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Published on: September 21, 2017
Effect of rotated head posture on dynamic vertebral artery elongation during simulated rear impact
Paul C Ivancic1, Shigeki Ito, Yasuhiro Tominaga
1Biomechanics Research Laboratory, Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, 333 Cedar St., P.O. Box 208071, New Haven, CT 06520-8071, USA.
Background:
Elongation-induced vertebral artery injury has been hypothesized to occur during non-physiological coupled axial rotation and extension of head. No studies have quantified dynamic vertebral artery elongation during head-turned rear impacts. Therefore, we evaluated effect of rotated head posture vs. forward head posture at the time of impact on dynamic vertebral artery elongation during simulated rear impacts.
Methods:
A whole cervical spine model with surrogate head and muscle force replication underwent either simulated head-turned (n = 6) or head-forward (n = 6) rear impacts of 3.5, 5, 6.5 and 8 g. Continuous dynamic vertebral artery elongation was recorded using custom transducer and compared to physiological values obtained during intact flexibility testing.
Findings:
Average (SD) peak dynamic vertebral artery elongation of up to 30.5 (2.6) mm during head-turned rear-impact significantly exceeded (P < 0.05) the physiological beginning at 5 g. Highest peak elongation of 5.8 (2.1) mm during head-forward rear impact did not exceed physiological limit. Head-turned rear impact caused earlier occurrence of average peak vertebral artery elongation, 84.5 (4.2) ms vs. 161.0 (43.8) ms, and higher average peak vertebral artery elongation rate, 1336.7 (74.5) mm/s vs. 211.5 (97.4) mm/s, as compared to head-forward rear impact.
Interpretation:
Elongation-induced vertebral artery injury is more likely to occur in those with rotated head posture at the time of rear impact, as compared to head-forward.
