The concept that manual therapy outcomes are best when the treatment is aimed at a specific and relevant joint is assumed and commonplace in education and clinical practice. But what’s the evidence for this?
Manual therapy is considered a highly skilled procedure both in terms of assessment for treatment site, as well as treatment application. Much attention is given to learning to determine the level, side and thrust-style of a technique, as this is considered important for clinical outcomes. But what is the evidence for this approach? Does it matter where you apply a manual therapy technique, does it really make a clinical difference?
To answer this question a new systematic review, published in Nature, compared spine-related outcomes when SMT was applied at a candidate site presumed to be clinically relevant vs. when SMT was applied at any other spinal location.
Summary of Methods
Firstly it’s important to define what spinal manual therapy (SMT) means in the context of this systematic review. The authors decided to use this term to describe high velocity, low amplitude force which can be applied manually or via an instrument. This means mainland’s or non-thrust techniques were not included within the review.
From a methodology perspective the systematic review was preregistered in PROSPERO and adhered to the PRISMA guidelines. Four databases were searched (PubMed, Embased, CINAHL and Index to Chiropractic Literature) using a search strategy which contained terms relating to spinal pain, SMT applied at candidate sites, and non-candidate SMT sites. The search strategy is available in full.
The ‘application site’ is where the treating clinicians attempted to apply SMT. In this systematic review this is defined as the site determined to be relevant for clinical outcomes. The authors compared SMT sites to three types of non-candidate SMT sites:
- contralateral side at same level
- elsewhere in the same spinal region
- a distant / remote spinal region
Articles were eligible for inclusion if they were RCT designs involving humans with spinal pain in any region of any duration comparing spinal manual therapy to any candidate site compared to any non-candidate site, where the between-group effect sizes were reported or estimable.
Risk of bias was assessed using the Cochrane Risk of Bias tool and quality of included studies was evaluated using a custom tool. More details are available in the full text of the article.
In total ten studies (944 participants) were included within the review all published in English between 2003 and 2010. Six of these studies included cervical pain and four involved lumbar pain with half of all studies involving patients with chronic pain. The number of SMT sessions ranged from 1-10 with the average being 2.1.
In terms of risk of bias one study had high risk of bias, four moderate risk of bias and five had low risk of bias. Overall the authors summarised the evidence as credible based on risk of bias and quality.
Only a single study demonstrated statistical significance in favour of SMT applied at the candidate site compared to a non-candidate SMT site. All other studies demonstrated no difference in outcome when SMT was applied to a site in the same region or distant to the site targeted by the clinician.
In essence spinal manual therapy applied by a clinician at a clinician-determined, ‘correct’ vertebral level did not have better outcomes than treatment applied less accurately or ‘haphazardly’. The outcomes include pain and disability as well as others.
The study which was showed ‘correct’ application of SMT was more effective was the only study rated as having a ‘high’ risk of bias and although met statistical significance is unlikely to have reached clinical significance.
The authors of the systematic review propose a number of explanations for their findings that they were unable to find any measurable difference in clinical outcomes based on whether SMT was applied at a vertebral level based on clinical assessment or not.
Firstly, it’s possible that the candidate site is a subjective concept as, although there are numerous way of assessing or detecting the correct site for manual therapy, a recent systematic review demonstrated assessments to be unreliable. It’s possible that clinically relevant candidate sites exist but clinicians are unable to find them using the assessment techniques available to them.
Secondly, as the authors explain, manipulation is non-specific which means there is no need to be exact when applying a treatment to a candidate site. After all studies have demonstrated that manual therapy affects multiple vertebral joints both in proximity and further away from the target joint / vertebrae. Furthermore it is possible that the therapeutic effects of manual therapy may be unrelated to treatment specificity but be down to systemic or generalised interactions.
The authors propose a third explanation which is that contextual, or patient specific factors, might explain the positive effects of manual therapy in the clinical setting. Patient experience, expectations and therapeutic alliance have all been shown to improve patient symptoms. It’s important to remember this effect is also found in other physiotherapy treatment such as electrotherapy and exercise.
It is also important to note that the findings of this systematic review, and all manual therapy research, is not profession specific and applies to all healthcare professionals using manual therapy. Also bear in mind that this is not to say there isn’t a place for manual therapy in clinical practice rather treatment and education should reflect the benefit of “non-specific” manual therapy rather than site specific treatment.