Design Modifications and Optimization of a Commercially Available Knee Simulator

To determine the wear behavior of knee endoprostheses, implants are tested in knee simulators before being introduced to the market. Implants may undergo mechanical failure and wear debris is generated. The magnitude and morphology of this debris are determined to gain information about its biological reactivity. In this study, we describe the modifications made to the AMTI multistation knee simulator. The simulator is not capable to ensure a medially biased load distribution as required per ISO 14243, and therefore the usage of the simulator is limited. Thus, simulator modifications were made to implement a wear test as outlined in ISO 14243, and to improve both user-friendliness of operation and cost of simulation. In particular, this involved modifying the implant holders and controlling implant kinematics during the simulation. For component design, a 3D computer-aided design software was used. After the manufacturing of all components had been completed, the redesigned system was put into operation. In a final wear test, functionality and conformance with the ISO standard were tested for the modified simulator. After implementation of design modifications, it is possible to run wear tests with a medially biased load distribution according to ISO 14243.