title: Impact responses of the cervical spine: A computational study of the effects of muscle activity, torso constraint, and pre-flexion.
abstract: Cervical spine injuries continue to be a costly societal problem. Future advancements in injury prevention depend on improved physical and computational models, which are predicated on a better understanding of the neck response during dynamic loading. Previous studies have shown that the tolerance of the neck is dependent on its initial position and its buckling behavior. This study uses a computational model to examine three important factors hypothesized to influence the loads experienced by vertebrae in the neck under compressive impact: muscle activation, torso constraints, and pre-flexion angle of the cervical spine. Since cadaver testing is not practical for large scale parametric analyses, these factors were studied using a previously validated computational model. On average, simulations with active muscles had 32% larger compressive forces and 25% larger shear forces-well in excess of what was expected from the muscle forces alone. In the short period of time required for neck injury, constraints on torso motion increased the average neck compression by less than 250N. The pre-flexion hypothesis was tested by examining pre-flexion angles from neutral (0°) to 64°. Increases in pre-flexion resulted in the largest increases in peak loads and the expression of higher-order buckling modes. Peak force and buckling modality were both very sensitive to pre-flexion angle. These results validate the relevance of prior cadaver models for neck injury and help explain the wide variety of cervical spine fractures that can result from ostensibly similar compressive loadings. They also give insight into the mechanistic differences between burst fractures and lower cervical spine dislocations.
authors.affiliation: Duke University, Department of Biomedical Engineering and Division of Orthopaedic Surgery, Box 90281 Durham, NC 27708-0281, United States. Electronic address: rwn@duke.edu.
authors.forename: Roger W
authors.initials: RW
authors.lastname: Nightingale
authors.affiliation: Duke University, Department of Biomedical Engineering and Division of Orthopaedic Surgery, Box 90281 Durham, NC 27708-0281, United States.
authors.forename: Jake
authors.initials: J
authors.lastname: Sganga
authors.affiliation: Duke University, Department of Biomedical Engineering and Division of Orthopaedic Surgery, Box 90281 Durham, NC 27708-0281, United States.
authors.forename: Hattie
authors.initials: H
authors.lastname: Cutcliffe
authors.affiliation: Duke University, Department of Biomedical Engineering and Division of Orthopaedic Surgery, Box 90281 Durham, NC 27708-0281, United States.
authors.forename: Cameron R 'Dale'
authors.initials: CR
authors.lastname: Bass
mesh_terms: D001696:Biomechanical Phenomena; D002574:Cervical Vertebrae / Q000502:physiology* / Q000503:physiopathology; D019245:Compressive Strength; D003198:Computer Simulation; D050723:Fractures, Bone / Q000503:physiopathology; D006801:Humans; D008297:Male; D055595:Mechanical Phenomena; D009132:Muscles / Q000502:physiology* / Q000503:physiopathology; D019838:Neck Injuries / Q000503:physiopathology; D016059:Range of Motion, Articular; D013124:Spinal Injuries / Q000503:physiopathology; D060726:Torso / Q000502:physiology* / Q000503:physiopathology; D016474:Weight-Bearing
keywords: Alignment; Bilateral facet Dislocation; Biomechanics; Buckling; Cervical spine; Compression; Initial conditions; Muscle; Pre-flexion; Preflexion