IEEE Trans Biomed Circuits Syst. 2021 Feb;15(1):102-110. doi: 10.1109/TBCAS.2021.3052970. Epub 2021 Mar 30.
Implant failure can have devastating consequences on patient outcomes following joint replacement. Time to diagnosis affects subsequent treatment success, but current diagnostics do not give early warning and lack accuracy. This research proposes an embedded ultrasound system to monitor implant fixation and temperature - a potential indicator of infection. Requiring only two implanted components: a piezoelectric transducer and a coil, pulse-echo responses are elicited via a three-coil inductive link. This passive system avoids the need for batteries, energy harvesters, and microprocessors, resulting in minimal changes to existing implant architecture. Proof-of-concept was demonstrated in vitro for a titanium plate cemented into synthetic bone, using a small embedded coil with 10 mm diameter. Gross loosening - simulated by completely debonding the implant-cement interface - was detectable with 95% confidence at up to 12 mm implantation depth. Temperature was calibrated with root mean square error of 0.19°C at 5 mm, with measurements accurate to ±1°C with 95% confidence up to 6 mm implantation depth. These data demonstrate that with only a transducer and coil implanted, it is possible to measure fixation and temperature simultaneously. This simple smart implant approach minimises the need to modify well-established implant designs, and hence could enable mass-market adoption.
植入物失败会对关节置换后的患者预后产生毁灭性的影响。诊断时间会影响后续的治疗效果，但目前的诊断方法没有早期预警，也不够准确。本研究提出了一种嵌入式超声系统来监测植入物的固定和温度——这是感染的潜在指标。该系统仅需要两个植入组件：一个压电换能器和一个线圈，通过三个线圈的感应链路来产生脉冲回波响应。这种无源系统避免了对电池、能量收集器和微处理器的需求，对现有植入物结构的改动最小。在体外，使用直径为 10 毫米的小型嵌入式线圈，对粘接到合成骨上的钛板进行了验证。通过完全分离植入物-水泥界面来模拟严重松动，在最大植入深度为 12 毫米时，其可信度为 95%，可以检测到松动。在 5 毫米处，温度的均方根误差为 0.19°C，在最大植入深度为 6 毫米时，可信度为 95%，测量精度可达±1°C。这些数据表明，仅通过植入一个换能器和一个线圈，就可以同时测量固定和温度。这种简单的智能植入方法最大限度地减少了对成熟植入物设计进行修改的需要，因此可能实现大规模市场应用。
