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

Objective: To investigate whether subgroups of patients with chronic low ba ck pain show differences in treatment outcome, measured with the Roland Dis ability Questionnaire, (RDQ). Setting: The study was carried out in a rehabilitation centre. Subjects: Eighty-four patients with chronic low back pain participated in t his study. Intervention: Patients followed a multidisciplinary treatment programme tha t primarily targets physical aspects. Design and main outcome measure: Based on pretreatment lumbar dynamometry r esults and Symptom Checklist (SCL-90) scores, patients were divided into su bgroups. The dynamometry subgroups were: performances lower than healthy su bjects (expected performance), performances comparable with those of health y subjects (normal performance) and inconsistent performances (submaximal p erformance). The SCL-90 subgroups were: a total score of 'average' or lower compared with a population of chronic pain patients (low psychological sco re) and a total score of 'above average' or higher compared with this popul ation (high psychological score). Patients answered the RDQ in the week bef ore (RDQ(1); n = 84) and after treatment (RDQ(2); n = 78) to investigate wh ether the subgroups show differences in outcome expressed as the percentage change between RDQ(2) and RDQ(1) (%RDQ(2-1)), A %RDQ(2-1) greater than or equal to 20% was classified as an improvement. Results: Improvement on disability level greater than or equal to 20% is sh own in 64% and 55% of the patients with 'normal' and 'expected' lumbar dyna mometry performances and low psychological scores compared with only 33% an d 25% of those with high psychological scores. Patients with submaximal per formances show hardly any changes in disability level and there are no diff erences between those with low psychological scores (14%) and those reporti ng high scores (0%). Conclusion: The fact that patient subgroups with differences in treatment o utcome can be defined using lumbar dynamometry and psychological questionna ires suggests that these instruments might facilitate treatment indication in clinical practice.