User login
US National Practice Patterns in Ambulatory Operative Management of Lateral Epicondylitis
First described by Runge1 in 1873 and later termed lawn-tennis arm by Major2 in 1883, lateral epicondylitis is a common cause of elbow pain, affecting 1% to 3% of the general population each year.3,4 Given that prevalence estimates are up to 15% among workers in repetitive hand task industries,5-7 symptoms of lateral epicondylitis are thought to be related to recurring wrist extension and alternating forearm pronation and supination.8 Between 80% and 90% of patients with lateral epicondylitis experience symptomatic improvement with conservative therapy,9-11 including rest and use of nonsteroidal anti-inflammatory medications,12 physical therapy,13,14 corticosteroid injections,10,15,16 orthoses,17,18 and shock wave therapy.19 However, between 4% and 11% of patients with newly diagnosed lateral epicondylitis do not respond to prolonged (6- to 12-month) conservative treatment and then require operative intervention,11,20,21 with some referral practices reporting rates as high as 25%.22
Traditionally, operative management of lateral epicondylitis involved open débridement of the extensor carpi radialis brevis (ECRB).11,20 More recently, the spectrum of operations for lateral epicondylitis has expanded to include procedures that repair the extensor origin after débridement of the torn tendon and angiofibroblastic dysplasia; procedures that use fasciotomy or direct release of the extensor origin from the epicondyle to relieve tension on the common extensor; procedures directed at the radial or posterior interosseous nerve; and procedures that use arthroscopic techniques to divide the orbicular ligament, reshape the radial head, or release the extensor origin.23 There has been debate about the value of repairing the ECRB, lengthening the ECRB, simultaneously decompressing the radial nerve or resecting epicondylar bone, and performing the procedures percutaneously, endoscopically, or arthroscopically.24-28 Despite multiple studies of the outcomes of these procedures,11,29-31 little is known regarding US national trends for operative treatment of lateral epicondylitis. Understanding national practice patterns and disease burden is essential to allocation of limited health care resources.
We conducted a study to determine US national trends in use of ambulatory surgery for lateral epicondylitis. We focused on age, sex, surgical setting, anesthetic type, and payment method.
Methods
As the National Survey of Ambulatory Surgery32 (NSAS) is an administrative dataset in which all data are deidentified and available for public use, this study was exempt from requiring institutional review board approval.
NSAS data were used to analyze trends in treatment of lateral epicondylitis between 1994 and 2006. NSAS was undertaken by the National Center for Health Statistics (NCHS) of the Centers for Disease Control and Prevention (CDC) to obtain information about the use of ambulatory surgery in the United States. Since the early 1980s, ambulatory surgery has increased in the United States because of advances in medical technology and cost-containment initiatives.33 The number of procedures being performed in ambulatory surgery centers increased from 31.5 million in 1996 to 53.3 million in 2006.34 Funded by the CDC, NSAS is a national study that involves both hospital-based and freestanding ambulatory surgery centers and provides the most recent and comprehensive overview of ambulatory surgery in the United States.35 Because of budgetary limitations, 2006 was the last year in which data for NSAS were collected. Data for NSAS come from Medicare-participating, noninstitutional hospitals (excluding military hospitals, federal facilities, and Veteran Affairs hospitals) in all 50 states and the District of Columbia with a minimum of 6 beds staffed for patient use. NSAS used only short-stay hospitals (hospitals with an average length of stay for all patients of less than 30 days) or hospitals that had a specialty of general (medical or surgical) or children’s general. NSAS was conducted in 1994, 1996, and 2006 with medical information recorded on patient abstracts coded by contract staff. NSAS selected a sample of ambulatory surgery visits using a systematic random sampling procedure, and selection of visits within each facility was done separately for each location where ambulatory surgery was performed. In 1994, 751 facilities were sampled, and 88% of hospitals responded. In 1996, 750 facilities were sampled, and 91% of hospitals responded. In 2006, 696 facilities were sampled, and 75% responded. The surveys used International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) codes36 to classify medical diagnoses and procedures. To produce an unbiased national estimate, NCHS used multistage estimate procedures, including inflation by reciprocals of the probabilities of sample selection, population-weighting ratio adjustments, and adjustment for no response.37
Demographic and medical information was obtained for people with an ICD-9-CM diagnosis code of lateral epicondylitis (726.32), using previously described techniques.38 Data were then recorded for age, sex, facility type, insurance type, anesthesia type, diagnoses, and procedures.
Descriptive statistics consisted of means and standard deviations for continuous variables and frequency and percentages for discrete variables. Because NSAS data were collected on the basis of a probabilistic sample scheme, they were analyzed using a sampling weighting method. Sampling weights (inverse of selection probability) provided by the CDC were used to account for unequal sampling probabilities and to produce estimates for all visits in the United States. A Taylor linearization model provided by the CDC estimates was used to calculate standard error and confidence intervals (CIs) of the data. Standard error is a measure of sampling variability that occurs by chance because only a sample rather than the entire universe is surveyed. To define population parameters, NCHS chose 95% CIs along with a point estimate. Direct statistical comparison between years cannot be performed because of sampling differences in the database compared between years. The CIs, however, can suggest statistical differences if the data are nonoverlapping. US census data were used to obtain national population estimates for each year of the study (1994, 1996, 2006).39 Rates were presented as number of procedures per 100,000 standard population. For age, a direct adjustment procedure was used, and the US population in 2000 was selected as the standard population. Applying sex-specific rates to the standard population and dividing by the total in the standard population, we calculated sex-adjusted rates for each year. All data were analyzed using SPSS Version 20 software.
Results
A total of 30,311 ambulatory surgical procedures (95% CI, 27,292-33,330) or 10.44 per 100,000 capita were recorded by NSAS for the treatment of lateral epicondylitis in 2006 (Table 1). This represents a large increase in the total number of ambulatory procedures, from 21,852 in 1994 (95% CI, 19,981-23,722; 7.29/100,000) and 20,372 in 1996 (95% CI, 18,660-22,083; 6.73/100,000).
Between 1994 and 2006, the sex-adjusted rate of ambulatory surgery for lateral epicondylitis increased by 85% among females (7.74/100,000 to 14.31/100,000), whereas the rate decreased by 31% among males (8.07/100,000 to 5.59/100,000) (Table 1). The age-adjusted rate of ambulatory surgery for lateral epicondylitis increased among all age groups except the 30–39 years group (Table 2). The largest increase in age-adjusted rates was found for patients older than 50 years (275%) between 1994 and 2006.
During the study period, use of regional anesthesia nearly doubled, from 17% to 30%, whereas use of general anesthesia decreased, from 69% to 57% (Table 3). At all time points, the most common procedure performed for lateral epicondylitis in ambulatory surgery centers was division/release of the joint capsule of the elbow (Table 4). Private insurance remained the most common source of payment for all study years, ranging from 52% to 60% (Table 5). The Figure shows that, between 1994 and 2006, the proportion of surgeries performed in a freestanding ambulatory center increased.
