Ebramzadeh E, Sangiorgio S N, Longjohn D B, Buhari C F, Morrison B J, Dorr L D
Biomechanics Laboratory, Los Angeles Orthopaedic Hospital and Department of Orthopaedics, University of California, Los Angeles - USA.
J Appl Biomater Biomech. 2003 Jan-Apr;1(1):76-83.
Stress shielding and load transfer to the femur following total hip arthroplasty have been studied extensively. A number of models have addressed the effects of surface finish of double-tapered, non-collared cemented stems on load transfer to the femur. However, a great number of cemented femoral stem designs in wide use today are not double tapered, and many, such as the Charnley, have collars. The effects of surface finish of such stems on load transfer to the femur are not completely understood. In this study, we measured the effects of surface finish of a straight, non-tapered cemented femoral stem, with and without a collar, in two stem sizes, on load transfer to the femur, using an in vitro laboratory model. Eight types of straight stems were fabricated, with polished or rough surfaces, with and without a collar, and in two sizes. All stems were based on the same template, and varied only in the desired combination of parameters studied. Three each of the eight unique stem types (total of 24 specimens) were cyclically loaded for 77,000 cycles at 1 Hz, alternating between walking and stair-climbing load profiles. Surface strains were measured at ten locations in each femur during designated initial and final periods. Of the three design variables, stem surface finish had the greatest effect on femoral surface strains. Specifically, compared to rough stems, with polished stems, mean proximal medial compressive strains were smaller, whereas mean distal medial compressive strains were greater. In contrast, on the anterior surface, mean proximal anterior tensile strains were greater, whereas mean distal anterior strains were smaller. All femoral surface strains increased with cyclic loading, however, strains increased at a greater rate with polished stems than with rough stems. Proximal medial strains were somewhat increased with the presence of a collar, however, these differences were small (< 100 microå ) and/or not statistically significant. Similarly, distal medial strains were increased with the presence of a collar but, again, the differences were not consistent (p > 0.16). Compared to large stems, with small stems, proximal medial compressive strains were greater. The results emphasize the importance cemented femoral stem surface roughness and the manner in which this changes stem-cement bond strength, affecting the distribution of stresses in the femur. This is an important consideration in the design of femoral stems. (Journal of Applied Biomaterials & Biomechanics 2003; 1: 76-83).
全髋关节置换术后股骨的应力屏蔽和负荷转移已得到广泛研究。许多模型探讨了双锥形、无领骨水泥柄表面光洁度对股骨负荷转移的影响。然而，当今广泛使用的大量骨水泥股骨柄设计并非双锥形，而且许多设计，如Charnley型，都有领圈。此类柄的表面光洁度对股骨负荷转移的影响尚未完全了解。在本研究中，我们使用体外实验室模型，测量了两种尺寸、有无领圈的直形、非锥形骨水泥股骨柄的表面光洁度对股骨负荷转移的影响。制作了八种类型的直柄，表面有抛光或粗糙处理，有无领圈，且有两种尺寸。所有柄均基于同一模板，仅在所研究参数的期望组合上有所不同。将八种独特柄类型中的每三种（共24个标本）在1 Hz频率下循环加载77,000次循环，在行走和爬楼梯负荷曲线之间交替。在每个股骨的指定初始和末期，在十个位置测量表面应变。在三个设计变量中，柄表面光洁度对股骨表面应变影响最大。具体而言，与粗糙柄相比，抛光柄的近端内侧平均压缩应变较小，而远端内侧平均压缩应变较大。相比之下，在前表面，近端前部平均拉伸应变较大，而远端前部平均应变较小。所有股骨表面应变均随循环加载而增加，然而，抛光柄的应变增加速率比粗糙柄更快。近端内侧应变在有领圈时略有增加，然而，这些差异较小（<100微应变）和/或无统计学意义。同样，远端内侧应变在有领圈时增加，但差异同样不一致（p>0.16）。与大柄相比，小柄的近端内侧压缩应变更大。结果强调了骨水泥股骨柄表面粗糙度的重要性以及其改变柄 - 骨水泥粘结强度从而影响股骨应力分布的方式。这是股骨柄设计中的一个重要考虑因素。（《应用生物材料与生物力学杂志》2003年；1：76 - 83）
