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您请求的操作仅限于组中的用户:==生物力学:腰骶区==[[文件:测试腰椎屈曲。jpg|拇指|腰骶屈曲]]脊柱的三个动作是屈曲、伸展、旋转和侧屈。这些运动在[[运动的基本平面和轴|矢状面、冠状面和水平面]]中以旋转和平移的方式发生。Bogduk, N.(2012)。腰椎放射学和临床解剖学(第5版)。中国:丘吉尔·利文斯通。。运动产生力，力就是推或拉。运动是由力的作用产生和改变的。当力使物体部分旋转时，这种效应称为扭矩或力矩。SJ < ref >大厅。分析人体运动的动力学概念。楼内:SJ厅。eds。 Basic Biomechanics, 8e New York, NY: McGraw-Hill; 2019. http://www.sciepub.com/reference/334549 (last accessed 28.11, 2022). These spinal movements result in various forces acting on the [[Lumbar Anatomy|lumbar spine]] and [[sacrum]], that is: # compressive force # tensile force # shear force # bending moment # torsional moment. [[File:Discmig2.jpg|thumb|Direction nucleus pulposus extension ]]For example, with lumbar flexion, a compressive force is applied to the anterior aspect of the disc and a distractive force is applied to the posterior aspect of the disc. The opposite forces occur with lumbar extensionMcKenzie, R. (1981). The lumbar spine : mechanical diagnosis and therapy. Waikanae, New Zealand: Spinal Publications..[[File:Discmig1.jpg|thumb|Direction nucleus pulposus flexion]]'''Load bearing''' * The lumbar spine complex forms an effective load-bearing system. When a load is applied externally to the vertebral column, it produces stresses to the stiff vertebral body and the relatively elastic [[Intervertebral disc|intervertebral disc (IVD)]], causing strains to be produced more easily in the IVDWhite A, Panjabi M. Clinical Biomechanics of the Spine. 1978, Philadelphia: JB Lippincott Co.. * Pressure within the nucleus pulposus (NP) is greater than zero, even at rest, providing a “preload” mechanism allowing for greater resistance to applied forcesHirsch C. The reaction of intervertebral discs to compression forces. J Bone Joint Surg (Am) 1955; 37:1188-1191. Hydrostatic pressure increases within the intervertebral disc resulting in an outward pressure towards the vertebral endplates resulting in bulging of the annulus fibrosis (AF) and tensile forces within the concentric annular fibres. This transmission of forces effectively slows the application of pressure onto the adjacent vertebra, acting as a shock absorber. The intervertebral discs are therefore an essential biomechanical feature, effectively acting as a [[Cartilage|fibrocartilage]] “cushion” transmitting force between adjacent vertebrae during spinal movement. * The lumbar disc is more predisposed to injury compared with other spinal regions due to: the annular fibres being in a more parallel arrangement and thinner posteriorly compared with anteriorly, the nucleus being positioned more posteriorly, and the holes in the cartilaginous endplates. See [[Biomechanics of Lumbar Intervertebral Disc Herniation]] * When a load is applied along the spine, “shear” forces occur parallel to the intervertebral disc as the compression of the nucleus results in a lateral bulging of the annulus. Shear forces also occur as one vertebra moves, for example, forwards or backwards with respect to an adjacent vertebra with flexion and extension. Torsional stresses result from the external forces about the axis of twist and occur in the intervertebral disc with activity such as twisting of the spine. * The zygapophysial or “facet” joints provide stability to the intervertebral joint with respect to shear forces, whilst allowing primarily flexion and extension movement. 回到 检索自"http:///Lumbosacral_Biomechanics＂
回到 检索自"http:///Lumbosacral_Biomechanics＂
