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

To investigate whether subgroups of patients with chronic low back pain show differences in treatment outcome, measured with the Roland Disability Questionnaire. (RDQ).

The study was carried out in a rehabilitation centre.

Eighty-four patients with chronic low back pain participated in this study.

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 > or = 20% was classified as an improvement.

Improvement on disability level > or = 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 betweenthose with low psychological scores (14%) and those reporting high scores (0%).

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.