Musculoskeletal Infection Society Research Articles

Different biomarker ratios in peripheral blood have limited value in diagnosing periprosthetic joint infection after total joint arthroplasty: a single-center, retrospective study

BackgroundPeriprosthetic joint infection (PJI) is a severe complication that can occur after total joint arthroplasty (TJA). The timely and accurate diagnosis of PJI is the key to treatment. This study investigated the diagnostic value of platelet to lymphocyte ratio (PLR), platelet count to mean platelet volume ratio (PVR), neutrophil to lymphocyte ratio (NLR) and monocyte to lymphocyte ratio (MLR) in PJI after total knee arthroplasty (TKA) and total hip arthroplasty (THA).MethodsWe performed a retrospective analysis of the patients who underwent revision hip or knee arthroplasty at our Institute between June 2015 and June 2020. Of the 187 patients reviewed, 168 were included in the study. According to the diagnostic criteria of the Musculoskeletal Infection Society (MSIS), 58 patients were in the PJI group, and 110 patients were in the aseptic loosening (AL) group. We recorded and compared the preoperative peripheral blood white blood cell (WBC) count, platelet count (PLT), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), PLR, PVR, NLR, and MLR in both groups. The diagnostic performance of the WBC, PLT, PLR, PVR, NLR, and MLR individually and in combination with the ESR and CRP for PJI diagnosis was evaluated by receiver operating characteristic (ROC) curves, and the sensitivity, specificity, positive predictive value, and negative predictive value were calculated.ResultsCompared to those in the AL group, the mean WBC, PLT, ESR, CRP, PLR, PVR, NLR, and MLR in the peripheral blood of the PJI group were significantly greater (P < 0.05). The analysis of the ROC curve revealed that the ESR, CRP, PLR, PVR, NLR, and MLR in peripheral blood had moderate effectiveness in diagnosing PJI, with area under the curve (AUC) values of 0.760 (95% CI: 0.688–0.823), 0.758 (95% CI: 0.687–0.821), 0.714 (95% CI: 0.639–0.781), 0.709 (95% CI: 0.634–0.777), 0.723 (95% CI: 0.649–0.789), and 0.728 (95% CI: 0.654–0.793), respectively. Conversely, the WBC and PLT counts demonstrated poor diagnostic value for PJI, with AUC values of 0.578 (95% CI: 0.499–0.653) and 0.694 (95% CI: 0.619–0.763), respectively. The results of the prediction model calculations revealed that the combined AUC of the WBC, PLT, ESR, CRP, PLR, PVR, NLR, and MLR was the highest at 0.853 (95% CI, 0.790–0.909), indicating good value in the diagnosis of PJI, with a sensitivity of 82.8% and a specificity of 72.7%. Moreover, the novel composite of parameters improved the accuracy and reliability in diagnosing PJI compared to the traditional biomarkers ESR and CRP (P = 0.015).ConclusionOur study suggested that the diagnostic value of the peripheral blood biomarkers PLR, PVR, NLR, and MLR for diagnosing PJI is limited and not superior to that of the ESR or CRP. However, when the WBC, PLT, ESR, CRP, PLR, PVR, NLR, and MLR are combined, the diagnostic performance of PJI in TJA patients can be improved.

Evaluating Modern Spacer Options and Outcomes in Revision Hip Arthroplasty

IntroductionA two-stage revision continues to be the standard treatment for periprosthetic joint infection (PJI) in hip arthroplasty. The use of “functional” spacers may allow patients to return to daily living while optimizing their health for revision surgery. We aimed to evaluate the clinical outcomes of different spacer types regarding infection eradication, mechanical complications, and functional outcomes. MethodsPatients who have complete Musculoskeletal Infection Society (MSIS) criteria for diagnosis of PJI that underwent one-stage or two-stage revision were queried in an institutional surgical database between 2002 and 2022. Out of 286 patients, 210 met our inclusion criteria and were retrospectively reviewed for demographics, laboratory values, functional and patient-reported outcomes, and subsequent revisions. The study population had 54.3% females, a mean age of 61.7 years old, and a mean follow-up of 3.7 ± 3.2 years. There was no difference between age, body mass index (BMI), or Charlson Comorbidity Index (CCI) scores between each cohort. Spacers were categorized as nonfunctional static, nonfunctional articulating, or functional articulating. Functional spacers were defined as those that allowed full weightbearing with no restrictions. Delphi criteria were used to define revision success, and failure was defined as a recurrent or persistent infection following definitive surgery. ResultsThere was a significantly lower re-operation rate after a definitive implant in the functional articulating cohort (P = 0.003), with a trending higher infection eradication rate and a lower rate of spacer failure compared to the nonfunctional spacer cohort. At 5 years, functional articulating spacers had a 94.1% survivorship rate, nonfunctional articulating spacers had an 81.2% survival rate, and nonfunctional static spacers had a 71.4% survival rate. In the functional articulating spacer cohort, 14.6% had yet to get reimplanted, with an average follow-up time of 1.4 years. ConclusionWithin this large cohort of similar demographics, functional articulating spacers may result in better clinical outcomes and infection eradication during two-stage revision arthroplasty for PJI.

