There is some (albeit not compelling) evidence to suggest that chiropractic spinal manipulation might be effective for treating non-specific back pain. But what about specific back pain, such as the one caused by a herniated disc? Some experts believe that, in patients suffering from such a condition, manipulations are contra-indicated (because the latter can cause the former), while others think that manipulation might be an effective treatment option (although the evidence is far from compelling). Who is correct? The issue can only be resolved with data from well-designed clinical investigations. A new trial might therefore enlighten us.
The stated purposes of this study were:
- to evaluate patients with low-back pain (LBP) and leg pain due to magnetic resonance imaging-confirmed disc herniation treated with high-velocity, low-amplitude spinal manipulation in terms of their short-, medium-, and long-term outcomes of self-reported global impression of change and pain levels
- to determine if outcomes differ between acute and chronic patients using.
The researchers conducted a ‘prospective cohort outcomes study‘ with 148 patients with LBP, leg pain, and physical examination abnormalities with concordant lumbar disc herniations. Baseline numerical rating scale (NRS) data for LBP, leg pain, and the Oswestry questionnaire were obtained. The specific lumbar spinal manipulation was dependent upon whether the disc herniation was intraforaminal or paramedian as seen on the magnetic resonance images and was performed by a chiropractor. Outcomes included the patient’s global impression of change scale for overall improvement, the NRS for LBP, leg pain, and the Oswestry questionnaire at 2 weeks, 1, 3, and 6 months, and 1 year. The proportion of patients reporting “improvement” on the patient’s global impression of change scale was calculated for all patients and for acute vs chronic patients. Pre-treatment and post-treatment NRS scores were compared using the paired t test. Baseline and follow-up Oswestry scores were compared using the Wilcoxon test. Numerical rating scale and Oswestry scores for acute vs chronic patients were compared using the unpaired t test for NRS scores and the Mann-Whitney U test for Oswestry scores.
Significant improvements for all outcomes at all time points were reported. At 3 months, 91% of patients were “improved”, and 88% were “improved” after 1 year. Acute patients improved faster by 3 months than did chronic patients. 81.8% of chronic patients 89.2% felt “improved” at 1 year. No adverse events were reported.
The researchers concluded that a large percentage of acute and importantly chronic lumbar disc herniation patients treated with chiropractic spinal manipulation reported clinically relevant improvement.
Does this new study meaningfully contribute to our knowledge about the effectiveness of chiropractic manipulation for back pain caused by herniated discs? The short answer to this question is NO.
A longer answer might be that the report does tell us something relevant about the quality of this research project. We know from countless studies that ~50% of patients experience adverse effects after spinal manipulations by a chiropractor. This means that any report claiming that NO ADVERSE EFFECTS WERE REPORTED is puzzling to a degree that we have to seriously question its quality or even honesty. In this context, it is relevant to mention that a recent review of the evidence concluded that a cause-effect relationship exists between the manipulative treatment and the development of disc herniation.
The positive outcomes reported in this new study could, of course, be due to a range of factors which are unrelated to the manipulations administered by the chiropractors:
- natural history of disc herniation
- regression towards the mean
- other treatments employed by the patients
- social desirability
To be able to say with any degree of certainty that the manipulations had anything to do with the observed positive outcomes would require an entirely different study-design. Should we assume that this is not known in the world of chiropractic? Or should we consider that chiropractors shy away from rigorous research because they fear its results?
The term prospective cohort outcomes study, seems to be a chiropractic invention (cohort studies are by definition prospective, and observational studies are usually prospective). It seems that, behind this long and impressive word, one can easily hide the fact that this study design fails to make the slightest attempt of controlling for non-specific effects; the term sounds scientific – but when we analyse what it means, we discover that this methodology is little more than a self-serving consumer survey. Most scientists would call such an investigation quite simply an OBSERVATIONAL STUDY.
I think it is time that chiropractors start doing proper research which actually does answer some of the many open questions regarding spinal manipulation.