Dynamic simulation of cervical spine following single-level cervical disc replacement

The aim of the present study is to analyze the simulated behavior of the Functional Spinal Unit (FSU) with a disc implant inserted in the C5-C6 segment, compare the results to the literature and use the data for disc design parameters. Intradiscal forces/pressures, bending moments and vertebral body rotations were calculated and compared to in-vitro and simulated results in the literature. This data can also be used to evaluate the prescribed input parameters for the ISO/DIS 18192-1 experimental protocol for evaluating cervical disc implants. LifeMOD was used as simulation software package and the cervical model was set up to closely resemble in-vivo conditions. Maximum range of motion data for ten student volunteers was used as input motion for the model. The results obtained correlated well with literature and it was interesting to see the retained motion at the C5-C6 segment containing the implant, which contradicts clinical and simulation results found for spinal fusion. The presented simulation model is hence deemed proficient to critically evaluate the dynamics of a cervical disc design and to relatively accurately prescribe in-vivo input forces and motions acting on a cervical disc.