Symptom relief does not fully reflect functional adaptation after lumbar decompression: longitudinal changes in lifting biomechanics following surgery for degenerative lumbar stenosis.

PURPOSE: Lumbar decompression effectively reduces pain and disability in patients with degenerative lumbar stenosis (DLS); however, it remains unclear whether symptomatic improvement is accompanied by restoration of functional movement during activities of daily living. This study evaluated longitudinal changes in lifting biomechanics and neuromuscular activation following lumbar decompression.

METHODS: Thirty-eight patients with symptomatic DLS underwent three-dimensional motion analysis and synchronized surface electromyography during a standardized symmetric lifting task approximately one week before surgery and again at 3 and 6 months postoperatively. Patient-reported outcome measures (ODI and PROMIS) were collected at each visit. Mixed-effects linear regression models evaluated longitudinal changes in kinematics and muscle activation.

RESULTS: Lumbar decompression produced significant improvements in disability, physical function, pain interference, and mood within three months that were maintained at six months. Despite these improvements, objective movement patterns continued to change through six months, with persistent biomechanical and neuromuscular adaptations. Postoperatively, patients demonstrated greater trunk and lumbar flexion, reduced frontal and transverse plane lower-extremity motion, and altered neuromuscular activation characterized by increased external oblique activity and shorter activation durations of the rectus femoris and gluteus maximus, whereas persistent adaptations remained in the tibialis anterior and erector spinae. Patients lifted heavier loads after surgery without significant changes in task completion time, indicating improved quality of movement rather than faster task performance.

CONCLUSIONS: Following lumbar decompression, improvements in patient-reported pain and disability were accompanied by longitudinal changes in lifting biomechanics and neuromuscular control; however, these objective adaptations remained evident through six months. These findings suggest that symptomatic improvement and objective functional adaptation represent complementary but distinct dimensions of postoperative recovery. Objective biomechanical assessment may therefore provide clinically relevant information beyond PROMs by characterizing how patients adapt movement strategies during recovery.