2.1 (0.6) mm; no statistical significance was demonstrated between any 2 of these groups alone (P = .12) (Figure 4). Mean (SD) pullout stiff­ness was higher in the bicortical-post backup group, 192 (48) N/mm, than in the SwiveLock backup group, 164 (53) N/mm, and the screw-only group, 163 (64) N/mm (P = .42) (Figure 5). Mean (SD) initial load at 5 mm of displacement was higher in the bicortical-post backup group, 482 (156) N, and the SwiveLock backup group, 423 (94) N, than in the screw-only group, 381 (169) N (P = .30).

Mean (SD) yield load was higher in the bicortical-post backup group, 829 (253) N, than in the SwiveLock backup group, 642 (172) N, and the interference-screw-only group, 496 (133) N (P = .003). Statistical significance was demonstrated between the screw-only and bicortical-post groups (P = .002) and between the screw-only and SwiveLock groups (P = .048). There was no statistical difference between the bicortical-post and SwiveLock groups (P = .07).

Mean (SD) ultimate load to failure was higher in the bicortical-post backup group, 1148 (186) N, than in the SwiveLock backup group, 1007 (176) N, and the interference-screw-only group, 778 (139) N (Figure 6). The difference was statistically significant, whereby the screw-only group failed at a lower load compared with the bicortical-post group (P < .001) and the SwiveLock group (P = .005). The 2 backup groups were not statistically different (P = .1).

Discussion

We investigated whether a fully threaded bio-interference screw backed with a 4.75-mm SwiveLock anchor would provide mechanically equivalent pullout strength within the tibial tunnel during ACL reconstruction with soft-tissue allografts in comparison either with a fully threaded bio-interference screw backed with a bicortical post or with a fully threaded bio-interference screw without backup fixation. The results of the study support this hypothesis. With SwiveLock used for backup fixation, there was no significant difference in stiffness or cyclic load displacement between the screw-only, SwiveLock, and bicortical-post groups. However, adding backup fixation could particularly help improve fixation consistency. Specifically, although after only 500 cycles there was no statistically significant difference in cyclic displacement, continued cycling may be clinically relevant if graft slippage exceeded limits to allow for healing within the tibial tunnel. Conversely, a significantly larger difference was found between the SwiveLock, bicortical-post, and screw-only groups in yield load and ultimate load to failure. However, there was no significant difference between the SwiveLock and bicortical-post groups.

 In this study, interference screw with SwiveLock backup demonstrated a mean (SD) ultimate load to failure of 1007 (176) N, comparable to that found by Walsh and colleagues³ for retrograde bio-interference screw with suture button, 1027 (157.11) N. In a study comparing quadrupled hamstring tibial graft fixation, Intrafix (DePuy Mitek) and an 8×25-mm Bioscrew (Linvatec) demonstrated mean (SD) single-cycle yield loads of 1332 (304) N and 612 (176) N, respectively.¹³ These results are similar to the ultimate yield loads in the present study: bicortical-post group, 1148 (186) N; SwiveLock group, 1007 (176) N; screw-only group, 778 (139) N. Differences may be attributed to hamstring tendons used in a quadrupled manner in the aforementioned study.^12,13 Last, mean (SD) ultimate load to failure in a study that used only a retrograde bio-interference screw (9×20 mm) was 679.00 (109.44) N,³ similar to the 778 (139) N found for interference-screw-only in the present study. The difference is likely attributable to the longer screw (9×28 mm) in our study. Using SwiveLock C in cortical bone, Barber and colleagues¹⁸ found mean (SD) loads to failure up to 711.9 (89.1) N.

Clinically, it has been shown that a statistically significant increase in anterior laxity occurred between 4 months and 2 years in 10.7% of patients who underwent hamstring ACL reconstruction.²⁰ The knees were clinically categorized as unstable or severely abnormal. The authors concluded that the clinical outcome was more likely influenced by the methods used to fix the free ends of the graft, specifically with 2 staples or a washer. To simulate early postoperative rehabilitation in the present study, cyclic loading of the graft was performed. Ultimate load to failure was then determined in order to evaluate catastrophic failure strength of the backup fixation devices in comparison with the interference-screw-only group without supplementary fixation.

It has been shown in autologous hamstring ACL reconstruction that a centrally placed polyethylene screw with sheath (Intrafix) performed as well as a standard, eccentrically placed metal interference screw with staple.¹⁰ It is therefore logical that backup fixation with use of a similar device (eg, SwiveLock, bicortical post) is necessary to ensure comparable clinical outcomes in relation to a screw/sheath device that has been shown to endure the highest yield loads.^{2,9,12,13,21-23} Potential benefits of using SwiveLock anchors for backup fixation include a statistically significant increased mean (SD) ultimate yield load of 229 (176) N over interference screw only. These results are similar to those in comparable studies: 218.3 (59.7) N²⁴ and 165 (24.15) N²⁵ in healthy bone with a reported bone mineral density (BMD) of 1.39 g/cm², similar to that of skeletally mature porcine tibia (1.220-1.675 g/cm²).³ In addition, ease of insertion of this device over a bicortical post was demonstrated. The titanium post required bicortical drilling as well as measurement with a depth gauge to ensure adequate screw length. This process appeared to require more time during specimen preparation and theoretically could prove to be more dangerous clinically.⁷ However, caution in using a SwiveLock anchor in osteoporotic bone is advised because of reduced pullout strength.²⁶ In this case, bicortical-post backup fixation may be more suitable. Moreover, although not demonstrated in this study, hardware prominence and irritation with a post may cause postoperative morbidity necessitating future removal.²⁰ Hardware removal was the most common reason for additional surgery using hamstring tendons as graft.²⁰ A second surgery for hardware removal was required in 21% of these patients.²⁰ This is unlikely to occur with a SwiveLock, as the anchor is buried within cortical bone.

Limitations

Regarding use of nonhuman tissues in a biomechanical model, porcine tibiae and bovine extensor tendons were used because of availability, consistency among specimens, and cost-effectiveness. However, bovine extensor tendons have been shown to exhibit stiffness and viscoelastic properties similar to those of a human hamstring graft.²⁷ In addition, the BMD of the porcine tibiae used in this study was not tested because of time involved and cost-efficiency. However, it has been shown that average BMD of porcine tibiae, 1.220-1.675 g/cm², is similar to that in a young athletic population, 1.24-1.62 g/cm².^3,28-31 We therefore assumed similarity to a young athletic population and uniformity of BMD of the porcine tibiae used in this study.

In addition, the biomechanical testing protocol did not simulate physiologic loading within the tibial tunnel. Moreover, the testing protocol used loads of only 250 N during cyclic testing for 500 cycles. This simulates only the early rehabilitation period and not the healing period, which may last up to 12 weeks.⁹ In addition, as previously mentioned, forces on the graft may be as high as 450 to 700 N.^11,32 Pullout testing in line with the long axis of the tibia was performed in order to compare mechanical testing results with those of similar studies.^3,12,13 Last, the P of .07 for the comparison of ultimate load to failure between the 2 backup fixation groups suggests that this study may have been underpowered.

Conclusion

This study demonstrated an effective, alternative, and equivalent backup fixation device that can help prevent graft slippage within the tibial tunnel during soft-tissue ACL reconstruction. Potential benefits of using SwiveLock anchors for backup fixation include a significantly increased ultimate yield load (229 N) when supplementing an interference screw, ease of insertion compared with a bicortical post, and the improbable need for future hardware removal. We support using SwiveLock for supplementary fixation at the tibial tunnel site when using soft-tissue grafts in ACL reconstruction.

