322. Joint Spacer Retention, Antimicrobial Suppression, and Risk of Re-infection

Abstract

BackgroundTwo-stage exchange is the standard treatment of periprosthetic joint infection in the United States. Occasionally, for selected patients, temporary antibiotic-loaded spacers are retained “permanently” instead of proceeding with prosthesis re-implantation. It is unclear whether the “retained” spacer represents a nidus for re-infection, and would require secondary antibiotic suppression to prevent recurrence of infection. We aim to determine the risk of re-infection among patients with retained knee and hip spacers, and assess the role of antibiotic suppression.MethodsWe identified 51 patients with retained static or articulating knee (n = 34) and hip (n = 17) spacers between 1996 and 2014 using the Mayo Clinic Hospital Orthopedic database. Medical records were reviewed to collect clinical data, including antibiotic use and offending organisms. We compared the cumulative incidence of reinfection between those with or without suppression using a competing risk model, with death and revision for mechanical failure as competing risks.ResultsThe median age was 77 years (range, 48–94). Gender distribution was equal. The median Charlton Comorbidity Index (CCI) was 3 (1–11), while median BMI was 30.1 (17.8–59.5). Eleven of 51 patients received antibiotic suppression after spacer retention. A history of prior antibiotic suppressive therapy was the only variable associated with being placed back on antibiotic suppression after spacer retention [OR 18 (95% CI 3.2–100)]. During the median follow-up period of 31.3 months, there were five re-infections. The cumulative incidence of re-infection was not significantly different between suppressed and unsuppressed groups (P = 0.89). The re-infecting pathogens were different from the index offending organisms. Only the presence of preoperative draining sinus was significantly associated with re-infection [OR 10 (95% CI 1–99.6)].ConclusionIn selected patients where a second-stage prosthesis re-implantation is not an option, and retention of “temporary” antibiotic loaded spacer is surgically preferred, the risk of re-infection was not prevented by prolonged antibiotic suppression. The presence of a draining sinus was significantly associated with re-infection, often with new pathogens.Disclosures All authors: No reported disclosures.