5-Item Modified Frailty Index Predicts Outcomes After Below-Knee Amputation in the Vascular Quality Initiative Amputation Registry

Patient frailty indices are increasingly being utilized to anticipate post-operative complications. This study explores whether a 5-factor modified frailty index (mFI-5) is associated with outcomes following below-knee amputation (BKA). All BKAs in the vascular quality initiative (VQI) amputation registry from 2012-2017 were reviewed. Preoperative frailty status was determined with the mFI-5 which assigns one point each for history of diabetes, chronic obstructive pulmonary disease or active pneumonia, congestive heart failure, hypertension, and nonindependent functional status. Outcomes included 30-day mortality, unplanned return to odds ratio (OR), post-op myocardial infarction (MI), post-op SSI, all-cause complication, revision to higher level amputation, disposition status, and prosthetic use. 2040 BKAs were performed. Logistic regression showed an increasing mFI-5 score that was associated with higher risk of combined complications (OR 1.22, confidence interval [CI] 1.07-1.38, P < .05), 30-day mortality (OR 1.60, CI 1.19-2.16, P < .05), post-op MI (OR 1.79, CI 1.30-2.45, P < .05), and failure of long-term prosthetic use (OR 1.17, CI 1.03-1.32, P < .05). In the VQI, every one-point increase in mFI-5 is associated with an increased risk of 22% for combined complications, 60% for 30-day mortality, nearly 80% for post-op MI, and 17% for failure of prosthetic use in BKA patients. The mFI-5 frailty index should be incorporated into preoperative planning and risk stratification.