Restoration of stability with return to activity is generally expected after anterior cruciate ligament (ACL) reconstruction; long-term success rates range from 75% to 95%.¹ However, graft failure occurs most frequently with soft-tissue grafts fixated only with interference screws.^2,3 Fixation failure also occurs more frequently at the tibial site.² This failure has been attributed to extensive graft slippage in cases of soft-tissue fixation with interference screws.² Interference screw fixation alone, with a double-looped hamstring tendon graft, fails at 350 N in young human tibiae.^4,5 However, failure is limited with use of a bone–tendon–bone graft or with backup fixation, particularly at the tibial site.³ The superiority of bicortical fixation has also been proven.^5-7

In addition, as shown in a goat model, ACL graft fixation is a major cause of failure in the immediate postoperative period, before biological incorporation of the graft.⁸ Fixation techniques for soft-tissue grafts must withstand stresses during the healing period (grafts may take up to 12 weeks to incorporate).⁹ Failures may result from forces exerted on the graft—forces that may be as high as 450 to 700 N during daily activities.^10,11 Within the tibial tunnel, various fixation devices are used, including interference screws, staples, pins, buttons, and interference screw/sheath constructs.^12,13 Primary fixation is commonly achieved with interference screws because of their ease of insertion and greater stiffness. However, fixation of the soft-tissue graft is influenced by several variables, including bone density, insertion torque, thread geometry, and interference screw material.^14-16 Many of these variables, which are a source of inconsistency and concern during the immediate postoperative period, have led surgeons to seek alternative methods of backup fixation at the tibial site. Nevertheless, good clinical and subjective results have been found after ACL reconstruction with a 4-stranded semitendinosus tendon at 10-year follow-up.¹⁷

An anchor used in rotator cuff repair is the SwiveLock system (Arthrex). Major advantages of this system include ease and speed of insertion, good strength, and reduced need for later hardware removal.

We conducted a study to biomechanically evaluate 3 methods of tibial-sided fixation for ACL reconstruction: fully threaded interference screw only, interference screw backed with 4.75-mm SwiveLock anchor, and fully threaded bio-interference screw backed with 4.5-mm bicortical screw. We hypothesized that a fully threaded bio-interference screw backed with a 4.75-mm SwiveLock anchor would provide mechanical strength no different from that provided by backup fixation with a bicortical post at the tibial site. We further hypothesized that SwiveLock backup fixation would provide more strength than fixation with bio-interference screw alone.

Materials and Methods

The design of this study was adapted from one used by Walsh and colleagues,³ who compared 3 fixation methods: retrograde interference screw, suture button, and combined fixation. Tibiae inspected before selection showed no signs of injury or abnormality. Bovine extensor tendons, which lacked any defects along their entire length, were stored in saline 0.9% solution. Both the tibiae and the extensor tendons were stored at –20°C before completion of the tibial-sided ACL reconstruction. Thirty fresh-frozen, skeletally mature porcine proximal tibiae were selected and thawed at 4°C before preparation. Specimens were prepared by potting the diaphysis in fiberglass resin, and a tunnel 9 mm in diameter was drilled through the anteromedial aspect of the tibia.

For consistency, one author (CAV) prepared all 30 specimens. Both tails of all 30 bovine extensor tendons were whip-stitched with No. 2 FiberLoop (Arthrex) 9 mm in diameter. Grafts and tibiae were randomly divided into 3 sample groups. The first group was prepared by antegrade graft fixation within the tibial tunnel using a fully threaded 9×28-mm BioComposite interference screw (Arthrex). The second and third groups used the same primary fixation within the tibial tunnel along with 2 types of secondary fixation. These backup fixation groups included a 4.5-mm titanium bicortical post (Arthrex) and a 4.75-mm BioComposite SwiveLock C anchor (Arthrex) (Figure 1). The FiberLoop at the ends of the distal graft tails for backup groups were fixated 1 cm distal to the tibial tunnel and tapped before insertion of backup devices (Figures 2A, 2B). Insertion was completed after 4.5-mm bicortical and 4.75-mm unicortical drilling and tapping of the anteromedial cortices for the titanium posts and SwiveLocks, respectively. The free ends of the whip-stitched No. 2 FiberLoop were tied to the proximal end of the titanium post with a single surgical knot followed by 5 square knots.³ The free ends of the No. 2 FiberLoop were inserted into the eyelet of the 4.75-mm SwiveLock and 1 cm directly inferior to the tibial tunnel. Interference fit of FiberLoop with SwiveLock was achieved within the corticocancellous bone of the tibiae. All samples retained a 30-mm tendon loop superior to the tibial plateau to simulate intra-articular ACL length. Specimens were then stored at –20°C and thawed at 4°C before biomechanical testing.

Each of the 30 tibiae was tested once. Each testing group consisted of 10 porcine tibiae. The tendons were kept moist during the entire testing procedure by spraying them thoroughly with saline 0.9% solution. Mechanical testing was performed with an Instron 8871 system with a 5-kN load cell secured to the crosshead. A fixed-angle aperture, attached to the testing surface, was adjusted so that the tendon would be pulled in line with the tibial tunnel. A hook fixture suspended from clevis and dowel was used to secure the tendon to the crosshead (Figure 3). A small preload of 5 N manually applied to each sample was followed by a precycling regimen of 10 cycles between 10 N and 50 N at 1 Hz. Precycling was performed to remove slack from the system. Mechanical testing consisted of 500 cycles between 50 N and 250 N at 1 Hz followed by pull to failure at 20 mm per minute. Load and displacement data were recorded at 500 Hz.

An a priori power analysis was not performed because 6 specimens per group in the study from which the testing protocol was adapted demonstrated sufficient power among 3 testing categories.³ In addition, other studies have demonstrated similar testing protocols using 10 specimens per testing group.^7,12,13,18 The data for each sample were analyzed with OriginPro 8.0 software (OriginLab). Ultimate load, yield load, stiffness, and cyclic displacement of the 3 sample groups were compared with 1-way analysis of variance (α = 0.05). Holm-Sidak tests were used for post hoc analysis.¹⁹P < .05 was statistically significant.

Results

None of the 30 specimens failed during preloading. Modes of failure were consistent among groups. All 10 specimens in the interference-screw-only group failed by graft slippage past the screw in the tibial tunnel. Nineteen of the 20 specimens in the backup-fixation groups failed by graft slippage past the screw and suture cutout through the distal graft tail. In the bicortical-post backup group, 1 failure was attributed to tendon tearing proximal to whip-stitching. There were no instances of hardware breakage or failure of either titanium screw or SwiveLock anchor.

Mean (SD) cyclic displacement was higher in the interference-screw-only group, 3.5 (2.2) mm, than in the SwiveLock backup group, 2.6 (0.5) mm, and the bicortical-post backup group, 2.1 (0.6) mm; no statistical significance was demonstrated between any 2 of these groups alone (P = .12) (Figure 4). Mean (SD) pullout stiff­ness was higher in the bicortical-post backup group, 192 (48) N/mm, than in the SwiveLock backup group, 164 (53) N/mm, and the screw-only group, 163 (64) N/mm (P = .42) (Figure 5). Mean (SD) initial load at 5 mm of displacement was higher in the bicortical-post backup group, 482 (156) N, and the SwiveLock backup group, 423 (94) N, than in the screw-only group, 381 (169) N (P = .30).

Mean (SD) yield load was higher in the bicortical-post backup group, 829 (253) N, than in the SwiveLock backup group, 642 (172) N, and the interference-screw-only group, 496 (133) N (P = .003). Statistical significance was demonstrated between the screw-only and bicortical-post groups (P = .002) and between the screw-only and SwiveLock groups (P = .048). There was no statistical difference between the bicortical-post and SwiveLock groups (P = .07).

Mean (SD) ultimate load to failure was higher in the bicortical-post backup group, 1148 (186) N, than in the SwiveLock backup group, 1007 (176) N, and the interference-screw-only group, 778 (139) N (Figure 6). The difference was statistically significant, whereby the screw-only group failed at a lower load compared with the bicortical-post group (P < .001) and the SwiveLock group (P = .005). The 2 backup groups were not statistically different (P = .1).

Discussion

We investigated whether a fully threaded bio-interference screw backed with a 4.75-mm SwiveLock anchor would provide mechanically equivalent pullout strength within the tibial tunnel during ACL reconstruction with soft-tissue allografts in comparison either with a fully threaded bio-interference screw backed with a bicortical post or with a fully threaded bio-interference screw without backup fixation. The results of the study support this hypothesis. With SwiveLock used for backup fixation, there was no significant difference in stiffness or cyclic load displacement between the screw-only, SwiveLock, and bicortical-post groups. However, adding backup fixation could particularly help improve fixation consistency. Specifically, although after only 500 cycles there was no statistically significant difference in cyclic displacement, continued cycling may be clinically relevant if graft slippage exceeded limits to allow for healing within the tibial tunnel. Conversely, a significantly larger difference was found between the SwiveLock, bicortical-post, and screw-only groups in yield load and ultimate load to failure. However, there was no significant difference between the SwiveLock and bicortical-post groups.

