Aims. The aim of this study was to determine the diagnostic accuracy of α defensin (AD) lateral flow assay (LFA) and enzyme-linked immunosorbent assay (ELISA) tests for periprosthetic joint infection (PJI) in comparison to conventional synovial white blood cell (WBC) count and polymorphonuclear neutrophil percentage (PMN%) analysis. Methods. Patients undergoing joint aspiration for evaluation of pain after total knee arthroplasty (TKA) or total hip arthroplasty (THA) were considered for inclusion. Synovial fluids from 99 patients (25 THA and 74 TKA) were analyzed by WBC count and PMN% analysis, AD LFA, and AD ELISA. WBC and PMN% cutoffs of ≥ 1,700 cells/mm. 3. and ≥ 65% for TKA and ≥ 3,000 cells/mm. 3. and ≥ 80% for THA were used, respectively. A panel of three physicians, all with expertise in orthopaedic infections and who were blinded to the results of AD tests, independently reviewed patient data to diagnose subjects as with or without PJI. Consensus PJI classification was used as the reference standard to evaluate test performances. Results were compared using McNemar’s test and area under the receiver operating characteristic curve (AUC) analysis. Results. Expert consensus classified 18 arthroplasies as having failed due to PJI and 81 due to aseptic failure. Using these classifications, the calculated sensitivity and specificity of AD LFA was 83.3% (95% confidence interval (CI) 58.6 to 96.4) and 93.8% (95% CI 86.2 to 98.0), respectively. Sensitivity and specificity of AD ELISA was 83.3% (95% CI 58.6 to 96.4) and 96.3% (95% CI 89.6 to 99.2), respectively. There was no statistically significant difference between sensitivity (p = 1.000) or specificity (p = 0.157) of the two AD assays. AUC for AD LFA was 0.891. In comparison, AUC for synovial WBC count, PMN%, and the combination of the two values was 0.821 (sensitivity p = 1.000, specificity p < 0.001), 0.886 (sensitivity p = 0.317, specificity p = 0.011), and 0.926 (sensitivity p = 0.317, specificity p = 0.317), respectively. Conclusion. The diagnostic accuracy of synovial AD for PJI diagnosis is comparable and not statistically superior to that of synovial WBC count plus PMN% combined. Cite this article: Bone Joint J 2021;103-B(6):1119–1126

Aims. Synovial fluid white blood cell (WBC) count and percentage of polymorphonuclear cells (%PMN) are elevated at periprosthetic joint infection (PJI). Leucocytes produce different interleukins (IL), including IL-6, so we hypothesized that synovial fluid IL-6 could be a more accurate predictor of PJI than synovial fluid WBC count and %PMN. The main aim of our study was to compare the predictive performance of all three diagnostic tests in the detection of PJI. Methods. Patients undergoing total hip or knee revision surgery were included. In the perioperative assessment phase, synovial fluid WBC count, %PMN, and IL-6 concentration were measured. Patients were labeled as positive or negative according to the predefined cut-off values for IL-6 and WBC count with %PMN. Intraoperative samples for microbiological and histopathological analysis were obtained. PJI was defined as the presence of sinus tract, inflammation in histopathological samples, and growth of the same microorganism in a minimum of two or more samples out of at least four taken. Results. In total, 49 joints in 48 patients (mean age 68 years (SD 10; 26 females (54%), 25 knees (51%)) were included. Of these 11 joints (22%) were infected. The synovial fluid WBC count and %PMN predicted PJI with sensitivity, specificity, accuracy, PPV, and NPV of 82%, 97%, 94%, 90%, and 95%, respectively. Synovial fluid IL-6 predicted PJI with sensitivity, specificity, accuracy, PPV, and NPV of 73%, 95%, 90%, 80%, and 92%, respectively. A comparison of predictive performance indicated a strong agreement between tests. Conclusions. Synovial fluid IL-6 is not superior to synovial fluid WBC count and %PMN in detecting PJI. Level of Evidence: Therapeutic Level II. Cite this article: Bone Jt Open 2020;1-12:737–742

