“Successful Outcome” after Below-Knee Amputation: An Objective Definition and Influence of Clinical Variables

Functional success after below-knee amputation (BKA) has been poorly studied. The purpose of this study was to establish a consistent definition of “successful outcome” after BKA and to identify clinical variables influencing that definition. Three hundred nine consecutive patients undergoing BKA were evaluated postoperatively using the following definition for “successful outcome”: 1) wound healing of the BKA without need for revision to a higher level; 2) maintenance of ambulation with a prosthesis for at least 1 year or until death; and 3) survival for at least 6 months. Independent clinical predictors influencing outcome were determined using bivariate and multivariable logistic regression analyses. For the cohort, median survival and maintenance of ambulation were 44 months and 60 months, respectively. Although 86.4 per cent of patients healed without the need for revision to a higher level, 63.4 per cent maintained ambulation with a prosthesis for 1 year and 86.1 per cent survived for 6 months, successful outcome as defined by attaining all three components of the definitions occurred in only 51.1 per cent (n = 158) of patients. Of 19 clinical variables examined, six were identified in bivariate analysis as significantly associated with outcome. However, only three were found to be independent predictors of outcome using logistic regression modeling. The presence of coronary artery disease [odds ratio (OR), 0.465; 95% CI, 0.289–0.747], cerebrovascular disease (OR, 0.389; 95% CI, 0.154–0.980), and impaired ambulatory ability before BKA (OR, 0.310; 95% CI, 0.154–0.623) were each associated with a decreased odds for successful outcome. Patients who presented with impaired ambulatory ability in combination with another independent predictor had only a 20 per cent to 23 per cent probability of successful outcome and patients who presented with all three had a 10.4 per cent probability of success. In contrast, patients who had none of the independent predictors at presentation had a 67.5 per cent probability of successful outcome after BKA. A standardized definition of success after BKA capable of predicting outcomes is feasible and can be a useful tool to determine rehabilitation potential. When judged by our definition, patients without predictors of failure possess a high potential for rehabilitation, whereas patients with multiple predictors rarely rehabilitate, should probably receive palliative above-knee amputation, and forgo the expense of futile prosthetic training.