Exploring Associations of Preoperative Physical Performance With Postoperative Outcomes After Lumbar Spinal Fusion: A Machine Learning Approach

Objective: To explore the association between preoperative physical performance with short- and long-term postoperative outcomes in patients undergoing lumbar spinal fusion (LSF). Design: Retrospective cohort. Setting: University hospital. Participants: Seventy-seven patients (N=77) undergoing elective LSF were preoperatively screened on patient demographics, patient-reported outcome measures, and physical performance measures (movement control, back muscle endurance strength and extensor strength, aerobic capacity, flexibility). Interventions: Not applicable. Main Outcome Measures: Associations between preoperative variables and inpatient functional recovery, hospital length of stay (LOS), and 1- to 2-year postoperative pain reduction were explored using random forest analyses assessing the relative influence of the variable on the outcome. Results: Aerobic capacity was associated with fast functional recovery <4 days and prolonged functional recovery >5 days (median z scores=7.1 and 12.0). Flexibility (median z score=4.3) and back muscle endurance strength (median z score=7.8) were associated with fast functional recovery <4 days. Maximum back extensor strength was associated with prolonged functional recovery >5 days (median z score=8.6). Flexibility (median z score=5.1) and back muscle endurance strength (median z score=13.5) were associated with short LOS <5 days. Aerobic capacity (median z score=8.7) was associated with prolonged LOS >7 days. Maximum back extensor strength (median z score=3.8) was associated with 1- to 2-year postoperative pain reduction and aerobic capacity (median z score=2.8) was tentative. Conclusions: Physical performance measures were associated with both short- and long-term outcomes after LSF. Adding these measures to prediction models predicting outcomes after LSF may increase their accuracy.