Risk factors for mortality after below knee amputation in patients with diabetes

Although many diabetic foot ulcers can be managed with limb-salvage strategies, a subset of patients ultimately progress to major lower-extremity amputation, including below-knee amputation (BKA), particularly when limb salvage is no longer feasible. While BKA is performed as a source-control procedure aimed at limiting proximal spread of infection, postoperative mortality following BKA remains high.

The purpose of this study was to evaluate patients with diabetes undergoing primary below-knee amputation (BKA) and to identify preoperative demographic, clinical, and laboratory factors associated with short- and intermediate-term all-cause mortality following the procedure.

Retrospective cohort study evaluating mortality outcomes after primary below-knee amputation in patients with diabetes.

A retrospective cohort study was conducted including patients who underwent primary below-knee amputation for diabetes-related complications. Mortality was evaluated at predefined postoperative time points (30, 90, 180, 365 days and overall mortality). Multivariate logistic regression was performed to identify independent predictors of mortality.

A total of 1,487 patients were analyzed (68.8% male; mean age 67.9 ± 12.4 years). Overall, 1,096 patients died during follow-up. Non-survivors were older at all time points and had higher Charlson Comorbidity Index scores and lower serum albumin levels compared to survivors. Multivariate analysis for overall mortality identified five independent predictors of increased mortality: CKD (OR 2.20, 95% CI 1.289-3.760, p = 0.004), albumin <2.95 g/dL (OR 2.85, 95% CI 1.843-4.409, p < 0.001), WBC >13.805 × 10⁹/L (OR 1.63, 95% CI 1.059-2.500, p = 0.026), Charlson Comorbidity Index >5.5 (OR 2.61, 95% CI 1.672-4.067, p < 0.001), and postoperative oral rather than IV antibiotic therapy (OR 1.95, 95% CI 1.102-3.456, p = 0.022).

This study demonstrates that preoperative comorbidities and laboratory markers-including CKD, hypoalbuminemia, elevated WBC count, and higher comorbidity burden-are strongly associated with increased mortality after BKA in diabetic patients. These findings underscore the importance of comprehensive preoperative assessment and targeted perioperative strategies to improve outcomes in this high-risk population.