Widmer K H, Zurfluh B, Morscher E W
Orthopädische Universitätsklinik und Labor für Orthopädische Biomechanik, Felix Platter-Spital Basel.
Orthopade. 1997 Feb;26(2):181-9. doi: 10.1007/s001320050084.
The implantation of an endoprosthetic socket into the acetabulum alters the mechanical stresses in the periacetabular region in a significant manner compared with the natural hip joint. In this way, a remodelling process is initiated. Primary stability to achieve osseointegration and a loading of the acetabulum owing to the biomechanical interaction between cup and bone that is similar to the natural joint, are important prerequisites for a long-term bony integration of the implant. Therefore, the intra-articular pressure distribution in eight hip joints of fresh-frozen human pelvic cadavers and in the bone/implant interface of two press-fit cups was investigated using pressure-sensitive Prescale films. A modular cup with a pure hemispherical shape (PCA cup) and a monoblock cup with a biradial surface and flattening of the pole (press-fit cup) were tested. Loads of up to twice body weight were introduced into the sacrum, simulating a single-leg stance with the hip in neutral flexion. The results were extracted from the pressure prints applying digital image processing methods. It was demonstrated that intra-articular contact occurs over the whole articular surface of the joint, with contact areas between 39.0% and 56.9% of the hemisphere, showing zones of higher pressures where the acetabulum is supported by the iliac, ischial and pubic bone. The biradial press-fit cup showed mean contact areas of 44.7% of its surface when inserted under press-fit only. This area was enlarged to 53.0% and to 64.2% with increasing load. The corresponding figures for the PCA cup are 45.1%, 48.9% and 57.1%. The low-profile PCA cup produces a small band of high pressure near the periphery, and with increasing load its pole area comes into contact with the acetabular fossa. Occasionally, irregular gaps do occur. The press-fit cup enlarges the contact area from the periphery to the pole within its optimised biradial contact zone until the lunar surface is loaded. The acetabular fossa remains unloaded owing to the flattening of the pole. This load distribution is close to that of the natural hip joint. The pressure distribution of both cups is also characterised by three zones at the iliac, ischial and pubic bones showing a higher load transmission.
与天然髋关节相比，将髋臼内假体植入髋臼会显著改变髋臼周围区域的机械应力。通过这种方式，启动了一个重塑过程。实现骨整合所需的初始稳定性以及由于髋臼杯与骨骼之间的生物力学相互作用而导致的髋臼负荷（类似于天然关节），是植入物长期骨整合的重要前提条件。因此，使用压敏Prescale薄膜研究了新鲜冷冻人体骨盆尸体的八个髋关节以及两个压配杯的骨/植入物界面中的关节内压力分布。测试了具有纯半球形形状的模块化杯（PCA杯）和具有双径向表面且极部扁平化的整体式杯（压配杯）。将高达两倍体重的负荷施加到骶骨上，模拟髋关节处于中立屈曲位的单腿站立。使用数字图像处理方法从压力印记中提取结果。结果表明，关节内接触发生在关节的整个关节表面，接触面积占半球的39.0%至56.9%，在髋臼由髂骨、坐骨和耻骨支撑的部位显示出较高压力区域。双径向压配杯仅在压配插入时其表面平均接触面积为44.7%。随着负荷增加，该面积扩大到53.0%和64.2%。PCA杯的相应数字分别为45.1%、48.9%和57.1%。低轮廓PCA杯在周边附近产生一小条高压带，随着负荷增加，其极部区域与髋臼窝接触。偶尔会出现不规则间隙。压配杯在其优化的双径向接触区内从周边到极部扩大接触面积，直到月面加载。由于极部扁平化，髋臼窝保持无负荷状态。这种负荷分布接近天然髋关节的负荷分布。两种髋臼杯的压力分布还具有在髂骨、坐骨和耻骨处的三个区域，显示出较高的负荷传递。
