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Alar, Transverse, and Apical Ligament Strain due to Head-Turned Rear Impact

Maak, Travis G., BS; Tominaga, Yasuhiro, MD, PhD; Panjabi, Manohar M., PhD; Ivancic, Paul C., MPhil

doi: 10.1097/01.brs.0000202739.05878.d3

Study Design. Determination of alar, transverse, and apical ligament strains during simulated head-turned rear impact.

Objectives. To quantify the alar, transverse, and apical ligament strains during head-turned rear impacts of increasing severity, to compare peak strains with baseline values, and to investigate injury mechanisms.

Summary of Background Data. Clinical and epidemiologic studies have documented upper cervical spine ligament injury due to severe whiplash trauma. There are no previous biomechanical studies investigating injury mechanisms during head-turned rear impacts.

Methods. Whole cervical spine specimens (C0–T1) with surrogate head and muscle force replication were used to simulate head-turned rear impacts of 3.5, 5, 6.5, and 8 g horizontal accelerations of the T1 vertebra. The peak ligament strains during impact were compared (P < 0.05) to baseline values, obtained during a noninjurious 2 g acceleration.

Results. The highest right and left alar ligament average peak strains were 41.1% and 40.8%, respectively. The highest transverse and apical ligament average strain peaks were 17% and 21.3%, respectively. There were no significant increases in the average peak ligament strains at any impact acceleration compared with baseline.

Conclusions. The alar, transverse, and apical ligaments are not at risk for injury due to head-turned rear impacts up to 8 g. The upper cervical spine symptomatology reported by whiplash patients may, therefore, be explained by other factors, including severe whiplash trauma in excess of 8 g peak acceleration and/or other impact types, e.g., offset, rollover, and multiple collisions.

Alar, transverse, and apical ligament strains were monitored during head-turned rear impacts up to 8 g using whole cervical spine specimens with surrogate head and muscle force replication. The peak dynamic strains did not exceed baseline values, indicating that ligament injury did not occur.

From the Biomechanics Research Laboratory, Department of Orthopedics and Rehabilitation, Yale University School of Medicine, New Haven, CT.

Acknowledgment date: February 8, 2005. First revision date: March 17, 2005. Acceptance date: March 24, 2005.

Supported by NIH Grant No. 1 R01 AR45452 1A2 and the Doris Duke Charitable Foundation.

The manuscript submitted does not contain information about medical device(s)/drug(s).

Federal and Foundation funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

Address correspondence and reprint requests to Paul C. Ivancic, MPhil, Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, P.O. Box 208071, New Haven, CT 06520-8071. E-mail:

© 2006 Lippincott Williams & Wilkins, Inc.