Active therapy for chronic low back pain Part 3. Factors influencing self-rated disability and its change following therapy

Design. Cross-sectional analysis of the factors influencing self-rated disa bility associated with chronic low back pain and prospective study of the r elationship between changes in each of these factors and in disability foll owing active therapy. Objectives. To examine the relative influences of pain, psychological facto rs, and physiological factors on self-rated disability. Summary of Background Date. In chronic LBP, the interrelationship between p hysical impairment, pain, and disability is particularly complicated, due t o the influence of various psychological factors and the lack of unequivoca l methods for assessing impairment. investigations using new "belief" quest ionnaires and "sophisticated" performance tests, which have shown promise a s discriminating measures of impairment, may assist in clarifying the situa tion. Previous studies have rarely investigated all these factors simultane ously. Methods. One hundred forty-eight patients with cLBP completed questionnaire s and underwent tests of mobility, strength, muscle activation, and fatigab ility, and (in a subgroup) erector spinae size and fiber size/type distribu tion. All measures were repeated after 3 months active therapy. Relationshi ps between each factor and self-rated disability (Roland and Morris questio nnaire) at baseline, and between the changes in each factor and changes in disability following therapy, were examined. Results. Stepwise linear regression showed that the most significant predic tors of disability at baseline were, in decreasing order of importance: pai n; psychological distress; fear-avoidance beliefs; muscle activation levels ; lumbar range of motion; gender. Only changes in pain, psychological distr ess, and fear-avoidance beliefs significantly accounted for the changes in disability following therapy. Conclusion. A combination of pain, psychological and physiological factors was best able to predict baseline disability, although its decrease followi ng therapy was determined only by reductions in pain and psychological vari ables. The active therapy programm-in addition to improving physical functi on-appeared capable of modifying important psychological factors, possibly as a result of the positive experience of completing the prescribed exercis es without undue harm.