Preoperative triglyceride-glucose index as a metabolic predictor of surgical site infection after posterior lumbar fusion.

PurposeTo assess whether the preoperative triglyceride-glucose (TyG) index is associated with 30-day surgical site infection (SSI) after instrumented posterior lumbar fusion (PLF) and to examine its predictive performance.MethodsWe retrospectively reviewed consecutive adults who underwent elective one- or two-level instrumented PLF between 2017 and 2024 at a tertiary center. Patients with active infection, revision surgery, tumor, trauma, or incomplete 30-day follow-up were excluded. Preoperative fasting triglycerides and glucose were used to calculate the TyG index as ln[(triglycerides × glucose)/2]. The primary outcome was 30-day SSI defined by Centers for Disease Control and Prevention criteria. Multivariable logistic regression evaluated the association between TyG and SSI, and receiver operating characteristic analysis assessed discrimination and identified an optimal cut-off. Incremental predictive value was examined by comparing a clinical model with and without TyG using AUC, likelihood ratio testing, reclassification metrics, calibration, Brier score, and decision curve analysis with bootstrap internal validation.ResultsAmong 438 patients, 29 (6.6%) developed SSI (24 superficial, 2 deep, 3 organ/space). Patients with SSI had higher TyG values than non-SSI patients (9.1 ± 0.5 vs 8.6 ± 0.6; p < 0.001). Each 1-unit increase in TyG was independently associated with higher odds of SSI (adjusted odds ratio 3.65; 95% confidence interval 1.62-8.24; p = 0.002). TyG alone yielded an area under the curve of 0.73, and a cut-off of 8.80 identified a high-risk group with an SSI rate of 11.8% versus 2.5% in the low-TyG group. Beyond standard clinical factors, adding TyG improved model fit (LRT χ2 = 10.98; p = 0.001) and improved reclassification.ConclusionA higher preoperative TyG index is independently associated with 30-day SSI after PLF and provides moderate discriminative ability as a simple predictor. Incorporating TyG into preoperative risk assessment may help refine perioperative optimization and infection surveillance strategies in lumbar fusion surgery.