A study of cervical spine kinematics and joint capsule strain in rear impacts using a human FE model

Kitagawa, Yuichi<sup>1</sup>; Yasuki, Tsuyoshi<sup>1</sup>; Hasegawa, Junji<sup>1</sup>

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Abstract and keywords

Many efforts have been made to understand the mechanism of whiplash injury. Recently, the cervical facet joint capsules have been focused on as a potential site of injury. An experimental approach has been taken to analyze the vertebral motion and to estimate joint capsule stretch that was thought to be a potential cause of pain. The purpose of this study is to analyze the kinematics of the cervical facet joint using a human FE model in order to better understand the injury mechanism. The Total Human Model for Safety (THUMS) was used to visually analyze the local and global kinematics of the spine. Soft tissues in the neck were newly modeled and introduced into THUMS for estimating the loading level in rear impacts. The model was first validated against human test data in the literature by comparing vertebrae motion as well as head and neck responses. Joint capsule strain was estimated from a maximum principal strain output from the elements representing the capsule tissues. A rear-end collision was then simulated using THUMS and a prototype seat model, assuming a delta-V of 25 km/h. The trajectory of the vertebrae was analyzed in a local coordinate system defined along the joint surface. Strain growth in the joint capsules was explained, as related to contact events between the occupant and the seat. A new seat concept was proposed to help lessen the loading level to the neck soft tissues. The foam material of the seat back was softened, the initial gap behind the head was reduced and the head restraint was stiffened for firm support. The lower seat back frame was also reinforced to withstand the impact severity at the given delta-V. Another rear impact simulation was conducted using the new seat concept model to examine the effectiveness of the new concept. The joint capsule strain was found to be relatively lower with the new seat concept. The study also discusses the influence of seat parameters to the vertebral motion and the resultant strain in the joint capsules. The meaning of the contact timing of the head to the head restraint was examined based on the results in terms of correlation with injury indicators such as NIC and the joint capsule strain.

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PubMed: 17311176

SAE: 2006-22-0020

Cited By (10)

Year	Entry
2007	Kitagawa Y, Yasuki T, Hasegawa J. Consideration of possible indicators for whiplash injury assessment and examination of seat design parameters using human FE model. In: Proceedings of the 20th International Technical Conference on the Enhanced Safety of Vehicles (ESV). June 18-21, 2007; Lyon, France.
2009	Shigeta K, Kitagawa Y, Yasuki T. Development of next generation human FE model capable of organ injury prediction. In: Proceedings of the 21st International Technical Conference on the Enhanced Safety of Vehicles (ESV). June 15-18, 2009; Stuttgart, Germany.
2008	Kitagawa Y, Yasuki T, Hasegawa J. Research study on whiplash injury lessening with active head restraint using human body fe model. In: Proceedings of the 2008 International IRCOBI Conference on the Biomechanics of Impact. September 17-19, 2008; Bern, Switzerland.381-396.
2010	Ghajari M, Peldschus S, Galvanetto U, Asgharpourb Z, Iannucci L. Influence of the body on head rotational acceleration in motorcycle helmet oblique impact tests. In: Proceedings of the 2010 International IRCOBI Conference on the Biomechanics of Impact. September 15-17, 2010; Hannover, Germany.95-106.
2010	Sato F, Antona J, Ejima S, Ono K. Influence on cervical vertebral motion of the interaction between occiput and head restraint/seat based on the reconstruction of rear-end collision using finite element human model. In: Proceedings of the 2010 International IRCOBI Conference on the Biomechanics of Impact. September 15-17, 2010; Hannover, Germany.41-58.
2017	Arun MWJ, Hadagali P, Driesslein K, Curry W, Yoganandan N, Pintar FA. Biomechanics of lumbar motion-segments in dynamic compression. Stapp Car Crash J. November 2017;61:1-25. SAE 2017-22-0001.
2011	Jaumard NV, Welch WC, Winkelstein BA. Spinal facet joint biomechanics and mechanotransduction in normal, injury and degenerative conditions. J Biomech Eng. July 2011;133(7):071010.
2014	Huang H. Biomechanics of Coupled Motion in the Cervical Spine During Simulated Whiplash in Patients With Pre-Existing Cervical or Lumbar Spinal Fusion: A Finite Element Study [Master's thesis]. Duke University; 2014.
2010	Fice JB. Numerical Modeling of Whiplash Injury [Master's thesis]. University of Waterloo; 2010.
2020	Fabre MAC. Development of Elderly Posture Male and Female Finite Element Neck Models and Assessment of Tissue-Level Response Under Impact Loading [Master's thesis]. University of Waterloo; 2020.