Tommasini Steven M, Nasser Philip, Schaffler Mitchell B, Jepsen Karl J
New York Center for Biomedical Engineering, CUNY Graduate School, Department of Biomedical Engineering, City College of New York, New York, USA.
J Bone Miner Res. 2005 Aug;20(8):1372-80. doi: 10.1359/JBMR.050326. Epub 2005 Mar 28.
Biomechanical properties were assessed from the tibias of 17 adult males 17-46 years of age. Tissue-level mechanical properties varied with bone size. Narrower tibias were comprised of tissue that was more brittle and more prone to accumulating damage compared with tissue from wider tibias.
A better understanding of the factors contributing to stress fractures is needed to identify new prevention strategies that will reduce fracture incidence. Having a narrow (i.e., more slender) tibia relative to body mass has been shown to be a major predictor of stress fracture risk and fragility in male military recruits and male athletes. The intriguing possibility that slender bones, like those shown in animal models, may be composed of more damageable material has not been considered in the human skeleton.
Polar moment of inertia, section modulus, and antero-posterior (AP) and medial-lateral (ML) widths were determined for tibial diaphyses from 17 male donors 17-46 years of age. A slenderness index was defined as the inverse ratio of the section modulus to tibia length and body weight. Eight prismatic cortical bone samples were generated from each tibia, and tissue-level mechanical properties including modulus, strength, total energy, postyield strain, and tissue damageability were measured by four-point bending from monotonic (n = 4/tibia) and damage accumulation (n = 4/tibia) test methods. Partial correlation coefficients were determined between each geometrical parameter and each tissue-level mechanical property while taking age into consideration.
Significant correlations were observed between tibial morphology and the mechanical properties that characterized tissue brittleness and damageability. Positive correlations were observed between measures of bone size (AP width) and measures of tissue ductility (postyield strain, total energy), and negative correlations were observed between bone size (moment of inertia, section modulus) and tissue modulus.
The correlation analysis suggested that bone morphology could be used as a predictor of tissue fragility and stress fracture risk. The average mechanical properties of cortical tissue varied as a function of the overall size of the bone. Therefore, under extreme loading conditions (e.g., military training), variation in bone quality parameters related to damageability may be a contributing factor to the increased risk of stress fracture for individuals with more slender bones.
对17名年龄在17至46岁的成年男性的胫骨进行了生物力学特性评估。组织水平的力学特性随骨骼大小而变化。与较宽胫骨的组织相比，较窄胫骨的组织更脆，更容易积累损伤。
需要更好地了解导致应力性骨折的因素，以确定能降低骨折发生率的新预防策略。相对于体重而言，胫骨较窄（即更细长）已被证明是男性新兵和男性运动员应力性骨折风险和脆性的主要预测指标。在人类骨骼中，尚未考虑到像动物模型中所示的细长骨骼可能由更易受损的材料组成这一有趣的可能性。
测定了17名年龄在17至46岁男性供体胫骨骨干的极惯性矩、截面模量以及前后（AP）和内外侧（ML）宽度。细长指数定义为截面模量与胫骨长度和体重的反比。从每根胫骨中制备8个棱柱形皮质骨样本，并通过单调（n = 4/胫骨）和损伤累积（n = 4/胫骨）测试方法的四点弯曲来测量包括模量、强度、总能量、屈服后应变和组织损伤性在内的组织水平力学特性。在考虑年龄的情况下，确定每个几何参数与每个组织水平力学特性之间的偏相关系数。
观察到胫骨形态与表征组织脆性和损伤性的力学特性之间存在显著相关性。在骨骼大小测量值（AP宽度）与组织延展性测量值（屈服后应变、总能量）之间观察到正相关，而在骨骼大小（惯性矩、截面模量）与组织模量之间观察到负相关。
相关性分析表明，骨骼形态可作为组织脆性和应力性骨折风险的预测指标。皮质组织的平均力学特性随骨骼的整体大小而变化。因此，在极端负荷条件下（如军事训练），与损伤性相关的骨质量参数变化可能是骨骼更细长个体应力性骨折风险增加的一个促成因素。
