Evaluation of Spinal Arthrodesis Implant Designs: A Biomedicial-Legal Perspective

A successful spinal implant design requires that it perform consistently under a known set of loading conditions. Specifically, the loading conditions experienced in the activities of everyday living must be accounted for in both the design and testing of spinal arthrodesis implants. Knowledge of these loading conditions and, in particular, those which produce implant failure, must be addressed continuously during the design, testing and even during the actual clinical use of the implant. The goals of this presentation are: 1) to provide an understanding of typical spinal implant test procedures and, 2) to understand how to utilize real world failure data to optimize the test loading conditions which would predict failure of a spinal implant. For the first goal, ASTM standards for testing of spinal implants will be described and, for the second goal, data from a clinical case with failure of a pedicle screw connector will be utilized. This will include data from the patient’s medical records, structural and material properties of the implant material, and accident reconstruction analyses. The combined data will provide a most probable cause of implant failure and failure load.