Optimization is a Moving Target: A Continuous Modifiable Frailty Index (o-ASD-FI) Reflecting Optimization Prior to Complex Adult Spinal Deformity (ASD) Intervention.

STUDY

DESIGN

Retrospective analysis of a multicenter complex adult spinal deformity (ASD) cohort.

OBJECTIVES

Develop a simplified, weighted, and modifiable ASD Frailty Index (o-ASD-FI) that incorporates modifiable health components.

BACKGROUND

Though newer frailty indices have emerged, none specifically addresses complex ASD while incorporating modifiable health factors.

METHODS

Miller's ASD-FI variables were evaluated via Pearson bivariate correlation and multiple stepwise regression. Ten frailty and three modifiable health factors (depression, diabetes, and osteoporosis) were identified and regressed against mortality, extended length of stay (LOS > 8 d), revisions, and major complications. Coefficients were weighted using Johnson's method to create the o-ASD-FI (range: 0 - 18). Frailty categories were defined as: not frail (<2), frail (≥2 and <7), and severely frail (≥7). Associations between frailty and pre- and postoperative factors were assessed via ANOVA.

RESULTS

Among 572 patients (mean ± SD age 60.6±15.7 years, BMI 27.3±5.4 kg/m², LOS 7.2±5.0 d), the final model explained 80.6% of the variance in the ASD-FI score. Key contributors (weights): smoking (3), osteoporosis (3), diabetes (2), cardiac disease (2), lifting impairment (2), leg weakness (2), disability (1), stair difficulty (1), depression (1), BMI extremes (1), and optimized depression, osteoporosis, or diabetes (-1 each). Mean o-ASD-FI score: 3.4±2.1. Most patients were frail (72.2%); 20.5% not frail, 7.3% severely frail. Greater frailty correlated with longer LOS (P<0.001), worse HRQoL (P<0.001), and poorer alignment (P<0.05). Frailty independently predicted higher odds of spine (OR 1.2), medical (1.09), intraoperative (1.1), and in-hospital adverse events (1.1), all P<0.01.

CONCLUSIONS

The newly developed simplified, weighted, and optimizable ASD Frailty Index (o-ASD-FI) incorporates modifiable health components, providing a robust assessment of physiological status and potentially superior risk stratification compared with existing tools for both primary and revision complex spinal deformity surgery.

LEVEL OF EVIDENCE: III.