A Development of Force Distribution Measurement System with High Resolution for Total Knee Arthroplasty

Soft tissue or ligament balancing in total knee arthroplasty is important for ensuring knee joint stability. Correct balancing and appropriate alignment of ligaments extend prosthesis life by preventing unnecessary force fromacting on the prosthesis during routine activities. The current implementation of total knee arthroplasty relies heavily on the subjective “feel” of the surgeon for correct prosthesis implantation onto tibiofemoral components. We developed a force distribution sensing systemto provide quantitative information to surgeons during ligament balancing. The measurement system consists of two main components: two force sensors embedded in trial insert for each condyle and signal acquisition for data processing and force visualization. Sensors were designed and developed using pressure-sensitive conductive rubber that measures changes in resistance in the event of deformation caused by external force. Corresponding voltage measured by circuits is transmitted via an RF transceiver to a computer and visualized as color gradient. Current sensors could measure maximum force of 196.13 N (20 kgf). Results from calibration and experiments on a plastic trial prosthesis indicated that the device has good potential for providing appropriate force distribution information on the knee during total knee arthroplasty procedure.