The aim of this study was to assess the role of synovial C-reactive protein (CRP) in the diagnosis of chronic periprosthetic hip infection. We prospectively collected synovial fluid from 89 patients undergoing revision hip arthroplasty and measured synovial CRP, serum CRP, erythrocyte sedimentation rate (ESR), synovial white blood cell (WBC) count and synovial percentages of polymorphonuclear neutrophils (PMN). Patients were classified as septic or aseptic by means of clinical, microbiological, serum and synovial fluid findings. The high viscosity of the synovial fluid precluded the analyses in nine patients permitting the results in 80 patients to be studied. There was a significant difference in synovial CRP levels between the septic (n = 21) and the aseptic (n = 59) cohort. According to the receiver operating characteristic curve, a synovial CRP threshold of 2.5 mg/l had a sensitivity of 95.5% and specificity of 93.3%. The area under the curve was 0.96. Compared with serum CRP and ESR, synovial CRP showed a high diagnostic value. According to these preliminary results, synovial CRP may be a useful parameter in diagnosing chronic periprosthetic hip infection. Cite this article: Bone Joint J 2015; 97-B:173–6

The aim of this study was to determine whether the level of circulating C-reactive protein (CRP) before treatment predicted overall disease-specific survival and local tumour control in patients with a sarcoma of bone. We retrospectively reviewed 318 patients who presented with a primary sarcoma of bone between 2003 and 2010. Those who presented with metastases and/or local recurrence were excluded. Elevated CRP levels were seen in 84 patients before treatment; these patients had a poorer disease-specific survival (57% at five years) than patients with a normal CRP (79% at five years) (p < 0.0001). They were also less likely to be free of recurrence (71% at five years) than patients with a normal CRP (79% at five years) (p = 0.04). Multivariate analysis showed the pre-operative CRP level to be an independent predictor of survival and local control. Patients with a Ewing’s sarcoma or chondrosarcoma who had an elevated CRP before their treatment started had a significantly poorer disease-specific survival than patients with a normal CRP (p = 0.02 and p < 0.0001, respectively). Patients with a conventional osteosarcoma and a raised CRP were at an increased risk of poorer local control. We recommend that CRP levels are measured routinely in patients with a suspected sarcoma of bone as a further prognostic indicator of survival. Cite this article: Bone Joint J 2013;95-B:411–18

Aims. The aim of this study was to determine the prevalence and characteristics of C-reactive protein (CRP)-negative prosthetic joint infection (PJI) and evaluate the influence of the type of infecting organism on the CRP level. Patients and Methods. A retrospective analysis of all PJIs affecting the hip or knee that were diagnosed in our institution between March 2013 and December 2016 was performed. A total of 215 patients were included. Their mean age was 71 years (. sd. 11) and there were 118 women (55%). The median serum CRP levels were calculated for various species of organism and for patients with acute postoperative, acute haematogenous, and chronic infections. These were compared using the Kruskal–Wallis test, adjusting for multiple comparisons with Dunn’s test. The correlation between the number of positive cultures and serum CRP levels was estimated using Spearman correlation coefficient. Results. Preoperative CRP levels were normal (< 10 mg/l) in 77 patients (35.8%) with positive cultures. Low-virulent organisms were isolated in 66 PJIs (85.7%) with normal CRP levels. When grouping organisms by species, patients with an infection caused by Propionibacterium spp., coagulase-negative staphylococci (CNS), and Enterococcus faecalis had significantly lower median serum CRP levels (5.4 mg/l, 12.2 mg/l, and 23.7 mg/l, respectively), compared with those with infections caused by Staphylococcus aureus and Streptococcus spp. (194 mg/l and 89.3 mg/l, respectively; p < 0.001). Those with a chronic PJI had statistically lower median serum CRP levels (10.6 mg/l) than those with acute postoperative and acute haematogenous infections (83.7 mg/l and 149.4 mg/l, respectively; p < 0.001). There was a significant correlation between the number of positive cultures and serum CRP levels (Spearman correlation coefficient, 0.456; p < 0.001). Conclusion. The CRP level alone is not accurate as a screening tool for PJI and may yield high false-negative rates, especially if the causative organism has low virulence. Aspiration of the joint should be used for the diagnosis of PJI in patients with a chronic painful arthroplasty, irrespective of CRP level. Cite this article: Bone Joint J 2018;100-B:1482–86

