Study design: Meta-analysis methodology was extended to derive comparative effectiveness information on spinal manipulation for low back pain.
Objective: Determine relative effectiveness of spinal manipulation therapies (SMTs), medical management, physical therapies, and exercise for acute and chronic nonsurgical low back pain.
Summary of background data: Results of spinal manipulation treatments of nonsurgical low back pain are equivocal. Nearly 40 years of SMT studies were not informative.
Methods: Studies were chosen on the basis of inclusion in prior evidence syntheses. Effect sizes were converted to standardized mean effect sizes and probabilities of recovery. Nested model comparisons isolated nonspecific from treatment effects. Aggregate data were tested for evidential support as compared with shams.
Results: Of 84% acute pain variance, 81% was from nonspecific factors and 3% from treatment. No treatment for acute pain exceeded sham's effectiveness. Most acute results were within 95% confidence bands of that predicted by natural history alone. For chronic pain, 66% of 98% was nonspecific, but treatments influenced 32% of outcomes. Chronic pain treatments also fit within 95% confidence bands as predicted by natural history. Though the evidential support for treating chronic back pain as compared with sham groups was weak, chronic pain seemed to respond to SMT, whereas whole systems of clinical management did not.
Conclusion: Meta-analyses can extract comparative effectiveness information from existing literature. The relatively small portion of outcomes attributable to treatment explains why past research results fail to converge on stable estimates. The probability of treatment superiority matched a binomial random process. Treatments serve to motivate, reassure, and calibrate patient expectations--features that might reduce medicalization and augment self-care. Exercise with authoritative support is an effective strategy for acute and chronic low back pain.