38. Final Debridement Cultures Before Free Tissue Transfer Do Not Predict Limb Salvage Outcomes

PURPOSE: Chronic wounds are serially debrided prior to lower extremity (LE) free tissue transfer (FTT). Qualitative cultures taken after these debridements may guide clinical decisions. This study evaluates the impact of qualitative final debridement culture results LE FTT outcomes. METHODS: A retrospective chart review of patients receiving LE FTT from July 2011 to June 2024 was conducted. RESULTS: 345 LE FTT had final debridement culture data. The median Charlson Comorbidity Index was 4 (IQR: 3), reflecting prevalent rates of diabetes (55.9%), peripheral vascular disease (54.2%), chronic kidney disease (11.1%), and end-stage renal disease (5.5%). Final debridement cultures were positive in 143 cases (41.4%). 43 wounds (12.5%) were polymicrobial. Flap survival rate was 96.8% and, by a median follow up time of 10.6 (IQR: 22.7), major limb amputation occurred in 40 cases (11.6%). Culture characteristics that conferred higher risk for amputation on univariate analysis included a bacterial load of “rare” (OR: 8.1, p=0.013) and methicillin-resistant Staphylococcus aureus (MRSA; OR: 3.7, p=0.039). Upon multivariate analysis adjusting for all significant co-variates to amputation, these variables did not remain significant. Rather, osteomyelitis on the date of surgery (OR: 3.1, CI: 1.2, 8.0, p=0.018), more debridements before FTT (OR: 1.4, CI: 1.0, 1.8, p=0.037), and an occluded posterior tibial artery (OR: 52.5, CI: 1.0-6.1, p=0.042) independently increased odds of amputation. CONCLUSION: The limited predictive value found of the final debridement culture reinforces the capacity of healthy vascularized tissue to promote limb salvage, even in the presence of soft tissue infection.