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The functions of the back regions are protection (spinal cord and nerves), posture, trunk stability, weight bearing and movement.

Trunk stability enables higher quality vision and hearing, plus more accurate manipulation. Co-ordination of the limbs with the trunk allows for various positions of the upper body despite changes in the lower body position.

The back contains thoracic, lumbar and sacral zones* with different functions related to the structure of the individual components.

The back is a module*. The regions* of the back are:

Proper assessment and treatment of back conditions requires detailed knowledge of the clinical anatomy.

The vast majority of patients with intervertebral disk herniation (not 'prolapse') have involvement of one of the lowest two lumbar disks (L4/5 or more often, L5/S1), where weight bearing is maximal.

With normal ageing (chronic herniation), the nucleus pulposis (situated slightly posteriorly) becomes dry and dessicated. Fissures develop in the annulus fibrosis. Small herniations occur, sometimes into the vertebral body (central herniation*). The disk shrinks in height stressing the facet joints. Consequent joint displacement leads to degeneration.

Acute disk herniation is less common but more severe. Symptoms include:

  • i) Pain (usually referred, severe, in back and lower limb)
  • ii) Nerve dysfunction (paresthesia, numbness in foot, cauda equina syndrome)

Signs include:

  • i) Deformity (loss of lordosis, lateral tilt, flexed knee to ease sciatic nerve)
  • ii) Tenderness (midline, lower back)
  • iii) Reflex muscle spasm (increases pain, decreases movement)
  • iv) Nerve dysfunction (painful straight leg raising, neurological losses)

Investigations include plain x-ray, diskography, CT and MRI. Myelography is rarely performed now.

Treatment* is conservative or operative.

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