Dose-Response for Chronic Low Back Pain: Long-Term Outcomes from a Randomized Controlled Trial

Background: Little is known about the number of sessions to optimize outcomes for the treatment of chronic low back pain. This is the first full-scale trial to evaluate the dose-response of spinal manipulation for any condition.

Methods: We randomized 400 patients with chronic low back pain to receive one of four dose levels of care: 0, 6, 12, or 18 sessions of lumbar spinal manipulation from a chiropractor. All participants were scheduled for three visits per week for six weeks at one of eight clinics. Care was rendered at each visit, either the index intervention or light massage to control attention and "hands on." The primary outcome was low back pain intensity. Secondary outcomes were functional disability, days with pain and functional disability, pain unpleasantness, global perceived improvement, fear-avoidance, and general health status. Outcomes were assessed at baseline and at 6, 12, 18, 24, 39, and 52 weeks. Linear and higher order dose effects will be evaluated using covariate-adjusted simultaneous regression; parametric dose-response curves will also be fitted. Efficacy will also be assessed by comparison of participants with 18 manipulation and 18 massage control treatments using covariate-adjusted simultaneous regression and generalized estimating equations.

Results: Adherence to all 18 treatment visits was 94%. Compliance with follow-up data collection was ≥ 86% at each endpoint to date. Outcomes will be analyzed after follow-up completion in June.

Conclusions: The first full-scale dose-response study of spinal manipulation has been successfully implemented. Outcomes up to 12 months will be reported.