Sangiorgio Sophia N, Ebramzadeh Edward, Longjohn Donald B, Dorr Lawrence D
Biomechanics Laboratory, Los Angeles Orthopaedic Hospital, 2400 South Flower Street, Los Angeles, CA 90007-2697, USA.
J Bone Joint Surg Am. 2004 Apr;86(4):813-20. doi: 10.2106/00004623-200404000-00022.
Although current designs of cemented femoral stems for total hip replacement include both those with and those without a flanged shape at the proximal end, the influence of anteroposterior dorsal flanges on the fixation of the stem is not completely understood. The purpose of this study was to assess the effects of flanges on femoral stem stability and load transfer to the femur with use of an in vitro model.
We measured femoral surface strains and three-dimensional micromotion in synthetic femora under cyclic loading with four types of stems: those with flanges and those without flanges in two sizes each. The four types of stems were otherwise identical; that is, all of them were straight, polished, and collarless. Stem-cement micromotion measurements and strain measurements were repeated with three stems of each type, whereas bone-cement micromotion measurements were made with one stem of each type.
Flanges had a greater influence on femoral strains and micromotion than did the difference in the cement thickness resulting from the different stem sizes. Specifically, the flanged stems produced greater strains on the medial femoral surface but smaller strains on the anterior surface than did the non-flanged stems. Flanged stems achieved tighter mechanical interlock within the cement, but these stems increased bone-cement micromotion. Specifically, the motion per cycle of flanged stems within the cement mantle was smaller than that of non-flanged stems, whereas the motion per cycle of the cement mantle within the femoral canal was greater with the flanged stems than with the non-flanged stems.
Flanges on a total hip femoral stem increase the interlock between the stem and the cement and decrease the proximal-medial stress-shielding. However, these advantages occur with increased bone-cement interface motion, which may be detrimental to the survival of the implant.
尽管目前用于全髋关节置换的骨水泥型股骨柄设计包括近端有和没有凸缘形状的两种，但前后背侧凸缘对股骨柄固定的影响尚未完全明确。本研究的目的是使用体外模型评估凸缘对股骨柄稳定性以及向股骨的载荷传递的影响。
我们在循环加载下，使用四种类型的股骨柄（每种类型有带凸缘和不带凸缘两种尺寸）测量合成股骨的表面应变和三维微动。这四种类型的股骨柄在其他方面相同，即均为直柄、表面光滑且无领圈。每种类型的三个股骨柄重复进行柄 - 骨水泥微动测量和应变测量，而每种类型的一个股骨柄进行骨 - 骨水泥微动测量。
与不同股骨柄尺寸导致的骨水泥厚度差异相比，凸缘对股骨应变和微动影响更大。具体而言，带凸缘的股骨柄在内侧股骨表面产生的应变更大，但在前表面产生的应变小于不带凸缘的股骨柄。带凸缘的股骨柄在骨水泥内实现了更紧密的机械嵌合，但这些股骨柄增加了骨 - 骨水泥微动。具体来说，带凸缘的股骨柄在骨水泥壳内每周期的运动小于不带凸缘的股骨柄，而带凸缘的股骨柄在股骨髓腔内骨水泥壳每周期的运动大于不带凸缘的股骨柄。
全髋关节股骨柄上的凸缘增加了柄与骨水泥之间的嵌合，并减少了近端内侧应力遮挡。然而，这些优点伴随着骨 - 骨水泥界面运动增加而出现，这可能对植入物的存活不利。
