Pastrav L C, Jaecques S V N, Mulier M, Van Der Perre G
Division of Biomechanics and Engineering Design (BMGO), Katholieke Universiteit Leuven - Belgium.
J Appl Biomater Biomech. 2008 Jan-Apr;6(1):23-9.
Vibration analysis is a non-destructive testing technique, which has a potential to assess the mechanical properties of the stem/femur system in total hip replacement (THR). Different methods based on vibration analysis have already been successfully used to determine bone mechanical properties, to monitor fracture healing, and to quantify the fixation of dental implants. This paper describes an in vitro study of the change in the frequency response function (FRF) of the hip stem/femur structure during implant insertion. At successive insertion stages, the FRF of the system was measured by impulse excitation on the prosthesis neck, in the range 0-5000 Hz. To quantify the difference between two successive FRF spectra, the Pearson's correlation coefficient and the cross correlation function were used. The stiffness of the implant/bone system varies during insertion, which results in a change in FRF, especially in the range of higher frequencies. If the FRF spectrum shifts to the right, then the stiffness of the implant/bone connection increases and, consequently, the stability of the implant increases as well. If the FRF does not change between two successive insertion stages, then the mechanical properties of the prosthesis-femur structure does not change; therefore, the stem-bone connection is stable and the insertion should stop to avoid intra-operative fractures. Based on the obtained results, a per-operative protocol based on FRF analysis can be designed to assess the stability of a cementless hip prosthesis, and to detect the insertion end point.
振动分析是一种无损检测技术，它有潜力评估全髋关节置换（THR）中柄/股骨系统的力学性能。基于振动分析的不同方法已成功用于确定骨力学性能、监测骨折愈合以及量化牙种植体的固定情况。本文描述了一项关于植入物插入过程中髋柄/股骨结构频率响应函数（FRF）变化的体外研究。在连续的插入阶段，通过在假体颈部进行脉冲激励，在0 - 5000Hz范围内测量系统的FRF。为了量化两个连续FRF谱之间的差异，使用了皮尔逊相关系数和互相关函数。植入物/骨系统的刚度在插入过程中会发生变化，这会导致FRF的改变，尤其是在较高频率范围内。如果FRF谱向右移动，那么植入物/骨连接的刚度增加，因此植入物的稳定性也会增加。如果在两个连续的插入阶段之间FRF没有变化，那么假体 - 股骨结构的力学性能没有改变；因此，柄 - 骨连接是稳定的，插入应停止以避免术中骨折。基于所获得的结果，可以设计一种基于FRF分析的术中方案，以评估非骨水泥型髋关节假体的稳定性，并检测插入终点。
