Biodegradable cages for the degenerated disc

Purpose and goal:

The aim was to design spinal cages made of Mg alloy WE43 using topology optimization, and verify their function in bench tests. A finite element code was developed where cages were optimized to account for temporal degradation and WE43 material properties. Mechanical testing according to ASTM F2077 was conducted for cages at different degradation time points. While the project goal was fulfilled, further material development is needed to achieve a well-functioning implant.

Expected results and effects:

The cage design was successfully optimised, produced, and tested. The mechanical testing of the degraded samples showed an interesting trend that captures the complexity of biodegradable materials. Pitting corrosion was observed to be the main initiator of mechanical failure. These results give insight on the feasibility of using additively manufactured WE43 alloy in spinal applications. HTA analysis predicts a substantial positive effect on the society for these types of implants.

Approach and implementation:

A topology optimisation algorithm capable of efficiently designing geometries with material phases that vary both spatially and temporally was developed. Once that was completed, design and printing parameter optimization could be done simultaneously. This allowed for an efficient printing stage and further mechanical testing. Collaborative meetings were conducted on a bi-weekly schedule, which allowed all to communicate effectively and minimise disruptions.