Impact of Positive Cultures During the Second Stage of a Two-Stage Exchange: Systematic Review and Meta-Analysis.

BACKGROUND: Two-stage exchange is a frequently performed procedure in patients who have a periprosthetic joint infection. Positive cultures when performing the second stage are perceived as a risk factor for reinfection. This study aimed to determine the impact of positive cultures during the second stage on the outcome of patients undergoing a 2-stage septic exchange and the impact of stopping the antibiotic treatment before reimplantation. METHODS: We systematically searched four databases. We performed a meta-analysis on the risk of complications after positive cultures during second stage and a subgroup analysis by antibiotic holiday period. We included 24 studies. RESULTS: Failure in the positive group was 37.0% and in the negative group was 13.7% with an odds ratio (OR) of 4.05. In the subgroup analysis by antibiotic holidays, failure rate without holidays was 15% and with holidays was 17.3% (P = .21). Failure in each group was higher when cultures were positive (without holidays, 25 versus 12.2%, P = .0003, and with holidays 41.1 versus 12.7%, P < .0001), but the risk of failure when cultures were positive was higher in the holiday group (OR 4.798) than in the nonholiday group (OR 2.225) in comparison to those patients who were culture negative at the second stage. CONCLUSIONS: Microbiological eradication at second stage was not obtained in 18% of cases and it was associated with a higher failure rate. In patients with positive cultures, withholding antibiotic treatment was associated with lower failure rate. Further studies to define the antibiotic strategy in 2-stage exchange procedure are necessary.

Ceramic Wear Particles: Can They Be Retrieved In Vivo and Duplicated In Vitro?

BACKGROUND: Little is known about retrieved zirconia platelet toughened alumina (ZPTA) wear particles from ceramic-on-ceramic (COC) total hip arthroplasty. Our objectives were to evaluate clinically retrieved wear particles from explanted periprosthetic hip tissues and to analyze the characteristics of in vitro-generated ZPTA wear particles. METHODS: Periprosthetic tissue and explants were received for 3 patients who underwent a total hip replacement of ZPTA COC head and liner. Wear particles were isolated and characterized via scanning electron microscopy and energy dispersive spectroscopy. The ZPTA and control (highly cross-linked polyethylene and cobalt chromium alloy) were then generated in vitro using a hip simulator and pin-on-disc testing, respectively. Particles were assessed in accordance with American Society for Testing and Materials F1877. RESULTS: Minimal ceramic particles were identified in the retrieved tissue, consistent with the retrieved components demonstrating minimal abrasive wear with material transfer. Average particle diameter from in vitro studies was 292 nm for ZPTA, 190 nm for highly cross-linked polyethylene, and 201 nm for cobalt chromium alloy. CONCLUSION: The minimal number of in vivo ZPTA wear particles observed is consistent with the successful tribological history of COC total hip arthroplasties. Due to the relatively few ceramic particles located in the retrieved tissue, in part due to implantation times of 3 to 6 years, a statistical comparison was unable to be made between the in vivo particles and the in vitro-generated ZPTA particles. However, the study provided further insight into the size and morphological characteristics of ZPTA particles generated from clinically relevant in vitro test setups.

Clinical and laboratory predictors for prosthetic joint infection within the first postoperative days following primary total hip and knee arthroplasty.

