Kinematic and Anatomical Analysis of the Human Cervical Spinal Column Under Axial Loading

The patho-anatomic alterations due to vertical loading of the human cervical column were documented and correlated with biomechanical kinematic data. Seven fresh human cadaveric head-neck complexes were prepared, and six-axis load cells were placed at the proximal and distal ends of the specimens to document the gross biomechanical response. Retroreflective markers were placed on bony landmarks of vertebral bodies, articular facets, and spinous processes along the entire cervical column. Targets were also placed on the occiput and arch of C1. The localized movements of these markers were recorded using a video analyzer during the entire loading cycle. Pre-test two-dimensional, and three-dimensional computerized tomography (CT), and plane radiographs were taken. The specimens were loaded to failure using an electrohydraulic testing device at a rate of 2 mm/s. Preparations were deep frozen in the compressed state using dry ice and liquid nitrogen to preserve the deformations of the tissues as well as bony alterations. Two-dimensional CT's were done and sequential anatomic sections were taken using a cryomicrotome. These image data documented the soft and hard tissue strains. Biomechanical data (strength and localized kinematics) together with the image data correlated well with the pathology. Upper cervical injuries were observed under compression-extension modes while lower cervical injuries occurred under compression-flexion modes. Because the specimens were analyzed at failure, preserving tissue alterations, the pathology observed in the present study may provide an insight into the behavior of the cervical spine at the level of injury.