Rehabilitation from acute quadriplegia is frequently complicated by coexistent cervical spinal instability, in many cases secondary to ligamentous damage. Without surgery such injuries require bracing for three to six months often with the cumbersome halo-vest. Not only does this impede physical rehabilitation but even after its prolonged use, chronic spinal instability may still result. A variety of surgical procedures exist for reconstruction of the ligamentously unstable cervical spine. Few have a logical basis in preliminary research, but instead represent an individual's personal clinical experience and when attempted by others often have an unacceptable incidence of complication. The purpose of this project is to develop a canine cervical ligamentous instability model. Acute instability will be produced in a single spinal motion segment. Different general reconstructions will be applied to the model. The progression of instability in the model and the way in which the reconstructions alter it will be objectively studied by: 1. Serial Radiographs 2. Overload and, in some cases fatigue, flexion and extension mechanical testing using a Materials Test System - 810 Unit to generate the following mechanical parameters: A. Construct Shear and Angular stiffness, ultimate strength and energy absorption to failure. B. Total Shear and Angulation to failure. C. Number of cycles to failure for Constructs tested in fatigue. D. Changing Construct stiffness as a function of number of cycles for Constructs tested in fatigue. The above data will be statistically analyzed . 3. Histological slides of the interface between the reconstruction materials and the original spinal elements. The above studies will be obtained (from different experimental animals) at montly intervals postoperatively up to three months. A stability continuum for the different reconstructions will thus be created from which their strengths, weaknesses and specifc indications will be defined in a laboratory setting.
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