Milgrom Charles, Burr David B, Finestone Aharon S, Voloshin Arkady
Hebrew University School of Medicine, Tsameret, Ein Kerem, Jerusalem, Israel.
Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN, USA.
Bone. 2015 Sep;78:11-4. doi: 10.1016/j.bone.2015.04.033. Epub 2015 Apr 28.
Previous human in vivo tibial strain measurements from surface strain gauges during vigorous activities were found to be below the threshold value of repetitive cyclical loading at 2500 microstrain in tension necessary to reduce the fatigue life of bone, based on ex vivo studies. Therefore it has been hypothesized that an intermediate bone remodeling response might play a role in the development of tibial stress fractures. In young adults tibial stress fractures are usually oblique, suggesting that they are the result of failure under shear strain. Strains were measured using surface mounted unstacked 45° rosette strain gauges on the posterior aspect of the flat medial cortex just below the tibial midshaft, in a 48year old male subject while performing vertical jumps, staircase jumps and running up and down stadium stairs. Shear strains approaching 5000 microstrain were recorded during stair jumping and vertical standing jumps. Shear strains above 1250 microstrain were recorded during runs up and down stadium steps. Based on predictions from ex vivo studies, stair and vertical jumping tibial shear strain in the test subject was high enough to potentially produce tibial stress fracture subsequent to repetitive cyclic loading without necessarily requiring an intermediate remodeling response to microdamage.
基于体外研究，以往通过表面应变仪对人类在剧烈活动期间胫骨体内应变的测量发现，其低于2500微应变的重复性循环载荷阈值，而该阈值是降低骨疲劳寿命所需的拉伸阈值。因此，有人提出一种中间骨重塑反应可能在胫骨应力性骨折的发生中起作用。在年轻成年人中，胫骨应力性骨折通常是斜形的，这表明它们是剪切应变下失效的结果。在一名48岁男性受试者进行垂直跳跃、楼梯跳跃以及在体育场楼梯上上下跑时，使用表面安装的非堆叠45°应变花应变仪在胫骨中轴下方扁平内侧皮质的后侧测量应变。在楼梯跳跃和垂直站立跳跃期间记录到接近5000微应变的剪切应变。在体育场楼梯上上下跑期间记录到超过1250微应变的剪切应变。根据体外研究的预测，测试对象在楼梯和垂直跳跃时的胫骨剪切应变足够高，在重复性循环载荷后可能会导致胫骨应力性骨折，而不一定需要对微损伤产生中间重塑反应。
