Risk Factors for Lower Extremity Minor Amputation Conversion to Major Amputation

Abstract

Minor lower extremity amputations have become an important part of the limb salvage approach but are not as benign as previously thought. This study investigates the difference in outcome between toe/ray versus midfoot amputations and the risk factors for major amputation conversion associated with each procedure. We performed retrospective chart review of foot amputation patients at a single tertiary care medical center with a primary end point of conversion to major amputation and secondary end points of one-year wound healing and mortality rate. We collected data on relevant medical comorbidities, non-invasive vascular imaging, revascularization, repeat amputations, wound healing rate, and one-year mortality. Patients were separated into toe/ray amputations versus midfoot amputation groups and compared using descriptive statistics, Chi Squared tests, Cox proportional hazards, and a multivariate logistic regression model. A total of 375 amputations were included in the analysis. 65.3% (245 patients) included toe/ray amputations and 34.7% (130 patients) included midfoot amputations. We compared these two cohorts with regard to their rate of conversion to repeat minor and/or major amputation in addition to overall mortality. The toe/ray group underwent more repeat minor amputations within one year after index amputation (34.7% vs. 21.5%, p=0.008) and wound healing (epithelization) at 90 days was also higher in this group. The midfoot group had a higher conversion to major lower extremity amputation within one year on univariate analysis (20.8 vs. 6.9%, p<0.001). Overall one-year mortality was 6.17% and there was no significant difference between groups. While there is a consistency with previous studies that found no significant overall difference in mortality between types of minor LEA, we have extended this previous work by demonstrating the independent risk factors for conversion to major amputation between types of minor LEA. Comparing these two groups will assist surgeons in choosing the appropriate level of amputations and will enhance patient's understanding of their chance of wound healing and risk of repeat amputation.