Digital Arterial Calcification and Major Limb Amputation Risk in Patients With Chronic Limb-Threatening Ischemia at a Safety-Net Hospital.

BACKGROUND: Digital arterial calcification (DAC), defined as calcification of the hallux or digital arteries on plain foot radiograph, is a binary subcomponent of the pedal medial arterial calcification (pMAC) score. Its association with major limb amputation in a safety-net population remains uncharacterized. METHODS: Single-center retrospective cohort study of patients with chronic limb-threatening ischemia (CLTI) undergoing infrainguinal revascularization at a safety-net hospital (2020-2024). Inter-rater reliability was assessed by Cohen's κ. Factors associated with DAC were identified by multivariable logistic regression. Major amputation and all-cause mortality were analyzed by Kaplan-Meier and Cox proportional hazards regression; bilateral limb pairs were accounted for using robust sandwich variance estimators. RESULTS: Among 146 limbs in 132 patients, DAC was present in 49.3% (inter-rater κ = 0.904). Factors independently associated with DAC included ESRD (OR 7.05; p < .001), insulin-dependent diabetes (OR 3.68; p = .007), and active tobacco use (OR 0.35; p = .043), while prior revascularization was inversely associated with DAC (OR 0.22; p = .026). DAC was associated with lower freedom from major amputation on Kaplan-Meier analysis (p = .046) and an unadjusted hazard ratio of 2.14 (95% CI 1.00-4.59; p = .050), which attenuated after multivariable adjustment (aHR 1.65; 95% CI 0.74-3.68; p = .218). DAC was not associated with mortality (aHR 0.94; p = .884). CONCLUSION: In this safety-net CLTI cohort, DAC was present in half of the limbs and was associated with lower freedom from amputation on unadjusted analysis, though this attenuated after multivariable adjustment. Its single-radiograph nature makes DAC a practical risk stratification candidate in resource-limited settings.