Modified Frailty Index Does Not Provide Additional Value in Predicting Outcomes in Patients Undergoing Elective Transforaminal Lumbar Interbody Fusion

To determine the predictive value of the modified Frailty Index (mFI) in evaluating sarcopenia and clinical outcomes in patients undergoing 1-level or 2-level transforaminal lumbar interbody fusion (TLIF). Patients who underwent a 1-level or 2-level TLIF between 2012 and 2020 were retrospectively identified. Frailty was compared among groups using mFI, and sarcopenia was classified by the psoas muscle cross-sectional area. Bivariate statistics compared demographics, comorbidities, and clinical outcomes. A linear regression model was developed using the Charlson Comorbidity Index (CCI) or mFI as independent variables to determine potential predictors for improvement in 1-year patient-reported outcomes. Of 488 included patients, 60 were severely frail and 60 patients had sarcopenia, but sarcopenia was not associated with patient frailty (P = 0.469). Severely frail patients had worse baseline Oswestry Disability Index (ODI) (P < 0.001), Mental Component Score–12 (P = 0.001), and Physical Component Score–12 (P < 0.001), and worse improvement in ODI (P = 0.037), Physical Component Score–12 (P < 0.001), and visual analog scale (VAS) back (P = 0.007). mFI was an independent predictor of poorer improvement in VAS back and ODI, whereas age + CCI in addition predicted poorer improvement in VAS leg. Patients with higher mFI experienced longer length of stay, less frequent home discharge, and higher rates of complications, but similar readmission and reoperation rates. Frailer patients experience poorer improvement in back pain, physical functioning, and disability after TLIF. mFI and the combination of age and CCI comparably predict patient-reported outcomes but do not correlate to baseline sarcopenia. Frailty increased the risk of complications, length of hospital stay, and risk of nonhome discharge.