| Anterior cervical corpectomy with strut graft reconstruction is a surgical technique used in the treatment of myelopathy due to spinal cord compression. It is almost universally accepted as a safe and effective method of treatment for short decompressions requiring removal of only one or two vertebral bodies. Longer decompressions present a greater challenge, however, with reported complication or failure rates as high as 50%. Nevertheless, high rates of symptom resolution and low recurrence indicate that, despite the difficulties, corpectomy with strut graft reconstruction will continue to be recommended for treatment of multilevel CSM.; A newly developed, anatomically accurate analytical model of the subaxial cervical spine using advanced finite elements is presented. The model includes accommodation for modeling of the methods and instrumentation used in multilevel corpectomy surgeries. Material models for vertebrae, ligaments, and intervertebral discs are developed. Articular facet contact is accounted for using a low friction sliding contact formulation. The model was validated using published experimental data for intact spine segments.; The biomechanical properties of the intact and surgically reconstructed cervical spine are assessed. Several types of supplemental internal stabilization are evaluated including rigid anterior plating, posterior segmental fixation, and circumferential stabilization, which combines the anterior and posterior devices. The role of these devices in potential strut graft failure is evaluated using applied moments and forces. Findings include the presence of large shear forces at the ends of the uninstrumented strut graft in flexion, extension, and lateral bending which can lead to graft dislodgment, migration, and fracture. Supplemental fixation devices are effective in reducing strut graft shear as well as increasing overall construct stability. However, the introduction of fixation devices causes significant stress concentrations in the anterior vertebral bodies. This is of particular concern in the case of isolated rigid anterior plating where the calculated vertebral stresses approach the yield stress of cortical bone indicating the potential for screw pull outs and vertebral or endplate fracture.; Finally, a novel method of including physiological muscle forces is implemented and applied to the problem of strut graft biomechanics. Findings include increased construct stiffness, particularly in flexion, and increased graft shear in flexion and extension. |
