Outcomes of Long-Term Antibiotic Therapy for Prosthetic Joint Infection: A Cohort Study in a Canadian High-Volume Arthroplasty Center

Long-term antibiotic therapy (LAT) can be used to prevent relapse of prosthetic joint infection. Evidence on best practices for LAT is limited and conflicting. We aimed to assess total hip or knee arthroplasty revision for prosthetic joint infection for patients on LAT. We identified a single-institution study cohort of patients who used oral antibiotics for longer than 90 days. We then performed a chart review to identify demographic and clinical characteristics of these patients at the index revision and the day LAT ended. We used Cox proportional hazard models to estimate the hazard ratios (HRs) of the association between these characteristics and later revision. Our study cohort consisted of 85 patients (87 joints), 60% were male; median age was 65 years, and median body mass index was 32 kg/m2. One-third of infections were caused by staphylococci and one-third were culture-negative. Above-median (≥30 mg/L) preoperative C-reactive protein was associated with a higher risk of subsequent revision, HR = 4.5 (95% confidence interval 1.1-18.8). Staphylococcus aureus infection (compared to other staphylococcal infections) did not seem to be associated with an increased risk of revision, HR = 1.3 (95% confidence interval 0.3-6.4). LAT ended for 70% of patients; we identified no specific risk factors for post-LAT revision. Elevated C-reactive protein levels seem to be consistently associated with an increased risk of re-revision. We could not assess whether there is a threshold above which patients are at increased risk. Other factors, for example, increased age, may play a role, but we were unable to rule definitively on these factors.