Real Time, In Vivo Mapping of Tibiofemoral Contact Pressures in Knee Arthroplasty

描述（由申请人提供）：提出了一种新的传感器系统，用于实时、体内监测膝关节置换术植入物的胫股接触压力，以预测植入物失效，并了解用户进行日常活动时植入物的实时动态。所提出的传感器系统将包括一个压敏磁层，嵌入在膝关节置换术植入物的聚乙烯插入物的顶表面下，用于绘制聚乙烯插入物和股骨部件之间的接触压力。压力感应层将由压力/应力敏感磁弹性薄条网格组成，这些薄条随着施加的力而改变其磁性。压力将在压力点测量，这些压力点位于网格的交叉处。每个传感条的磁化强度将通过监测其磁场的高次谐波来远程测量。这些传感条的响应将被输入到一个算法中，以确定所有压力点的压力负荷，从而可以实时、在体内地确定聚乙烯插入物顶部表面的压力分布。初步研究表明，通过磁弹性传感条阵列可以远程检测表面上的压力。然而，在将该技术应用于动物模型或人体试验之前，需要解决几个问题，包括可复制和生物相容的传感层的制造，可靠的检测系统和数据处理算法的开发，以及表征传感层的响应，确保其有效性。

DESCRIPTION (provided by applicant): A new sensor system is proposed for real time, in vivo monitoring of tibiofemoral contact pressures at knee arthroplasty implants for prediction of implant failure and understanding the real time dynamic of the implants when the user carries out his/her daily activities. The proposed sensor system will consist of a pressure-sensitive magnetic layer embedded under the top surface of the polyethylene insert of a knee arthroplasty implant for mapping the contact pressures between the polyethylene insert and femoral components. The pressure-sensing layer will consist of a grid of pressure/stress-sensitive magnetoelastic thin strips that change their magnetic properties with applied forces. Pressures will be measured at the pressure points, which are at the crossings of the grid. The magnetization of each sensing strip will be remotely measured by monitoring its magnetic higher-order harmonic fields. The responses of these sensing strips will be fed into an algorithm to determine the pressure loading at all pressure points, which allows real-time, in vivo determination of pressure profiles across the top surface of the polyethylene insert. Preliminary studies have demonstrated the remote detection of pressure across a surface with an array of magnetoelastic sensing strips. Prior to applying this technology to animal models or human trials, however, several issues will be addressed including the fabrication of reproducible and biocompatible sensing layer, development of a reliable detection system and data processing algorithm, and characterizing the response of the sensing layer ensuring its effectiveness. PUBLIC HEALTH RELEVANCE: There is a need to measure contact pressures at the femoral component of a knee arthroplasty implant to determine the wear and tear of the polyethylene insert of the implant. Today, most pressure monitoring systems for knee arthroplasty implants are either limited for in vitro or intraoperative uses, or cannot measure contact pressures across the surfaces of the femoral component and tibia plate. Development of a new technique for continuous, ambulatory monitoring of tibiofemoral contact pressures would be an enormous advance both in the detection of the implant failure and understanding the causes of the failure. While there are sensor systems that can either map the tibiofemoral contact pressures or provide continuous monitoring of the total pressure at the knee joint, to the PIs' knowledge there is no sensor system that can provide ambulatory mapping of tibiofemoral contact pressures. Therefore, the proposed sensor system, when successfully developed, will have a significant impact on the long term care of patients who receive knee arthroplasty implantation.