Weinans H, Huiskes R, Grootenboer H J
Section of Biomechanics, University of Nijmegen, The Netherlands.
J Biomech Eng. 1994 Nov;116(4):393-400. doi: 10.1115/1.2895789.
Bone atrophy caused by stress-shielding may cause serious complications for the long-term fixation of hip stems. In particular, uncemented total hip arthroplasty is threatened by this problem, because the stems are usually larger and, as a consequence, stiffer than those of cemented implants. In the present study, the effects of fit and bonding characteristics of femoral hip stems were investigated, using the (nonlinear) finite element method in combination with adaptive bone remodeling theory to predict the bone density distribution in a bone or bone/implant configuration. Unknown parameters used in the theory, such as a reference equilibrium loading stimulus and a threshold (dead) zone of this stimulus, were established (triggered) by using the method to predict the density distributions in the natural femur and around fully coated uncemented implants. The computer simulation method can provide long term predictions of remodeling patterns around various implant configurations. Several cases were analyzed, whereby the coating conditions (fully, partly, or noncoated) and the fit characteristics (press fitted or overreamed) were varied. The computer predictions showed that partly coating can only significantly reduce bone atrophy relative to fully coated stems, when the coating is applied at a small region at the utmost proximal part of the stem. For smooth press-fit stems the predicted amount of bone loss (35 percent in the proximal medial region) was less than for a one-third proximally coated or a fully coated stem (50 to 54 percent predicted bone loss in the proximal medial region).(ABSTRACT TRUNCATED AT 250 WORDS)
应力屏蔽导致的骨萎缩可能会给髋关节柄的长期固定带来严重并发症。特别是，非骨水泥型全髋关节置换术受到这一问题的威胁，因为柄通常更大，因此比骨水泥型植入物更硬。在本研究中，利用（非线性）有限元方法结合适应性骨重塑理论，研究了股骨柄的配合和粘结特性对骨或骨/植入物结构中骨密度分布的影响，以预测骨密度分布。通过预测天然股骨和完全涂层非骨水泥型植入物周围的密度分布的方法，确定（触发）了该理论中使用的未知参数，如参考平衡加载刺激和该刺激的阈值（死）区。计算机模拟方法可以对各种植入物结构周围的重塑模式进行长期预测。分析了几种情况，其中涂层条件（完全、部分或无涂层）和配合特性（压配或扩孔）有所不同。计算机预测表明，当涂层仅应用于柄近端最小区域时，相对于完全涂层柄，部分涂层仅能显著减少骨萎缩。对于光滑压配柄，预测的骨丢失量（近端内侧区域为35%）低于近端三分之一涂层或完全涂层柄（近端内侧区域预测骨丢失量为50%至54%）。（摘要截短于250字）
