Common treatments for neck pain include manual therapy interventions such as spinal manipulation and stretching. As approximately 50% of cervical rotation occurs at the atlantoaxial joint, it has been suggested that there is the possibility of a reduction of vertebral artery blood flow during cervical spine manipulation or other manual therapy procedures. The possible mechanism contributing to this includes stretching of the contralateral vertebral artery and compression of the ipsilateral vertebral artery over the bony landmarks in the region.
In the current literature, some studies have found a decrease in blood flow velocity in the contralateral vertebral artery associated with cervical spine rotation, while other studies have suggested that the natural tortuous path of the vertebral artery prevents these distortions from occurring. Furthermore, it has been reported that the vertebral artery strain during spinal manipulation is lower than the strain induced during range of motion (ROM) testing, thereby decreasing the likelihood of a disruption of the vertebral artery during spinal manipulation. One limitation of the current literature is that studies completed to date have mostly examined healthy participants, not taking into account individuals with upper cervical spinal restrictions, or even neck pain (the very patients we see in practice!). These restrictions may further reduce the potential for compression or stretching forces of the vertebral artery due to a reduction in the available range of motion.
Static stretching is another common treatment approach used for neck pain that has shown beneficial clinical results. It has been suggested that sustained end-range cervical rotation for 60 seconds or longer should be avoided, in order to help prevent any potential compromise of the vertebral artery. Similar to spinal manipulation, studies using pulsed-wave Doppler sonography have produced contradicting results, with some studies showing significant reduction in the contralateral vertebral artery blood flow, while others found no significant reduction during these maneuvers. A main limitation in the current literature includes that studies assessing the duration of stretching and its impact on blood hemodynamics has not been assessed.
The aim of this Research Review is to briefly summarize three studies investigating the hemodynamics of the vertebral arteries during manual therapy set-ups. The purpose of the first study by Leenaerts et al. was to measure changes in blood flow velocity and volume flow rate in the contralateral vertebral artery during end-range rotation and pre-manipulative hold, and to compare these measurements between participants with and without C1-2 range of motion restriction. The purpose of the second study by Yelverton et al. was to examine the blood flow through the vertebral arteries during different rotary head positions and post-cervical spinal manipulation. The aim of the third study by Mahmoud et al. was to investigate the effect of sustained end-range cervical rotation using 3 different time durations. Their collective results add to our knowledge in this area…enjoy!
THIS WEEK'S RESEARCH REVIEW: “Vertebral Artery Blood Flow & Chiropractic Procedures – Literature Updates”
These three papers were published in JMPT (2020) and this Review is posted in Recent Reviews, Spinal Manipulation - Safety & Adverse Events and the 2021 Archive.
vertebral artery