Introduction: Frailty, marked by declines in weight, exhaustion, weakness, and physical activity, is a predictor of postoperative outcomes in spine surgery. Previous studies have focused on a limited set of indices, neglecting other critical aspects of frailty. This systematic review addresses these gaps by assessing the prevalence of all frailty indices and their association with clinical outcomes in spine surgery. We hypothesize significant variation in frailty measures and propose that "frailty" is often misapplied in spine surgery literature.
Methods: This review adhered to PRISMA guidelines, with an extensive search of PubMed, Scopus, and Web of Science, identifying 34 relevant studies on frailty in elective spine surgery. Studies were included if they used a frailty index, were primary cohort studies, and focused on elective procedures. Data were collected on frailty indices, medical and surgical complications, and perioperative events like non-routine discharge, reoperation, readmission, and mortality.
Results: The modified frailty index (mFI) was the most used measure, with the mFI-11 employed in 38% of studies and the mFI-5 in 29%. The Hospital Frailty Risk Score appeared in 9%, while less frequently used indices included the Adult Spinal Deformity Frailty Index and FRAIL (6% each). Other indices, like the Fried Frailty Index and Canadian Study of Health and Aging Clinical Frailty Scale, were used in 3% of studies. Sarcopenia was the most assessed frailty-related term (12%). Frailty was treated as an independent variable in 94% of studies, and complications were reported in 85%. Medical and surgical complications were seen in 67% and 62% of studies, respectively, while non-routine discharge occurred in 47%, readmissions in 29%, and mortality in 26%.
Conclusion : While the mFI-5 and mFI-11 are the most frequently used frailty measures in spine surgery literature, their comorbidity-based approach limits their ability to capture the multidimensional decline in physiological reserves that defines frailty. Future research should prioritize the use of more comprehensive frailty indices, such as the Fried Frailty Index and FRAIL scale, which incorporate functional assessments to better stratify patient risk for spine surgery.
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