Risk Stratification of Elderly Patients Undergoing Spinal Surgery Using the Modified Frailty Index

Study Design: Retrospective cohort. Objectives: To validate the 11-item modified Frailty Index (mFI) as a perioperative risk stratification tool in elderly patients undergoing spine surgery. Methods: All consecutive cases of spine surgery in patients aged 65 years or older between July 2016 and June 2018 at a state-wide trauma center were retrospectively reviewed. The primary outcome was post-operative major complication rate (Clavien-Dindo Classification ≥ III). Secondary outcome measures included the rate of all complications, 6-month mortality and surgical site infection. Results: A total of 348 cases were identified. The major complication rate was significantly lower in patients with an mFI of 0 compared to ≥ 0.45 (18.3% versus 42.5%, P = .049). As the mFI increased from 0 to ≥ 0.45 there was a stepwise increase in risk of major complications ( P < .001). Additionally, 6-month mortality rate was considerably lower when the mFI was 0 rather than ≥ 0.27 (4.2% versus 20.4%, P = .007). Multivariate analysis demonstrated an mFI ≥ 0.27 was significantly associated with an increased incidence of major complication (OR 2.80, 95% CI 1.46-5.35, P = .002), all complication (OR 2.93, 95% CI 1.70-15.11, P < .001), 6-month mortality (OR 7.39, 95% CI 2.55-21.43, P < .001) and surgical site infection (OR 4.43, 95% CI 1.71-11.51, P = .002). The American Society of Anesthesiologists’ (ASA) index did not share a stepwise relationship with any outcome. Conclusion: The mFI is significantly associated in a gradated fashion with increased morbidity and mortality. Patients with an mFI ≥ 0.27 are at greater risk of major complications, all-complications, 6-monthy mortality, and surgical site infection.