Changing the definition of treatment success alters treatment outcomes in periprosthetic joint infection: a systematic review and meta-analysis

Abstract. Background: Variability in the definition of treatment success poses difficulty when assessing the reported efficacy of treatments for hip and knee periprosthetic joint infection (PJI). To address this problem, we determined how definitions of PJI treatment success have changed over time and how this has affected published rates of success after one-stage and two-stage treatments for hip and knee PJI. Methods: A systematic review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was conducted to identify one-stage and two-stage revision hip and knee PJI publications in major databases (2006–2021). Definition of treatment success, based on Musculoskeletal Infection Society tier criteria, was identified for each study. Publication year, number of patients, minimum follow-up, and study quality were also recorded. The association of success definitions and treatment success rate was measured using multi-variable meta-regression. Results: Study quality remained unchanged in the 245 publications included. Over time, no antibiotics (tier 1) and no further surgery (tier 3) (40.7 % and 54.5 %, respectively) became the two dominant criteria. After controlling for type of surgery, study quality, study design, follow-up, and year of publication, studies with less strict success definitions (tier 3) reported slightly higher odds ratios of 1.05 [1.01, 1.10] (p=0.009) in terms of treatment success rates compared to tier 1. Conclusions: PJI researchers have gravitated towards tier-1 and tier-3 definitions of treatment success. While studies with stricter definitions had lower PJI treatment success, the clinical significance of this is unclear. Study quality, reflected in the methodological index for non-randomized studies (MINORS) score, did not improve. We advocate for improving PJI study quality, including clarification of the definition of treatment success.

Static Versus Articulating Spacer: Does Infectious Pathogen Type Affect Treatment Success?

Treatment with a static or an articulating antibiotic-containing spacer is a common strategy for treating periprosthetic joint infection (PJI), yet many patients have persistent infections after spacer treatment. Although previous studies have compared the efficacy of a static and articulating spacer for treating PJI, few studies have assessed infection control from the time of spacer implantation, or they defined treatment failure as including reinfection, reoperation, or chronic suppressive therapy. Additionally, few studies have examined whether there is an interaction between spacer and pathogen type with respect to treatment success. (1) Is there a difference in failure-free survival (defined as no reoperation, reinfection, or suppressive antibiotic therapy) between static and articulating spacers after spacer implantation for PJI? (2) Did the relationship between spacer type and failure-free survival differ by pathogen type (staphylococcal versus nonstaphylococcal and difficult-to-treat [including methicillin-resistant Staphylococcus aureus, methicillin-susceptible S. aureus, Corynebacterium, Mycobacterium, Enterococcus spp, and other gram-negative bacterium] versus not-difficult-to-treat organisms)? Between January 2014 and January 2022, a convenience sample of 277 patients was identified as having knee PJIs treated with an articulating (75% [208 of 277]) or static (25% [69 of 277]) antibiotic spacer and potentially eligible for this study. During that time, providers at our institution generally used spacers for later-presenting or chronic infections. Spacer choice was determined by surgeon preference, with static spacers used more often in instances of higher bone loss and poor soft tissue coverage. Thirty-one patients (8 static and 23 articulating spacers) were considered lost to follow-up or had incomplete datasets and were excluded from the analysis, resulting in a final analysis cohort of 246 patients: 25% (61 of 246) received a static spacer and 75% (185 of 246) received an articulating spacer. The mean ± standard deviation age of patients was 66 ± 9.9 years, BMI was 33.3 ± 6.9 kg/m2, and Elixhauser score was 18.1 ± 16.9. Demographic and clinical characteristics were similar between the two groups. Pathogen type was collected and categorized as staphylococcal versus nonstaphylococcal, and difficult-to-treat (including methicillin-resistant Staphylococcus aureus, methicillin-susceptible S. aureus, Corynebacterium, Mycobacterium, Enterococcus spp, and other gram-negative bacterium) versus not-difficult-to-treat, as defined by an infectious disease physician. Other variables we collected included sex, age, American Society of Anesthesiologists classification, BMI, and Elixhauser score. The primary outcome of interest was failure-free survival, which was a composite time-to-event outcome, with failure defined as reoperation, reinfection, death owing to infection, or chronic antibiotic use at a minimum of 1 year after the completion of the patient's Stage 1 postoperative antibiotic course, whichever came first. Reinfection was determined by the treating physicians in accordance with the Musculoskeletal Infection Society guidelines and included an evaluation of infectious laboratory values, cultures, and clinical signs of infection. We compared static and articulating spacers using a Cox proportional hazards model, with spacer type as the primary predictor variable. We compared staphylococcal versus nonstaphylococcal and difficult-to-treat versus not-difficult-to-treat infections by running additional models with interaction terms between spacer type and pathogen type. No difference was observed in the cause-specific hazard ratio for static versus articulating (reference) spacers (HR 1.45 [95% confidence interval 0.94 to 2.22]; p = 0.09), after adjusting for covariates. Additionally, no difference in the association between spacer type and failure-free survival was found between pathogen types or treatment difficulty after evaluating interactions (staphylococcal HR 0.37 [95% CI 0.15 to 0.91], nonstaphylococcal HR 0.79 [95% CI 0.49 to 1.28]; p value for interaction = 0.14; difficult-to-treat HR 0.37 [95% CI 0.14 to 0.99], not-difficult-to-treat HR 0.75 [95% CI 0.47 to 1.20]; p value for interaction = 0.20). The lack of a difference in failure-free survival and insufficient evidence of a difference in the association between spacer type and treatment failure by pathogen type suggests that infectious organism may not be an important consideration in the decision about spacer treatment type. Further studies should aim to elucidate which patient factors are the most influential in surgeon decision-making when choosing a spacer type in patients with PJI of the knee.Level of Evidence Level III, therapeutic study.

