Do adverse events after manual therapy for back and/or neck pain have an impact on the chance to recover? A cohort study

BACKGROUND: Manual therapy is a commonly used treatment for patients with back and neck pain. Studies have shown that manual therapy-related adverse events are mainly short in duration and mild or moderate by their intensity, affecting up to 50% of the patients. If the presence of adverse events has an impact on the chance to recover from back/neck pain is poorly understood. The aim of this study was to investigate if mild or moderate adverse events after manual therapy has an impact on the chance to recover from back/neck pain in men and women. METHODS: A prospective cohort study of 771 patients with at least three treatment sessions in a randomized controlled trial performed in January 2010 – December 2013. Adverse events within 24 h after each treatment were measured with questionnaires and categorized as: no, mild or moderate, based on bothersomeness. Outcome measure was the perceived recovery at seven weeks and at three months follow-up. Odds Ratios (OR) and 95% confidence intervals (CI) were calculated by Logistic regression to investigate the associations between the exposure and outcome, and to test and adjust for potential confounding. RESULTS: There were no statistically significant associations observed between the experience of mild or moderate adverse events and being recovered at the seven weeks follow-up. The only statistically significant association observed at the three months follow-up was for mild adverse events in men with an OR of 2.44, 95% CI: 1.24–4.80 in comparison to men with no adverse events. CONCLUSION: This study indicates that mild adverse events after manual therapy may be related to a better chance to recover in men. TRIAL REGISTRATION: The study is based on data from a trial registered in Current Controlled Trials (ISRCTN92249294).