Discussion
In this descriptive epidemiologic study, we used NSAS data to investigate trends in ambulatory surgery for lateral epicondylitis between 1994 and 2006.32 Our results showed that total number of procedures and the population-adjusted rate of procedures for lateral epicondylitis increased during the study period. The largest increase in age-adjusted rates of surgery for lateral epicondylitis was found among patients older than 50 years, whereas the highest age-adjusted rate of ambulatory surgery for lateral epicondylitis was found among patients between ages 40 and 49 years. These findings are similar to those of previous studies, which have shown that most patients with lateral epicondylitis present in the fourth and fifth decades of life.22 Prior reports have suggested that the incidence of lateral epicondylitis in men and women is equal.22 The present study found a change in sex-adjusted rates of ambulatory surgery for lateral epicondylitis between 1994 and 2006. Specifically, in 1994, surgery rates for men and women were similar (8.07/100,000 and 7.74/100,000), but in 2006 the sex-adjusted rate of surgery for lateral epicondylitis was almost 3 times higher for women than for men (14.31/100,000 vs 5.59/100,000).
We also found that the population-adjusted rate of lateral epicondylectomy increased drastically, from 0.4 per 100,000 in 1994 to 3.53 per 100,000 in 2006. Lateral epicondylectomy involves excision of the tip of the lateral epicondyle (typically, 0.5 cm) to produce a cancellous bone surface to which the edges of the débrided extensor tendon can be approximated without tension.23 It is possible that the increased rate of lateral epicondylectomy reflects evidence-based practice changes during the study period,27 though denervation was found more favorable than epicondylectomy in a recent study by Berry and colleagues.40 Future studies should investigate whether rates of epicondylectomy have changed since 2006. In addition, the present study showed a correlation between the introduction of arthroscopic techniques for the treatment of lateral epicondylitis and the period when much research was being conducted on the topic.24,25,28 As arthroscopic techniques improve, their rates are likely to continue to increase.
Our results also showed an increase in procedures performed in freestanding facilities. The rise in ambulatory surgical volume, speculated to result from more procedures being performed in freestanding facilities,34 has been reported with knee and shoulder arthroscopy.41 In addition, though general anesthesia remained the most used technique, our results showed a shift toward peripheral nerve blocks. The increase in regional anesthesia, which has also been noted in joint arthroscopy, is thought to stem from the advent of nerve-localizing technology, such as nerve stimulation and ultrasound guidance.41 Peripheral nerve blocks are favorable on both economic and quality measures, are associated with fewer opioid-related side effects, and overall provide better analgesia in comparison with opioids, highlighting their importance in the ambulatory setting.42
Although large, national databases are well suited to epidemiologic research,43 our study had limitations. As with all databases, NSAS is subject to data entry errors and coding errors.44,45 However, the database administrators corrected for this by using a multistage estimate procedure with weighting adjustments for no response and population-weighting ratio adjustments.35 Another limitation of this study is its lack of clinical detail, as procedure codes are general and do not allow differentiation between specific patients. Because of the retrospective nature of the analysis and the heterogeneity of the data, assessment of specific surgeries for lateral epicondylitis was limited. Although a strength of using NSAS to perform epidemiologic analyses is its large sample size, this also sacrifices specificity in terms of clinical insight. The results of this study may influence investigations to distinguish differences between procedures used in the treatment of lateral epicondylitis. Furthermore, the results of this study are limited to ambulatory surgery practice patterns in the United States between 1996 and 2006. Last, our ability to perform economic analyses was limited, as data on total hospital cost were not recorded by the surveys.
Conclusion
The increase in ambulatory surgery for lateral epicondylitis, demonstrated in this study, emphasizes the importance of national funding for surveys such as NSAS beyond 2006, as utilization trends may have considerable effects on health care policies that influence the quality of patient care.
1. Runge F. Zur genese und behandlung des schreibekramfes. Berl Klin Wochenschr. 1873;10:245.
2. Major HP. Lawn-tennis elbow. Br Med J. 1883;2:557.
3. Allander E. Prevalence, incidence, and remission rates of some common rheumatic diseases or syndromes. Scand J Rheumatol. 1974;3(3):145-153.
4. Verhaar JA. Tennis elbow. Anatomical, epidemiological and therapeutic aspects. Int Orthop. 1994;18(5):263-267.
5. Kurppa K, Viikari-Juntura E, Kuosma E, Huuskonen M, Kivi P. Incidence of tenosynovitis or peritendinitis and epicondylitis in a meat-processing factory. Scand J Work Environ Health. 1991;17(1):32-37.
6. Ranney D, Wells R, Moore A. Upper limb musculoskeletal disorders in highly repetitive industries: precise anatomical physical findings. Ergonomics. 1995;38(7):1408-1423.
7. Haahr JP, Andersen JH. Physical and psychosocial risk factors for lateral epicondylitis: a population based case-referent study. Occup Environ Med. 2003;60(5):322-329.
8. Goldie I. Epicondylitis lateralis humeri (epicondylalgia or tennis elbow). A pathogenetical study. Acta Chir Scand Suppl. 1964;57(suppl 399):1+.
9. Binder AI, Hazleman BL. Lateral humeral epicondylitis—a study of natural history and the effect of conservative therapy. Br J Rheumatol. 1983;22(2):73-76.
10. Smidt N, van der Windt DA, Assendelft WJ, Devillé WL, Korthals-de Bos IB, Bouter LM. Corticosteroid injections, physiotherapy, or a wait-and-see policy for lateral epicondylitis: a randomised controlled trial. Lancet. 2002;359(9307):657-662.
11. Nirschl RP, Pettrone FA. Tennis elbow. The surgical treatment of lateral epicondylitis. J Bone Joint Surg Am. 1979;61(6):832-839.
12. Burnham R, Gregg R, Healy P, Steadward R. The effectiveness of topical diclofenac for lateral epicondylitis. Clin J Sport Med. 1998;8(2):78-81.
13. Martinez-Silvestrini JA, Newcomer KL, Gay RE, Schaefer MP, Kortebein P, Arendt KW. Chronic lateral epicondylitis: comparative effectiveness of a home exercise program including stretching alone versus stretching supplemented with eccentric or concentric strengthening. J Hand Ther. 2005;18(4):411-419.
14. Svernlöv B, Adolfsson L. Non-operative treatment regime including eccentric training for lateral humeral epicondylalgia. Scand J Med Sci Sports. 2001;11(6):328-334.
15. Hay EM, Paterson SM, Lewis M, Hosie G, Croft P. Pragmatic randomised controlled trial of local corticosteroid injection and naproxen for treatment of lateral epicondylitis of elbow in primary care. BMJ. 1999;319(7215):964-968.
16. Lewis M, Hay EM, Paterson SM, Croft P. Local steroid injections for tennis elbow: does the pain get worse before it gets better? Results from a randomized controlled trial. Clin J Pain. 2005;21(4):330-334.
17. Van De Streek MD, Van Der Schans CP, De Greef MH, Postema K. The effect of a forearm/hand splint compared with an elbow band as a treatment for lateral epicondylitis. Prosthet Orthot Int. 2004;28(2):183-189.
18. Struijs PA, Smidt N, Arola H, Dijk vC, Buchbinder R, Assendelft WJ. Orthotic devices for the treatment of tennis elbow. Cochrane Database Syst Rev. 2002;(1):CD001821.
19. Buchbinder R, Green SE, Youd JM, Assendelft WJ, Barnsley L, Smidt N. Shock wave therapy for lateral elbow pain. Cochrane Database Syst Rev. 2005;(4):CD003524.