 In this study, interference screw with SwiveLock backup demonstrated a mean (SD) ultimate load to failure of 1007 (176) N, comparable to that found by Walsh and colleagues³ for retrograde bio-interference screw with suture button, 1027 (157.11) N. In a study comparing quadrupled hamstring tibial graft fixation, Intrafix (DePuy Mitek) and an 8×25-mm Bioscrew (Linvatec) demonstrated mean (SD) single-cycle yield loads of 1332 (304) N and 612 (176) N, respectively.¹³ These results are similar to the ultimate yield loads in the present study: bicortical-post group, 1148 (186) N; SwiveLock group, 1007 (176) N; screw-only group, 778 (139) N. Differences may be attributed to hamstring tendons used in a quadrupled manner in the aforementioned study.^12,13 Last, mean (SD) ultimate load to failure in a study that used only a retrograde bio-interference screw (9×20 mm) was 679.00 (109.44) N,³ similar to the 778 (139) N found for interference-screw-only in the present study. The difference is likely attributable to the longer screw (9×28 mm) in our study. Using SwiveLock C in cortical bone, Barber and colleagues¹⁸ found mean (SD) loads to failure up to 711.9 (89.1) N.

Clinically, it has been shown that a statistically significant increase in anterior laxity occurred between 4 months and 2 years in 10.7% of patients who underwent hamstring ACL reconstruction.²⁰ The knees were clinically categorized as unstable or severely abnormal. The authors concluded that the clinical outcome was more likely influenced by the methods used to fix the free ends of the graft, specifically with 2 staples or a washer. To simulate early postoperative rehabilitation in the present study, cyclic loading of the graft was performed. Ultimate load to failure was then determined in order to evaluate catastrophic failure strength of the backup fixation devices in comparison with the interference-screw-only group without supplementary fixation.

It has been shown in autologous hamstring ACL reconstruction that a centrally placed polyethylene screw with sheath (Intrafix) performed as well as a standard, eccentrically placed metal interference screw with staple.¹⁰ It is therefore logical that backup fixation with use of a similar device (eg, SwiveLock, bicortical post) is necessary to ensure comparable clinical outcomes in relation to a screw/sheath device that has been shown to endure the highest yield loads.^{2,9,12,13,21-23} Potential benefits of using SwiveLock anchors for backup fixation include a statistically significant increased mean (SD) ultimate yield load of 229 (176) N over interference screw only. These results are similar to those in comparable studies: 218.3 (59.7) N²⁴ and 165 (24.15) N²⁵ in healthy bone with a reported bone mineral density (BMD) of 1.39 g/cm², similar to that of skeletally mature porcine tibia (1.220-1.675 g/cm²).³ In addition, ease of insertion of this device over a bicortical post was demonstrated. The titanium post required bicortical drilling as well as measurement with a depth gauge to ensure adequate screw length. This process appeared to require more time during specimen preparation and theoretically could prove to be more dangerous clinically.⁷ However, caution in using a SwiveLock anchor in osteoporotic bone is advised because of reduced pullout strength.²⁶ In this case, bicortical-post backup fixation may be more suitable. Moreover, although not demonstrated in this study, hardware prominence and irritation with a post may cause postoperative morbidity necessitating future removal.²⁰ Hardware removal was the most common reason for additional surgery using hamstring tendons as graft.²⁰ A second surgery for hardware removal was required in 21% of these patients.²⁰ This is unlikely to occur with a SwiveLock, as the anchor is buried within cortical bone.

Limitations

Regarding use of nonhuman tissues in a biomechanical model, porcine tibiae and bovine extensor tendons were used because of availability, consistency among specimens, and cost-effectiveness. However, bovine extensor tendons have been shown to exhibit stiffness and viscoelastic properties similar to those of a human hamstring graft.²⁷ In addition, the BMD of the porcine tibiae used in this study was not tested because of time involved and cost-efficiency. However, it has been shown that average BMD of porcine tibiae, 1.220-1.675 g/cm², is similar to that in a young athletic population, 1.24-1.62 g/cm².^3,28-31 We therefore assumed similarity to a young athletic population and uniformity of BMD of the porcine tibiae used in this study.

In addition, the biomechanical testing protocol did not simulate physiologic loading within the tibial tunnel. Moreover, the testing protocol used loads of only 250 N during cyclic testing for 500 cycles. This simulates only the early rehabilitation period and not the healing period, which may last up to 12 weeks.⁹ In addition, as previously mentioned, forces on the graft may be as high as 450 to 700 N.^11,32 Pullout testing in line with the long axis of the tibia was performed in order to compare mechanical testing results with those of similar studies.^3,12,13 Last, the P of .07 for the comparison of ultimate load to failure between the 2 backup fixation groups suggests that this study may have been underpowered.

Conclusion

This study demonstrated an effective, alternative, and equivalent backup fixation device that can help prevent graft slippage within the tibial tunnel during soft-tissue ACL reconstruction. Potential benefits of using SwiveLock anchors for backup fixation include a significantly increased ultimate yield load (229 N) when supplementing an interference screw, ease of insertion compared with a bicortical post, and the improbable need for future hardware removal. We support using SwiveLock for supplementary fixation at the tibial tunnel site when using soft-tissue grafts in ACL reconstruction.

Venous thromboembolic events (VTEs), encompassing both deep vein thrombosis (DVT) and pulmonary embolism (PE), are potentially fatal events that can occur after orthopedic surgery.¹ In patients who do not receive prophylaxis, VTE incidence can be as high as 70% for total hip arthroplasty,² 26% for hip fracture,³ and 5% for ankle fracture.⁴ Based on the relatively low incidence of VTE after ankle fractures and insufficient evidence for VTE prophylaxis in this population, the American Orthopaedic Foot and Ankle Society and the American College of Chest Physicians do not recommend routine screening or prophylaxis for VTE in patients with ankle fractures.^1,5 Nevertheless, certain patients may be at increased risk for VTE after open reduction and internal fixation (ORIF) of an ankle fracture. In such cases, further consideration for prophylaxis may be warranted.

Other studies of VTEs have identified general risk factors of increased age, obesity, prior thromboembolic disease, oral contraceptive use, multitrauma, varicose veins, and prolonged immobilization, among others.^1,6,7 In orthopedics, most of this research comes from total joint arthroplasty and hip fracture studies. However, there is relatively limited data for ankle fracture. The best studies directly addressing VTE after ORIF of ankle fractures have had important limitations, including missing patient data and suboptimal capture of VTE occurrences,^8-10 possibly leading to underestimates of the incidence of VTEs.

Given the limited data available, we conducted a retrospective national-cohort study to determine the incidence of and independent risk factors for VTEs after ankle fracture ORIF. If patients who are at higher risk for VTE can be identified, they can and should be carefully monitored and be considered for VTE prophylaxis. This information is needed for patient counseling and clinical decision-making.

Materials and Methods

This retrospective study used the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database, which captures data from more than 370 participating US hospitals.¹¹ In ACS-NSQIP, 150 patient variables are collected from operative reports, medical records, and patient interviews by trained clinical reviewers.^11,12 Patients are identified prospectively and randomly sampled at participating hospitals. Routine auditing is performed to ensure high-quality data. Clinical data are collected for the entire 30-day postoperative period, regardless of discharge status during this time.

Patients who underwent ankle fracture ORIF between 2005 and 2012 were identified in the ACS-NSQIP database. They were initially selected by the postoperative diagnosis of ankle fracture (International Classification of Diseases, Ninth Revision codes 824.0-824.9). Of these patients, only those with primary Current Procedural Terminology codes 27766 (ORIF of medial malleolus fracture), 27769 (ORIF of posterior malleolus fracture), 27792 (ORIF of lateral malleolus fracture), 27814 (ORIF of bimalleollar fracture), and 27822/27823 (ORIF of trimalleollar fracture) were included in the analysis. Patients with incomplete perioperative data were excluded, leaving 4412 patients (out of the initial 4785) for analysis.

