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
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
- i) Pain (usually referred, severe, in back and lower limb)
- ii) Nerve dysfunction (paresthesia, numbness in foot, cauda
- 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
Investigations include plain x-ray, diskography, CT and MRI.
Myelography is rarely performed now.
Treatment* is conservative or operative.