Etiology of Limb Loss after Successful Transmetatarsal Amputation

Transmetatarsal amputation (TMA) is a functional foot reconstruction for limb salvage following extensive forefoot infection and/or ischemic gangrene. Unfortunately, up to 30% of TMAs progress to major amputation. This study evaluates the effects of diabetes and peripheral artery disease (PAD) on long-term TMA outcomes.

This was a retrospective review of a single-surgeon, single-institution consecutive series of TMAs performed between 2006 and 2024. Patients with PAD and perioperative hemoglobin A1c (HbA1c) ≤ 6.5 (euglycemic PAD), PAD and HbA1c > 6.5 (hyperglycemic PAD), and diabetes without PAD (diabetes [DM] only) were compared for ipsilateral major amputation, primary healing, and all-cause mortality.

Among 230 TMAs, 189 healed primarily. Of intact TMAs, 48 were euglycemic PAD, 71 hyperglycemic PAD, and 70 DM only. There were no differences in sex, race, or comorbidities aside from smoking history (P = 0.043) and history of prior revascularization (P < 0.001). Mean HbA1cs were 5.7, 8.3, and 9.1 (P < 0.001). The PAD groups were older (67.1, 66.7, 57.3 years; P < 0.001), had lower toe pressures (34.7, 43.0, 99.0 mm Hg; P < 0.001), and higher WIfI scores (69.1%, 76.0%, 43.6% stage 4; P = 0.009). Primary healing rates were 85.7%, 74.0%, and 89.7% (P = 0.021), with similar 90-day all-cause mortality (P = 0.364). Kaplan-Meier analysis demonstrated superior intact TMA survival in euglycemic PAD (P = 0.049), with 5-year TMA survival rates of 97.8%, 83.6%, and 78.8%. Modeled continuously, each 1% rise in HbA1c increased major amputation odds by 24% (P = 0.005).

Uncontrolled diabetes is a distinct marker of poor long-term outcomes following TMA for limb salvage.