Patient characteristics, including sex, age, height, weight, and history of smoking, were collected from the ACS-NSQIP database. Body mass index (BMI) was calculated from each patient’s height and weight. Age was divided into approximately 20-year increments, beginning with age 18 years, in order to compare younger, middle-aged, and elderly groups of patients with ankle fractures. BMI was divided into categories based on the World Health Organization definitions of obesity: under 25 kg/m² (normal weight), 25 to 30 kg/m² (overweight), 30 to 35 kg/m² (class I obesity), and 35 kg/m² or over (class II and class III obesity).¹³

Information about medical comorbidities is also available in the ACS-NSQIP database. History of pulmonary disease was defined as a history of dyspnea, severe chronic obstructive pulmonary disease, ventilator-assisted respiration within 48 hours before surgery, or current pneumonia. History of heart disease was defined as a history of congestive heart failure (CHF) or angina within 1 month before admission, myocardial infarction within 6 months before admission, cardiac surgery, or percutaneous coronary intervention. American Society of Anesthesiologists (ASA) classes 3 and above signify severe systemic disease. Steroid use was defined as requiring regular administration of corticosteroid medications within 1 month before surgery. Disseminated cancer was defined as a malignancy that has spread to 1 or more sites besides the primary site.

Functional status was defined as the ability to perform activities of daily living (ADLs) within 30 days before surgery. Best functional status during this period was recorded. ACS-NSQIP defines ADLs as the “activities usually performed in the course of a normal day in a person’s life,” including bathing, feeding, dressing, toileting, and mobility. An independent patient does not require assistance for any ADLs; a partially dependent patient requires assistance for some ADLs; and a totally dependent patient requires assistance in all ADLs. Partially and totally dependent patients were grouped for analysis. Anesthesia type was separated into general and nongeneral, which includes monitored anesthesia care, spinal anesthesia, and regional anesthesia.

ACS-NSQIP also records the occurrence of multiple events up to 30 days after surgery. For our study, VTE was defined as the occurrence of a DVT or a PE during this period. ACS-NSQIP defines DVT as a new blood clot or thrombus identified within a vein—with confirmation by duplex ultrasonography, venogram, or computed tomography (CT)—that required therapy (anticoagulation, placement of vena cava filter, and/or clipping of vena cava). PE is recorded if ventilation/perfusion (VQ) scan, CT examination, transesophageal echocardiogram, pulmonary arteriogram, CT angiogram, or any other definitive modality is positive.

Statistical analyses were performed with Stata Version 11.2 (StataCorp). Demographic and comorbidity variables were tested for association with occurrence of VTE using bivariate and multivariate logistic regression.

Final multivariate models were constructed with a backward stepwise process that initially included all potential variables and sequentially excluded variables with the highest P value until only those with P < .200 remained. Variables with .050 < P < .200 were left in the model to control for potential confounding but are not considered significantly associated with the outcome. Statistical significance was established at a 2-sided α of 0.050 (P < .050). The fitness of the final logistic regression model was assessed with the C statistic and the Hosmer-Lemeshow goodness-of-fit test.

Results

For the 4412 ankle fracture patients who met the inclusion criteria, mean (SD) age was 50.9 (18.2) years, and mean (SD) BMI was 30.4 (7.6) kg/m². The cohort was 40.4% male. Surgery was performed on 235 patients (5.3%) with medial malleolus fracture, 1143 patients (25.9%) with lateral malleolus fracture, 1705 patients (38.6%) with bimalleollar fracture, and 1329 patients (30.1%) with trimalleollar fracture. Table 1 summarizes the patient characteristics.

Of the 33 patients (0.8%) with a VTE recorded within the first 30 postoperative days, 16 (0.4% of all patients) had a DVT recorded, 14 (0.3% of all patients) had a PE recorded, and 3 (0.1% of all patients) had both a DVT and a PE recorded. In 13 (39.4%) of the 33 patients with a VTE, the event occurred after discharge. VTEs were reported a mean (SD) of 11.5 (9.6) days after surgery. No patient in this study died of VTE.

Bivariate logistic regressions were performed to test the association of each patient variable with the occurrence of a VTE. Results are listed in Table 2. The bivariate analyses revealed significant associations between VTE after ankle fracture ORIF and the patient variables of age 60 years or older (odds ratio [OR], 2.40; 95% confidence interval [CI], 1.01-5.72), class I obesity (BMI, 30-35 kg/m²: OR, 5.15, 95% CI, 1.14-23.28), class II and class III obesity (BMI, ≥35 kg/m²: OR, 6.33, 95% CI, 1.41-28.38), ASA classes 3 and 4 (OR, 3.05; 95% CI, 1.53-6.08), history of heart disease (OR, 5.10; 95% CI, 2.08-12.49), history of hypertension (OR, 2.81; 95% CI, 1.39-5.66), and dependent functional status (OR, 3.39; 95% CI, 1.52-7.56).

Multivariate logistic regression was used to control for potential confounding variables and determine which factors were independently associated with VTEs. Results of this analysis are listed in Table 2 as well. The multivariate analysis revealed that the patient variables of class I obesity (BMI, 30-35 kg/m²: OR, 4.77; 95% CI, 1.05-21.72; P = .044), class II and class III obesity (BMI, ≥35 kg/m²: OR, 4.71; 95% CI, 1.03-21.68; P = .046), history of heart disease (OR, 3.28; 95% CI, 1.20-8.97; P = .020), and dependent functional status (OR, 2.59; 95% CI, 1.11-6.04; P = .028) were independently associated with an increased rate of VTEs. Of note, anesthesia type was not significantly associated with occurrence of VTE on bivariate or multivariate analysis.

The C statistic of the final multivariate model was 0.76, indicating very good distinguishing ability. The Hosmer-Lemeshow goodness-of-fit test showed no evidence of lack of fit.

Discussion

Citing the lack of conclusive evidence and the low incidence of VTE after ankle fracture surgery, current recommendations are to avoid routine VTE prophylaxis in the postoperative management of patients who undergo this surgery.^1,5 However, it is important to identify patients who are at increased risk, as some may benefit from VTE prophylaxis. In the present study, we used the large, high-quality ACS-NSQIP database collecting information from multiple US hospitals to examine risk factors for VTE after ankle fracture ORIF. We identified 4412 patients who underwent ankle fracture ORIF between 2005 and 2012, and found an overall VTE incidence of 0.8%. Multivariate analysis identified obesity, history of heart disease, and dependent functional status as independent risk factors for VTE after ankle fracture ORIF.

This study’s 0.8% incidence of VTE after ankle fracture ORIF is consistent with the range (0.29%-5%) reported in other ankle fracture studies.^4,8-10,14-18 We found that VTEs occurred a mean of about 11 days after surgery, and no patient died of VTE.

Obesity (BMI, ≥30 kg/m²) had the strongest association with VTEs in this study. Obesity, which is a growing public health concern, can make postoperative care and mobilization more difficult.¹⁹ Obesity has previously been associated with VTEs after ankle fractures, and BMI of over 25 kg/m² is one of the Caprini criteria for thrombosis risk factor assessment.^6,10 In our study, however, BMI of 25 to 30 kg/m² was not associated with an increased VTE rate, indicating that moderately overweight patients may not be at significantly higher risk for VTE (compared with patients with normal BMI) and may not need VTE prophylaxis. VTE prophylaxis after ankle fracture surgery may be considered in patients with BMI over 30 kg/m².

History of heart disease was also associated with VTEs in this study. Patients with a history of heart disease were at 3 times the risk for VTE within 30 days of ankle fracture surgery. This association is also consistent with the Caprini criteria, which include acute myocardial infarction and CHF as risk factors for venous thrombosis.⁶ Other studies have found associations between CHF and VTE and between cardiovascular risk factors and VTE.^7,20 The association between cardiovascular disease and VTE may derive from the decreased venous flow rate associated with CHF or an overall vascular disease state. These patients may benefit from heightened surveillance and postoperative prophylaxis for VTE.

Dependent functional status was the final risk factor found to be associated with VTE after ankle fracture ORIF. This association likely derives from an inability to mobilize independently, leading to increased venous stasis. Immobilization has been previously associated with increased risk for VTE after ankle surgery.^7,14,16,20 Caretakers should be aware of this increased risk during the postoperative period and diligently monitor these patients for signs and symptoms of VTE. Prophylaxis may also be considered in this patient population.

