Dose-response and efficacy of spinal manipulation for care of chronic low back pain: a randomized controlled trial

Abstract

Background context: There have been no full-scale trials of the optimal number of visits for the care of any condition with spinal manipulation.

Purpose: To identify the dose-response relationship between visits to a chiropractor for spinal manipulation and chronic low back pain (cLBP) outcomes and to determine the efficacy of manipulation by comparison with a light massage control.

Study design/setting: Practice-based randomized controlled trial.

Patient sample: Four hundred participants with cLBP.

Outcome measures: The primary cLBP outcomes were the 100-point modified Von Korff pain intensity 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.

Methods: One hundred participants with cLBP were randomized to each of four 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, they 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.

Results: For the primary outcomes, mean pain and disability improvement in the manipulation groups were 20 points by 12 weeks and sustainable to 52 weeks. Linear dose-response effects were small, reaching about two points per six manipulation sessions at 12 and 52 weeks for both variables (p<.025). At 12 weeks, the greatest differences from the no-manipulation control were found for 12 sessions (8.6 pain and 7.6 disability points, p<.025); 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, p<.025).

Conclusions: 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.

Trial registration: ClinicalTrials.gov NCT00376350.

Keywords: Chiropractic; Chronic low back pain; Dose-response; Randomized controlled trial; Spinal manipulation.

Fig. 1

Study flow diagram. All participants were assigned 18 treatment visits. They received either spinal manipulative therapy (SMT) or light massage control (LM) at any one visit.

Fig 2

Pain time profile. Pain intensity was evaluated on a 0 to 100 scale. The graphs show pain development for each group at baseline and the six follow-up time points. The primary endpoints were 12 and 24 weeks.

Fig. 3

Pain dose-response curves. The dose-response plots demonstrate small gradients in pain intensity (0 to 100 point scale) across dose groups for four time points: end of care (6 weeks), primary endpoints (12 and 24 weeks), and the final follow-up (52 weeks). Note that a line illustrates differences across the dose groups at a particular time point, rather than change over time for a particular dose.

Fig. 4

Responders: percentage of individuals attaining 50% pain improvement.