UCSF

Background: The European Bone and Joint Infection Society (EBJIS)/Musculoskeletal Infection Society (MSIS) criteria provide a framework for diagnosing hip periprosthetic joint infection, yet daily clinical application lacks a standardized algorithm. Since these criteria rely heavily on synovial fluid markers, surgeons encounter 2 primary dilemmas: the reliability of aspiration techniques (ultrasound vs fluoroscopy) and the economic trade-off between higher-cost proprietary assays and standard institutional laboratories. This cost-effectiveness analysis was conducted to identify the diagnostic pathway that maximizes clinical benefit while minimizing expenditure within the EBJIS/MSIS framework. Methods: A decision tree model simulated the diagnostic workup of a 67-year-old patient with suspected hip periprosthetic joint infection. Ten strategies were evaluated, comparing aspiration modality and laboratory method (institutional, point-of-care, and third-party analysis). The model incorporated 1- and 2-stage revision pathways and included dry tap scenarios. Accuracy inputs were derived from the literature, and costs reflected 2025 Medicare schedules. Sensitivity analyses tested robustness across diagnostic outcomes. Effectiveness was measured in quality-adjusted life years based on downstream surgical outcomes. Results: Ultrasound-guided aspiration with third-party synovial analysis was most cost-effective in both revision scenarios. Despite higher upfront costs of specialized testing, its superior sensitivity and specificity maximized quality-adjusted life years by reducing morbidity from misdiagnosis. Institutional testing was preferred only if sensitivity exceeded 90% and specificity 94%. In "dry tap" cases, intraoperative lateral flow alpha-defensin testing was favored over preoperative nuclear imaging. Surgical outcome utility most strongly influenced the results. Conclusions: Within the EBJIS/MSIS framework, prioritizing high-accuracy diagnostic tools maximizes value by reducing misaligned revision strategies. Diagnostic precision outweighed individual test cost in determining cost-effectiveness. Level of Evidence: Economic and decision analysis, Level II.