Analysis of synovial biomarkers with a multiplex protein microarray in patients with PJI undergoing revision arthroplasty of the hip or knee joint.

INTRODUCTION: Diagnosing a (low-grade) periprosthetic joint infection (PJI) after hip or knee arthroplasty remains a diagnostic challenge. The aim of this study was to evaluate the utility of using a novel multiplex protein microarray system for synovial biomarkers in determining PJI in patients undergoing revision knee or hip arthroplasty. MATERIALS AND METHODS: The individual synovial fluid levels of 12 cytokines (IL-1b, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, IL-17, GM-CSF, TNF-α, and INF-γ) were analysed with a novel multiplex protein microarray system in 32 patients undergoing revision hip (n = 22) or knee (n = 10) arthroplasty. Cases were classified into septic and aseptic groups on basis of pre- and interoperative findings: [PJI (n = 14) vs. non-PJI (n = 18)]. Receiver operator characteristic (ROC) curves were calculated to assess the discriminatory strength of the individual parameters. A multiple regression model was used to determine the utility of using a combination of the tested cytokines to determine the infection status. RESULTS: The levels of all of the evaluated cytokines were significantly elevated in the PJI-group. Best sensitivity and specificity were found for IL-6, followed by IL-1b, IL-10, and IL-17. The multiple regression models revealed a combination of IL-2, IL-4, IL-5, IL6, lL-12, and GM-CSF to be associated with the best sensitivity (100%) and specificity (88.9%) for a cut-off value of 0.41, with a likelihood ratio of 9.0. CONCLUSION: Analysis of individual synovial fluid cytokine levels showed both high sensitivity and high specificity in diagnosing PJI. A combined model using several cytokines showed even higher sensitivity and specificity in diagnosing PJI and could thus be a useful predictive tool to determine the probability of PJI in patients with a painful prosthesis. LEVEL OF EVIDENCE: Diagnostic IV.

Mid-term results after revision total hip arthroplasty with custom-made acetabular implants in patients with Paprosky III acetabular bone loss.

INTRODUCTION: Severe acetabular bone loss, both with or without pelvic discontinuity, remains a challenge in revision total hip arthroplasty (RTHA). The goal of our study was to evaluate the mid-term results for consecutive patients with Paprosky III acetabular bone loss with or without pelvic discontinuity who needed RTHA with custom-made acetabular implants and to compare the results to those of other studies. MATERIALS AND METHODS: Sixty-eight (68) patients with severe acetabular bone loss (Paprosky Type IIIa and IIIb), who required RTHA, were included in our study. All prostheses were constructed on the basis of thin-layer computed tomography (CT) scans of the pelvis. The visual analogue scale (VAS), Harrison hip score (HHS), and clinical and radiographic follow-up assessments were used to evaluate the outcome. RESULTS: The average follow-up time was 43 months (range 1-120 months). Implant survival at last follow-up was 75% (51 of 68). Kaplan-Meier survival analysis, with explantation as the endpoint, revealed survival rates of 82.7% (3 years) and 77% (5 years). Patients with revision of the acetabular component only had a significant higher survival rate (p 0.012). Overall revision rate was 36.7%. Reinfection rate was 34.4%. Complications included 15 (22%) periprosthetic joint infections (PJI), 7 dislocations (10.2%), and 2 aseptic loosenings (2.9%). Mean VAS at last follow-up was 1.45 compared to 3.2 preoperatively, while mean HHS improved from 21.1 points preoperatively to 61 at last follow-up. The change in both scores was thus significant (p < 0.001). CONCLUSION: Defect reconstruction with custom-made modular acetabular implants can be a good, nevertheless expensive, treatment option with clinically and radiologically satisfying results in comparison to recent studies in the literature. Nevertheless, high postoperative complication rates, especially in terms of PJI, remain a challenge.