Determining Diagnostic Thresholds for Acute Postoperative Periprosthetic Joint Infection

Dynamics of Synovial Fluid Markers Following Single-Stage Exchange and Debridement, Antibiotics, and Implant Retention Procedure With Topical Antibiotic Infusion in Treating Periprosthetic Joint Infection

BACKGROUND

Periprosthetic joint infection (PJI) is a severe complication following total joint arthroplasty. This study aimed to investigate the dynamics of synovial fluid markers following single-stage exchange arthroplasty or debridement, combined with antibiotics and implant retention with topical antibiotic infusion for PJI.

METHODS

This retrospective study analyzed patient records at a tertiary hospital from March 1, 2018, to May 1, 2023. Patients who received single-stage exchange arthroplasty or debridement, combined with antibiotics and implant retention, followed by intra-articular antibiotic infusion for PJI, were included. Basic demographic details, comorbidities, Charlson Comorbidity Index scores, microorganism profile, presence of sinus tract, and antibiotic treatment type were collected. Synovial fluid samples were collected preoperatively and postoperatively every two days for 14 days to quantify synovial white blood cell (WBC) count and polymorphonuclear cell percentage (PMN%).

RESULTS

The study included 140 patients who had a mean age of 63 years and a mean body mass index of 25. The results showed a steady decrease in synovial WBC count from preoperative levels to day 14 postoperatively. Patients who had successful outcomes had significantly higher preoperative WBC counts compared to those who had a treatment failure. The synovial PMN% initially increased postoperatively, peaking at days one to two, and then gradually declined. Patients who had successful outcomes showed a faster decline in PMN% compared to those who had persistent infections. Different bacteria exhibited varying preoperative synovial WBC counts and PMN%, but these differences were not statistically significant.

CONCLUSIONS

Monitoring synovial WBC count and PMN% can help distinguish between normal postoperative inflammation and persistent infection. Higher preoperative synovial WBC counts are associated with successful outcomes, suggesting their potential role in predicting treatment success. Future research with larger sample sizes is necessary to further validate these findings and improve the management and diagnosis of PJI.

Neutrophil-Lymphocyte Ratio as Predictor for Acute Infection After Primary Total Joint Arthroplasty in Rheumatoid Arthritis Patients

OBJECTIVES

Preoperative levels of certain inflammatory markers in the blood can predict acute infection after primary total joint arthroplasty in patients without inflammatory disease, but whether they can do so in patients with rheumatoid arthritis is unclear. The objectives of this study were to determine whether, with appropriate cut-off values, (1) preoperative levels of NLR predicted postoperative acute infection; and (2) preoperative plasma fibrinogen, monocyte-lymphocyte ratio, C-reactive protein or erythrocyte sedimentation rate predicted postoperative acute infection.

METHODS

We retrospectively analyzed 964 patients with rheumatoid arthritis who underwent primary total joint arthroplasty at our hospital between January 2010 and November 2020. We compared preoperative levels of inflammatory markers including neutrophil-lymphocyte ratio (NLR), monocyte-lymphocyte ratio (MLR), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), plasma fibrinogen (FIB) between patients who suffered acute infection or not within 90 days after surgery. The ability of markers to predict infection was assessed in terms of the area under receiver operating characteristic curves (AUC) based on optimal cut-off values determined from the Youden index.

RESULTS

Among the 964 patients, 27 (2.8%) experienced acute infection. Preoperative levels of individual inflammatory markers predicted infection with the following AUCs and cut-off values: NLR, 0.704 (cut-off: 2.528); MLR, 0.608 (0.2317); CRP, 0.516 (4.125 mg/L); ESR, 0.533 (66.5 mm/h); and FIB, 0.552 (3.415 g/L). The neutrophil-lymphocyte ratio showed diagnostic sensitivity of 92.6% and specificity of 43.3%, while the monocyte-lymphocyte ratio showed sensitivity of 77.8% and specificity of 46.3%.

CONCLUSION

The preoperative NLR shows some ability to predict acute infection after total joint arthroplasty in patients with rheumatoid arthritis. Monitoring this ratio, perhaps in conjunction with other markers not analyzed here, may be useful for optimizing the timing of surgery in order to minimize risk of postoperative infection.

Clinical Benefit of Using Differential Cutoff Values of Synovial C-Reactive Protein in Acute and Chronic Infected as Well as Aseptic Hip and Knee Revision Arthroplasties

BACKGROUND

It is unclear whether cutoff values for synovial C-reactive protein (syCRP) differ between acute and chronic infected as well as aseptic revision total hip arthroplasty (rTHA) and revision total knee arthroplasty (rTKA). We aimed to evaluate this and to compare the diagnostic accuracy of syCRP with serum C-reactive protein (seCRP), synovial white blood cell count, and polymorphonuclear leukocyte percentage (syPMN%).

METHODS

A total of 387 revision arthroplasties (83 rTHA, 304 rTKA) were analyzed for seCRP, syCRP, synovial white blood cell, syPMN%, and culture results. Using the International Consensus Meeting 2018 periprosthetic joint infection (PJI) criteria, 189 (42 rTHA, 147 rTKA) were classified as infected, and 198 (41 rTHA, 157 rTKA) were aseptic revisions. Diagnostic accuracy was assessed using receiver operating characteristic curves and area under the curve (AUC).

RESULTS

The optimal syCRP cutoff for PJI diagnosis among rTHA and rTKA < 90 days was 9.05 mg/L (AUC: 0.85) and 4.95 mg/L (AUC: 0.92), respectively. For > 90 days, the optimal syCRP cutoff was 3.00 mg/L (AUC: 0.90) for THA and 1.65 mg/L (AUC: 0.88) for TKA. In early and late acute PJI (n = 48), syCRP (45 of 48 = 94%) showed a higher positivity rate than seCRP (43 of 48 = 90%), WBC (38 of 48 = 79%), and PMN% (42 of 48 = 88%). A similar trend was observed in chronic PJI (n = 141): syCRP (110 of 141 = 78%), seCRP (104 of 141 = 74%), WBC (105 of 141 = 74%), and PMN% (101 of 141 = 72%). Among 189 confirmed PJIs, both WBC and PMN% were negative in 34 of 189 (18%), of which syCRP and seCRP were positive in 13 of 34 (38%) and 10 of 34 (29%), respectively.

CONCLUSIONS

The syCRP may be useful as a supplementary biomarker in cases with suspected PJI, but normal synovial cell count. Our data suggest that different cutoff values based on the type of joint and the chronicity of rTHA and rTKA are clinically useful.

