Norman T L, Yeni Y N, Brown C U, Wang Z
Department of Mechanical and Aerospace Engineering, Musculoskeletal Research Center, West Virginia University, Morgantown 26506-9196, USA.
Bone. 1998 Sep;23(3):303-6. doi: 10.1016/s8756-3282(98)00103-3.
The relationship between microdamage accumulation and bone fragility is not well understood. Previous work has demonstrated a positive relationship between microdamage and age in human cortical bone. Prior investigations have also demonstrated that fracture toughness decreases with age in the same bone. Based on these findings, the objective of this study was to test the hypothesis that a decrease in fracture toughness can be attributed to an increase in microdamage density. Microdamage parameters (density, surface density, and average crack length) were measured from bone taken from the shaft of the human femur and tibia and correlated with results from fracture toughness tests of the same bone. Results indicated that there was a weak but significant inverse relationship between fracture toughness and microdamage parameters for tension loading of the femur. These findings suggest that in vivo microdamage observable at the transmitted light level (100x) plays a secondary role to other contributory factors to decreased fracture toughness with age. Results also indicate that this relationship depends on bone ductility that apparently differs between the femur and the tibia. This study, in addition to prior investigations, suggests that crack size (microscopic vs. submicroscopic) and crack origin or type (in vivo vs. stress induced de novo) may influence the relationship between microdamage and bone toughness.
微损伤积累与骨脆性之间的关系尚未得到充分理解。先前的研究表明，人体皮质骨中微损伤与年龄呈正相关。先前的调查还表明，同一骨骼的断裂韧性会随着年龄的增长而降低。基于这些发现，本研究的目的是检验以下假设：断裂韧性的降低可归因于微损伤密度的增加。从人股骨和胫骨骨干获取的骨样本中测量微损伤参数（密度、表面密度和平均裂纹长度），并将其与同一骨骼的断裂韧性测试结果相关联。结果表明，在股骨拉伸载荷下，断裂韧性与微损伤参数之间存在微弱但显著的负相关关系。这些发现表明，在透射光水平（100倍）下可观察到的体内微损伤，在随年龄增长导致断裂韧性降低的其他促成因素中起次要作用。结果还表明，这种关系取决于股骨和胫骨明显不同的骨延展性。除先前的研究外，本研究表明裂纹尺寸（微观与亚微观）以及裂纹起源或类型（体内与应力诱导新生）可能会影响微损伤与骨韧性之间的关系。
