|
Total Knee Arthroplasty is an extremely common procedure carried out across the United States. However, despite the extensive research and testing leading to new methods of surgery and improved implant designs, approximately 20% of patients are dissatisfied with their knee replacements. Like any system, there are multiple factors that can lead to failure. These include wear and loosening, which can be caused by a misalignment during surgery or unbalanced ligaments. In order to detect loosening, there have been several attempts to utilize passive sensors, such as piezoelectric transducers and strain gauges, installed in artificial knee replacements to detect a shift in the proper alignment of the implant. There has also been recent work reported that utilized the active electromechanical impedance (EMI) sensing method, which uses a single PZT in order to detect a change in the state of the monitored system, to monitor knee replacements. However, the study isolated the system so that there was no external force applied to the PZTs while the testing was performed. This work is intended to evaluate the reliability of the EMI method for monitoring of total knee replacements under an applied force in order to determine whether or not this method can be utilized in-vivo to evaluate if a replacement has failed before it becomes hazardous to the patient. This work utilizes a rectangular block of artificial bone, a rectangular block of a similar metallic alloy used in tibial trays, and a polyethylene block made of material similar to the polymer used in bearings in order to simulate the tibia, tibial tray, and bearing, respectively. The artificial bone and metallic alloy components are bonded together with bone cement, and a PZT transducer is bonded to the alloy component using superglue. The polymer component is placed on top of the PZT transducer. The system is tested under static load to monitor several stages of artificial damage. This work is intended to serve as a foundation for further in-vivo and intra-operative studies.
|