Comparative Diagnostic Value of Serological and Synovial Tests for Periprosthetic Joint Infections: A Comprehensive Analysis

Background

Prompt diagnosis of periprosthetic joint infections (PJIs) is crucial for providing optimal care. Currently, there are no gold-standard tests available. An ideal test would be simple to implement, cost-effective, and readily available. We aimed to determine the best single or combined serological or synovial markers for diagnosing PJIs.

Methods

There were 177 of 313 patients who had PJIs between April 2012 and March 2023 and a control group of 60 patients who were included in this retrospective review. The PJIs were diagnosed using Musculoskeletal Infection Society (MSIS) and European Bone and Joint Infection Society (EBJIS) criteria. Serum (C-reactive protein [CRP], white blood-cell [WBC] count, neutrophil-lymphocyte ratio [NLR], polymorphonuclear neutrophil percentage [PMN%]), and synovial fluid (WBC, NLR, PMN%) parameters were compared between the 2 groups. We determined the sensitivity, specificity, area under the curve (AUC), and cutoff values (COV) for each marker. We determined the best combination of markers to diagnose PJIs. There was no statistical significance between the demographic data of the control and treatment groups.

Results

The S-CRP had the highest AUC of 0.912 with a COV of 16.15 mg/dL (Sensitivity 79.6%, Specificity 97.8%). The combination of tests, S-CRP, synovial fluid (SF-WBC), and S-NLR demonstrated the highest AUC of 0.946 (Sensitivity 93%, Specificity 90.9%). The COV for SF-WBC was 5.75 cells/μL (AUC 0.803; Sensitivity 70.3%, Specificity 97.1%); S-NLR COV was 3.659 (AUC 0.803; Sensitivity 67.3%, Specificity 88%).

Conclusion

We found the combination of S-CRP, SF-WBC, and S-NLR to be valuable in diagnosing PJI with high sensitivities and specificities. It can be easily implemented by clinicians without additional cost or equipment. It is important to use this with a thorough clinical and physical examination as well as other modalities (i.e., MSIS/EBJIS criteria).

Level of Evidence

Retrospective Comparative Study-Level III evidence. See Instructions for Authors for a complete description of levels of evidence.

Nomogram to predict periprosthetic joint infection after total hip arthroplasty using laboratory tests

BACKGROUND

Periprosthetic joint infection (PJI) is a catastrophic complication after joint arthroplasty. This study aimed to analyze the relationship between laboratory tests and PJI and establish a nomogram for predicting risks of PJI after total hip arthroplasty (THA).

MATERIALS AND METHODS

The clinical data of patients who underwent THA from January 2015 to December 2020 were retrospectively analyzed. Demographic and relevant clinical information of patients was collected; independent risk factors associated with PJI were determined by univariate and multivariate logistic regression analysis, and receiver operating characteristics (ROC) were drawn to analyze the specificity and sensitivity of each risk factor. Risk factors are included in the nomogram. Calibration curve and decision curve analysis were used to evaluate the predictive accuracy and discriminability of the model.

RESULTS

A total of 589 patients were enrolled in the study, of whom 87 were eventually diagnosed with PJI. Multivariate logistic regression analysis showed that serum C-reactive protein, erythrocyte sedimentation rate, polymorphonuclear neutrophils, D-dimer, and platelet count were independent risk factors for PJI after THA. The ROC curve analysis model of multivariate combined diagnosis had good diagnostic value, sensitivity was 77.01%, and specificity was 75.51%. The calibration curve shows good agreement between the prediction of the line graph and the actual observed results. The decision curve shows that the nomogram has a net clinical benefit.

CONCLUSIONS

The changes in serum C-reactive protein, erythrocyte sedimentation rate, polymorphonuclear neutrophils, D-dimer, and platelet count are related to the occurrence of PJI after hip arthroplasty. The nomogram prediction model established in this study is promising for the screening of PJI after hip arthroplasty.

LEVEL OF EVIDENCE

Level III evidence. Non-randomized controlled cohort/follow-up study.

Synovial glucose and serum-to-synovial-glucose ratio perform better than other biomarkers for the diagnosis of acute postoperative prosthetic knee infection

Introduction: In native septic arthritis, synovial glucose is a well-established diagnostic marker. However, its diagnostic utility in periprosthetic joint infection (PJI) remains unexplored. Given the diagnostic challenges of acute postoperative PJI, we hypothesized that synovial glucose could serve as a valuable biomarker and aimed to evaluate its diagnostic accuracy. Material and methods:  This is a retrospective diagnostic study in acute postoperative PJI in total knee arthroplasty (TKA). We reviewed all TKA surgeries performed in the past 10 years and cross-checked those patients that consulted to our emergency room during the first 90 d after TKA surgery for knee-related symptoms. We calculated the serum-to-synovial-glucose ratio for each patient (serum-to-synovial-glucose ratio = [(serological glucose - synovial glucose) / serological glucose]), and we formed the receiver operating characteristic (ROC) curves for synovial glucose, serum-to-synovial-glucose ratio, serum C-reactive protein (CRP), synovial white blood cell (s-WBC) count, and polymorphonuclear cell percentage (PMN%); then we extracted the optimal cutoff values. Results: The optimal cutoffs for diagnosing acute postoperative PJI were < 44 mg dL-1 for synovial glucose and > 0.69 for serum-to-synovial-glucose ratio. The area under the curve (AUC) values were 0.861 and 0.889, respectively. ROC curves for serum CRP, s-WBC count, and PMN% showed AUC values of 0.69, 0.714, and 0.66, respectively. The combined ROC curve analysis for serum CRP, s-WBC count, and PMN% showed an AUC of 0.722. When adding synovial glucose, the AUC was 0.859 and with serum-to-synovial-glucose ratio we achieved an AUC of 0.876. Conclusion: Synovial glucose and serum-to-synovial-glucose ratio demonstrated good diagnostic potential for acute postoperative PJI following TKA. These biomarkers exhibited superior accuracy compared to the combination of serum CRP, s-WBC count, and PMN%.

Diagnostic Thresholds of Synovial Markers for Acute Periprosthetic Joint Infection: One Size Does Not Fit All

BACKGROUND

The diagnosis of periprosthetic joint infection (PJI), particularly during the early postoperative period, remains challenging. The purpose of this multicenter study was to assess the utility of synovial white blood cell (WBC) count and polymorphonuclear leukocyte percentage (PMN%) in the diagnosis of acute PJI at different time intervals after primary total joint arthroplasty (TJA).

