Traumatic instabilities of the cervical spine caused by high-speed axial compression in a human model: An in vitro biomechanical study

Abstract

Study Design. Traumatic injury of the cervical spine was produced on human cadavers and evaluated with instability tests and radiographs. Objective. To relate traumatic injuries of the cervical spine to instability and patterns of traumatic injury to different levels of impact energy. Summary of Background Data. Data from young human cadavers are rare in traumatic models of the cervical spine, and instabilities caused by axial compression with different impacts remain unknown. Methods. Fourteen cervical spine specimens (C2-C4) obtained from fresh human cadavers were divided evenly into two groups and subjected to axial compressive impact with 30 J and 50 J impact energy, respectively. Pure moments in flexion-extension, left/right lateral bending, and left/right axial rotation were applied to each specimen before and after trauma. The maximum moment was 2.0 Nm in each case. Ranges of motion and neutral zones were measured using stereophotogrammetry. Results. Ranges of motion and neutral zones for both groups increased after trauma. No bony injury was observed on the radiographs after trauma with 30 J, but motions increased significantly in flexion, extension, and axial rotation. All specimens showed bony injuries after trauma with 50 J, whereas motions continued to increase significantly in all directions. The relative neutral zone values were larger than the corresponding range of motion values, except in flexion-extension after trauma with 50 J. Conclusions. The injury patterns of the cervical spine were associated with impact energy, and a high level of impact energy could produce either three-column injury or anterior middle-column injury. Instabilities of the cervical spine caused by compressive trauma increased with the level of impact energy. The neutral zone was more sensitive than the range of motion in representing spinal instability testing was more sensitive than radiographs in evaluating traumatic injury of cervical spine.