ABSTRACT
This chapter aims to explain how work activities can cause intervertebral disc damage, degeneration and pain. The soft centre of each disc is an amorphous gel comprising mostly large proteoglycan molecules. Tension in the collagen fibres of the annulus opposes the swelling pressure in the nucleus, so that the nucleus exhibits a measurable pressure, even when the disc is unloaded. The uniform pressure throughout the nucleus and inner annulus is often referred to as the intra-discal pressure (IDP), and IDP rises in linear proportion to the applied compressive load. Reduced disc height following creep creates some slack in the annulus and in the ligaments of the neural arch, so that the spine’s resistance to bending falls: in effect, the whole spine segment becomes ‘wobbly’. Exposure to very heavy manual work and/or vibrations is associated with radiographic disc height loss, which is indicative of endplate damage and/or annulus collapse.
