Diab Tamim, Vashishth Deepak
Department of Biomedical Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
Bone. 2007 Mar;40(3):612-8. doi: 10.1016/j.bone.2006.09.027. Epub 2006 Nov 13.
In vivo, microdamage occurs in the form of linear microcracks and diffuse damage. However, it is unknown whether the age-related changes in bone quality predispose bone to form one type of damage morphology over the other during in vivo loading. In this study, histological and histomorphometrical analyses were conducted on transverse cross sections, obtained from the tibiae of aging human bone (age 19 to 89), to investigate the in vivo accumulation and localization of damage morphologies. The results demonstrate that old donor bone (83+/-3 years) contains more linear microcracks than younger donor bone in the cortices predominantly subjected to compressive (p<0.01) and tensile loading (p<0.01). In contrast, young donor bone (40+/-10 years) contains more diffuse damage than older donor bone in the cortex predominantly subjected to tensile loading (p<0.01). The formation of damage morphology showed no correlation with bone geometry parameters and exhibited distinct preferences with bone microstructure. Linear microcracks formed in the interstitial bone (p<0.01) and were either trapped or arrested by the microstructural interfaces (cement line and lamellar interface) (p<0.05). Areas of diffuse damage, however, were preferentially associated with secondary osteonal bone (p<0.01) and had no relationship with the microstructural interfaces (p<0.01). Based upon these findings, we conclude that age-related changes in bone microstructure, but not bone geometry, play a key role in the propensity of old donors to form linear microcrack over diffuse damage under in vivo loading conditions.
在体内，微损伤以线性微裂纹和弥散性损伤的形式出现。然而，尚不清楚骨质量随年龄的变化是否会使骨骼在体内加载过程中更容易形成一种损伤形态而非另一种。在本研究中，对取自19至89岁老年人胫骨的横切面进行了组织学和组织形态计量学分析，以研究损伤形态在体内的积累和定位。结果表明，在主要承受压缩力（p<0.01）和拉力（p<0.01）的皮质骨中，老年供体骨（83±3岁）比年轻供体骨含有更多的线性微裂纹。相比之下，在主要承受拉力的皮质骨中，年轻供体骨（40±10岁）比老年供体骨含有更多的弥散性损伤（p<0.01）。损伤形态的形成与骨几何参数无关，而对骨微观结构有明显偏好。线性微裂纹在骨小梁间骨中形成（p<0.01），并被微观结构界面（黏合线和板层界面）捕获或阻止（p<0.05）。然而，弥散性损伤区域优先与继发性骨单位骨相关（p<0.01），且与微观结构界面无关（p<0.01）。基于这些发现，我们得出结论，在体内加载条件下，骨微观结构而非骨几何形状随年龄的变化在老年供体形成线性微裂纹而非弥散性损伤的倾向中起关键作用。
