Do postoperative changes in physical function affect patient-reported outcomes in patients with lumbar spinal stenosis who underwent a rehabilitation program?

To investigate the relationships between changes in objective physical function and changes in PROMs in patients with LSS who underwent lumbar surgery.

This was a secondary analysis of a randomized controlled trial, in which patients with LSS undergoing lumbar surgery received an inpatient postoperative rehabilitation program with either amino acids or a non-protein supplement for 3 weeks. Objective physical assessments included gait speed, a Timed Up and Go test, hand grip and knee muscle strength, and bioelectrical impedance analysis for skeletal muscle at 3 months. PROMs included the Zurich Claudication Questionnaire (ZCQ), a numerical rating scale for back pain, leg pain, and leg numbness, the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire, and the 36-item Short-Form Survey (SF-36) at 3 and 12 months. Stepwise linear regression analysis was used to identify unique factors associated with changes in PROMs. The changes in objective physical assessments and PROMs with p .0.05 in the Spearman correlational analyses were entered as independent variables.

A total of 80 patients (40 males and 40 females, average age 70.4 years) were included. At 3 months, significant but small correlations were observed between the change in gait speed (r = –0.25) or knee extensor strength (r = –0.31) and the change in the ZCQ symptom severity subscale, and between the change in gait speed (r = –0.29) or appendicular skeletal muscle mass index (r = 0.23) and the change in the ZCQ physical function subscale. At 12 months, there was a small correlation between the changes in gait speed and SF-36 physical functioning subscale (r = –0.29). Stepwise linear regression analysis showed that the change in knee extensor strength was significantly associated with the change in ZCQ symptom severity subscale at 3 months (R² = 0.53), explaining a further 3% variance in the improvement of ZCQ symptom severity score could be accounted for by the improvement in knee extensor strength. The change in gait speed was associated with the change in SF-36 physical functioning subscale at 12 months (R² = 0.65, 5% variance). 

In LSS patients who underwent surgery and a prospective rehabilitation program, improvements in knee extensor strength and gait speed contributed to improvements in a limited number of PROMs, but their overall impact was small.

While lower limb function plays a limited role in patient-perceived changes in pain, disability, and quality of life after lumbar surgery, it is considered important to assess long-term health outcomes, including the development of sarcopenia, healthy life expectancy, mortality, and medical costs.