Inertial properties and loading rates affect buckling modes and injury mechanisms in the cervical spine

Cervical spine injuries continue to be a costly societal problem. Future ad vancements in injury prevention depend on improved physical and computation al models which, in turn, are predicated on a better understanding of the r esponses of the neck during dynamic loading. Previous studies have shown th at the tolerance of the neck is dependent on its initial position and its b uckling behavior. This study uses a computational model to examine the mech anical factors influencing buckling behavior during impact to the neck. It was hypothesized that the inertial properties of the cervical spine influen ce the dynamics during compressive axial loading. The hypothesis was tested by performing parametric analyses of vertebral mass, mass moments of inert ia, motion segment stiffness, and loading rate. Increases in vertebral mass resulted in increasingly complex kinematics and larger peak loads and impu lses. Similar results were observed for increases in stiffness. Faster load ing rates were associated with higher peak loads and higher-order buckling modes. The results demonstrate that mass has a great deal of influence on t he buckling behavior of the neck, particularly with respect to the expressi on of higher-order modes. Injury types and mechanisms may be substantially altered by loading rate because inertial effects may influence whether the cervical spine fails in a compressive mode, or a bending mode. (C) 2000 Els evier Science Ltd. All rights reserved.