The fitting of the human joint through micro implanted sensors

The objective of this research is to integrate sensors to develop a fitting device capable of correcting the placement of artificial joints in humans. Improper fitting or balancing of a joint can lead to increased shear forces across the bone prosthesis interface, resulting varus-valgus instability, increased wear to the prosthetic components, and eventual premature failure of the prosthesis. In this study, an array of pressure sensors were placed between the articulating surfaces of a total knee that was surgically placed inside a cadaver knee. A jig was designed that simulates physiologic loads while flexing the knee through its normal range of motion. A distribution of contact pressure was recorded as a function of angle. A 3D PEM model of the knee Joint was built and a stress analysis was performed. The objective is three fold: (1) To understand the human joints and the effects of dynamic loading on the joint as a function of the contact pressure, (2) To correlate the FEM model with the experiment, (3) to predict failure mechanisms due to cyclic loading and improper load distribution