Mortality and Conversion Rates to Below-Knee or Above-Knee Amputation After Transmetatarsal Amputation

Introduction: The purpose of this study was to identify associated risk factors for complications, need for a higher level of amputation such as below-knee amputation (BKA) or above-knee amputation (AKA), and mortality after transmetatarsal amputation (TMA). Methods: We identified 265 patients who underwent 286 TMA procedures between June 2002 and July 2016. Medical records were reviewed for revision surgery and amputation. Mortality was verified using the National Death Index. We identified and documented potential risk factors including diabetes, hemoglobin A1c level, end-stage renal disease, cardiovascular disease, peripheral vascular disease, history of revascularization, contralateral amputation, and neuropathy. Sixty-eight percent were male, the mean age was 56.9 years (SD 12.8; range 24.1 to 92.1), and the median body mass index was 28.6 (interquartile range, 24.5 to 33.1). Results: Twenty-seven percent of the patients required a subsequent BKA or AKA after the index TMA surgery. The results of a multivariable model indicated that women (odds ratio [OR], 3.63; 95% confidence interval [CI], 1.716 to 7.672), patients aged 57 to 64 years (OR, 0.17; 95% CI, 0.06 to 0.51), and patients with a history of revascularization (OR, 7.06, 95% CI, 2.86 to 17.44) had markedly higher odds than the relevant comparison groups. Forty percent of the patients died after the index TMA at a median of 27 months. After adjusting for all patient factors, history of end-stage renal disease (OR, 2.2; 95% CI, 1.206 to 4.014) and cardiovascular disease (OR, 2.879; 95% CI, 1.615 to 5.131) remained markedly associated with mortality after TMA. Discussion: There are high rates of additional amputation after nontraumatic TMA and a high mortality rate. Surgeons should set realistic expectations with patients considered for TMA and identify risk factors, which may guide treatment. Treatment is multidisciplinary, requiring attention to surgical details, correction of vascular deficiency or contracture when present, and perioperative medical optimization.