Several risk factors that were significant on bivariate analysis (increased age; increased ASA class; history of diabetes, pulmonary disease, hypertension) were not significant in the final multivariate model. This finding suggests covariance between these factors and those that were significant in the final multivariate model. In particular, age and increased overall comorbidity (represented by increased ASA class) were not significant in our multivariate model—contrary to findings of other studies.^8-10 It is possible that history of heart disease alone was responsible for the association between overall comorbidity and VTE in those studies. In the present study, separating and controlling for individual comorbidities could have allowed this association to be more precisely characterized.

The characteristics of the ACS-NSQIP database limited our study in several ways. First, although ACS-NSQIP makes significant efforts to collect as many patient variables as possible, some information is not captured. Data about additional factors that may affect VTE risk (eg, history of previous VTE, hypercoagulable state, history of malignancy other than disseminated cancer, tourniquet time, patient position in operating room) were not available. Second, data are collected only on those postoperative adverse events that occur within 30 days after surgery; data on VTEs that occur later are not captured. However, it has been shown that the majority of VTEs occur within the first 30 days after lower extremity trauma and surgery,^21,22 so this follow-up interval was deemed adequate for capture of VTE data. Third, the database does not include information on the prophylactic regimens used for these patients—which may have weakened the associations between predictor variables and VTE risk and led to an underestimated effect size. VTE incidence, as well as the odds of developing a VTE with one of the identified risk factors, may actually be higher than reported in this study.

Conclusion

VTEs are serious complications that can occur after ORIF of ankle fractures. In this study, the overall incidence of VTE after ankle fracture ORIF was 0.8%. Although the American Orthopaedic Foot and Ankle Society and the American College of Chest Physicians do not recommend routine screening or prophylaxis for VTE in patients with ankle fractures,^1,5 the results of this study showed there may be a benefit in emphasizing VTE prophylaxis after ankle fracture ORIF in patients with obesity, history of heart disease, or dependent functional status. At minimum, these patients should be more carefully monitored for development of VTEs.

Venous thromboembolic events (VTEs), encompassing both deep vein thrombosis (DVT) and pulmonary embolism (PE), are potentially fatal events that can occur after orthopedic surgery.¹ In patients who do not receive prophylaxis, VTE incidence can be as high as 70% for total hip arthroplasty,² 26% for hip fracture,³ and 5% for ankle fracture.⁴ Based on the relatively low incidence of VTE after ankle fractures and insufficient evidence for VTE prophylaxis in this population, the American Orthopaedic Foot and Ankle Society and the American College of Chest Physicians do not recommend routine screening or prophylaxis for VTE in patients with ankle fractures.^1,5 Nevertheless, certain patients may be at increased risk for VTE after open reduction and internal fixation (ORIF) of an ankle fracture. In such cases, further consideration for prophylaxis may be warranted.

Other studies of VTEs have identified general risk factors of increased age, obesity, prior thromboembolic disease, oral contraceptive use, multitrauma, varicose veins, and prolonged immobilization, among others.^1,6,7 In orthopedics, most of this research comes from total joint arthroplasty and hip fracture studies. However, there is relatively limited data for ankle fracture. The best studies directly addressing VTE after ORIF of ankle fractures have had important limitations, including missing patient data and suboptimal capture of VTE occurrences,^8-10 possibly leading to underestimates of the incidence of VTEs.

Given the limited data available, we conducted a retrospective national-cohort study to determine the incidence of and independent risk factors for VTEs after ankle fracture ORIF. If patients who are at higher risk for VTE can be identified, they can and should be carefully monitored and be considered for VTE prophylaxis. This information is needed for patient counseling and clinical decision-making.

Materials and Methods

This retrospective study used the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database, which captures data from more than 370 participating US hospitals.¹¹ In ACS-NSQIP, 150 patient variables are collected from operative reports, medical records, and patient interviews by trained clinical reviewers.^11,12 Patients are identified prospectively and randomly sampled at participating hospitals. Routine auditing is performed to ensure high-quality data. Clinical data are collected for the entire 30-day postoperative period, regardless of discharge status during this time.

Patients who underwent ankle fracture ORIF between 2005 and 2012 were identified in the ACS-NSQIP database. They were initially selected by the postoperative diagnosis of ankle fracture (International Classification of Diseases, Ninth Revision codes 824.0-824.9). Of these patients, only those with primary Current Procedural Terminology codes 27766 (ORIF of medial malleolus fracture), 27769 (ORIF of posterior malleolus fracture), 27792 (ORIF of lateral malleolus fracture), 27814 (ORIF of bimalleollar fracture), and 27822/27823 (ORIF of trimalleollar fracture) were included in the analysis. Patients with incomplete perioperative data were excluded, leaving 4412 patients (out of the initial 4785) for analysis.

Patient characteristics, including sex, age, height, weight, and history of smoking, were collected from the ACS-NSQIP database. Body mass index (BMI) was calculated from each patient’s height and weight. Age was divided into approximately 20-year increments, beginning with age 18 years, in order to compare younger, middle-aged, and elderly groups of patients with ankle fractures. BMI was divided into categories based on the World Health Organization definitions of obesity: under 25 kg/m² (normal weight), 25 to 30 kg/m² (overweight), 30 to 35 kg/m² (class I obesity), and 35 kg/m² or over (class II and class III obesity).¹³

Information about medical comorbidities is also available in the ACS-NSQIP database. History of pulmonary disease was defined as a history of dyspnea, severe chronic obstructive pulmonary disease, ventilator-assisted respiration within 48 hours before surgery, or current pneumonia. History of heart disease was defined as a history of congestive heart failure (CHF) or angina within 1 month before admission, myocardial infarction within 6 months before admission, cardiac surgery, or percutaneous coronary intervention. American Society of Anesthesiologists (ASA) classes 3 and above signify severe systemic disease. Steroid use was defined as requiring regular administration of corticosteroid medications within 1 month before surgery. Disseminated cancer was defined as a malignancy that has spread to 1 or more sites besides the primary site.

Functional status was defined as the ability to perform activities of daily living (ADLs) within 30 days before surgery. Best functional status during this period was recorded. ACS-NSQIP defines ADLs as the “activities usually performed in the course of a normal day in a person’s life,” including bathing, feeding, dressing, toileting, and mobility. An independent patient does not require assistance for any ADLs; a partially dependent patient requires assistance for some ADLs; and a totally dependent patient requires assistance in all ADLs. Partially and totally dependent patients were grouped for analysis. Anesthesia type was separated into general and nongeneral, which includes monitored anesthesia care, spinal anesthesia, and regional anesthesia.

ACS-NSQIP also records the occurrence of multiple events up to 30 days after surgery. For our study, VTE was defined as the occurrence of a DVT or a PE during this period. ACS-NSQIP defines DVT as a new blood clot or thrombus identified within a vein—with confirmation by duplex ultrasonography, venogram, or computed tomography (CT)—that required therapy (anticoagulation, placement of vena cava filter, and/or clipping of vena cava). PE is recorded if ventilation/perfusion (VQ) scan, CT examination, transesophageal echocardiogram, pulmonary arteriogram, CT angiogram, or any other definitive modality is positive.

Statistical analyses were performed with Stata Version 11.2 (StataCorp). Demographic and comorbidity variables were tested for association with occurrence of VTE using bivariate and multivariate logistic regression.

Final multivariate models were constructed with a backward stepwise process that initially included all potential variables and sequentially excluded variables with the highest P value until only those with P < .200 remained. Variables with .050 < P < .200 were left in the model to control for potential confounding but are not considered significantly associated with the outcome. Statistical significance was established at a 2-sided α of 0.050 (P < .050). The fitness of the final logistic regression model was assessed with the C statistic and the Hosmer-Lemeshow goodness-of-fit test.

Results

For the 4412 ankle fracture patients who met the inclusion criteria, mean (SD) age was 50.9 (18.2) years, and mean (SD) BMI was 30.4 (7.6) kg/m². The cohort was 40.4% male. Surgery was performed on 235 patients (5.3%) with medial malleolus fracture, 1143 patients (25.9%) with lateral malleolus fracture, 1705 patients (38.6%) with bimalleollar fracture, and 1329 patients (30.1%) with trimalleollar fracture. Table 1 summarizes the patient characteristics.

