Treatments for Back Pain: Can We Get Past Trivial Effects?

To the Editor:

Dr. Deyo raises several interesting considerations regarding the interpretation of our results(1) in his editorial.(2) Numerous previous studies, particularly those examining the outcomes of spinal manipulation, have resulted in relatively small effect sizes of modest clinical importance.(3) Had we simply compared the outcomes of manipulation versus an exercise intervention, our results would have favored manipulation by a statistically significant, but clinically trivial amount. However the treatment effects were about 70% greater in the sub-group of patients who fit the rule for predicting a favorable response to manipulation, supporting the notion that the solution to small treatment effects lies in the development of sub-grouping mechanisms that match patients to the treatment (or non-treatment) most likely to benefit them.

The issue of generalizability to other clinicians and different practice settings is a consideration in any randomized trial. Our anecdotal experience with therapists and patients in the military health care delivery system leads us to believe that the individuals generalize well to a civilian health care setting, however only further research can validate this assumption. Another concern was the legitimacy of the exercise treatment used. The exercise regimen used in our study was based on protocols that have been demonstrated to be effective for certain sub- groups of patients, including those with a first episode of acute back pain(4) and those with chronic back pain who had radiographic evidence of spondylolysis or spondylolisthesis,(5) suggesting this exercise regimen is beneficial for at least a subgroup of patients.

Dr. Deyo alludes to the role of patient expectations in explaining the response to various treatments. The literature clearly indicates that meeting a patient's expectation results in improved patient satisfaction. However, only limited evidence exists regarding the influence of patient expectations about specific treatments on clinical outcomes in patients with back pain. Among 78 patients in our study indicating an expectation that manipulation would be at least somewhat likely to benefit them, patients who received manipulation did experience a significantly greater reduction in disability after 1 week. However, the magnitude of this effect was clinically trivial and no longer significant after 4 weeks or 6 months. Among this same subgroup, patients who were positive on the rule and received manipulation still experienced significantly greater and clinically important reductions in disability and pain compared to patients negative on the rule receiving manipulation. In other words, consideration of the patient's status on the rule outweighed the influence of patient expectations.

Finally, we share Dr. Deyo's bewilderment as to why large trials are so scarce in musculoskeletal medicine. An example of one such trial has recently been published by our colleagues in the United Kingdom.(6) However, the record for funding similar research in the Unites States is less than stellar. Delayed recovery from back pain in particular is not a benign condition, being associated with enormous disability and health care costs. Until federal funding agencies appreciate the potential for large, pragmatic clinical trials to improve the care of patients with back pain, innovation and improvement in the management of back pain will continue to be slow and fragmented.

John D. Childs PT, Ph.D. childsjd@sbcglobal.net Wilford Hall Medical Center

Reference List

(1) Childs JD, Fritz JM, Flynn TW, Irrgang JJ, Johnson KK, Majkowski GR et al. A clinical prediction rule to identify patients with low back pain who will benefit from spinal manipulation: A validation study. Ann Intern Med. 2004;141:920-928.

(2) Deyo RA. Treatments for back pain: Can we get past trivial effects? (editorial). Ann Intern Med. 2004;141:957-58.

(3) Assendelft WJ, Morton SC, Yu EI, Suttorp MJ, Shekelle PG. Spinal manipulative therapy for low back pain. A meta-analysis of effectiveness relative to other therapies. Ann Intern Med. 2003;138:871-81.

(4) Hides JA, Jull GA, Richardson CA. Long-term effects of specific stabilizing exercises for first-episode low back pain. Spine. 2001;26:E243 -E248.

(5) O'Sullivan PB, Phyty GD, Twomey LT, Allison GT. Evaluation of specific stabilizing exercise in the treatment of chronic low back pain with radiologic diagnosis of spondylolysis or spondylolisthesis. Spine. 1997;22:2959-67.

(6) UK Beam Trial Team. United Kingdom back pain exercise and manipulation (UK BEAM) randomised trial: effectiveness of physical treatments for back pain in primary care. BMJ. 2004;329.

Conflict of Interest:

None declared