Aims. Calprotectin (CLP) is produced in neutrophils and monocytes and released into body fluids as a result of inflammation or infection. The aim of this study was to evaluate the utility of blood and synovial CLP in the diagnosis of chronic periprosthetic joint infection (PJI). Methods. Blood and synovial fluid samples were collected prospectively from 195 patients undergoing primary or revision hip and knee arthroplasty. Patients were divided into five groups: 1) primary total hip and knee arthroplasty performed due to idiopathic osteoarthritis (OA; n = 60); 2) revision hip and knee arthroplasty performed due to aseptic failure of the implant (AR-TJR; n = 40); 3) patients with a confirmed diagnosis of chronic PJI awaiting surgery (n = 45); 4) patients who have finished the first stage of the PJI treatment with the use of cemented spacer and were qualified for replantation procedure (SR-TJR; n = 25), and 5) patients with rheumatoid arthritis undergoing primary total hip and knee arthroplasty (RA; n = 25). CLP concentrations were measured quantitatively in the blood and synovial fluid using an immunoturbidimetric assay. Additionally, blood and synovial CRP, blood interleukin-6 (IL-6), and ESR were measured, and a leucocyte esterase (LE) strip test was performed. Results. Patients with PJI had higher CLP concentrations than those undergoing aseptic revision in blood (median PJI 2.14 mg/l (interquartile range (IQR) 1.37 to 3.56) vs AR-TJR 0.66 mg/l (IQR 0.3 to 0.83); p < 0.001) and synovial fluid samples (median PJI 20.46 mg/l (IQR 14.3 to 22.36) vs AR-TJR 0.7 mg/l (IQR 0.41 to 0.95); p < 0.001). With a cut-off value of 1.0 mg/l, blood CLP showed a sensitivity, specificity, positive predictive value, and negative predictive value of 93.3%, 87.5%, 89.4%, and 92.1%, respectively. For synovial fluid with a cut-off value of 1.5 mg/l, these were 95.6%, 95%, 95.5%, and 95%, respectively. Conclusion. This small study suggests that synovial and blood CLP are useful markers in chronic PJI diagnosis with similar or higher sensitivity and specificity than routinely used markers such as CRP, ESR, IL-6, and LE. CLP was not useful to differentiate patients with PJI from those with rheumatoid arthritis. Cite this article: Bone Joint J 2021;103-B(1):46–55

Aims. Prosthetic joint infection (PJI) remains a major clinical challenge. Neutrophil CD64 index, Fc-gamma receptor 1 (FcγR1), plays an important role in mediating inflammation of bacterial infections and therefore could be a valuable biomarker for PJI. The aim of this study is to compare the neutrophil CD64 index in synovial and blood diagnostic ability with the standard clinical tests for discrimination PJI and aseptic implant failure. Methods. A total of 50 patients undergoing revision hip and knee arthroplasty were enrolled into a prospective study. According to Musculoskeletal Infection Society (MSIS) criteria, 25 patients were classified as infected and 25 as not infected. In all patients, neutrophil CD64 index and percentage of polymorphonuclear neutrophils (PMN%) in synovial fluid, serum CRP, ESR, and serum CD64 index levels were measured preoperatively. Receiver operating characteristic (ROC) curves and the area under the curve (AUC) were analyzed for each biomarker. Results. Serum CD64 index showed no significant difference between the two groups (p = 0.091). Synovial fluid CD64 index and PMN% discriminated good differentiation between groups of PJI and aseptic failure with AUC of 0.946 (95% confidence interval (CI) 0.842 to 0.990) and 0.938 (95% CI 0.832 to 0.987) separately. The optimal threshold value of synovial CD64 index for the diagnosis of PJI was 0.85, with a sensitivity of 92.00%, a specificity of 96.00%, and diagnostic odds ratio (DOR) of 227.11. Conclusion. The present study demonstrates that CD64 index in synovial fluid could be a promising laboratory marker for screening PJI. The cut-off values of 0.85 for synovial CD64 index has the potential to distinguish aseptic failure from PJI. Cite this article: Bone Joint J 2020;102-B(4):463–469

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

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

Cut-off values with highest sensitivity and specificity for the synovial fluid white cell and differential count will facilitate the accurate diagnosis of infection in total knee (TKR) and total hip replacement (THR). All patients undergoing revision TKR or THR for suspected prosthetic joint infection between 2009 and 2011 at two hospitals were identified. A total of 75 patients were included with a mean age of 70.3 years (38 to 89). Synovial fluid was aspirated pre-operatively and peri-prosthetic tissue samples were taken intra-operatively for histological and microbiological examination. Receiver operating characteristic (ROC) plots were constructed for white cell and differential counts in aspirated fluid. The optimal cut-off for TKR and THR was 1590 white cells/µl and 65% neutrophilia. The white cell count cut-off value identified for THR was notably lower than previously quoted in the literature. A cut-off value for white cell count in synovial aspirate in suspected prosthetic joint infection of between 1100 and 1700 white cells/µl is likely to be applicable to both THR and TKR. Cite this article: Bone Joint J 2013;95-B:554–7

