Differences in treatment outcome between subgroups of patients with chronic low back pain using lumbar dynamometry and psychological aspects

Abstract

Objective: To investigate whether subgroups of patients with chronic low back pain show differences in treatment outcome, measured with the Roland Disability Questionnaire. (RDQ). Setting: The study was carried out in a rehabilitation centre. Subjects: Eighty-four patients with chronic low back pain participated in this study. Intervention: Patients followed a multidisciplinary treatment programme that primarily targets physical aspects. Design and main outcome measure: Based on pretreatment lumbar dynamometry results and Symptom Checklist (SCL-90) scores, patients were divided into subgroups. The dynamometry subgroups were: performances lower than healthy subjects (expected performance), performances comparable with those of healthy subjects (normal performance) and inconsistent performances (submaximal performance). The SCL-90 subgroups were: a total score of ‘average’ or lower compared with a population of chronic pain patients (low psychological score) and a total score of ‘above average’ or higher compared with this population (high psychological score). Patients answered the RDQ in the week before (RDQ1; n = 84) and after treatment (RDQ2; n = 78) to investigate whether the subgroups show differences in outcome expressed as the percentage change between RDQ2 and RDQ1 (%RDQ2–1). A%RDQ2–1 ≥ 20% was classified as an improvement. Results: Improvement on disability level ≥20% is shown in 64% and 55% of the patients with ‘normal’ and ‘expected’ lumbar dynamometry performances and low psychological scores compared with only 33% and 25% of those with high psychological scores. Patients with submaximal performances show hardly any changes in disability level and there are no differences between those with low psychological scores (14%) and those reporting high scores (0%). Conclusion: The fact that patient subgroups with differences in treatment outcome can be defined using lumbar dynamometry and psychological questionnaires suggests that these instruments might facilitate treatment indication in clinical practice.