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Take-Home Points
- Novel synovial markers and PCR have the potential to improve the detection of PJIs.
- 10Difficult-to-detect infections of prosthetic joints pose a diagnostic problem to surgeons and can lead to suboptimal outcomes.
- AD is a highly sensitive and specific synovial fluid marker for detecting PJIs.
- AD has shown promising results in detecting low virulence organisms.
- Studies are needed to determine how to best incorporate novel synovial markers and PCR to current diagnostic criteria in order to improve diagnostic accuracy.
Approximately 7 million Americans are living with a hip or knee replacement.1 According to projections, primary hip arthroplasties will increase by 174% and knee arthroplasties by 673% by 2030. Revision arthroplasties are projected to increase by 137% for hips and 601% for knees during the same time period.2 Infection and aseptic loosening are the most common causes of implant failure.3 The literature shows that infection is the most common cause of failure within 2 years after surgery and that aseptic loosening is the most common cause for late revision.3
Recent studies suggest that prosthetic joint infection (PJI) may be underreported because of difficulty making a diagnosis and that cases of aseptic loosening may in fact be attributable to infections with low-virulence organisms.2,3 These findings have led to new efforts to develop uniform criteria for diagnosing PJIs. In 2011, the Musculoskeletal Infection Society (MSIS) offered a new definition for PJI diagnosis, based on clinical and laboratory criteria, to increase the accuracy of PJI diagnosis.4 The MSIS committee acknowledged that PJI may be present even if these criteria are not met, particularly in the case of low-virulence organisms, as patients may not present with clinical signs of infection and may have normal inflammatory markers and joint aspirates. Reports of PJI cases misdiagnosed as aseptic loosening suggest that current screening and diagnostic tools are not sensitive enough to detect all infections and that PJI is likely underdiagnosed.
According to MSIS criteria, the diagnosis of PJI can be made when there is a sinus tract communicating with the prosthesis, when a pathogen is isolated by culture from 2 or more separate tissue or fluid samples obtained from the affected prosthetic joint, or when 4 of 6 criteria are met. The 6 criteria are (1) elevated serum erythrocyte sedimentation rate (ESR) (>30 mm/hour) and elevated C-reactive protein (CRP) level (>10 mg/L); (2) elevated synovial white blood cell (WBC) count (1100-4000 cells/μL); (3) elevated synovial polymorphonuclear leukocytes (>64%); (4) purulence in affected joint; (5) isolation of a microorganism in a culture of periprosthetic tissue or fluid; and (6) more than 5 neutrophils per high-power field in 5 high-power fields observed.
In this review article, we discuss recently developed novel synovial biomarkers and polymerase chain reaction (PCR) technologies that may help increase the sensitivity and specificity of diagnostic guidelines for PJI.
Methods
Using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses), we performed a systematic review of specific synovial fluid markers and PCR used in PJI diagnosis. In May 2016, we searched the PubMed database for these criteria: ((((((PCR[Text Word]) OR IL-6[Text Word]) OR leukocyte esterase[Text Word]) OR alpha defensin[Text Word]) AND ((“infection/diagnosis”[MeSH Terms] OR “infection/surgery”[MeSH Terms])))) AND (prosthetic joint infection[MeSH Terms] OR periprosthetic joint infection[MeSH Terms]).
We included patients who had undergone total hip, knee, or shoulder arthroplasty (THA, TKA, TSA). Index tests were PCR and the synovial fluid markers α-defensin (AD), interleukin 6 (IL-6), and leukocyte esterase (LE). Reference tests included joint fluid/serum analysis or tissue analysis (ESR/CRP level, cell count, culture, frozen section), which defined the MSIS criteria for PJI. Primary outcomes of interest were sensitivity and specificity, and secondary outcomes of interest included positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (+LR), and negative likelihood ratio (–LR). Randomized controlled trials and controlled cohort studies in humans published within the past 10 years were included.
Results
Our full-text review yielded 15 papers that met our study inclusion criteria (Figure 1).
α-Defensin
One of the novel synovial biomarkers that has shown significant promise in diagnosing PJIs, even with difficult-to-detect organisms, is AD. 
AD has shown even more impressive results as a biomarker for PJI in the hip and knee, where infection with low virulence organism is less common. In 2014, Deirmengian and colleagues6 conducted a prospective clinical study of 149 patients who underwent revision THA or TKA for aseptic loosening (n = 112) or PJI (n = 37) as defined by MSIS criteria. Aseptic loosening was diagnosed when there was no identifiable reason for pain, and MSIS criteria were not met. Synovial fluid aspirates were collected before or during surgery. AD correctly identified 143 of the 149 patients with confirmed infection with sensitivity of 97.3% (95% confidence interval [CI], 85.8%-99.6%) and specificity of 95.5% (95% CI, 89.9%-98.5%). Similarly, Bingham and colleagues7 conducted a retrospective clinical study of 61 assays done on 57 patients who underwent revision arthroplasty for PJI as defined by MSIS criteria. Synovial fluid aspirates were collected before or during surgery. AD correctly identified all 19 PJIs with sensitivity of 100% (95% CI, 79%-100%) and specificity of 95% (95% CI, 83%-99%). Sensitivity and specificity of the AD assay more accurately predicted infection than synovial cell count or serum ESR/CRP level did.
These results are supported by another prospective study by Deirmengian and colleagues8 differentiating aseptic failures and PJIs in THA or TKA. The sensitivity and specificity of AD in diagnosing PJI were 100% (95% CI, 85.05%-100%). 
In a prospective study of 102 patients who underwent revision THA or TKA secondary to aseptic loosening or PJI, Frangiamore and colleagues9 also demonstrated the value of AD as a diagnostic for PJI in primary and revision hip and knee arthroplasty. 
Table 1 and Figure 2 provide a concise review of the findings of each study.
Interleukin 6
Another synovial fluid biomarker that has shown promise in PJI diagnosis is IL-6. In 2015, Frangiamore and colleagues10 conducted a prospective clinical study of 32 patients who underwent revision TSA. Synovial fluid aspiration was obtained before or during surgery. MSIS criteria were used to establish the diagnosis of PJI. IL-6 had sensitivity of 87% and specificity of 90%, with +LR of 8.45 and –LR of 0.15 in predicting PJI. Synovial fluid IL-6 had strong associations with frozen section histology and growth of P acnes. Frangiamore and colleagues10 recommended an ideal IL-6 cutoff of 359.1 pg/mL and reported that, though not as accurate as AD, synovial fluid IL-6 levels can help predict positive cultures in patients who undergo revision TSA.
Lenski and Scherer11 conducted another retrospective clinical study of the diagnostic value of IL-6 in PJI. 
Randau and colleagues12 conducted a prospective clinical study of 120 patients who presented with painful THA or TKA and underwent revision for PJI, aseptic failure, or aseptic revision without signs of infection or loosening. Synovial fluid aspirate was collected before or during surgery. 
Table 2 and Figure 3 provide a concise review of the findings of each study.
Leukocyte Esterase
LE strips are an inexpensive screening tool for PJI, according to some studies. In a prospective clinical study of 364 endoprosthetic joint (hip, knee, shoulder) interventions, Guenther and colleagues13 collected synovial fluid before surgery. Samples were tested with graded LE strips using PJI criteria set by the authors. Results were correlated with preoperative synovial fluid aspirations, serum CRP level, serum WBC count, and intraoperative histopathologic and microbiological findings. Whereas 293 (93.31%) of the 314 aseptic cases had negative test strip readings, 100% of the 50 infected cases were positive. LE had sensitivity of 100%, specificity of 96.5%, PPV of 82%, and NPV of 100%.