Aims. The aim of this study was to further evaluate the accuracy of ten promising synovial biomarkers (bactericidal/permeability-increasing protein (BPI), lactoferrin (LTF), neutrophil gelatinase-associated lipocalin (NGAL), neutrophil elastase 2 (ELA-2), α-defensin, cathelicidin LL-37 (LL-37), human β-defensin (HBD-2), human β-defensin 3 (HBD-3), D-dimer, and procalcitonin (PCT)) for the diagnosis of periprosthetic joint infection (PJI), and to investigate whether inflammatory joint disease (IJD) activity affects their concentration in synovial fluid. Methods. We included 50 synovial fluid samples from patients with (n = 25) and without (n = 25) confirmed PJI from an institutional tissue bank collected between May 2015 and December 2016. We also included 22 synovial fluid samples aspirated from patients with active IJD presenting to Department of Rheumatology, the first Medical Centre, Chinese PLA General Hospital. Concentrations of the ten candidate biomarkers were measured in the synovial fluid samples using standard enzyme-linked immunosorbent assays (ELISA). The diagnostic accuracy was evaluated by receiver operating characteristic (ROC) curves. Results. BPI, LTF, NGAL, ELA-2, and α-defensin were well-performing biomarkers for detecting PJI, with areas under the curve (AUCs) of 1.000 (95% confidence interval, 1.000 to 1.000), 1.000 (1.000 to 1.000), 1.000 (1.000 to 1.000), 1.000 (1.000 to 1.000), and 0.998 (0.994 to 1.000), respectively. The other markers (LL-37, HBD-2, D-dimer, PCT, and HBD-3) had limited diagnostic value. For the five well-performing biomarkers, elevated concentrations were observed in patients with active IJD. The original best thresholds determined by the Youden index, which discriminated PJI cases from non-PJI cases could not discriminate PJI cases from active IJD cases, while elevated thresholds resulted in good performance. Conclusion. BPI, LTF, NGAL, ELA-2, and α-defensin demonstrated excellent performance for diagnosing PJI. However, all five markers showed elevated concentrations in patients with IJD activity. For patients with IJD, elevated thresholds should be considered to accurately diagnose PJI. Cite this article: Bone Joint J 2021;103-B(1):32–38

Aims. As a proven and comprehensive molecular technique, metagenomic next-generation sequencing (mNGS) has shown its potential in the diagnosis of pathogens in patients with periprosthetic joint infection (PJI), using a single type of specimen. However, the optimal use of mNGS in the management of PJI has not been explored. In this study, we evaluated the diagnostic value of mNGS using three types of specimen with the aim of achieving a better choice of specimen for mNGS in these patients. Methods. In this prospective study, 177 specimens were collected from 59 revision arthroplasties, including periprosthetic tissues, synovial fluid, and prosthetic sonicate fluid. Each specimen was divided into two, one for mNGS and one for culture. The criteria of the Musculoskeletal Infection Society were used to define PJI (40 cases) and aseptic failure (19 cases). Results. The sensitivity and specificity of mNGS in the diagnosis of PJI were 95% and 94.7%, respectively, for all types of specimen. The sensitivity and specificity were 65% and 100%, respectively, for periprosthetic tissues, 87.5% and 94.7%, respectively, for synovial fluid, and 92.5% and 94.7%, respectively, for prosthetic sonicate fluid. The mNGS of prosthetic sonicate fluid outperformed that for other types of specimen in the rates of detection of pathogens (84.6%), sequencing reads (> ten-fold) and the rate of genome coverage (> five-fold). Conclusion. mNGS could serve as an accurate diagnostic tool in the detection of pathogens in patients with a PJI using three types of specimen. Due to its superior perfomance in identifying a pathogen, mNGS of prosthetic sonicate fluid provides the most value and may partly replace traditional tests such as bacteriological culture in these patients. Cite this article: Bone Joint J 2021;103-B(5):923–930

