TOTAL DISC REPLACEMENT

TOTAL DISC REPLACEMENT

The concept of replacing worn or damaged joints with artificial joints is well accepted. Most people will know somebody who has had a hip or knee replacement and other joint replacements, such as shoulders or ankles, are now undertaken routinely. For almost as long as surgeons have been replacing hip and knee joints there have been attempts to replace damaged discs in the spine, but until recently these attempts have been frustrated by technical and mechanical problems encountered in the lower spine . Surgical advances and engineering developments in recent years have overcome these problems and made the possibility of disc replacement a reality. 

The Artificial Disc

Rationale : - Total disc replacement is undertaken to help with symptoms of back pain (and sometimes with leg pain symptoms too) arising from a disc which has become worn and damaged. Pain may be coming from the damaged disc itself as well as from other structures such as the small joints at the back of the spine (the facet joints) which can become overloaded as the disc collapses and narrows. This narrowing of the disc, which occurs as the degenerative disease progresses, causes the vertebra above to sink down towards the one below putting extra pressure on the facet joints. The loss of disc height also reduces the size of the openings to either side where the nerves leave the spine, called neural foramen. This may pinch the nerve roots adding leg pain, and sometimes other symptoms, to the problems experienced with a degenerative disc. 

The Artificial Disc : - There are three parts to the Charité (pronounced share-ih-tay) artificial disc, two metal endplates and a central plastic core. The metal endplates are made from cobalt chromium alloy, a material which has been thoroughly proven in hip and knee replacements. The outer surfaces, which are positioned against the vertebral bodies, are porous to allow the bone to bond to them very firmly. This is helped by several teeth which project out and give immediate fixation to the bone. The inner surfaces are highly polished concave dishes, allowing movement with the central core. The core is made from polyethylene, again well proven in other joint replacements, with domed upper and lower surfaces which fit within the concave dishes of the endplates. 

How is the Artificial Disc adapted to an individual?

It is important to select the right implant for an individual. The dimensions from side to side and from front to back will vary according to the height and stature of an individual but will also depend on the level of the disc being replaced. The same factors will also affect the height of the implant. It is also important to restore the normal amount of wedging between the back and the front of the disc, called lordosis, since this can affect overall balance and have an impact on other parts of the spine. There is a wide range of sizes available. During the operation, trials are used and checked visually and with x-ray control to ensure the optimum size, height and lordosis is chosen and that the implant is correctly placed. 

The Operation

How long does the surgery take?

The operation normally takes about two hours for a single level disc replacement and about three and a half hours if two discs are being replaced. 

What happens during the procedure ?

After making the incision the anterior abdominal muscles (the 'six-pack' muscles) are separated and the peritoneal sack, containing the abdominal organs, carefully moved to one side. A marker is placed on the disc and an x-ray obtained to confirm the level where the disc replacement is to be inserted. The large blood vessels in front of the spine are then carefully moved to give the necessary access to the disc.

The central section of the disc is then removed and the vertebrae spread apart to allow access to the very back of the disc which must be carefully cleared away to ensure good movement of the artificial disc. 

The appropriate size and lordosis of the disc replacement is then determined using x-ray control, which is also used to ensure very accurate placement. This is an important technical step which we know affects the long term functioning of the disc replacement. 

The endplates are inserted into the disc space, being pressed home and held in position by the protruding teeth and the inherent pressure of the spine. Placement is meticulously checked, millimetre by millimetre, as the disc replacement is inserted. Once in place the core is inserted and a final check of the prosthesis is made. 

After the Operation

What is the period of hospitalization?

Most people are able to go home after about four days for a single level disc replacement and perhaps five days if two levels are replaced. 

What can I expect in hospital after the operation?

You will probably be quite surprised at how quickly and easily you will be able to get moving after the operation. We will usually aim to get you up, standing and taking a few steps later the same day or the day after the operation. Your wound will be protected by a waterproof dressing when you go in the pool. As your mobility improves you will be encouraged to take regular short walks. You will start a programme of core stability physiotherapy exercises, which are very important, and these will continue after you go home. Your therapist will show you ways to protect your back while doing everyday things such as getting in or out of bed, dressing, getting up out of a chair or getting into a car. 

The nursing staff will work with you to try and ensure that any post-operative discomfort is kept to a minimum. Initially this may be through the use of pain killing medication through a line which you control through the simple press of a button (Patient Controlled Analgesia, or PCA), but quite quickly you will be able to switch to simple tablets. 

What will my convalescence involve after leaving hospital?

The Surgical Wound : - The clips are removed once the wound has healed, usually at nine days after your operation. This is not uncomfortable and is very simple. You can either come into the hospital or we can arrange for your district nurse to remove the clips for you at home. 

Activity and Movement : - You will need to continue with your programme of active home exercises and supervised physiotherapy after your discharge from hospital. This will usually involve attending the physiotherapy department about twice a week, either at Hospital or locally to your home. Initially your physiotherapist may use treatments to help settle soreness and muscle spasm and bruising from the operation. Regular walks are also helpful. You will be taught what to do to protect your back and how to position yourself when you sit or lie down. Quite soon you will move onto more active treatments to build up your strength and improve your flexibility. 

Driving and Travel : - You can return to driving as soon as you feel reasonably confident about getting in and out of your car and happy that you will be able to sit comfortably for the necessary time. You shouldn't drive if your concentration is impaired, for example if you are uncomfortable, or if you are taking medication which might make you drowsy. 

The same guidelines apply to airline travel, although you should avoid very long haul flights for the first three months after surgery because of the risks of a deep vein thrombosis. If you do plan to travel take an aisle seat so you can get up for a stretch and do a little walking periodically, and wear your elasticated stockings. 


Sports and fitness training : - You will probably be able to return to light aerobic fitness training at your health club about six weeks after your surgery. You can discuss appropriate exercise with your physiotherapist. It is best to wait until about three months before returning to golf and competitive sports. 


Return to Work : - You will be able to consider returning to light semi-sedentary work in three to four weeks but if your work is more physically demanding you may benefit from a longer period of recovery. In the weeks after an operation you will tend to tire more easily and it might be better to return on a part time basis initially. 

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