Skedros John G, Sorenson Scott M, Takano Yuichi, Turner Charles H
Department of Orthopaedic Surgery, University of Utah, and Bone and Joint Research Laboratory, Department of Veteran's Affairs Medical Center, Salt Lake City, UT 84107, USA.
Bone. 2006 Jul;39(1):143-51. doi: 10.1016/j.bone.2005.12.007. Epub 2006 Feb 3.
In limb bone diaphyses, it is hypothesized that collagen and extra-fibrillar mineral are aligned differently in relatively simple loading conditions (e.g., habitual longitudinal compression) when compared to complex or potentially deleterious strain environments (e.g., habitual shear or tension). These putative differences in collagen/mineral organization might be adaptations that enhance toughness and fatigue resistance by controlling the direction of microdamage propagation. This study examined relationships between the non-uniform strain distribution of wild deer calcanei and elastic anisotropy of cortical bone specimens in three preparations: (1) demineralized (collagen only), (2) deproteinized (mineral only), and (3) untreated. Using simulated functional loading, the following strain data were obtained from the dorsal "compression", plantar "tension", and medial and lateral ("neutral axis") cortices of one calcaneus of each of seven pairs: (1) peak strain magnitude, (2) prevalent/predominant strain mode (compression, tension, shear), and (3) principal strain orientation with respect to the bone's long axis. In the contralateral calcanei, elastic anisotropy ratios (ARs) were calculated using acoustic velocity (longitudinal and transverse) measurements from a pair of orthogonally sliced specimens (representing each of three preparation types) from each cortex. In a separate set of seven adult calcanei, predominant collagen fiber orientation (CFO) was measured using circularly polarized light (CPL) in the four cortical locations. Results showed that, in general, elastic anisotropy was significant in each region, with ARs being significantly different from isotropy (where AR=1.0). Compared to CFO, mineral orientation more strongly influenced this anisotropy, which was most notable in the plantar "tension" cortex. High correlations (r values from -0.675 to -0.734, P<0.05) were found between collagen anisotropy obtained from acoustic data when compared to the CPL data. Significant correlations of mineral and collagen anisotropy were also found between strain mode, magnitude, and orientation (all r values approximately -0.750). The habitual compression, tension, and shear (neutral axis) regions also had different collagen/mineral organizations, which may be important in accommodating the well-known disparity in the mechanical properties of bone in these loading modes.
在四肢骨骨干中，有这样一种假说：与复杂或潜在有害的应变环境（如习惯性剪切或拉伸）相比，在相对简单的负荷条件下（如习惯性纵向压缩），胶原蛋白和纤维外矿物质的排列方式有所不同。胶原蛋白/矿物质组织的这些假定差异可能是一种适应性变化，通过控制微损伤传播的方向来增强韧性和抗疲劳性。本研究在三种制备状态下，研究了野生鹿跟骨的非均匀应变分布与皮质骨标本弹性各向异性之间的关系：（1）脱矿质（仅含胶原蛋白），（2）脱蛋白（仅含矿物质），以及（3）未处理。使用模拟功能负荷，从七对跟骨中每对跟骨的一个跟骨的背侧“压缩”、足底“拉伸”以及内侧和外侧（“中性轴”）皮质获得了以下应变数据：（1）峰值应变大小，（2）普遍/主要应变模式（压缩、拉伸、剪切），以及（3）相对于骨长轴的主应变方向。在对侧跟骨中，使用来自每个皮质的一对正交切片标本（代表三种制备类型中的每一种）的声速（纵向和横向）测量值计算弹性各向异性比（ARs）。在另一组七个成年跟骨中，使用圆偏振光（CPL）测量了四个皮质位置的主要胶原纤维取向（CFO）。结果表明，总体而言，每个区域的弹性各向异性都很显著，ARs与各向同性（AR = 1.0）有显著差异。与CFO相比，矿物质取向对这种各向异性影响更大，这在足底“拉伸”皮质中最为明显。与CPL数据相比，从声学数据获得的胶原蛋白各向异性之间发现了高度相关性（r值在 -0.675至 -0.734之间，P < 0.05）。在应变模式、大小和方向之间也发现了矿物质和胶原蛋白各向异性的显著相关性（所有r值约为 -0.750）。习惯性压缩、拉伸和剪切（中性轴）区域也有不同的胶原蛋白/矿物质组织，这对于适应这些负荷模式下骨力学性能中众所周知的差异可能很重要。