METHODS

This retrospective study identified 225 patients who underwent a joint aspiration within 90 days of their primary TJA at three institutions. A PJI was defined as revision TJA for infection within 7 days of joint aspiration with two positive cultures isolating the same organism. Patients were considered aseptic if they had no reoperation for up to 1 year after arthrocentesis. Receiver operator characteristic curves were used to assess the utility of WBC count and PMN% in the diagnosis of acute PJI at zero to 15, 15 to 45, and 45 to 90 days. Youden's index was used to identify the optimal cutoffs at each time interval. A pairwise comparison was performed to compare the area under the curve (AUC) of the two markers. There were 214 patients included. Of these, 81 (37.9%) were infected and 133 (62.1%) were aseptic.

RESULTS

The optimal cutoff at zero to 15 days was 21,003 cells/μL for WBC count (AUC 0.937, sensitivity 88.0%, specificity 100%) and 92.0% for PMN% (AUC 0.638, sensitivity 56.0%, specificity 68.4%). Although the diagnostic threshold for WBC count decreased to 5,111 cells/μL at 15 to 45 days and to 2,503 cells/μL at 45 to 90 days, the cutoffs for PMN% did not downtrend in the same fashion (80% at 15 to 45 days; 86% at 45 to 90 days). Using pairwise comparison, the AUC for WBC count was higher than that of PMN% at 0 to 15 days (P = 0.002); however, there was no difference in AUCs at either 15 to 45 days (P = 0.438) or 45 to 90 days (P = 0.826).

CONCLUSIONS

Based on our findings, it appears that there may be a role for diagnostic thresholds for the identification of acute PJI that are specific to the timing of joint aspiration after primary TJA.

Serum C-Reactive Protein to Hemoglobin Ratio: Novel Biomarkers for the Diagnosis of Chronic Periprosthetic Joint Infection

BACKGROUND

Despite several markers being evaluated and available in recent years, diagnosing periprosthetic joint infection (PJI) remains challenging. There is a pressing need to explore reliable, economical, convenient, highly sensitive, and specific diagnostic biomarkers to diagnose PJI. This study aimed to investigate the diagnostic value of combined serum markers with C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) in PJI.

METHODS

A total of 841 revision arthroplasty cases, including 435 PJI and 406 non-PJI patients, were enrolled from January 2010 through December 2022. The diagnostic values of CRP, ESR, CRP + ESR, CRP or hemoglobin ratio (CHR), CRP or albumin ratio, CRP or hemoglobin + albumin ratio, ESR or hemoglobin ratio, ESR or albumin ratio, ESR or hemoglobin + albumin ratio, and hemoglobin + albumin were evaluated using sensitivity, specificity, and receiver operating characteristics analysis with area under the curve. The optimal threshold was determined using the Youden index.

RESULTS

The CHR had the highest area under the curve (0.87, 95% CI [confidence interval] 0.85 to 0.90) and sensitivity (0.81, 95% CI: 0.77 to 0.85), compared to other markers. The CHR exhibited reliable diagnostic adequacy for PJIs caused by low-virulent organisms (sensitivity 0.83, 95% CI: 0.76 to 0.89; specificity 0.83, 95% CI: 0.79 to 0.86). However, CHR displayed poor sensitivity (0.77, 95% CI: 0.67 to 0.86) in patients who have diabetes.

CONCLUSIONS

The CHR demonstrated better diagnostic strength in detecting chronic PJI than other classical markers, especially in identifying low-grade infections. Our findings offer new insights into a more accurate and comprehensive picture of pathogens and hosts, thereby improving the accuracy of diagnostic algorithms.

Infectiological Outcome of Total Hip and Total Knee Arthroplasty in Post-Traumatic and Primary Osteoarthritis

Background: The objective of this study was to compare infection rates, pathogen species detection and antimicrobial susceptibility testing in patients with total hip arthroplasty (THA) and total knee arthroplasty (TKA) following post-traumatic osteoarthritis (PTOA) and primary osteoarthritis (POA). Results: Patients undergoing both THA and TKA were significantly more likely to have a PJI after PTOA than after POA (THA: 2.5% vs. 10.2%, p = 0.003; TKA: 3.2% vs. 10.3%, p = 0.028). The most frequently detected pathogen in both THA and TKA was Staphylococcus spp. Among patients with a PJI in THA, Staphylococcus spp. was detected in 47% after POA and 60% after PTOA. Among patients with a PJI in TKA, Staphylococcus spp. was isolated in 59% after POA and 80% after PTOA. The remaining pathogens were mainly Enterococcus spp., Enterobacterales and anaerobic bacteria. After THA, beta-lactam-resistant staphylococcal isolates were detected more frequently in PTOA patients than in POA patients (13% vs. 100%, p = 0.024). There was no difference in the beta-lactam staphylococcal resistance rate in patients after TKA (20% vs. 25%, p = 0.945). Furthermore, an analysis of susceptibility testing from all groups showed that significantly more pathogens were susceptible to vancomycin than to cefuroxime (76% vs. 45%, p < 0.001) or clindamycin (76% vs. 52%, p = 0.007). Methods: A retrospective analysis was performed using clinic-owned data during the period January 2016-December 2020. A total of 1485 patients following primary implantation of THA or TKA due to PTOA or POA were included. Early-onset periprosthetic joint infection (PJI), defined according to the 2018 Definition of Periprosthetic Hip and Knee Infection Criteria, was evaluated. Conclusions: Therefore, the use of vancomycin as a perioperative prophylaxis should be discussed under benefit/risk consideration in further studies.

Early Versus Late Periprosthetic Joint Infection After Total Knee Arthroplasty: Do Patient Differences Exist?

BACKGROUND

Periprosthetic joint infection (PJI) is a devastating complication following total knee arthroplasty (TKA). Little evidence exists comparing those with early versus late PJI. The purpose of the study was to determine comorbidity profile differences between patients developing early and late PJI.

METHODS

There were 72,659 patients undergoing primary TKA from 2009 to 2021, who were identified from a commercial claims and encounters database. Subjects diagnosed with PJI were categorized as either 'early' (within 90 days of index procedure) or 'late' (> 2 years after index arthroplasty). Non-infected patients within these periods served as control groups following 4:1 propensity score matching on other extraneous variables. Logistic regression analyses were performed comparing comorbidities between groups.

