Manipulation-induced hypoalgesia in musculoskeletal pain populations: a systematic critical review and meta-analysis

Abstract Background Manipulation-induced hypoalgesia (MIH) represents reduced pain sensitivity following joint manipulation, and has been documented in various populations. It is unknown, however, whether MIH following high-velocity low-amplitude spinal manipulative therapy is a specific and clinically relevant treatment effect. Methods This systematic critical review with meta-analysis investigated changes in quantitative sensory testing measures following high-velocity low-amplitude spinal manipulative therapy in musculoskeletal pain populations, in randomised controlled trials. Our objectives were to compare changes in quantitative sensory testing outcomes after spinal manipulative therapy vs. sham, control and active interventions, to estimate the magnitude of change over time, and to determine whether changes are systemic or not. Results Fifteen studies were included. Thirteen measured pressure pain threshold, and four of these were sham-controlled. Change in pressure pain threshold after spinal manipulative therapy compared to sham revealed no significant difference. Pressure pain threshold increased significantly over time after spinal manipulative therapy (0.32 kg/cm2, CI 0.22–0.42), which occurred systemically. There were too few studies comparing to other interventions or for other types of quantitative sensory testing to make robust conclusions about these. Conclusions We found that systemic MIH (for pressure pain threshold) does occur in musculoskeletal pain populations, though there was low quality evidence of no significant difference compared to sham manipulation. Future research should focus on the clinical relevance of MIH, and different types of quantitative sensory tests. Trial registration Prospectively registered with PROSPERO (registration CRD42016041963)

Waste not, want not: call to action for spinal manipulative therapy researchers

Abstract Background Research waste is defined as research outcomes with no or minimal societal benefits. It is a widespread problem in the healthcare field. Four primary sources of research waste have been defined: (1) irrelevant or low priority research questions, (2) poor design or methodology, (3) lack of publication, and (4) biased or inadequate reporting. This commentary, which was developed by a multidisciplinary group of researchers with spinal manipulative therapy (SMT) research expertise, discusses waste in SMT research and provides suggestions to improve future research. Main text This commentary examines common sources of waste in SMT research, focusing on design and methodological issues, by drawing on prior research and examples from clinical and mechanistic SMT studies. Clinical research is dominated by small studies and studies with a high risk of bias. This problem is compounded by systematic reviews that pool heterogenous data from varying populations, settings, and application of SMT. Research focusing on the mechanisms of SMT often fails to address the clinical relevance of mechanisms, relies on very short follow-up periods, and has inadequate control for contextual factors. Conclusions This call to action is directed to researchers in the field of SMT. It is critical that the SMT research community act to improve the way research is designed, conducted, and disseminated. We present specific key action points and resources, which should enhance the quality and usefulness of future SMT research