Quenneville Cheryl E, Austman Rebecca L, King Graham J W, Johnson James A, Dunning Cynthia E
Department of Mechanical and Materials Engineering, The University of Western Ontario, London, Ontario, Canada.
J Hand Surg Am. 2008 Jul-Aug;33(6):927-31. doi: 10.1016/j.jhsa.2008.02.020.
Anterior flanges have been added to the humeral components of some total elbow arthroplasty systems to improve load transfer to the humerus and thereby reduce stress shielding in an effort to decrease the incidence of loosening. Either a wedge of bone or bone cement is placed between the anterior surface of the humerus and the flange. The purpose of this study was to quantify the cortical strains in the humerus as a function of these implantation options.
Five cadaveric distal humeri were fitted with bending strain gauges at 2 levels on the diaphysis and axial strain gauges at 1 level. Each specimen was subjected to cantilevered bending and axial compressive loads. Subsequently, a humeral prosthesis was inserted, and testing was repeated with 3 materials behind the flange: no graft (simulating an implant with no flange), a wafer of cancellous bone, and a block of bone cement.
The presence of an anterior flange had no significant effect on load transfer through the distal humerus regardless of graft material. This was found to be consistent for both bending and axial loading modes at all gauge levels; however, the supporting collar effect of the implant may have influenced axial compression results.
These results suggest that for the Latitude humeral component studied, the placement of bone or bone cement behind the anterior flange may not influence the cortical strains in the distal humerus under bending loads. However, a flange may still influence cortical strains using another implant with different geometric and material properties than the currently studied design.
一些全肘关节置换系统的肱骨组件增加了前凸缘，以改善向肱骨的负荷传递，从而减少应力遮挡，降低松动发生率。在肱骨前表面和凸缘之间放置一块骨楔或骨水泥。本研究的目的是量化肱骨皮质应变与这些植入方式的关系。
对5具尸体的肱骨远端进行如下操作：在骨干的2个水平安装弯曲应变片，在1个水平安装轴向应变片。对每个标本施加悬臂弯曲和轴向压缩载荷。随后，插入一个肱骨假体，并用凸缘后方的3种材料重复测试：无移植骨（模拟无凸缘的植入物）、一块松质骨薄片和一块骨水泥。
无论移植材料如何，前凸缘的存在对通过肱骨远端的负荷传递均无显著影响。在所有应变片水平上，弯曲和轴向加载模式下均得到一致结果；然而，植入物的支撑环效应可能影响了轴向压缩结果。
这些结果表明，对于所研究的Latitude肱骨组件，在弯曲载荷下，在前凸缘后方放置骨或骨水泥可能不会影响肱骨远端的皮质应变。然而，与当前研究设计相比，使用具有不同几何和材料特性的另一种植入物时，凸缘仍可能影响皮质应变。
