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| Indications |
- Nerve Root Compression
- in those with Nerve Root
Sciatica 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.
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| Types |
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Microdiscectomy  is 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.
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Laminectomy
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).
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Fusion
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.
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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.
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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.
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| Provocation Discography |
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Selection - It can be difficult to
select 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.
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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:-
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Front
View
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Side
View
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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.
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Complications / see IDET
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