PURPOSE: To identify clinical and laboratory predictors for low- and high-grade prosthetic joint infection (PJI) within the first postoperative days following primary total hip/knee arthroplasty (THA/TKA). METHODS: Institutional bone and joint infection registry of a single osteoarticular infection referral centre was reviewed to identify all osteoarticular infections treated between 2011 and 2021. Among them were 152 consecutive PJI (63 acute high-grade PJI, 57 chronic high-grade PJI, and 32 low-grade PJI) who also had primary THA/TKA performed at the same institution, which were retrospectively analyzed with multivariate logistic regression and covariables. RESULTS: For each additional day of wound discharge, persistent wound drainage (PWD) predicted PJI in the acute high-grade PJI group with odds ratio (OR) 39.4 (p = 0.000, 95%CI 1.171-1.661), in the low-grade PJI group with OR 26.0 (p = 0.045, 95%CI 1.005-1.579), but not in the chronic high-grade PJI group (OR 16.6, p = 0.142, 95%CI 0.950-1.432). The leukocyte count product of pre-surgery and POD2 >100 predicted PJI in the acute high-grade PJI group (OR 2.1, p = 0.025, 95%CI 1.003-1.039) and in the chronic high-grade PJI group (OR 2.0, p = 0.018, 95%CI 1.003-1.036). Similar trend was also seen in the low-grade PJI group, but was not statistically significant (OR 2.3, p = 0.061, 95%CI 0.999-1.048). CONCLUSIONS: The most optimal threshold value for predicting PJI was observed only in the acute high-grade PJI group, where PWD >three days after index surgery yielded 62.9% sensitivity and 90.6% specificity, whereby the leukocyte count product of pre-surgery and POD2 >100 showed 96.9% specificity. Glucose, erythrocytes, hemoglobin, thrombocytes, and CRP showed no significant value in this regard.

Zirconia-Toughened Alumina Ceramic Wear Particles Do Not Elicit Inflammatory Responses in Human Macrophages.

Ten percent of patients undergoing total hip arthroplasty (THA) require revision surgery. One of the reasons for THA are wear particles released from the implants that can activate the immune defense and cause osteolysis and failure of the joint implant. The discrepancies between reports on toxicity and immunogenicity of the implant materials led us to this study in which we compared toxicity and immunogenicity of well-defined nanoparticles from Al2O3, zirconia-toughened alumina (ZTA), and cobalt chrome (CoCr), a human THP-1 macrophage cell line, human PBMCs, and therefrom-derived primary macrophages. None of the tested materials decreased the viability of THP-1 macrophages nor human primary macrophages at the 24 h time point, indicating that at concentrations from 0.05 to 50 µm3/cell the tested materials are non-toxic. Forty-eight hours of treatment of THP-1 macrophages with 5 µm3/cell of CoCr and Al2O3 caused 8.3-fold and 4.6-fold increases in TNF-α excretion, respectively, which was not observed for ZTA. The comparison between THP-1 macrophages and human primary macrophages revealed that THP-1 macrophages show higher activation of cytokine expression in the presence of CoCr and Al2O3 particles than primary macrophages. Our results indicate that ZTA is a non-toxic implant material with no immunogenic effects in vitro.

60 years of Charnley-Muller Alivium hip prosthesis: the revision percentage and tribo-corrosion sequelae after a mean of 27 years.

INTRODUCTION: The main aim was to analyse the series of 29 collected cemented Charnley-Muller Alivium retrievals with the meantime in situ of 27 years. In addition, the revision rate of 1425 Alivium prostheses implanted at our institution between 1977 and 1992 was calculated. MATERIALS AND METHODS: The revision percentage of the Alivium cohort was calculated up to 45 years of follow-up and compared to that of all total hip arthroplasties (THAs) implanted in the same period (No. 5535). Metal and polyethylene retrieved components were inspected in 29 cases for wear damage and roughness. Wear particles were retrieved from periprosthetic tissue using digestion protocols and their composition, morphology, and size distribution were investigated. Periprosthetic tissue was analysed histologically. RESULTS: The revision percentage of the Alivium cohort was 16% at 45 years of follow-up. It was comparable to all the THAs implanted at the same time (18%). The shape of polyethylene particles isolated from periprosthetic tissue corresponded to the wear pattern on polyethylene cups. Polyethylene particles were the main wear product, with the majority (68%) of particles smaller than 0.1 µm. Metal particles were rare with two types: CoCr and Cr based. Histological analysis showed that in 14 out of 18 specimens, the metal particles were graded + 1, reflecting that the metal loading in the periprosthetic tissue was low. CONCLUSIONS: Our study represents valuable data not reported previously on the survival rate of Charnley-Muller prostheses at 45 years of follow-up and a unique insight into the collected retrievals from the materials' point of view.

How to Handle Concomitant Asymptomatic Prosthetic Joints During an Episode of Hematogenous Periprosthetic Joint Infection, a Multicenter Analysis.