Wetters et al14 performed a prospective clinical study on 223 patients who underwent TKAs and THAs for suspected PJI based on having criteria defined by the authors of the study. Synovial fluid samples were collected either preoperatively or intraoperatively. 
Other authors have reported different findings that LE is an unreliable marker in PJI diagnosis. In one prospective clinical study of 85 patients who underwent primary or revision TSA, synovial fluid was collected during surgery.15 According to MSIS criteria, only 5 positive LE results predicted PJI among 21 primary and revision patients with positive cultures. Of the 7 revision patients who met the MSIS criteria for PJI, only 2 had a positive LE test. LE had sensitivity of 28.6%, specificity of 63.6%, PPV of 28.6%, and NPV of 87.5%. Six of the 7 revision patients grew P acnes. These results showed that LE was unreliable in detecting shoulder PJI.15
In another prospective clinical study, Tischler and colleagues16 enrolled 189 patients who underwent revision TKA or THA for aseptic failure or PJI as defined by the MSIS criteria. Synovial fluid was collected intraoperatively. 
Table 3 and Figure 4 provide a concise review of the findings of each study.
Polymerase Chain Reaction
Studies have found that PCR analysis of synovial fluid is effective in detecting bacteria on the surface of implants removed during revision arthroplasties. Comparison of the 16S rRNA gene sequences of bacterial genomes showed a diverse range of bacterial species within biofilms on the surface of clinical and subclinical infections.17 These findings, along with those of other studies, suggest that PCR analysis of synovial fluid is useful in diagnosing PJI and identifying organisms and their sensitivities to antibiotics.
Gallo and colleagues18 performed a prospective clinical study on 115 patients who underwent revision TKAs or THAs. Synovial fluid was collected intraoperatively. PCR assays targeting the 16S rDNA were carried out on 101 patients. PJIs were classified based on criteria of the authors of this study, of which there were 42. The sensitivity, specificity, PPV, NPV, +LR, and -LR for PCR were 71.4% (95% CI, 61.5%-75.5%), 97% (95% CI, 91.7%-99.1%), 92.6% (95% CI, 79.8%-97.9%), 86.5% (95% CI, 81.8%-88.4%), 23.6 (95% CI, 5.9%-93.8%), and 0.29 (95% CI, 0.17%-0.49%), respectively. Of note the most common organism detected in 42 PJIs was coagulase-negative Staphylococcus.
Marin and colleagues19 conducted a prospective study of 122 patients who underwent arthroplasty for suspected infection or aseptic loosening as defined by the authors’ clinicohistopathologic criteria. Synovial fluid and biopsy specimens were collected during surgery, and 40 patients met the infection criteria. The authors concluded that 16S PCR is more specific and has better PPV than culture does as one positive 16S PCR resulted in a specificity and PPV of PJI of 96.3% and 91.7%, respectively. However, they noted that culture was more sensitive in diagnosing PJI.
Jacovides and colleagues20 conducted a prospective study on 82 patients undergoing primary TKA, revision TKA, and revision THA.
The low PCR sensitivities reported in the literature were explained in a review by Hartley and Harris.21 They wrote that BR 16S rDNA and sequencing of PJI samples inherently have low sensitivity because of the contamination that can occur from the PCR reagents themselves or from sample mishandling. Techniques that address contaminant (extraneous DNA) removal, such as ultraviolet irradiation and DNase treatment, reduce Taq DNA polymerase activity, which reduces PCR sensitivity. 
Table 4 and Figure 5 provide a concise review of the findings of each study.
Discussion
Although there is no gold standard for the diagnosis of PJIs, several clinical and laboratory criteria guidelines are currently used to help clinicians diagnose infections of prosthetic joints. However, despite standardization of diagnostic criteria, PJI continue to be a diagnostic challenge.
AD is a highly sensitive and specific synovial fluid biomarker in detecting common PJIs. 
In summary, 5 AD studies5-9 had sensitivity ranging from 63% to 100% and specificity ranging from 95% to 100%; 3 IL-6 studies10-12 had sensitivity ranging from 46.8% to 90.9% and specificity ranging from 85.7% to 97.6%; 4 LE studies13-16 had sensitivity ranging from 28.6% to 100% and specificity ranging from 63.6% to 96.5%; and 3 PCR studies18-20 had sensitivity ranging from 67.1% to 95.7% and specificity ranging from 12.3% to 97.8%. Sensitivity and specificity were consistently higher for AD than for IL-6, LE, and PCR, though there was significant overlap, heterogeneity, and variation across all the included studies. 
Although the overall incidence of PJI is low, infected revisions remain a substantial financial burden to hospitals, as annual costs of infected revisions is estimated to exceed $1.62 billion by 2020.25 The usefulness of novel biomarkers and PCR in diagnosing PJI can be found in their ability to diagnose infections and facilitate appropriate early treatment. Several of these tests are readily available commercially and have the potential to be cost-effective diagnostic tools. The price to perform an AD test from Synovasure TM (Zimmer Biomet) ranges from $93 to $143. LE also provides an economic option for diagnosing PJI, as LE strips are commercially available for the cost of about 25 cents. PCR has also become an economic option, as costs can average $15.50 per sample extraction or PCR assay and $42.50 per amplicon sequence as reported in a study by Vandercam and colleagues.26 Future studies are needed to determine a diagnostic algorithm which incorporates these novel synovial markers to improve diagnostic accuracy of PJI in the most cost effective manner.
The current literature supports that AD can potentially be used to screen for PJI. Our findings suggest novel synovial fluid biomarkers may become of significant diagnostic use when combined with current laboratory and clinical diagnostic criteria. We recommend use of AD in cases in which pain, stiffness, and poor TJA outcome cannot be explained by errors in surgical technique, and infection is suspected despite MSIS criteria not being met.
The studies reviewed in this manuscript were limited in that none presented level I evidence (12 had level II evidence, and 3 had level III evidence), and there was significant heterogeneity (some studies used their own diagnostic standard, and others used the MSIS criteria). Larger scale prospective studies comparing serum ESR/CRP level and synovial fluid analysis to novel synovial markers are needed.
Am J Orthop. 2017;46(4):190-198. Copyright Frontline Medical Communications Inc. 2017. All rights reserved.
1. Maradit Kremers H, Larson DR, Crowson CS, et al. Prevalence of total hip and knee replacement in the United States. J Bone Joint Surg Am. 2015;97(17):1386-1397.
2. Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg Am. 2007;89(4):780-785.
3. Sharkey PF, Lichstein PM, Shen C, Tokarski AT, Parvizi J. Why are total knee arthroplasties failing today—has anything changed after 10 years? J Arthroplasty. 2014;29(9):1774-1778.
4. Butler-Wu SM, Burns EM, Pottinger PS, et al. Optimization of periprosthetic culture for diagnosis of Propionibacterium acnes prosthetic joint infection. J Clin Microbiol. 2011;49(7):2490-2495.
5. Frangiamore SJ, Saleh A, Grosso MJ, et al. α-Defensin as a predictor of periprosthetic shoulder infection. J Shoulder Elbow Surg. 2015;24(7):1021-1027.
