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Published in Dag K. Brune, Christer Edling, Occupational Hazards in the Health Professions, 2020
In the same way as in engines and other machinery, a wear-out takes place in the body due to the frictional sliding. However, in contrast to machines, the body is composed of living tissue and the wear-out is counteracted by a continuously ongoing adaption and growth, and when damage has occurred, a healing process starts immediately. Depending on the rate of these competing processes, which differs between individuals, the result can become a progressing wear-out, an equilibrium at some level, or a healing. Since it is not possible to say anything certain about the rate of these processes, ergonomic recommendations for work design are to avoid repeated loadings at high levels as much as possible. Tissues such as tendons, ligaments, and cartilage, which are poorly vascularized, can take a very long time to heal after a damage, years rather than weeks.
Ligament Reconstruction with Reference to the Anterior Cruciate Ligament of the Knee
Published in Verna Wright, Eric L. Radin, Mechanics of Human Joints, 2020
Ligaments are band or cordlike structures of dense, highly oriented connective tissue that link bones in the vicinity of every synovial joint. They consist mainly of pure type I collagen, with the fibers arranged along the length of the ligament, that is, in the direction of the load acting. In the resting state the collagen fiber bundles have a wavy appearance; they are crimped. This feature explains the characteristic response of ligamentous structure to load. The elongation of a ligament is large for a small increment of load at the initial stages of loading, and once the crimped fiber bundles have straightened under load, it also stiffens. Subsequently, increments in load produce smaller corresponding elongations of the structure to the point of failure. The load-elongation relationship follows a typical nonlinear J curve.
Body Systems: The Basics
Published in Karen L. LaBat, Karen S. Ryan, Human Body, 2019
The body has two basic bone types: cortical and trabecular bone. Cortical bone is structurally strong, dense, and found near bone surfaces. Trabecular bone is generally interior and has a spongy lattice form which holds some of the blood forming bone marrow. The long bones in the arms and legs are primarily cortical bone with areas of trabecular bone near the joint surfaces. At birth, infants’ skeletons are composed of bone and cartilage (a resilient, firm connective tissue) that will be replaced with bone as the child develops. Areas of cartilage near the ends of the bones, known as growth plates, allow the bony skeleton to expand throughout childhood and into adolescence. Bone types, a long bone example, and bone maturation are illustrated in Figure 2.3. Some areas of the adult skeleton are made of cartilage. Feel the tip of your nose. You will notice that it is quite flexible compared to the bony bridge of your nose. Cartilage in your nose supplies flexibility. Cartilage can also provide a cushion where bone meets bone in a joint. Ligaments are strong bands of connective tissue that link bones across joints.
Finite element modelling and biodynamic response prediction of the seated human body exposed to whole-body vibration
Published in Ergonomics, 2023
Kaizhan Gao, Zhifei Zhang, Hongwei Lu, Zhongming Xu, Yansong He
Referring to the database of human anatomy and anthropometry provided by the Poser software (Poser Pro 11, Smith Micro Software Inc, Santa Cruz, CA, USA), the .obj file of the lumbar spine geometry in standing posture was obtained, as shown in Figures 1(a,b). The .obj file of the lumbar spine was exported from Poser and converted into a .stl file in 3ds Max software (V2015, Autodesk, USA), and the modelling was completed in the commercial software Hyperworks (V2017.1, Altair, USA). The lumbar spine consists of the vertebral bodies (including cortical bone and cancellous bone), intervertebral discs, and ligaments. There are seven types of ligaments, including the anterior longitudinal ligament (ALL), posterior longitudinal ligament (PLL), capsular ligament (CL), ligamentum flavum (LF), interspinous ligament (ISL), supraspinous ligament (SSL), and intertransverse ligament (ITL), as shown in Figure 1(c). The intervertebral disc consists of nucleus pulposus, annulus fibrosis, endplates (0.8 mm), and collagen fibres, as shown in Figure 1(d). The ratio of the cross-section area of the nucleus pulposus was assumed to be 44% of the disc area (Kong and Goel 2003).
Knee ligament injuries in U.S. pedestrian crashes
Published in Traffic Injury Prevention, 2022
A. Mallory, A. Kender, A. Valek, B. Badman, J. Stammen
The majority of pedestrian cases documented in the 2007 to 2017 NTDB/TQP datasets with knee or knee-adjacent injuries involved fractures (Figure 2). Although ligament injuries are less frequent, they can be associated with substantial long-term disability. Among the pedestrians with ligament injuries, with or without fractures, 31% of adults (16+) and 36% of younger pedestrians (<16) sustained cruciate ligament injury without collateral injury (Figure 1). Therefore, at least 31% of adults and 36% of younger pedestrians with ligament injuries sustained cruciate injury without collateral injury in the same knee. Since NTDB/TQP diagnostic codes do not differentiate between injuries in the left and right knee, these estimates likely underestimate the proportion of pedestrians with isolated cruciate injuries in a single knee. These results suggest that cruciate ligament injury in the absence of collateral ligament injury may not be as rare in real-world pedestrian crashes as previously suggested.
Parameter identification for the simulation of the periodontal ligament during the initial phase of orthodontic tooth movement
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Albert Heinrich Kaiser, Ludger Keilig, Reinhard Klein, Christoph Bourauel
In general, a ligament is a soft tissue that connects bone to bone and its mechanical function is to guide and restrict relative motion of joints. For an introduction refer to the textbook of Cowin and Doty (2007). Tensile tests of ligaments are typically done with specimens, where collagen fibre axes are aligned with the load direction. The stress strain curve observed depicts a progressive behaviour and is typically divided into three regions (e.g., Holzapfel 2001): At first, in the toe region, small force levels are necessary to elongate the tissue initially. Then, in the heel region, with increased load a progressively increased force is observed. The crimped collagen fibres gradually line up with load direction and at the end of the heel region, when collagen fibres are straightened, a transition into the linear region is observed. Here the stress strain curve is dominated by the straightened collagen fibres. At the end of the linear region, with gradual failure of highly stretched fibre bundles, drops in the stress strain curve and ultimate failure is observed. When subject to dynamic loads ligaments show viscoelastic behaviour. This could be due to the shear interaction of the interfibre matrix, that is, the interaction of the collagen fibres with the ground substance proteoglycans.