DOES CHLORHEXIDINE CONCENTRATION MATTER? A COMPARATIVE STUDY OF 0.5% VERSUS 2% SKIN PREPARATION IN FOOT AND ANKLE SURGERY

Evidence comparing different concentrations of chlorhexidine (CHG) for surgical skin preparation in foot and ankle surgery remains limited. This study evaluates surgical site infection (SSI) rates following use of 2% and 0.5% CHG and compares deep and superficial infection rates against national benchmark data. The UK Foot and Ankle Thromboembolism Audit reported superficial and deep infection rates of 3.73% and 1.27%. A retrospective cohort study of consecutive cases, excluding diabetic foot infections, was undertaken between March 2025 and February 2026. SSI was defined as postsurgical infection requiring antibiotics (superficial) or return to theatre for washout (deep). A total of 226 cases were included (47 trauma, 179 elective). Mean age was 54.9 years (range 20 to 84) and 150 patients (66.4%) were female. Skin preparation changed from 2% to 0.5% CHG in September 2025, with 110 cases receiving 2% CHG and 116 receiving 0.5% CHG. Seventeen SSIs were identified (7.52%, 95% confidence interval 4.68 to 11.79) including sixteen superficial (7.08%, 95% confidence interval 4.33 to 11.26) and one deep (0.44%, 95% confidence interval 0.01 to 2.72). Overall SSI rate was 6.36% with 2% CHG and 8.62% with 0.5% CHG: difference 2.26% (p = 0.52). Trauma and elective SSI rates were comparable (6.38% vs 7.82%, p = 1.00). Compared with national audit data, deep SSI rate was lower (0.44% vs 1.27%, p = 0.42), while superficial SSI rate was higher (7.08% vs 3.73%, p = 0.02). No significant difference in SSI rates was identified between 2% and 0.5% CHG. The elevated superficial SSI rate compared with national data warrants further scrutiny, and prospective SSI surveillance has been implemented to complete the audit cycle and ensure sustained safety and benchmarking.