Ruther Cathérine, Ewald Hartmut, Mittelmeier Wolfram, Fritsche Andreas, Bader Rainer, Kluess Daniel
Department of Orthopedics, University of Rostock, 18057 Rostock, Germany.
J Biomech Eng. 2011 Oct;133(10):104503. doi: 10.1115/1.4005222.
The main reason for the revision of total hip replacements is aseptic loosening, caused by stress shielding and wear particle induced osteolysis. In order to detect an implant loosening early, the osseointegration of endoprosthetic implants must be measured exactly. Currently applied diagnostic methods, such as standard radiographs and clinical symptomatology, often result in an imprecise diagnosis. A novel radiation-free method to improve the diagnostic investigation of implant loosening is presented. The osseointegration of an implant can be identified using mechanical magnetic sensors (oscillators), which impinge on small membranes inside an implant component, e.g., the femoral hip stem. The maximum velocity after impingement of the oscillator depends on the osseointegration of the implant. Excitation of the oscillator is realized by a coil outside the human body. Another external coil is used to detect the velocity of the oscillator. To demonstrate the principle of the novel loosening sensor, an overdimensioned test device was designed to measure simulated loosening phases in the first experimental tests with different material layers. The overdimensioned test device of the loosening sensor showed significant differences in the various phases of fixation. Analysis of the membrane without any material layer in the case of advanced loosening resulted in a 23% higher maximum velocity compared to an attached artificial bone layer. Based on these preliminary results, the sensor system shows potential for the detection of implant loosening. Moreover, the proposed system could be used in experimental applications to determine the quality of bioactive coatings and new implant materials.
全髋关节置换术翻修的主要原因是无菌性松动，这是由应力遮挡和磨损颗粒诱导的骨溶解引起的。为了早期检测植入物松动，必须精确测量假体植入物的骨整合情况。目前应用的诊断方法，如标准X线片和临床症状，往往导致诊断不准确。本文提出了一种新型的无辐射方法来改进植入物松动的诊断研究。可以使用机械磁传感器（振荡器）来识别植入物的骨整合情况，该传感器撞击植入部件（如股骨柄）内的小薄膜。振荡器撞击后的最大速度取决于植入物的骨整合情况。振荡器的激发通过人体外部的线圈实现。另一个外部线圈用于检测振荡器的速度。为了演示新型松动传感器的原理，设计了一个尺寸过大的测试装置，用于在首次实验测试中测量不同材料层的模拟松动阶段。松动传感器的尺寸过大的测试装置在固定的各个阶段显示出显著差异。在晚期松动的情况下，对没有任何材料层的薄膜进行分析，其最大速度比附着有人造骨层的情况高23%。基于这些初步结果，该传感器系统显示出检测植入物松动的潜力。此外，所提出的系统可用于实验应用，以确定生物活性涂层和新型植入材料的质量。
