Numerical Modelling of a Cervical Spine Discectomy

Abstract

Cervical spine discectomy is a relatively common medical procedure which entails the surgical removal of a herniated intervertebral disc which is then replaced with an adequate prosthesis. Surgeons rely on their expertise to minimize the damage induced on the adjacent vertebrae and discs during this invasive procedure in order to reduce the patient's postsurgical distress. A typical cervical spine discectomy has been modelled and tested using the Finite
Element Method (FEM) with the intention of contributing to better elucidate its immediate physical consequences on the vertebrae and intervertebral discs. Internal stresses, strains and damage levels can be obtained through the use of FE models, which can prove useful in improving surgical procedures or tailoring them to the need of particular patients. To this aim, a
model of four cervical vertebrae with their corresponding discs has been built. Spinal ligaments, zygapophyseal joints and uncovertebral joints have also been included. The vertebrae have been modelled using a damage model whilst the intervertebral discs and ligaments have been treated as separate hyperelastic materials. Also, the nucleus and the annulus of the discs have been dierentiated. The problem has been solved following non-linear large deformation theory and considering prestress in the ligaments. The model's accuracy has been assessed through comparison of previously published results for dierent spinal movements (N. Kallemeyn et al., Med Eng Phys, 32(5):482-489 (2010)). Then, the model has been numerically tested for a load case representative of the discectomy procedure.