Qin Y X, McLeod K J, Guilak F, Chiang F P, Rubin C T
Department of Orthopaedics, State University of New York at Stony Brook 11794-8181, USA.
J Orthop Res. 1996 Nov;14(6):862-70. doi: 10.1002/jor.1100140604.
The ability of shear strains to inhibit bony ingrowth was investigated by use of a transcortical porous-coated cylindrical plug implant in a functionally isolated turkey ulna model in which the mechanical loading environment could be accurately controlled and rigorously defined. The distribution of ingrowth at the bone-implant interface was quantified following 8 weeks of in vivo loading consisting of 100 seconds per day of a 20 Hz sinusoidal stimulus sufficient to cause a local peak strain of approximately 100 microstrain in the cortex at the bone-implant interface in four turkeys. A nonuniform but repeatable pattern of bony ingrowth, from 33 +/- 6 to 72 +/- 6% (mean +/- SE), was observed. The mechanical environment in the vicinity of the bone-implant interface was calculated using a three-dimensional elastic orthotropic finite element model. The general stress-strain state of the bone as predicted by the finite element model was validated in two additional turkeys using four three-element rosette strain gauges, while high resolution moiré interferometry was used to determine the mechanical state of the region immediately adjacent to the implant itself. Shear strains and stresses were evaluated at the interface and correlated to the pattern of bony ingrowth circumscribing the implant interface. Linear regressions between ingrowth and both shear strain and shear stress were negative, with the values of R = -0.75 and R = -0.78 (p < 0.001), respectively, indicating significant inhibition of ingrowth where shear components were maximal. These results suggest that the minimization of shear stress and strain components is a major determinant in achieving successful ingrowth of bone into a prosthesis.
通过在功能独立的火鸡尺骨模型中使用经皮质多孔涂层圆柱形塞植入物，研究了剪切应变抑制骨长入的能力。在该模型中，可以精确控制和严格定义机械加载环境。在四只火鸡的骨-植入物界面处，通过每天100秒的20Hz正弦刺激进行8周的体内加载后，对骨长入的分布进行了量化，该刺激足以在皮质中引起局部峰值应变约100微应变。观察到骨长入的模式不均匀但可重复，范围为33±6%至72±6%（平均值±标准误）。使用三维弹性正交各向异性有限元模型计算骨-植入物界面附近的力学环境。在另外两只火鸡中，使用四个三元应变片验证了有限元模型预测的骨的一般应力-应变状态，同时使用高分辨率云纹干涉测量法确定紧邻植入物本身区域的力学状态。在界面处评估了剪切应变和应力，并将其与围绕植入物界面的骨长入模式相关联。骨长入与剪切应变和剪切应力之间的线性回归均为负，R值分别为-0.75和-0.78（p<0.001），表明在剪切分量最大的地方，骨长入受到显著抑制。这些结果表明，将剪切应力和应变分量降至最低是实现骨成功长入假体的主要决定因素。
