Vertebral arteries do not experience tensile force during manual cervical spine manipulation applied to human cadavers

Abstract

Background: The vertebral artery (VA) may be stretched and subsequently damaged during manual cervical spine manipulation. The objective of this study was to measure VA length changes that occur during cervical spine manipulation and to compare these to the VA failure length. Methods: Piezoelectric ultrasound crystals were implanted along the length of the VA (C1 to C7) and were used to measure length changes during cervical spine manipulation of seven un-embalmed, post-rigor human cadavers. Arteries were then excised, and elongation from arbitrary in-situ head/neck positions to first force (0.1 N) was measured. Following this, VA were stretched (8.33 mm/s) to mechanical failure. Failure was defined as the instance when VA elongation resulted in a decrease in force. Results: From arbitrary in-situ head/neck positions, the greatest average VA length change during spinal manipulation was [mean (range)] 5.1% (1.1 to 15.1%). From arbitrary in-situ head/neck positions, arteries were elongated on average 33.5% (4.6 to 84.6%) prior to first force occurrence and 51.3% (16.3 to 105.1%) to failure. Average failure forces were 3.4 N (1.4 to 9.7 N). Conclusions: Measured in arbitrary in-situ head/neck positions, VA were slack. It appears that this slack must be taken up prior to VA experiencing tensile force. During cervical spine manipulations (using cervical spine extension and rotation), arterial length changes remained below that slack length, suggesting that VA elongated but were not stretched during the manipulation. However, in order to answer the question if cervical spine manipulation is safe from a mechanical perspective, the testing performed here needs to be repeated using a defined in-situ head/neck position and take into consideration other structures (e.g. carotid arteries).

Reporting of adverse events associated with spinal manipulation in randomised clinical trials: an updated systematic review

“… 17 18 Furthermore, recent biomechanical studies report that head angular displacements and vertebral artery length changes are small during cervical spine manipulation thrusts 19 and that the vertebral artery does not experience longitudinal force during cervical spine manipulation. 20 Despite this literature, the serious nature of such events that are temporally associated with cervical spine manipulation makes it imperative that the circumstances surrounding such events are reported transparently.…”

“…Additionally, several large population-based studies have reported that there is no difference in risk of cervical artery dissection following visits to a chiropractor compared with those occurring following a visit to a primary care provider15 16 or, in those who received cervical spinal manipulation compared with matched controls 17 18. Furthermore, recent biomechanical studies report that head angular displacements and vertebral artery length changes are small during cervical spine manipulation thrusts19 and that the vertebral artery does not experience longitudinal force during cervical spine manipulation 20. Despite this literature, the serious nature of such events that are temporally associated with cervical spine manipulation makes it imperative that the circumstances surrounding such events are reported transparently.…”

Plausible Mechanisms of Causation of Immediate Stroke by Cervical Spine Manipulation: A Narrative Review

“…A 2023 study concluded that CSM exerts no stretch on the vertebral artery, it simply elongates it [ 53 ]. In this case, it may be that any neck movement that elongates the vertebral artery more than CSM is a more probable alternative explanation.…”

Cervical Spine Manipulation and Causation of Cervical Artery Dissection: A Review of 10 Case Reports

“…Research does not support a causal association between cervical spine manipulation (CSM) and CAD. CSM causes little or no strain on the cervical arteries [ 2 , 3 ]. In a statement from the American Heart Association and American Stroke Association, Biller et al [ 4 ] found that biomechanical evidence is insufficient to establish the claim that CSM causes CAD and recommended that practitioners should strongly consider CAD as a presenting symptom prior to CSM.…”