We analysed the serum C-reactive protein level, synovial fluid obtained by joint aspiration and five synovial biopsies from 145 knee replacements prior to revision to assess the value of these parameters in diagnosing late peri-prosthetic infection. Five further synovial biopsies were used for histological analysis. Samples were also obtained during the revision and incubated and analysed in an identical manner for 14 days. A total of 40 total knee replacements were found to be infected (prevalence 27.6%). The aspiration technique had a sensitivity of 72.5% (95% confidence interval (CI) 58.7 to 86.3), a specificity of 95.2% (95% CI 91.2 to 99.2), a positive predictive value of 85.3% (95% CI 73.4 to 100), a negative predictive value of 90.1% (95% CI 84.5 to 95.7) and an accuracy of 89%. The biopsy technique had a sensitivity of 100%, a specificity of 98.1% (95% CI 95.5 to 100), a positive predictive value of 95.2% (95% CI 88.8 to 100), a negative predictive value of 100% and an accuracy of 98.6%. C-reactive protein with a cut-off-point of 13.5 mg/l had a sensitivity of 72.5% (95% CI 58.7 to 86.3), a specificity of 80.9% (95% CI 73.4 to 88.4), a positive predictive value of 59.2% (95% CI 45.4 to 73.0), a negative predictive value of 88.5% (95% 81.0 to 96.0 CI) and an accuracy of 78.1%. We found that biopsy was superior to joint aspiration and C-reactive protein in the diagnosis of late peri-prosthetic infection of total knee replacements

In 50 patients with non-infected total hip arthroplasties (THA), 233 C-reactive protein (CRP) values were obtained over a three-year period. Six of these 50 patients occasionally had CRP values of over 20 mg/l. The erythrocyte sedimentation rate (ESR) and CRP concentration were measured in 23 patients with deep infections of THA before revision. In 11 patients the infections were caused by coagulase-negative staphylococci. CRP exceeded 20 mg/l in 18 patients and the ESR was more than 30 mm/hr in 14. In only one infected patient were both CRP and ESR below these levels. All of 33 patients with non-septic loosening had CRP less than 20 mg/l and ESR less than 30 mm/hr before revision. C-reactive protein seems to be a valuable supplement to the ESR in the monitoring of infection after THA

We studied the changes in plasma viscosity and C-reactive protein to establish normal values after total hip or knee arthroplasty. Viscosity decreased from 1.68 (+/- 0.017) to 1.57 (+/- 0.014) on the first postoperative day and thereafter rose to 1.60 (+/- 0.019), 1.75 (+/- 0.015), and 1.74 (+/- 0.011) on the third, seventh and fourteenth days respectively. Six to eight weeks after operation it had returned to pre-operative levels. A viscosity above the upper limit of the laboratory range, obtained more than two months after operation, may be considered as abnormal. The C-reactive protein level increased significantly on the first postoperative day and then decreased from a peak on the second day, attaining nearly normal levels at six to eight weeks after operation. It may be a more sensitive indicator of deep postoperative infection than plasma viscosity

Our study has determined the response of C-reactive protein (CRP) after total knee replacement (TKR). The peak level occurs on the second postoperative day and is significantly greater than that after total hip replacement (THR). The level returns to normal at similar times after both procedures. The physiological response to TKR as measured by the area under the CRP/ time curve is significantly greater than that after THR. Rising CRP levels after the third postoperative day may indicate a complication of surgery such as infection

Any operation induces an elevation in the level of serum C-reactive protein (CRP). After hip and knee arthroplasty the maximal values are seen on the second and third postoperative days, after which the CRP decreases rapidly. There is no difference between patients with cemented or uncemented prostheses. Major postoperative complications may cause a further increase in CRP levels at one and two weeks

We measured the serum concentration of C-reactive protein (CRP) by a high-sensitive method in patients with lumbar disc herniation. There were 48 patients in the study group and 53 normal controls. The level and type of herniation were evaluated. The clinical data including the neurological findings, the angle of straight leg raising and post-operative recovery as measured by the Japanese Orthopaedic Association (JOA) score, were recorded. The high-sensitive CRP (hs-CRP) was measured by an ultrasensitive latex-enhanced immunoassay. The mean hs-CRP concentration was 0.056 ± 0.076 mg/dl in the patient group and 0.017 ± 0.021 mg/dl in the control group. The difference was statistically significant (p = 0.006). There was no other correlation between the hs-CRP concentration and the level and type of herniation, or the pre-operative clinical data. A positive correlation was found between the concentration of hs-CRP before operation and the JOA score after. Those with a higher concentration of hs-CRP before operation showed a poorer recovery after. The significantly high concentration of serum hs-CRP might indicate a systemic inflammatory response to impingement of the nerve root caused by disc herniation and might be a predictor of recovery after operation