6. Deirmengian C, Kardos K, Kilmartin P, Cameron A, Schiller K, Parvizi J. Combined measurement of synovial fluid α-defensin and C-reactive protein levels: highly accurate for diagnosing periprosthetic joint infection. J Bone Joint Surg Am. 2014;96(17):1439-1445.
7. Bingham J, Clarke H, Spangehl M, Schwartz A, Beauchamp C, Goldberg B. The alpha defensin-1 biomarker assay can be used to evaluate the potentially infected total joint arthroplasty. Clin Orthop Relat Res. 2014;472(12):4006-4009.
8. Deirmengian C, Kardos K, Kilmartin P, et al. The alpha-defensin test for periprosthetic joint infection outperforms the leukocyte esterase test strip. Clin Orthop Relat Res. 2015;473(1):198-203.
9. Frangiamore SJ, Gajewski ND, Saleh A, Farias-Kovac M, Barsoum WK, Higuera CA. α-Defensin accuracy to diagnose periprosthetic joint infection—best available test? J Arthroplasty. 2016;31(2):456-460.
10. Frangiamore SJ, Saleh A, Kovac MF, et al. Synovial fluid interleukin-6 as a predictor of periprosthetic shoulder infection. J Bone Joint Surg Am. 2015;97(1):63-70.
11. Lenski M, Scherer MA. Synovial IL-6 as inflammatory marker in periprosthetic joint infections. J Arthroplasty. 2014;29(6):1105-1109.
12. Randau TM, Friedrich MJ, Wimmer MD, et al. Interleukin-6 in serum and in synovial fluid enhances the differentiation between periprosthetic joint infection and aseptic loosening. PLoS One. 2014;9(2):e89045.
13. Guenther D, Kokenge T, Jacobs O, et al. Excluding infections in arthroplasty using leucocyte esterase test. Int Orthop. 2014;38(11):2385-2390.
14. Wetters NG, Berend KR, Lombardi AV, Morris MJ, Tucker TL, Della Valle CJ. Leukocyte esterase reagent strips for the rapid diagnosis of periprosthetic joint infection. J Arthroplasty. 2012;27(8 suppl):8-11.
15. Nelson GN, Paxton ES, Narzikul A, Williams G, Lazarus MD, Abboud JA. Leukocyte esterase in the diagnosis of shoulder periprosthetic joint infection. J Shoulder Elbow Surg. 2015;24(9):1421-1426.
16. Tischler EH, Cavanaugh PK, Parvizi J. Leukocyte esterase strip test: matched for Musculoskeletal Infection Society criteria. J Bone Joint Surg Am. 2014;96(22):1917-1920.
17. Dempsey KE, Riggio MP, Lennon A, et al. Identification of bacteria on the surface of clinically infected and non-infected prosthetic hip joints removed during revision arthroplasties by 16S rRNA gene sequencing and by microbiological culture. Arthritis Res Ther. 2007;9(3):R46.
18. Gallo J, Kolar M, Dendis M, et al. Culture and PCR analysis of joint fluid in the diagnosis of prosthetic joint infection. New Microbiol. 2008;31(1):97-104.
19. Marin M, Garcia-Lechuz JM, Alonso P, et al. Role of universal 16S rRNA gene PCR and sequencing in diagnosis of prosthetic joint infection. J Clin Microbiol. 2012;50(3):583-589.
20. Jacovides CL, Kreft R, Adeli B, Hozack B, Ehrlich GD, Parvizi J. Successful identification of pathogens by polymerase chain reaction (PCR)-based electron spray ionization time-of-flight mass spectrometry (ESI-TOF-MS) in culture-negative periprosthetic joint infection. J Bone Joint Surg Am. 2012;94(24):2247-2254.
21. Hartley JC, Harris KA. Molecular techniques for diagnosing prosthetic joint infections. J Antimicrob Chemother. 2014;69(suppl 1):i21-i24.
22. Zappe B, Graf S, Ochsner PE, Zimmerli W, Sendi P. Propionibacterium spp. in prosthetic joint infections: a diagnostic challenge. Arch Orthop Trauma Surg. 2008;128(10):1039-1046.
23. Rasouli MR, Harandi AA, Adeli B, Purtill JJ, Parvizi J. Revision total knee arthroplasty: infection should be ruled out in all cases. J Arthroplasty. 2012;27(6):1239-1243.e1-e2.
24. Hunt RW, Bond MJ, Pater GD. Psychological responses to cancer: a case for cancer support groups. Community Health Stud. 1990;14(1):35-38.
25. Kurtz SM, Lau E, Schmier J, Ong KL, Zhao K, Parvizi J. Infection burden for hip and knee arthroplasty in the United States. J Arthroplasty. 2008;23(7):984-991.
26. Vandercam B, Jeumont S, Cornu O, et al. Amplification-based DNA analysis in the diagnosis of prosthetic joint infection. J Mol Diagn. 2008;10(6):537-543.
Take-Home Points
- Novel synovial markers and PCR have the potential to improve the detection of PJIs.
- 10Difficult-to-detect infections of prosthetic joints pose a diagnostic problem to surgeons and can lead to suboptimal outcomes.
- AD is a highly sensitive and specific synovial fluid marker for detecting PJIs.
- AD has shown promising results in detecting low virulence organisms.
- Studies are needed to determine how to best incorporate novel synovial markers and PCR to current diagnostic criteria in order to improve diagnostic accuracy.
Approximately 7 million Americans are living with a hip or knee replacement.1 According to projections, primary hip arthroplasties will increase by 174% and knee arthroplasties by 673% by 2030. Revision arthroplasties are projected to increase by 137% for hips and 601% for knees during the same time period.2 Infection and aseptic loosening are the most common causes of implant failure.3 The literature shows that infection is the most common cause of failure within 2 years after surgery and that aseptic loosening is the most common cause for late revision.3
Recent studies suggest that prosthetic joint infection (PJI) may be underreported because of difficulty making a diagnosis and that cases of aseptic loosening may in fact be attributable to infections with low-virulence organisms.2,3 These findings have led to new efforts to develop uniform criteria for diagnosing PJIs. In 2011, the Musculoskeletal Infection Society (MSIS) offered a new definition for PJI diagnosis, based on clinical and laboratory criteria, to increase the accuracy of PJI diagnosis.4 The MSIS committee acknowledged that PJI may be present even if these criteria are not met, particularly in the case of low-virulence organisms, as patients may not present with clinical signs of infection and may have normal inflammatory markers and joint aspirates. Reports of PJI cases misdiagnosed as aseptic loosening suggest that current screening and diagnostic tools are not sensitive enough to detect all infections and that PJI is likely underdiagnosed.
According to MSIS criteria, the diagnosis of PJI can be made when there is a sinus tract communicating with the prosthesis, when a pathogen is isolated by culture from 2 or more separate tissue or fluid samples obtained from the affected prosthetic joint, or when 4 of 6 criteria are met. The 6 criteria are (1) elevated serum erythrocyte sedimentation rate (ESR) (>30 mm/hour) and elevated C-reactive protein (CRP) level (>10 mg/L); (2) elevated synovial white blood cell (WBC) count (1100-4000 cells/μL); (3) elevated synovial polymorphonuclear leukocytes (>64%); (4) purulence in affected joint; (5) isolation of a microorganism in a culture of periprosthetic tissue or fluid; and (6) more than 5 neutrophils per high-power field in 5 high-power fields observed.
