Prolapsed Inter-Vertebral Disc

Intervertebral Disc degeneration-With normal ageing the disc gradually dries out: the nucleus pulposus changes from a turgid, gelatinous bulb to a brownish, desiccated structure. Where they protrude against the ligaments ,reactive new bone formation produces bony ridges (erroneously called ‘osteophytes’, because in two dimensional x-ray images they do indeed look like osteophytic projections). In the adjacent vertebrae the end plates ossify and become sclerotic; fatty change occurs in the subchondral bone marrow. The picture as a whole is referred to as spondylosis.

Investigations –

X-Rays-Radiographic features of intervertebral disc degeneration.

MRI – better to pick up disc prolapsed and for quantification of the disc bulge. Also gives a clear picture about the pressure on the nerve from disc/osteophyte-ligament complex.

Stages of PIVD

  • Bulge
  • Protrusion
  • Extrusion
  • Sequestration

A large central rupture may cause compression of the cauda equina.

Sometimes a local inflammatory response with oedema aggravates the symptoms.

Acute back pain at the onset of disc herniation probably arises from disruption of the outermost layers of the annulus fibrosus and stretching or tearing of the posterior longitudinal ligament.

If the disc protrudes to one side, it may irritate the adjacent nerve root causing pain in the buttock, posterior thigh and calf (sciatica).

Pressure on the nerve root itself causes paraesthesia and/or numbness in the corresponding dermatome, as well as weakness and depressed reflexes in the muscles supplied by that nerve root.

Clinical features-

Acute disc prolapse may occur at any age, but is uncommon in the very young and the very old. The patient is usually a fit adult aged 20–45 years. Typically, while lifting or stooping he has severe back pain and is unable to straighten up. Either then or a day or two later pain is felt in the buttock and lower limb (sciatica).

Both backache and sciatica are made worse by coughing or straining.

Later there may be paraesthesia or numbness in the leg or foot, and occasionally muscle weakness.

The patient usually stands with a slight list to one side (‘sciatic scoliosis’).

All back movements are restricted, and during forward flexion the list may increase. There is often tenderness in the midline of the low back, and paravertebral muscle spasm.

Straight leg raising is restricted and painful on the affected side.

Neurological examination may show muscle weakness (and, later, wasting), diminished reflexes and sensory loss corresponding to the affected level.

Diagnosis-

1. Clinically

2. Imaging-X-rays  are helpful, not to show an abnormal disc space but to exclude bone disease. After several attacks the disc space may be narrowed and small osteophytes appear.

CT and MRI are more reliable than myelography and have none of its disadvantages. These are now the preferred methods of spinal imaging.

Treatment-

Heat and analgesics soothe, and exercises strengthen muscles, but there are only three ways of treating the prolapse itself – rest, reduction or removal, followed by rehabilitation:

  1. Rest With an acute attack the patient should be kept in bed, with hips and knees slightly flexed. A nonsteroidal anti-inflammatory drug is useful.
  2. Reduction Continuous bed rest and traction for 2 weeks may reduce the herniation. If the symptoms and signs do not improve during that period, an epidural injection of corticosteroid and local anaesthetic may help.
  3. Removal The indications for operative removal of a prolapse are:
  • A cauda equina compression syndrome – this is an emergency;
  • Neurological deterioration while under conservative treatment;
  • Persistent pain and signs of sciatic tension (especially crossed sciatic tension) after 2–3 weeks of conservative treatment.

The two operations most widely performed are-laminotomy and microdiscectomy.

  1. Laminotomy is nowadays preferred to the older techniques.
  2. Microdiscectomy is essentially similar to the standard posterior operation, except that the exposure is very limited.

Morbidity and length of hospitalization are certainly less than with conventional surgery.

Rehabilitation After recovery from an acute disc rupture, or disc removal, the patient is taught isometric exercises and how to lie, sit, bend and lift with the least strain. Ideally this should be done as part of an education programme in a ‘back school.