20. Boyd HB, McLeod AC Jr. Tennis elbow. J Bone Joint Surg Am. 1973;55(6):1183-1187.
21. Coonrad RW, Hooper WR. Tennis elbow: its course, natural history, conservative and surgical management. J Bone Joint Surg Am. 1973;55(6):1177-1182.
22. Calfee RP, Patel A, DaSilva MF, Akelman E. Management of lateral epicondylitis: current concepts. J Am Acad Orthop Surg. 2008;16(1):19-29.
23. Plancher KD, Bishai SK. Open lateral epicondylectomy: a simple technique update for the 21st century. Tech Orthop. 2006;21(4):276-282.
24. Peart RE, Strickler SS, Schweitzer KM Jr. Lateral epicondylitis: a comparative study of open and arthroscopic lateral release. Am J Orthop. 2004;33(11):565-567.
25. Dunkow PD, Jatti M, Muddu BN. A comparison of open and percutaneous techniques in the surgical treatment of tennis elbow. J Bone Joint Surg Br. 2004;86(5):701-704.
26. Rosenberg N, Henderson I. Surgical treatment of resistant lateral epicondylitis. Follow-up study of 19 patients after excision, release and repair of proximal common extensor tendon origin. Arch Orthop Trauma Surg. 2002;122(9-10):514-517.
27. Almquist EE, Necking L, Bach AW. Epicondylar resection with anconeus muscle transfer for chronic lateral epicondylitis. J Hand Surg Am. 1998;23(4):723-731.
28. Smith AM, Castle JA, Ruch DS. Arthroscopic resection of the common extensor origin: anatomic considerations. J Shoulder Elbow Surg. 2003;12(4):375-379.
29. Baker CL Jr, Murphy KP, Gottlob CA, Curd DT. Arthroscopic classification and treatment of lateral epicondylitis: two-year clinical results. J Shoulder Elbow Surg. 2000;9(6):475-482.
30. Owens BD, Murphy KP, Kuklo TR. Arthroscopic release for lateral epicondylitis. Arthroscopy. 2001;17(6):582-587.
31. Mullett H, Sprague M, Brown G, Hausman M. Arthroscopic treatment of lateral epicondylitis: clinical and cadaveric studies. Clin Orthop Relat Res. 2005;(439):123-128.
32. National Survey of Ambulatory Surgery. Centers for Disease Control and Prevention website. http://www.cdc.gov/nchs/nsas/nsas_questionnaires.htm. Published May 4, 2010. Accessed November 10, 2015.
33. Leader S, Moon M. Medicare trends in ambulatory surgery. Health Aff. 1989;8(1):158-170.
34. Cullen KA, Hall MJ, Golosinskiy A. Ambulatory surgery in the United States, 2006. Natl Health Stat Rep. 2009;(11):1-25.
35. Kim S, Bosque J, Meehan JP, Jamali A, Marder R. Increase in outpatient knee arthroscopy in the United States: a comparison of National Surveys of Ambulatory Surgery, 1996 and 2006. J Bone Joint Surg Am. 2011;93(11):994-1000.
36. Centers for Disease Control and Prevention, National Center for Health Statistics. International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM). http://www.cdc.gov/nchs/icd/icd9cm.htm. Updated June 18, 2013. Accessed October 28, 2015.
37. Dennison C, Pokras R. Design and operation of the National Hospital Discharge Survey: 1988 redesign. Vital Health Stat 1. 2000;(39):1-42.
38. Stundner O, Kirksey M, Chiu YL, et al. Demographics and perioperative outcome in patients with depression and anxiety undergoing total joint arthroplasty: a population-based study. Psychosomatics. 2013;54(2):149-157.
39. Population estimates. US Department of Commerce, United States Census Bureau website. http://www.census.gov/popest/index.html. Accessed November 16, 2015.
40. Berry N, Neumeister MW, Russell RC, Dellon AL. Epicondylectomy versus denervation for lateral humeral epicondylitis. Hand. 2011;6(2):174-178.
41. Memtsoudis SG, Kuo C, Ma Y, Edwards A, Mazumdar M, Liguori G. Changes in anesthesia-related factors in ambulatory knee and shoulder surgery: United States 1996–2006. Reg Anesth Pain Med. 2011;36(4):327-331.
42. Richman JM, Liu SS, Courpas G, et al. Does continuous peripheral nerve block provide superior pain control to opioids? A meta-analysis. Anesth Analg. 2006;102(1):248-257.
43. Bohl DD, Basques BA, Golinvaux NS, Baumgaertner MR, Grauer JN. Nationwide Inpatient Sample and National Surgical Quality Improvement Program give different results in hip fracture studies. Clin Orthop Relat Res. 2014;472(6):1672-1680.
44. Gray DT, Hodge DO, Ilstrup DM, Butterfield LC, Baratz KH, Concordance of Medicare data and population-based clinical data on cataract surgery utilization in Olmsted County, Minnesota. Am J Epidemiol. 1997;145(12):1123-1126.
45. Memtsoudis SG. Limitations associated with the analysis of data from administrative databases. Anesthesiology. 2009;111(2):449.
First described by Runge1 in 1873 and later termed lawn-tennis arm by Major2 in 1883, lateral epicondylitis is a common cause of elbow pain, affecting 1% to 3% of the general population each year.3,4 Given that prevalence estimates are up to 15% among workers in repetitive hand task industries,5-7 symptoms of lateral epicondylitis are thought to be related to recurring wrist extension and alternating forearm pronation and supination.8 Between 80% and 90% of patients with lateral epicondylitis experience symptomatic improvement with conservative therapy,9-11 including rest and use of nonsteroidal anti-inflammatory medications,12 physical therapy,13,14 corticosteroid injections,10,15,16 orthoses,17,18 and shock wave therapy.19 However, between 4% and 11% of patients with newly diagnosed lateral epicondylitis do not respond to prolonged (6- to 12-month) conservative treatment and then require operative intervention,11,20,21 with some referral practices reporting rates as high as 25%.22
Traditionally, operative management of lateral epicondylitis involved open débridement of the extensor carpi radialis brevis (ECRB).11,20 More recently, the spectrum of operations for lateral epicondylitis has expanded to include procedures that repair the extensor origin after débridement of the torn tendon and angiofibroblastic dysplasia; procedures that use fasciotomy or direct release of the extensor origin from the epicondyle to relieve tension on the common extensor; procedures directed at the radial or posterior interosseous nerve; and procedures that use arthroscopic techniques to divide the orbicular ligament, reshape the radial head, or release the extensor origin.23 There has been debate about the value of repairing the ECRB, lengthening the ECRB, simultaneously decompressing the radial nerve or resecting epicondylar bone, and performing the procedures percutaneously, endoscopically, or arthroscopically.24-28 Despite multiple studies of the outcomes of these procedures,11,29-31 little is known regarding US national trends for operative treatment of lateral epicondylitis. Understanding national practice patterns and disease burden is essential to allocation of limited health care resources.
We conducted a study to determine US national trends in use of ambulatory surgery for lateral epicondylitis. We focused on age, sex, surgical setting, anesthetic type, and payment method.
Methods
As the National Survey of Ambulatory Surgery32 (NSAS) is an administrative dataset in which all data are deidentified and available for public use, this study was exempt from requiring institutional review board approval.