BACKGROUND: Prosthetic joints are at risk of becoming infected during an episode of bacteremia, especially during Staphylocococcus aureus bacteremia. However, it is unclear how often asymptomatic periprosthetic joint infection (PJI) occurs, and whether additional diagnostics should be considered. METHODS: In this multicenter study, we retrospectively analyzed a cohort of patients with a late acute (hematogenous) PJI between 2005-2015 who had concomitant prosthetic joints in situ. Patients without at least 1 year of follow-up were excluded. RESULTS: We included 91 patients with a hematogenous PJI and 108 concomitant prosthetic joints. The incident PJI was most frequently caused by Staphylococcus aureus (43%), followed by streptococci (26%) and Gram-negative rods (18%). Of 108 concomitant prosthetic joints, 13 were symptomatic, of which 10 were subsequently diagnosed as a second PJI. Of the 95 asymptomatic prosthetic joints, 1 PJI developed during the follow-up period and was classified as a "missed" PJI at the time of bacteremia with S. aureus (1.1%). Infected prosthetic joints were younger than the noninfected ones in 67% of cases, and prosthetic knees were affected more often than prosthetic hips (78%). CONCLUSIONS: During an episode of hematogenous PJI, concomitant asymptomatic prosthetic joints have a very low risk of being infected, and additional diagnostic work-up for these joints is not necessary.

The Impact of Surgical Strategy and Rifampin on Treatment Outcome in Cutibacterium Periprosthetic Joint Infections.

BACKGROUND: Cutibacterium species are common pathogens in periprosthetic joint infections (PJI). These infections are often treated with ß-lactams or clindamycin as monotherapy, or in combination with rifampin. Clinical evidence supporting the value of adding rifampin for treatment of Cutibacterium PJI is lacking. METHODS: In this multicenter retrospective study, we evaluated patients with Cutibacterium PJI and a minimal follow-up of 12 months. The primary endpoint was clinical success, defined by the absence of infection relapse or new infection. We used Fisher's exact tests and Cox proportional hazards models to analyze the effect of rifampin and other factors on clinical success after PJI. RESULTS: We included 187 patients (72.2% male, median age 67 years) with a median follow-up of 36 months. The surgical intervention was a 2-stage exchange in 95 (50.8%), 1-stage exchange in 51 (27.3%), debridement and implant retention (DAIR) in 34 (18.2%), and explantation without reimplantation in 7 (3.7%) patients. Rifampin was included in the antibiotic regimen in 81 (43.3%) cases. Infection relapse occurred in 28 (15.0%), and new infection in 13 (7.0%) cases. In the time-to-event analysis, DAIR (adjusted hazard ratio [HR] = 2.15, P = .03) and antibiotic treatment over 6 weeks (adjusted HR = 0.29, P = .0002) significantly influenced treatment failure. We observed a tentative evidence for a beneficial effect of adding rifampin to the antibiotic treatment-though not statistically significant for treatment failure (adjusted HR = 0.5, P = .07) and not for relapses (adjusted HR = 0.5, P = .10). CONCLUSIONS: We conclude that a rifampin combination is not markedly superior in Cutibacterium PJI, but a dedicated prospective multicenter study is needed.

Evaluation and interpretation of prosthetic joint infection diagnostic investigations.

BACKGROUND: Total joint arthroplasty (TJA) is considered one of the most successful surgical procedures ever developed. It can successfully provide pain relief, restore joint function, and improve mobility and quality of life. Prosthetic joint infection (PJI) presents with a wide variety and severity of signs and symptoms. It remains a major threat to the outcome of TJA procedures and usually necessitates surgical intervention and prolonged courses of antibiotics. Inappropriate treatment of an unrecognized PJI usually ends with unacceptable and sometimes catastrophic results. THE AIM: The understanding and evaluation of diagnostic investigations are extremely important to properly diagnose PJI, including frequently unrecognized low-grade infections, and to provide healthcare professionals with needed information for the care of patients affected by this condition. This article aims to review most of the methods available in PJI diagnostics, to emphasize the strengths and the weaknesses of each of them, and to provide a guideline on how to select the surgical treatment strategy based on the level of diagnostic certainty during the evaluation period. To safely accomplish this, it is crucial to be aware of the limitations of each diagnostic modality. THE FOCUS: The emphasis will be on the use and interpretation of the core criteria for PJI diagnosis, including the pathognomonic sinus tract communicating with the implant, purulent synovial fluid, inflammation in the periprosthetic tissue, cell count with differential, microbial growth in the synovial fluid culture, tissue sample cultures, and sonication samples.