Serial serum C-reactive protein (CRP) measurements were made, for three weeks, in 42 consecutive patients with solitary tibial fractures. The CRP response was related to the treatment: lower values were observed in 27 patients treated conservatively than in 15 operated patients. Open reduction and plating resulted in a greater response than closed intramedullary nailing. The timing of the CRP response was related to the timing of the treatment: the highest values were usually recorded two days after admission or operation. The timing of the operation did not affect the degree of CRP response. Neither the site, nor the type of fracture, nor the age of the patient played any role. Awareness of these natural CRP responses after fractures may help in the diagnosis of early post-traumatic and postoperative complications, especially infections

Aims. To assess the diagnostic value of C-reactive protein (CRP), leucocyte count (LC), and erythrocyte sedimentation rate (ESR) in late fracture-related infection (FRI). Materials and Methods. PubMed, Embase, and Cochrane databases were searched focusing on the diagnostic value of CRP, LC, and ESR in late FRI. Sensitivity and specificity combinations were extracted for each marker. Average estimates were obtained using bivariate mixed effects models. Results. A total of 8284 articles were identified but only six were suitable for inclusion. Sensitivity of CRP ranged from 60.0% to 100.0% and specificity from 34.3% to 85.7% in all publications considered. Five articles were pooled for meta-analysis, showing a sensitivity and specificity of 77.0% and 67.9%, respectively. For LC, this was 22.9% to 72.6%, and 73.5% to 85.7%, respectively, in five articles. Four articles were pooled for meta-analysis, resulting in a 51.7% sensitivity and 67.1% specificity. For ESR, sensitivity and specificity ranged from 37.1% to 100.0% and 59.0% to 85.0%, respectively, in five articles. Three articles were pooled in meta-analysis, showing a 45.1% sensitivity and 79.3% specificity. Four articles analyzed the value of combined inflammatory markers, reporting an increased diagnostic accuracy. These results could not be pooled due to heterogeneity. Conclusion. The serum inflammatory markers CRP, LC, and ESR are insufficiently accurate to diagnose late FRI, but they may be used as a suggestive sign in its diagnosis

Aims. The aims of this study were to increase the diagnostic accuracy of the analysis of synovial fluid in the differentiation of prosthetic joint infection (PJI) by the addition of inexpensive biomarkers such as the levels of C-reactive protein (CRP), adenosine deaminase (ADA), alpha-2-macrogloblulin (α2M) and procalcitonin. Patients and Methods. Between January 2013 and December 2015, synovial fluid and removed implants were requested from 143 revision total joint arthroplasties. A total of 55 patients met inclusion criteria of the receipt of sufficient synovial fluid, tissue samples and removed implants for analysis. The diagnosis of PJI followed the definition from a recent International Consensus Meeting to create two groups of patients; septic and aseptic. Using receiver operating characteristic curves we determined the cutoff values and diagnostic accuracy for each marker. Results. There were 23 PJIs and 32 patients with aseptic loosening. The levels of total leucocyte count, proportion of polymorphonuclear leucocytes (PMNs), CRP, ADA and α2M in the synovial fluid were all significantly higher in those with a PJI than in those with aseptic loosening. The levels of procalcitonin were comparable in the two groups. Cutoff values for the optimal performance in the diagnosis of infection were: total leucocyte count > 1463 cells/μL (sensitivity (Sens) 100%, specificity (Spec) 71.9%, positive predictive value (PPV) 71.9%, negative predictive value (NPV) 100%); proportion of PMNs > 81% (Sens 78.3%, Spec 75.0%, PPV 69.2%, NPV 82.8%); CRP > 6.7mg/L (Sens 78.3%, Spec 93.8%, PPV 90.0%, NPV 85.7%); ADA > 61U/L (Sens 78.3%, Spec 96.9%, PPV 94.7%, NPV 86.1%) and α2M > 958 mg/L (Sens 47.8%, Spec 96.9%, PPV 91.7%, NPV 72.1%). The addition of a raised level of CRP or ADA to the total leukocyte count increased the specificity: total leukocyte count > 1463 cells/μL and CRP > 6.7mg/L (Sens 78.3%, Spec 100%, PPV 100%, NPV 86.5%) or with ADA > 61U/L (Sens 78.3%, Spec 96.9%, PPV 94.7%, NPV 86.1%). . Conclusion. The total leucocyte count in the synovial fluid offers great negative predictive value in the diagnosis of PJI and the addition of more specific markers such as CRP and ADA improves the positive predictive value. Thus the addition of simple and inexpensive markers to the measurement of the leucocyte count in the synovial fluid may reduce the number of equivocal results which demand more expensive investigation. Cite this article: Bone Joint J 2017;99-B:351–7

