Some chiropractors claim that their main intervention, spinal manipulation, works for nonspecific neck pain by improving inter-vertebral range of motion (IV-RoM). But IV-RoM is difficult to measure, and whether it is related to clinical outcomes seems uncertain. Researchers from the Institute of Musculoskeletal Research & Clinical Implementation and the Anglo-European College of Chiropractic have just published a study that might throw some light on this issue. According to its authors, it was aimed at answering the following research questions:
- Does cervical spine flexion and extension IV-RoM increase after a course of spinal manipulation?
- Is there a relationships between any IV-RoM increases and clinical outcomes?
- How does palpation compare with objective measurement in the detection of hypo-mobile segments?
Thirty patients with nonspecific neck pain and 30 healthy controls matched for age and gender received quantitative fluoroscopy (QF) screenings to measure flexion and extension IV-RoM (C1-C6) at baseline and 4-week follow-up. Patients received up to 12 neck manipulations and completed NRS, NDI and Euroqol 5D-5L at baseline, plus PGIC and satisfaction questionnaires at follow-up. IV-RoM accuracy, repeatability and hypo-mobility cut-offs were determined. Minimal detectable changes (MDC) over 4 weeks were calculated from controls. Patients and control IV-RoMs were compared at baseline as well as changes in patients over 4 weeks. Correlations between outcomes and the number of manipulations received and the agreement (Kappa) between palpated and QF-detected of hypo-mobile segments were calculated.
QF had high accuracy (worst RMS error 0.5σ) and repeatability (highest SEM 1.1σ, lowest ICC 0.9σ) for IV-RoM measurement. Hypo-mobility cut offs ranged from 0.8σ to 3.5σ. No outcome was significantly correlated with increased IV-RoM above MDC and there was no significant difference between the number of hypo-mobile segments in patients and controls at baseline or significant increases in IV-RoMs in patients. However, there was a modest and significant correlation between the number of manipulations received and the number of levels and directions whose IV-RoM increased beyond MDC (Rho=0.39, p=0.043). There was also no agreement between palpation and QF in identifying hypo-mobile segments (Kappa 0.04-0.06).
The authors concluded that this study found no differences in cervical sagittal IV-RoM between patients with non-specific neck pain and matched controls. There was a modest dose-response relationship between the number of manipulations given and number of levels increasing IV-RoM – providing evidence that neck manipulation has a mechanical effect at segmental levels. However, patient-reported outcomes were not related to this.
This conclusion seems a little odd to me. In my view the study suggests a clearly negative answer to all the three research questions formulated above. An interesting paragraph from the authors’ discussion section provides further insight: The lack of a relationship between symptomatic improvement and increased IV-RoM is also of interest. Clearly other mechanisms that improved the comfort and functional capacity of the patients in this study were in play, including spontaneous recovery. Other important biological factors may have included chemical factors in joint and muscle and activation patterns in the latter. However, this study seemed to rule out central pain hypersensitivity as a factor, as this was not detected at baseline in any of the patients. Psychological and social factors and their influence on functional behavior may also have had a role and may have been influenced by the interventions received.
So, spinal manipulation does not seem to work by improving IV-RoM. Could this be because spinal manipulation does not work at all?