Étude biomécanique de paramètres d'instrumentation chirurgicale antérieure du rachis scoliotique

Idiopathic scoliosis is a three-dimensional deformation of the spine and rib cage generally appearing during the adolescent growth period. Actual anterior surgical treatments, including arthrodesis, allow the correction of this deformity. The surgery by endoscopy studied in this thesis uses a novel less invasive approach. Anterior instrumentation also allows the reduction of instrumented levels, increasing the final spine mobility. However, within this approach, intervertebral disks need to be removed and arthrodesis to be performed. The biomechanical impact of the surgical instrumentation configuration in post-operative conditions is hard to evaluate by the surgeons in pre-operative situation. Actual choices are made on empirical bases, experience and biomechanical considerations. Therefore, the goal of this project is to evaluate the biomechanical parameters of the anterior instrumentation, in post-operative conditions, to recommend instrumentation configurations to the surgeons.

An experimental setup allowing stiffness and coupling measurements of an instrumented spinal model loaded to 8 N.m. in flexion, torsion and lateral inflexion has been developed. Spinal model were incorporating mechanical and geometrical properties of human vertebras. There were made of stacked cylinders and composed of two materials simulating cortical and cancellous bone. Eight different setups have been tested following a Box, Hunter and Hunter experimental plan in order to evaluate four parameters: CD Horizon Eclipse screw diameter (5.5–7.5 mm) and angle (0°–22.5°), bone grip of the screw (mono-bi cortical) and the amount of instrumented levels (5–8). (Abstract shortened by UMI.)