Doctoral Dissertation: Collagen Fiber Orientation and Locomotor Loading in Primates

本研究考察了骨的一些重要的微观结构细节。结果可能会提高我们对组织微观结构的理解，以及直立行走和跑步时施加在其上的力是如何分布的。胶原纤维是骨骼微观结构的重要组成部分。它们的方向反映了骨头在沉积期间所承受的力的类型。通过显微分析组织学切片，本研究将提供在行走和跑步过程中对人体骨骼特定区域施加的力的新数据。在动物的骨骼微观结构，实践高度专业化的运动形式，并已研究了其他手段，如体内应变片检查将首先回顾。这将允许方法的详细标准化，也可以作为测试胶原蛋白定向能力的手段，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定位部分的人类和非人类灵长类动物骨骼中胶原纤维的方向。首先要研究的是长臂猿的前肢。长臂猿练习伸展，这是一种运动模式，身体交替地由每条前肢悬吊。长臂猿尺骨的张力主要是拉伸的，而其前臂的伴骨，桡骨的张力主要是弯曲的。这些力的特性应该会特别影响两根骨头中的胶原蛋白取向。本研究将对长臂猿前肢的胶原纤维取向进行量化和定性，并将结果与在肢体中测量的菌株进行比较。在这项研究中要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。该区域对骨质疏松症引起的骨质流失非常敏感，是老年女性骨折的常见部位。因此，改进对该地区的力量和结构的了解具有潜在的重大意义。与人类相比，黑猩猩的股骨颈是不同的，因为它们的上颈部有一层厚厚的骨皮质层。人类和黑猩猩皮质骨发育的不同模式被认为是由于在他们各自的运动模式中持续的力和髋部不同的肌肉解剖结构的结果。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，但黑猩猩很少用两足行走。因此，黑猩猩的臀部肌肉组织在解剖学上与人类不同。在人类中，髋部肌肉（外展肌）被认为可以缓解股骨颈上部的受力。这导致该区域的骨形成最少，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强大的外展肌功能，因此它们的股骨颈承受更大的力，导致皮质更厚。通过检查黑猩猩和人类股骨颈的胶原纤维方向，这项研究将确定在这两个物种的股骨颈中发生了什么力量。这些结果将测试皮质骨的分布是否是作用在黑猩猩和人类股骨颈上的不同力的结果。这项研究还将检查骨的显微解剖结构。骨组织中胶原纤维的排列一直是骨生物学中备受争议的话题。大多数研究人员认为，胶原纤维在骨骼中具有特定的取向。然而，有些人认为胶原纤维是随机取向的，没有任何特定的取向。这项研究将检查骨的三个正交平面上的胶原纤维，以确定是否确实存在特定的方向。本研究的结果将进一步加深我们对骨微观结构及其与骨所受载荷的关系的理解。本研究将为骨的微观结构对机械刺激的适应问题提供重要的新经验证据。此外，将产生新的证据，通过检查胶原纤维的方向，将有助于阐明骨骼的微观结构。这些结果将对体质人类学、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.