Vertebral arteries do not experience tensile force during manual cervical spine manipulation applied to human cadavers
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).
Keywords: Spinal biomechanics; cerebrovascular accidents; spinal manipulation; stroke; vertebral artery dissection.
Les auteurs : Lindsay M Gorrell, Andrew Sawatsky, W Brent Edwards, Walter Herzog
Commentaire Gepro :
Cette étude mesure les modifications de la longueur de l'artère vertébrale lors de la manipulation du rachis cervical. La comparaison est faite avec la longueur d'échec de l'artère vertébrale.
L'étude rapporte que des cristaux ultrasonores piézoélectriques ont été placés au sein de l'artère vertébrale sur les étages allant de C7 à D1 sur des cadavres post-rigor et non embaumés. Un étalonnage a été pratiqué pour déterminer le longueur d'échec c'est à dire le cas ou l'étirement de l'artère vertébrale a entrainé une diminution de la force.
L'étude a démontré que les changements de longueur artérielle restaient inférieurs à cette longueur d'échec ce qui permet de dire que l'artère vertébrale n'est pas étirée malgré son allongement lors de la manipulation.
Les résultats de l'étude nous confortent sur les enseignements de la manipulation structurelle articulaire selon la méthode Gepro. En effet, les manipulations structurelles selon la méthode GEPRO s'effectuent dans le respect de la physiologie en utilisant des techniques directes et sans bras de levier. Tel que décrit dans cet articles les manoeuvres n'entrainent pas d'étirement des l'artère vertébrale. Les manipulations structurelles articulaires sont enseignées selon la méthode GEPRO sur les cervicales de C2 à C7.