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Indications

Nerve Root Compression

• In those with Nerve Root Sciatica or Brachialgia where there are signs of severe nerve root dysfunction (numbness, tingling, moderate / severe weakness, incontinence), taking the pressure off a nerve can allow the nerve pain and function to recover, but neither of these is guaranteed. The disc is not removed, but trimmed back flush with the line of the vertebra.

Spinal Instability

• In those with instability due to fractures, tumours, hypermobile ligaments, severe disc degeneration, spondylolisthesis, stabilising the unstable segment in the spine can improve back pain, but this is not guaranteed.

Types

Microdiscectomy

• A less invasive technique for smaller disc prolapses. Surgical access can be improved by performing a fenestration (making a small window in the lower part of the lamina). Not a good technique for large disc prolapses or far lateral discs.

Laminectomy

• This involves removing part of the lamina (bone) and posterior spinal ligaments to improve surgical access. Different versions include full laminectomy (both sides) or a hemi-laminectomy (just one half). Used for larger disc prolapses, for access to far lateral discs, spinal stenosis, and for foraminotomy (surgical decompression of the nerve root exit hole in those with foraminal stenosis).

Fusion

• This involves fixing adjacent vertebrae to one another to treat spinal instability caused by spondylolisthesis, fractures, hypermobility, discogenic pain, or tumours. Selecting the correct spinal level is often obvious because of the pathological changes apparent on an MRI scan. In difficult cases Provocation Discography is used.
  • Lumbar and Thoracic Fusion is be achieved by using metal rods and screws, or by taking bone chips from the iliac crest to pack between adjacent vertebra.
  • Cervical Fusion is achieved by inserting a bone graft and then fixing a metal plate to the front of two adjacent vertebrae. alternatively Clowards procedure achieves fusion by inserting an artificial bone dowel alone (about 19 mm long by 14 mm in diameter) between the affected vertebra.

Provocation Discography

Selection

• It can be difficult in the pain relief clinic to suggest the correct disc level for a fusion in some instances. In the case of a spondylolisthesis the decision is easier because the pathology is easy to spot, but in patients where there is discogenic pain from disc degeneration or chronic annular tears, the selection process can be more difficult.
• Therefore some spinal surgeons will perform this investigation prior to fusion, so that the most appropriate level is operated on.

Technique

• A needle is entered into (commonly) the lower three lumbar discs from the side using X-ray guidance, under local anaesthesia, and light intravenous sedation . X-ray contrast medium injected into the centre of each of the suspect discs:-
  • Front View
  • Side View
• Injecting the contrast should reproduce the normal back pain (+/- sciatica), and subsequent injection of local anaesthetic into the centre of the disc should relieve it.

Complications - see IDET