Session: 06-05 Implants and Biomedicine

Paper Number: 171951

171951 - A Multiphysics Finite Element Modeling Framework for a Piezoelectric Instrumented Knee Replacement 

Total Knee Replacement (TKR) surgery has gained momentum as an effective treatment for osteoarthritis and other debilitating joint disorders in the past half century. Several technological advancements have been realized over this time in regards to the materials used in and the overall design of TKR implants, however, the devices remain passive. A critical area for improvement of TKR devices is the integration of kinetic and kinematic sensing systems that can serve as a diagnostic tool to assess the health of the replaced joint by monitoring joint forces and motions throughout the life of the implant. Researchers have explored the use of strain gauges, capacitive sensors, and piezoelectrics for sensing joint loads. Piezoelectric transducers are particularly attractive due to their ability to sense joint loads, harvest energy, and use this energy to power measurement and telemetry devices. Our research group has been investigating the design of a piezoelectric sensing and energy harvesting system for use in TKR implants. Our existing numerical models depict an accurate representation of the implant geometry, forces, and optimal placement of the piezoelectric transducers for sensing forces within the knee. However, these models are not able to represent piezoelectric coupling, and model the piezoelectric as a passive material. The ability to numerically predict the electrical response of piezoelectric transducers within smart TKR designs is a critical step in the development of a modeling framework which can be used in the design and optimization of smart TKRs, particularly with respect to the energy harvesting performance. The purpose of this work is to advance our existing modeling framework by developing a multiphysics modeling framework for smart TKR design which predicts the electrical response of embedded piezoelectric transducers to realistic loads applied to the components of a total knee replacement.

A finite element model of our smart TKR design has been developed in ANSYS (ANSYS, Inc., Canonsburg, PA, USA) from 3D scanned and imported geometries of the Stryker Triathlon TKR system (Triathlon, Stryker, Mahwah, NJ, USA). The model includes an array of six piezoelectric transducers, placed below the polyethylene bearing component, that is used to sense compartmental loads and tibiofemoral contact locations, and harvest energy. This work focuses on updating the model to capture the multiphysics electromechanical response of the piezoelectric transducers. The multiphysics model is representative of the piezoelectric operating in 33-mode with the polarizing field in the axial direction, converting the input mechanical energy to electrical energy. The model will employ a uniaxial force profile applied to the femoral component simulating normal walking to generate an accurate representation of the electrical output from the piezoelectrics to compare with analytical and experimental data.  The purpose of this model is to provide a complete numerical representation of the TKR system. We aim to validate the model using an MTS uniaxial load frame to apply the same compressive load profile to a fabricated prototype, and compare the simulated results against the empirical data.

Presenting Author: Jacob Foster Tennessee Technological University

Presenting Author Biography: Jacob Foster
Master of Science in Mechanical Engineering from Tennessee Technological University
Ph.D. Student specializing in Dynamic and Smart Systems
Characterization and Applications of a New Zn-Al Alloy co-author
Tennessee Tech University, Cookeville, TN, USA
Jhfoster22@tntech.edu