*WINNER* Parametric Testing of Surrogate Knee Replacement Bearings with Embedded Piezoelectric Transducers

Abstract

Total Knee Replacement (TKR) is a common surgery, yet often times the long-term results are less than satisfactory due to misalignment of the knee. Within the first few years of surgery about 20% of knee replacement recipients report discomfort or undesired functionality. One major underlying cause of this ligamentous imbalance is lack of numerical data for surgery. This study tests the force location and magnitude estimation capabilities of knee replacement bearings with embedded piezoelectric transducers. In this study, two different manufacturing methods are used to build bearing prototypes: Fused Deposition Modeling (FDM) 3D printed from PLA, as well as Computer Numerical Control (CNC) machining from UHMW polyethylene. These prototypes are compared in their ability to sense applied force inputs given certain test parameters. The prototypes are tested in a fixture designed to replicate the knee as it goes through normal and irregular gait cycles. The fixture can position between 0 and 90 degrees of flexion and can replicate axial rotation as well as lateral translation between the femoral component and knee bearing interface; this permits simulation of a knee with correct alignment and simulation of misaligned knees. This study provides a comparison between predictions from the piezoelectric sensors and actual measurements from the load frame for force magnitude and contact locations. The aim of this study is to give insight to the feasibility of a 6-sensor array within a patient's actual knee bearing, and how well surgical teams will be able to utilize this novel application of piezoelectric transducers.