The 5-Item Modified Frailty Index Is Predictive of Severe Adverse Events in Patients Undergoing Surgery for Adult Spinal Deformity

Study Design.A retrospective review of 281 consecutive cases of adult spine deformity (ASD) surgery (age 55 ± 19 yrs, 91% female, follow-up 4.3 ± 1.9 yrs) from a multicenter database.Objective.To compare the value and predictive ability of the 5-item modified frailty index (mFI-5) to the conventional 11-item modified frailty index (mFI-11) for severe adverse events (SAEs).Summary of Background Data.Several recent studies have described associations between frailty and surgical complications. However, the predictive power and usefulness of the mFI-5 have not been proven.Methods.SAEs were defined as: Clavien-Dindo grade >3, reoperation required, deterioration of motor function at discharge, or new motor deficit within 2 years. The patients' frailty was categorized by the mFI-5 and mFI-11 (robust, prefrail, or frail). Spearman's rho was used to assess correlation between the mFI-5 and mFI-11. Univariate and multivariate Poisson regression analyses were conducted to analyze the relative risk of mFI-5 and mFI-11 as a predictor for SAEs in ASD surgery. Age, sex, and baseline sagittal alignment (Schwab-SRS classification subcategories) were used to adjust the baseline variance of the patients.Results.Of the 281 patients, 63 (22%) had developed SAE at 2 years. The weighted Kappa ratio between the mFI-5 and mFI-11 was 0.87, indicating excellent concordance across ASD surgery. Frailty was associated with increased total complications, perioperative complications, implant-related complications, and SAEs. Adjusted and unadjusted models showed similar c-statistics for mFI-5 and mFI-11 and a strong predictive ability for SAEs in ASD surgery. As the mFI-5 increased from 0 to ≥2, the rate of SAEs increased from 17% to 63% (P < 0.01), and the relative risk was 2.2 (95% CI: 1.3-3.7).Conclusion.The mFI-5 and the mFI-11 were equally effective predictors of SEA development in ASD surgery. The evaluation of patient frailty using mFI-5 may help surgeons optimize procedures and counsel patients.Level of Evidence: 4.