RESULTS

Patients were significantly younger in the late compared to the early infection group (58.1 versus 62.4 years, P < .001). When compared to those with early PJI, patients who had chronic kidney disease (13.3 versus 4.1%; OR [odds ratio] 5.17, P = .002), malignancy (20.4 versus 10.5%; OR 2.53, P = .009), uncomplicated diabetes (40.8 versus 30.6%; OR 2.00, P = .01), rheumatoid arthritis (9.2 versus 3.3%; OR 2.66, P = .046), and hypertension (88.8 versus 81.6%; OR 2.17, P = .04), were all significant predictors of developing a late PJI.

CONCLUSIONS

When compared to patients diagnosed with early PJI following primary TKA, the presence of chronic kidney disease, malignancy, uncomplicated diabetes, rheumatoid arthritis, and hypertension, were independent risk factors for the development of late PJI. Younger patients who have these comorbidities may be targets for preoperative optimization interventions that minimize the risk of PJI.

The Association of Dental Caries or Dental Implant Placement Within One Year of Primary Total Hip Arthroplasty on Medical and Implant Complications

BACKGROUND

Total hip arthroplasty (THA) adverse events among patients who have dental diagnoses remain unclear. We sought to determine if dental caries or dental implant placements increased (1) 90-day medical complications, (2) 90-day readmissions, and (3) 2-year implant-related complications, including periprosthetic joint infections (PJIs) after THA.

METHODS

A nationwide database for primary THAs from 2010 to 2021 was queried to compare 3 patient cohorts. Patients who had a history of dental implants or caries within 12 months prior to THA (n = 1,179) or 12 months after THA (n = 1,218) were case-matched to patients who did not have dental history (n = 6,090) by age and comorbidities. Outcomes included 90-day complications, 90-day readmissions, and 2-year implant-related complications. Logistic regression models computed the odds ratios (ORs) of complications and readmissions. P values less than .006 were significant.

RESULTS

Patients who had dental caries or implant placement 12 months before or after THA experienced 1.6-fold greater odds of 90-day medical complications compared to case-matched patients. Readmissions within 90 days increased for patients who had a dental history before (11.7% versus 8.3%; OR: 1.49, P < .0001) and after (14.2% versus 8.3%; OR: 1.84, P < .0001) THA compared to case-matched patients. A dental caries diagnosis or dental implant placement within 12 months following THA increased 2-year implant complications compared to case-matched patients (15.2% versus 9.3%; OR: 1.69, P < .0001), including PJIs (5.3% versus 2.8%; OR: 1.98, P < .0001), dislocations (4.4% versus 2.7%; OR: 1.63, P = .002), and THA revisions (3.9% versus 2.5%; OR: 1.61, P = .005).

CONCLUSIONS

Dental diagnoses within 12 months of THA are associated with increased medical complications. Dental diagnoses occurring 12 months after THA are associated with greater implant-related complications, including PJIs. Delaying invasive dental procedures for 12 months after THA may be advisable.

Advancements in treatment strategies for periprosthetic joint infections: A comprehensive review

Periprosthetic joint infection (PJI) presents a critical challenge in orthopedic care, contributing to significant patient morbidity and healthcare costs. This burden is expected to increase secondary to growing demand for total joint arthroplasty (TJA). Despite the profound significance of PJI, there is currently no universally accepted "gold standard" diagnostic criteria using serum biomarker thresholds; latest criteria fail to differentiate acute infections from chronic or consider time since initial surgery. Furthermore, contemporary PJI treatment, which conventionally requires 2-stage revision surgery in conjunction with rigorous antibiotic treatment, can be particularly taxing on patients. Fortunately, recent years have seen marked evolution in both PJI diagnosis and treatment methods. Contemporary research supports time-dependent serum biomarker thresholds with greater sensitivity and specificity than previously reported, as well as alternative surgical options which may be more suitable for certain patients. The following narrative review aims to describe the significance and pathogenesis of PJI before characterizing current challenges, novel innovations, and the future landscape of PJI diagnosis and management. Here, we spotlight the emerging utility of novel biomarkers and metagenomic next-generation sequencing for diagnosis, advancements in patient-centered surgical outcome prediction tools for PJI risk assessment and prevention, and evolving surgical techniques including 1-stage and a "hybrid" 1.5-stage revision surgeries. Additionally, we explore cutting-edge therapeutic modalities including peptide and bacteriophage-based treatments, intraoperative anti-biofilm gel, the VT-X7 antibiotic pump, and promising immune-based interventions. Ultimately, these advancements hold the potential to revolutionize PJI management, offering hope for improved outcomes and reduced burdens on healthcare systems.

Preoperative Laboratory Values Predicting Periprosthetic Joint Infection in Morbidly Obese Patients Undergoing Total Hip or Knee Arthroplasty

BACKGROUND

Morbidly obese patients are an ever-growing high-risk population undergoing total hip arthroplasty (THA) and total knee arthroplasty (TKA) for end-stage osteoarthritis. This study sought to identify preoperative laboratory values that may serve as predictors of periprosthetic joint infection (PJI) in morbidly obese patients undergoing THA or TKA.

METHODS

All morbidly obese patients with preoperative laboratory data before undergoing primary elective TKA or THA were identified using the Premier Healthcare Database. Patients who developed PJI within 90 days after surgery were compared with patients without PJI. Laboratory value thresholds were defined by clinical guidelines or primary literature. Univariate and multivariable regression analyses were utilized to assess the association between PJI and preoperative laboratory values, including total lymphocyte count, neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), monocyte-lymphocyte ratio (MLR), systemic immune-inflammation index (SII), albumin level, platelet count, albumin-globulin ratio, hemoglobin level, and hemoglobin A1c.

RESULTS

Of the 6,780 patients identified (TKA: 76.67%; THA: 23.33%), 47 (0.69%) developed PJI within 90 days after surgery. The rate of PJI was 1.69% for patients with a hemoglobin level of <12 g/dL (for females) or <13 g/dL (for males), 2.14% for those with a platelet count of <142,000/µL or >417,000/µL, 1.11% for those with an NLR of >3.31, 1.69% for those with a PLR of >182.3, and 1.05% for those with an SII of >776.2. After accounting for potential confounding factors, we observed an association between PJI and an abnormal preoperative NLR (adjusted odds ratio [aOR]: 2.38, 95% confidence interval [CI]: 1.04 to 5.44, p = 0.039), PLR (aOR: 4.86, 95% CI: 2.15 to 10.95, p < 0.001), SII (aOR: 2.44, 95% CI: 1.09 to 5.44, p = 0.029), platelet count (aOR: 3.50, 95% CI: 1.11 to 10.99, p = 0.032), and hemoglobin level (aOR: 2.62, 95% CI: 1.06 to 6.50, p = 0.038).

