Multiplanar Cervical Spine Injury Due to Head-Turned Rear Impact

Abstract

Head-turned whole cervical spine model was stabilized with muscle force replication and subjected to simulated rear impacts of increasing severity. Multiplanar flexibility testing evaluated any resulting injury. To identify and quantify cervical spine soft tissue injury and injury threshold acceleration for head-turned rear impact, and to compare these data with previously published head-forward rear and frontal impact results. Epidemiologically and clinically, head-turned rear impact is associated with increased injury severity and symptom duration, as compared to forward facing. To our knowledge, no biomechanical data exist to explain this finding. Six human cervical spine specimens (C0-T1) with head-turned and muscle force replication were rear impacted at 3.5, 5, 6.5, and 8 g, and flexibility tests were performed before and after each impact. Soft tissue injury was defined as a significant increase (P < 0.05) in intervertebral flexibility above baseline. Injury threshold was the lowest T1 horizontal peak acceleration that caused the injury. The injury threshold acceleration was 5 g with injury occurring in extension or axial rotation at C3-C4 through C7-T1, excluding C6-C7. Following 8 g, 3-plane injury occurred in extension and axial rotation at C5-C6, while 2-plane injury occurred at C7-T1. Head-turned rear impact caused significantly greater injury at C0-C1 and C5-C6, as compared to head-forward rear and frontal impacts, and resulted in multiplanar injuries at C5-C6 and C7-T1.