Diabetic management and infection risk in total ankle arthroplasty

BackgroundAs total ankle arthroplasty (TAA) increases in popularity nationwide for the management of end-stage arthritis, it is essential to understand ways to mitigate the risk of infection. Diabetes increases the risk of infection due to compromised immunity and impaired wound-healing mechanisms. However, there is limited research on how diabetic management, inclusive of medications and glucose control, may impact infection risks post-TAA. This study aims to demonstrate the impact of diabetic management on the occurrence of periprosthetic joint infection (PJI) following TAA. MethodsThis was a retrospective study of patients who underwent a TAA at a single academic institution from March 2002 to May 2022. Patients with diabetes who developed an intraarticular infection following TAA were propensity score matched (1:3) to diabetic patients who did not. Data collection included demographics, implant types, diabetic medications, and preoperative hemoglobin A1c. PJI was diagnosed based on Musculoskeletal Infection Society (MSIS) criteria. Statistical analyses assessed differences in medication use, glucose control, and infection rates between groups. ResultsOf the 1863 patients who underwent TAA, 177 patients had a diagnosis of diabetes. The infection rate in patients with diabetes (2.8%) was higher than the total cohort rate (0.8%). Five patients with diabetes developed a PJI at an average of 2.2 months postoperatively. This cohort (n = 5) was compared to propensity score-matched controls (n = 15). There was no significant difference in diabetic medication use. Patients who developed PJI had higher rates of uncontrolled diabetes (60.0% vs. 6.7%) and average A1c levels (7.02% vs. 6.29%) compared to controls. ConclusionOur findings suggest that the elevated risk of PJI observed in individuals with diabetes subsequent to TAA may be attributed not solely to the presence of diabetes, but to inadequate glycemic control. Effectively managing blood glucose levels is imperative for achieving favorable outcomes following TAA. Level of evidenceIII

Comparison of Delphi Consensus Criteria and Musculoskeletal Infection Society Outcome Reporting Tool Definitions of Successful Surgical Treatment of Periprosthetic Knee Infection

BackgroundAgreement on success following surgical treatment for periprosthetic joint infection (PJI) is important for comparing the efficacy of different surgical approaches with varying consequences and outcomes and setting patient expectations. We compared success rates following two-stage exchange arthroplasty for knee PJI using two expert-consensus definitions of success. MethodsProspectively documented data for 57 knees treated by a single surgeon at an academic tertiary care center were retrospectively reviewed. Treatment outcomes were quantified using the Delphi Consensus Criteria and the Musculoskeletal Infection Society Outcome Reporting Tool (MSIS ORT). ResultsSuccess rates were 81% using the Delphi Consensus Criteria and 56% using the MSIS ORT (P = .008). The MSIS ORT success rates increased to 76% when aseptic revisions and deaths unrelated to PJI were not penalized as failures of treatment. Predicted probabilities of successful treatment in a hypothetical case scenario were lowest based on the MSIS ORT and similarly higher using Delphi Consensus Criteria and MSIS ORT modified for both women (53.0, 90.8, and 88.7%) and men (29.1, 89.1, and 89.3%). ConclusionsStudy observations underscore the need for a uniformly accepted single definition of surgical treatment success.

Evaluation of time to reimplantation as a risk factor in two-stage revision with static spacers for periprosthetic knee joint infection

IntroductionWe investigated the time to reimplantation (TTR) during two-stage revision using static spacers with regard to treatment success and function in patients with chronic periprosthetic joint infection (PJI) of the knee.Methods163 patients (median age 72 years, 72 women) who underwent two-stage exchange for chronic knee PJI between 2012 and 2020 were retrospectively analyzed (based on the 2011 Musculoskeletal Infection Society criteria). A cutoff TTR for increased risk of reinfection was identified using the maximally selected log-rank statistic. Infection control, aseptic revisions and overall survival were analyzed using Kaplan–Meier survival estimates. Adjustment for confounding factors—the Charlson Comorbidity Index (CCI) and C-reactive protein (CRP)—was done with a Cox proportional hazards model.ResultsWhen TTR exceeded 94 days, the adjusted hazard of reinfection was increased 2.8-fold (95% CI 1.4–5.7; p = 0.0036). The reinfection-free rate was 67% (95% CI 52-79%) after 2 years and 33% (95% CI 11–57%) after 5 years for a longer TTR compared to 89% (95% CI 81–94%) and 80% (95% CI 69–87%) at 2 and 5 years, respectively, for a shorter TTR. Adjusted overall survival and number of aseptic revisions did not differ between the longer TTR and shorter TTR groups. Maximum knee flexion was 90° (IQR 84–100) for a longer TTR and 95° (IQR 90–100) for a shorter TTR (p = 0.0431), with no difference between the groups in Oxford Knee Score. Baseline characteristics were similar (body mass index, age, previous surgeries, microorganisms) for the two groups, except that there was a higher CCI (median 4 vs. 3) and higher CRP (median 3.7 vs 2.6 mg/dl) in the longer TTR group.ConclusionA long TTR is sometimes unavoidable in clinical practice, but surgeons should be aware of a potentially higher risk of reinfection.Level of evidence: III, retrospective comparative study.