CONCLUSIONS

This study identified preoperative anemia, abnormal platelet count, and elevated NLR, PLR, and SII to be associated with an increased risk of PJI among patients with a body mass index of ≥40 kg/m 2 . These findings may help surgeons risk-stratify this high-risk patient population.

LEVEL OF EVIDENCE

Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

An overview of the current diagnostic approach to Periprosthetic Joint Infections

The diagnosis of periprosthetic joint infections (PJI) presents a formidable challenge to orthopaedic surgeons due to its complex and diverse manifestations. Accurate diagnosis is of utmost importance, as even mild pain following joint replacement surgery may indicate PJI in the absence of a definitive gold standard diagnostic test. Numerous diagnostic modalities have been suggested in the literature, and international societies have continually updated diagnostic criteria for this debilitating complication. This review article aims to comprehensively examine the latest evidence-based approaches for diagnosing PJI. Through a thorough analysis of current literature, we explore promising diagnostic strategies that have demonstrated effectiveness in identifying PJI. These strategies encompass the utilization of laboratory markers, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), alongside imaging techniques such as magnetic resonance imaging (MRI) and leukocyte scintigraphy. Additionally, we highlight the importance of synovial fluid analysis, including the potential role of alpha-defensin as a biomarker, and examine evolving international diagnostic criteria to standardize and improve diagnostic accuracy.

Risk Factors for Therapeutic Failure and One-Year Mortality in Patients with Intramedullary Nail-Associated Infection after Trochanteric and Subtrochanteric Hip Fracture Repair

Despite the implications of trochanteric and subtrochanteric intramedullary (IM) nail infection for patients with hip fracture, little is known about risk factors for therapeutic failure and mortality in this population. We performed a retrospective observational analysis including patients diagnosed with trochanteric and subtrochanteric IM nail infection at a Spanish academic hospital during a 10-year period, with a minimum follow-up of 22 months. Of 4044 trochanteric and subtrochanteric IM nail implants, we identified 35 cases of infection during the study period (0.87%), 17 of which were chronic infections. Patients with therapeutic failure (n = 10) presented a higher average Charlson Comorbidity Index (CCI) (5.40 vs. 4.21, p 0.015, CI 0.26-2.13) and higher rates of polymicrobial (OR 5.70, p 0.033, CI 1.14-28.33) and multidrug-resistant (OR 7.00, p 0.027, CI 1.24-39.57) infections. Upon multivariate analysis, polymicrobial infection and the presence of multidrug-resistant pathogens were identified as independent risk factors for therapeutic failure. Implant retention was associated with an increased risk of failure in chronic infection and was found to be an independent risk factor for overall one-year mortality in the multivariate analysis. Our study highlights the importance of broad-spectrum empirical antibiotics as initial treatment of trochanteric and subtrochanteric IM nail-associated infection while awaiting microbiological results. It also provides initial evidence for the importance of implant removal in chronic IM-nail infection.

Diagnostic cutoff values of synovial fluid biomarkers for acute postoperative prosthetic joint infection: a systematic review and meta-analysis

Introduction: The assessment of white blood cell (WBC) count and polymorphonuclear cell (PMN) percentage in synovial fluid can help in the diagnosis of acute postoperative peri-prosthetic joint infection (PJI). Their cutoff values, which would differ from those for chronic PJI, have not yet been determined in acute postoperative PJI. The aim of this study was (1) to analyse studies reporting the optimal cutoff values for WBC count and the PMN percentage in synovial fluid and (2) to determine which is the best diagnostic tool for acute postoperative PJI. Methods: We performed a systematic review (SR) of primary studies analysing WBC count and the PMN percentage for diagnosis of acute postoperative PJI. A search was performed in MEDLINE and EMBASE. We studied the risk of bias and quality assessment. We extracted data on cutoff values, sensitivity, specificity, positive and negative predictive value, area under the curve, and accuracy. We calculated the diagnosis odds ratio (DOR), performed the meta-analysis and summarized receiver operating curves (sROCs) for WBC count and the PMN percentage. Results: We included six studies. WBC count showed a DOR of 123.61 (95 % CI: 55.38-275.88), an sROC with an area under the curve (AUC) of 0.96 (SE: 0.009) and a Q index of 0.917. The PMN percentage showed a summary DOR of 18.71 (95 % CI: 11.64-30.07), an sROC with an AUC 0.88 (SE: 0.018) and a Q index of 0.812. Conclusion: We concluded that WBC count and the PMN percentage are useful tests for the diagnosis of acute PJI; WBC is the more powerful of the two. Studies centred on other synovial fluid biomarkers not yet studied could help in this diagnosis.

Graphic type differentiation of cell count data for diagnosis of early and late periprosthetic joint infection: A new method

BACKGROUND

Graphic type differentiation of cell count data of synovial aspirates is a new method for the diagnosis of early and late periprosthetic joint infection.

OBJECTIVE

The aim of the study was to analyse if the same 6 LMNE-types can be differentiated in the new Yumizen H500 cell counter as it was the case for the old cell counter ABX Pentra XL 80 of previous publications, to verify if the erythrocyte and thrombocyte curves of the new device give additional information and to calculate the difference of cell count in LMNE-type I and III (with abrasion) in the cell counter and in the manual counting chamber (Neubauer improved).

METHODS

450 aspirates of 152 total hip arthroplasties and 298 knee arthroplasties obtained for the diagnosis of periprosthetic joint infection were analysed with the Yumizen H500.

RESULTS

All LMNE-matrices of the 450 aspirates could assigned to one of the six LMNE-types. There were 76 LMNE-type I, 72 LMNE-type II, 14 LMNE-type III, 241 LMNE-type IV, 36 LMNE-type V and 12 LMNE-type VI. The erythrocyte and thrombocyte distribution curves were very helpful for differentiation of hematoma and infection. The cell count in the manual counting procedure was lower than in the cell counter: for the LMNE-type I (abrasion type) the median of the difference was 925/μL (median) and for the LMNE-type III (combined type of infection and abrasion) 3570/μL (median).

CONCLUSION

The described graphic type differentiation is a new and helpful method for differentiation of hematoma and early PJI as well as abrasion and late PJI.

