Bühler D W, Oxland T R, Nolte L P
M. E. Müller Institute for Biomechanics, University of Bern, Switzerland.
Med Eng Phys. 1997 Mar;19(2):187-99. doi: 10.1016/s1350-4533(96)00060-4.
Implant micromotion is considered to be a major factor in the loosening of cementless total hip replacements. Translational micromotion at the bone-implant interface generally occurs in all three spatial directions. Under physiological loading, the interfacial micromotion consists of a cyclic amplitude and changes in the mean, which, in the cranio-caudal direction, represents subsidence of the prosthesis. Existing measurement strategies, which are based on dial gauges, extensometers, LVDTs, hall-effect transducers or strain gauge techniques provide information about only one component of the general three-dimensional micromovement. Moreover, in the majority of the studies, the data are difficult to interpret due to the measured motions being composed of interfacial micromotion and femoral strains. A new transducer was designed that allows the accurate measurement of all three isolated components of micromotion. An optoelectronic approach, based on silicon position-sensitive detectors (PSD) in combination with high precision mechanical parts, was chosen. To exclude thermodrifts during long-term testing, a thermistor was integrated in the sensor. Validation experiments on a precision positioning table indicated the high precision and resolution of the developed sensors. Furthermore, in-vitro tests on a standard press-fit prosthesis demonstrated the easy handling and reliability of the system.
植入物微动被认为是无骨水泥全髋关节置换术松动的主要因素。骨-植入物界面处的平移微动通常在所有三个空间方向上发生。在生理负荷下，界面微动由循环振幅和平均值变化组成，在头-尾方向上，这代表假体的下沉。现有的基于百分表、引伸计、线性可变差动变压器、霍尔效应传感器或应变片技术的测量策略仅提供一般三维微动中一个分量的信息。此外，在大多数研究中，由于测量的运动由界面微动和股骨应变组成，数据难以解释。设计了一种新型传感器，能够精确测量微动的所有三个独立分量。采用了一种基于硅位置敏感探测器（PSD）并结合高精度机械部件的光电方法。为了排除长期测试过程中的热漂移，在传感器中集成了一个热敏电阻。在精密定位台上进行的验证实验表明所开发传感器具有高精度和高分辨率。此外，在标准压配式假体上进行的体外测试证明了该系统易于操作且可靠。