Optimal selection of specimens for metagenomic next-generation sequencing in diagnosing periprosthetic joint infections.

This study aimed to assess the diagnostic value of metagenomic next-generation sequencing (mNGS) across synovial fluid, prosthetic sonicate fluid, and periprosthetic tissues among patients with periprosthetic joint infection (PJI), intending to optimize specimen selection for mNGS in these patients. This prospective study involved 61 patients undergoing revision arthroplasty between September 2021 and September 2022 at the First Affiliated Hospital of Zhengzhou University. Among them, 43 cases were diagnosed as PJI, and 18 as aseptic loosening (AL) based on the American Musculoskeletal Infection Society (MSIS) criteria. Preoperative or intraoperative synovial fluid, periprosthetic tissues, and prosthetic sonicate fluid were collected, each divided into two portions for mNGS and culture. Comparative analyses were conducted between the microbiological results and diagnostic efficacy derived from mNGS and culture tests. Furthermore, the variability in mNGS diagnostic efficacy for PJI across different specimen types was assessed. The sensitivity and specificity of mNGS diagnosis was 93% and 94.4% for all types of PJI specimens; the sensitivity and specificity of culture diagnosis was 72.1% and 100%, respectively. The diagnostic sensitivity of mNGS was significantly higher than that of culture (X2 = 6.541, P=0.011), with no statistically significant difference in specificity (X2 = 1.029, P=0.310). The sensitivity of the synovial fluid was 83.7% and the specificity was 94.4%; the sensitivity of the prosthetic sonicate fluid was 90.7% and the specificity was 94.4%; and the sensitivity of the periprosthetic tissue was 81.4% and the specificity was 100%. Notably, the mNGS of prosthetic sonicate fluid displayed a superior pathogen detection rate compared to other specimen types. mNGS can function as a precise diagnostic tool for identifying pathogens in PJI patients using three types of specimens. Due to its superior ability in pathogen identification, prosthetic sonicate fluid can replace synovial fluid and periprosthetic tissue as the optimal sample choice for mNGS.

Do one-stage indications predict success following two-stage arthroplasty for chronic periprosthetic joint infection?

Introduction: The 2018 International Consensus Meeting (ICM) proposed criteria for one-stage exchange arthroplasty in treating periprosthetic joint infection (PJI). Our study aimed to determine what proportion of PJI patients met the 2018 ICM criteria and how this affected infection-free survivorship for patients. Methods: All chronic PJI patients treated with two-stage exchange within our institution between 2017-2020 were retrospectively reviewed. Included cases met 2011 Musculoskeletal Infection Society (MSIS) criteria for PJI and had a 2-year minimum follow-up. Treatment success was defined as Tier 1A in the 2019 MSIS working group definition. ICM one-stage criteria included non-immunocompromised host, absence of sepsis, adequate soft tissue for closure, known preoperative pathogen, and susceptibility. Immunocompromised host was analyzed as two separate definitions. Kaplan-Meier survivorship, Cox regression, and univariate analyses were performed. Results: A total of 293 chronic PJI patients were included. Overall, treatment failure occurred in (21.8 %) patients. Only 13 % () met ICM criteria definition no.1 for one-stage exchange; 12 % () met definition no.2. In both definitions, infection-free survivorship at 2years did not differ between patients who met and did not meet criteria (). Cox proportional hazard regression analyses demonstrated that the only variable predicting treatment failure was knee joint involvement (). Conclusions: We found that a very limited number of chronic PJI patients were suitable for a one-stage exchange. Furthermore, the supposition that healthier hosts with known pathogens (the basis of the ICM criteria) yield better PJI treatment outcomes was not observed. These results justify the ongoing multicenter randomized control trial comparing one-stage versus two-stage treatment for chronic PJI.

Risk factors for early septic failure after two-stage exchange total knee arthroplasty for treatment of periprosthetic joint infection

BackgroundThe cause of early septic failure after two-stage exchange revision total knee arthroplasty (TKA) for chronic periprosthetic joint infection (PJI) and the factors affecting it are not well known. The purpose of this study was to determine the surgical outcomes and the risk factors for early septic failure after two-stage revision TKA for chronic PJI.MethodsWe identified a total of 246 adult patients who met the Musculoskeletal Infection Society (MSIS) diagnostic criteria for chronic PJI at two academic tertiary hospitals from March 2012 to December 2018. Finally, 151 patients who consecutively received two-stage exchange revision TKA for chronic PJI and who had a minimum 3-year follow-up were enrolled and retrospectively reviewed. Successful surgical treatment was evaluated for two-stage revision TKA and risk factors for early septic failure were identified.ResultsEarly septic failures occurred within 3 years after reimplantation in 48 patients (31.8%). After accounting for potentially confounding variables, we found that male patient [odds ratio (OR): 2.753, 95% confidence interval (CI) 1.099–6.893, p = 0.031], fungus or mycobacterial infection (OR: 5.224, 95% CI 1.481–18.433, p = 0.01), and positive culture at reimplantation (OR: 4.407, 95% CI 1.255–15.480, p = 0.021) were independently associated with early septic failure after two-stage exchange revision TKA.ConclusionMale patients, fungus or mycobacterial infection, and positive culture at reimplantation were independently associated with an increased risk of early septic failure after two-stage exchange revision TKA despite normal C-reactive protein values prior to reimplantation. Further prospective and high-quality studies are needed to determine the risk factors of two-stage exchange revision TKA for chronic PJI.Level of evidence: level IV; retrospective comparison; treatment study.

