The Adult Spinal Column :: Biology, Tissues

Abstract—Understanding the relationship between repetitive lifting and the breakdown of disc tissue over several years of exposure is difï ¬ cult to study in vivo and in vitro. The aim of this investigation was to develop an asymmetric Porovisco elastic ï ¬ nite element model of a lumbar motion segment that reï ¬â€šects the biological properties and behaviors of in vivo disc Finite element predictions were compared to in vivo measurements published by Tyrrell et al. (1985) of percent change in total stature for two loading protocols, short-term creep loading and standing recovery and short-term cyclic loading with standing recovery. Future models will treat the tissues as poor-assume elastic and 3D in order to be more accurate and the relationship between repetitive lifting and disc degeneration T I. INTRODUCTION he adult spinal column is made up of 26 bones, called vertebrae: 7 cervical in the neck, 12 thoracic in the rib area, 5 lumbar in the lower back, a sacrum and a coccyx. Located between adjacent vertebrae are intervertebral discs. The human intervertebral disc acts as the body’s shock absorber to properly diffuse the stresses that the spine encounters. It is made up of the inner, gel-like nucleus pulposus and the outer annulus fibrosus. Fluid flows through the disc in a diurnal cycle At the beginning of each day, the disc is fully hydrated, but as the day progresses, fluid is forced to flow out of the disc; this flow helps to carry nutrients into and waste out of the disc [1]. The exploration of biomechanical properties of living tissues is fundamental to the analysis of structural behaviour of the musculoskeletal system. It is known that mechanical properties of living tissues are time dependent. Creep, relaxation, constant strain rate loading, and cyclic loading represent the various physiological loading conditions that the human body confronts. For example, higher strain rates of loading can be used for simulating vehicular accidents or trauma, medium strain rates of loading for daily activity, creep for the prolonged static posture, and cyclic loading for work in vibrating environments, i.