Precision risk stratification for perioperative safety of minimally invasive versus open TLIF in elderly patients with lumbar degenerative disease

Lumbar degenerative disease is highly prevalent in elderly patients, and transforaminal lumbar interbody fusion (TLIF) is a standard surgical treatment. However, the comparative safety of minimally invasive (MIS-TLIF) versus open TLIF in this vulnerable population remains incompletely defined, particularly regarding effect modifiers and underlying mechanisms. This retrospective cohort study included 728 patients aged ≥ 60 years who underwent primary TLIF, with 1:1 propensity score matching (PSM) performed to balance baseline characteristics. Perioperative outcomes were compared, and 30-day complications were analyzed using the Fine-Gray competing risk model. Subgroup analysis, mediation analysis, and a gradient boosting machine learning predictive model were conducted to explore effect heterogeneity, mechanisms, and risk stratification. After PSM, all baseline variables were well balanced (all standardized mean differences < 0.05). The MIS-TLIF group exhibited significantly shorter operative time, less intraoperative blood loss, lower transfusion rates, faster postoperative recovery, and reduced 30-day and 90-day unplanned readmission rates (all P < 0.001). After adjusting for competing risks, MIS-TLIF was associated with a 52% lower risk of any 30-day complication (adjusted subdistribution hazard ratio [SHR] = 0.48, 95% CI 0.34–0.68, P < 0.001) and a 61% lower risk of major complications (adjusted SHR = 0.39, 95% CI 0.21–0.72, P = 0.003). Subgroup analysis revealed significant interactions between treatment effect and age (P for interaction = 0.007) and frailty index (P for interaction < 0.001), with exponentially greater benefits observed in patients aged ≥ 72 years and frail patients. Intraoperative blood loss and operative time mediated 41.3% and 18.9% of the total protective effect, respectively, with a total mediating effect of 60.2%. The predictive model achieved an area under the receiver operating characteristic curve of 0.83 in the validation set, and the relative risk reduction of complications with MIS-TLIF reached 78% in the very high-risk group. MIS-TLIF significantly improves perioperative safety in elderly patients with lumbar degenerative disease, with the greatest benefit in high-risk subgroups. The developed risk prediction model can facilitate personalized surgical decision-making for this population.