CRP KINETICS FOLLOWING DAIR: NOT EVERY CRP SPIKE IS ASSOCIATED WITH DAIR FAILURE

Introduction & Aim Debridement, antibiotics, and implant retention (DAIR) is the surgical treatment of periprosthetic joint infection (PJI) associated with the best functional outcome. DAIR is primarily indicated when biofilm is still immature. While C-reactive protein (CRP) has limited diagnostic value in low-grade PJI, it is a key biomarker for monitoring postoperative recovery. However, CRP kinetics and correlation with treatment success remain understudied. This analyses CRP kinetics following DAIR and identifies factors causing CRP spikes unrelated to treatment failure. Methods We retrospectively analysed postoperative CRP trends in patients undergoing DAIR of hip and knee PJI between 2010 and 2024. Only successful DAIR procedures were included. PJI diagnosis was based on the EBJIS definition. Serial CRP values were recorded from the immediate postoperative period through follow-up. Particular attention was given to secondary CRP spikes following initial decline, correlated with specific postoperative events rather than true infection relapse. Treatment success was defined as no clinical or microbiological infection at minimum 2 year follow-up. Results 124 patients after successful DAIR of hip or knee arthroplasty were analysed. The CRP pattern showed a rapid postoperative rise peaking within the first 2–3 days, followed by gradual decline over 2-3 weeks. 62 patients showed a consistent CRP decline; the remaining 62 exhibited a secondary CRP spike following initial decline. Among the latter: 53% were female, 30 hip and 32 knee arthroplasties, mean age 71 years, mean symptom duration before DAIR 8 days. The mean CRP difference between secondary and primary CRP spike was 112,6 mg/L, mean spike duration was 6 days. Secondary CRP spikes were related to: surgical interventions (n=27; drainage and urinary catheter removal, wound management e.g. dressing change, surgical clips removal), antibiotic regimen adjustments (n=11), coinfection (n=9; urinary tract infections, gastrointestinal disturbances, pneumonia), other reasons (n=6; attack of gout (1), change of immunosuppressive therapy (1), discharge from intensive care unit (2), oedema (2)), and no identifiable cause (n=9). Conclusions This is the first study evaluating CRP kinetics following DAIR. Our study found that most of CRP spikes following DAIR procedure are not related to treatment failure. A secondary CRP spike was observed in 50% of successful DAIR procedures and was most commonly related to postoperative interventions - including drainage removal, adjustment of antibiotic therapy and wound management – rather than infection relapse. Surgeons should consider procedural and therapeutic factors when interpreting postoperative CRP trends and avoid premature intervention based on biomarker fluctuations alone.