Rapid response to a systematic review on spinal manipulative therapy for chronic low back pain

A systematic review (1) on the benefits and harms of spinal manipulative therapy (SMT) for chronic low back pain (CLBP) was published in the British Medical Journal in March 2019. The review authors concluded that SMT has similar effects to ‘recommended’ therapies for pain intensity, and a clinically better effect for function over recommended therapies, ‘non-recommended’ therapies and sham therapy at short-term follow-up.

Dr Neil O’Connell and I submitted a rapid response. In this we outlined a number of reasons why the review interpretations and conclusions may not be valid. Below is a copy of our response.

“The only reliable way of assessing the efficacy of SMT is to compare it with sham treatment. In their analyses, there was low to very low certainty evidence based upon up to eight trials and 831 participants that SMT did not improve pain more than sham treatment at any time point and provided a small benefit for function at one month only. Examination of the forest plot for function at one month indicates considerable statistical heterogeneity (I2=91%) explained by a single extreme outlier which reported a likely implausible lack of improvement over time in the sham SMT group (2). Removal of that outlier results in an effect substantially lower than their threshold for a clinically important benefit (SMD -0.27 (95% CI -0.52 to -0.02), I2=39%). In fact, five of the remaining six trials failed to report a benefit for function at this time point. The lack of an important benefit in trials with a host of biases likely to favor SMT indicates that higher quality evidence would be extremely unlikely to overturn a conclusion that SMT confers no benefits over sham therapy.

It is also difficult to interpret the comparisons of SMT with ‘recommended’ and ‘non-recommended’ therapies as these comparisons combine a variety of control groups that may not yield similar outcomes. For example, multimodal packages of care, exercise interventions, back school, minimal medical care, and a pain clinic were all included in the ‘recommended’ therapies comparison. The categorization of therapies as ‘recommended’ or ‘non-recommended’ therapy is also sometimes questionable. For example, inert (e.g. detuned ultrasound) and no treatment controls were both categorized as ‘non-recommended’ therapies. While these are clearly not recommended, it seems unreasonable to pool them with non-recommended therapies offered in good faith. On the other hand, a minimal medical care control comprised mainly of provision of paracetamol (3), a treatment that is no longer recommended by the clinical guidelines cited, was categorized as a ‘recommended’ therapy.

Some included trials also provide no reliable estimation of the effectiveness of SMT. For example, one study compared a package of chiropractic care which included stretching, dry needling, ischemic compression, soft tissue massage and home exercise in addition to SMT, and this was compared to a variety of approaches which included gabapentin, facet joint injection, soft-tissue injections and transcutaneous electrical nerve stimulation (TENS) (4).

A further issue is that the authors do not seem to interpret their results in line with their own thresholds for determining clinical effectiveness. The point estimates for almost all comparisons failed to meet their pre-defined thresholds for clinical importance. In the single comparison where the point estimate exceeded this threshold, the lower limit of the 95% confidence intervals fell well outside it. That SMT fails to cross this low bar in open-label trials at risk of various other biases, might be interpreted as evidence of ineffectiveness.

Finally, the assessment of the certainty in evidence and strength of recommendations for SMT overstates the degree of certainty. A body of evidence for a given comparison was only downgraded for the criterion “limitations of studies” where >50% of participants came from studies at risk of both allocation and performance bias. This is lenient since either one of these sources of bias alone represents a meaningful limitation.

In conclusion, these results demonstrate no convincing evidence for the superiority of SMT over sham SMT, and a lack of clinically important benefit of SMT when compared with any other treatment. The lack of a benefit of SMT over sham therapy indicates that SMT is unlikely to have any direct benefits and observed improvements are the result of contextual and other effects. It is likely that the apparent equivalence with both ‘recommended’ and ‘non-recommended’ therapies tells us more about the disappointing effectiveness of those approaches than it does about the benefit of SMT.”

Authors of Rapid Response:

Mary O’Keeffe, Institute for Musculoskeletal Health, Sydney, Australia, New South Wales.

Neil E O’Connell, Health Economics Research Group, Department of Clinical Sciences, Institute of Environment, Health and Societies, Brunel University London, Uxbridge, UK