The effect of spinal manipulation on the efficacy of a rehabilitation protocol for patients with chronic neck pain : a pilot study

This pilot study sought to (1) determine whether a 4-week period of chiropractic care improved the ability of chronic neck pain patients to respond to an 8-week period of exercise rehabilitation and (2) determine effect sizes to use in sample size calculations for future studies. Twenty male and female participants (age, 43 ± 12 years; body mass index, 27 ± 4.5 [mean ± SD]) with chronic nonspecific neck pain were randomized into either a chiropractic care combined with exercise or an exercise only group. Group 1 received 4 weeks of chiropractic care, and group 2 waited 4 weeks before both groups participated in an 8-week exercise intervention. The following outcome measures were assessed in week 1 (baseline), week 4, and at week 12: Neck Disability Index (NDI); Visual Analogue Scale (VAS), both now and worst; neck flexion-relaxation response; and feed-forward activation (FFA) times. A repeated-measures analysis of variance was used to evaluate the changes in the NDI and VAS over time. Effect sizes were calculated for changes in neuromuscular parameters. There were significant decreases in the NDI score (P b .001) and VAS in (P b .005) in both groups with no significant differences between the groups. Effect sizes (ESs) were as follows: NDI (.293); VAS now (.175); VAS worst (.392); flexion-relaxation (.636); FFA times: sternocleidomastoid (.1321), anterior scalene (.195). This lead to sample size estimates as follows: flexion-relaxation response, 64 subjects per group; NDI, 145 subjects per group; VAS, 166 subjects per group. Chiropractic care combined with exercise and exercise alone are both effective at reducing functional disability and pain in chronic nonspecific neck pain patients. Future studies will need at least 64 subjects per group to determine if there are differences between the groups and if these differences are attributable to changes in neuromuscular measures.