Finite Element Study of Bending of a Custom 2-Level Anterior Cervical Plate in 4-Point Configuration

The objective of this work is to develop a finite element (FE) model for studying the 4-point bend characteristics of a custom 2-level anterior cervical plate (ACP), a fixation device used in spinal surgeries. It is important to establish the flexural behaviour of the cervical plate prior to using them in surgical constructs, where they are subjected to physiological loads. Furthermore, such a study is also important if there are changes in the processing path. Herein, a heat treatment specifically developed for slender Ti6Al4V castings and the properties therefrom, were used for the model. Simulations of 4-point bend test of the ACP with rigid segment attachments were performed using ANSYS Static Structural Module, formulated as a non-linear mechanical problem. A precursor model of 4-point bend test of a rectangular sheet specimen of Ti6Al4V was developed and validated by independent measurements. The ACP model revealed a peculiar double-yield behaviour in the load–deflection response, attributed to non-uniform stress distribution in the plate structure. While the outer face showed stress concentration at the graft windows, stress concentrated along the plate edges on the inner face. The bending stiffness and strength of the plate were determined to be 818 N/mm and 17 Nm, respectively. The present model is expected to be useful towards iterative device design optimization, in-lieu of measurement, saving time and cost associated with repeated experimentation. Secondly, such models enable the realization of ‘leaner’ implants by combining the benefits of iterative design optimization with material property enhancements brought about by process improvements.