Refining the Role of Routine Synovial Alpha-Defensin in Periprosthetic Joint Infection Following Total Knee Arthroplasty: An Analysis of Limitations

BACKGROUND

The utility of the synovial alpha-defensin test in diagnosing periprosthetic joint infections (PJIs) remains controversial. This study aimed to examine the diagnostic utility of this test.

METHODS

A retrospective review was conducted to identify adults evaluated for PJI following total knee arthroplasty at a single institution. Patient demographics, laboratory results, and operative details were recorded. Using the 2018 Musculoskeletal Infection Society (MSIS) criteria, cases were categorized as definitive, inconclusive, or negative for PJI. The sensitivity, specificity, positive predictive value, and negative predictive value of each MSIS criterion was determined. The number of patients whose PJI diagnosis was contingent on alpha-defensin positivity was calculated.

RESULTS

Overall, 172 total knee arthroplasty patients were included, who had an average age of 70.4 years (range, 39 to 95). Of the 21 patients who met major criteria, 20 (95.2%) were alpha-defensin positive. Of the remaining 151 patients, 85 did not meet minor criteria, all of whom were alpha-defensin negative. Among the 30 patients who met minor criteria, 28 (93.3%) were alpha-defensin positive and 2 (6.7%) were negative. The remaining 36 patients were deemed inconclusive preoperatively. In total, alpha-defensin testing changed the diagnosis in only 9 of 172 patients (5.2%). The sensitivity, specificity, positive predictive value, and negative predictive value of alpha-defensin in this cohort were 94.1, 100, 100, and 97.6, respectively.

CONCLUSION

Alpha-defensin may assist in the diagnosis of PJI when a preoperative workup is inconclusive. However, this test is often unnecessary when the diagnosis of PJI can be made using the 2018 MSIS criteria.

Serum acute-phase protein concentrations following uncomplicated total hip arthroplasty in dogs

OBJECTIVES

To establish preoperative and postoperative serum C reactive protein (CRP) and serum amyloid A (SAA) levels in dogs undergoing uncomplicated total hip arthroplasty (THA).

STUDY DESIGN

Prospective clinical trial.

ANIMALS

Eighteen client-owned dogs.

METHODS

Dogs undergoing THA were recruited. Serum CRP and SAA levels were measured in all dogs the day prior to surgery, and 3 and 6 months following surgery. All dogs received a physical examination and underwent radiography at each visit, and dogs with complications were excluded from the study. For continuous numeric data, histograms were generated and evaluated for normality. A 1-way repeated measures ANOVA was performed to find differences between time points.

RESULTS

No complications were encountered in any of the recruited dogs. Median age was 30 months (12-66), and the median bodyweight was 27.3 kg (22.3-40.2). Mean CRP concentrations in the preoperative, 3-month, and 6-month periods were 3.8 mg/L ± 4.4, 0.8 mg/L ± 1.9, and 1.4 mg/L ± 1.4, respectively. The mean SAA concentrations in the preoperative, 3-month, and 6-month periods were 13.9 mg/L ± 8.8, 14.1 mg/L ± 12.6, and 18.4 mg/L ± 15.1, respectively. There were no differences for each parameter between time points.

CONCLUSION

C-reactive protein and SAA levels were consistent with levels previously established for noninflammatory and normal conditions in dogs.

CLINICAL SIGNIFICANCE

Postoperative CRP and SAA concentrations were low by 3 months following uncomplicated THA.

A New Graphic Type Differentiation of Cell Account Determination for Distinguishing Acute Periprosthetic Joint Infection from Hemarthrosis

Aims: This study evaluates the value of a new graphic representation of cell count data of synovial fluid in the diagnosis of acute periprosthetic joint infection (PJI). Methods: A total of 75 patients with revisions of 48 primary total knee and 27 hip arthroplasties within the first six weeks after surgery were analyzed with cultivation of the synovial fluid and determination of its cell count as well as microbiological and histological analyses of the periprosthetic tissue obtained during the revision surgery using the ICM classification. The synovial fluid was additionally analyzed for graphic representation of the measured cells using LMNE-matrices. Results: A total of 38 patients (50.7%) had an infection. The following types of LMNE matrices could be differentiated: the indeterminate type (IV) in 14.7%, the infection type (II) in 5.3%, the hematoma type (V) in 33.3%, and the mixed type (VI; infection and hematoma) in 46.7%. Differentiation of LMNE types into infection (types II and VI) and non-infection (types IV and V) resulted in a sensitivity of 100%, a specificity of 97.3%, and a positive likelihood ratio of 37.0. The cell count measurement showed a sensitivity of 78.9%, a specificity of 89.2%, and a positive likelihood ratio of 7.3 at a cut-off of 10,000 cells. The percentage of polymorphonuclear leukocytes showed a sensitivity of 34.2%, a specificity of 100%, and a positive likelihood ratio of >200 at a cut-off of 90%. Conclusion: The graphic representation of the cell count analysis of synovial aspirates is a new and helpful method for differentiating between genuine early periprosthetic infections and postoperative hemarthrosis.

C-reactive protein during the first 6 postoperative days after total hip arthroplasty cannot predict early periprosthetic infection

INTRODUCTION

Periprosthetic joint infection (PJI) after total hip arthroplasty (THA) remains a serious complication in orthopaedic surgery. C-reactive protein (CRP) is widely used as a marker to screen for inflammatory complications. The early postoperative course is well known, but knowledge about the predictive value of CRP in the first 6 postoperative days for detecting an acute postoperative PJI is lacking.

METHODS

We retrospectively analyzed the inpatient course of CRP of all primary THA and THA with acute PJI within 28 days in our hospital from 2013 to 2021. A receiver-operating curve (ROC) analysis was performed and the best CRP threshold for detecting an acute PJI based on Youden's-index was calculated and an area-under-the curve (AUC) analysis of the threshold was performed.

RESULTS

33 of 7042 patients included had an acute PJI within 28 days. Patients with acute PJI were older, had a higher BMI and longer operation time and suffered more often from diabetes mellitus. A preoperatively elevated CRP was a risk factor for PJI. CRP was significantly higher in the PJI group on postoperative days 3 and 5. Threshold values were calculated to be 152 mg/l on day 3 and 73 mg/l on day 5. However, these values had a low sensitivity (75%, 76%) and specificity (67%, 61%).