NSAS data were used to analyze trends in treatment of lateral epicondylitis between 1994 and 2006. NSAS was undertaken by the National Center for Health Statistics (NCHS) of the Centers for Disease Control and Prevention (CDC) to obtain information about the use of ambulatory surgery in the United States. Since the early 1980s, ambulatory surgery has increased in the United States because of advances in medical technology and cost-containment initiatives.33 The number of procedures being performed in ambulatory surgery centers increased from 31.5 million in 1996 to 53.3 million in 2006.34 Funded by the CDC, NSAS is a national study that involves both hospital-based and freestanding ambulatory surgery centers and provides the most recent and comprehensive overview of ambulatory surgery in the United States.35 Because of budgetary limitations, 2006 was the last year in which data for NSAS were collected. Data for NSAS come from Medicare-participating, noninstitutional hospitals (excluding military hospitals, federal facilities, and Veteran Affairs hospitals) in all 50 states and the District of Columbia with a minimum of 6 beds staffed for patient use. NSAS used only short-stay hospitals (hospitals with an average length of stay for all patients of less than 30 days) or hospitals that had a specialty of general (medical or surgical) or children’s general. NSAS was conducted in 1994, 1996, and 2006 with medical information recorded on patient abstracts coded by contract staff. NSAS selected a sample of ambulatory surgery visits using a systematic random sampling procedure, and selection of visits within each facility was done separately for each location where ambulatory surgery was performed. In 1994, 751 facilities were sampled, and 88% of hospitals responded. In 1996, 750 facilities were sampled, and 91% of hospitals responded. In 2006, 696 facilities were sampled, and 75% responded. The surveys used International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) codes36 to classify medical diagnoses and procedures. To produce an unbiased national estimate, NCHS used multistage estimate procedures, including inflation by reciprocals of the probabilities of sample selection, population-weighting ratio adjustments, and adjustment for no response.37
Demographic and medical information was obtained for people with an ICD-9-CM diagnosis code of lateral epicondylitis (726.32), using previously described techniques.38 Data were then recorded for age, sex, facility type, insurance type, anesthesia type, diagnoses, and procedures.
Descriptive statistics consisted of means and standard deviations for continuous variables and frequency and percentages for discrete variables. Because NSAS data were collected on the basis of a probabilistic sample scheme, they were analyzed using a sampling weighting method. Sampling weights (inverse of selection probability) provided by the CDC were used to account for unequal sampling probabilities and to produce estimates for all visits in the United States. A Taylor linearization model provided by the CDC estimates was used to calculate standard error and confidence intervals (CIs) of the data. Standard error is a measure of sampling variability that occurs by chance because only a sample rather than the entire universe is surveyed. To define population parameters, NCHS chose 95% CIs along with a point estimate. Direct statistical comparison between years cannot be performed because of sampling differences in the database compared between years. The CIs, however, can suggest statistical differences if the data are nonoverlapping. US census data were used to obtain national population estimates for each year of the study (1994, 1996, 2006).39 Rates were presented as number of procedures per 100,000 standard population. For age, a direct adjustment procedure was used, and the US population in 2000 was selected as the standard population. Applying sex-specific rates to the standard population and dividing by the total in the standard population, we calculated sex-adjusted rates for each year. All data were analyzed using SPSS Version 20 software.
Results
A total of 30,311 ambulatory surgical procedures (95% CI, 27,292-33,330) or 10.44 per 100,000 capita were recorded by NSAS for the treatment of lateral epicondylitis in 2006 (Table 1). This represents a large increase in the total number of ambulatory procedures, from 21,852 in 1994 (95% CI, 19,981-23,722; 7.29/100,000) and 20,372 in 1996 (95% CI, 18,660-22,083; 6.73/100,000).
Between 1994 and 2006, the sex-adjusted rate of ambulatory surgery for lateral epicondylitis increased by 85% among females (7.74/100,000 to 14.31/100,000), whereas the rate decreased by 31% among males (8.07/100,000 to 5.59/100,000) (Table 1). The age-adjusted rate of ambulatory surgery for lateral epicondylitis increased among all age groups except the 30–39 years group (Table 2). The largest increase in age-adjusted rates was found for patients older than 50 years (275%) between 1994 and 2006.
During the study period, use of regional anesthesia nearly doubled, from 17% to 30%, whereas use of general anesthesia decreased, from 69% to 57% (Table 3). At all time points, the most common procedure performed for lateral epicondylitis in ambulatory surgery centers was division/release of the joint capsule of the elbow (Table 4). Private insurance remained the most common source of payment for all study years, ranging from 52% to 60% (Table 5). The Figure shows that, between 1994 and 2006, the proportion of surgeries performed in a freestanding ambulatory center increased.
Discussion
In this descriptive epidemiologic study, we used NSAS data to investigate trends in ambulatory surgery for lateral epicondylitis between 1994 and 2006.32 Our results showed that total number of procedures and the population-adjusted rate of procedures for lateral epicondylitis increased during the study period. The largest increase in age-adjusted rates of surgery for lateral epicondylitis was found among patients older than 50 years, whereas the highest age-adjusted rate of ambulatory surgery for lateral epicondylitis was found among patients between ages 40 and 49 years. These findings are similar to those of previous studies, which have shown that most patients with lateral epicondylitis present in the fourth and fifth decades of life.22 Prior reports have suggested that the incidence of lateral epicondylitis in men and women is equal.22 The present study found a change in sex-adjusted rates of ambulatory surgery for lateral epicondylitis between 1994 and 2006. Specifically, in 1994, surgery rates for men and women were similar (8.07/100,000 and 7.74/100,000), but in 2006 the sex-adjusted rate of surgery for lateral epicondylitis was almost 3 times higher for women than for men (14.31/100,000 vs 5.59/100,000).
We also found that the population-adjusted rate of lateral epicondylectomy increased drastically, from 0.4 per 100,000 in 1994 to 3.53 per 100,000 in 2006. Lateral epicondylectomy involves excision of the tip of the lateral epicondyle (typically, 0.5 cm) to produce a cancellous bone surface to which the edges of the débrided extensor tendon can be approximated without tension.23 It is possible that the increased rate of lateral epicondylectomy reflects evidence-based practice changes during the study period,27 though denervation was found more favorable than epicondylectomy in a recent study by Berry and colleagues.40 Future studies should investigate whether rates of epicondylectomy have changed since 2006. In addition, the present study showed a correlation between the introduction of arthroscopic techniques for the treatment of lateral epicondylitis and the period when much research was being conducted on the topic.24,25,28 As arthroscopic techniques improve, their rates are likely to continue to increase.
Our results also showed an increase in procedures performed in freestanding facilities. The rise in ambulatory surgical volume, speculated to result from more procedures being performed in freestanding facilities,34 has been reported with knee and shoulder arthroscopy.41 In addition, though general anesthesia remained the most used technique, our results showed a shift toward peripheral nerve blocks. The increase in regional anesthesia, which has also been noted in joint arthroscopy, is thought to stem from the advent of nerve-localizing technology, such as nerve stimulation and ultrasound guidance.41 Peripheral nerve blocks are favorable on both economic and quality measures, are associated with fewer opioid-related side effects, and overall provide better analgesia in comparison with opioids, highlighting their importance in the ambulatory setting.42
Although large, national databases are well suited to epidemiologic research,43 our study had limitations. As with all databases, NSAS is subject to data entry errors and coding errors.44,45 However, the database administrators corrected for this by using a multistage estimate procedure with weighting adjustments for no response and population-weighting ratio adjustments.35 Another limitation of this study is its lack of clinical detail, as procedure codes are general and do not allow differentiation between specific patients. Because of the retrospective nature of the analysis and the heterogeneity of the data, assessment of specific surgeries for lateral epicondylitis was limited. Although a strength of using NSAS to perform epidemiologic analyses is its large sample size, this also sacrifices specificity in terms of clinical insight. The results of this study may influence investigations to distinguish differences between procedures used in the treatment of lateral epicondylitis. Furthermore, the results of this study are limited to ambulatory surgery practice patterns in the United States between 1996 and 2006. Last, our ability to perform economic analyses was limited, as data on total hospital cost were not recorded by the surveys.