Aims. The aim of this study was to evaluate the diagnostic accuracy of the synovial alpha-defensin enzyme-linked immunosorbent assay (ELISA) for the diagnosis of prosthetic joint infection (PJI) in the work-up prior to revision of total hip (THA) and knee arthroplasty (TKA). Patients and Methods. Inclusion criteria for this prospective cohort study were acute or chronic symptoms of the index joint without specific exclusion criteria. Synovial fluid aspirates of 202 patients were analyzed and semiquantitative laboratory alpha-defensin ELISA was performed. Final diagnosis of PJI was established by examination of samples obtained during revision surgery. Results. Sensitivity and specificity of the alpha-defensin ELISA for PJI were 78.2% (95% confidence interval (CI) 66.7 to 88.5) and 96.6% (95% CI 93.0 to 99.3). Positive and negative predictive values were 89.6% (95% CI 80.6 to 97.8) and 92.2% (95% CI 87.5 to 96.1). The test remained false-negative in 22% of septic revisions, most of which were due to coagulase-negative staphylococci all occurring in either late-chronic or early-postoperative PJI. Conclusion. The routine use of synovial fluid alpha-defensin laboratory ELISA in the preoperative evaluation of symptomatic THAs and TKAs is insufficient to accurately diagnose PJI. Particularly in cases involving low-virulence organisms, such as coagulase-negative staphylococci, there remains a need for tests with a higher sensitivity. Cite this article: Bone Joint J 2019;101-B:970–977

Aims. Metagenomic next-generation sequencing (mNGS) is useful in the diagnosis of infectious disease. However, while it is highly sensitive at identifying bacteria, it does not provide information on the sensitivity of the organisms to antibiotics. The purpose of this study was to determine whether the results of mNGS can be used to guide optimization of culture methods to improve the sensitivity of culture from intraoperative samples. Methods. Between July 2014 and October 2019, patients with suspected joint infection (JI) from whom synovial fluid (SF) was obtained preoperatively were enrolled. Preoperative aspirated SF was analyzed by conventional microbial culture and mNGS. In addition to samples taken for conventional microbial culture, some samples were taken for intraoperative culture to optimize the culture method according to the preoperative mNGS results. The demographic characteristics, medical history, laboratory examination, mNGS, and culture results of the patients were recorded, and the possibility of the optimized culture methods improving diagnostic efficiency was evaluated. Results. A total of 56 cases were included in this study. There were 35 cases of JI and 21 cases of non-joint infection (NJI). The sensitivity, specificity, and accuracy of intraoperative microbial culture after optimization of the culture method were 94.29%, 76.19%, and 87.5%, respectively, while those of the conventional microbial culture method were 60%, 80.95%, and 67.86%, respectively. Conclusion. Preoperative aspirated SF detected via mNGS can provide more aetiological information than preoperative culture, which can guide the optimization and improve the sensitivity of intraoperative culture. Cite this article: Bone Joint J 2021;103-B(1):39–45

Aims. To establish the utility of adding the laboratory-based synovial alpha-defensin immunoassay to the traditional diagnostic work-up of a prosthetic joint infection (PJI). Methods. A group of four physicians evaluated 158 consecutive patients who were worked up for PJI, of which 94 underwent revision arthroplasty. Each physician reviewed the diagnostic data and decided on the presence of PJI according to the 2014 Musculoskeletal Infection Society (MSIS) criteria (yes, no, or undetermined). Their initial randomized review of the available data before or after surgery was blinded to each alpha-defensin result and a subsequent randomized review was conducted with each result. Multilevel logistic regression analysis assessed the effect of having the alpha-defensin result on the ability to diagnose PJI. Alpha-defensin was correlated to the number of synovial white blood cells (WBCs) and percentage of polymorphonuclear cells (%PMN). Results. Intraobserver reliability and interobserver agreement did not change when the alpha-defensin result was available. Positive alpha-defensin results had greater synovial WBCs (mean 31,854 cells/μL, SD 32,594) and %PMN (mean 93.0%, SD 5.5%) than negative alpha-defensin results (mean 974 cells/μL, SD 3,988; p < 0.001 and mean 39.4% SD 28.6%; p < 0.001). Adding the alpha-defensin result did not alter the diagnosis of a PJI using preoperative (odds ratio (OR) 0.52, 95% confidence interval (CI) 0.14 to 1.88; p = 0.315) or operative (OR 0.52, CI 0.18 to 1.55; p = 0.242) data when clinicians already decided that PJI was present or absent with traditionally available testing. However, when undetermined with traditional preoperative testing, alpha-defensin helped diagnose (OR 0.44, CI 0.30 to 0.64; p < 0.001) or rule out (OR 0.41, CI 0.17 to 0.98; p = 0.044) PJI. Of the 27 undecided cases with traditional testing, 24 (89%) benefited from the addition of alpha-defensin testing. Conclusion. The laboratory-based synovial alpha-defensin immunoassay did not help diagnose or rule out a PJI when added to routine serologies and synovial fluid analyses except in cases where the diagnosis of PJI was unclear. We recommend against the routine use of alpha-defensin and suggest using it only when traditional testing is indeterminate. Cite this article: Bone Joint J 2020;102-B(5):593–599

