Smart Orthopaedic Implants: Applications in Total Knee Arthroplasty

Abstract

Total knee arthroplasty is a common orthopaedic procedure conducted in the United States with approximately 700,000 surgeries performed annually. A common complication following total knee arthroplasty is anterior knee pain which affects tens to hundreds of thousands of people each year. The exact mechanism that leads to anterior knee pain remains unknown, but improper component selection may cause pathologic loading of the knee which leads to pain. Measuring loads in the knee to elucidate the mechanisms underlying anterior knee pain remains a challenge because the joints are so small. Using novel wireless sensor technology, we have developed and validated the first "smart" patellar implant capable of measuring force magnitude and force distribution in the knee. Implantable force sensors were calibrated and tested through the range of physiologic loading. Three sensors were then interfaced with a Zimmer patellar implant and placed into a custom loading apparatus. The smart patellar implant was then incrementally loaded from 0-500 N. Sensor signals were all recorded simultaneously in real time to measure the load across the patellofemoral joint. Results demonstrated that the smart patellar implant was able to accurately measure the load being transmitted across the simulated patellofemoral joint.