Design attributes of spinal fusion cages and a surgical instrument to aid thier screw fixationud

摘要

Spinal fusion cages are used to aid spinal fusion where the joint between the vertebrae is fused by bone graft. The design and material of these cages are of great importance to the fusion process. Methods such as screw fixation are sometimes used to secure these cages in vivo. However, access to the cage screw holes is partially obscured by the vertebral bodies. This study aimed to evaluate the effect of side-holes on the design of a cage, assess the feasibility of a bioactive/biodegradable composite as a cage material and develop an instrument to aid screw access to the cage screw holes. Computer models of cages with between 0 and 10 side-holes were produced to model compression between adjacent vertebrae. The bioactive/biodegradable composite as a cage material was analysed using a range of Young’s modulus values for the composite. The results suggested that the number of side-holes had a negligible effect on the stress distribution within the cage and the bioactive/biodegradable composite as a cervical cage material is unlikely to fail in static compression. A cutter instrument was developed in compliance with regulatory standards. It neatly removed the targeted vertebral edge adjacent to the cage screw holes allowing screw insertion.