CONCLUSION

Especially considering the decreasing length of stay after THA, the question of the usefulness of regular inpatient CRP checks arises. AUC analysis of the ROC showed a poor diagnostic accuracy in almost all cases. Only the dynamic analysis of the maximum CRP value to the lowest CRP value with a decrease of 102.7 mg/l showed a fair accuracy. This calls into question the clinical relevance of CRP in the first postoperative week for detection of acute postoperative PJI.

Synovial calprotectin is a reliable biomarker for periprosthetic joint infections in acute-phase inflammation - a prospective cohort study

PURPOSE

Diagnosing periprosthetic joint infections (PJI) are challenging and may be hampered by the presence of other causes of local inflammation. Conventional synovial and serum markers are not reliable under these circumstances. Synovial calprotectin has been recently shown as a promising biomarker for PJI in total hip (THA) and total knee arthroplasty (TKA). The aim of this study is to investigate if calprotectin is reliable for PJI diagnosis in cases with accompanying inflammation due to recent surgery, dislocation or implant breakage in primary and revision TKA and THA.

METHODS

Thirty-three patients were included in this prospective study between July 2019 and October 2021 (17 patients undergoing surgery < 9 months, 11 dislocations, five implant breakage, respectively). Synovial white blood cell count (WBC), percentage of polymorphonuclear neutrophils (PMC), serum C-reactive protein (CRP) and synovial calprotectin, using a lateral-flow-assay, were analysed. These parameters were tested against a modified European-Bone-and-Joint-Infection-Society (EBJIS) definition with adjusted thresholds to account for the local inflammation. Statistic quality criteria were calculated and compared using a binary classification test.

RESULTS

Seventeen patients were classified as confirmed infections according to the modified EBJIS definition (13 THA and 4 TKA). The calprotectin assay yielded a sensitivity of 0.88 (0.64, 0.99), a specificity of 0.81 (0.54, 0.96), a positive predictive value (PPV) of 0.83 (0.59, 0.96) and a negative predictive value (NPV) of 0.87 (0.60, 0.98).

CONCLUSIONS

Even in the presence of local inflammation due to other, non-infectious causes, calprotectin is a reliable diagnostic parameter for the detection of a PJI in primary and revision THA and TKA.

Recent Antibiotic Treatment Impacts Serum and Synovial Laboratory Values in Early Periprosthetic Joint Infection Workup

BACKGROUND

Accurately detecting early postoperative periprosthetic joint infection (PJI) following total hip arthroplasty (THA) and total knee arthroplasty (TKA) remains challenging. The purpose of our study was to determine the impact of antibiotics given prior to laboratory evaluation on the reliability of serologic and synovial fluid tests to identify PJI in the early postoperative period.

METHODS

We identified 49,861 primary total hip arthroplasties and total knee arthroplasties performed between 2000 and 2019. Among these patients, 21 hips and 28 knees that underwent arthrocentesis within 12 weeks of their arthroplasty were identified as infected. Patients who had received antibiotics within 2 weeks prior to laboratory evaluation were compared to those who had not. Median values of C-reactive protein, erythrocyte sedimentation rate, synovial white blood cell (WBC) count, synovial neutrophil percentage, and synovial absolute neutrophil count were compared between groups. The false negative rate for detecting PJI using laboratory values was compared using published cutoffs for PJI in the early postoperative period.

RESULTS

Median values of C-reactive protein (105 vs 22 mg/L; P = .006), synovial WBC count (57,591 vs 4,473 cells/μL; P = .003), synovial neutrophil percentage (94% vs 76%; P = .004), and synovial absolute neutrophil count (50,748 vs 2,804 cells/μL; P < .001) were significantly lower in patients who received antibiotics compared to those who did not. False negative rates for detecting PJI were significantly higher for synovial WBC and synovial neutrophil percentage in patients treated with antibiotics compared to untreated patients.

CONCLUSION

False negative rates for detecting early PJI when using published cutoffs were markedly higher in antibiotic-treated patients compared to untreated patients for synovial WBC count and synovial neutrophil percentage.

LEVEL OF EVIDENCE

Level IV retrospective review.

Delayed normalization of C-Reactive protein and erythrocyte sedimentation rate was not associated with inferior clinical outcomes after total knee arthroplasty

BACKGROUND

The purpose of this study aimed to identify the proportion of patients with delayed normalization of C-reactive protein (CRP) and Erythrocyte sedimentation rate (ESR) after TKA, to determine postoperative thresholds predictive of prolonged elevation. Further, we aimed to determine if the clinical outcomes of patients with prolonged elevation were inferior to those without prolonged elevation.

METHODS

The records of 211 unilateral and 320 bilateral TKA were reviewed. Patients were divided into the normal and elevation group based on CRP and ESR levels at 6 weeks and 3 months. The temporal pattern of CRP and ESR change in both groups was compared, and thresholds predictive of elevation at 6 weeks and 3 months were identified. Further, the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index and Tegner activity scale of both groups at 6 months, 1 year, and 2 years after TKA were compared.

RESULTS

The proportion of patients with elevated CRP and ESR at 6 weeks and 3 months was CRP: 24.2%, 10%, ESR: 51.6%, 29.9% in unilateral and CRP: 31.5%, 10.6%, ESR: 58.1%, 42.7% in bilateral TKA. The thresholds for elevation at 6 weeks and 3 months were 9.5 mg/dL, 11.4 mg/dL (CRP at 6 weeks) and 81.5 mm/h, 74.5 mm/h (ESR at 3 months). There was no difference in the WOMAC score and Tegner activity scale between both groups.

CONCLUSIONS

CRP and ESR are often elevated for a prolonged period even in the absence of infection after TKA. Such cases show distinct temporal patterns, which are predictable, and do not appear to have a significant effect on clinical outcome.

Laboratory Value Effectiveness in Predicting Early Postoperative Periprosthetic Joint Infection After Total Hip Arthroplasty

BACKGROUND

Diagnosing early periprosthetic joint infection (PJI) after primary total hip arthroplasty (THA) remains challenging. We sought to validate optimal laboratory value cutoffs for detecting early PJIs in a series of primary THAs from one institution.

METHODS

We retrospectively identified 22,795 primary THAs performed between 2000 and 2019. Within 12 weeks, 43 hips (43 patients) underwent arthrocentesis. Patients were divided into 2 groups: evaluation ≤6 weeks or 6-12 weeks following THA. The 2011 Musculoskeletal Infection Society major criteria for PJI diagnosed PJI in 15 patients. Mann-Whitney U-tests were used to compare median laboratory values and receiver operating characteristic curve analysis was used to evaluate optimal cutoff values.

