One is to formulate a model for the spine as a whole ( Meakin et al., 1998). There are two extreme approaches to understanding the mechanical behaviour of the spine. The emphasis is on the lumbar region of the human spine but results from other mammals will be used when they are considered to be suitable models for human tissue.
This paper is concerned with the relationship between the structures and properties of the tissues of the spine and their mechanical functions. This and other observations indicate the importance of muscles for maintaining the stability of the spinal column. Thus the fascia is maintained in tension when stretched by the abdominal muscles.
The structure of the interspinous ligament suggests that its main function is to attach the thoracolumbar fascia to the posterior spine. This structure enables the high extensibility of elastic fibers to be exploited but protects them from damage at high strains. In the unstretched ligamenta flava, the collagen fibers have almost random orientations but they become aligned as the ligament is stretched. The ligamenta flava contain elastic fibers (low stiffness and low strength) with collagen fibers (high stiffness and high strength). Collagen fibers also provide tensile reinforcement and prevent tears spreading across ligaments. Collagen fibers within the annulus provide reinforcement during compression, bending and torsion of the disc. Thus the disc acts as a thick-walled pressure vessel. The intervertebral disc is able to withstand compression because of the swelling pressure exerted by the nucleus pulposus which is constrained, radially, by the annulus fibrosus. Vertebrae consist of a core of cancellous bone (low density) surrounded by a shell of cortical bone (high stiffness) as a result they have high stiffness but low mass. This paper reviews our current understanding of the relationship between the structures and properties of the tissues of the spine and their mechanical functions.
0 kommentar(er)
