Tommasini Steven M, Nasser Philip, Jepsen Karl J
New York Center for Biomedical Engineering, CUNY Graduate School, Department of Biomedical Engineering, City College of New York, New York, NY, USA.
Bone. 2007 Feb;40(2):498-505. doi: 10.1016/j.bone.2006.08.012. Epub 2006 Oct 10.
Understanding how growth influences adult bone morphology and tissue quality should provide important insight into why females show a greater incidence of stress fractures early in life and fragility fractures later in life compared to males. The objective of this study was to test whether females acquire similar tissue-level mechanical properties as males by the time peak bone properties are established. Standardized beams of bone were machined from the tibial diaphyses of 14 young, adult females ranging in age from 22 to 46 years. Data for males (n=17, age=17-46 years) were taken from a prior study. Measures of tissue-level mechanical properties, including stiffness, strength, ductility, toughness, and damageability, were compared between sexes using t-tests. The relationship between cross-sectional morphology and tissue-level mechanical properties was also examined. Males and females showed nearly identical tissue-level mechanical properties. Both sexes also showed similar age-related degradation of mechanical properties and a similar relationship between cross-sectional morphology and tissue quality. However, for all body sizes, female tibiae were smaller relative to body size (i.e., less robust) compared to males. The results indicated that sex-specific growth patterns affected transverse bone size, but did not affect tissue-level mechanical properties. This, combined with the observation that young, adult female long bones are undersized relative to body size, suggests that adult females would be expected to accumulate more damage under intense loading compared to males. This may be a contributing factor to the greater incidence of stress fractures observed for female military recruits.
了解生长如何影响成年骨骼形态和组织质量，应能为为何女性在生命早期应力性骨折发生率更高、在生命后期脆性骨折发生率高于男性提供重要见解。本研究的目的是测试在峰值骨特性确立时，女性是否获得与男性相似的组织水平力学性能。从14名年龄在22至46岁的年轻成年女性的胫骨干中加工出标准化的骨梁。男性（n = 17，年龄 = 17 - 46岁）的数据取自先前的一项研究。使用t检验比较两性之间组织水平力学性能的测量值，包括刚度、强度、延展性、韧性和易损性。还研究了横截面形态与组织水平力学性能之间的关系。男性和女性显示出几乎相同的组织水平力学性能。两性在力学性能的年龄相关退化以及横截面形态与组织质量之间的关系方面也表现相似。然而，对于所有体型，与男性相比，女性胫骨相对于体型较小（即不够粗壮）。结果表明，性别特异性生长模式影响横向骨尺寸，但不影响组织水平力学性能。这一点，再加上观察到年轻成年女性长骨相对于体型尺寸过小，表明与男性相比，成年女性在高强度负荷下预计会积累更多损伤。这可能是女性新兵应力性骨折发生率更高的一个促成因素。
