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At the heart of general practice since 1960

How disc replacement surgery has advanced

GP Dr Lorna Gold speaks to specialist Mr Andre Jackowski about surgical

advances and

to patient Steven Heath about his experiences

hy has disc replacement surgery just become a realistic proposition?

Since the early 1970s we have been performing spinal fusion surgery on patients with severe degenerative disease localised to one or two discs. Over the years, with advances in operating techniques and improvements in surgical instruments, we have been able to use smaller and smaller incisions.

Within the past five years, the skills and equipment needed to perform disc replacement have become available. Initial attempts were hampered by the absence of an acceptable prosthesis, but the development of a lightweight, easily- inserted device, the Prodisc, appears to have overcome the last remaining barrier to disc replacement surgery.

What is the Prodisc?

The Prodisc consists of two cobalt chrome alloy plates which are coated with titanium to promote osseointegration. An ultra-high molecular weight polyethylene insert in the lower plate provides the pivot which allows movement between the plates.

Is this the solution for all our patients with lumbar disc degeneration?

Unfortunately, patients who fulfil the criteria for disc replacement surgery are relatively rare. They must have advanced disc degeneration at one or, at most, two levels without secondary arthritic changes in the facet joints.

The window of opportunity is quite small. It would be inappropriate to offer such major surgery to patients who have mild disc abnormalities that may not progress, while by the time significant disc degeneration has occurred the facet joints are often deranged. The patient must have symptoms severe enough to merit major surgery but appropriate to the objective physical abnormality.

There should be no psychological or social factors contributing to his or her disability. A typical patient will be working and will be generally happy with his or her life, but may be unable to do sport or have to limit his or her social activities due to back pain and/or nerve root symptoms.

What does the operation involve?

Lumbar disc replacement is performed under general anaesthesia. The abdominal incision is around 6cm long, centrally placed, and may be either vertical or horizontal. The bowel is retracted and the iliac vessels are mobilised.

Under radiographic control, the worn disc is removed and the prosthetic

disc inserted using a technique that ensures the spinal ligaments are not overstretched. The spinal cord is not at risk as it ends above the level of the lumbar spine and the surgery does not extend posteriorly as far as the spinal canal, so the operation should not cause sphincter disturbance or other neurological abnormalities.

Postoperatively, the patient can get up after 24-48 hours and can mobilise as much as is comfortable. The inpatient stay is five-six days, two days shorter than after spinal fusion.

How quickly will the patient recover?

Within a few weeks, and sometimes within days, the patient will notice a symptomatic improvement, and he or she should have resumed a full range of normal activities by six weeks postoperatively. This is a significantly shorter recovery period than after spinal fusion. There are two reasons for this. The first is that the bone grafts used for spinal fusion take three to six months to fuse. The second is that after spinal fusion the donor site also takes time to heal.

Long-term, we expect that restoring a functionally normal disc will protect the discs above and below the damaged one, whereas after spinal fusion more stress is put on the adjacent discs and they undergo accelerated degeneration.

How successful is disc replacement surgery?

Thierry Marne in Montpelier and Michael Mayer in Munich, the pioneers of disc replacement surgery using the Prodisc, have reported on a series of patients. The improvement in functional ability and relief of pain were at least as good as with spinal fusion, and 92 per cent of patients overall were satisfied with the end result.

Prosthetic hip and knee joints have a finite lifespan. Is this also the case with the Prodisc?

Artificial hips and knees wear out because they are highly mobile load-bearing joints. The Prodisc has a much smaller range of movement and is subject to reduced weightbearing stress. We hope that it will last a lifetime.

Is the operation available on the NHS?

Yes, although at present the manufacturers are only allowing the Prodisc to be used in selected centres.

What future developments in surgery for disc problems do you anticipate?

Spinal arthroplasty is now where hip arthroplasty was when the Charnley prosthesis gave us reliable, widely available total hip replacements 35 years ago, although the need for careful patient selection makes a comparison with hip resurfacing more accurate. In young active people, restoring mobility by disc replacement rather than reducing mobility by spinal fusion is likely to become more widely used and lumbar and spinal disc replacement will become standard techniques over the next 10 years. By then, advances in tissue engineering and repair techniques may make it possible to salvage the patient's own disc.

How disc replacement

surgery has advanced

Despite having suffered from back pain since his early 20s, Steven Heath, from Great Barr, Birmingham, does not attend surgery very often. I was quite unprepared when he strode cheerfully into my room, announced 'You must be dying to see my X-rays', and held up a radiograph of his lumbar spine with a prosthetic disc in place. I had no idea that disc replacement surgery was a reality. In this consultation, the patient was going to have to educate the doctor. As Steven is only the third person in the UK to undergo this particular procedure, my ignorance can perhaps be forgiven.

Steven attributes his back pain to having worked as a television engineer ­ a job involving a lot of heavy lifting ­ in his teens.

His symptoms increased over the years, and he became used to having regular episodes of disabling sciatica superimposed on constant back pain and paraesthesia in his right thigh. Even on 'good' days, he was unable to sit for long enough to watch a film and had to plan movements such as lifting and bending down. This did not stop him from working as a telecommunications engineer. He has never been unemployed, and has often gone to work on hefty doses of analgesia to avoid sick leave.

At the end of 2001, after a month off work with sciatica, Steven asked one of my practice partners to recommend an osteopath. My partner suggested Dr David Smith, a local GP with an osteopathic practice. After treating Steven twice without any benefit, Dr Smith arranged an MRI scan, which showed severe disc degeneration, and referred him to Mr Jackowski. Mr Jackowski identified Steven as an ideal candidate for disc replacement surgery ­ an otherwise healthy 32-year-old man with localised severe disc degeneration and a very positive approach to life ­ and offered him the option of the new procedure or spinal fusion, the standard operative treatment. Steven chose joint replacement mainly because he liked the idea of maintaining spinal mobility, and had a four-and-a-half hour operation in the Royal Orthopaedic Hospital. He was mobile very quickly, and within two to three weeks he felt noticeably better than before the operation. His 'normal' pain has disappeared and, so far, his sciatica has not recurred. His abdominal wound has healed well. He is now able to lift his four-year-old daughter, and he plans to return to work soon.

Five take-home

messages

 · Spinal disc replacement surgery can be used as an alternative to spinal fusion.

 · It is suitable only for patients who have severe but isolated damage to one or two discs.

 · It is not a panacea for orthopaedic heartsink ­ patients who have psychosocial factors contributing to their symptoms are not suitable for disc replacement surgery.

 · The operation is performed through a small abdominal incision.

 · The prosthetic disc should last a lifetime.

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