In this review article, we discuss recently developed novel synovial biomarkers and polymerase chain reaction (PCR) technologies that may help increase the sensitivity and specificity of diagnostic guidelines for PJI.
Methods
Using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses), we performed a systematic review of specific synovial fluid markers and PCR used in PJI diagnosis. In May 2016, we searched the PubMed database for these criteria: ((((((PCR[Text Word]) OR IL-6[Text Word]) OR leukocyte esterase[Text Word]) OR alpha defensin[Text Word]) AND ((“infection/diagnosis”[MeSH Terms] OR “infection/surgery”[MeSH Terms])))) AND (prosthetic joint infection[MeSH Terms] OR periprosthetic joint infection[MeSH Terms]).
We included patients who had undergone total hip, knee, or shoulder arthroplasty (THA, TKA, TSA). Index tests were PCR and the synovial fluid markers α-defensin (AD), interleukin 6 (IL-6), and leukocyte esterase (LE). Reference tests included joint fluid/serum analysis or tissue analysis (ESR/CRP level, cell count, culture, frozen section), which defined the MSIS criteria for PJI. Primary outcomes of interest were sensitivity and specificity, and secondary outcomes of interest included positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (+LR), and negative likelihood ratio (–LR). Randomized controlled trials and controlled cohort studies in humans published within the past 10 years were included.
Results
Our full-text review yielded 15 papers that met our study inclusion criteria (Figure 1).
α-Defensin
One of the novel synovial biomarkers that has shown significant promise in diagnosing PJIs, even with difficult-to-detect organisms, is AD.
AD has shown even more impressive results as a biomarker for PJI in the hip and knee, where infection with low virulence organism is less common. In 2014, Deirmengian and colleagues6 conducted a prospective clinical study of 149 patients who underwent revision THA or TKA for aseptic loosening (n = 112) or PJI (n = 37) as defined by MSIS criteria. Aseptic loosening was diagnosed when there was no identifiable reason for pain, and MSIS criteria were not met. Synovial fluid aspirates were collected before or during surgery. AD correctly identified 143 of the 149 patients with confirmed infection with sensitivity of 97.3% (95% confidence interval [CI], 85.8%-99.6%) and specificity of 95.5% (95% CI, 89.9%-98.5%). Similarly, Bingham and colleagues7 conducted a retrospective clinical study of 61 assays done on 57 patients who underwent revision arthroplasty for PJI as defined by MSIS criteria. Synovial fluid aspirates were collected before or during surgery. AD correctly identified all 19 PJIs with sensitivity of 100% (95% CI, 79%-100%) and specificity of 95% (95% CI, 83%-99%). Sensitivity and specificity of the AD assay more accurately predicted infection than synovial cell count or serum ESR/CRP level did.
These results are supported by another prospective study by Deirmengian and colleagues8 differentiating aseptic failures and PJIs in THA or TKA. The sensitivity and specificity of AD in diagnosing PJI were 100% (95% CI, 85.05%-100%).
In a prospective study of 102 patients who underwent revision THA or TKA secondary to aseptic loosening or PJI, Frangiamore and colleagues9 also demonstrated the value of AD as a diagnostic for PJI in primary and revision hip and knee arthroplasty.
Table 1 and Figure 2 provide a concise review of the findings of each study.
Interleukin 6
Another synovial fluid biomarker that has shown promise in PJI diagnosis is IL-6. In 2015, Frangiamore and colleagues10 conducted a prospective clinical study of 32 patients who underwent revision TSA. Synovial fluid aspiration was obtained before or during surgery. MSIS criteria were used to establish the diagnosis of PJI. IL-6 had sensitivity of 87% and specificity of 90%, with +LR of 8.45 and –LR of 0.15 in predicting PJI. Synovial fluid IL-6 had strong associations with frozen section histology and growth of P acnes. Frangiamore and colleagues10 recommended an ideal IL-6 cutoff of 359.1 pg/mL and reported that, though not as accurate as AD, synovial fluid IL-6 levels can help predict positive cultures in patients who undergo revision TSA.
Lenski and Scherer11 conducted another retrospective clinical study of the diagnostic value of IL-6 in PJI.
Randau and colleagues12 conducted a prospective clinical study of 120 patients who presented with painful THA or TKA and underwent revision for PJI, aseptic failure, or aseptic revision without signs of infection or loosening. Synovial fluid aspirate was collected before or during surgery.
Table 2 and Figure 3 provide a concise review of the findings of each study.
Leukocyte Esterase
LE strips are an inexpensive screening tool for PJI, according to some studies. In a prospective clinical study of 364 endoprosthetic joint (hip, knee, shoulder) interventions, Guenther and colleagues13 collected synovial fluid before surgery. Samples were tested with graded LE strips using PJI criteria set by the authors. Results were correlated with preoperative synovial fluid aspirations, serum CRP level, serum WBC count, and intraoperative histopathologic and microbiological findings. Whereas 293 (93.31%) of the 314 aseptic cases had negative test strip readings, 100% of the 50 infected cases were positive. LE had sensitivity of 100%, specificity of 96.5%, PPV of 82%, and NPV of 100%.
Wetters et al14 performed a prospective clinical study on 223 patients who underwent TKAs and THAs for suspected PJI based on having criteria defined by the authors of the study. Synovial fluid samples were collected either preoperatively or intraoperatively.
Other authors have reported different findings that LE is an unreliable marker in PJI diagnosis. In one prospective clinical study of 85 patients who underwent primary or revision TSA, synovial fluid was collected during surgery.15 According to MSIS criteria, only 5 positive LE results predicted PJI among 21 primary and revision patients with positive cultures. Of the 7 revision patients who met the MSIS criteria for PJI, only 2 had a positive LE test. LE had sensitivity of 28.6%, specificity of 63.6%, PPV of 28.6%, and NPV of 87.5%. Six of the 7 revision patients grew P acnes. These results showed that LE was unreliable in detecting shoulder PJI.15
In another prospective clinical study, Tischler and colleagues16 enrolled 189 patients who underwent revision TKA or THA for aseptic failure or PJI as defined by the MSIS criteria. Synovial fluid was collected intraoperatively.
Table 3 and Figure 4 provide a concise review of the findings of each study.
Polymerase Chain Reaction
Studies have found that PCR analysis of synovial fluid is effective in detecting bacteria on the surface of implants removed during revision arthroplasties. Comparison of the 16S rRNA gene sequences of bacterial genomes showed a diverse range of bacterial species within biofilms on the surface of clinical and subclinical infections.17 These findings, along with those of other studies, suggest that PCR analysis of synovial fluid is useful in diagnosing PJI and identifying organisms and their sensitivities to antibiotics.
Gallo and colleagues18 performed a prospective clinical study on 115 patients who underwent revision TKAs or THAs. Synovial fluid was collected intraoperatively. PCR assays targeting the 16S rDNA were carried out on 101 patients. PJIs were classified based on criteria of the authors of this study, of which there were 42. The sensitivity, specificity, PPV, NPV, +LR, and -LR for PCR were 71.4% (95% CI, 61.5%-75.5%), 97% (95% CI, 91.7%-99.1%), 92.6% (95% CI, 79.8%-97.9%), 86.5% (95% CI, 81.8%-88.4%), 23.6 (95% CI, 5.9%-93.8%), and 0.29 (95% CI, 0.17%-0.49%), respectively. Of note the most common organism detected in 42 PJIs was coagulase-negative Staphylococcus.
