Riggs C M, Vaughan L C, Evans G P, Lanyon L E, Boyde A
Department of Large Animal Clinical Science, Royal Veterinary College, North Mymms, Herts, UK.
Anat Embryol (Berl). 1993 Mar;187(3):239-48. doi: 10.1007/BF00195761.
Mechanical test specimens were prepared from the cranial and caudal cortices of radii from eight horses. These were subjected to destructive tests in either tension or compression. The ultimate stress, elastic modulus and energy absorbed to failure were calculated in either mode of loading. Analysis was performed on the specimens following mechanical testing to determine their density, mineral content, mineral density distribution and histological type. A novel technique was applied to sections from each specimen to quantify the predominant collagen fibre orientation of the bone near the plane of fracture. The collagen map for each bone studied was in agreement with the previously observed pattern of longitudinal orientation in the cranial cortex and more oblique to transverse collagen in the caudal cortex. Bone from the cranial cortex had a significantly higher ultimate tensile stress (UTS) than that from the caudal cortex (160 MPa vs 104 MPa; P < 0.001) though this trend was reversed in compression, the caudal cortex becoming relatively stronger (185 MPa vs 217 MPa; P < 0.01). Bone from the cranial cortex was significantly stiffer than that from the caudal cortex both in tension (22 GPa vs 15 GPa; P < 0.001) and compression (19 GPa vs 15 GPa; P < 0.01). Of all the histo-compositional variables studied, collagen fibre orientation was most closely correlated with mechanical properties, accounting for 71% of variation in ultimate tensile stress and 58% of variation in the elastic modulus. Mineral density and porosity were the only other variables to show any significant correlation with either UTS or elastic modulus. The variations in mechanical properties around the equine radius, which occur in close association with the different collagen fibre orientations, provide maximal safety factors in terms of ultimate stress, yet contribute to greater bending of the bone as it is loaded during locomotion, and thus lower safety factors through the higher strains this engenders.
从八匹马的桡骨的颅侧和尾侧皮质制备机械测试样本。这些样本在拉伸或压缩状态下进行破坏性测试。在每种加载模式下计算极限应力、弹性模量和破坏时吸收的能量。在机械测试后对样本进行分析，以确定其密度、矿物质含量、矿物质密度分布和组织学类型。一种新技术应用于每个样本的切片，以量化骨折平面附近骨的主要胶原纤维取向。所研究的每块骨的胶原图谱与先前观察到的颅侧皮质纵向取向模式以及尾侧皮质中更倾斜至横向胶原的模式一致。颅侧皮质的骨比尾侧皮质的骨具有显著更高的极限拉伸应力（UTS）（160MPa对104MPa；P<0.001），尽管在压缩时这种趋势相反，尾侧皮质变得相对更强（185MPa对217MPa；P<0.01）。颅侧皮质的骨在拉伸（22GPa对15GPa；P<0.001）和压缩（19GPa对15GPa；P<0.01）方面都比尾侧皮质的骨显著更硬。在所有研究的组织成分变量中，胶原纤维取向与力学性能最密切相关，占极限拉伸应力变化的71%和弹性模量变化的58%。矿物质密度和孔隙率是仅有的与UTS或弹性模量显示出任何显著相关性的其他变量。马桡骨周围力学性能的变化与不同的胶原纤维取向密切相关，就极限应力而言提供了最大安全系数，但在运动加载时导致骨更大程度的弯曲，因此通过由此产生的更高应变导致安全系数降低。