Does a sign restricting operating room access reduce staff traffic in the surgical department?

IntroductionInfections following orthopedic surgery are rare but difficult to treat. Among the prevention measures reviewed during the Musculoskeletal Infection Society's (MSIS) 2023 international consensus meeting, the only strategy to obtain 100% agreement was the control of traffic in and out of the operating room (OR). Although this recommendation makes good sense, to our knowledge, it has not been previously investigated in a comparative study. We, therefore, conducted a prospective, observational, before-and-after study of the implementation of an informational sign designed to limit traffic in and out of the OR to (1) determine its impact on door openings and the number of people present during orthopedic surgery and (2) assess the risk of surgical site infection after the institution of this sign. HypothesisThis type of sign reduces the number of door openings. Materials and methodsThis prospective, observational study included all patients operated on in one of our ORs over a 6-week period. The number of entrances and exits from the OR and how long the doors were kept open were recorded during the entire study period. After 3 weeks, an informational sign was posted on the OR doors warning people that unnecessary traffic in and out of the OR increases the risk of infection. During this period, we also recorded the type of procedure, operative time, the number of people in the OR at the time of the incision, and the number of entrances and exits. Patients underwent a follow-up at 2 years to check for postoperative infection. The primary endpoint was the number of OR door openings, and the secondary endpoint was the number of infections at 2 years postoperatively. ResultsThe 2 groups (before and after the implementation of the sign) were homogeneous. The average total number of door openings for all ORs was 28.9±19.6 [2–90]. In the no sign group, it was 33.3±20.9 [3–90], and in the sign group, it was 21.0±14.7 [2–50] (p=0.011). The maximum number of people in the OR at one time was 8.32±1.84 [4–12] in the no sign group and 8.44±1.98 [5–12] in the sign group (p=0.8). There were 3 postoperative infections at the 2-year follow-up, all occurring in the no sign group. The infection rate was 6.4% (3/47) in the no sign group versus 0% (0/25) in the sign group (p=0.197). DiscussionOur prospective study demonstrated a simple strategy to reduce the number of entrances and exits, the number of people in the OR, and potentially the risk of surgery-related infection. Another larger-scale study is needed to assess the exact impact of this type of sign, particularly on the risk of infection. Level of evidenceIII; prospective non-randomized comparative study.

A “Dry Tap” in Prosthetic Joint Infection Workup of Total Hip Arthroplasty Is Not Reassuring

BackgroundSynovial fluid analysis is important in diagnosing prosthetic joint infection (PJI). The rate of culture-positive PJI in patients who have a dry tap of a total hip arthroplasty (THA) is not well described. MethodsWe reviewed all image-guided THA aspirations, performed from 2014 to 2021 at a single academic institution. Aspirations were categorized as successful (≥ 0.5 mL) or unsuccessful (< 0.5 mL, “dry tap”). We analyzed culture data on all repeat aspirations and revision surgeries performed within 90 days of the initial dry tap. ResultsWe reviewed 275 consecutive attempted THA aspirations of which 100 (36.4%) resulted in a dry tap. The dry tap cohort had a significantly higher percentage of fluoroscopic-guided aspirations (64%) and fewer ultrasound-guided aspirations (36%) compared to the successful aspiration cohort (48.9% fluoroscopic, 53.1% ultrasound, P = .0061). Of the 100 patients who have dry taps, 48 underwent revision surgery within 90 days of the initial dry tap, and 15 resulted in 2 or more positive cultures. The rate of PJI defined by MusculoSkeletal Infection Society major criteria in the dry tap cohort was 16.0%. ConclusionsAttempted aspiration of a THA resulted in a dry tap 36.4% of the time. Of those patients who had a dry tap, 16.0% were subsequently found to have PJI based on MusculoSkeletal Infection Society major criteria. Therefore, a “dry tap” does not exclude the diagnosis of infection and should not be considered reassuring for the absence of PJI.

How good are surgeons at disclosing periprosthetic joint infection at the time of revision, based on pre- and intra-operative assessment? A study on 16,922 primary total hip arthroplasties reported to the Norwegian Arthroplasty Register.

