The Normal Ankle Joint
Ankle arthritis affects the joint between your shin bone, known as the tibia, and the talus bone. We often think of this joint a bit like a hinge, allowing upward and downward movement. In reality, ankle joint motion is a bit more complex with sliding and rotation involved as well. In fact, all movements of the foot and ankle are quite complex and are often a combination of the movement of several joints.
When thinking about the ankle joint, it is also important to consider the joint below it, known as the subtalar joint (between the talus and heel bones) and the joint in front, the talonavicular joint (between the talus and navicular bones). The subtalar is responsible for side to side movement of the heel and the talonavicular joint allows some up and down motion but also some twisting of the foot.
Today, if you’re suffering from the pain of ankle arthritis, ankle replacement is good option to consider. In the past, ankle replacements had a little bit of a poor reputation. They didn’t perform very well and tended to wear out quickly.
Many generations later, today’s ankle replacements now perform extremely well, and like hip and knee replacements, they are becoming much more mainstream, and are being offered to younger patients.
The ankle is a complex joint. It’s much more than just a “hinge”; it flexes and rotates, and a new ankle replacement needs to be able to provide a good biomechanical approximation of your own ankle.
Today’s ankle replacements are performing really well because of technological advances, which mean that an ankle replacement can be tailored precisely to suit the geometry of your joint – after all, we’re all put together a little differently.
What is ankle arthritis?
The bones on either side of any joint are covered in cartilage, a protective layer that sits on top of the bone. Cartilage is not only a shock absorber but also allows smooth motion of a joint, working with joint fluid to allow this. When the cartilage is worn away, usually by wear and tear or, most commonly, as a result of previous trauma to the ankle including fracture, bone begins to rub against bone and this causes pain. This is arthritis.
The pain and poor function of a worn-out ankle joint can have a huge impact on mobility and an individual’s quality of life.
At the moment, we do not have a way of getting that worn away cartilage to grow back. Fortunately, we do have some great surgical ways of dealing with the problem and getting you back to being happy and mobile.
Historically, if you had advanced ankle osteoarthritis, where a lot of the cartilage is worn away, the gold standard surgical treatment was to have an ankle fusion, also known as ankle arthrodesis. This involves placing large screws across the ankle joint to allow your bones to heal together so that the foot and ankle are permanently held in a neutral, right angle position. As you can imagine, this means that the joint will no longer move.
It’s an effective treatment for reducing ankle pain, where we essentially sacrifice some movement in exchange for pain relief.
Not being able to flex at the ankle means that your gait (the way you walk) isn’t normal and people with fusions have to adapt to this, which is usually not a problem. Fusing the ankle, however, does put extra pressure on the surrounding joints, in particular the neighbouring subtalar joint.
We know that arthritis affecting the subtalar joint is seen relatively frequently at about 10 years after an ankle fusion. We also rely on your body to heal across the joint to make it one block. Sometimes this doesn’t happen and despite our best efforts, the joint doesn’t fuse (non-union).
The alternative to an ankle fusion is an ankle replacement. An ankle replacement essentially involves removing the worn joint surfaces of the ankle and replacing them with artificial components. The replacement (aka “prosthesis”) is made up of three parts – a part that replaces the roof of the ankle joint (tibial component), a second part that replaces the floor of the ankle joint (the talar component), and the third component is a spacer which sits between the tibial and talar components. The tibial and talar components have stems which slot into the bones they are fixed in to. All of this is designed to preserve ankle joint motion.
In the past, ankle replacements had a little bit of a poor reputation. The first generation of ankle replacements from the 1970s didn’t do so well and tended to become loose and wear out rather quickly. Fast forward to our current 4th generation implants and technology has allowed for much better implants and we can expect much better longevity from them.
Ankle replacements now give us a fantastic way of keeping your joint moving and therefore protecting against some of the issues seen with ankle fusion. With the latest techniques, we are able to accurately placet the new joint in the best possible position taking into account a number of factors individual to you. With the latest 3D printing technology, we are then able to print customised guides that we use in surgery to makes sure we put the replacement in exactly as planned for you.
Today’s ankle replacements are performing really well because of these technological advances, which mean that an ankle replacement can be tailored precisely to suit you as an individual – after all, we’re all put together a little differently.
What happens during an ankle replacement?
The process starts well before the day of the operation. A CT scan of your ankle is taken, and using special software, a detailed surgical plan is made, and this information is sent to the ankle replacement manufacturers. They then produce the customised guides that we use in surgery, so that it can be very accurately placed into your ankle.
The operation itself takes a couple of hours and is done using x-ray guidance in the operating theatre.
What’s the recovery like after an ankle replacement?
The surgery is usually performed under a general anaesthetic, and a nerve block - this is where the main nerves to the lower leg are temporarily numbed and offers great pain relief after the operation, as well as during. The block ensures you’ll be very comfortable when you wake up from the operation.
Most patients stay a maximum of one night in hospital. Your ankle will be held secure in a plaster cast for two weeks which allows the surgical wound to heal up. You’ll be on crutches so that you can completely take the weight off the healing leg whilst in plaster. In order to reduce swelling and support wound healing, you’ll be advised to resting with your foot and ankle elevated most of the time.
After two weeks, you’ll return to clinic, where we will check that the wounds are healing well and perform an xray to ensure all is well. The plaster cast will be removed, and working with the physiotherapist, you’ll be encouraged to get the joint gently moving, and you’ll be able to bear weight through the ankle in a walking boot.
It can take up to six to twelve months and sometime beyond to see the full effects of the replacement. Ultimately, you can anticipate being back to full activity, and many patients will have returned to activities such as cycling, hiking, swimming and skiing. Running and other higher impact sports put the new joint under a lot of pressure and force and may cause the joint to wear out sooner – so a usually best avoided.
What are the potential risks of having an ankle replacement?
Any surgical procedure brings with it an element of risk, but thankfully, excellent surgical techniques, hospital care and rehab mean that the risks are very much minimised.
Potential risks to any surgery on the foot and ankle include infection, bleeding, pain, scarring, injury to nerves and blood vessels, blood clots in the leg or lung (DVT and PE). Specific to ankle replacements, risks included instability, excessive stiffness of the joint or loosening of the ankle replacement components.
Advanced technology and surgical skills allow ankle replacements to be the very best fit possible, and if the ankle replacement eventually wears out, it’s possible to carry out a revision ankle replacement.
I've had an ankle fusion. Is it possible to have the fused ankle replacement?
The simple as is ‘yes’. Converting and ankle fusion to an ankle replacement is especially useful in patients that develop subtalar arthritis after an ankle fusion. Rather than fuse the subtalar joint as well and create a really very stiff leg, we can replace the ankle and fuse the subtalar joint (where there is no other choice other than fuse) and preserve some movement in the lower leg.
How successful are ankle replacements?
Ankle replacement surgery is a fantastic way of treating ankle arthritis and getting you out of pain. Not everyone will be suitable for an ankle replacement, but in the carefully selected patient, ankle replacements now do very well.
The latest generations of replacements have so far shown excellent survivorship and durability. Although we don’t quite know how the latest ankle replacements will function in 20 years, we do know that as many as 97% are still working well at 2 years, around 90% at 5 years and as many as 80% at 8-10 years.
All in all, ankle replacement is a great option if you’re suffering from the pain and disability of ankle osteoarthritis.