Preoperative aggregate index of systemic inflammation and cause-specific 1-year mortality after surgery for geriatric intertrochanteric fracture

Abstract

Older adults undergoing intertrochanteric-fracture surgery have high 1-year mortality. Routine preoperative complete blood count indices may provide readily available prognostic information before surgery. This prospective single-center cohort enrolled consecutive patients aged ≥ 65 years undergoing surgery for low-energy femoral intertrochanteric fracture from July 1, 2023, to December 31, 2024. The Aggregate Index of Systemic Inflammation (AISI) was calculated from the earliest eligible preoperative complete blood count, transformed using the natural logarithm (ln-AISI) and standardized. The primary outcome was adjudicated fracture- or surgery-related death within 365 days; non-fracture death was treated as a competing event. Fine-Gray models estimated sub-distribution hazard ratios (sHRs). Exploratory analyses used an expanded confounder model and internally validated clinical prediction models with separate additions of the neutrophil-to-lymphocyte ratio, systemic immune-inflammation index, or ln-AISI. Among 587 patients, 365-day vital status was confirmed for 575 (98.0%); 12 were censored before 365 days. During follow-up, 119 patients died: 73 fracture- or surgery-related deaths and 46 non-fracture deaths. The 365-day cumulative incidence of the primary outcome increased across AISI tertiles (6.8%, 12.3%, and 18.6%; Gray’s test, p < 0.001). Each 1 standard deviation (SD) increase in ln-AISI was associated with a higher subdistribution hazard for the primary event (adjusted sHR, 1.43; 95% confidence interval [CI], 1.19–1.72; p < 0.001). The highest versus lowest tertile sHR was 2.11 (95% CI, 1.31–3.41; p = 0.002). All-cause mortality was also associated with ln-AISI (hazard ratio [HR], 1.35; 95% CI, 1.13–1.62; p = 0.001). In the expanded confounder model, each 1-SD higher ln-AISI had an sHR of 1.26 (95% CI, 1.03–1.54; p = 0.025). Adding ln-AISI to the clinical model changed the optimism-corrected 365-day area under the curve (AUC) from 0.724 to 0.737 (difference, 0.013; 95% CI, -0.002 to 0.029). Elevated preoperative AISI was associated with higher 1-year fracture- or surgery-related mortality and all-cause mortality after geriatric intertrochanteric-fracture surgery. Internal validation showed only a modest gain in predictive performance, and external validation is required before clinical use. Not applicable.