Spinal manipulative therapy (SMT) or “adjustment” is a widely practiced intervention by chiropractors, osteopaths, and physiotherapists for acute and chronic low-back pain. An updated review of the research on SMT for short-term or acute low-back pain suggests it is no more effective than other therapy options. However, as much as anything, the indecisive research outcomes attest to the lack of high quality evidence in this area of pain management.
As an update to their earlier Cochrane Systematic Review and Meta-Analysis of this topic, Sidney M Rubinstein, DC, MSc and colleagues in The Netherlands conducted an extensive search of all literature on the effects of SMT for acute low-back pain [Rubinstein et al. 2012]. Acute low-back pain was defined a <6 weeks duration, and excluded pain caused by a known underlying condition, such as infection, tumor, or fracture. Patients whose pain was predominantly in the lower back but may also have radiated into the buttocks and legs were included.
The Review focused exclusively on randomized controlled trials (RCTs) in which SMT was defined as any hands-on therapy directed towards the spine, whether manipulation and mobilization, and including studies from chiropractors, manual therapists, and osteopaths. Comparison therapies were combined into the following 5 main clusters:
- SMT versus sham/placebo SMT (ie, ostensibly indistinguishable by the patient from the true technique);
- SMT versus “inert” interventions (eg, detuned diathermy or ultrasound);
- SMT versus “active” therapeutic interventions (eg, back school, exercise, physiotherapy);
- SMT plus any intervention versus that same intervention alone (ie, SMT as an adjunctive therapy);
- SMT versus another SMT technique (eg, side-lying thrust SMT versus non-thrust side-lying technique, supine thrust SMT versus side-lying thrust SMT).
Only patient-reported outcome measures were evaluated, and the primary endpoints of interest for analysis were back pain, back-pain specific functional status, and perceived recovery. Secondary outcomes were return-to-work and quality of life.
The researchers identified 20 qualifying RCTs (total participants N = 2,674), 12 (60%) of which were not included in the authors’ previous Cochrane Review. Study sample sizes ranged from 36 to 323 (median N [Interquartile Range] = 108 [61 to 189]). In total, only 6 trials (30% of all included studies) were of higher quality (ie, low risk of bias) and, at most, 3 RCTs could be identified per comparison, outcome, and time interval. Therefore, the researchers note that the amount of available data for each analysis was not robust. The following results were determined:
- Overall, for the primary outcomes, there was low to very low quality evidence suggesting no difference in effect for SMT when compared with inert interventions, sham SMT, or when added to another intervention.
- There was a varying quality of evidence (from very low to moderate) suggesting no difference in effect for SMT when compared with active interventions.
- In general, there were only minor or nonsignificant differences identified between various SMT thrust techniques for any outcome or time interval.
- There was no evidence of serious adverse events demonstrated in any of the reported trials.
Based on the preponderance of evidence from the available trials, the authors conclude that SMT is no more effective in patients with acute low-back pain than inert interventions, sham SMT, or when added to another intervention. SMT also appears to be no better than other commonly recommended active therapies. Therefore, the decision to refer patients for SMT, such as chiropractic care, could be based on costs, preferences of patients and providers, and relative safety of SMT compared with other treatment options.
COMMENTARY: The results of this current Cochrane Review focusing on acute low-back pain are comparable to those of an earlier analysis from this same group of authors investigating SMT for chronic low-back conditions [see UPDATE here]. In that Review they concluded that the limited high quality evidence available suggests that for low-back pain of >12 weeks duration there is no clinically relevant superiority of SMT compared with other common and generally effective interventions for reducing back pain and improving function.
In this present Review by Rubinstein and colleagues , while SMT therapies were not more favorable than other treatments known to be effective — such as exercise or physiotherapy — the authors express some surprise that SMT therapies also were not more favorable compared with sham/placebo approaches or interventions known to be inert. They concede that these unexpected results might be explained by the low quantity and poor quality of available evidence. In fact, a number of factors may be unknown, uncontrolled, and/or confounding in the research on SMT to date, such as:
- In a majority of cases, trial sizes are too small (inadequate power) to reliably detect significant differences between groups.
- Trials often include heterogenous (widely differing) patient populations and in different cultures.
- Back pain conditions being treated may have a diversity of etiologies, even when all are nonspecific.
- The natural course of back pain, with peaks and valleys over time and spontaneous remission in a great number of cases, may distort assessments of treatment efficacy.
- Variable approaches to SMT, such as differing manipulative techniques, as well as the frequency and duration of treatment sessions may alter outcomes in different trials.
- Individual skills and even the personalities of practitioners participating in trials may affect outcomes.
- Blinding of practitioners in SMT trials is impossible and, in most cases, subjects cannot be blinded to treatment condition, all of which could bias outcomes.
- In many of the studies, baseline pain and functional status are, on average, at moderate levels; hence, there can be a “floor effect” — that is, too little latitude for statistically or clinically significant improvement.
- Individual patient preferences for treatment, with some favoring “hands-on” therapies while others prefer less active interventions, may affect therapeutic response.
- There is always a question of whether sham/placebo treatments are actually inert and, if not so, this could greatly diminish effect sizes in comparison trials.
All of these factors, and others, might affect patient responses to treatment and/or distort outcomes. Additionally, Rubinstein et al. acknowledge that their meta-analysis was extremely limited (ie, hampered) by the small number of studies per comparison, outcome, and time interval. Therefore, they concede that it is difficult to reach valid conclusions or make strong recommendations regarding the use of SMT for acute low-back pain.
At the same time, many people with back pain claim that SMT, particularly chiropractic, has helped them. This might be influenced by patient preferences combined with the skills of the particular practitioners consulted and the possibility that SMT may be advantageous therapy for specific subgroups of patients that have not been adequately delineated in the research. In this current Cochrane Review, SMT appeared to be as safe for the treatment of acute low-back pain as other treatment options and, from limited data, the authors found that cost differences over one year — comparing SMT with general practitioner care or an exercise program — are relatively modest.
REFERENCE: Rubinstein SM, Terwee CB, Assendelft WJJ, et al. Spinal manipulative therapy for acute low-back pain. Cochrane Database of Systematic Reviews. 2012;9(CD008880) [abstract here].
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