Susceptibility-guided use of gentamicin-loaded calcium sulfate after surgical debridement for complex diabetes-related foot infection: a single-centre case series

Background Complex diabetes-related foot infections (DFIs) frequently involve tissue necrosis, impaired perfusion, bacterial persistence, and residual dead space, which may complicate infection control despite surgical and systemic antimicrobial treatment. Bioabsorbable calcium sulfate provides a potential means of delivering high local antibiotic concentrations after surgical source control. This study describes the clinical, microbiological, wound, and safety outcomes of susceptibility-guided gentamicin-loaded calcium sulfate used as an adjunct to surgical debridement and systemic antimicrobial therapy. Methods We retrospectively reviewed 10 consecutive adults with complex DFI treated at a tertiary referral centre between 2024 and 2026. All patients underwent surgical debridement and deep-tissue culture sampling and received systemic antimicrobial therapy. Gentamicin-loaded calcium sulfate was used only when baseline pathogenic isolates demonstrated gentamicin susceptibility. Each application consisted of 5 cc of calcium sulfate mixed with 80 mg gentamicin. Index-wound area, microbiological findings, revascularization, repeat treatment, amputation, laboratory parameters, and safety outcomes were evaluated descriptively. Results The mean age was 64.9 years, 90% of patients were male, and peripheral arterial disease was present in 80%. Osteomyelitis was documented in 20%, and 30% underwent lower-extremity revascularization. The median wound-measurement follow-up was 42 days (range, 29–120). Mean index-wound area reduction was 62.9%, and the median reduction was 62.0% (range, 0.6%–100%). Among the nine patients who did not undergo major amputation, all demonstrated reduction in index-wound area; one achieved complete closure during the measurement period and another subsequently underwent definitive closure with a skin graft. One patient required major amputation. Follow-up cultures showed no persistence of baseline pathogens among patients with microbiological reassessment. Median CRP decreased from 66.5 to 9.1 mg/L. No patient developed hypercalcaemia, and no clear cohort-level deterioration in renal function was observed. Conclusion In this small uncontrolled case series, susceptibility-guided gentamicin-loaded calcium sulfate was feasible as an adjunct to surgical debridement and systemic antimicrobial therapy in selected patients with complex DFI, with reductions in wound area and absence of baseline-pathogen persistence on available follow-up cultures. However, one patient required major amputation, and the retrospective design, small sample size, multimodal treatment, and absence of a comparator preclude conclusions regarding efficacy. Prospective comparative studies are needed to define the role of this approach in multidisciplinary DFI management.