Does the alpha-defensin lateral flow test conserve its diagnostic properties in a larger population of chronic complex periprosthetic infections? Enlargement to 112 tests, from 42 tests in a preliminary study, in a reference center

Bacteriological sampling in revision surgery: When, how, and with what therapeutic impact?

Bacteriological sampling in orthopedic revision surgery for arthroplasty or internal fixation raises several questions. 1) When? And should sampling be systematic? Sampling should not be systematic in revision surgery, but only in case of suspected infection, in which case empirical antibiotic regimen should be systematically implemented. 2) How? Which tissues, how many and what transport? Only deep samples, preferably taken without ongoing antibiotic therapy, allow reliable interpretation of results. The optimal number of intra-operative samples is 5, or 3 if the laboratory uses seeding in aerobic and anaerobic vials. Samples should be transported to the laboratory within 2 h, at room temperature. 3) What conclusions can be drawn, using what references? There are several classifications, leading to divergent interpretation. The EBJIS (European Bone and Joint Infection Society) classification showed the best sensitivity in a multicenter study. 4) What duration of antibiotic washout before revision, and how to proceed if it cannot be achieved? The antibiotic-free period before sampling should be 14 days, or 21 days in case of prior treatment by cyclins, clindamycin, rifampicin or drugs with a very long half-life such as lipoglycopeptides, except when surgical intervention is required urgently. 5) How to deal with microbiological sampling and antibiotic prophylaxis at the time of revision surgery? Pursuing prophylactic antibiotic therapy during bone and joint implant revision does not greatly impair the value of intra-operative sampling. However, evidence of benefit of continuing antibiotic prophylaxis during revision arthroplasty is lacking. 6) What samples for atypic infection? Atypic micro-organisms (mycobacteria, fungi, etc.) require specific screening, guided by the clinical context and discussed before sampling is carried out. LEVEL OF EVIDENCE: V; expert opinion.

Comparative performance analysis of Synovasure™ and Leukocyte Esterase assays for the diagnosis of periprosthetic infections in complex microbiological situations

INTRODUCTION

Osteoarticular infections (OAI) after prosthetic surgery have serious functional and economic consequences. Rapid tests for alpha-defensin (TAD) and leukocyte esterase (TLE) are two intra-articular markers involved in the diagnosis of OAIs. TLE cannot be applied in the presence of blood unless centrifugation is used, but the rate of "non-application" of the test for this reason is unknown in complex microbiological situations (discordant or negative puncture, ongoing antibiotic treatment). We therefore conducted a prospective study to determine: 1) the performance of the TAD and TLE rapid tests in diagnosing complex OAI, 2) the rate of non-application of the TLE due to hemarthrosis, and 3) the concordance between the two tests.

ASSUMPTION

These two diagnostic tests had a negative predictive value (NPV) ≥ 90% for the diagnosis of complex OAI.

MATERIALS AND METHODS

A total of 79 suspected OAI patients with complex microbiological diagnoses were included between 2018 and 2023. They were 52 men (66%) for 27 women (34%), with a mean age of 66 ± 13.5 years. The hip (n = 41, 52%) and knee (n = 36, 46%) were the most represented, followed by the elbow (n = 1, 1%) and shoulder (n = 1, 1%). These patients were suspected of having an OAI that required joint puncture, but with a complex microbiological diagnosis due to discordant punctures (n = 21, 27%) or sterile punctures despite strong suspicion of infection (n = 50, 63%), or in case of ongoing antibiotic treatment (n = 8, 10%). All patients underwent joint fluid puncture followed by TAD (Synovasure™, Zimmer, Warsaw, IN, USA) and, when the macroscopic appearance of the sample allowed (clear fluid group), TLE (Multistix 8SG, Siemens Healthcare GmbH, Erlangen, Germany). The results of both tests were compared with Musculoskeletal Infection Society (MSIS) criteria.

RESULTS

Of the 79 patients included, 27 (34%) were considered infected according to the MSIS. In 30% of cases (n = 24), TLE was not feasible due to the presence of blood in the joint fluid. In the "clear fluid" group, the NPV was equal to 90% for both TAD (sensitivity 87%, specificity 88%) and TLE (sensitivity 87%, specificity 81%). The two parameters showed almost perfect agreement (κ = 0.927).

CONCLUSION

TAD and TLE are two rapid, reliable tests with near-perfect concordance and high NPV, even in situations of complex microbiological diagnosis. They are particularly useful for deciding on a therapeutic strategy for patients with complex OAI. The TLE cannot be used in 30% of cases due to hemarthrosis, but centrifugation can correct this defect.

LEVEL OF EVIDENCE

III; Prospective comparative diagnostic accuracy study.