Aims

Serum inflammatory parameters are widely used to aid in diagnosing a periprosthetic joint infection (PJI). Due to their limited performances in the literature, novel and more accurate biomarkers are needed. Serum albumin-to-globulin ratio (AGR) and serum CRP-to-albumin ratio (CAR) have previously been proposed as potential new parameters, but results were mixed. The aim of this study was to assess the diagnostic accuracy of AGR and CAR in diagnosing PJI and to compare them to the established and widely used marker CRP.

This prospective study evaluates the role of new laboratory markers in the diagnosis of deep implant infection in 78 patients (41 men and 37 women) with a revision total knee or hip replacement. The mean age at the time of operation was 64.0 years (19 to 90). Intra-operative cultures showed that 21 patients had a septic and 57 an aseptic total joint replacement. The white blood cell count, the erythrocyte sedimentation rate and levels of C-reactive protein, interleukin-6, procalcitonin and tumour necrosis factor (TNF)-α were measured in blood samples before operation. The diagnostic cut-off values were determined by Received Operating Characteristic curve analysis. C-reactive protein (> 3.2 md/dl) and interleukin-6 (> 12 pg/ml) have the highest sensitivity (0.95). Interleukin-6 is less specific than C-reactive protein (0.87 vs 0.96). Combining C-reactive protein and interleukin-6 identifies all patients with deep infection of the implant. Procalcitonin (> 0.3 ng/ml) and TNF-α (> 40 ng/ml) are very specific (0.98 vs 0.94) but have a low sensitivity (0.33 vs 0.43). The combination of C-reactive protein and interleukin-6 measurement provide excellent screening tests for infection of a deep implant. A highly specific marker such as procalcitonin and pre-operative aspiration of the joint might be useful in identifying patients with true positive C-reactive protein and/or interleukin-6 levels

The aim of this study was to determine whether the high-sensitivity modified Glasgow prognostic score (Hs-mGPS) could predict the disease-specific survival and oncological outcome in adult patients with non-metastatic soft-tissue sarcoma before treatment. A total of 139 patients treated between 2001 and 2012 were retrospectively reviewed. The Hs-mGPS varied between 0 and 2. Patients with a score of 2 had a poorer disease-specific survival than patients with a score of 0 (p < 0.001). The estimated five-year rate of disease-specific survival for those with a score of 2 was 0%, compared with 85.4% (95% CI 77.3 to 93.5) for those with a score of 0. Those with a score of 2 also had a poorer disease-specific survival than those with a score of 1 (75.3%, 95% CI 55.8 to 94.8; p < 0.001). Patients with a score of 2 also had a poorer event-free rate than those with a score of 0 (p < 0.001). Those with a score of 2 also had a poorer event-free survival than did those with a score of 1 (p = 0.03). A multivariate analysis showed that the Hs-mGPS remained an independent predictor of survival and recurrence. The Hs-mGPS could be a useful prognostic marker in patients with a soft-tissue sarcoma.

Cite this article: Bone Joint J 2015; 97-B:847–52.

