ABSTRACT
The purpose of this study were to constructed multi-level cervical spine finite element (FE) model and to investigate changes in load distribution and range of motion (ROM) at index level and adjacent levels at immediately after anterior cervical discectomy and fusion (ACDF) and after full bony union using constrained and semi-constrained cervical plate systems(dynamic plate, variable screw). A FE model of intact cervical spine (C3-6) was created from computer tomography (CT) images of the healthy adult (male, 26 years, no pathologies). The post-op FE models (C5-6 with ACDF, cage with bone graft) were constructed by modifying a intact cervical FE model. Four different configurations of the model were considered: Type 1-Rigid plate+Fixed screw, Type II-Rigid plate + Variable screw, Type III-Dynamic plate + Fixed screw, Type IV-Dynamic plate + Variable screw. The bone-cage and bone screw interface behavior were accomplished via 'tie' contact condition and friction coefficient of 0.2 to assume fusion and non-fusion, respectively. The inferior endplate of C6 vertebral body was constrained in all directions. Loading condition used hybrid protocol with follower load of 73.6N at superior endplate of C3 vertebral body. In non-fusion cases, load at the bone graft increased from Type I to IV (2.3