Exponent, Inc., Philadelphia, Pennsylvania 19140, USA.
J Arthroplasty. 2009 Oct;24(7):1137-42. doi: 10.1016/j.arth.2008.08.005. Epub 2008 Sep 26.
Valgus alignment of femoral resurfacing components has been advocated to reduce proximal femur loading and thus minimize the risk for femoral neck fractures. However, such reduction in loading may exacerbate undesirable stress shielding. This study examined the effect of extreme implant orientations (+/-15 degrees ) and stem canal overreaming on initial bone remodeling stimulus using finite element models. The changes in implant-cement interface stresses due to implant alignment were also evaluated. The valgus model showed increased initial bone resorption stimulus, which extended distally and peripherally around the femoral neck. The peak implant-cement interface shear stress for the varus model was 10.9 MPa, exceeding the interface shear strength. Overreaming of the stem canal eliminated distal tip loading, but proximal stress shielding was still unavoidable. These data show bone loading and interface fixation trends emanating from valgus and varus implant positions that will be of interest to practicing physicians.
提倡股骨表面置换组件的外翻对准，以减少股骨近端的负荷，从而最大限度地降低股骨颈骨折的风险。然而，这种负荷的减少可能会加剧不良的应力遮挡。本研究使用有限元模型研究了极端植入物取向（±15 度）和髓腔扩孔对初始骨重塑刺激的影响。还评估了由于植入物对准引起的植入物-水泥界面应力的变化。外翻模型显示初始骨吸收刺激增加，这种刺激向股骨颈的远端和周围延伸。内翻模型的峰值植入物-水泥界面剪切应力为 10.9 MPa，超过了界面剪切强度。髓腔扩孔消除了尖端的远端加载，但近端的应力遮挡仍然不可避免。这些数据显示了从外翻和内翻植入位置产生的骨负荷和界面固定趋势，这将引起临床医生的兴趣。
