OPTIMIZATION OF BONE GRAFT SHAPES OF S-TYPE CERVICAL CAGE THROUGH GENETIC ALGORITHM

Abstract

The fourth and fifth cervical vertebrae are the common sites of injury and disc degeneration. The interbody fusion failure was observed after fusion surgery. The postoperative effects are subsidence, migration, and nonfusion of the implants due to the improper cage design. Finite element analysis is the most efficient tool to simulate the surgical condition using computer-aided design models. In this study, we designed an S-type dynamic cage with a different geometry of bone graft. The objective of our study is to reduce the stresses in the dynamic cage, so the risk of subsidence is controlled and optimized for the best suitable shape. The different geometry of a bone graft designed for the dynamic cage are square, circular, rectangular, and elliptical. In this study, the bone grafts producing higher stress need to be selected for the cage design. A three-dimensional finite element model form C3-C6 was developed, and in the C4-C5 level, the S-type dynamic cage with the bone graft was virtually inserted. The S-type dynamic cage with the elliptical graft exhibited a lower stress in the cage and higher stress in the bone graft. The optimized cage with the graft reduces the risk of subsidence and increases osteointegration so the fusion can be achieved. Keeping this in mind, the genetic algorithm is used for optimizing the stress level and assigning a correct material and shape for the cage and bone graft for a particular patient.