Prognostic performance of the albumin–gluteus medius index for one-year mortality in geriatric hip fracture patients: a retrospective cohort study

Proximal femur fractures are associated with high mortality in older adults, and accurate prognostic assessment is clinically important. The Albumin–Gluteus Medius Index (AGMI) is a novel composite index integrating CT-derived muscle reserve with serum albumin, an inflammatory and metabolic prognostic biomarker. This study aimed to evaluate the prognostic performance of AGMI in predicting one-year mortality in geriatric patients with hip fracture and to compare its discriminative ability with serum albumin and gluteus medius muscle area individually. This retrospective study included 219 patients aged ≥ 65 years who were treated for hip fracture between January 2021 and May 2025. Gluteus medius muscle area was measured from pelvic CT, and serum albumin levels were recorded. AGMI was calculated as the product of albumin (g/L) and muscle area (mm²). Independent predictors of mortality were assessed using multivariable logistic regression. Discriminative performance was evaluated using receiver operating characteristic (ROC) curve analysis. The one-year mortality rate was 14.6%. AGMI was significantly lower in non-survivors than in survivors ( p < 0.001). In multivariable analysis, age ( p = 0.011), male sex ( p = 0.046), and AGMI were independently associated with one-year mortality. Each 1,000-unit increase in AGMI was associated with a 3% reduction in the odds of mortality (OR 0.97, 95% CI 0.96–0.98; p < 0.001). Among the individual markers, AGMI had the highest observed AUC (0.762, 95% CI 0.676–0.849); however, paired DeLong comparisons with serum albumin and gluteus medius muscle area were not statistically significant. AGMI was independently associated with one-year mortality and had the numerically highest discrimination among the individual markers evaluated. If externally validated, this accessible composite biomarker may serve as an adjunctive tool for early risk stratification in geriatric patients with hip fracture.