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

描述(申请人提供)：提出了一种新的传感器系统，用于实时、活体监测膝关节置换植入物的胫股接触压力，以预测植入物失败并了解使用者进行日常活动时植入物的实时动态。建议的传感器系统将由嵌入在膝关节置换植入物的聚乙烯植入物的顶面下的压敏磁层组成，用于映射聚乙烯植入物和股骨部件之间的接触压力。压力传感层将由压力/应力敏感磁弹性薄带组成的栅格组成，这些薄带会随着外力的变化而改变其磁性。压力将在压力点测量，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高次谐波磁场进行远程测量。这些传感条的响应将被送入一个算法，以确定所有压力点的压力载荷，从而允许实时、活体地确定聚乙烯插入物顶面上的压力分布。初步研究已经证明，利用磁弹性传感条阵列可以远程检测表面上的压力。然而，在将这项技术应用于动物模型或人体试验之前，将解决几个问题，包括制造可重现的和生物兼容的感应层，开发可靠的检测系统和数据处理算法，以及表征感应层的响应以确保其有效性。 公共卫生相关性：有必要测量膝关节置换植入物的股骨部件处的接触压力，以确定植入物的聚乙烯衬垫的磨损。今天，大多数膝关节置换植入物的压力监测系统要么仅限于体外或术中使用，要么无法测量股骨假体和胫骨板表面的接触压力。开发一种连续的、动态监测胫股接触压力的新技术，将是在检测植入物失败和了解失败原因方面的巨大进步。虽然有传感器系统可以测绘胫股接触压力或提供膝关节总压的连续监测，但据PI所知，没有传感器系统可以提供动态的胫股接触压力测绘。因此，拟议的传感器系统一旦成功开发，将对接受膝关节置换术的患者的长期护理产生重大影响。

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.