Mechanical vs manual manipulation for low back pain: an observational cohort study

This is an observational prospective cohort study to explore the treatment effect of mechanical vs manual manipulation for acute low back pain.

Ninety-two patients with a history of acute low back pain were recruited from 3 private chiropractic offices, 2 of which used manual lumbar manipulation and 1 used mechanical instrument manipulation (Activator) as their primary modes of treatment. The chiropractors used their "treatment-as-usual" protocols for a maximum of 8 visits or 4 weeks, whichever occurred first. Primary outcome measures were changes in Numeric Pain Rating Scale (NPRS) and Oswestry Disability Index (ODI) scores from baseline to 4 weeks. The linear regression models were adjusted for baseline NPRS and ODI scores, age, and treatment expectancy.

Comparison of baseline characteristics did not show any significant differences between the groups except for age (38.4 vs 49.7 years, P < .001) and treatment expectancy (5.7 vs 6.3, P = .003). Linear regression revealed significantly lower NPRS scores in the manual manipulation group at 4 weeks (beta = -1.2; 95% confidence interval, -2.1 to -.28) but no significant difference in ODI scores between the 2 groups at 4 weeks (beta = 1.5; 95% confidence interval, -8.3 to 2.4). Treatment expectancy, but not age, was found to have a significant main effect on both NPRS and ODI scores at 4 weeks. Exploratory analysis of the clinical patterns of care between the clinicians revealed significant differences in treatment frequency, duration, modality, and radiograph use between the 2 cohorts.

This study highlights the challenges inherent with conducting research that allows for "treatment as usual." The data and experience derived from this investigational study will be used to design a future randomized clinical trial in which tighter controls will be imposed on the treatment protocol.