Of the 33 patients (0.8%) with a VTE recorded within the first 30 postoperative days, 16 (0.4% of all patients) had a DVT recorded, 14 (0.3% of all patients) had a PE recorded, and 3 (0.1% of all patients) had both a DVT and a PE recorded. In 13 (39.4%) of the 33 patients with a VTE, the event occurred after discharge. VTEs were reported a mean (SD) of 11.5 (9.6) days after surgery. No patient in this study died of VTE.

Bivariate logistic regressions were performed to test the association of each patient variable with the occurrence of a VTE. Results are listed in Table 2. The bivariate analyses revealed significant associations between VTE after ankle fracture ORIF and the patient variables of age 60 years or older (odds ratio [OR], 2.40; 95% confidence interval [CI], 1.01-5.72), class I obesity (BMI, 30-35 kg/m²: OR, 5.15, 95% CI, 1.14-23.28), class II and class III obesity (BMI, ≥35 kg/m²: OR, 6.33, 95% CI, 1.41-28.38), ASA classes 3 and 4 (OR, 3.05; 95% CI, 1.53-6.08), history of heart disease (OR, 5.10; 95% CI, 2.08-12.49), history of hypertension (OR, 2.81; 95% CI, 1.39-5.66), and dependent functional status (OR, 3.39; 95% CI, 1.52-7.56).

Multivariate logistic regression was used to control for potential confounding variables and determine which factors were independently associated with VTEs. Results of this analysis are listed in Table 2 as well. The multivariate analysis revealed that the patient variables of class I obesity (BMI, 30-35 kg/m²: OR, 4.77; 95% CI, 1.05-21.72; P = .044), class II and class III obesity (BMI, ≥35 kg/m²: OR, 4.71; 95% CI, 1.03-21.68; P = .046), history of heart disease (OR, 3.28; 95% CI, 1.20-8.97; P = .020), and dependent functional status (OR, 2.59; 95% CI, 1.11-6.04; P = .028) were independently associated with an increased rate of VTEs. Of note, anesthesia type was not significantly associated with occurrence of VTE on bivariate or multivariate analysis.

The C statistic of the final multivariate model was 0.76, indicating very good distinguishing ability. The Hosmer-Lemeshow goodness-of-fit test showed no evidence of lack of fit.

Discussion

Citing the lack of conclusive evidence and the low incidence of VTE after ankle fracture surgery, current recommendations are to avoid routine VTE prophylaxis in the postoperative management of patients who undergo this surgery.^1,5 However, it is important to identify patients who are at increased risk, as some may benefit from VTE prophylaxis. In the present study, we used the large, high-quality ACS-NSQIP database collecting information from multiple US hospitals to examine risk factors for VTE after ankle fracture ORIF. We identified 4412 patients who underwent ankle fracture ORIF between 2005 and 2012, and found an overall VTE incidence of 0.8%. Multivariate analysis identified obesity, history of heart disease, and dependent functional status as independent risk factors for VTE after ankle fracture ORIF.

This study’s 0.8% incidence of VTE after ankle fracture ORIF is consistent with the range (0.29%-5%) reported in other ankle fracture studies.^4,8-10,14-18 We found that VTEs occurred a mean of about 11 days after surgery, and no patient died of VTE.

Obesity (BMI, ≥30 kg/m²) had the strongest association with VTEs in this study. Obesity, which is a growing public health concern, can make postoperative care and mobilization more difficult.¹⁹ Obesity has previously been associated with VTEs after ankle fractures, and BMI of over 25 kg/m² is one of the Caprini criteria for thrombosis risk factor assessment.^6,10 In our study, however, BMI of 25 to 30 kg/m² was not associated with an increased VTE rate, indicating that moderately overweight patients may not be at significantly higher risk for VTE (compared with patients with normal BMI) and may not need VTE prophylaxis. VTE prophylaxis after ankle fracture surgery may be considered in patients with BMI over 30 kg/m².

History of heart disease was also associated with VTEs in this study. Patients with a history of heart disease were at 3 times the risk for VTE within 30 days of ankle fracture surgery. This association is also consistent with the Caprini criteria, which include acute myocardial infarction and CHF as risk factors for venous thrombosis.⁶ Other studies have found associations between CHF and VTE and between cardiovascular risk factors and VTE.^7,20 The association between cardiovascular disease and VTE may derive from the decreased venous flow rate associated with CHF or an overall vascular disease state. These patients may benefit from heightened surveillance and postoperative prophylaxis for VTE.

Dependent functional status was the final risk factor found to be associated with VTE after ankle fracture ORIF. This association likely derives from an inability to mobilize independently, leading to increased venous stasis. Immobilization has been previously associated with increased risk for VTE after ankle surgery.^7,14,16,20 Caretakers should be aware of this increased risk during the postoperative period and diligently monitor these patients for signs and symptoms of VTE. Prophylaxis may also be considered in this patient population.

Several risk factors that were significant on bivariate analysis (increased age; increased ASA class; history of diabetes, pulmonary disease, hypertension) were not significant in the final multivariate model. This finding suggests covariance between these factors and those that were significant in the final multivariate model. In particular, age and increased overall comorbidity (represented by increased ASA class) were not significant in our multivariate model—contrary to findings of other studies.^8-10 It is possible that history of heart disease alone was responsible for the association between overall comorbidity and VTE in those studies. In the present study, separating and controlling for individual comorbidities could have allowed this association to be more precisely characterized.

The characteristics of the ACS-NSQIP database limited our study in several ways. First, although ACS-NSQIP makes significant efforts to collect as many patient variables as possible, some information is not captured. Data about additional factors that may affect VTE risk (eg, history of previous VTE, hypercoagulable state, history of malignancy other than disseminated cancer, tourniquet time, patient position in operating room) were not available. Second, data are collected only on those postoperative adverse events that occur within 30 days after surgery; data on VTEs that occur later are not captured. However, it has been shown that the majority of VTEs occur within the first 30 days after lower extremity trauma and surgery,^21,22 so this follow-up interval was deemed adequate for capture of VTE data. Third, the database does not include information on the prophylactic regimens used for these patients—which may have weakened the associations between predictor variables and VTE risk and led to an underestimated effect size. VTE incidence, as well as the odds of developing a VTE with one of the identified risk factors, may actually be higher than reported in this study.

Conclusion

VTEs are serious complications that can occur after ORIF of ankle fractures. In this study, the overall incidence of VTE after ankle fracture ORIF was 0.8%. Although the American Orthopaedic Foot and Ankle Society and the American College of Chest Physicians do not recommend routine screening or prophylaxis for VTE in patients with ankle fractures,^1,5 the results of this study showed there may be a benefit in emphasizing VTE prophylaxis after ankle fracture ORIF in patients with obesity, history of heart disease, or dependent functional status. At minimum, these patients should be more carefully monitored for development of VTEs.

Venous thromboembolic events (VTEs), encompassing both deep vein thrombosis (DVT) and pulmonary embolism (PE), are potentially fatal events that can occur after orthopedic surgery.¹ In patients who do not receive prophylaxis, VTE incidence can be as high as 70% for total hip arthroplasty,² 26% for hip fracture,³ and 5% for ankle fracture.⁴ Based on the relatively low incidence of VTE after ankle fractures and insufficient evidence for VTE prophylaxis in this population, the American Orthopaedic Foot and Ankle Society and the American College of Chest Physicians do not recommend routine screening or prophylaxis for VTE in patients with ankle fractures.^1,5 Nevertheless, certain patients may be at increased risk for VTE after open reduction and internal fixation (ORIF) of an ankle fracture. In such cases, further consideration for prophylaxis may be warranted.

Other studies of VTEs have identified general risk factors of increased age, obesity, prior thromboembolic disease, oral contraceptive use, multitrauma, varicose veins, and prolonged immobilization, among others.^1,6,7 In orthopedics, most of this research comes from total joint arthroplasty and hip fracture studies. However, there is relatively limited data for ankle fracture. The best studies directly addressing VTE after ORIF of ankle fractures have had important limitations, including missing patient data and suboptimal capture of VTE occurrences,^8-10 possibly leading to underestimates of the incidence of VTEs.

