Accuracy of Preoperative Hip Aspiration in Diagnosing Infection before Conversion to Total Hip Arthroplasty after Failed Fixation for Hip Fracture: A Retrospective Study.

Abstract

Objectives: 1.What is the accuracy of preoperative hip aspiration in diagnosing infections in patients scheduled for conversion of failed hip fixation to total hip arthroplasty (cTHA)? 2. What is the clinically significant cutoff value for inflammatory markers that may assist in diagnosing hip infections before cTHA? 3. What is the concordance between preoperative hip aspiration and intraoperative cultures?

Methods: A retrospective study was conducted at Imam Khomeini Hospital Complex, Tehran (2017-2021), including candidates for cTHA following failed open reduction and internal fixation (ORIF). Exclusions were dry tap (failed aspiration), recent antibiotic therapy, or insufficient synovial fluid. Patients underwent erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) testing, joint aspiration, and intraoperative cultures, with the latter serving as the gold standard for diagnosis.

Results: The study involved 38 patients (mean age 50 ± 16.4 years). Preoperative hip aspiration demonstrated low sensitivity (17.7%) but high specificity (81.0%). C-reactive protein (CRP) demonstrated moderate diagnostic value (AUC = 0.643) with an optimal cutoff of 8.8 mg/L (sensitivity, 64.3%; specificity, 64.7%). Erythrocyte sedimentation rate (ESR) had limited diagnostic value (AUC = 0.577).

Conclusion: Preoperative hip aspiration for diagnosing infection in patients with total hip arthroplasties (THA) demonstrated poor sensitivity but high specificity. C-reactive protein (CRP) demonstrated moderate potential, whereas erythrocyte sedimentation rate (ESR) had limited value. These findings underscore the need for improved diagnostic methods, potentially combining multiple tests. Future research should focus on developing more accurate diagnostic approaches for infections in patients with chronic total hip arthroplasty (cTHA).