148. Independent Predictors of Early Limb Loss in Patients Undergoing Free Tissue Transfer: A 12-year Experience

PURPOSE: Chronic lower extremity (LE) wounds pose threats to limb salvage. Free tissue transfer (FTT) can obviate the need for atraumatic major LE amputation (MLEA). However, the factors contributing to early postoperative amputation within the first 90 postoperative days remain underexplored in this population. This study aims to identify independent predictors of early limb loss after FTT. METHODS: A retrospective chart review of patients receiving LE FTT reconstruction July 2011 to March 2024 was conducted. Patient demographics, comorbidities, vascular characteristics, wound details, operative details, and postoperative outcomes were collected. Incidence of post-operative MLEA was recorded. Univariate logistic regression was conducted on all 94 collected variables for MLEA occurring with 60 days and 90 days of FTT. A Bonferroni correction was applied to account for multiple comparisons and reduce Type I errors, setting the significance threshold at p<0.0005. Variables meeting this criterion were included in a multivariate logistic regression to identify independent predictors of MLEA. RESULTS: During the study period, a total of 339 LE FTT were performed in 330 unique patients. A total of 41 patients (12.1%) underwent MLEA, all of which were below-knee amputation (BKA) at a median of 180 (IQR: 251.5) postoperative days. Significant co-variates were included in multivariate models for 60-day and 90-day limb loss. Independent predictors of BKA within 60 days of FTT included units of blood transfused by discharge (OR: 1.2, CI: 1.0-2.8, p=0.017), postoperative infection (OR: 6.4, CI: 1.4-28.4, p=0.014), and a history of a contralateral BKA (OR: 8.5, CI: 1.3-54.6, p=0.024). Independent predictors of BKA within 90 postoperative days were units of intraoperative blood transfusion (OR: 2.2, CI: 1.1-4.2, p=0.026), a flap complication (OR: 10.4, CI: 1.4-78.7, p=0.023), postoperative infection (OR: 5.4, CI: 1.0-28.1, p=0.045), and a history of a contralateral BKA (OR: 19.0, CI: 2.1-153.0, p=0.008). CONCLUSION: We have identified several predictors of early limb loss in the LE FTT population, including postoperative infection, flap complications, need for blood transfusion, and a history of MLEA on the contralateral limb. These factors should be used to risk stratify patients undergoing LE FTT to optimize postoperative surveillance protocols.