Aims. The purpose of this current multicentre study is to analyse the presence of alpha-defensin proteins in synovial fluid using the Synovasure lateral flow device and to determine its diagnostic reliability and accuracy compared with the prosthetic joint infection (PJI) criteria produced by the Musculoskeletal Infection Society (MSIS). Patients and Methods. A cohort of 121 patients comprising 85 total knee arthroplasties and 36 total hip arthroplasties was prospectively evaluated between May 2015 and June 2016 in three different orthopaedic centres. The tests were performed on patients with a chronically painful prosthesis undergoing a joint aspiration in a diagnostic pathway or during revision surgery. Results. Based on the MSIS criteria, 34 patients (28%) would have had a PJI, and 87 patients had no PJI. Testing with the lateral flow device had a sensitivity of 97.1% (95% confidence intervals (CI) 84.5 to 99.9) and a specificity of 96.6% (95% CI 90.3 to 99.2). The positive predictive value was 91.7% (95% CI 77.7% to 98.3), and the negative predictive value was 98.8% (95% CI 93.6 to 99.9). Receiver operator characteristics analysis demonstrated an area under the curve for the Synovasure test of 0.97 (95% CI 0.93 to 1.00). Conclusion. Our findings suggest that the Synovasure test has an excellent diagnostic performance to confirm or reject the diagnosis of a PJI. The results are promising for the care of the painful or problematic knee and hip joint arthroplasty and the test should be considered as part of the diagnostic toolbox for PJIs. Cite this article: Bone Joint J 2017;99-B:1176–82

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Gram-negative periprosthetic joint infection (PJI) has been poorly studied despite its rapidly increasing incidence. Treatment with one-stage revision using intra-articular (IA) infusion of antibiotics may offer a reasonable alternative with a distinct advantage of providing a means of delivering the drug in high concentrations. Carbapenems are regarded as the last line of defense against severe Gram-negative or polymicrobial infection. This study presents the results of one-stage revision using intra-articular carbapenem infusion for treating Gram-negative PJI, and analyzes the characteristics of bacteria distribution and drug sensitivity.

Aims. The diagnosis of periprosthetic joint infection (PJI) remains demanding due to limitations of all the available diagnostic tests. The synovial fluid marker, α-defensin, is a promising adjunct for the assessment of potential PJI. The purpose of this study was to investigate the qualitative assessment of α-defensin, using Synovasure to detect or exclude periprosthetic infection in total joint arthroplasty. Patients and Methods. We studied 50 patients (28 women, 22 men, mean age 65 years; 20 to 89) with a clinical indication for revision arthroplasty who met the inclusion criteria of this prospective diagnostic study. The presence of α-defensin was determined using the qualitative Synovasure test and compared with standard diagnostic methods for PJI. Based on modified Musculoskeletal Infection Society (MSIS) criteria, 13 cases were categorised as septic and 36 as aseptic revisions. One test was inconclusive. Results. The Synovasure test achieved a sensitivity of 69% and a specificity of 94%. The positive and negative likelihood ratios were 12.46 and 0.33, respectively. A good diagnostic accuracy for PJI, with an area under the curve of 0.82, was demonstrated. Adjusted p-values using the method of Hochberg showed that Synovasure is as good at diagnosing PJI as histology (p = 0.0042) and bacteriology with one positive culture (p = 0.0327). Conclusion. With its ease of use and rapid results after approximately ten minutes, Synovasure may be a useful adjunct in the diagnosis of PJI. Cite this article: Bone Joint J 2017;99-B:66–72

Aims . Recently, several synovial biomarkers have been introduced into the algorithm for the diagnosis of a prosthetic joint infection (PJI). Alpha defensin is a promising biomarker, with a high sensitivity and specificity, but it is expensive. Calprotectin is a protein that is present in the cytoplasm of neutrophils, is released upon neutrophil activation and exhibits anti-microbial activity. Our aim, in this study, was to determine the diagnostic potential of synovial calprotectin in the diagnosis of a PJI. Patients and Methods. In this pilot study, we prospectively collected synovial fluid from the hip, knee, shoulder and elbow of 19 patients with a proven PJI and from a control group of 42 patients who underwent revision surgery without a PJI. PJI was diagnosed according to the current diagnostic criteria of the Musculoskeletal Infection Society. Synovial fluid was centrifuged and the supernatant was used to measure the level of calprotectin after applying a lateral flow immunoassay. . Results. The median synovial calprotectin level was 991 mg/L (interquartile range (IQR) 154 to 1787) in those with a PJI and 11 mg/L (IQR 3 to 29) in the control group (p < 0.0001). Using a cut-off value of 50 mg/L, this level showed an excellent diagnostic accuracy, with an area under the curve of 0.94. The overall sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) was 89%, 90%, 81% and 95% respectively. The NPV was 97% in the nine patients with a chronic PJI. . Conclusion . Synovial calprotectin may be a valuable biomarker in the diagnosis of a PJI, especially in the exclusion of an infection. With a lateral flow immunoassay, a relatively rapid quantitative diagnosis can be made. The measurement is cheap and is easy to use. . Cite this article: Bone Joint J 2017;99-B:660–5

