Objectives: Treatment guidelines recommend targeting both physical and psychological factors in interventions for degenerative lumbar spine disorders. Studying the treatment mechanisms gives information on key factors explaining the outcome improvement that can refine treatments. This study explores treatment mediators in a physiotherapy treatment on disability, pain intensity, and health-related quality of life in surgical candidates with degenerative lumbar spine disorders compared with waiting-list controls. An additional aim was to evaluate patients' expectation as a moderator of treatment outcome.
Materials and methods: Data collected from 197 patients in a single-blinded randomized controlled trial comparing 9 weeks of multifaceted physiotherapy with waiting-list controls were used in this conditional process analysis. Analysis was carried out on group differences for change in Oswestry Disability Index, Pain Visual Analog Scale (VAS) back pain, EuroQol-5D, and EuroQol-VAS. The putative moderation role of expectations and mediation role of change in physical variables and psychosocial variables were tested.
Results: Change in self-efficacy mediated improvement in all outcomes. Improvement in Oswestry Disability Index was also mediated by change in depression; VAS was mediated by change in fear-avoidance beliefs; and EuroQol-VAS was mediated by change in activity level and fear avoidance beliefs. Improvements were moderated by patients' treatment expectations.
Discussion: Self-efficacy, fear-avoidance beliefs, physical activity level, and patients' treatment expectations were found to be important factors explaining treatment effects. Self-efficacy was the consistent mediator for effects of the presurgical physiotherapy on disability, back pain intensity, and health-related quality of life.
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