Marin and colleagues19 conducted a prospective study of 122 patients who underwent arthroplasty for suspected infection or aseptic loosening as defined by the authors’ clinicohistopathologic criteria. Synovial fluid and biopsy specimens were collected during surgery, and 40 patients met the infection criteria. The authors concluded that 16S PCR is more specific and has better PPV than culture does as one positive 16S PCR resulted in a specificity and PPV of PJI of 96.3% and 91.7%, respectively. However, they noted that culture was more sensitive in diagnosing PJI.
Jacovides and colleagues20 conducted a prospective study on 82 patients undergoing primary TKA, revision TKA, and revision THA.
The low PCR sensitivities reported in the literature were explained in a review by Hartley and Harris.21 They wrote that BR 16S rDNA and sequencing of PJI samples inherently have low sensitivity because of the contamination that can occur from the PCR reagents themselves or from sample mishandling. Techniques that address contaminant (extraneous DNA) removal, such as ultraviolet irradiation and DNase treatment, reduce Taq DNA polymerase activity, which reduces PCR sensitivity.
Table 4 and Figure 5 provide a concise review of the findings of each study.
Discussion
Although there is no gold standard for the diagnosis of PJIs, several clinical and laboratory criteria guidelines are currently used to help clinicians diagnose infections of prosthetic joints. However, despite standardization of diagnostic criteria, PJI continue to be a diagnostic challenge.
AD is a highly sensitive and specific synovial fluid biomarker in detecting common PJIs.
In summary, 5 AD studies5-9 had sensitivity ranging from 63% to 100% and specificity ranging from 95% to 100%; 3 IL-6 studies10-12 had sensitivity ranging from 46.8% to 90.9% and specificity ranging from 85.7% to 97.6%; 4 LE studies13-16 had sensitivity ranging from 28.6% to 100% and specificity ranging from 63.6% to 96.5%; and 3 PCR studies18-20 had sensitivity ranging from 67.1% to 95.7% and specificity ranging from 12.3% to 97.8%. Sensitivity and specificity were consistently higher for AD than for IL-6, LE, and PCR, though there was significant overlap, heterogeneity, and variation across all the included studies.
Although the overall incidence of PJI is low, infected revisions remain a substantial financial burden to hospitals, as annual costs of infected revisions is estimated to exceed $1.62 billion by 2020.25 The usefulness of novel biomarkers and PCR in diagnosing PJI can be found in their ability to diagnose infections and facilitate appropriate early treatment. Several of these tests are readily available commercially and have the potential to be cost-effective diagnostic tools. The price to perform an AD test from Synovasure TM (Zimmer Biomet) ranges from $93 to $143. LE also provides an economic option for diagnosing PJI, as LE strips are commercially available for the cost of about 25 cents. PCR has also become an economic option, as costs can average $15.50 per sample extraction or PCR assay and $42.50 per amplicon sequence as reported in a study by Vandercam and colleagues.26 Future studies are needed to determine a diagnostic algorithm which incorporates these novel synovial markers to improve diagnostic accuracy of PJI in the most cost effective manner.
The current literature supports that AD can potentially be used to screen for PJI. Our findings suggest novel synovial fluid biomarkers may become of significant diagnostic use when combined with current laboratory and clinical diagnostic criteria. We recommend use of AD in cases in which pain, stiffness, and poor TJA outcome cannot be explained by errors in surgical technique, and infection is suspected despite MSIS criteria not being met.
The studies reviewed in this manuscript were limited in that none presented level I evidence (12 had level II evidence, and 3 had level III evidence), and there was significant heterogeneity (some studies used their own diagnostic standard, and others used the MSIS criteria). Larger scale prospective studies comparing serum ESR/CRP level and synovial fluid analysis to novel synovial markers are needed.
Am J Orthop. 2017;46(4):190-198. Copyright Frontline Medical Communications Inc. 2017. All rights reserved.
Take-Home Points
- Novel synovial markers and PCR have the potential to improve the detection of PJIs.
- 10Difficult-to-detect infections of prosthetic joints pose a diagnostic problem to surgeons and can lead to suboptimal outcomes.
- AD is a highly sensitive and specific synovial fluid marker for detecting PJIs.
- AD has shown promising results in detecting low virulence organisms.
- Studies are needed to determine how to best incorporate novel synovial markers and PCR to current diagnostic criteria in order to improve diagnostic accuracy.
Approximately 7 million Americans are living with a hip or knee replacement.1 According to projections, primary hip arthroplasties will increase by 174% and knee arthroplasties by 673% by 2030. Revision arthroplasties are projected to increase by 137% for hips and 601% for knees during the same time period.2 Infection and aseptic loosening are the most common causes of implant failure.3 The literature shows that infection is the most common cause of failure within 2 years after surgery and that aseptic loosening is the most common cause for late revision.3
Recent studies suggest that prosthetic joint infection (PJI) may be underreported because of difficulty making a diagnosis and that cases of aseptic loosening may in fact be attributable to infections with low-virulence organisms.2,3 These findings have led to new efforts to develop uniform criteria for diagnosing PJIs. In 2011, the Musculoskeletal Infection Society (MSIS) offered a new definition for PJI diagnosis, based on clinical and laboratory criteria, to increase the accuracy of PJI diagnosis.4 The MSIS committee acknowledged that PJI may be present even if these criteria are not met, particularly in the case of low-virulence organisms, as patients may not present with clinical signs of infection and may have normal inflammatory markers and joint aspirates. Reports of PJI cases misdiagnosed as aseptic loosening suggest that current screening and diagnostic tools are not sensitive enough to detect all infections and that PJI is likely underdiagnosed.
According to MSIS criteria, the diagnosis of PJI can be made when there is a sinus tract communicating with the prosthesis, when a pathogen is isolated by culture from 2 or more separate tissue or fluid samples obtained from the affected prosthetic joint, or when 4 of 6 criteria are met. The 6 criteria are (1) elevated serum erythrocyte sedimentation rate (ESR) (>30 mm/hour) and elevated C-reactive protein (CRP) level (>10 mg/L); (2) elevated synovial white blood cell (WBC) count (1100-4000 cells/μL); (3) elevated synovial polymorphonuclear leukocytes (>64%); (4) purulence in affected joint; (5) isolation of a microorganism in a culture of periprosthetic tissue or fluid; and (6) more than 5 neutrophils per high-power field in 5 high-power fields observed.
In this review article, we discuss recently developed novel synovial biomarkers and polymerase chain reaction (PCR) technologies that may help increase the sensitivity and specificity of diagnostic guidelines for PJI.
Methods
Using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses), we performed a systematic review of specific synovial fluid markers and PCR used in PJI diagnosis. In May 2016, we searched the PubMed database for these criteria: ((((((PCR[Text Word]) OR IL-6[Text Word]) OR leukocyte esterase[Text Word]) OR alpha defensin[Text Word]) AND ((“infection/diagnosis”[MeSH Terms] OR “infection/surgery”[MeSH Terms])))) AND (prosthetic joint infection[MeSH Terms] OR periprosthetic joint infection[MeSH Terms]).
