Utility of the Combined Inflammatory–Nutritional Score for Predicting Major Amputation after Minor Amputation in Patients with Infected Foot Wounds

Purpose: Early identification of patients at high risk of a major amputation after a minor amputation remains challenging because of the multifactorial nature of infected foot wounds.This study evaluated the clinical utility of the combined inflammatory-nutritional score (CINS), integrating the C-reactive protein-to-albumin ratio (CAR), and systemic immune-inflammation index (SII), for predicting a major amputation.Materials and Methods: This retrospective single-center study included 195 patients who underwent a minor amputation for infected foot wounds between March 2004 and September 2025.A minor amputation was defined as an amputation distal to the ankle joint.CAR and SII were calculated from the admission laboratory data, and CINS was derived using the optimal cutoff values from receiver operating characteristic curve analysis.The primary outcome was a major amputation within 90 days after a minor amputation.The predictive performance was assessed using logistic regression, trend analysis, and receiver operating characteristic curve analysis.Results: Among the 195 patients, 29 (14.9%)underwent a major amputation within 90 days.The incidence of a major amputation increased across CINS categories: 2.6% in patients with a score of 0, 14.6% in those with a score of 1, and 19.4% in those with a score of 2, showing a borderline trend toward a higher risk (p for trend=0.050).Multivariable logistic regression adjusted for age, peripheral artery disease, chronic kidney disease, and revascularization showed that CINS was associated with a major amputation (odds ratio, 3.21; 95% confidence interval, 1.23~8.40;p=0.017).Peripheral artery disease was the strongest predictor.CINS showed a numerically higher area under the curve (AUC; 0.621) than CAR and SII alone.Conclusion: CINS may serve as a practical adjunctive biomarker for risk stratification after a minor amputation in patients with infected foot wounds.Although its discriminative ability was modest, CINS showed a numerically higher AUC than individual markers and may support the early identification of high-risk patients, particularly those with peripheral artery disease.