| Summary: | 碩士 === 國立陽明大學 === 醫學工程研究所 === 100 === Security verifications with international testing standards before marketing are essential for orthopaedic implants. Lumbar disc prosthesis, as a non-fusion implant for treatment of degenerated lumbar intervertebral disc, has met the basic biomechanical requirements through the examination with ASTM F-2646. It has been claimed that the defined testing conditions in ASTM standard cannot include all the possible situations after implantation, thus failures of disc prostheses in clinical practice may be the evidences that the current testing method may be a perfect way. A modified compressive-shearing test (MCS test), based on ASTM standard, has been developed utilized for evaluating the security of polyethylene (PE) component in disc prosthesis. However, loading conditions in the MCS test have not been completely evaluated, neither has the comparison between the MCS test and ASTM standard been performed. Purpose of current study was to accomplish a more completed finite element evaluation to the MCS test method with 2 commercial lumbar disc prostheses, and also compared with traditional ASTM standard testing method to confirm the differences between the methods. The values and distributions of von Mises stresses on PE components were considered as the main mechanical parameter for evaluation. Results revealed that, lower resultant force was required for PE component failure in the MCS test method than the ASTM standard testing method. With the application of MCS test method, the mechanical safe zones can be respectively defined for the different prosthetic disc designs. Current study has accomplished more detailed evaluations of the MCS test method, and represented that the mechanical failure of PE component in lumbar disc prosthesis can be more conservatively evaluated using the MCS test method than the ASTM standard testing method. The MCS test method can be beneficial for future lumbar disc prosthesis in the early stage of its designing process.
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