RESULTS

Both within 6 weeks and between 6 and 12 weeks postoperatively, median C-reactive protein (CRP), erythrocyte sedimentation rate, synovial white blood cell (WBC) count, neutrophil percentage, and absolute neutrophil count (ANC) values were significantly higher in infected THAs. Optimal cutoffs within 6 weeks were: CRP ≥100 mg/L, synovial WBCs ≥4390 cells/μL, neutrophil percentage ≥74%, and ANC ≥3249 cells/μL. Between 6 and 12 weeks, optimal cutoffs were: CRP ≥33 mg/L, synovial WBCs ≥26,995 cells/μL, neutrophil percentage ≥93%, and ANC ≥25,645 cells/μL.

CONCLUSION

Early PJI following THA should be suspected within 6 weeks with CRP ≥100 mg/L or synovial WBCs ≥4390 cells/μL. Between 6 and 12 weeks postoperatively, cutoffs of CRP ≥33 mg/L, synovial fluid WBC ≥26,995 cells/μL, and neutrophil percentage ≥93% diagnosed PJI with high accuracy.

LEVEL OF EVIDENCE

Level IV Diagnostic.

The combined measurement of synovial markers in the diagnosis of periprosthetic joint infection

INTRODUCTION

Currently there is no single test for periprosthetic joint infection (PJI) that demonstrates an acceptable level of sensitivity. The aim of this pilot study was to identify a combination of biomarkers that could exclude periprosthetic infection prior to revision surgery in hip and knee arthroplasty. This would help in equivocal cases of PJI, such as those with low-virulence organisms, chronic low-grade infection or 'aseptic' loosening. Current research has focused on measuring the levels of biomarkers in the patient's synovial fluid, and these can be combined to improve accuracy.

METHODS

We selected synovial white cell count (SF-WCC) and C-reactive protein (SF-CRP), as they demonstrated an acceptable level of sensitivity and specificity which could be measured using existing equipment. One hundred and sixty-one synovial fluid samples from 134 patients were collected and analysed prospectively using calculated cut-off values of 10mg/l for SF-CRP and 3,000×10⁶/l for SF-WCC. Samples were deemed positive for infection when either of the SF-CRP or SF-WCC values were above the cut-off.

RESULTS

The combined test demonstrated a sensitivity greater than 98.5% and specificity above 80% in all samples analysed or looked at separately for total hip replacement and total knee replacement infections. All ten aspirates taken from chronically infected joints tested positive.

CONCLUSIONS

The combination of SF-CRP and SF-WCC measurement has been shown to have high sensitivity of over 99% in detecting both acute and chronic PJI in both hip and knee arthroplasty. This ability of the test to exclude infection with a high degree of certainty will help in preoperative planning of PJIs.

Current Insights in the Evaluation and Treatment of Infected Total Knee Arthroplasty

Total knee arthroplasty is a widely successful procedure, but a small percentage of patients have a postoperative course complicated by periprosthetic joint infection (PJI). PJI is a difficult problem to diagnose and to treat, and the management of PJI differs, depending on the acuity of the infection. This paper discusses the established and newer technologies developed for the diagnosis of PJI as well as different treatment considerations and surgical solutions currently available.

Novel strategies to diagnose prosthetic or native bone and joint infections

INTRODUCTION

Bone and Joint Infections (BJI) are medically important, costly and occur in native and prosthetic joints. Arthroplasties will increase significantly in absolute numbers over time as well as the incidence of Prosthetic Joint Infections (PJI). Diagnosis of BJI and PJI is sub-optimal. The available diagnostic tests have variable effectiveness, are often below standard in sensitivity and/or specificity, and carry significant contamination risks during the collection of clinical samples. Improvement of diagnostics is urgently needed.

AREAS COVERED

We provide a narrative review on current and future diagnostic microbiology technologies. Pathogen identification, antibiotic resistance detection, and assessment of the epidemiology of infections via bacterial typing are considered useful for improved patient management. We confirm the continuing importance of culture methods and successful introduction of molecular, mass spectrometry-mediated and next-generation genome sequencing technologies. The diagnostic algorithms for BJI must be better defined, especially in the context of diversity of both disease phenotypes and clinical specimens rendered available.

EXPERT OPINION

Whether interventions in BJI or PJI are surgical or chemo-therapeutic (antibiotics and bacteriophages included), prior sensitive and specific pathogen detection remains a therapy-substantiating necessity. Innovative tests for earlier and more sensitive and specific detection of bacterial pathogens in BJI are urgently needed.

Combined serum and synovial C-reactive protein tests: a valuable adjunct to the diagnosis of chronic prosthetic joint infection

Background

Diagnosis of periprosthetic joint infection (PJI), especially chronic PJI, is very confusing and challenging. The value of C-reactive protein (CRP) in infectious diseases has been recognized, but the diagnostic value of CRP in chronic PJI is unknown. Our aim was to investigate the diagnostic value of synovial CRP in chronic PJI and to explore the role of combined serum and synovial CRP in distinguishing chronic PJI from aseptic failure after knee and hip arthroplasties.

Methods

We prospectively enrolled patients scheduled to have a revision surgery for chronic PJI or aseptic loosening from January 2019 to December 2020, in which synovial CRP was additionally measured along with routine preoperative diagnostic serum ((ESR, CRP) and synovial (PMN%) biomarkers. The receiver operating characteristic (ROC) curves and area under the curve (AUC) were analyzed for each biomarker to determine diagnostic efficacy.

Results

There were no statistically significant differences between the infection (n = 39) and aseptic (n = 58) groups, including 61 hips and 36 knees. The synovial CRP levels were significantly higher in the infection group than in the aseptic group (median: 9.93 mg/l vs 3.58 mg/l; p < .001). The optimal cut-off value for detecting chronic PJI of Synovial fluid (SF) CRP was of 7.26 mg/l with a sensitivity of 84.62%, a specificity of 93.10%. The combined model I (Serum CRP > 10.2 mg/l OR SF CRP > 7.26 mg/l) had a negative predictive value (NPV) of 96.67%, and a sensitivity of 97.44%. The combined model II (Serum CRP > 10.2 mg/l AND Synovial CRP > 7.26 mg/l) led to a specificity of 1, and a positive predictive value (PPV) of 1.

Conclusions

The present study demonstrated that the combination of serum and synovial CRP can be used as an adjunct to the diagnosis of chronic PJI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04545-6.