Alar, transverse, and apical ligament strain due to head-turned rear impact

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

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.

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.

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.

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.

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.