We included patients who had undergone total hip, knee, or shoulder arthroplasty (THA, TKA, TSA). Index tests were PCR and the synovial fluid markers α-defensin (AD), interleukin 6 (IL-6), and leukocyte esterase (LE). Reference tests included joint fluid/serum analysis or tissue analysis (ESR/CRP level, cell count, culture, frozen section), which defined the MSIS criteria for PJI. Primary outcomes of interest were sensitivity and specificity, and secondary outcomes of interest included positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (+LR), and negative likelihood ratio (–LR). Randomized controlled trials and controlled cohort studies in humans published within the past 10 years were included.
Results
Our full-text review yielded 15 papers that met our study inclusion criteria (Figure 1).
α-Defensin
One of the novel synovial biomarkers that has shown significant promise in diagnosing PJIs, even with difficult-to-detect organisms, is AD.
AD has shown even more impressive results as a biomarker for PJI in the hip and knee, where infection with low virulence organism is less common. In 2014, Deirmengian and colleagues6 conducted a prospective clinical study of 149 patients who underwent revision THA or TKA for aseptic loosening (n = 112) or PJI (n = 37) as defined by MSIS criteria. Aseptic loosening was diagnosed when there was no identifiable reason for pain, and MSIS criteria were not met. Synovial fluid aspirates were collected before or during surgery. AD correctly identified 143 of the 149 patients with confirmed infection with sensitivity of 97.3% (95% confidence interval [CI], 85.8%-99.6%) and specificity of 95.5% (95% CI, 89.9%-98.5%). Similarly, Bingham and colleagues7 conducted a retrospective clinical study of 61 assays done on 57 patients who underwent revision arthroplasty for PJI as defined by MSIS criteria. Synovial fluid aspirates were collected before or during surgery. AD correctly identified all 19 PJIs with sensitivity of 100% (95% CI, 79%-100%) and specificity of 95% (95% CI, 83%-99%). Sensitivity and specificity of the AD assay more accurately predicted infection than synovial cell count or serum ESR/CRP level did.
These results are supported by another prospective study by Deirmengian and colleagues8 differentiating aseptic failures and PJIs in THA or TKA. The sensitivity and specificity of AD in diagnosing PJI were 100% (95% CI, 85.05%-100%).
In a prospective study of 102 patients who underwent revision THA or TKA secondary to aseptic loosening or PJI, Frangiamore and colleagues9 also demonstrated the value of AD as a diagnostic for PJI in primary and revision hip and knee arthroplasty.
Table 1 and Figure 2 provide a concise review of the findings of each study.
Interleukin 6
Another synovial fluid biomarker that has shown promise in PJI diagnosis is IL-6. In 2015, Frangiamore and colleagues10 conducted a prospective clinical study of 32 patients who underwent revision TSA. Synovial fluid aspiration was obtained before or during surgery. MSIS criteria were used to establish the diagnosis of PJI. IL-6 had sensitivity of 87% and specificity of 90%, with +LR of 8.45 and –LR of 0.15 in predicting PJI. Synovial fluid IL-6 had strong associations with frozen section histology and growth of P acnes. Frangiamore and colleagues10 recommended an ideal IL-6 cutoff of 359.1 pg/mL and reported that, though not as accurate as AD, synovial fluid IL-6 levels can help predict positive cultures in patients who undergo revision TSA.
Lenski and Scherer11 conducted another retrospective clinical study of the diagnostic value of IL-6 in PJI.
Randau and colleagues12 conducted a prospective clinical study of 120 patients who presented with painful THA or TKA and underwent revision for PJI, aseptic failure, or aseptic revision without signs of infection or loosening. Synovial fluid aspirate was collected before or during surgery.
Table 2 and Figure 3 provide a concise review of the findings of each study.
Leukocyte Esterase
LE strips are an inexpensive screening tool for PJI, according to some studies. In a prospective clinical study of 364 endoprosthetic joint (hip, knee, shoulder) interventions, Guenther and colleagues13 collected synovial fluid before surgery. Samples were tested with graded LE strips using PJI criteria set by the authors. Results were correlated with preoperative synovial fluid aspirations, serum CRP level, serum WBC count, and intraoperative histopathologic and microbiological findings. Whereas 293 (93.31%) of the 314 aseptic cases had negative test strip readings, 100% of the 50 infected cases were positive. LE had sensitivity of 100%, specificity of 96.5%, PPV of 82%, and NPV of 100%.
Wetters et al14 performed a prospective clinical study on 223 patients who underwent TKAs and THAs for suspected PJI based on having criteria defined by the authors of the study. Synovial fluid samples were collected either preoperatively or intraoperatively.
Other authors have reported different findings that LE is an unreliable marker in PJI diagnosis. In one prospective clinical study of 85 patients who underwent primary or revision TSA, synovial fluid was collected during surgery.15 According to MSIS criteria, only 5 positive LE results predicted PJI among 21 primary and revision patients with positive cultures. Of the 7 revision patients who met the MSIS criteria for PJI, only 2 had a positive LE test. LE had sensitivity of 28.6%, specificity of 63.6%, PPV of 28.6%, and NPV of 87.5%. Six of the 7 revision patients grew P acnes. These results showed that LE was unreliable in detecting shoulder PJI.15
In another prospective clinical study, Tischler and colleagues16 enrolled 189 patients who underwent revision TKA or THA for aseptic failure or PJI as defined by the MSIS criteria. Synovial fluid was collected intraoperatively.
Table 3 and Figure 4 provide a concise review of the findings of each study.
Polymerase Chain Reaction
Studies have found that PCR analysis of synovial fluid is effective in detecting bacteria on the surface of implants removed during revision arthroplasties. Comparison of the 16S rRNA gene sequences of bacterial genomes showed a diverse range of bacterial species within biofilms on the surface of clinical and subclinical infections.17 These findings, along with those of other studies, suggest that PCR analysis of synovial fluid is useful in diagnosing PJI and identifying organisms and their sensitivities to antibiotics.
Gallo and colleagues18 performed a prospective clinical study on 115 patients who underwent revision TKAs or THAs. Synovial fluid was collected intraoperatively. PCR assays targeting the 16S rDNA were carried out on 101 patients. PJIs were classified based on criteria of the authors of this study, of which there were 42. The sensitivity, specificity, PPV, NPV, +LR, and -LR for PCR were 71.4% (95% CI, 61.5%-75.5%), 97% (95% CI, 91.7%-99.1%), 92.6% (95% CI, 79.8%-97.9%), 86.5% (95% CI, 81.8%-88.4%), 23.6 (95% CI, 5.9%-93.8%), and 0.29 (95% CI, 0.17%-0.49%), respectively. Of note the most common organism detected in 42 PJIs was coagulase-negative Staphylococcus.
Marin and colleagues19 conducted a prospective study of 122 patients who underwent arthroplasty for suspected infection or aseptic loosening as defined by the authors’ clinicohistopathologic criteria. Synovial fluid and biopsy specimens were collected during surgery, and 40 patients met the infection criteria. The authors concluded that 16S PCR is more specific and has better PPV than culture does as one positive 16S PCR resulted in a specificity and PPV of PJI of 96.3% and 91.7%, respectively. However, they noted that culture was more sensitive in diagnosing PJI.
Jacovides and colleagues20 conducted a prospective study on 82 patients undergoing primary TKA, revision TKA, and revision THA.
