Distal Femur Versus Proximal Tibia Fracture-Related Infections: A Prospective Site-Stratified Audit of Epidemiology, Microbiology, and Surgical Strategy

Background Periarticular fracture-related infections (PA-FRIs) around the knee represent a uniquely challenging subset of fracture-related infections, occurring in anatomically complex regions where mechanical stability, soft-tissue viability, and joint preservation are simultaneously threatened. Despite their clinical significance, most published literature amalgamates periarticular FRIs into larger datasets, overlooking potentially important site-specific differences between the distal femur (DF) and proximal tibia (PT). This study aimed to compare the epidemiology, microbiological profile, and initial surgical strategy between DF and PT fracture-related infections using a prospectively maintained registry. Methods A prospective registry audit was conducted at a tertiary trauma and reconstruction centre over twelve months (June 2024–May 2025), capturing 120 consecutive PA-FRI cases. Diagnosis was established according to Fracture-Related Infection Consensus Group criteria. Variables collected included demographics, comorbidities, infection chronicity, sinus tract presence, microbiological yield, and initial surgical strategy. A minimum of five deep tissue samples were obtained intraoperatively, with cultures incubated for up to 14 days. Descriptive statistics were used to compare outcomes between anatomical sites. Results The cohort comprised 120 patients with a male-to-female ratio of 13:2, predominantly in the 41–60 year age group. Diabetes mellitus was present in 28.3%. Chronic infections (>4 weeks duration) accounted for 63.3% of cases, and 55.8% presented with an established sinus tract at admission. Culture positivity was 64.1%, with no-growth cultures in 35.8% of cases. The dominant organisms were Staphylococcus aureus (MRSA and MSSA) and Gram-negative bacilli including Enterobacter cloacae and Klebsiella pneumoniae — present at comparable frequencies at both sites. Surgically, PT infections underwent implant removal nearly three times more frequently than DF cases (44 vs 15), while debridement, antibiotics, and implant retention (DAIR) was performed equally across both sites (17 vs 17). External fixation was used more frequently in PT cases (10 vs 4). Conclusions While DF and PT fracture-related infections share similar host demographics and injury profiles, their surgical management patterns diverge significantly, driven by the proximal tibia's thin soft-tissue envelope and subcutaneous implant position. The prominent Gram-negative burden at both sites challenges the traditional Gram-positive-centric view of fracture-related infection and supports broader empiric antibiotic coverage pending culture results. The high rate of culture-negative results underscores the need for improved diagnostic protocols including extended incubation and molecular diagnostics. Site-specific treatment algorithms are warranted to standardise periarticular fracture-related infection management