Abstract
OBJECTIVES: The growing prevalence of diabetes and concomitant peripheral arterial disease (DM/PAD) has led to an increase in patients at risk for adverse limb events in current practice. Despite a widespread perception that minor amputation may result in both limb salvage and preserved functionality, the natural history of minor amputations remains unknown. Thus, we sought to quantify the rates of subsequent major amputation and survival among DM/PAD patients with any prior minor amputation. METHODS: We performed a retrospective cohort study using US Medicare claims from 2007 to 2019. We included patients with DM/PAD based on International Classification of Diseases, 9th and 10th editions, diagnosis codes. We excluded patients lacking continuous fee-for-service coverage or with incomplete demographic data. The primary exposure was prior minor (below-ankle) amputation. The primary outcome was major (above-ankle) amputation. Statistical analyses were performed using the Kaplan-Meier method and Cox proportional hazards modeling. RESULTS: We identified 12,257,174 patients (age 73 ± 11 years; 48% male; 76% White) with DM/PAD. Of these patients, 2.2% (n = 274,225) underwent prior minor amputation. Patients with prior minor amputation were more likely to be male (63% vs 47%; P < .0001), Black non-Hispanic (17% vs 13%; P < .0001), and rural (25% vs 21%; P < .0001) than those without prior minor amputation. The 5-year Kaplan-Meier cumulative incidence of major amputation was 27% (n = 58,613) of patients with prior minor amputation, compared with 1.4% (n = 129,872) of patients without prior minor amputation. After risk-adjustment, patients with prior minor amputations were 6.1-fold more likely to require a subsequent major amputation (hazard ratio, 6.11; 95% confidence interval, 6.04-6.18) compared with those without prior minor amputations. CONCLUSIONS: This contemporary claims-based analysis demonstrates that approximately 25% of Medicare beneficiaries with DM/PAD and prior minor amputation will necessitate a major amputation within 5 years. Prior minor amputation carries a risk of major amputation comparable with de novo tissue loss and is a stronger predictor than any demographic or socioeconomic exposure. These results help to inform both clinical decision-making and anticipated real-world outcomes among those at greatest risk for limb loss.