Outcomes after suppressive antimicrobial therapy for prosthetic joint infection: a prospective cohort study.

The objective of this study was to describe the use of and outcomes after suppressive antimicrobial therapy (SAT) in a large prospective peri-prosthetic joint infection (PJI) cohort. SAT was defined as antimicrobial therapy continuing beyond 12 months from PJI diagnosis or where there was an early intention for SAT. The primary outcome was "treatment failure" at 24 months, defined as any of (i) clinical evidence of (ii) further surgery for or (iii) death from PJI. Secondary outcomes included quality of life (QOL) scores using Short Form 12 (SF-12) and Oxford hip (OHS) and knee (OKS) scores. SAT was prescribed for 223 of 720 (31.0%) in the cohort. Patients prescribed SAT were more likely to be older, have comorbidities, chronic PJI, higher C-reactive protein, sinus tract, or be treated with debridement and implant retention. The most frequently prescribed antimicrobials for SAT were ciprofloxacin (64 [21%]), amoxicillin (42 [14%]), and rifampicin (35 [12%]). Treatment failure was more common in the SAT group (75/185 [40.1%] vs 85/447 [19.0%]). After propensity score-adjusted analysis, SAT remained associated with higher rates of treatment failure (aOR 2.48, 95% CI [1.66-3.72]). Although 24-month QOL scores were lower in the SAT group, there were similar improvements from baseline in functional joint scores in SAT and non-SAT groups (OHS median interquartile range [IQR] +8.5 [19.0] vs +7.0 [22.0]; P = 0.78 and OKS +8.0 [20.0] vs +7.0 [22.0]; P = 0.53). SAT use for PJI is common, and in this study, it was not associated with improved outcomes. Identifying patients most likely to benefit from SAT should be explored in carefully designed controlled trials.