Jaw joint replacement
Reproduced from Issue 122 of Arthritis Today
Is there nothing that can't be replaced these days? Orthopaedic surgeon Robert Hensher explains the pros and cons of jaw joint replacement.
Joint replacement is a very common condition orthopaedic procedure. It is not widely appreciated that it is also possible to replace the temporomandibular (jaw) joint. This idea in itself is not new. In the post-war era, jaw replacements were designed for patients who had large amounts of lower jaw removed for cancer, etc. These often had a rudimentary false joint to them.
In the past 20 to 40 years, several types of prosthetic jaw joint were developed, particularly in America. One particularly good system is no longer available, but at the moment we have the choice of three; the most sophisticated is a custom-built joint based on a model of the jaws created from a special 3D CT scan. An example of this joint is shown in the picture.
This is not a common procedure, but the patients who usually have it usually have severe arthritis, either rheumatoid or osteoarthritis of the joint; failure of development of the joint; the end result of multiple operations on the join, and ankylosing spondylitis, a condition where the joint fuses and movement is not possible. It is a serious problem if patients cannot open their mouths adequately, as dentistry, anaesthesia and resuscitation may be severely complicated and even life-threatening.
The surgery is quite lengthy and involves incisions on the face, this is to gain access to the joint, remove the diseased area and insert the prosthesis. During this procedure there is a risk of causing permanent facial weakness as the facial nerve runs in several branches throughout this area. Post-operatively patients normally need to be in hospital doe about five days. They require vigorous physiotherapy, for which an exercising device is used. Review appointments are essential, with x-rays being taken to check the position of the joint and monitor its function. Patients should only be offered this surgery when their jaw joints are in sufficiently bad condition to be confident of an improvement. False joints are not as good as normal healthy joints, and, as in other areas of the body, a compromise must be anticipated.
If we measure the opening of the jaw and use visual analogue tests for pain, dietary upset and patient satisfaction, where these qualities are measured as marks out of ten, experience with modern total jaw joint replacement prostheses shows that 80 to 85 per cent of patients have significant improvement in all these parameters. However, some are not helped, and some are made even worse. This is likely to be the case when the joint is used to the wrong reasons and it is essential that the correct assessment and diagnosis are made.
The longevity of the joints is not yet known; the best guess from the companies who make the latest types is 15 to 20 years, although this may be much longer. With the plastic socket and metal ball type it is likely that wear will only take place in the socket, so that this component may need replacing. Extensive studies in the orthopaedic literature have shown that there is no greater risk of wear debris complications with these joints than in other identical types used in orthopaedics generally.
A number of surgeons can perform jaw joint surgery, and as in all operations, it is a wise policy to choose somebody who has experience in using these prostheses.
- Robert Hensher is a consultant oral maxillofacial surgeon at the Cheltenham and Gloucester Nuffield Hospital in Cheltenham.
  Alan Grindrod pictured now and shortly after surgery Case study Alan Grindrod, now 75, was eating a cheese and lettuce sandwich when in his own words, his jaw joint "failed catastrophically". "Something went crunch and I thought it must be a stone in the lettuce; my jaw wouldn't shut," explains Mr Grindrod, a retired engineer from Gloucestershire. He had had a "clicky" jaw for years, which turned out later to have been osteoarthritis. After an unhelpful visit to his GP Mr Grindrod went to see his dentist, who knew of Robert Hensher's expertise as a maxillofacial surgeon. By this time, surviving on liquidised food and painkillers, Mr Grindrod sought a consultation with Mr Hensher, who after steroid injections and physiotherapy had failed, decided that the new custom-built jaw joint replacement he was then pioneering would be ideal. Mr Grindrod first had preparatory surgery to remove part of the diseased jaw bone called the condyle, and had a temporary plastic spacer fitted. MRI and CT scans were taken of his jaw to assess the level of damage in the joint, which were sent to the US for a plastic model to be made of his jaw and teeth before the final custom-built metal prosthesis could be especially made and inserted six months after the first operation As this type of surgery was very new in the UK and not then available on the NHS (it now is) Mr Grindrod took advantage of his private healthcare insurance to become the first person to have this type of surgery performed, at a cost of £15,000. "I'm told it was a text book case, and that the joint replacement went straight in," recalled Mr Grindrod. "When they took the bandages off I looked like a hamster, but I was only in the Gloucester Royal Hospital for four days and soon recovered. The day after the operation I was actually biting and chewing bread for the first time in ages. Six days later I managed to chewed chicken and chips. It was heaven! Three years on it's perfect. I'm a bit careful how hard I bite, since I have no idea of the strength of the 2.5mm titanium screw fittings, but the only thing I can't eat now is sticky food like toffee. I'm fine with crunchy things.." Mr Grindrod was so happy with his new titanium jaw joint, which should last him for the rest of his life, that he happily chats to prospective jaw joint replacement patients, allaying their fears. "Some of them think they will be scarred, but I defy anyone to look at him from six inches and tell me where I have a scar," he says. "I'm really satisfied with my new jaw joint. Indeed, I've practically forgotten my left hand jaw joint is not my natural jaw bone." |