Conclusion
The increase in ambulatory surgery for lateral epicondylitis, demonstrated in this study, emphasizes the importance of national funding for surveys such as NSAS beyond 2006, as utilization trends may have considerable effects on health care policies that influence the quality of patient care.
First described by Runge1 in 1873 and later termed lawn-tennis arm by Major2 in 1883, lateral epicondylitis is a common cause of elbow pain, affecting 1% to 3% of the general population each year.3,4 Given that prevalence estimates are up to 15% among workers in repetitive hand task industries,5-7 symptoms of lateral epicondylitis are thought to be related to recurring wrist extension and alternating forearm pronation and supination.8 Between 80% and 90% of patients with lateral epicondylitis experience symptomatic improvement with conservative therapy,9-11 including rest and use of nonsteroidal anti-inflammatory medications,12 physical therapy,13,14 corticosteroid injections,10,15,16 orthoses,17,18 and shock wave therapy.19 However, between 4% and 11% of patients with newly diagnosed lateral epicondylitis do not respond to prolonged (6- to 12-month) conservative treatment and then require operative intervention,11,20,21 with some referral practices reporting rates as high as 25%.22
Traditionally, operative management of lateral epicondylitis involved open débridement of the extensor carpi radialis brevis (ECRB).11,20 More recently, the spectrum of operations for lateral epicondylitis has expanded to include procedures that repair the extensor origin after débridement of the torn tendon and angiofibroblastic dysplasia; procedures that use fasciotomy or direct release of the extensor origin from the epicondyle to relieve tension on the common extensor; procedures directed at the radial or posterior interosseous nerve; and procedures that use arthroscopic techniques to divide the orbicular ligament, reshape the radial head, or release the extensor origin.23 There has been debate about the value of repairing the ECRB, lengthening the ECRB, simultaneously decompressing the radial nerve or resecting epicondylar bone, and performing the procedures percutaneously, endoscopically, or arthroscopically.24-28 Despite multiple studies of the outcomes of these procedures,11,29-31 little is known regarding US national trends for operative treatment of lateral epicondylitis. Understanding national practice patterns and disease burden is essential to allocation of limited health care resources.
We conducted a study to determine US national trends in use of ambulatory surgery for lateral epicondylitis. We focused on age, sex, surgical setting, anesthetic type, and payment method.
Methods
As the National Survey of Ambulatory Surgery32 (NSAS) is an administrative dataset in which all data are deidentified and available for public use, this study was exempt from requiring institutional review board approval.
NSAS data were used to analyze trends in treatment of lateral epicondylitis between 1994 and 2006. NSAS was undertaken by the National Center for Health Statistics (NCHS) of the Centers for Disease Control and Prevention (CDC) to obtain information about the use of ambulatory surgery in the United States. Since the early 1980s, ambulatory surgery has increased in the United States because of advances in medical technology and cost-containment initiatives.33 The number of procedures being performed in ambulatory surgery centers increased from 31.5 million in 1996 to 53.3 million in 2006.34 Funded by the CDC, NSAS is a national study that involves both hospital-based and freestanding ambulatory surgery centers and provides the most recent and comprehensive overview of ambulatory surgery in the United States.35 Because of budgetary limitations, 2006 was the last year in which data for NSAS were collected. Data for NSAS come from Medicare-participating, noninstitutional hospitals (excluding military hospitals, federal facilities, and Veteran Affairs hospitals) in all 50 states and the District of Columbia with a minimum of 6 beds staffed for patient use. NSAS used only short-stay hospitals (hospitals with an average length of stay for all patients of less than 30 days) or hospitals that had a specialty of general (medical or surgical) or children’s general. NSAS was conducted in 1994, 1996, and 2006 with medical information recorded on patient abstracts coded by contract staff. NSAS selected a sample of ambulatory surgery visits using a systematic random sampling procedure, and selection of visits within each facility was done separately for each location where ambulatory surgery was performed. In 1994, 751 facilities were sampled, and 88% of hospitals responded. In 1996, 750 facilities were sampled, and 91% of hospitals responded. In 2006, 696 facilities were sampled, and 75% responded. The surveys used International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) codes36 to classify medical diagnoses and procedures. To produce an unbiased national estimate, NCHS used multistage estimate procedures, including inflation by reciprocals of the probabilities of sample selection, population-weighting ratio adjustments, and adjustment for no response.37
Demographic and medical information was obtained for people with an ICD-9-CM diagnosis code of lateral epicondylitis (726.32), using previously described techniques.38 Data were then recorded for age, sex, facility type, insurance type, anesthesia type, diagnoses, and procedures.
Descriptive statistics consisted of means and standard deviations for continuous variables and frequency and percentages for discrete variables. Because NSAS data were collected on the basis of a probabilistic sample scheme, they were analyzed using a sampling weighting method. Sampling weights (inverse of selection probability) provided by the CDC were used to account for unequal sampling probabilities and to produce estimates for all visits in the United States. A Taylor linearization model provided by the CDC estimates was used to calculate standard error and confidence intervals (CIs) of the data. Standard error is a measure of sampling variability that occurs by chance because only a sample rather than the entire universe is surveyed. To define population parameters, NCHS chose 95% CIs along with a point estimate. Direct statistical comparison between years cannot be performed because of sampling differences in the database compared between years. The CIs, however, can suggest statistical differences if the data are nonoverlapping. US census data were used to obtain national population estimates for each year of the study (1994, 1996, 2006).39 Rates were presented as number of procedures per 100,000 standard population. For age, a direct adjustment procedure was used, and the US population in 2000 was selected as the standard population. Applying sex-specific rates to the standard population and dividing by the total in the standard population, we calculated sex-adjusted rates for each year. All data were analyzed using SPSS Version 20 software.
Results
A total of 30,311 ambulatory surgical procedures (95% CI, 27,292-33,330) or 10.44 per 100,000 capita were recorded by NSAS for the treatment of lateral epicondylitis in 2006 (Table 1). This represents a large increase in the total number of ambulatory procedures, from 21,852 in 1994 (95% CI, 19,981-23,722; 7.29/100,000) and 20,372 in 1996 (95% CI, 18,660-22,083; 6.73/100,000).
Between 1994 and 2006, the sex-adjusted rate of ambulatory surgery for lateral epicondylitis increased by 85% among females (7.74/100,000 to 14.31/100,000), whereas the rate decreased by 31% among males (8.07/100,000 to 5.59/100,000) (Table 1). The age-adjusted rate of ambulatory surgery for lateral epicondylitis increased among all age groups except the 30–39 years group (Table 2). The largest increase in age-adjusted rates was found for patients older than 50 years (275%) between 1994 and 2006.