Revision due to infection, as reported to the Norwegian Arthroplasty Register (NAR), is a surrogate endpoint to periprosthetic joint infection (PJI). We aimed to find the accuracy of the reported causes of revision after primary total hip arthroplasty (THA) compared with PJI to see how good surgeons were at disclosing infection, based on pre- and intraoperative assessment. We investigated the reasons for revision potentially caused by PJI following primary THA: infection, aseptic loosening, prolonged wound drainage, and pain only, reported to the NAR from surgeons in the region of Western Norway during the period 2010-2020. The electronic patient charts were investigated for information on clinical assessment, treatment, biochemistry, and microbiological findings. PJI was defined in accordance with the Musculoskeletal Infection Society (MSIS) definition. Sensitivity, specificity, and accuracy were calculated. 363 revisions in the NAR were eligible for analyses. Causes of revision were (reported/validated): infection (153/177), aseptic loosening (139/133), prolonged wound drainage (37/13), and pain only (34/40). The sensitivity for reported revision due to infection compared with PJI was 80%, specificity was 94%, and accuracy-the surgeons' ability to disclose PJI or non-septic revision at time of revision-was 87%. The accuracy for the specific revision causes was highest for revision due to aseptic loosening (95%) and pain only (95%), and lowest for revision due to prolonged wound drainage (86%). The accuracy of surgeon-reported revisions due to infection as representing PJI was 87% in the NAR. Our study shows the importance of systematic correction of the reported cause of revision in arthroplasty registers, after results from adequately taken bacterial samples.

Acidity Is an Excellent Marker of Infection in Hip and Knee Arthroplasty

Background: The diagnosis of joint replacement infection is a difficult clinical challenge that often occurs when the implant cannot be salvaged. We hypothesize that the pH value of synovial fluid could be an important indicator of the inflammatory status of the joint. However, in the literature, there is a lack of data on the pH changes in hip and knee joint replacements and their relation to infection and implant failure. In this study, we aimed to measure the pH levels of synovial fluid in patients with hip and knee joint replacements. We also investigated the potential of pH measurement as a diagnostic tool for joint replacement infection. In this study, we recorded the pH values to be 7.55 and 7.46 in patients where Pseudomonas aeruginosa was identified as the cause of the prosthetic joint infection. We attribute this to the different environments created by this specific bacterium. In other cases where the pH was higher, chronic mitigated infections were diagnosed, caused by strains of Staphylococcus aureus, Streptococcus agalactiase, and coagulase negative staphylococcus. Materials and methods: In our cohort of 155 patients with implanted hip (THA; n = 85) or knee (TKA; n = 70) joint replacements, we conducted a prospective study with a pH measurement. Out of the whole cohort, 44 patients had confirmed joint replacement infection (28.4%) (44/155). In 111 patients, infection was ruled out (71.6%) (111/155). Joint replacement infection was classified according to the criteria of the Musculoskeletal Infection Society (MSIS) from 2018. Based on the measured values, we determined the cut-off level for the probability of ongoing inflammation. We also determined the sensitivity and specificity of the measurement. Results: The group of patients with infection (n = 44) had a significantly lower synovial fluid pH (pH = 6.98 ± 0.48) than the group of patients with no infection (n = 111, pH = 7.82 ± 0.29, p &lt; 0.001). The corresponding median pH values were 7.08 for the patients with infection and 7.83 for the patients with no infection. When we determined the cut-off level of pH 7.4, the sensitivity level of infected replacements was 88.6%, and the specificity level of the measurement was 95.5%. The predictive value of a positive test was 88.6%, and the predictive value of a negative test was 95.5%. Conclusions: Our results confirm that it is appropriate to include a pH measurement in the diagnostic spectrum of hip and knee replacements. This diagnostic approach has the potential to provide continuous in vivo feedback, facilitated by specialized biosensors. The advantage of this method is the future incorporation of a pH-detecting sensor into intelligent knee and hip replacements that will assess pH levels over time. By integrating these biosensors into intelligent implants, the early detection of joint replacement infections could be achieved, enhancing proactive intervention strategies.

Limited value of platelet-related markers in diagnosing periprosthetic joint infection

ObjectiveTo evaluate the diagnostic values of serum platelet count (PC), mean platelet volume ratio (MPV), platelet count to mean platelet volume ratio (PVR), platelet to lymphocyte ratio (PLR), platelet to neutrophil ratio (PNR), PC/Albumin-globulin ratio (PC/AGR), and PC/C-reactive protein (PC/ CRP) in the diagnosis of periprosthetic joint infection (PJI).MethodsThe medical records were retrospectively analyzed of the 158 patients who had undergone hip or knee revisions from January 2018 to May 2022. Of them, 79 cases were diagnosed with PJI and 79 with aseptic loosening (AL). PJI was defined using the Musculoskeletal Infection Society criteria. The plasma levels of CRP, the erythrocyte sedimentation rate (ESR), PC, MPV, PVR, PLR, PNR, PC/AGR, and PC/CRP in the 2 groups were recorded and analyzed. In addition, tests were performed according to different joint types. The receiver operating characteristic curve was used to calculate the sensitivity and specificity of each indicator. The diagnostic value for each indicator was calculated according to the area under the curve (AUC).ResultsThe PC, PVR, PLR and PC/AGR levels in the PJI group were significantly higher than those in the AL group, while PC/CRP levels were significantly lower (P < 0.001). The AUC for PC/CRP, and PC/AGR was 0.804 and 0.802, respectively, which were slightly lower than that of CRP (0.826) and ESR (0.846). ROC analysis for PC/CRP, and PC/AGR revealed a cut-off value of 37.80 and 160.63, respectively, which provided a sensitivity of 73.42% and 84.81% and a specificity of 75.95% and 65.82% for PJI. The area under the curve of PLR and PC was 0.738 and 0.702. The area under the curve values for PVR, PNR, and MPV were 0.672, 0.553, and 0.544, respectively.ConclusionsThe results of this study suggest that PC, PLR, PC/CRP, and PC/AGR values do not offer significant advantages over ESR or CRP values when employed for the diagnosis of PJI. PVR, PNR, and MPV were not reliable in the diagnosis of PJI.

