Assessing the effect of sample size, methodological quality and statistical rigour on outcomes of randomised controlled trials on mobilisation, manipulation and massage for low back pain of at least 6 weeks duration

ObjectivesTo assess the effect of sample size, methodological quality and statistical rigour on outcomes of randomised controlled trials (RCTs) on manual therapy (i.e. manipulation, mobilisation and/or massage) for non-specific low back pain (LBP) of at least 6 weeks duration, and to report results from RCTs with adequate sample size, methodological quality and statistical rigour.Data sourcesMedLine, EMBASE, CINAHL, AMED, Cochrane, PEDro and the library collection of the Chartered Society of Physiotherapy.Review methodsRCTs were identified that compared manual therapy with a control or alternative intervention in adults with non-specific LBP of at least 6 weeks duration. The sample size, methodological quality (adapted 10-point van Tulder scale) and statistical rigour were then assessed. RCTs were regarded as higher quality if they fulfilled the following three criteria: (a) >40 subjects in the manual therapy group; (b) scoring >5/10 on the Van Tulder scale; and (c) reporting statistical tests that compared the change in the intervention group with the change in the control group.ResultsTen RCTs were included in the review but only two qualified as higher quality RCTs. Results from smaller trials and lower quality RCTs showed more variation in differences between the intervention and control groups than larger or higher quality trials. Evidence from large, high-quality RCTs with adequate statistical analyses showed that, for improvement in pain and function, a mobilisation/manipulation package is an effective intervention [compared with general practitioner (GP) care], whilst manipulation used in isolation showed no real benefits over sham manipulation or an alternative intervention. No higher quality evidence considering massage was identified.ConclusionsMany RCTs in the area of manual therapy for LBP have shortcomings in sample size, methodological quality and/or statistical rigour, but there remains evidence from higher quality RCTs to support the use of a manual therapy package, compared with GP care, for non-specific LBP of at least 6 weeks duration.