During the study period, use of regional anesthesia nearly doubled, from 17% to 30%, whereas use of general anesthesia decreased, from 69% to 57% (Table 3). At all time points, the most common procedure performed for lateral epicondylitis in ambulatory surgery centers was division/release of the joint capsule of the elbow (Table 4). Private insurance remained the most common source of payment for all study years, ranging from 52% to 60% (Table 5). The Figure shows that, between 1994 and 2006, the proportion of surgeries performed in a freestanding ambulatory center increased.
Discussion
In this descriptive epidemiologic study, we used NSAS data to investigate trends in ambulatory surgery for lateral epicondylitis between 1994 and 2006.32 Our results showed that total number of procedures and the population-adjusted rate of procedures for lateral epicondylitis increased during the study period. The largest increase in age-adjusted rates of surgery for lateral epicondylitis was found among patients older than 50 years, whereas the highest age-adjusted rate of ambulatory surgery for lateral epicondylitis was found among patients between ages 40 and 49 years. These findings are similar to those of previous studies, which have shown that most patients with lateral epicondylitis present in the fourth and fifth decades of life.22 Prior reports have suggested that the incidence of lateral epicondylitis in men and women is equal.22 The present study found a change in sex-adjusted rates of ambulatory surgery for lateral epicondylitis between 1994 and 2006. Specifically, in 1994, surgery rates for men and women were similar (8.07/100,000 and 7.74/100,000), but in 2006 the sex-adjusted rate of surgery for lateral epicondylitis was almost 3 times higher for women than for men (14.31/100,000 vs 5.59/100,000).
We also found that the population-adjusted rate of lateral epicondylectomy increased drastically, from 0.4 per 100,000 in 1994 to 3.53 per 100,000 in 2006. Lateral epicondylectomy involves excision of the tip of the lateral epicondyle (typically, 0.5 cm) to produce a cancellous bone surface to which the edges of the débrided extensor tendon can be approximated without tension.23 It is possible that the increased rate of lateral epicondylectomy reflects evidence-based practice changes during the study period,27 though denervation was found more favorable than epicondylectomy in a recent study by Berry and colleagues.40 Future studies should investigate whether rates of epicondylectomy have changed since 2006. In addition, the present study showed a correlation between the introduction of arthroscopic techniques for the treatment of lateral epicondylitis and the period when much research was being conducted on the topic.24,25,28 As arthroscopic techniques improve, their rates are likely to continue to increase.
Our results also showed an increase in procedures performed in freestanding facilities. The rise in ambulatory surgical volume, speculated to result from more procedures being performed in freestanding facilities,34 has been reported with knee and shoulder arthroscopy.41 In addition, though general anesthesia remained the most used technique, our results showed a shift toward peripheral nerve blocks. The increase in regional anesthesia, which has also been noted in joint arthroscopy, is thought to stem from the advent of nerve-localizing technology, such as nerve stimulation and ultrasound guidance.41 Peripheral nerve blocks are favorable on both economic and quality measures, are associated with fewer opioid-related side effects, and overall provide better analgesia in comparison with opioids, highlighting their importance in the ambulatory setting.42
Although large, national databases are well suited to epidemiologic research,43 our study had limitations. As with all databases, NSAS is subject to data entry errors and coding errors.44,45 However, the database administrators corrected for this by using a multistage estimate procedure with weighting adjustments for no response and population-weighting ratio adjustments.35 Another limitation of this study is its lack of clinical detail, as procedure codes are general and do not allow differentiation between specific patients. Because of the retrospective nature of the analysis and the heterogeneity of the data, assessment of specific surgeries for lateral epicondylitis was limited. Although a strength of using NSAS to perform epidemiologic analyses is its large sample size, this also sacrifices specificity in terms of clinical insight. The results of this study may influence investigations to distinguish differences between procedures used in the treatment of lateral epicondylitis. Furthermore, the results of this study are limited to ambulatory surgery practice patterns in the United States between 1996 and 2006. Last, our ability to perform economic analyses was limited, as data on total hospital cost were not recorded by the surveys.
Conclusion
The increase in ambulatory surgery for lateral epicondylitis, demonstrated in this study, emphasizes the importance of national funding for surveys such as NSAS beyond 2006, as utilization trends may have considerable effects on health care policies that influence the quality of patient care.
1. Runge F. Zur genese und behandlung des schreibekramfes. Berl Klin Wochenschr. 1873;10:245.
2. Major HP. Lawn-tennis elbow. Br Med J. 1883;2:557.
3. Allander E. Prevalence, incidence, and remission rates of some common rheumatic diseases or syndromes. Scand J Rheumatol. 1974;3(3):145-153.
4. Verhaar JA. Tennis elbow. Anatomical, epidemiological and therapeutic aspects. Int Orthop. 1994;18(5):263-267.
5. Kurppa K, Viikari-Juntura E, Kuosma E, Huuskonen M, Kivi P. Incidence of tenosynovitis or peritendinitis and epicondylitis in a meat-processing factory. Scand J Work Environ Health. 1991;17(1):32-37.
6. Ranney D, Wells R, Moore A. Upper limb musculoskeletal disorders in highly repetitive industries: precise anatomical physical findings. Ergonomics. 1995;38(7):1408-1423.
7. Haahr JP, Andersen JH. Physical and psychosocial risk factors for lateral epicondylitis: a population based case-referent study. Occup Environ Med. 2003;60(5):322-329.
8. Goldie I. Epicondylitis lateralis humeri (epicondylalgia or tennis elbow). A pathogenetical study. Acta Chir Scand Suppl. 1964;57(suppl 399):1+.
9. Binder AI, Hazleman BL. Lateral humeral epicondylitis—a study of natural history and the effect of conservative therapy. Br J Rheumatol. 1983;22(2):73-76.
10. Smidt N, van der Windt DA, Assendelft WJ, Devillé WL, Korthals-de Bos IB, Bouter LM. Corticosteroid injections, physiotherapy, or a wait-and-see policy for lateral epicondylitis: a randomised controlled trial. Lancet. 2002;359(9307):657-662.
11. Nirschl RP, Pettrone FA. Tennis elbow. The surgical treatment of lateral epicondylitis. J Bone Joint Surg Am. 1979;61(6):832-839.
12. Burnham R, Gregg R, Healy P, Steadward R. The effectiveness of topical diclofenac for lateral epicondylitis. Clin J Sport Med. 1998;8(2):78-81.
13. Martinez-Silvestrini JA, Newcomer KL, Gay RE, Schaefer MP, Kortebein P, Arendt KW. Chronic lateral epicondylitis: comparative effectiveness of a home exercise program including stretching alone versus stretching supplemented with eccentric or concentric strengthening. J Hand Ther. 2005;18(4):411-419.
14. Svernlöv B, Adolfsson L. Non-operative treatment regime including eccentric training for lateral humeral epicondylalgia. Scand J Med Sci Sports. 2001;11(6):328-334.
15. Hay EM, Paterson SM, Lewis M, Hosie G, Croft P. Pragmatic randomised controlled trial of local corticosteroid injection and naproxen for treatment of lateral epicondylitis of elbow in primary care. BMJ. 1999;319(7215):964-968.
16. Lewis M, Hay EM, Paterson SM, Croft P. Local steroid injections for tennis elbow: does the pain get worse before it gets better? Results from a randomized controlled trial. Clin J Pain. 2005;21(4):330-334.
