Association of preoperative systemic immune-inflammation index and geriatric nutritional risk index with prolonged postoperative length of stay in older patients with hip fracture: A retrospective cohort study

This study aimed to evaluate the associations of the preoperative systemic immune-inflammation index (SII), geriatric nutritional risk index (GNRI), and their joint exposure with prolonged postoperative length of stay (LOS) in older patients undergoing hip fracture surgery. This retrospective cohort study included older patients who underwent surgery for hip fracture. SII was calculated from preoperative platelet, neutrophil, and lymphocyte counts, and GNRI from albumin and body weight. High SII was defined as above the cohort-specific 75th percentile, GNRI ≤98 as nutritional risk, and prolonged postoperative LOS as above the cohort-specific 75th percentile. Logistic regression was used to assess associations of SII, GNRI, and their joint exposure with prolonged postoperative LOS, adjusting for age, sex, Charlson comorbidity index, fracture type, and preoperative waiting time. Interaction, discrimination, subgroup, and sensitivity analyses were also performed. Among 653 patients, higher log(SII) was associated with greater odds of prolonged postoperative LOS (OR = 2.23, 95% confidence interval [CI] 1.68-2.94), as was each 10-point decrease in GNRI (OR = 1.84, 95% CI 1.26-2.68). Compared with patients with non-high SII and no nutritional risk, those with both high SII and GNRI-defined nutritional risk had substantially higher odds of prolonged postoperative LOS (OR = 10.16, 95% CI 5.52-18.67). Each 1-point increase in the SII-GNRI risk burden score was associated with higher odds (OR = 3.30, 95% CI 2.42-4.51; P for trend <.001). Multiplicative interaction was not significant (P = .138), whereas exploratory OR-based additive interaction measures were positive. The clinical model area under the receiver operating characteristic curve increased from 0.697 to 0.774 after adding SII-GNRI joint exposure. Findings were generally consistent across subgroup and sensitivity analyses. Coexisting high SII and GNRI-defined nutritional risk may identify older patients with higher odds of prolonged postoperative LOS after hip fracture surgery. Joint assessment of inflammatory and nutritional status may provide additional information for perioperative risk stratification. Given the single-center retrospective design, cohort-derived thresholds, and lack of validation, these findings are preliminary and require confirmation in independent populations.