Profiling the Immune Response to Periprosthetic Joint Infection and Non-Infectious Arthroplasty Failure

Arthroplasty failure is a major complication of joint replacement surgery. It can be caused by periprosthetic joint infection (PJI) or non-infectious etiologies, and often requires surgical intervention and (in select scenarios) resection and reimplantation of implanted devices. Fast and accurate diagnosis of PJI and non-infectious arthroplasty failure (NIAF) is critical to direct medical and surgical treatment; differentiation of PJI from NIAF may, however, be unclear in some cases. Traditional culture, nucleic acid amplification tests, metagenomic, and metatranscriptomic techniques for microbial detection have had success in differentiating the two entities, although microbiologically negative apparent PJI remains a challenge. Single host biomarkers or, alternatively, more advanced immune response profiling-based approaches may be applied to differentiate PJI from NIAF, overcoming limitations of microbial-based detection methods and possibly, especially with newer approaches, augmenting them. In this review, current approaches to arthroplasty failure diagnosis are briefly overviewed, followed by a review of host-based approaches for differentiation of PJI from NIAF, including exciting futuristic combinational multi-omics methodologies that may both detect pathogens and assess biological responses, illuminating causes of arthroplasty failure.

Reliable Diagnostic Tests and Thresholds for Preoperative Diagnosis of Non-Inflammatory Arthritis Periprosthetic Joint Infection: A Meta-analysis and Systematic Review

Objective

The current diagnostic criteria for periprosthetic joint infection (PJI) are diverse and controversial, leading to delayed diagnosis. This study aimed to evaluate and unify their diagnostic accuracy and the threshold selection of serum and synovial routine tests for PJI at an early stage.

Methods

We searched the MEDLINE and Embase databases for retrospective or prospective studies which reported preoperative‐available assays (serum, synovial, or culture tests) for the diagnosis of chronic PJI among inflammatory arthritis (IA) or non‐IA populations from January 1, 2000 to June 30, 2022. Threshold effective analysis was performed on synovial polymorphonuclear neutrophils (PMN%), synovial white blood cell (WBC), serum C‐reactive protein (CRP), and erythrocyte sedimentation rate (ESR) to find the relevant cut‐offs.

Results

Two hundred and sixteen studies and information from 45,316 individuals were included in the final analysis. Synovial laboratory‐based α‐defensin and calprotectin had the best comprehensive sensitivity (0.91 [0.86–0.94], 0.95 [0.88–0.98]) and specificity (0.96 [0.94‐0.97], 0.95 [0.89–0.98]) values. According to the threshold effect analysis, the recommended cut‐offs are 70% (sensitivity 0.89 [0.85–0.92], specificity 0.90 [0.87–0.93]), 4100/μL (sensitivity 0.90 [0.87–0.93], specificity 0.97 [0.93–0.98]), 13.5 mg/L (sensitivity 0.84 [0.78–0.89], specificity 0.83 [0.73–0.89]), and 30 mm/h (sensitivity 0.79 [0.74–0.83], specificity 0.78 [0.72–0.83]) for synovial PMN%, synovial WBC, serum CRP, and ESR, respectively, and tests seem to be more reliable among non‐IA patients.

Conclusions

The laboratory‐based synovial α‐defensin and synovial calprotectin are the two best independent preoperative diagnostic tests for PJI. A cut off of 70% for synovial PMN% and tighter cut‐offs for synovial WBC and serum CRP could have a better diagnostic accuracy for non‐IA patients with chronic PJI.

Unicompartmental knee arthroplasty: the Italian version of the Forgotten Joint Score-12 is valid and reliable to assess prosthesis awareness

PURPOSE

Unicompartmental Knee Arthroplasty (UKA) recorded an increased incidence of around 30% per year in the United States. Patient's experience and satisfaction after surgery were traditionally assessed by pre, and post-surgical scores and Patient-Reported Outcome Measures (PROMs) scales. Traditional scales as Western Ontario and McMaster University Osteoarthritis Index (WOMAC) and Oxford Knee Score (OKS) reported high ceiling effect. Patients treated by UKA usually perform well; therefore, it is necessary to have a PROMs' scale with a low ceiling effect as the Forgotten Joint Score-12 (FJS-12). PROMs have to be validated in the local language to be used. This study aims to perform a psychometric validation of the Italian version of FJS-12 for UKA for the first time.

METHODS

Between January 2019 and October 2019, 44 patients were included. Each patient completed both the FJS-12 Italian version and the WOMAC Italian version in preoperative follow-up, after 2-week and 1-month, 3-month, and 6-month postoperative follow-up. Cronbach's α, intraclass correlation coefficient (ICC), standard error of measurement (SEM), and minimal detectable change (MDC) were calculated to evaluate the reliability. The Pearson coefficient was used to assess validity. The Effect Size (ES) was used to test the responsiveness.

RESULTS

A range of Cronbach's α between 0.90 and 0.95 indicated good internal consistency for the FJS-12. The test-retest reliability was acceptable (i.e., the ICC was higher than 0.7) at each follow-up. The Pearson correlation coefficient between the FJS-12 and WOMAC was - 0.11 (n.s.) at preoperative follow-up, r = 0.47 (P = 0.001) at 1 month, r = 0.57 (P < 0.001) at 3 months, and r = 0.57 (P < 0.001) at 6 months. Therefore, except for the preoperative period, the validity of the FJS-12 score was assessed.

CONCLUSION

The FJS-12 represents a valid and reliable tool with a low ceiling effect to assess the outcomes improvement in UKA patients. Therefore, validating and translating this score in different languages could help perform more accurate studies on outcomes after UKA.

LEVEL OF EVIDENCE

Level III, diagnostic study.