Authors: Tyler Peterson, Anna Jensen, Daniel Orr, Anton E Bowden
Mentors: Anton E Bowden
Insitution: Brigham Young University
Prior to approval for usage, spinal disc replacements undergo rigorous and costly tests to ensure that they will perform as designed once implanted. Wear testing, specifically, is one of the most important tests as any loose foreign particles can cause osteolysis of the surrounding tissue. Due to this, minimizing the wear experienced by a joint replacement is of extreme importance, however, wear testing is often done in latter stages of the design process as a functioning prototype is needed.
These tests can be prohibitively expensive and adjustments to the prototype only add to the costs, thus a more accessible test to get an initial estimate of the wear is desirable. There are current methods employed to perform these preliminary test results, including the use of a Tribometer, which tests friction and wear. Benefits of using a tribometer are that it can control environmental factors that parallel the ISO testing standards, however, these devices cost thousands of dollars.
In the present work, we designed a cost-effective preliminary testing apparatus that accurately recreates loadings that the implant will experience in flexion and extension, as well as lateral bending. The machine consists of a roller that can be loaded axially by compressing a spring to mimic realistic compressive loading conditions, and a motor that will move the roller to replicate spinal bending. The design incorporates a spring element to ensure that contact between the roller and the implant is preserved. Predictable, repeated motions achieved with this machine can provide early insights into the implant wear modes, which can facilitate iterative design improvements. Such knowledge early in the design process can save costs by reducing the need for major design changes in the late stages of product development.