Bernese peri-acetabular osteotomy performed with navigation and patient-specific templates is a reproducible and safe procedure.

PURPOSE: To present a novel surgical technique for the Bernese peri-acetabular osteotomy (PAO) using electromagnetic navigation (EMN) and patient-specific templates (PST), and to evaluate it against the traditional fluoroscopic technique. METHODS: We included 40 dysplastic hips. All PAOs were performed using PST and EMN. We recorded learning-related complications. For the purpose of acetabular fragment correction analysis, patients were divided into two groups. In the study group (EMN group, 30 hips), the acetabular fragment was reoriented with the help of EMN. In the control group (XR group, 10 hips), the acetabular fragment was reoriented using fluoroscopy. We compared the difference between the planned and achieved position of the acetabular fragment and outcomes between both groups. RESULTS: Two major complications occurred in four PAOs in the XR group only (first ten PAOs). The average absolute difference in planned and achieved lateral centre -edge angle (LCEA) and acetabular index (AI) was 1.2° ± 1.5° and 1.1° ± 2° for the EMN and 7° ± 6.1° and 6.3° ± 6.3° for the XR group (p = 0.02; p = 0.03). The average surgery duration was 183 ± 32 minutes for the EMN and 203 ± 42 minutes for the XR group (p = 0.19). At the last follow-up, the average Harris Hip Score (HHS) value was 88 ± 12 in the EMN and 86 ± 14 in the XR group (p = 0.84). CONCLUSIONS: Our study indicates that PAO performed with EMN and PST seems to be a safe and reproducible procedure with a short learning curve. Additionally, navigated reorientation of the acetabular fragment is significantly more accurate than the fluoroscopic technique.

A novel concept of cam-type femoroacetabular impingement treatment with patient-specific template guided osteochondral deformity ablation.

PURPOSE: To present a novel surgical concept for the cam-type femoroacetabular impingement (FAI) treatment and to assess and report the clinical outcomes. METHODS: We performed a retrospective study of a single-surgeon case series of six hips in five consecutive male patients with symptomatic cam-type FAI, treated with the mini-open anterior hip approach with a patient-specific template (PST)-guided deformity ablation between 2015 and 2018. We assessed the hip range of motion, iHOT-33, Tegner, and EQ-5D before surgery and after a minimum follow-up of 30 months. RESULTS: The average age was 37 ± 13.3 years, average BMI was 31.1 ± 3.3 kg/m2, and average pre-surgery Tönnis hip osteoarthritis (OA) grade was 1 ± 1. The average surgery duration was 71 ± eight minutes. The average estimated blood loss was 83 ± 26 ml. After a mean follow-up of 50 ± 12 months, we observed no OA progression with no change in Tönnis hip OA grades. Hip flexion and internal rotation significantly improved (p = 0.007; p = 0.048) from mean 98° ± 9° and 14° ± 11° to mean 113° ± 8° and 23° ± 8°, respectively. iHOT-33, Tegner, and EQ-5D improved significantly (p = < 0.001; p = 0.004; p = < 0.001) from mean 44.7 ± 12.2, 3 ± 1, and 0.513420 ± 0.101389 to mean 94 ± 2.7, 5 ± 1, and 1.000000 ± 0, respectively. One patient needed revision surgery for heterotopic ossification removal, with no sequelae at the last follow-up. CONCLUSION: Mini-open anterior hip approach with the PST-guided cam-type FAI deformity ablation presents an accurate and reproducible solution for cam-type FAI surgical treatment, with promising clinical outcomes. Using a PST in the cam-type FAI surgery may present a powerful additional tool in the existing open techniques armamentarium.