Objectives. Prosthetic joint infection (PJI) diagnosis is a major challenge in orthopaedics, and no reliable parameters have been established for accurate, preoperative predictions in the differential diagnosis of aseptic loosening or PJI. This study surveyed factors in synovial fluid (SF) for improving PJI diagnosis. Methods. We enrolled 48 patients (including 39 PJI and nine aseptic loosening cases) who required knee/hip revision surgery between January 2016 and December 2017. The PJI diagnosis was established according to the Musculoskeletal Infection Society (MSIS) criteria. SF was used to survey factors by protein array and enzyme-linked immunosorbent assay to compare protein expression patterns in SF among three groups (aseptic loosening and first- and second-stage surgery). We compared routine clinical test data, such as C-reactive protein level and leucocyte number, with potential biomarker data to assess the diagnostic ability for PJI within the same patient groups. Results. Cut-off values of 1473 pg/ml, 359 pg/ml, and 8.45 pg/ml were established for interleukin (IL)-16, IL-18, and cysteine-rich with EGF-like domains 2 (CRELD2), respectively. Receiver operating characteristic curve analysis showed that these factors exhibited an accuracy of 1 as predictors of PJI. These factors represent potential biomarkers for decisions associated with prosthesis reimplantation based on their ability to return to baseline values following the completion of debridement. Conclusion. IL-16, IL-18, and CRELD2 were found to be potential biomarkers for PJI diagnosis, with SF tests outperforming blood tests in accuracy. These factors could be useful for assessing successful debridement based on their ability to return to baseline values following the completion of debridement. Cite this article: M-F. Chen, C-H. Chang, L-Y. Yang, P-H. Hsieh, H-N. Shih, S. W. N. Ueng, Y. Chang. Synovial fluid interleukin-16, interleukin-18, and CRELD2 as novel biomarkers of prosthetic joint infections. Bone Joint Res 2019;8:179–188. DOI: 10.1302/2046-3758.84.BJR-2018-0291.R1

Aims. Prosthetic joint infection (PJI) and aseptic loosening in total hip arthroplasty (THA) can present with pain and osteolysis. The Musculoskeletal Infection Society (MSIS) has provided criteria for the diagnosis of PJI. The aim of our study was to analyze the utility of F18-fluorodeoxyglucose (FDG) positron emission tomography (PET) CT scan in the preoperative diagnosis of septic loosening in THA, based on the current MSIS definition of prosthetic joint infection. Patients and Methods. A total of 130 painful unilateral cemented THAs with a mean follow-up of 5.17 years (. sd. 1.12) were included in this prospective study. The mean patient age was 67.5 years (. sd. 4.85). Preoperative evaluation with inflammatory markers, aspiration, and an F18 FDG PET scan were performed. Diagnostic utility tests were also performed, based on the MSIS criteria for PJI and three samples positive on culture alone. Results. The mean erythrocyte sedimentation rate, C-reactive protein, and white cell count were 47.83 mm/hr, 25.21 mg/l, and 11.05 × 10. 9. /l, respectively. The sensitivity, specificity, accuracy, negative predictive value, and false-positive rate of FDG PET compared with MSIS criteria were 94.87%, 38.46 %, 56.38%, 94.59 %, and 60.21%, respectively. The false-positive rate of FDG PET compared with culture alone was 77.4%. Conclusion. FDG PET has a definitive role in the preoperative evaluation of suspected PJI. This the first study to evaluate its utility based on MSIS criteria and compare it with microbiology results alone. However, FDG PET has a high false-positive rate. Therefore, we suggest that F18 FDG PET is useful in confirming the absence of infection, but if positive, may not be confirmatory of PJI. Cite this article: Bone Joint J 2019;101-B:910–914

Aims. The aims of this study were to report the efficacy of revision surgery for patients with co-infective bacterial and fungal prosthetic joint infections (PJIs) presenting to a single institution, and to identify prognostic factors that would guide management. Patients and Methods. A total of 1189 patients with a PJI were managed in our bone infection service between 2006 and 2015; 22 (1.85%) with co-infective bacterial and fungal PJI were included in the study. There were nine women and 13 men, with a mean age at the time of diagnosis of 64.5 years (47 to 83). Their mean BMI was 30.9 kg/m. 2. (24 to 42). We retrospectively reviewed the outcomes of these PJIs, after eight total hip arthroplasties and 14 total knee arthroplasties. The mean clinical follow-up was 4.1 years (1.4 to 8.8). Results. The median number of risk factors for PJI was 5.5 (interquartile range (IQR) 3.25 to 7.25). All seven patients who initially underwent debridement and implant retention (DAIR) had a recurrent infection that led to a staged revision. All 22 patients underwent the first of a two-stage revision. None of the nine patients with negative tissue cultures at the second stage had a recurrent infection. The rate of recurrent infection was significantly higher in the presence of multidrug-resistant bacteria (p = 0.007), a higher C-reactive protein (CRP) at the time of presentation (p = 0.032), and a higher number of co-infective bacterial organisms (p = 0.041). The overall rate of eradication of infection after two and five years was 50% (95% confidence interval (CI) 32.9 to 75.9) and 38.9% (95% CI 22.6 to 67), respectively. Conclusion. The risk of failure to eradicate infection with the requirement of amputation associated with this diagnosis is much higher than in patients with PJI without bacterial and fungal co-infection, and this risk is heightened when the fungal organism is joined by polymicrobial and multidrug-resistant bacterial organisms. Cite this article: Bone Joint J 2019;101-B:582–588

