Biomechanical analysis and comparison of the native and prosthetic cervical intervertebral disc

• Autor(a) principal: Costa, Gonçalo Pratas Lima da
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/38515
• topic: Cervical Spine; Biomechanics; Intervertebral disc; Arthroplasty; Prosthetic disc; Deformation

The main objective of this study is to build a biomechanical analysis and comparison between the natural intervertebral disc (IVD) and the artificial prosthetic disc on the cervical spine. The cervical spine is a complex and essential structure that provides motion and stability while also protecting the spinal cord. The spine includes several structures including the vertebrae, the IVDs, nervous tissues, and ligaments. The cervical spine can perform several movements of the head which include extension, flexion, lateral bending and axial rotation. It has different forces applied in different directions due the muscles, ligaments and weight of different structures. With an injury in the spine or just with aging, spinal pathologies such as degenerative disc disease (DDD) and traumatic disc herniation can occur. These diseases cause the IVD to lose its integrity causing pain and loss of flexibility. Several treatments exist including total disc replacement with a prosthetic disc. There are several models of these devices and each one has its benefits. In this work the Mobi-C was used to compare its biomechanical properties to the natural disc. There is a scarcity of studies doing this comparison but there are several studies that show the compressive behaviour of the natural and prosthetic disc separately. An experimental model was created to mimic the cervical spine in a tensile tester machine to test the natural and prosthetic disc. The C5 and C6 vertebrae were chosen for this study because they are similar in structure, and they are located in the lower part of the cervical spine where loads applied are higher. Different materials are used in this system including the vertebrae, support pieces, the Mobi-C disc, a natural disc model, ligaments and tri-axial strain gauges. The assembly can mimic the neutral, flexion of 10 degrees and extension of 10 degrees of the spine. Strain gauge sensors were used to evaluate the deformation in the anterior and posterior facets of the vertebral body of each vertebra. Three different natural discs with three different hardness values were tested and compared with each other. One natural disc was chosen to compare with the prosthetic disc. Both models were assessed for different positions of the spine giving maximum and minimum values of principal strain for each sensor ( and ). When comparing the natural and prosthetic models, it was concluded that the assembly with the natural discs distribute the load applied to the system less evenly across the vertebral body than the prosthetic disc. The difference between the highest strain value and the lowest is 520.76 μm/m and 0.59 μm/m for and in the natural disc model and 207.31 μm/m and 274.77 μm/m for and in the prosthetic disc model. The disparity between values in different sensors is noticeably higher in the natural disc than in the prosthetic disc. So, the main conclusion was that the prosthetic disc distributes the load of the cervical spine in a more uniform distribution on the vertebral body of the vertebrae than the natural disc model due mainly to its geometry, mechanical properties and position in this experimental assembly which suggests benefits for treating spinal pathologies.