METHODS: 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.
RESULTS: 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.
CONCLUSIONS: 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.
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