Lower Success Rate of Débridement and Implant Retention in Late Acute versus Early Acute Periprosthetic Joint Infection Caused by Staphylococcus spp. Results from a Matched Cohort Study.

BACKGROUND: Surgical débridement, antibiotics and implant retention (DAIR) is currently recommended by international guidelines for both early acute (postsurgical) and late acute (hematogenous) periprosthetic joint infections (PJIs). However, due to a different pathogenesis of infection, a different treatment strategy may be needed. QUESTIONS/PURPOSES: (1) Compared with early acute PJIs, are late acute PJIs associated with a higher risk of DAIR failure? (2) When stratified by microorganism, is the higher risk of failure in late acute PJI associated with Staphylocococcus aureus infection? (3) When analyzing patients with S. aureus infection, what factors are independently associated with DAIR failure? METHODS: In this multicenter observational study, early acute and late acute PJIs treated with DAIR were retrospectively evaluated and matched according to treating center, year of diagnosis, and infection-causing microorganism. If multiple matches were available, the early acute PJI diagnosed closest to the late acute PJI was selected. A total of 132 pairs were included. Treatment success was defined as a retained implant during follow-up without the need for antibiotic suppressive therapy. RESULTS: Late acute PJIs had a lower treatment success (46% [60 of 132]) compared with early acute PJIs (76% [100 of 132]), OR 3.9 [95% CI 2.3 to 6.6]; p < 0.001), but the lower treatment success of late acute PJIs was only observed when caused by Staphylococcus spp (S. aureus: 34% versus 75%; p < 0.001; coagulase-negative staphylococci: 46% versus 88%; p = 0.013, respectively). On multivariable analysis, late acute PJI was the only independent factor associated with an unsuccessful DAIR when caused by S. aureus (OR 4.52 [95% CI 1.79 to 11.41]; p < 0.001). CONCLUSIONS: Although DAIR seems to be a successful therapeutic strategy in the management of early acute PJI, its use in late acute PJI should be reconsidered when caused by Staphylococcus spp. Our results advocate the importance of isolating the causative microorganism before surgery. LEVEL OF EVIDENCE: Level III, therapeutic study.

Electromagnetic navigation system for acetabular component placement in total hip arthroplasty is more precise and accurate than the freehand technique: a randomized, controlled trial with 84 patients.

Background and purpose - The accuracy of conventional navigation systems depends on precise registration of bony landmarks. We investigated the clinical use of electromagnetic navigation (EMN), with a unique device for precise determination of the anterior pelvic plane. Patients and methods - We randomly allocated patients scheduled for total hip arthroplasty into 2 groups of 42 patients each. In the study group, cups were placed at the predetermined target angles (inclination: 42.5°; anteversion: 15°) with the support of EMN. In the control group, cups were placed freehand aiming at the same target angles. Postoperatively the true position of the cup was determined using computed tomography scan of the pelvis. Precision (root mean squared error, RMSE) bias (mean bias error, ME), accuracy, and duration of surgery were compared between the methods. Results - Cup anteversion was more accurate and precise in the navigated group. The ME in the navigated and freehand group was -1.7° (95% CI -2.4 to 1.1) and -4.5° (CI -6.5 to 2.5), respectively. The RMSE in the navigated and freehand group was 2.8° (CI 2.3-3.2) and 8.0° (CI 6.3-9.5), respectively. The inclination was also more precise in the navigated group, with the RMSE in the navigated and freehand group at 4.6° (CI 3.4-5.9) and 6.5° (CI 5.4-7.5), respectively. The accuracy of the inclination and the duration of surgeries were similar between the groups. Interpretation - Cup placement with the help of EMN is more precise than the freehand technique and it does not affect the duration of surgery.

Enterococcal periprosthetic joint infection: clinical and microbiological findings from an 8-year retrospective cohort study.

