Describe the role of the disc in compressive loading of the spine. What happens under normal circumstances? What happens when normal forces are exceeded?

Question

What will be an ideal response?

Answer 1

ANS: During compression of the vertebrae, stress through the vertebral bodies results in increased
pressure on the nucleus. The pressure on the nucleus causes water to imbibe outward into the
cartilaginous end plates, which creates a swelling pressure within the end plates. Simultaneously,
the swelling nucleus creates tension in the surrounding anulus fibrosus, which pulls on the
cartilaginous end plates to which it is attached. Because the cartilaginous end plates are able to
undergo the least deformation of the vertebral tissues, the end plates are the first to fail under high
levels of vertical compressive loading. The components of the disc are the last to fail and, in pure
vertical compressive loading, are damaged only when there is first extensive damage of the
cartilaginous end plate and vertebral body. Given the excellent mechanism for absorbing
compressive stresses, the vertebral column rarely is damaged through compression alone.