Prevalence of low-grade infection in uncomplicated fracture osteosynthesis

Abstract

Subclinical bacterial colonization of osteosynthesis implants has been suggested as a potential contributor to subsequent periprosthetic joint infection, yet its frequency in clinically uneventful fracture healing remains unclear. This prospective cohort study aimed to determine the prevalence of unexpected positive intraoperative cultures (UPIC) during elective hardware removal after uncomplicated fracture union. Adult patients undergoing elective implant removal after radiographic union were prospectively enrolled. Inclusion required absence of signs of clinical infection and no antibiotic therapy within 48 hours before surgery. Three deep tissue samples were collected from the implant-bone interface prior to irrigation. Samples were homogenized and inoculated into aerobic and anaerobic blood culture bottles. UPIC were defined as culture growth without clinical suspicion. Microbiological confirmation required at least two concordant isolates according to the FRI consensus definition. Sixty-nine patients were included. Any bacterial growth occurred in 32 patients (46.4%). Seventeen patients (24.6%) had two or more concordant isolates fulfilling microbiological criteria, whereas 15 (21.7%) had a single low-virulence isolate interpreted as contamination. UPIC were most frequent in the shoulder, predominantly Cutibacterium acnes, followed by the elbow with mainly coagulase-negative staphylococci. No postoperative infections, wound complications, or reoperations occurred. Nearly one quarter of clinically unremarkable hardware removals yielded multiple concordant isolates, indicating a substantial rate of low-grade infection. Although no short-term clinical consequences were observed, the potential relevance of UPIC for future arthroplasty remains uncertain.