The concept of disc replacement is to place an artificial device into the disc
space to replace a damaged or painful disc and at the same time allowing the
mobility of the spine to be maintained. There are at present three disc replacement
devices which are in common surgical practice.
A disc replacement in the lumbar spine is inserted through the abdomen. This
is for the technical reason that the lumbar spine disc replacements have to
be physically large enough to support the vertebra bodies and, because of this
size, cannot be inserted through the back via a traditional spinal operation
approach. Incisions in the abdomen vary in size and position depending upon
the disc to be replaced. These scars are tending to become smaller as improved
operative techniques are developed, nonetheless it will seem odd to some patients
that an operation on your back is carried out through the front of the body!
The length of time for the operation is around 90 minutes and consists of a
careful dissection to the spine and in some areas mobilising the blood vessels
which are in the way. The disc itself is then entirely removed and the vertebra
above and below prepared to accept the implant. This generally consists of two
metal plates containing a plastic liner in a similar way to joint replacement
surgery in the knee or hip. The implants are press fitted into place and no
cement is used, unlike joint replacement surgery in the lower limb.
The risks and complications of these sorts of procedures tend to be vascular
i.e. injury to blood vessels. Another possible complication for a man in a replacement
of the lowest disc at L5/S1, is a possibility of retrograde ejaculation. This
means that semen is not ejected outwards in the normal process of an orgasm
but is directed back into the bladder. This can render a man sterile. The other
risks of this sort of surgery are the more usual ones of infection and deep
vein thrombosis guarded against by the use of antibiotics and TED stockings.
Nerve injury, although possible, is relatively rare.
Post-operatively patients are mobilised in a similar way to any form of spinal
surgery and very rarely is there any requirement for a support brace as muscular
control is usually adequate. Following disc replacement follow up x-rays are
taken over a period of 6 to 12 months to ensure that the implant does not displace.
Disc replacements are mainly for patients who have pain emanating from their
lumbar intervertebral discs only. One of the occasional failures of the technique
is that although a disc has been replaced, back pain may continue owing to problems
in the facet joints. It is therefore useful to ascertain, prior to considering
such surgery, how much pain is coming from the facet joint by using injections
and spinal probing to determine the pain source.
Usual hospitalisation time for a disc replacement is about 7 days with a recovery
period of about 6 weeks during which time increasingly more activities can be
undertaken. During the first 6 weeks after surgery the wound will be healing
and there will be an improvement in physical stamina.
In the cervical spine disc replacement surgery is also possible. The incision
in the cervical spine for a disc replacement tends to be anterior; in other
words through the front of the neck. The risks and complications for cervical
disc surgery and cervical disc replacement are similar and are firstly from
the anaesthetic itself. There is a small risk of nerve root injury and a small
risk of cerebro spinal fluid leak leading to headache. This tends to be treated
by bed rest. There is a risk of a hoarse voice if the nerve to the voice box
is bruised or injured. More usual risks are those of infection or deep vein
thrombosis which will be guarded against by the use of prophylactic antibiotics
and by the use of TED. stockings. You will also be mobilised the day after the
operation to further prevent deep vein thrombosis or clot formation.
In general disc replacement surgery has its place in both areas of the spine
provided there are correct indications. It is best to keep an area of the spine
mobile, as it reduces the stresses and strains on the levels above and below
which otherwise would be increased with fusion.
At Spine-Works we currently do not carry out lumbar (back) disc replacement
surgery. We feel that, although it makes intellectual sense, the surgery is relatively
complex and the current devices do not address all the areas of symptoms such
as the facet joints. We are currently evaluating the potential of cervical (neck) disc