Loosening of orthopaedic implants under repetitive loading is a frequent cause of implant failure. The Legacy Biomechanics Laboratory specializes in evaluation and optimization of implant fixation. We have developed laboratory models, which can simulate and evaluate implant loosening. These models aid orthopaedic implant manufacturers in predicting and optimizing implant fixation, migration and micromotion of novel implant designs. The Legacy Biomechanics Laboratory has established collaboration with leading implant manufacturers, including Zimmer, Synthes (USA), Mathys, Stryker (Europe), Smith & Nephew, and EBI. Currently, we maintain three models for implant-specific fixation failure simulation:

Locked Plate Fixation

Locked plates are revolutionizing plate fixation of bone fractures. We developed an osteoporotic diaphyseal bone model to evaluate locked plate performance in distinct loading modes.

HIPS: Hip Implant Performance Simulator

For evaluation of lag screw migration and cut-out failure, we developed a pertrochanteric fracture model. This model simulates for the first time bi-axial rocking motion and gate-cycle loading of the hip. In addition to the number of load cycles to cut-out failure, it acquires the complete 3-dimensional migration history of lag screws. Time and cost efficient simulation in surrogate bone specimens has been validated on cadaveric specimens.

Tibial Tray Tester

The tibial tray tester simulates micromotion and migration of tibial trays. It implements for the first time gate-cycle loading with combined anteroposterior load translation. It has been employed for evaluation of tibial components of total knee replacements and unicondylar knee replacements. Simulation in surrogate bone specimens has been validated on cadaveric specimens.