Midfoot amputations expand limb salvage rates for diabetic foot infections

The persistent high incidence of limb loss resulting from advanced forefoot tissue loss and infection in diabetic patients prompted an evaluation of transmetatarsal (TMA) and transtarsal/midfoot amputations in achieving foot salvage at our tertiary vascular practice. Over the last 8 years, 74 diabetic patients required 77 TMAs for tissue loss and/or infection. Twelve (16%) of the patients had a contralateral below-knee amputation (BKA) and 26% (n=20) had dialysis-dependent renal failure. Thirty-five (45%) limbs had concomitant revascularization (bypass grafting or percutaneous transluminal angioplasty), 32 (42%) had arterial occlusive disease by noninvasive testing and/or arteriography but were not or could not be revascularized, and seven (13%) had normal hemodynamics. Patient factors, arterial testing, operative complications, operative mortality (< 60 days), wound healing (at 90 days), limb salvage, functional status, and survival were evaluated during a mean follow-up of 20 months (range 3-48). Operative mortality was 5% (n=4) after TMA and/or midfoot amputation. Although 32 TMAs initially healed (44%), six BKAs were required 5-38 months later. Of the 41 nonhealing TMAs (56%), progressive infection/tissue loss necessitated major amputation of nine limbs. Chopart (n=22) or Lisfranc (n=10) midfoot amputations were done in the remaining 32 nonhealing TMAs. Despite additional wound revisions in 14 patients (44%), major amputation was needed in six limbs. However, functional ambulation was achieved in 23 of 25 (92%) limbs with healed midfoot amputations, and foot salvage was possible in 61% (25/41) of nonhealing TMAs. Overall limb salvage for TMA/midfoot procedures was estimated from Kaplain-Meier life tables to be 73%, 68%, and 62% at 1, 3, and 5 years, respectively, with only 50% of dialysis patients avoiding major amputation. Ankle pressure > 100 mm Hg and a biphasic pedal waveform had a positive predictive value (PPV) of 79%, and toe pressure > 50 mm Hg had a PPV of 91% for determining healing of TMA/midfoot amputations. One- and 3-year survival rates were only 72% and 69% for the entire cohort from life table estimates. Aggressive attempts at foot salvage are justified in diabetic patients with advanced forefoot tissue loss/infection after assuring adequate arterial perfusion. Transtarsal amputations salvaged over half of nonhealing TMAs with excellent functional results.