Debridement, Antibiotics, and Implant Retention (DAIR) Plus Offers Similar Periprosthetic Joint Infection Treatment Success Rates to Two-Stage Revision in Oncologic Megaprosthesis

BackgroundProsthetic joint infections (PJIs) after megaprosthesis implantation are associated with high rates of treatment failure and amputation. Our study analyzed PJI treatment success rates by surgical strategy and assessed risks of reinfection and amputation. MethodsWe retrospectively analyzed the outcomes of patients diagnosed with PJI after undergoing megaprosthesis implantation for oncologic indications. The 2011 Musculoskeletal Infection Society criteria were used to define PJI. Reinfection, reoperation, and amputation for PJI recurrence were assessed. A total of 67 patients with megaprosthesis PJIs were included. There were fourteen patients who were treated with debridement, antibiotics, and implant retention (DAIR), 31 with DAIR plus (DAIR with modular component exchange and stem retention), and 21 with two-stage revisions. Kaplan-Meier estimates were used for survival analyses and Cox proportional hazards for risk factor analyses. ResultsThe two-year reinfection-free survival was 25% for DAIR and 60% for DAIR plus or two-stage revision (P = .049). The five-year amputation-free survival was 84% for DAIR plus or two-stage revision, and 48% for DAIR (P = .13). Reinfection-free, reoperation-free, and amputation-free survival were similar between DAIR plus and two-stage revision at the 2- and 5-year marks. Body mass index ≥30 (hazard ratio [HR] = 2.65) and chronic kidney disease (HR = 11.53) were risk factors for reinfection. Treatment with DAIR plus or two-stage revision (HR = 0.44) was a protective factor against reinfection. ConclusionsA DAIR was associated with high rates of treatment failure and higher amputation rates than DAIR plus or 2-stage surgery. A DAIR plus was not inferior to 2-stage revision clearing a PJI and might be performed in patients who cannot withstand two-stage revision surgery.

Host and microbial characteristics associated with recurrent prosthetic joint infections.

Approximately 20% of patients after resection arthroplasty and antibiotic spacer placement for prosthetic joint infection develop repeat infections, requiring an additional antibiotic spacer before definitive reimplantation. The host and bacterial characteristics associated with the development of recurrent infection is poorly understood. A case-control study was conducted for 106 patients with intention to treat by two-stage revision arthroplasty for prosthetic joint infection at a single institution between 2009 and 2020. Infection was defined according to the 2018 Musculoskeletal Infection Society criteria. Thirty-nine cases ("recurrent-periprosthetic joint infection[PJI]") received at least two antibiotic spacers before clinical resolution of their infection, and 67 controls ("single-PJI") received a single antibiotic cement spacer before infection-free prosthesis reimplantation. Patient demographics, McPherson host grade, and culture results including antibiotic susceptibilities were compared. Fifty-two (78%) single-PJI and 32 (82%) recurrent-PJI patients had positive intraoperative cultures at the time of their initial spacer procedure. The odds of polymicrobial infections were 11-fold higher among recurrent-PJI patients, and the odds of significant systemic compromise (McPherson host-grade C) were more than double. Recurrent-PJI patients were significantly more likely to harbor Staphylococcus aureus. We found no differences between cases and controls in pathogen resistance to the six most tested antibiotics. Among recurrent-PJI patients, erythromycin-resistant infections were more prevalent at the final than initial spacer, despite no erythromycin exposure. Our findings suggest that McPherson host grade, polymicrobial infection, and S. aureus infection are key indicators of secondary or persistent joint infection following resection arthroplasty and antibiotic spacer placement, while bacterial resistance does not predict infection-related arthroplasty failure.

1287. Assessing the Utility of Vertebral Body / Disc Space Fluid Cell Differential in the Diagnosis of Native Vertebral Osteomyelitis

