Gefen Amit, Neulander Ron
Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv, Israel.
J Appl Biomech. 2007 Aug;23(3):230-7. doi: 10.1123/jab.23.3.230.
Bone is a living tissue, which undergoes continuous renewal to repair local defects. Two separate processes, adaptation and remodeling, are involved when a defect appears. The defect produces stress concentrations that provoke regional adaptation, and is gradually repaired, first by resorption and then by deposition of new bone. Using a mathematical formulation of the adaptation mechanism in trabeculae of cancellous bone, we hypothesize that in some cases, where a microcrack is small enough relative to the dimensions of the trabecula, the adaptation response of the whole trabecula may be sufficient to regain homeostatic mechanical conditions (with no need for a remodeling process). The simulation results showed that for trabeculae with nominal length of 900 microm and nominal thickness of 80-800 microm, a microcrack with minimal length of 48 microm and minimal depth of 13% of the trabecula's thickness was required to initiate a remodeling process. A longer (100 microm) but shallower (depth of 7% of the trabecula's thickness) crack also triggered remodeling. These computational results support our hypothesis that when a microcrack small enough relative to the dimensions of the trabecula occurs, adaptation of the whole trabecula may be sufficient to regain homeostatic mechanical conditions with no need for a local remodeling process.
骨骼是一种活组织，会不断更新以修复局部缺损。当出现缺损时，会涉及两个独立的过程，即适应性改变和重塑。缺损会产生应力集中，引发局部适应性改变，并逐渐得到修复，首先是通过吸收，然后是新骨沉积。通过对松质骨小梁适应性机制进行数学公式化，我们推测在某些情况下，当微裂纹相对于小梁尺寸足够小时，整个小梁的适应性反应可能足以恢复稳态力学条件（无需重塑过程）。模拟结果表明，对于标称长度为900微米、标称厚度为80 - 800微米的小梁，需要最小长度为48微米、最小深度为小梁厚度13%的微裂纹才能启动重塑过程。一条更长（100微米）但更浅（深度为小梁厚度7%）的裂纹也会引发重塑。这些计算结果支持了我们的假设，即当出现相对于小梁尺寸足够小的微裂纹时，整个小梁的适应性改变可能足以恢复稳态力学条件，而无需局部重塑过程。
