Some experts concede that chiropractic spinal manipulation is effective for chronic low back pain (cLBP). But what is the right dose? There have been no full-scale trials of the optimal number of treatments with spinal manipulation. This study was aimed at filling this gap by trying to identify a dose-response relationship between the number of visits to a chiropractor for spinal manipulation and cLBP outcomes. A further aim was to determine the efficacy of manipulation by comparison with a light massage control.
The primary cLBP outcomes were the 100-point pain intensity scale and functional disability scales evaluated at the 12- and 24-week primary end points. Secondary outcomes included days with pain and functional disability, pain unpleasantness, global perceived improvement, medication use, and general health status.
One hundred patients with cLBP were randomized to each of 4 dose levels of care: 0, 6, 12, or 18 sessions of spinal manipulation from a chiropractor. Participants were treated three times per week for 6 weeks. At sessions when manipulation was not assigned, the patients received a focused light massage control. Covariate-adjusted linear dose effects and comparisons with the no-manipulation control group were evaluated at 6, 12, 18, 24, 39, and 52 weeks.
For the primary outcomes, mean pain and disability improvement in the manipulation groups were 20 points by 12 weeks, an effect that was sustainable to 52 weeks. Linear dose-response effects were small, reaching about two points per 6 manipulation sessions at 12 and 52 weeks for both variables. At 12 weeks, the greatest differences compared to the no-manipulation controls were found for 12 sessions (8.6 pain and 7.6 disability points); at 24 weeks, differences were negligible; and at 52 weeks, the greatest group differences were seen for 18 visits (5.9 pain and 8.8 disability points).
The authors concluded that the number of spinal manipulation visits had modest effects on cLBP outcomes above those of 18 hands-on visits to a chiropractor. Overall, 12 visits yielded the most favorable results but was not well distinguished from other dose levels.
This study is interesting because it confirms that the effects of chiropractic spinal manipulation as a treatment for cLBP are tiny and probably not clinically relevant. And even these tiny effects might not be due to the treatment per se but could be caused by residual confounding and bias.
As for the optimal dose, the authors suggest that, on average, 18 sessions might be the best. But again, we have to be clear that the dose-response effects were small and of doubtful clinical relevance. Since the therapeutic effects are tiny, it is obviously difficult to establish a dose-response relationship.
In view of the cost of chiropractic spinal manipulation and the uncertainty about its safety, I would probably not rate this approach as the treatment of choice but would consider the current Cochrane review which concludes that “high quality evidence suggests that there is no clinically relevant difference between spinal manipulation and other interventions for reducing pain and improving function in patients with chronic low-back pain” Personally, I think it is more prudent to recommend exercise, back school, massage or perhaps even yoga to cLBP-sufferers.