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The aim of this study was to evaluate the diagnostic accuracy of the absolute synovial polymorphonuclear neutrophil cell (PMN) count for the diagnosis or exclusion of periprosthetic joint infection (PJI) after total hip (THA) or knee arthroplasty (TKA).

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Histology is widely used for diagnosis of persistent infection during reimplantation in two-stage revision hip and knee arthroplasty, although data on its utility remain scarce. Therefore, this study aims to assess the predictive value of permanent sections at reimplantation in relation to reinfection risk, and to compare results of permanent and frozen sections.

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A higher failure rate has been reported in haematogenous periprosthetic joint infection (PJI) compared to non-haematogenous PJI. The reason for this difference is unknown. We investigated the outcome of haematogenous and non-haematogenous PJI to analyze the risk factors for failure in both groups of patients.

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The aim of this study was to evaluate the optimal deep tissue specimen sample number for histopathological analysis in the diagnosis of periprosthetic joint infection (PJI).

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Fungal and mycobacterial periprosthetic joint infections (PJI) are rare events. Clinicians are wary of missing these diagnoses, often leading to the routine ordering of fungal and mycobacterial cultures on periprosthetic specimens. Our goal was to examine the utility of these cultures and explore a modern bacterial culture technique using bacterial blood culture bottles (BCBs) as an alternative.

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It can be extremely challenging to determine whether to perform reimplantation in patients who have contradictory serum inflammatory markers and frozen section results. We investigated whether patients with a positive frozen section at reimplantation were at a higher risk of reinfection despite normal ESR and CRP.

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The diagnosis of periprosthetic joint infection (PJI) can be difficult. All current diagnostic tests have problems with accuracy and interpretation of results. Many new tests have been proposed, but there is no consensus on the place of many of these in the diagnostic pathway. Previous attempts to develop a definition of PJI have not been universally accepted and there remains no reference standard definition.

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Use of molecular sequencing methods in periprosthetic joint infection (PJI) diagnosis and organism identification have gained popularity. Next-generation sequencing (NGS) is a potentially powerful tool that is now commercially available. The purpose of this study was to compare the diagnostic accuracy of NGS, polymerase chain reaction (PCR), conventional culture, the Musculoskeletal Infection Society (MSIS) criteria, and the recently proposed criteria by Parvizi et al in the diagnosis of PJI.

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In the absence of an identified organism, single-stage revision is contraindicated in prosthetic joint infection (PJI). However, no studies have examined the use of intra-articular antibiotics in combination with single-stage revision in these cases. In this study, we present the results of single-stage revision using intra-articular antibiotic infusion for treating culture-negative (CN) PJI.

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The success rates of two-stage revision arthroplasty for infection have evolved since their early description. The implementation of internationally accepted outcome criteria led to the readjustment of such rates. However, patients who do not undergo reimplantation are usually set aside from these calculations. The aim of this study was to investigate the outcomes of two-stage revision arthroplasty when considering those who do not undergo reimplantation, and to investigate the characteristics of this subgroup.

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Biopsy of the periprosthetic tissue is an important diagnostic tool for prosthetic joint infection (PJI) as it enables the detection of the responsible microorganism with its sensitivity to antibiotics. We aimed to investigate how often the bacteria identified in the tissue analysis differed between samples obtained from preoperative biopsy and intraoperative revision surgery in cases of late PJI; and whether there was a therapeutic consequence.

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The aim of this study was to establish the diagnostic accuracy of culture of joint aspirate with and without saline injection-reaspiration.

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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.

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Fungal prosthetic joint infections (PJIs) are rare and account for about 1% of total PJIs. Our aim was to present clinical and microbiological results in treating these patients with a two-stage approach and antifungal spacers.

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α-defensin is a biomarker which has been described as having a high degree of accuracy in the diagnosis of periprosthetic joint infection (PJI). Current meta-analyses are based on the α-defensin laboratory-based immunoassay rather than the quick on-table lateral flow test kit. This study is the first meta-analysis to compare the accuracy of the α-defensin laboratory-based immunoassay and the lateral flow test kit for the diagnosis of PJI.