Given the limited data available, we conducted a retrospective national-cohort study to determine the incidence of and independent risk factors for VTEs after ankle fracture ORIF. If patients who are at higher risk for VTE can be identified, they can and should be carefully monitored and be considered for VTE prophylaxis. This information is needed for patient counseling and clinical decision-making.

Materials and Methods

This retrospective study used the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database, which captures data from more than 370 participating US hospitals.¹¹ In ACS-NSQIP, 150 patient variables are collected from operative reports, medical records, and patient interviews by trained clinical reviewers.^11,12 Patients are identified prospectively and randomly sampled at participating hospitals. Routine auditing is performed to ensure high-quality data. Clinical data are collected for the entire 30-day postoperative period, regardless of discharge status during this time.

Patients who underwent ankle fracture ORIF between 2005 and 2012 were identified in the ACS-NSQIP database. They were initially selected by the postoperative diagnosis of ankle fracture (International Classification of Diseases, Ninth Revision codes 824.0-824.9). Of these patients, only those with primary Current Procedural Terminology codes 27766 (ORIF of medial malleolus fracture), 27769 (ORIF of posterior malleolus fracture), 27792 (ORIF of lateral malleolus fracture), 27814 (ORIF of bimalleollar fracture), and 27822/27823 (ORIF of trimalleollar fracture) were included in the analysis. Patients with incomplete perioperative data were excluded, leaving 4412 patients (out of the initial 4785) for analysis.

Patient characteristics, including sex, age, height, weight, and history of smoking, were collected from the ACS-NSQIP database. Body mass index (BMI) was calculated from each patient’s height and weight. Age was divided into approximately 20-year increments, beginning with age 18 years, in order to compare younger, middle-aged, and elderly groups of patients with ankle fractures. BMI was divided into categories based on the World Health Organization definitions of obesity: under 25 kg/m² (normal weight), 25 to 30 kg/m² (overweight), 30 to 35 kg/m² (class I obesity), and 35 kg/m² or over (class II and class III obesity).¹³

Information about medical comorbidities is also available in the ACS-NSQIP database. History of pulmonary disease was defined as a history of dyspnea, severe chronic obstructive pulmonary disease, ventilator-assisted respiration within 48 hours before surgery, or current pneumonia. History of heart disease was defined as a history of congestive heart failure (CHF) or angina within 1 month before admission, myocardial infarction within 6 months before admission, cardiac surgery, or percutaneous coronary intervention. American Society of Anesthesiologists (ASA) classes 3 and above signify severe systemic disease. Steroid use was defined as requiring regular administration of corticosteroid medications within 1 month before surgery. Disseminated cancer was defined as a malignancy that has spread to 1 or more sites besides the primary site.

Functional status was defined as the ability to perform activities of daily living (ADLs) within 30 days before surgery. Best functional status during this period was recorded. ACS-NSQIP defines ADLs as the “activities usually performed in the course of a normal day in a person’s life,” including bathing, feeding, dressing, toileting, and mobility. An independent patient does not require assistance for any ADLs; a partially dependent patient requires assistance for some ADLs; and a totally dependent patient requires assistance in all ADLs. Partially and totally dependent patients were grouped for analysis. Anesthesia type was separated into general and nongeneral, which includes monitored anesthesia care, spinal anesthesia, and regional anesthesia.

ACS-NSQIP also records the occurrence of multiple events up to 30 days after surgery. For our study, VTE was defined as the occurrence of a DVT or a PE during this period. ACS-NSQIP defines DVT as a new blood clot or thrombus identified within a vein—with confirmation by duplex ultrasonography, venogram, or computed tomography (CT)—that required therapy (anticoagulation, placement of vena cava filter, and/or clipping of vena cava). PE is recorded if ventilation/perfusion (VQ) scan, CT examination, transesophageal echocardiogram, pulmonary arteriogram, CT angiogram, or any other definitive modality is positive.

Statistical analyses were performed with Stata Version 11.2 (StataCorp). Demographic and comorbidity variables were tested for association with occurrence of VTE using bivariate and multivariate logistic regression.

Final multivariate models were constructed with a backward stepwise process that initially included all potential variables and sequentially excluded variables with the highest P value until only those with P < .200 remained. Variables with .050 < P < .200 were left in the model to control for potential confounding but are not considered significantly associated with the outcome. Statistical significance was established at a 2-sided α of 0.050 (P < .050). The fitness of the final logistic regression model was assessed with the C statistic and the Hosmer-Lemeshow goodness-of-fit test.

Results

For the 4412 ankle fracture patients who met the inclusion criteria, mean (SD) age was 50.9 (18.2) years, and mean (SD) BMI was 30.4 (7.6) kg/m². The cohort was 40.4% male. Surgery was performed on 235 patients (5.3%) with medial malleolus fracture, 1143 patients (25.9%) with lateral malleolus fracture, 1705 patients (38.6%) with bimalleollar fracture, and 1329 patients (30.1%) with trimalleollar fracture. Table 1 summarizes the patient characteristics.

Of the 33 patients (0.8%) with a VTE recorded within the first 30 postoperative days, 16 (0.4% of all patients) had a DVT recorded, 14 (0.3% of all patients) had a PE recorded, and 3 (0.1% of all patients) had both a DVT and a PE recorded. In 13 (39.4%) of the 33 patients with a VTE, the event occurred after discharge. VTEs were reported a mean (SD) of 11.5 (9.6) days after surgery. No patient in this study died of VTE.

Bivariate logistic regressions were performed to test the association of each patient variable with the occurrence of a VTE. Results are listed in Table 2. The bivariate analyses revealed significant associations between VTE after ankle fracture ORIF and the patient variables of age 60 years or older (odds ratio [OR], 2.40; 95% confidence interval [CI], 1.01-5.72), class I obesity (BMI, 30-35 kg/m²: OR, 5.15, 95% CI, 1.14-23.28), class II and class III obesity (BMI, ≥35 kg/m²: OR, 6.33, 95% CI, 1.41-28.38), ASA classes 3 and 4 (OR, 3.05; 95% CI, 1.53-6.08), history of heart disease (OR, 5.10; 95% CI, 2.08-12.49), history of hypertension (OR, 2.81; 95% CI, 1.39-5.66), and dependent functional status (OR, 3.39; 95% CI, 1.52-7.56).

Multivariate logistic regression was used to control for potential confounding variables and determine which factors were independently associated with VTEs. Results of this analysis are listed in Table 2 as well. The multivariate analysis revealed that the patient variables of class I obesity (BMI, 30-35 kg/m²: OR, 4.77; 95% CI, 1.05-21.72; P = .044), class II and class III obesity (BMI, ≥35 kg/m²: OR, 4.71; 95% CI, 1.03-21.68; P = .046), history of heart disease (OR, 3.28; 95% CI, 1.20-8.97; P = .020), and dependent functional status (OR, 2.59; 95% CI, 1.11-6.04; P = .028) were independently associated with an increased rate of VTEs. Of note, anesthesia type was not significantly associated with occurrence of VTE on bivariate or multivariate analysis.

The C statistic of the final multivariate model was 0.76, indicating very good distinguishing ability. The Hosmer-Lemeshow goodness-of-fit test showed no evidence of lack of fit.

Discussion

Citing the lack of conclusive evidence and the low incidence of VTE after ankle fracture surgery, current recommendations are to avoid routine VTE prophylaxis in the postoperative management of patients who undergo this surgery.^1,5 However, it is important to identify patients who are at increased risk, as some may benefit from VTE prophylaxis. In the present study, we used the large, high-quality ACS-NSQIP database collecting information from multiple US hospitals to examine risk factors for VTE after ankle fracture ORIF. We identified 4412 patients who underwent ankle fracture ORIF between 2005 and 2012, and found an overall VTE incidence of 0.8%. Multivariate analysis identified obesity, history of heart disease, and dependent functional status as independent risk factors for VTE after ankle fracture ORIF.

This study’s 0.8% incidence of VTE after ankle fracture ORIF is consistent with the range (0.29%-5%) reported in other ankle fracture studies.^4,8-10,14-18 We found that VTEs occurred a mean of about 11 days after surgery, and no patient died of VTE.