BACKGROUND: Treatment of enterococcal periprosthetic joint infections (PJI) is challenging due to non-standardized management strategies and lack of biofilm-active antibiotics. The optimal surgical and antimicrobial therapy are unknown. Therefore, we evaluated characteristics and outcome of enterococcal PJI. METHODS: Consecutive patients with enterococcal PJI from two specialized orthopedic institutions were retrospectively analyzed. Both institutions are following the same diagnostic and treatment concepts. The probability of relapse-free survival was estimated using Kaplan-Meier survival curves and compared by log-rank test. Treatment success was defined by absence of relapse or persistence of PJI due to enterococci or death related to enterococcal PJI. Clinical success was defined by the infection-free status, no subsequent surgical intervention for persistent or perioperative infection after re-implantation and no PJI-related death within 3 months. RESULTS: Included were 75 enterococcal PJI episodes, involving 41 hip, 30 knee, 2 elbow and 2 shoulder prostheses. PJI occurred postoperatively in 61 episodes (81%), hematogenously in 13 (17%) and by contiguous spread in one. E. faecalis grew in 64 episodes, E. faecium in 10 and E. casseliflavus in one episode(s). Additional microorganism(s) were isolated in 38 patients (51%). Enterococci were susceptible to vancomycin in 73 of 75 isolates (97%), to daptomycin in all 75 isolates, and to fosfomycin in 21 of 22 isolates (96%). The outcome data was available for 66 patients (88%). The treatment success after 3 years was 83.7% (95% confidence interval [CI]; 76.1-96.7%) and the clinical success was 67.5% (95% CI; 57.3-80.8%). In 11 patients (17%), a new PJI episode caused by a different pathogen occurred. All failures occurred within 3 years after surgery. CONCLUSION: About half of enterococcal PJI were polymicrobial infections. The treatment success was high (84%). All treatment failures occurred within the first 3 years after revision surgery. Interestingly, 17% of patients experienced a new PJI caused by another pathogen at a later stage. TRIAL REGISTRATION: The study was retrospectively registered with the public clinical trial identification NCT0253022 at https://www.clinicaltrials.gov on 15 July 2015.

The Not-So-Good Prognosis of Streptococcal Periprosthetic Joint Infection Managed by Implant Retention: The Results of a Large Multicenter Study.

BACKGROUND.: Streptococci are not an infrequent cause of periprosthetic joint infection (PJI). Management by debridement, antibiotics, and implant retention (DAIR) is thought to produce a good prognosis, but little is known about the real likelihood of success. METHODS.: A retrospective, observational, multicenter, international study was performed during 2003-2012. Eligible patients had a streptococcal PJI that was managed with DAIR. The primary endpoint was failure, defined as death related to infection, relapse/persistence of infection, or the need for salvage therapy. RESULTS.: Overall, 462 cases were included (median age 72 years, 50% men). The most frequent species was Streptococcus agalactiae (34%), and 52% of all cases were hematogenous. Antibiotic treatment was primarily using ß-lactams, and 37% of patients received rifampin. Outcomes were evaluable in 444 patients: failure occurred in 187 (42.1%; 95% confidence interval, 37.5%-46.7%) after a median of 62 days from debridement; patients without failure were followed up for a median of 802 days. Independent predictors (hazard ratios) of failure were rheumatoid arthritis (2.36), late post-surgical infection (2.20), and bacteremia (1.69). Independent predictors of success were exchange of removable components (0.60), early use of rifampin (0.98 per day of treatment within the first 30 days), and long treatments (≥21 days) with ß-lactams, either as monotherapy (0.48) or in combination with rifampin (0.34). CONCLUSIONS.: This is the largest series to our knowledge of streptococcal PJI managed by DAIR, showing a worse prognosis than previously reported. The beneficial effects of exchanging the removable components and of ß-lactams are confirmed and maybe also a potential benefit from adding rifampin.

Does Preoperative Antimicrobial Prophylaxis Influence the Diagnostic Potential of Periprosthetic Tissues in Hip or Knee Infections?