Aims

To evaluate the effectiveness of an institutionally developed algorithm for evaluation and diagnosis of prosthetic joint injection and to determine the impact of this protocol on overall hospital re-admissions.p

Infection is a leading indication for revision arthroplasty. Established criteria used to diagnose prosthetic joint infection (PJI) include a range of laboratory tests. Leucocyte esterase (LE) is widely used on a colorimetric reagent strip for the diagnosis of urinary tract infections. This inexpensive test may be used for the diagnosis or exclusion of PJI. Aspirates from 30 total hip arthroplasties (THAs) and 79 knee arthroplasties (KA) were analysed for LE activity. Semi-quantitative reagent strip readings of 15, 70, 125 and 500 white blood cells (WBC) were validated against a manual synovial white cell count (WCC). A receiver operating characteristic (ROC) curve was constructed to determine the optimal cut-off point for the semi-quantitative results. Based on established criteria, six THAs and 15 KAs were classified as infected. The optimal cut-off point for the diagnosis of PJI was 97 WBC. The closest semi-quantitative reading for a positive result was 125 WBC, achieving a sensitivity of 81% and a specificity of 93%. The positive and negative predictive values of the LE test strip were 74% and 95% respectively.

The LE reagent strip had a high specificity and negative predictive value. A negative result may exclude PJI and negate the need for further diagnostic tests.

Cite this article: Bone Joint J 2015;97-B:1232–6.

The purpose of this study was to evaluate whether the serum level of interleukin 6 (IL-6) could be used to identify the persistence of infection after the first stage of a two-stage revision for periprosthetic joint infection.

Between 2010 and 2011, we prospectively studied 55 patients (23 men, 32 women; mean age 69.5 years; 36 to 86) with a periprosthetic joint infection. Bacteria were identified in two intra-operative tissue samples during re-implantation in 16 patients. These cases were classified as representing persistent infection.

To calculate a precise cut-off value which could be used in everyday clinical practice, a 3 x 2 contingency table was constructed and manually defined.

We found that a serum IL-6 ≥ 13 pg/mL can be regarded as indicating infection: its positive-predictive value is 90.9%. A serum IL-6 ≤ 8 pg/mL can be regarded as indicating an absence of infection: its negative predictive value is 92.1%.

The serum IL-6 level seems to be a reasonable marker for identifying persistent infection after the first stage of a revision joint arthroplasty and before attempting re-implantation.

Cite this article: Bone Joint J 2015;97-B:71–5.

Aims

The aim of this study was to identify the incidence of positive cultures during the second stage of a two-stage revision arthroplasty and to analyse the association between positive cultures and an infection-free outcome.

Aims

To investigate the outcomes of treatment of streptococcal periprosthetic joint infection (PJI) involving total knee and hip arthroplasties.

The aim of our study was to describe the characteristics, treatment, and outcomes of patients with periprosthetic joint infection (PJI) and normal inflammatory markers after total knee arthroplasty (TKA) and total hip arthroplasty (THA).

In total 538 TKAs and 414 THAs underwent surgical treatment for PJI and met the inclusion criteria. Pre-operative erythrocyte sedimentation rate (ESR) and C-reactive protein level (CRP) were reviewed to identify the seronegative cohort. An age- and gender-matched cohort was identified from the remaining patients for comparison. Overall, 4% of confirmed infections were seronegative (21 TKA and 17 THA). Of those who underwent pre-operative aspiration, cultures were positive in 76% of TKAs (n = 13) and 64% of THAs (n = 7). Cell count and differential were suggestive of infection in 85% of TKA (n = 11) and all THA aspirates (n = 5). The most common organism was coagulase-negative Staphylococcus. Seronegative infections were associated with a lower aspirate cell count and a lower incidence of Staphylococcus aureus infection. Two-stage revision was performed in 35 cases (95%). At a mean of five years (14 to 162 months) following revision, re-operation for infection occurred in two TKAs, and one THA. From our study we estimate around 4% of patients with PJI may present with normal ESR and CRP. When performed, pre-operative aspirate is useful in delivering a definitive diagnosis. When treated, similar outcomes can be obtained compared with patients with positive serology.

Cite this article: Bone Joint J 2015;97-B:939–44.

