Predictors of Ambulatory Status at 1 Year Following Major Lower Extremity Amputation

Abstract

Nearly 60,000 major lower extremity amputations (AKA/BKA) are performed annually in the United States. We created a simple risk score for predicting ambulation at 1 year following AKA/BKA. We queried the Vascular Quality Initiative amputation database for patients who underwent above-knee (AKA) or below-knee (BKA) amputation (2013-2018). The primary endpoint was ambulation at 1 year either independently or with assistance. The cohort was divided into 80% derivation and 20% validation. Using the derivation set, a multivariable model identified preoperatively available independent predictors of 1 year ambulation and an integer-based risk-score was created. Scores were calculated to assign patients to risk groups-low, medium, or high chance of being ambulatory at 1 year. Internal validation was performed by applying the risk score to the validation set. Of 8725 AKA/BKA, 2055 met inclusion criteria-excluded: 2644 nonambulatory prior to amputation, 3753 missing 1-year follow-up ambulatory status. The majority-n = 1366, 66% were BKAs. The indications were CLTI; 47%, ischemic tissue loss; 9%, ischemic rest pain; 35%, infection/neuropathic; 9%, acute limb ischemia. Ambulation at 1 year was higher for BKA than AKA: 67%, versus 50%, p < .0001. In the final prediction model, contralateral BKA/AKA was the strongest predictor of nonambulation. The score provided reasonable discrimination (C-statistic = 0.65) and was well calibrated (Hosmer-Lemeshow p = .24). Sixty-two percent of patients who were ambulatory preoperatively remained ambulatory at 1 year. An integer-based risk score can stratify patients according to chance of ambulation at 1 year after major amputation and may be useful for preoperative patient counseling and selection.

Keywords: ambulation; amputation; clinical calculator; peripheral arterial disease; risk prediction; vascular quality initiative.