BACKGROUND: Undiagnosed low-grade prosthetic joint infections (PJI) are recognized as an important reason for early failure of presumably aseptic revisions. Preoperatively administered antimicrobial prophylaxis reduces the incidence of PJI but it may reduce the sensitivity of microbiologic periprosthetic tissue cultures and consequently increase the incidence of undiagnosed septic prosthetic joint failures, which can lead to catastrophic serial revisions. QUESTIONS/PURPOSES: We wished to determine whether administration of preoperative antibiotics decreases the likelihood of diagnosing PJI in patients undergoing revision hip or knee arthroplasty in whom infection is suspected. METHODS: We prospectively enrolled and evaluated 40 patients (29 with THAs and 11 with TKAs) who met the following inclusion criteria: older than 18 years, with suspected PJI of unknown cause, undergoing surgical revision. After arthrotomy, three tissue samples were obtained for microbiologic analysis and diagnosis, and antimicrobial prophylaxis (cefazolin 2 g intravenously) then was administered. Later during the procedure, but before débridement and irrigation, the second set of three tissue samples was obtained from the same surgical area and was cultured. Tissue concentration of prophylactic antibiotic was verified with the second set of samples. A positive culture result was defined as one or more positive cultures (growth on agar at or before 14 days). We then compared the yield on the microbiologic cultures obtained before administration of antibiotics with the yield on the cultures obtained after antibiotics were administered. An a priori analysis was performed; with the numbers available, we had 98% power to detect a difference in diagnostic sensitivity of 33%. RESULTS: With the numbers available, we found no difference in the likelihood that an infection would be diagnosed between the samples obtained before and after administration of antimicrobial prophylaxis (odds ratio [OR] for positive microbial culture = 0.99; 95% CI, 0.40-2.48; p = 0.99). All measured tissue concentrations of cefazolin were greater than the minimum inhibitory concentration, therefore we found that antibiotic prophylaxis was adequate at the time of second-set tissue specimen recovery. CONCLUSIONS: Results from this small, prospective series suggest that preoperative antimicrobial prophylaxis may be administered safely even in patients undergoing revision hip or knee arthroplasty in which microbiologic sampling is planned without compromising the diagnostic sensitivity of tissue sample cultures. However, before applying our results more generally, our findings need to be confirmed in larger, multicenter studies that would allow evaluation by sex, procedure, bacteriology, and other potentially important factors. LEVEL OF EVIDENCE: Level I, diagnostic study.

Detection of bacteria with molecular methods in prosthetic joint infection: sonication fluid better than periprosthetic tissue.

Background and purpose - The correct diagnosis of prosthetic joint infection (PJI) can be difficult because bacteria form a biofilm on the surface of the implant. The sensitivity of culture from sonication fluid is better than that from periprosthetic tissue, but no comparison studies using molecular methods on a large scale have been performed. We assessed whether periprosthetic tissue or sonication fluid should be used for molecular analysis. Patients and methods - Implant and tissue samples were retrieved from 87 patients who underwent revision operation of total knee or total hip arthroplasty. Both sample types were analyzed using broad-range (BR-) PCR targeting the 16S rRNA gene. The results were evaluated based on the definition of periprosthetic joint infection from the Workgroup of the Musculoskeletal Infection Society. Results - PJI was diagnosed in 29 patients, whereas aseptic failure was diagnosed in 58 patients. Analysis of sonication fluid using BR-PCR detected bacteria in 27 patients, whereas analysis of periprosthetic tissue by BR-PCR detected bacteria in 22 patients. In 6 of 7 patients in whom BR-PCR analysis of periprosthetic tissue was negative, low-virulence bacteria were present. The sensitivity and specificity values for periprosthetic tissue were 76% and 93%, respectively, and the sensitivity and specificity values for sonication fluid were 95% and 97%. Interpretation - Our results suggest that sonication fluid may be a more appropriate sample than periprosthetic tissue for BR-PCR analysis in patients with PJI. However, further investigation is required to improve detection of bacteria in patients with so-called aseptic failure.

Human beta-defensin-3 producing cells in septic implant loosening.

