Brown T D, Pope D F, Hale J E, Buckwalter J A, Brand R A
Department of Orthopaedic Surgery, University of Iowa, Iowa City 52242.
J Orthop Res. 1991 Jul;9(4):559-67. doi: 10.1002/jor.1100090412.
Contact stress distributions were studied in vitro for 13 dog knees, with full-thickness osteochondral defects drilled in the weight-bearing area of both femoral condyles. Diameters of the circular defects were concentrically enlarged from 1 to 7 mm. Digitally-imaged Fuji film was used to record cartilage contact stress distribution on femoral condyles for each increment of defect diameter. All specimens showed at least some tendency for contact stress concentration at the rim of the defects. However, detailed distributions had large interspecimen variability and, within a given specimen, contact stress distributions became progressively more nonuniform around the defect rim as the diameter was enlarged. Averaged over the full series of 26 condyles, circumferential mean cartilage contact stress around the defect rim was only moderately higher (by 10-30%) than intact surface's peak local contact stress [series average = 6.2 mega pascals (MPa)]. Maximal rim stress concentration occurred for 2 mm defects, there being a consistent trend toward mild rim stress decrease with further defect enlargement. Such modest contact stress elevations, per se, are probably insufficient to inhibit defect repair or to cause degeneration of surrounding cartilage. However, near the defect rim (for all diameters), the radial component of the gradient of contact stress (i.e., radial-direction variation of contact stress) was consistently elevated by an order of magnitude above that for intact, condyle articular cartilage.
对13个犬膝关节进行了体外接触应力分布研究，在双侧股骨髁的负重区钻了全层骨软骨缺损。圆形缺损的直径从1毫米到7毫米呈同心扩大。使用数字成像的富士胶片记录每个缺损直径增量下股骨髁上的软骨接触应力分布。所有标本在缺损边缘均至少表现出一定程度的接触应力集中趋势。然而，详细的分布在标本间存在很大差异，并且在给定标本内，随着直径增大，缺损边缘周围的接触应力分布逐渐变得更加不均匀。在整个26个髁的系列中平均来看，缺损边缘周围的周向平均软骨接触应力仅比完整表面的局部峰值接触应力略高（高10%-30%）[系列平均值 = 6.2兆帕（MPa）]。2毫米缺损时出现最大边缘应力集中，随着缺损进一步扩大，边缘应力有持续轻度降低的趋势。这种适度的接触应力升高本身可能不足以抑制缺损修复或导致周围软骨退变。然而，在缺损边缘附近（对于所有直径），接触应力梯度的径向分量（即接触应力在径向方向的变化）始终比完整的髁关节软骨升高一个数量级。
