Human Knee Prosthesis Equipped with Force Sensors

In-vivo monitoring of human knee implants after total arthroplasty increases the knowledge about articular motion and loading conditions. The proposed knee prosthesis equipped with force sensors executes force measurements in polyethylene human knee prosthesis by two sensorized metal bars positioned under the femoral condyles and fully contained in the polyethylene insert. In this paper, a new force sensor, which acts in the knee integrated in the prosthesis, is proposed with the aim of reducing the hysteresis of polyethylene material and increase the rigidity of the insert. The fabricated sensors are characterized and tested by means of a mechanical press controlled load. The realized conditioning electronics is done by low power components and it can be integrated in an autonomous system. The forces transmitted across the knee joint during normal human activities such as walking, running or climbing can be directly measured. Furthermore, the device can be used to improve design, refine surgical instrumentation, guide post-operative physical therapy and detect human activities that can overload the system.