Human ß-defensin-3 (hBD-3) has been found in synovial fluid and later in periprosthetic tissues in septic joint implant loosening. The aim of the present study was to identify its cellular sources. Tissue samples from 12 patients were analyzed. A fully automatic Leica BOND MAX staining robot was used. Affinity-purified rabbit anti-human hBD-3 IgG was applied in a two-layer horse radish peroxidase/anti-rabbit-labeled polymer method. Double immunofluorescence of hBD3 together with CD68, CD31, heat shock protein 47 (HSP47) and mast cell tryptase (MCT) staining was done. Human BD-3 was found in monocyte/macrophage-like cells, vascular endothelial cells and fibroblasts-like cells, but was weakly expressed in foreign body giant cells and negative in neutrophils. Human BD-3 was found in CD68 and CD31 immunoreactive cells, whereas HSP47 and MCT positive cells were hBD-3 negative. Immunostaining of hBD-3 was strong in some tissue areas but weak or absent in others. Monocyte/macrophages and endothelial cells were established in this study as the major cellular sources of hBD-3 in septic loosening, but fibroblasts and foreign body giant cells can also contribute to its production. The heterogeneous topological staining of hBD-3 suggests local regulation, possibly by bacterial products, damage-associated molecular patterns and cytokines. The results explain the increased synovial fluid/tissue concentrations of hBD-3 in septic loosening.

Identification of the same species in at least two intra-operative samples for prosthetic joint infection diagnostics yields the best results with broad-range polymerase chain reaction.

PURPOSE: Prosthetic joint infection (PJI) is a devastating complication of total joint arthroplasty. No single laboratory test has perfect sensitivity and specificity; however, culture of periprosthetic tissue is the standard method for PJI diagnosis. Interpretation of positive culture results in PJI diagnostics can be difficult due to the possibility of contamination with microorganisms originating from skin micro flora. Criteria have been established to aid in distinguishing pathogen from contaminant for culture results. A similar criterion has not however been established for polymerase chain reaction (PCR) analysis, which is in part responsible for confusion about the reliability of PCR for PJI diagnostics. The aim of our study was to establish a criterion for interpretation of broad range (BR) PCR results in PJI diagnostics. METHODS: Samples of periprosthetic tissue were retrieved from 100 patients with joint prosthesis failure and analysed with BR-PCR. The results of BR-PCR were evaluated based on the number of samples of periprosthetic tissue with the same bacterial species. RESULTS: The sensitivity (87.5%) of BR-PCR was highest if the same species was present in at least one sample, although this criterion also resulted in the lowest specificity (92.1%). The sensitivity decreased (83.2%), although without a statistically significant difference, if the same species was present in two or more samples but, at the same time, specificity increased (100%), with a statistically significant difference. CONCLUSIONS: For diagnostics of PJI with BR-PCR the criterion of the same bacterial species in at least two specimens of periprosthetic tissue from the same patient should be used for interpretation of positive results.

An Upper-Arm Clostridium perfringens Fracture-Related Infection: A Case Report.

CONCLUSION: Fracture-related infections (FRI) pose serious complications, requiring swift surgical intervention. Although C. perfringens infections in FRIs are rare and literature is scarce, this case highlights the successful management and good functional outcome, offering valuable insights for clinicians dealing with such infections.

Identification of prosthetic joint infections with 16S amplicon metagenomic sequencing - comparison with standard cultivation approach.

Prosthetic joint infections (PJIs) are commonly diagnosed via culture-based methods, which may miss hard-to-grow pathogens. This study contrasts amplicon metagenomic sequencing (16S AS) with traditional culture techniques for enhanced clinical decision-making. We analyzed sonicate fluid from 27 patients undergoing revision arthroplasty using both methods, emphasizing the distinction between contaminants and true positives. Our findings show moderate agreement between the two methods, with a Cohen's kappa of 0.490, varying across bacterial genera (Cohen's kappa -0.059 to 1). The sensitivity of 16S AS compared to culture was 81% (95% CI, 68% to 94%). Sequencing revealed greater microbial diversity, including anaerobic genera like Anaerococcus and Citrobacter. Interestingly, several culture-negative PJI samples showed diverse bacteria via 16S AS. Despite rigorous controls and algorithms to eliminate contaminants, confirming bacteria presence with 16S AS remains a challenge. This highlights the need for improved PJI diagnostic methods, while also pointing out the limitations of next-generation sequencing (NGS) as a clinical diagnostic tool.