Intervertebral Disk Replacement - Keivan Anbarani's Electronic ...

Introduction
Intervertebral discs provide flexibility to the spine and transmit loads from body weight
and muscle activity. The discs consist of three highly specialized structures, the endplates,
the annulus fibrosus and the nucleus pulposus. The two cartilaginous endplates form the
inferior and superior interface between the disc and the adjacent vertebrae, therefore
enclosing the disc axially. The annulus fibrosus is made up of several lamellae consisting of
parallel collagen fibers interspersed by elastin fibers. Surrounded by the annulus fibrosus
is the nucleus pulposus, the gelatinous core, which consists of randomly organized collagen
fibers, radially arranged elastin fibers and a highly hydrated aggrecancontaining gel. The
highly hydrated proteoglycans in the nucleus pulposus are essential to maintaining the
osmotic pressure and therefore have a major effect on the load bearing properties of the
disc.
Disc degeneration is possibly caused by three factors: mechanical loading, genetic
pre disposition and nutritional effects and aging (G. Paesold, et al.). Injuries applied to these
discs result in a variety of consequences ranging from normal motor and sensory function
to a complete loss of motor and sensory function. Spinal cord injuries are divided into two
main categories: traumatic and non-­‐traumatic. Traumatic spinal cord injuries (TSCI) are
due to a traumatic impact applied to the spinal cord, such as automobile accidents or sports
injuries. The second category of non-­‐traumatic spinal cord injuries (NTSCI) is due to any
damages to the spinal cord not caused by trauma such as genetic disorders and aging.
Additional examples of NTSCI also include vascular malformations, neoplastics, and
degenerative diseases (Figure 1).
1