Culture-Specific Outcomes of Intra-Articular Antibiotic Infusion With Implant-Retaining Debridement for Periprosthetic Joint Infection After Unicompartmental Knee Arthroplasty.

Background: Periprosthetic joint infection (PJI) following unicompartmental knee arthroplasty (UKA) poses a substantial therapeutic challenge, particularly in culture-negative cases. The efficacy of debridement, antibiotics, and implant retention (DAIR) for PJI after UKA remains inadequately defined. This study evaluated DAIR supplemented by postoperative catheter-based intra-articular antibiotic infusion and compared outcomes between culture-positive and culture-negative patients. Methods: In this single-center retrospective cohort study, 21 patients with PJI after UKA who met the 2018 International Consensus Meeting criteria were treated with DAIR, including radical debridement, povidone-iodine lavage, and postoperative catheter-based intra-articular antibiotic infusion. The primary outcome was eradication success at 2 years. Secondary outcomes included reoperation, functional recovery, inflammatory-marker normalization, and antibiotic-related complications. Results: At a mean follow-up of 25 months, the overall infection eradication rate was 85.7%, with no significant difference between culture-positive (83.3%) and culture-negative (88.9%) groups. Functional scores improved substantially and comparably between groups. However, culture-negative patients experienced significantly longer hospital stays (18.2 vs 13.7 days, Conclusions: In this exploratory single-center cohort, DAIR supplemented by catheter-based intra-articular antibiotic infusion demonstrated encouraging mid-term infection control in carefully selected patients with UKA-PJI. Comparable infection-control and functional outcomes were observed between culture-positive and culture-negative cases; however, the limited sample size precludes definitive conclusions regarding equivalence between groups. Level of Evidence: Therapeutic Level III.