17. Van De Streek MD, Van Der Schans CP, De Greef MH, Postema K. The effect of a forearm/hand splint compared with an elbow band as a treatment for lateral epicondylitis. Prosthet Orthot Int. 2004;28(2):183-189.
18. Struijs PA, Smidt N, Arola H, Dijk vC, Buchbinder R, Assendelft WJ. Orthotic devices for the treatment of tennis elbow. Cochrane Database Syst Rev. 2002;(1):CD001821.
19. Buchbinder R, Green SE, Youd JM, Assendelft WJ, Barnsley L, Smidt N. Shock wave therapy for lateral elbow pain. Cochrane Database Syst Rev. 2005;(4):CD003524.
20. Boyd HB, McLeod AC Jr. Tennis elbow. J Bone Joint Surg Am. 1973;55(6):1183-1187.
21. Coonrad RW, Hooper WR. Tennis elbow: its course, natural history, conservative and surgical management. J Bone Joint Surg Am. 1973;55(6):1177-1182.
22. Calfee RP, Patel A, DaSilva MF, Akelman E. Management of lateral epicondylitis: current concepts. J Am Acad Orthop Surg. 2008;16(1):19-29.
23. Plancher KD, Bishai SK. Open lateral epicondylectomy: a simple technique update for the 21st century. Tech Orthop. 2006;21(4):276-282.
24. Peart RE, Strickler SS, Schweitzer KM Jr. Lateral epicondylitis: a comparative study of open and arthroscopic lateral release. Am J Orthop. 2004;33(11):565-567.
25. Dunkow PD, Jatti M, Muddu BN. A comparison of open and percutaneous techniques in the surgical treatment of tennis elbow. J Bone Joint Surg Br. 2004;86(5):701-704.
26. Rosenberg N, Henderson I. Surgical treatment of resistant lateral epicondylitis. Follow-up study of 19 patients after excision, release and repair of proximal common extensor tendon origin. Arch Orthop Trauma Surg. 2002;122(9-10):514-517.
27. Almquist EE, Necking L, Bach AW. Epicondylar resection with anconeus muscle transfer for chronic lateral epicondylitis. J Hand Surg Am. 1998;23(4):723-731.
28. Smith AM, Castle JA, Ruch DS. Arthroscopic resection of the common extensor origin: anatomic considerations. J Shoulder Elbow Surg. 2003;12(4):375-379.
29. Baker CL Jr, Murphy KP, Gottlob CA, Curd DT. Arthroscopic classification and treatment of lateral epicondylitis: two-year clinical results. J Shoulder Elbow Surg. 2000;9(6):475-482.
30. Owens BD, Murphy KP, Kuklo TR. Arthroscopic release for lateral epicondylitis. Arthroscopy. 2001;17(6):582-587.
31. Mullett H, Sprague M, Brown G, Hausman M. Arthroscopic treatment of lateral epicondylitis: clinical and cadaveric studies. Clin Orthop Relat Res. 2005;(439):123-128.
32. National Survey of Ambulatory Surgery. Centers for Disease Control and Prevention website. http://www.cdc.gov/nchs/nsas/nsas_questionnaires.htm. Published May 4, 2010. Accessed November 10, 2015.
33. Leader S, Moon M. Medicare trends in ambulatory surgery. Health Aff. 1989;8(1):158-170.
34. Cullen KA, Hall MJ, Golosinskiy A. Ambulatory surgery in the United States, 2006. Natl Health Stat Rep. 2009;(11):1-25.
35. Kim S, Bosque J, Meehan JP, Jamali A, Marder R. Increase in outpatient knee arthroscopy in the United States: a comparison of National Surveys of Ambulatory Surgery, 1996 and 2006. J Bone Joint Surg Am. 2011;93(11):994-1000.
36. Centers for Disease Control and Prevention, National Center for Health Statistics. International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM). http://www.cdc.gov/nchs/icd/icd9cm.htm. Updated June 18, 2013. Accessed October 28, 2015.
37. Dennison C, Pokras R. Design and operation of the National Hospital Discharge Survey: 1988 redesign. Vital Health Stat 1. 2000;(39):1-42.
38. Stundner O, Kirksey M, Chiu YL, et al. Demographics and perioperative outcome in patients with depression and anxiety undergoing total joint arthroplasty: a population-based study. Psychosomatics. 2013;54(2):149-157.
39. Population estimates. US Department of Commerce, United States Census Bureau website. http://www.census.gov/popest/index.html. Accessed November 16, 2015.
40. Berry N, Neumeister MW, Russell RC, Dellon AL. Epicondylectomy versus denervation for lateral humeral epicondylitis. Hand. 2011;6(2):174-178.
41. Memtsoudis SG, Kuo C, Ma Y, Edwards A, Mazumdar M, Liguori G. Changes in anesthesia-related factors in ambulatory knee and shoulder surgery: United States 1996–2006. Reg Anesth Pain Med. 2011;36(4):327-331.
42. Richman JM, Liu SS, Courpas G, et al. Does continuous peripheral nerve block provide superior pain control to opioids? A meta-analysis. Anesth Analg. 2006;102(1):248-257.
43. Bohl DD, Basques BA, Golinvaux NS, Baumgaertner MR, Grauer JN. Nationwide Inpatient Sample and National Surgical Quality Improvement Program give different results in hip fracture studies. Clin Orthop Relat Res. 2014;472(6):1672-1680.
44. Gray DT, Hodge DO, Ilstrup DM, Butterfield LC, Baratz KH, Concordance of Medicare data and population-based clinical data on cataract surgery utilization in Olmsted County, Minnesota. Am J Epidemiol. 1997;145(12):1123-1126.
45. Memtsoudis SG. Limitations associated with the analysis of data from administrative databases. Anesthesiology. 2009;111(2):449.
1. Runge F. Zur genese und behandlung des schreibekramfes. Berl Klin Wochenschr. 1873;10:245.
2. Major HP. Lawn-tennis elbow. Br Med J. 1883;2:557.
3. Allander E. Prevalence, incidence, and remission rates of some common rheumatic diseases or syndromes. Scand J Rheumatol. 1974;3(3):145-153.
4. Verhaar JA. Tennis elbow. Anatomical, epidemiological and therapeutic aspects. Int Orthop. 1994;18(5):263-267.
5. Kurppa K, Viikari-Juntura E, Kuosma E, Huuskonen M, Kivi P. Incidence of tenosynovitis or peritendinitis and epicondylitis in a meat-processing factory. Scand J Work Environ Health. 1991;17(1):32-37.
6. Ranney D, Wells R, Moore A. Upper limb musculoskeletal disorders in highly repetitive industries: precise anatomical physical findings. Ergonomics. 1995;38(7):1408-1423.
7. Haahr JP, Andersen JH. Physical and psychosocial risk factors for lateral epicondylitis: a population based case-referent study. Occup Environ Med. 2003;60(5):322-329.
8. Goldie I. Epicondylitis lateralis humeri (epicondylalgia or tennis elbow). A pathogenetical study. Acta Chir Scand Suppl. 1964;57(suppl 399):1+.
9. Binder AI, Hazleman BL. Lateral humeral epicondylitis—a study of natural history and the effect of conservative therapy. Br J Rheumatol. 1983;22(2):73-76.
