Doctoral Dissertation: Collagen Fiber Orientation and Locomotor Loading in Primates

这项研究考察了骨骼的一些重要的微观结构细节。这一结果可能会提高我们对该组织的微观结构以及在直立行走和跑步过程中施加在该组织上的力是如何分布的理解。胶原纤维是骨骼微结构的重要组成部分。它们的方向反映了骨骼在沉积期间所承受的力的类型。通过对组织切片的显微分析，这项研究将提供关于行走和跑步过程中施加在人类骨骼特定区域的力的新数据。首先将审查练习高度专门化运动形式的动物的骨骼微结构，这些动物已经通过其他手段，如体内应变仪检查进行了研究。这将允许详细的方法标准化，也可以作为一种测试胶原蛋白取向能力的手段，以准确反映骨力。然后，它将定性和定量地评估取自骨骼高度局部化部分的人类和非人类灵长类骨骼中胶原纤维的方向。第一个要研究的地点是长臂猿前肢。吉本斯练习臂位，这是一种运动模式，身体由每个前肢交替悬挂。长臂猿尺骨的应变主要是拉伸，而前臂的伴骨，即桡骨，则主要是弯曲的。这些力特征应该会特别影响两块骨骼中的胶原蛋白方向。这项研究将量化和定性长臂猿前肢的胶原纤维方向，并将结果与肢体上测量的应变进行比较。这项研究中将调查的第二个地点是人类和黑猩猩的股骨颈。人类股骨颈的独特之处在于其上部有一层非常薄的皮质骨壳。这一区域对骨质疏松导致的骨丢失非常敏感，也是老年女性骨折的常见部位。因此，更好地了解这一区域的部队和结构可能具有重大意义。与人类的股骨颈不同，黑猩猩的股骨颈与众不同，因为它们的上颈有一层厚厚的皮质骨层。人类和黑猩猩皮质骨发育的不同模式被认为是由于它们在各自的运动模式中所受的力，以及髋部不同的肌肉解剖的结果。人类练习两足运动，在此过程中，臀部肌肉的功能是将身体稳定在骨盆上，但黑猩猩很少会两足行走。因此，黑猩猩的臀部肌肉结构在解剖学上与人类的不同。在人类中，髋部肌肉(外展肌)被认为可以缓解股骨颈上部的力量。这导致该区域只有最少的骨形成，这可能是人类股骨典型的薄皮质壳的主要原因。然而，黑猩猩的臀部肌肉没有那么强的外展功能，因此允许他们的股骨颈承受更大的力，导致皮质更厚。通过研究黑猩猩和人类股骨颈中胶原纤维的取向，这项研究将确定这两个物种的股骨颈中发生了什么力。这些结果将检验皮质骨的分布是否是黑猩猩和人类股骨颈上不同作用力的结果。这项研究还将检查骨骼的显微解剖结构。骨胶原纤维的排列在骨生物学中仍是一个备受争议的话题。大多数研究人员认为，胶原蛋白纤维在骨骼中具有特殊的取向。然而，也有一些人认为，胶原纤维是随机取向的，没有任何特定的取向。本研究将对三个骨胶原纤维的垂直平面进行检测，以确定是否确实存在特定的取向。这项研究的结果将进一步加深我们对骨的微观结构及其与骨所受载荷的关系的理解。这项研究将为骨骼对机械刺激的微观结构适应问题增加关键的新的经验证据。此外，还将产生新的证据，通过检查胶原纤维的取向来帮助阐明骨骼的微结构结构。这些结果将对身体人类学、骨生物学、骨科、组织工程学和结构生物学产生影响。

This study examines some important microscopic structural details of bone. Results can potentially improve our understanding of the tissue's microscopic architecture and how forces imposed on it during upright walking and running are distributed. Collagen fibers are a large component of bone microstructure. Their orientation reflects the types of forces sustained by bone over the time period during which it is being deposited. By microscopically analyzing histological sections, this study will provide new data about forces imposed on specific areas of the human skeleton during walking and running.Bone microstructure in animals that practice highly specialized forms of locomotion and which have been studied by other means such as in vivo strain gauge examination will first be reviewed. This will permit detailed standardization of methodology and also serve as a means of testing the capacity of collagen orientation to accurately reflect bone forces. It will then qualitatively and quantitatively assess the orientation of collagen fibers in human and non-human primate bone taken from highly localized parts of the skeleton. The first site to be studied will be the gibbon forelimb. Gibbons practice brachiation, which is a locomotor pattern in which the body is alternatively suspended by each forelimb. Strain in the gibbon ulna is primarily tensile, whereas, that in its companion bone of the forearm, the radius, is primarily bending. These force characteristics should specifically affect the collagen orientation in the two bones. This study will quantify and qualify the collagen fiber orientation in the gibbon forelimb and compare the results with the strains which have been measured in the limb. The second site that will be investigated in this study is the femoral necks of humans and chimpanzees. Human femoral necks are unique in that they have a very thin cortical bone shell at the superior portion. This region is very sensitive to bone loss from osteoporosis and is a frequent site of fracture in elderly females. An improved knowledge of the forces and structure of this region are therefore of potentially great importance. In contrast to those of humans, chimpanzee femoral necks are distinct because they have a thick cortical layer of bone on the superior neck. The different pattern of cortical bone development in humans and chimps is thought to be due to the forces sustained during their respective modes of locomotion and the result of different muscular anatomies in the hip. Humans practice bipedal locomotion during which the hip muscles function to stabilize the body on the pelvis, but chimpanzees only infrequently walk bipedally. The hip musculature in chimps therefore differs anatomically from that of humans. In humans the hip muscles (abductors) are thought to relieve forces on the upper part of the femoral neck. This results in only minimum bone formation in this region, and may be the primary reason for the thin cortical shell typical of human femora. However, chimp hip muscles do not have as strong an abductor function and therefore permit their femoral neck to suffer higher forces resulting in a thicker cortex. By examining collagen fiber orientation in chimp and human femoral necks, this study will determine what forces occur in the two species' femoral necks. These results will test whether the distribution of cortical bone is the result of different forces acting on the chimp and human femoral necks.This investigation will also examine the microanatomical construction of bone. The arrangement of collagen fibers in bone remains a highly debated topic in bone biology. Most researchers believe that collagen fibers possess particular orientations in bone. However, there are those who believe that collagen fibers are randomly oriented without any particular orientations. This study will examine collagen fibers in three orthogonal planes of bone in order to determine if specific orientations do indeed exist.The findings from this investigation will further our understanding of bone microstructure and its relationship to loads suffered by bone. This study will add critical new empirical evidence to the question of bone's microstructural adaptation to mechanical stimuli. In addition, new evidence will be produced that will help elucidate the microstructural architecture of bone by examining collagen fiber orientations. These results will have implications for physical anthropology, bone biology, orthopaedics, tissue engineering, and structural biology.