Obesity (BMI, ≥30 kg/m²) had the strongest association with VTEs in this study. Obesity, which is a growing public health concern, can make postoperative care and mobilization more difficult.¹⁹ Obesity has previously been associated with VTEs after ankle fractures, and BMI of over 25 kg/m² is one of the Caprini criteria for thrombosis risk factor assessment.^6,10 In our study, however, BMI of 25 to 30 kg/m² was not associated with an increased VTE rate, indicating that moderately overweight patients may not be at significantly higher risk for VTE (compared with patients with normal BMI) and may not need VTE prophylaxis. VTE prophylaxis after ankle fracture surgery may be considered in patients with BMI over 30 kg/m².

History of heart disease was also associated with VTEs in this study. Patients with a history of heart disease were at 3 times the risk for VTE within 30 days of ankle fracture surgery. This association is also consistent with the Caprini criteria, which include acute myocardial infarction and CHF as risk factors for venous thrombosis.⁶ Other studies have found associations between CHF and VTE and between cardiovascular risk factors and VTE.^7,20 The association between cardiovascular disease and VTE may derive from the decreased venous flow rate associated with CHF or an overall vascular disease state. These patients may benefit from heightened surveillance and postoperative prophylaxis for VTE.

Dependent functional status was the final risk factor found to be associated with VTE after ankle fracture ORIF. This association likely derives from an inability to mobilize independently, leading to increased venous stasis. Immobilization has been previously associated with increased risk for VTE after ankle surgery.^7,14,16,20 Caretakers should be aware of this increased risk during the postoperative period and diligently monitor these patients for signs and symptoms of VTE. Prophylaxis may also be considered in this patient population.

Several risk factors that were significant on bivariate analysis (increased age; increased ASA class; history of diabetes, pulmonary disease, hypertension) were not significant in the final multivariate model. This finding suggests covariance between these factors and those that were significant in the final multivariate model. In particular, age and increased overall comorbidity (represented by increased ASA class) were not significant in our multivariate model—contrary to findings of other studies.^8-10 It is possible that history of heart disease alone was responsible for the association between overall comorbidity and VTE in those studies. In the present study, separating and controlling for individual comorbidities could have allowed this association to be more precisely characterized.

The characteristics of the ACS-NSQIP database limited our study in several ways. First, although ACS-NSQIP makes significant efforts to collect as many patient variables as possible, some information is not captured. Data about additional factors that may affect VTE risk (eg, history of previous VTE, hypercoagulable state, history of malignancy other than disseminated cancer, tourniquet time, patient position in operating room) were not available. Second, data are collected only on those postoperative adverse events that occur within 30 days after surgery; data on VTEs that occur later are not captured. However, it has been shown that the majority of VTEs occur within the first 30 days after lower extremity trauma and surgery,^21,22 so this follow-up interval was deemed adequate for capture of VTE data. Third, the database does not include information on the prophylactic regimens used for these patients—which may have weakened the associations between predictor variables and VTE risk and led to an underestimated effect size. VTE incidence, as well as the odds of developing a VTE with one of the identified risk factors, may actually be higher than reported in this study.

Conclusion

VTEs are serious complications that can occur after ORIF of ankle fractures. In this study, the overall incidence of VTE after ankle fracture ORIF was 0.8%. Although the American Orthopaedic Foot and Ankle Society and the American College of Chest Physicians do not recommend routine screening or prophylaxis for VTE in patients with ankle fractures,^1,5 the results of this study showed there may be a benefit in emphasizing VTE prophylaxis after ankle fracture ORIF in patients with obesity, history of heart disease, or dependent functional status. At minimum, these patients should be more carefully monitored for development of VTEs.

Patients with knee osteoarthritis (OA) who have poor sleep habits display greater central sensitization of pain, according to a study published online ahead of print June 4 in Arthritis Care & Research. Study findings also showed that OA patients who catastrophize had increased central sensitization that was associated with greater pain.

“Our study is the largest and most comprehensive examination of the relationship between sleep disturbance, catastrophizing, and central sensitization in knee OA,” stated lead author Claudia Campbell, PhD, an Associate Professor of Psychiatry and Behavioral Sciences at Johns Hopkins University School of Medicine in Baltimore.

The case-controlled study included 208 participants who were categorized according to 4 groups: patients who have OA and insomnia, patients who have OA and normal sleep habits, healthy controls with insomnia, and healthy controls without a pain syndrome and normal sleep. In all, 72% of the study’s participants were female.

Participants completed multimodal sleep assessments (eg, questionnaire, diary, actigraphy, and polysmnography) and extensive evaluation of pain using clinical measures and quantitative sensory testing to evaluate associations between central sensitization, catastrophizing, and insomnia.

Results showed that the participants with knee OA and insomnia had the greatest amount of central sensitization compared with controls. The team found patients with poor sleep and high catastrophizing scores reported increased levels of central sensitization. In turn, central sensitization was significantly associated with increased clinical pain.

“While no causal processes may be determined from this study, our data suggest that those with low sleep efficiency and higher catastrophizing have the greatest central sensitization. Understanding the intricate relationship between sleep, central sensitization, and catastrophizing has important clinical implications for treating those with chronic pain conditions such as knee OA,” Dr. Campbell stated.

Patients with knee osteoarthritis (OA) who have poor sleep habits display greater central sensitization of pain, according to a study published online ahead of print June 4 in Arthritis Care & Research. Study findings also showed that OA patients who catastrophize had increased central sensitization that was associated with greater pain.

“Our study is the largest and most comprehensive examination of the relationship between sleep disturbance, catastrophizing, and central sensitization in knee OA,” stated lead author Claudia Campbell, PhD, an Associate Professor of Psychiatry and Behavioral Sciences at Johns Hopkins University School of Medicine in Baltimore.

The case-controlled study included 208 participants who were categorized according to 4 groups: patients who have OA and insomnia, patients who have OA and normal sleep habits, healthy controls with insomnia, and healthy controls without a pain syndrome and normal sleep. In all, 72% of the study’s participants were female.

Participants completed multimodal sleep assessments (eg, questionnaire, diary, actigraphy, and polysmnography) and extensive evaluation of pain using clinical measures and quantitative sensory testing to evaluate associations between central sensitization, catastrophizing, and insomnia.

Results showed that the participants with knee OA and insomnia had the greatest amount of central sensitization compared with controls. The team found patients with poor sleep and high catastrophizing scores reported increased levels of central sensitization. In turn, central sensitization was significantly associated with increased clinical pain.

“While no causal processes may be determined from this study, our data suggest that those with low sleep efficiency and higher catastrophizing have the greatest central sensitization. Understanding the intricate relationship between sleep, central sensitization, and catastrophizing has important clinical implications for treating those with chronic pain conditions such as knee OA,” Dr. Campbell stated.

Patients with knee osteoarthritis (OA) who have poor sleep habits display greater central sensitization of pain, according to a study published online ahead of print June 4 in Arthritis Care & Research. Study findings also showed that OA patients who catastrophize had increased central sensitization that was associated with greater pain.

“Our study is the largest and most comprehensive examination of the relationship between sleep disturbance, catastrophizing, and central sensitization in knee OA,” stated lead author Claudia Campbell, PhD, an Associate Professor of Psychiatry and Behavioral Sciences at Johns Hopkins University School of Medicine in Baltimore.

The case-controlled study included 208 participants who were categorized according to 4 groups: patients who have OA and insomnia, patients who have OA and normal sleep habits, healthy controls with insomnia, and healthy controls without a pain syndrome and normal sleep. In all, 72% of the study’s participants were female.

Participants completed multimodal sleep assessments (eg, questionnaire, diary, actigraphy, and polysmnography) and extensive evaluation of pain using clinical measures and quantitative sensory testing to evaluate associations between central sensitization, catastrophizing, and insomnia.

Results showed that the participants with knee OA and insomnia had the greatest amount of central sensitization compared with controls. The team found patients with poor sleep and high catastrophizing scores reported increased levels of central sensitization. In turn, central sensitization was significantly associated with increased clinical pain.

“While no causal processes may be determined from this study, our data suggest that those with low sleep efficiency and higher catastrophizing have the greatest central sensitization. Understanding the intricate relationship between sleep, central sensitization, and catastrophizing has important clinical implications for treating those with chronic pain conditions such as knee OA,” Dr. Campbell stated.