Designing Spinal Disc Prosthesis Implants Using Short Fiber Reinforced Composites
Spinal injury and the gradual deterioration of spinal discs that lead to back pain or spinal disorders can be treated surgically. One of the most promising surgical options under continuous development is the use of artificial discs to replace the patient’s natural spinal disc.
The materials used in these artificial discs are an important factor in the development of this technology. The discs must be made from materials that are safe to be implanted in the human body, do not cause allergic reactions, but are also wear resistant and compatible with medical imaging (MRI for example).
The challenge when designing implants that take advantage of reinforced plastics is predicting the manufactured material performance. The mechanical properties of an implant designed with fiber reinforced plastics can vary widely depending on the use of the material and how the implant is manufactured. The injection or compression molding process used to manufacture the implant will affect the fiber orientations throughout the part.
MSC Software’s material modeling and simulation tool, Digimat, produces a much more accurate prediction of the composite behavior for materials such as fiber reinforced plastics. The process was simple. Medicrea started with the same finite element model of the implant that is used for the existing analysis.
In the case of the Medicrea design, the original isotropic simulation over-predicted the implant’s stiffness by as much as 170%! The same simulation using a Digimat material model that accounted for both changes in fiber orientations as well as plastic deformations matched the test results almost perfectly.