The end of ankle pain?
Published on 01 October 2009
Hot on the heels of fusion surgery, ankle replacement is now becoming more commonly performed.
It’s unlikely that ankle replacement surgery will ever overtake either knee or hip replacement in term of popularity or numbers of operations performed.
While more than 65,000 people in the UK have a new knee fitted each year and similar numbers undergo hip replacement surgery, only around 1,000 people with arthritis have their ankle replaced at present.
But while even its most enthusiastic advocates concede that ankle replacement surgery is still regarded as developmental rather than a mainstream orthopaedic procedure, the operation has considerable merits when performed on the right patients.
When Arthritis Today covered this topic 5 years ago, only a handful of orthopaedic surgeons were carrying out ankle replacement, as many remained sceptical about the lack of robust evidence of its success rate.
Pioneering ankle surgeon Peter Wood, from Wrightington Hospital in Wigan, led the way in the UK when he started performing the surgery in the early 1990s. Now, as he is about to retire, he reflects that while only a couple of hundred operations were performed in 2003 in the UK, the number has greatly increased. “All over the world, more designs have become available, and surgical experience has increased tenfold,” he says.
Other orthopedic surgeons are now taking up the cudgels on behalf of ankle replacement and are now much more willing to do the surgery, despite the absence of evidence of long-term durability.
Paul Cooke, an orthopaedic surgeon from the Nuffield Orthopaedic Centre in Oxford who has ten years of specialising in ankle replacement, says that from the very limited number of patients who have been followed up over 15 years, the failure rate is higher than that of hip replacement. Peter Wood puts the failure rate as between one and two per cent a year, as measured by the re-operation rate. A recent journal article written by Mr Wood and colleagues estimates a survival rate of 95 per cent over 5 years, which drops to 80 per cent after a decade.
“There’s a calculation of need against predicted outcome, but sometimes the patient’s need is so great we will take the increased risk compared with fusion. Ankle replacement is not the answer to every ankle problem but it can be very effective in the right patient,” says Paul Cooke. “The latest generation of prostheses, which have a mobile bearing in them, have proved to work well and the early outcomes that Peter Wood was showing have been sustained.”
The surgery is performed as an alternative to ankle fusion. Fusion results in a more robust ankle and has a higher rate of success, but means that the joint becomes stiff and immobile. Fusion enables the recipient to walk without a limp and over rough ground, but is only really effective if other joints near the ankle such as the hip and knee are working well.
“The advantage of ankle replacement is that it gives you movement, but you can’t always be as active after this type of surgery compared to fusion,” says Paul Cooke, who carries out an equal number of fusions and replacements, so is well-placed to judge the two operations’ pros and cons.
So who should have an ankle replacement? Experts differ slightly on this point.
“The people who do best are those with arthritis elsewhere in the body, so those with rheumatoid arthritis or juvenile idiopathic arthritis are good bets; people whose hips, knees and backed are affected, or have multiple joint replacement,” says Paul Cooke.
“Someone who would be perfect for fusion would be, for example, an 18-year-old who wants to still kick a ball about with his friends, whereas the perfect replacement patient would be a 70 year-old with diffuse arthritis, who has stiff joints elsewhere and more limited expectation of movement.”
Pain is the main reason for having an ankle replacement
Peter Wood’s view is that age and activity are less important than the straightness of the ankle joint at the time of surgery, and there is evidence that those whose ankle joint is crooked or deformed at the time of surgery have a higher failure rate.
The main reason for having an ankle replaced is because of pain, rather than lack of mobility. The operation maintains a range of movement in the ankle joint, although it doesn’t return it to its previously healthy state – if the ankle was stiff before surgery, it will stay stiff afterwards.
A small study of fusion and ankle replacement patients at the Nuffield illustrated that ankle replacement is not always as robust or stable as fusion. All those who had had a fusion were able to return to playing golf after surgery. But only two thirds of those who underwent replacement were able to play a round of golf unaided; the remaining third had to wear an ankle brace for extra support.
If an ankle replacement fails it is usually due to wear, loosening or formation of cysts. It can be revised, or converted to a fusion, although this is a bigger operation and should only be performed in specialist centres such as the, Nuffield Orthopaedic Centre, Wrightington Hospital, Leeds General Infirmary, the Avon Orthopaedic Centre in Bristol or the Queen’s Medical Centre, Nottingham.
Post-operatively, the patient is in splints for between four and eight weeks, and once the plaster cast is removed physiotherapy is very important to get the new joint working effectively. It is usually around 6 months before the patient can enjoy recreational walking again. The swelling and the stiffness when starting to move the joint can last for up to 18 months, and may never go away entirely.
A life-transforming experience
Only a handful of people with ankle problems caused by arthritis will ever have surgery. (Of the 30,000 referrals to foot and ankle clinics every year for ankle arthritis, only 3,000 come to surgery; either fusion or replacement. A further 3,000 will have an arthroscopy, and the rest will have injections or orthotics.) Nevertheless, for those few, it remains a life-transforming experience.
“There are a lot more surgeons carrying out ankle replacement surgery, although only six of us are doing more than 20 a year, and rest are doing relatively few, “ says Paul Cooke. “Over the next few years they will be doing a lot more. Just recently it has spread from being performed in a very few centres to becoming much more widely available.”
Peter Wood concurs. “People who say that ankle replacement will never take off are wrong,” he says. “I think for every ten knee replacements performed there will be one ankle replacement, so 6,000 a year. It will be done in every town and in every large hospital trust.”