Frailty Syndrome in Patients With Lower Extremity Amputation: Simplifying How we Calculate Frailty

Background: Frailty syndrome is an established predictor of adverse outcomes after surgical procedures. Our study aimed to compare the simplified National Surgical Quality Improvement Program 5-factor–modified frailty index (mFI-5) to its prior 11-factor–modified frailty index (mFI-11) with respect to the predictive ability for mortality, postoperative complications, and unplanned 30-d readmission in patients undergoing lower limb amputation. Methods: The National Surgical Quality Improvement Program (2005-2012) databank was queried for all geriatric patients (>65 y) who underwent above-knee and below-knee amputations. We calculated each mFI by dividing the number of factors present for a patient by the total number of available factors. To assess the correlation between the mFI-5 and mFI-11, we used Spearman's rho rank coefficient. We then compared the two indices for each outcome (30-d complication, 30-d mortality, and 30-d readmission) and C-Statistic using predictive models. Results: A total of 8681 patients were included with mean age of 76 ± 9 y, complication rate 35.8%, mortality rate 10.2%, and readmission rate 15.9%. There was no difference in type of amputation in frail and nonfrail. Correlation between the mFI-5 and mFI-11 was above 0.9 for all outcome measures. Both mFI-5 and mFI-11 indexes had strong predictive ability for mortality, postoperative complications, and 30-d readmissions. Conclusions: In patients undergoing major lower limb amputation, we found mFI-5 and the mFI-11 were equally effective in predicting postoperative outcomes. Frailty remained a strong predictor of postoperative complications, mortality, and 30-d readmission.