Objectives. The diagnosis of periprosthetic joint infection (PJI) is difficult and requires a battery of tests and clinical findings. The purpose of this review is to summarize all current evidence for common and new serum biomarkers utilized in the diagnosis of PJI. Methods. We searched two literature databases, using terms that encompass all hip and knee arthroplasty procedures, as well as PJI and statistical terms reflecting diagnostic parameters. The findings are summarized as a narrative review. Results. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were the two most commonly published serum biomarkers. Most evidence did not identify other serum biomarkers that are clearly superior to ESR and CRP. Other serum biomarkers have not demonstrated superior sensitivity and have failed to replace CRP and ESR as first-line screening tests. D-dimer appears to be a promising biomarker, but more research is necessary. Factors that influence serum biomarkers include temporal trends, stage of revision, and implant-related factors (metallosis). Conclusion. Our review helped to identify factors that can influence serum biomarkers’ level changes; the recognition of such factors can help improve their diagnostic utility. As such, we cannot rely on ESR and CRP alone for the diagnosis of PJI prior to second-stage reimplantation, or in metal-on-metal or corrosion cases. The future of serum biomarkers will likely shift towards using genomics and proteomics to identify proteins transcribed via messenger RNA in response to infection and sepsis. Cite this article: A. Saleh, J. George, M. Faour, A. K. Klika, C. A. Higuera. Serum biomarkers in periprosthetic joint infections. Bone Joint Res 2018;7:85–93. DOI: 10.1302/2046-3758.71.BJR-2017-0323

Aims. The aim of this study was to compare the results of 16S/28S rRNA sequencing with the erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) level, and synovial fluid analysis in the diagnosis of prosthetic joint infection (PJI). Patients and Methods. Between September 2015 and August 2016, 214 consecutive patients were enrolled. In the study population, there were 25 patients with a PJI and 189 controls. Of the PJI patients, 14 (56%) were women, and the mean age at the time of diagnosis was 65 years (38 to 83). The ESR and CRP levels were measured, and synovial fluid specimens were collected prospectively. Synovial fluid was subjected to reverse transcription polymerase chain reaction (RT-PCR)/sequence analysis targeting the 16S/28S rRNA, and to conventional culture. Laboratory personnel who were blind to the clinical information performed all tests. The diagnosis of PJI was based on the criteria of the Musculoskeletal Infection Society. Results. A total of 25 patients had a confirmed PJI. In 20 cases of monomicrobial PJI, the PCR products could be perfectly matched with the 16S/28S rRNA genes specific for different species of bacteria provided by sequence analysis. Of the five polymicrobial cases of PJI, 16S/28S rRNA PCR sequence analysis failed to identify the concordant bacteria species. In the 189 control patients, there was one false-positive RT-PCR result. The sensitivity and specificity of the molecular diagnosis method were 100% (95% confidence interval (CI) 85.7 to 100) and 99.5% (95% CI 97.1 to 99.9), respectively, whereas the positive and negative predictive values of PCR were 96.1% (95% CI 79.6 to 99.9) and 100% (95% CI 98.1 to 100), respectively. The PCR results were significantly better than serological diagnostic methods (p = 0.004 and p = 0.010 for ESR and CRP, respectively), the synovial fluid white blood cell (WBC) count (p = 0.036), and percentage of polymorphonuclear cells (PMN%) (p = 0.014). Conclusion. Stepwise RT-PCR and sequence analysis of the 16S/28S rRNA carried out under stringent laboratory conditions achieved highly sensitive and specific results for the differentiation between aseptic and septic joints undergoing arthroplasty. Sequence analysis successfully identified bacterial strains in monomicrobial infections but failed to identify molecular targets in polymicrobial infections. Further refinement of the protocols to identify the bacteria in polymicrobial infections is needed. Cite this article: Bone Joint J 2018;100-B:1345–51