A High Frailty Burden is a Strong Predictor of Adverse Postoperative Outcomes in Geriatric Lumbar Spine Surgery: A Retrospective Cohort Study

Study Design Retrospective cohort study. Objectives To determine whether the 5-item modified frailty index (mFI-5) is associated with in-hospital complications and 1-year adverse events among patients aged ≥70 years who underwent lumbar spine surgery. Methods We retrospectively reviewed data from patients aged ≥70 years who underwent lumbar spine surgery at a single tertiary referral hospital from January 2020 to December 2021, with 1-year follow-up. Participants were stratified into two groups based on an mFI-5 score of 3. The primary outcome was the odds of in-hospital complications, and the secondary outcome was the odds of 1-year adverse events. To account for confounding variables and identify independent predictors, we applied inverse probability of treatment weighting (IPTW) and multivariable logistic regression. Results Among 967 eligible older adults, 132 (13.6%) met the criteria for severe frailty (mFI-5 score ≥3). Following IPTW adjustment, severe frailty was significantly and independently associated with in-hospital complications (odds ratio: 1.792, 95% confidence interval: 1.243–2.585; P = 0.002). Higher American Society of Anesthesiologists Physical Status scores, functional dependence, and in-hospital complications were strong predictors of 1-year adverse events. Conclusion Severe frailty was independently associated with in-hospital complications in older adults undergoing lumbar spine surgery. The mFI-5 may serve as a practical tool for stratifying preoperative surgical risk and tailoring perioperative management.