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Internal forces sustained by the vertebral artery during spinal manipulative therapy
Bruce P Symons1, Tim Leonard, Walter Herzog
1Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Canada.
Journal of Manipulative and Physiological Therapeutics
|October 17, 2002
Summary
Spinal manipulative therapy (SMT) applies minimal strain to the vertebral artery (VA), significantly below rupture levels. This study indicates SMT is unlikely to cause mechanical disruption of the VA.
Area of Science:
- Biomechanics
- Anatomy
- Orthopedics
Background:
- Spinal manipulative therapy (SMT) is effective for musculoskeletal disorders.
- Safety concerns exist regarding neck manipulation and vertebrobasilar stroke risk.
Purpose of the Study:
- Quantify vertebral artery (VA) strains during SMT.
- Assess the mechanical safety of SMT for the VA.
Main Methods:
- Cadaveric study using unembalmed specimens.
- Instrumented vertebral arteries with ultrasonographic crystals to measure strain.
- Compared strains during SMT, range of motion, and diagnostic tests.
- Determined mechanical failure points of the VA.
Main Results:
- SMT induced low strains (6.2% distal, 2.1% proximal VA loops).
- These strains were comparable to or less than those from diagnostic tests.
- VA mechanical failure occurred at strains 139%-162% of resting length.
Conclusions:
- SMT strains on the VA are significantly lower than those causing mechanical disruption.
- High-velocity, low-amplitude SMT is unlikely to mechanically disrupt the vertebral artery under normal conditions.