The purpose of this study was to compare the diagnostic accuracy for the detection of infection between the culture of fluid obtained by sonication (SFC) and the culture of peri-implant tissues (PITC) in patients with early and delayed implant failure, and those with unsuspected and suspected septic failure. It was hypothesised that SFC increases the diagnostic accuracy for infection in delayed, but not early, implant failure, and in unsuspected septic failure. The diagnostic accuracy for infection of all consecutive implants (hardware or prostheses) that were removed for failure was compared between SFC and PITC. This prospective study included 317 patients with a mean age of 62.7 years (9 to 97). The sensitivity for detection of infection using SFC was higher than using PITC in an overall comparison (89.9% versus 67%, respectively; p < 0.001), in unsuspected septic failure (100% versus 48.5%, respectively; p < 0.001), and in delayed implant failure (88% versus 58%, respectively; p < 0.001). PITC sensitivity dropped significantly in unsuspected compared with suspected septic failure (p = 0.007), and in delayed compared with early failure (p = 0.013). There were no differences in specificity.

Sonication is mainly recommended when there is implant failure with no clear signs of infection and in patients with delayed implant failure. In early failure, SFC is not superior to PITC for the diagnosis of infection and, therefore, is not recommended as a routine diagnostic test in these patients.

Cite this article: Bone Joint J 2013;95-B:244–9.

Patients with infected arthroplasties are normally treated with a two-stage exchange procedure using polymethylmethacrylate bone cement spacers impregnated with antibiotics. However, spacers may act as a foreign body to which micro-organisms may adhere and grow. In this study it was hypothesised that subclinical infection may be diagnosed with sonication of the surface biofilm of the spacer. The aims were to assess the presence of subclinical infection through sonication of the spacer at the time of a second-stage procedure, and to determine the relationship between subclinical infection and the clinical outcome. Of 55 patients studied, 11 (20%) were diagnosed with subclinical infection. At a mean follow-up of 12 months (interquartile range 6 to 18), clinical failure was found in 18 (32.7%) patients. Of the patients previously diagnosed with subclinical infection, 63% (7 of 11) had failed compared with 25% (11 of 44) of those without subclinical infection (odds ratio 5.25, 95% confidence interval 1.29 to 21.4, p = 0.021). Sonication of the biofilm of the surface of the spacer is useful in order to exclude subclinical infection and therefore contributes to improving the outcome after two-stage procedures.

We report a systematic review and meta-analysis of the peer-reviewed literature focusing on metal sensitivity testing in patients undergoing total joint replacement (TJR). Our purpose was to assess the risk of developing metal hypersensitivity post-operatively and its relationship with outcome and to investigate the advantages of performing hypersensitivity testing.

We undertook a comprehensive search of the citations quoted in PubMed and EMBASE: 22 articles (comprising 3634 patients) met the inclusion criteria. The frequency of positive tests increased after TJR, especially in patients with implant failure or a metal-on-metal coupling. The probability of developing a metal allergy was higher post-operatively (odds ratio (OR) 1.52 (95% confidence interval (CI) 1.06 to 2.31)), and the risk was further increased when failed implants were compared with stable TJRs (OR 2.76 (95% CI 1.14 to 6.70)).

Hypersensitivity testing was not able to discriminate between stable and failed TJRs, as its predictive value was not statistically proven. However, it is generally thought that hypersensitivity testing should be performed in patients with a history of metal allergy and in failed TJRs, especially with metal-on-metal implants and when the cause of the loosening is doubtful.

We wished to estimate the incidence of surgical-site infection (SSI) after total hip replacement (THR) and hemiarthroplasty and its strength of association with major risk factors. The SSI surveillance service prospectively gathered clinical, operative and infection data on inpatients from 102 hospitals in England during a four-year period.

The overall incidence of SSI was 2.23% for 16 291 THRs, 4.97% for 5769 hemiarthroplasty procedures, 3.68% for 2550 revision THRs and 7.6% for 198 revision hemiarthroplasties. Staphylococcus aureus was identified in 50% of SSIs; 59% of these isolates were methicillin-resistant (MRSA). In the single variable analysis of THRs, age, female gender, American Society of Anesthesiologists (ASA) score, body mass index, trauma, duration of operation and pre-operative stay were significantly associated with the risk of SSI (p < 0.05). For hemiarthroplasty, the ASA score and age were significant factors. In revision THRs male gender, ASA score, trauma, wound class, duration of operation and pre-operative stay were significant risk factors. The median time to detection of SSI was eight days for superficial incisional, 11 days for deep incisional and 11 days for joint/bone infections. For each procedure the mean length of stay doubled for patients with SSI. The multivariate analysis identified age group, trauma, duration of operation and ASA score as significant, independent risk factors for SSI. There was significant interhospital variation in the rates of SSI. MRSA was the most common pathogen to cause SSI in hip arthroplasty, especially in patients undergoing hemiarthroplasty, but coagulase-negative Staph. aureus may be more important in deep infections involving the joint.