OBJECTIVE: Black patients are substantially more likely than whites to undergo amputation rather than revascularization for lower-extremity arterial disease. Because their care is disproportionately concentrated among a small share of providers, some have attributed such disparities to the quality and capacity of these sites. We investigated whether racial gaps are minimized by high-quality providers, or instead, differential treatment of otherwise similar patients pervades all settings.
METHODS: We evaluated all 86,865 white or black fee-for-service Medicare beneficiaries 65 and older who underwent major lower-extremity vascular procedures. Using generalized linear mixed models with random effects, we computed risk-adjusted odds of amputation by race overall, and after serial substratification by salient patient and provider characteristics.

RESULTS: Blacks were far more likely to undergo amputation (45% versus 20%). Their procedures were performed more often by non-specialists (41% versus 27%; p<0.001), in low-volume hospitals (40% versus 32%; p<0.001), with high amputation rates (53% versus 29%; p<0.001). Controlling for differences in comorbidity, disease severity, and surgeon and hospital performance, blacks’ odds of amputation remained 1.7 times greater (95%CI 1.6-1.9). Even among highest-performing providers--vascular specialists in high-volume, urban teaching hospitals with angioplasty facilities--racial gaps persisted (risk-adjusted amputation rates: 7% for blacks versus 4% for whites, p<0.001; odds ratio 1.8, 95%CI 1.5-2.1).
CONCLUSIONS: Black patients with critical limb ischemia face significantly higher risk of major amputation, even when treated by providers with highest likelihoods of revascularization. Increased referral to high-performing providers might increase limb-preservation, but will not eliminate disparities until equitable treatment is ensured in all settings.