The low PCR sensitivities reported in the literature were explained in a review by Hartley and Harris.21 They wrote that BR 16S rDNA and sequencing of PJI samples inherently have low sensitivity because of the contamination that can occur from the PCR reagents themselves or from sample mishandling. Techniques that address contaminant (extraneous DNA) removal, such as ultraviolet irradiation and DNase treatment, reduce Taq DNA polymerase activity, which reduces PCR sensitivity.
Table 4 and Figure 5 provide a concise review of the findings of each study.
Discussion
Although there is no gold standard for the diagnosis of PJIs, several clinical and laboratory criteria guidelines are currently used to help clinicians diagnose infections of prosthetic joints. However, despite standardization of diagnostic criteria, PJI continue to be a diagnostic challenge.
AD is a highly sensitive and specific synovial fluid biomarker in detecting common PJIs.
In summary, 5 AD studies5-9 had sensitivity ranging from 63% to 100% and specificity ranging from 95% to 100%; 3 IL-6 studies10-12 had sensitivity ranging from 46.8% to 90.9% and specificity ranging from 85.7% to 97.6%; 4 LE studies13-16 had sensitivity ranging from 28.6% to 100% and specificity ranging from 63.6% to 96.5%; and 3 PCR studies18-20 had sensitivity ranging from 67.1% to 95.7% and specificity ranging from 12.3% to 97.8%. Sensitivity and specificity were consistently higher for AD than for IL-6, LE, and PCR, though there was significant overlap, heterogeneity, and variation across all the included studies.
Although the overall incidence of PJI is low, infected revisions remain a substantial financial burden to hospitals, as annual costs of infected revisions is estimated to exceed $1.62 billion by 2020.25 The usefulness of novel biomarkers and PCR in diagnosing PJI can be found in their ability to diagnose infections and facilitate appropriate early treatment. Several of these tests are readily available commercially and have the potential to be cost-effective diagnostic tools. The price to perform an AD test from Synovasure TM (Zimmer Biomet) ranges from $93 to $143. LE also provides an economic option for diagnosing PJI, as LE strips are commercially available for the cost of about 25 cents. PCR has also become an economic option, as costs can average $15.50 per sample extraction or PCR assay and $42.50 per amplicon sequence as reported in a study by Vandercam and colleagues.26 Future studies are needed to determine a diagnostic algorithm which incorporates these novel synovial markers to improve diagnostic accuracy of PJI in the most cost effective manner.
The current literature supports that AD can potentially be used to screen for PJI. Our findings suggest novel synovial fluid biomarkers may become of significant diagnostic use when combined with current laboratory and clinical diagnostic criteria. We recommend use of AD in cases in which pain, stiffness, and poor TJA outcome cannot be explained by errors in surgical technique, and infection is suspected despite MSIS criteria not being met.
The studies reviewed in this manuscript were limited in that none presented level I evidence (12 had level II evidence, and 3 had level III evidence), and there was significant heterogeneity (some studies used their own diagnostic standard, and others used the MSIS criteria). Larger scale prospective studies comparing serum ESR/CRP level and synovial fluid analysis to novel synovial markers are needed.
Am J Orthop. 2017;46(4):190-198. Copyright Frontline Medical Communications Inc. 2017. All rights reserved.
1. Maradit Kremers H, Larson DR, Crowson CS, et al. Prevalence of total hip and knee replacement in the United States. J Bone Joint Surg Am. 2015;97(17):1386-1397.
2. Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg Am. 2007;89(4):780-785.
3. Sharkey PF, Lichstein PM, Shen C, Tokarski AT, Parvizi J. Why are total knee arthroplasties failing today—has anything changed after 10 years? J Arthroplasty. 2014;29(9):1774-1778.
4. Butler-Wu SM, Burns EM, Pottinger PS, et al. Optimization of periprosthetic culture for diagnosis of Propionibacterium acnes prosthetic joint infection. J Clin Microbiol. 2011;49(7):2490-2495.
5. Frangiamore SJ, Saleh A, Grosso MJ, et al. α-Defensin as a predictor of periprosthetic shoulder infection. J Shoulder Elbow Surg. 2015;24(7):1021-1027.
6. Deirmengian C, Kardos K, Kilmartin P, Cameron A, Schiller K, Parvizi J. Combined measurement of synovial fluid α-defensin and C-reactive protein levels: highly accurate for diagnosing periprosthetic joint infection. J Bone Joint Surg Am. 2014;96(17):1439-1445.
7. Bingham J, Clarke H, Spangehl M, Schwartz A, Beauchamp C, Goldberg B. The alpha defensin-1 biomarker assay can be used to evaluate the potentially infected total joint arthroplasty. Clin Orthop Relat Res. 2014;472(12):4006-4009.
8. Deirmengian C, Kardos K, Kilmartin P, et al. The alpha-defensin test for periprosthetic joint infection outperforms the leukocyte esterase test strip. Clin Orthop Relat Res. 2015;473(1):198-203.
9. Frangiamore SJ, Gajewski ND, Saleh A, Farias-Kovac M, Barsoum WK, Higuera CA. α-Defensin accuracy to diagnose periprosthetic joint infection—best available test? J Arthroplasty. 2016;31(2):456-460.
10. Frangiamore SJ, Saleh A, Kovac MF, et al. Synovial fluid interleukin-6 as a predictor of periprosthetic shoulder infection. J Bone Joint Surg Am. 2015;97(1):63-70.
11. Lenski M, Scherer MA. Synovial IL-6 as inflammatory marker in periprosthetic joint infections. J Arthroplasty. 2014;29(6):1105-1109.
12. Randau TM, Friedrich MJ, Wimmer MD, et al. Interleukin-6 in serum and in synovial fluid enhances the differentiation between periprosthetic joint infection and aseptic loosening. PLoS One. 2014;9(2):e89045.
13. Guenther D, Kokenge T, Jacobs O, et al. Excluding infections in arthroplasty using leucocyte esterase test. Int Orthop. 2014;38(11):2385-2390.
14. Wetters NG, Berend KR, Lombardi AV, Morris MJ, Tucker TL, Della Valle CJ. Leukocyte esterase reagent strips for the rapid diagnosis of periprosthetic joint infection. J Arthroplasty. 2012;27(8 suppl):8-11.
15. Nelson GN, Paxton ES, Narzikul A, Williams G, Lazarus MD, Abboud JA. Leukocyte esterase in the diagnosis of shoulder periprosthetic joint infection. J Shoulder Elbow Surg. 2015;24(9):1421-1426.
16. Tischler EH, Cavanaugh PK, Parvizi J. Leukocyte esterase strip test: matched for Musculoskeletal Infection Society criteria. J Bone Joint Surg Am. 2014;96(22):1917-1920.
17. Dempsey KE, Riggio MP, Lennon A, et al. Identification of bacteria on the surface of clinically infected and non-infected prosthetic hip joints removed during revision arthroplasties by 16S rRNA gene sequencing and by microbiological culture. Arthritis Res Ther. 2007;9(3):R46.
18. Gallo J, Kolar M, Dendis M, et al. Culture and PCR analysis of joint fluid in the diagnosis of prosthetic joint infection. New Microbiol. 2008;31(1):97-104.
19. Marin M, Garcia-Lechuz JM, Alonso P, et al. Role of universal 16S rRNA gene PCR and sequencing in diagnosis of prosthetic joint infection. J Clin Microbiol. 2012;50(3):583-589.
