STRAIN in vertebral artery during passive cervical range of motion and spinal manipulation therapy: A systematic review and meta-analysis.

Abstract

To identify and synthesize studies examining the strain on the vertebral artery (VA) during cervical spinal manipulation therapy (cSMT). Additionally, we compared VA strains induced by cSMT with passive range of motion (ROM) across different cervical spine levels and VA segments. A systematic review and meta-analysis were conducted following PRISMA guidelines and registered with PROSPERO (CRD42024591457). The search was performed in May 2025 across SCOPUS, PubMed, MEDLINE, Web of Science, LILACS, SciELO, and the Index to Chiropractic Literature. Studies that focused on VA strain during cSMT and passive ROM. Risk of bias was assessed using the Anatomical Quality Assessment (AQUA) Tool. Data extraction included descriptive, methodological, VA strain, and interventional details. Meta-analysis was performed for studies comparing VA strain between cSMT and ROM. ix studies met the inclusion criteria, with four providing data for meta-analysis. cSMT consistently produced lower VA strain (up to 3.8 %) compared to passive ROM (up to 12.5 %) in the V3 segment (C0-C2). Meta-analysis revealed greater strain during ROM compared to cSMT, particularly during rotation (standardized mean difference [SMD] = 1.05). This systematic review and meta-analysis provide consistent evidence that cSMT induces less strain on the VA, particularly within the V3 segment, compared to passive cervical ROM. Although the evidence comes from studies conducted in human cadaveric specimens, the robustness of the methodologies and the consistency of findings across studies contribute to the growing body of biomechanical evidence supporting the relative safety of cSMT with respect to VA strain.