Design, analysis, and fabrication of a piezoelectric force tray for total knee replacements

Force plates have been widely adopted in biomechanical gait analysis to measure reaction forces and the center of pressure. In this work, the force plate concept is miniaturized and extended for use within the polyethylene bearing insert of a total knee replacement. A simplified rectangular-shaped force plate with multiple integrated piezoelectric sensors, including designs with six and eight transducers, is presented in this work. The performance of the sensory system is investigated through finite element analysis and experimental validation. Initially, the ability of the two designs in sensing compartmental forces and contact point locations on one side of the force plate is numerically investigated. Selected designs of the force plate are then fabricated and used to experimentally validate the performance of the system. The results show a maximum error of less than 6% and 4.5% in compartmental force amplitude sensing for the force plates with six and eight transducers, respectively. The force plates were able to detect the contact point location with maximum errors of less than 1 mm. The relatively small sensing error quantities show the potential of using a piezoelectric force plate sensor design in total knee replacement as well as other force sensing applications.