20. Jacovides CL, Kreft R, Adeli B, Hozack B, Ehrlich GD, Parvizi J. Successful identification of pathogens by polymerase chain reaction (PCR)-based electron spray ionization time-of-flight mass spectrometry (ESI-TOF-MS) in culture-negative periprosthetic joint infection. J Bone Joint Surg Am. 2012;94(24):2247-2254.
21. Hartley JC, Harris KA. Molecular techniques for diagnosing prosthetic joint infections. J Antimicrob Chemother. 2014;69(suppl 1):i21-i24.
22. Zappe B, Graf S, Ochsner PE, Zimmerli W, Sendi P. Propionibacterium spp. in prosthetic joint infections: a diagnostic challenge. Arch Orthop Trauma Surg. 2008;128(10):1039-1046.
23. Rasouli MR, Harandi AA, Adeli B, Purtill JJ, Parvizi J. Revision total knee arthroplasty: infection should be ruled out in all cases. J Arthroplasty. 2012;27(6):1239-1243.e1-e2.
24. Hunt RW, Bond MJ, Pater GD. Psychological responses to cancer: a case for cancer support groups. Community Health Stud. 1990;14(1):35-38.
25. Kurtz SM, Lau E, Schmier J, Ong KL, Zhao K, Parvizi J. Infection burden for hip and knee arthroplasty in the United States. J Arthroplasty. 2008;23(7):984-991.
26. Vandercam B, Jeumont S, Cornu O, et al. Amplification-based DNA analysis in the diagnosis of prosthetic joint infection. J Mol Diagn. 2008;10(6):537-543.
1. Maradit Kremers H, Larson DR, Crowson CS, et al. Prevalence of total hip and knee replacement in the United States. J Bone Joint Surg Am. 2015;97(17):1386-1397.
2. Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg Am. 2007;89(4):780-785.
3. Sharkey PF, Lichstein PM, Shen C, Tokarski AT, Parvizi J. Why are total knee arthroplasties failing today—has anything changed after 10 years? J Arthroplasty. 2014;29(9):1774-1778.
4. Butler-Wu SM, Burns EM, Pottinger PS, et al. Optimization of periprosthetic culture for diagnosis of Propionibacterium acnes prosthetic joint infection. J Clin Microbiol. 2011;49(7):2490-2495.
5. Frangiamore SJ, Saleh A, Grosso MJ, et al. α-Defensin as a predictor of periprosthetic shoulder infection. J Shoulder Elbow Surg. 2015;24(7):1021-1027.
6. Deirmengian C, Kardos K, Kilmartin P, Cameron A, Schiller K, Parvizi J. Combined measurement of synovial fluid α-defensin and C-reactive protein levels: highly accurate for diagnosing periprosthetic joint infection. J Bone Joint Surg Am. 2014;96(17):1439-1445.
7. Bingham J, Clarke H, Spangehl M, Schwartz A, Beauchamp C, Goldberg B. The alpha defensin-1 biomarker assay can be used to evaluate the potentially infected total joint arthroplasty. Clin Orthop Relat Res. 2014;472(12):4006-4009.
8. Deirmengian C, Kardos K, Kilmartin P, et al. The alpha-defensin test for periprosthetic joint infection outperforms the leukocyte esterase test strip. Clin Orthop Relat Res. 2015;473(1):198-203.
9. Frangiamore SJ, Gajewski ND, Saleh A, Farias-Kovac M, Barsoum WK, Higuera CA. α-Defensin accuracy to diagnose periprosthetic joint infection—best available test? J Arthroplasty. 2016;31(2):456-460.
10. Frangiamore SJ, Saleh A, Kovac MF, et al. Synovial fluid interleukin-6 as a predictor of periprosthetic shoulder infection. J Bone Joint Surg Am. 2015;97(1):63-70.
11. Lenski M, Scherer MA. Synovial IL-6 as inflammatory marker in periprosthetic joint infections. J Arthroplasty. 2014;29(6):1105-1109.
12. Randau TM, Friedrich MJ, Wimmer MD, et al. Interleukin-6 in serum and in synovial fluid enhances the differentiation between periprosthetic joint infection and aseptic loosening. PLoS One. 2014;9(2):e89045.
13. Guenther D, Kokenge T, Jacobs O, et al. Excluding infections in arthroplasty using leucocyte esterase test. Int Orthop. 2014;38(11):2385-2390.
14. Wetters NG, Berend KR, Lombardi AV, Morris MJ, Tucker TL, Della Valle CJ. Leukocyte esterase reagent strips for the rapid diagnosis of periprosthetic joint infection. J Arthroplasty. 2012;27(8 suppl):8-11.
15. Nelson GN, Paxton ES, Narzikul A, Williams G, Lazarus MD, Abboud JA. Leukocyte esterase in the diagnosis of shoulder periprosthetic joint infection. J Shoulder Elbow Surg. 2015;24(9):1421-1426.
16. Tischler EH, Cavanaugh PK, Parvizi J. Leukocyte esterase strip test: matched for Musculoskeletal Infection Society criteria. J Bone Joint Surg Am. 2014;96(22):1917-1920.
17. Dempsey KE, Riggio MP, Lennon A, et al. Identification of bacteria on the surface of clinically infected and non-infected prosthetic hip joints removed during revision arthroplasties by 16S rRNA gene sequencing and by microbiological culture. Arthritis Res Ther. 2007;9(3):R46.
18. Gallo J, Kolar M, Dendis M, et al. Culture and PCR analysis of joint fluid in the diagnosis of prosthetic joint infection. New Microbiol. 2008;31(1):97-104.
19. Marin M, Garcia-Lechuz JM, Alonso P, et al. Role of universal 16S rRNA gene PCR and sequencing in diagnosis of prosthetic joint infection. J Clin Microbiol. 2012;50(3):583-589.
20. Jacovides CL, Kreft R, Adeli B, Hozack B, Ehrlich GD, Parvizi J. Successful identification of pathogens by polymerase chain reaction (PCR)-based electron spray ionization time-of-flight mass spectrometry (ESI-TOF-MS) in culture-negative periprosthetic joint infection. J Bone Joint Surg Am. 2012;94(24):2247-2254.
21. Hartley JC, Harris KA. Molecular techniques for diagnosing prosthetic joint infections. J Antimicrob Chemother. 2014;69(suppl 1):i21-i24.
22. Zappe B, Graf S, Ochsner PE, Zimmerli W, Sendi P. Propionibacterium spp. in prosthetic joint infections: a diagnostic challenge. Arch Orthop Trauma Surg. 2008;128(10):1039-1046.
23. Rasouli MR, Harandi AA, Adeli B, Purtill JJ, Parvizi J. Revision total knee arthroplasty: infection should be ruled out in all cases. J Arthroplasty. 2012;27(6):1239-1243.e1-e2.
24. Hunt RW, Bond MJ, Pater GD. Psychological responses to cancer: a case for cancer support groups. Community Health Stud. 1990;14(1):35-38.
25. Kurtz SM, Lau E, Schmier J, Ong KL, Zhao K, Parvizi J. Infection burden for hip and knee arthroplasty in the United States. J Arthroplasty. 2008;23(7):984-991.
26. Vandercam B, Jeumont S, Cornu O, et al. Amplification-based DNA analysis in the diagnosis of prosthetic joint infection. J Mol Diagn. 2008;10(6):537-543.