10. Smidt N, van der Windt DA, Assendelft WJ, Devillé WL, Korthals-de Bos IB, Bouter LM. Corticosteroid injections, physiotherapy, or a wait-and-see policy for lateral epicondylitis: a randomised controlled trial. Lancet. 2002;359(9307):657-662.
11. Nirschl RP, Pettrone FA. Tennis elbow. The surgical treatment of lateral epicondylitis. J Bone Joint Surg Am. 1979;61(6):832-839.
12. Burnham R, Gregg R, Healy P, Steadward R. The effectiveness of topical diclofenac for lateral epicondylitis. Clin J Sport Med. 1998;8(2):78-81.
13. Martinez-Silvestrini JA, Newcomer KL, Gay RE, Schaefer MP, Kortebein P, Arendt KW. Chronic lateral epicondylitis: comparative effectiveness of a home exercise program including stretching alone versus stretching supplemented with eccentric or concentric strengthening. J Hand Ther. 2005;18(4):411-419.
14. Svernlöv B, Adolfsson L. Non-operative treatment regime including eccentric training for lateral humeral epicondylalgia. Scand J Med Sci Sports. 2001;11(6):328-334.
15. Hay EM, Paterson SM, Lewis M, Hosie G, Croft P. Pragmatic randomised controlled trial of local corticosteroid injection and naproxen for treatment of lateral epicondylitis of elbow in primary care. BMJ. 1999;319(7215):964-968.
16. Lewis M, Hay EM, Paterson SM, Croft P. Local steroid injections for tennis elbow: does the pain get worse before it gets better? Results from a randomized controlled trial. Clin J Pain. 2005;21(4):330-334.
17. Van De Streek MD, Van Der Schans CP, De Greef MH, Postema K. The effect of a forearm/hand splint compared with an elbow band as a treatment for lateral epicondylitis. Prosthet Orthot Int. 2004;28(2):183-189.
18. Struijs PA, Smidt N, Arola H, Dijk vC, Buchbinder R, Assendelft WJ. Orthotic devices for the treatment of tennis elbow. Cochrane Database Syst Rev. 2002;(1):CD001821.
19. Buchbinder R, Green SE, Youd JM, Assendelft WJ, Barnsley L, Smidt N. Shock wave therapy for lateral elbow pain. Cochrane Database Syst Rev. 2005;(4):CD003524.
20. Boyd HB, McLeod AC Jr. Tennis elbow. J Bone Joint Surg Am. 1973;55(6):1183-1187.
21. Coonrad RW, Hooper WR. Tennis elbow: its course, natural history, conservative and surgical management. J Bone Joint Surg Am. 1973;55(6):1177-1182.
22. Calfee RP, Patel A, DaSilva MF, Akelman E. Management of lateral epicondylitis: current concepts. J Am Acad Orthop Surg. 2008;16(1):19-29.
23. Plancher KD, Bishai SK. Open lateral epicondylectomy: a simple technique update for the 21st century. Tech Orthop. 2006;21(4):276-282.
24. Peart RE, Strickler SS, Schweitzer KM Jr. Lateral epicondylitis: a comparative study of open and arthroscopic lateral release. Am J Orthop. 2004;33(11):565-567.
25. Dunkow PD, Jatti M, Muddu BN. A comparison of open and percutaneous techniques in the surgical treatment of tennis elbow. J Bone Joint Surg Br. 2004;86(5):701-704.
26. Rosenberg N, Henderson I. Surgical treatment of resistant lateral epicondylitis. Follow-up study of 19 patients after excision, release and repair of proximal common extensor tendon origin. Arch Orthop Trauma Surg. 2002;122(9-10):514-517.
27. Almquist EE, Necking L, Bach AW. Epicondylar resection with anconeus muscle transfer for chronic lateral epicondylitis. J Hand Surg Am. 1998;23(4):723-731.
28. Smith AM, Castle JA, Ruch DS. Arthroscopic resection of the common extensor origin: anatomic considerations. J Shoulder Elbow Surg. 2003;12(4):375-379.
29. Baker CL Jr, Murphy KP, Gottlob CA, Curd DT. Arthroscopic classification and treatment of lateral epicondylitis: two-year clinical results. J Shoulder Elbow Surg. 2000;9(6):475-482.
30. Owens BD, Murphy KP, Kuklo TR. Arthroscopic release for lateral epicondylitis. Arthroscopy. 2001;17(6):582-587.
31. Mullett H, Sprague M, Brown G, Hausman M. Arthroscopic treatment of lateral epicondylitis: clinical and cadaveric studies. Clin Orthop Relat Res. 2005;(439):123-128.
32. National Survey of Ambulatory Surgery. Centers for Disease Control and Prevention website. http://www.cdc.gov/nchs/nsas/nsas_questionnaires.htm. Published May 4, 2010. Accessed November 10, 2015.
33. Leader S, Moon M. Medicare trends in ambulatory surgery. Health Aff. 1989;8(1):158-170.
34. Cullen KA, Hall MJ, Golosinskiy A. Ambulatory surgery in the United States, 2006. Natl Health Stat Rep. 2009;(11):1-25.
35. Kim S, Bosque J, Meehan JP, Jamali A, Marder R. Increase in outpatient knee arthroscopy in the United States: a comparison of National Surveys of Ambulatory Surgery, 1996 and 2006. J Bone Joint Surg Am. 2011;93(11):994-1000.
36. Centers for Disease Control and Prevention, National Center for Health Statistics. International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM). http://www.cdc.gov/nchs/icd/icd9cm.htm. Updated June 18, 2013. Accessed October 28, 2015.
37. Dennison C, Pokras R. Design and operation of the National Hospital Discharge Survey: 1988 redesign. Vital Health Stat 1. 2000;(39):1-42.
38. Stundner O, Kirksey M, Chiu YL, et al. Demographics and perioperative outcome in patients with depression and anxiety undergoing total joint arthroplasty: a population-based study. Psychosomatics. 2013;54(2):149-157.
39. Population estimates. US Department of Commerce, United States Census Bureau website. http://www.census.gov/popest/index.html. Accessed November 16, 2015.
40. Berry N, Neumeister MW, Russell RC, Dellon AL. Epicondylectomy versus denervation for lateral humeral epicondylitis. Hand. 2011;6(2):174-178.
41. Memtsoudis SG, Kuo C, Ma Y, Edwards A, Mazumdar M, Liguori G. Changes in anesthesia-related factors in ambulatory knee and shoulder surgery: United States 1996–2006. Reg Anesth Pain Med. 2011;36(4):327-331.
42. Richman JM, Liu SS, Courpas G, et al. Does continuous peripheral nerve block provide superior pain control to opioids? A meta-analysis. Anesth Analg. 2006;102(1):248-257.
43. Bohl DD, Basques BA, Golinvaux NS, Baumgaertner MR, Grauer JN. Nationwide Inpatient Sample and National Surgical Quality Improvement Program give different results in hip fracture studies. Clin Orthop Relat Res. 2014;472(6):1672-1680.
44. Gray DT, Hodge DO, Ilstrup DM, Butterfield LC, Baratz KH, Concordance of Medicare data and population-based clinical data on cataract surgery utilization in Olmsted County, Minnesota. Am J Epidemiol. 1997;145(12):1123-1126.
45. Memtsoudis SG. Limitations associated with the analysis of data from administrative databases. Anesthesiology. 2009;111(2):449.