Abstract Background Current approaches to diagnosing suspected native vertebral osteomyelitis (NVO) rely on imaging and microbiological workup, including blood and CT-guided biopsy cultures. These existing diagnostic methods often result in ambiguity, necessitating additional tests to distinguish NVO from its mimics. Our study aims to validate pilot findings demonstrating that an elevated neutrophil differential (PMN) in vertebral bone biopsy/ disc space fluid aspirate is associated with NVO. This may allow stratification of patients with suspected NVO into those who can be monitored closely versus those who may benefit from further invasive testing or empiric antibiotic therapy (Fig 1). Figure 1: Proposed workup of patients with suspected native vertebral osteomyelitis guided by disc space/ vertebral body neutrophil (PMN) differential. Methods This analysis examines a subset of patients from a prospective cohort study, enrolling adults referred to Mayo Clinic's neuroradiology department for spine biopsy. After collecting routine clinical specimens, the needle is rinsed with saline into an EDTA tube for automated cell count and differential analysis. To evaluate the predictive capacity of neutrophil (PMN) differential for NVO, logistic regression models were employed, and receiver operating characteristic (ROC) curve analyses were conducted for various PMN percentage cutoff points. Results In this preliminary analysis, 39 patients were included, comprising 7 patients with NVO and 32 patients with alternative diagnoses. Baseline characteristics are presented in Table 1. All NVO patients received antibiotics within two weeks of the spine biopsy. The median biopsy sample PMN percentage for NVO patients was 83.0 (77.5-88.0), compared to 65.0 (56.5-69.5) for those without NVO (p=0.005) (Fig 2A). The estimated relationship between the probability of NVO and each measure across the full range of percentages is illustrated in Fig 2B. The optimal ROC curve point corresponds to a PMN differential of 72.5% (sensitivity=0.86, specificity=0.81) (Fig 3).Table 1:Baseline Characteristics of Patients Included in the Preliminary AnalysisFigure 2:A) Distribution of spine biopsy neutrophil percent by native vertebral osteomyelitis (NVO) status, B) Loess nonparametric smoother showing the relationship between the probability of NVO and biopsy sample neutrophil percentage.Figure 3:ROC curve analysis of neutrophil percent and NVO Conclusion This preliminary analysis indicates that an elevated PMN differential in spine biopsy samples may serve as a valuable diagnostic tool for NVO, with results seemingly unaffected by recent antibiotic intake. The PMN differential cutoff of 72.5% exhibited notable sensitivity and specificity. Investigations are ongoing to further validate these findings Disclosures Brett Freedman, MD, Clear Choice Therapeutics: Stocks/Bonds|Medtronic: Grant/Research Support|Neuroinnovations: Stocks/Bonds Aaron J. Tande, M.D., Musculoskeletal Infection Society: Board Member|Wolters Kluwer Health - Lippincott Williams &amp; Wilkins: Publishing royalties, financial or material support

1300. Comparison of the Clinical Characteristics and Outcomes of Anaerobic Prosthetic Joint Infections (PJI) and Aerobic PJIs : A Retrospective Review

Abstract Background PJI is an uncommon but serious complication of joint arthroplasties that can result in significant morbidity and cost. There is a paucity of studies in the literature on PJIs caused by anaerobic organisms either as the sole pathogen or part of a polymicrobial infection. The purpose of this study was to compare the clinical presentation and outcomes of PJI caused by anaerobes as opposed to aerobes. Methods This was a retrospective review of 306 patients who met Musculoskeletal Infection Society (MSIS) criteria for PJI from 2014 to 2020 at the University of Iowa Hospitals and Clinics (UIHC). 38 patients with anaerobic PJI were compared to 268 patients with aerobic PJI. Statistical analyses were performed using Pearson’s Chi square, Fisher exact test, t-test, and binary logistic regression. Results PJI with anaerobes represented 12.4% of all PJI cases in our institution, which is higher than the 3-6% reported in literature. Patients with anaerobic PJI had longer duration of symptoms (19.4 weeks vs 10.9 weeks, p = 0.012), were more likely to have a sinus tract on exam (23.7% vs 5.9%, p &amp;lt; 0.001), less fever on presentation ( 13.2% vs 30.2%, p = 0.029), more radiographic abnormalities (50.0% vs 31.1%, p&amp;lt; 0.001), lower erythrocyte sedimentation rate (49.0mm/hr vs 67.7 mm/hr, p = 0.003), lower C-reactive protein (6.6 mg/dL vs 12.1mg/dL, p = 0.004), and more likely to be polymicrobial (42.1%vs 8.0%, p &amp;lt; 0.001) compared to aerobic PJI. There was a higher proportion of anaerobes in shoulder PJIs compared to other joints (39.5% vs 5.5%, p&amp;lt; 0.001). Two-stage exchange was the most common surgical treatment in patients with anaerobic PJI (39.4%) whereas debridement and implant retention was the most common (44.5%) surgical treatment done in patients with aerobic PJI. No significant differences were seen between the two groups in terms of recurrences. Independent factors associated with anaerobic infection were shoulder prosthetic joint (AOR 10.5, CI 3.4 - 32.8) and presence of sinus tract (AOR 10.1, CI 3.1 - 32.6). Conclusion Anaerobic cultures should be performed in patients with PJI, and they should especially be considered on the differential in patients with shoulder PJI, longstanding symptoms, sinus tract on examination and abnormalities noted on radiographs. Disclosures All Authors: No reported disclosures

Evaluation of painful total knee arthroplasty: an approach based on common etiologies for total knee arthroplasty revision.

A differential diagnosis with emphasis on the common indications for revision should be utilized in the workup of painful total knee arthroplasty (TKA). The physician should identify the exact etiology of the patient's pain to maximize outcomes from treatment. Evaluation for infection should be completed using the Musculoskeletal Infection Society (MSIS) criteria. When common causes of revision TKA do not appear to be the cause of the pain, less likely causes should be not be ignored. Further advancements such as pressure sensing devices may be able to improve patient satisfaction and decrease the incidence of pain following TKA.