Vertebral artery flow and cervical manipulation: An experimental study☆

Background: Spinal manipulation therapy is used by millions of patients each year to relieve symptoms caused by biomechanical dysfunction of the spine. Cerebrovascular accidents in the posterior cerebral circulation are a feared complication, but little research has been done on vertebral artery hemodynamics during cervical manipulation. Objective: The purpose of this study was to develop an experimental model for investigations of volume blood flow changes in the vertebral arteries during premanipulative testing of these vessels and during spinal manipulation therapy of the cervical spine. Design and Setting: An experimental study in a university biomedical laboratory. Material and Methods: The vertebral arteries were exposed in 8 adult pigs after extensive mediastinal dissection. Volume blood flow was measured on both sides simultaneously by advanced transit-time flowmetry. Results: After cervical manipulation, the vertebral artery volume blood flow increased significantly for 40 seconds before returning to baseline values in less than 3 minutes. We found no significant changes in volume blood flow during premanipulative testing of the vertebral arteries (DeKleyn's test). Conclusion: We present an experimental model for investigations of vertebral artery hemodynamics during biomechanical interventions. We found a modest and transient effect of cervical manipulation on vertebral artery volume flow. The model may have further applications in future biomechanical research, for example, to determine whether any of several spinal manipulative techniques imposes less strain on the vertebral artery, thereby reducing possible future cerebrovascular accidents after such treatment. (J Manipulative Physiol Ther 1999; 22:431–5)