Total ankle arthroplasty

Regain pain-free, mobile ankle — without giving up movement.

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For many years from now, total ankle arthroplasty procedures has significantly improved, after disappointing beginnings. Nowadays, the outcomes are reliable because long-lasting and reproducible. In case of a severe ankle condition, osteoarthritis or an inflammatory disease, it is now legitimate to consider this procedure.

Through a central anterior incision, the surgeon replaces bone cartilage of the tibia and the talus with metallic and polyethylene implants. These three components of the total ankle prosthesis slide with each other, which preserves the joint mobility. Full weight bearing is allow immediately after surgery and a physiotherapy program is started just after wound healing.

Like for all joint arthroplasties, some risks exist and have to be prevented. If so, the long-term results are reliable. Ten years after implantation, ankle prosthesis remain functioning in more than 90% of cases. In a more long-term perspective, the forecasts are promising.

Finally, this surgery is difficult and cases are rare for non specialized surgeons. Therefore, the French Association of Foot Surgery (AFCP) recommends to have total ankle arthroplasty performed only in specialized centres, used to this procedure.

What and for who?

What are we talking about?

The ankle joint includes two major bones: the tibia and the talus. Their surface is covered by cartilage, lubricated with synovial liquid, and everything is enclosed in an envelop called capsule. All these joint components allow the ankle to move, with a normal range of motion and without pain.
A joint wear mostly affecting the cartilage can disrupt this normal functioning. Pain and a loss of motion may appear.
Likewise other anatomical areas (hip, knee, shoulder, etc.), a total ankle arthroplasty is a joint implant which aim is to substitute the weak cartilage and bone. Thus, the patient can hope to recover a non-painful and movable ankle.

Ankle prosthesis components

The aim of surgery is to replace the worn joint’s elements: the cartilage and the bone connected to the cartilage.
Therefore, an ankle prosthesis has three components : the tibial part, the talar part, and an intermediate part called “insert”.
The tibial and talar implants are metallic, made of chromium and cobalt alloy. Their specific coating allows the bone to grow onto it. This ensures the anchorage of the prosthesis in the bone, without the use of surgical cement.
The “insert”, intermediate element between the tibia and the talus, is composed of ultra high molecular weight polyethylene. It is the central friction element between the two metallic implants, and designed to highly resist to friction wear.

Which pathologies?

Two main disease families may require an ankle prosthesis: osteoarthritis and inflammatory diseases.

Inflammatory diseases, in the first place of which rheumatoid arthritis, cause destruction of the joint and its components (cartilage, bone, synovial membrane). The disease specifically targets the articular elements and only a medical treatment can permanently stop the evolution. But in some cases, rarely nowadays, the disease is too advanced to remain compatible with a normal ankle function (painless mobility). Total ankle arthroplasty is then indicated.

Osteoarthritis represents the vast majority of cases. This is an articular wear from a mechanical origin and might be explained by numerous causes:

  • Tibial fracture history
  • Chronic ankle instability
  • Rearfoot alignement abnormality
  • Anterior and posterior conflicts
  • etc…

Fortunately, among the affected patients, those who will effectively develop an arthritis requiring total ankle arthroplasty are exceptional. For instance, patients suffering from recurrent sprains are very numerous, but very rare are those who, among them, will really develop an ankle osteoarthritis.

Before surgery

Medical alternatives to total ankle arthroplasty

As always in surgery, the therapeutic path increases gradually with aggressiveness, and surgery comes last.
Painkiller and non-steroidians anti-inflammatory (NSAI) allow to live for a long time with a little or even a non-painful ankle.
The orthotic insoles also play a role as they correct at least partially an ankle’s axis deformity.
The patient can also use a walking support or crutches, that can sustainably relieve him as they limit the mechanical load applied to the point.
Steroid joint injections are very often efficient on pain and must be renewed as long as they provide the patient with a painless ankle.

Surgical alternatives to total ankle arthroplasty

We are not discussing the osteoarthritis’ cause treatment. When a total ankle arthroplasty is considered, the joint’s wear is too severe to hope restoring a functional ankle only with treating the causal.
Two types of alternative interventions are discussed : ankle arthrodesis, and supra-malleolar osteotomy.

Supra-malleolar osteotomy

Supra-malleolar osteotomy is a palliative surgery. It aims to modify the ankle’s mechanical axes so that the patient’s weight is loaded on a preserved part of the joint. The patient may hope a pain reduction but it is not a definitive procedure since the affected joint, even if not painful anymore, remains after surgery.

Ankle arthrodesis

With an ankle arthrodesis the joint is removed and to achieve a fusion between the tibia and the talus. The joint is fixed in a walking position with the plantar sole at 90° angle with respect to the leg. The pain disappears but at the price of a definitive loss of the ankle’s motion. All the other foot’s joints are kept mobile. After surgery the movement that doesn’t occur in the ankle may partially be transferred to these joints. This explains why walking looks quite close to normal without limping after an ankle arthrodesis.
Nevertheless, this surgery requires an immobilization in a cast for 2 to 3 months with a forbidden weight-bearing.
These postoperative instructions are very different from those following a total ankle arthroplasty. They are often taken into account in the decision-making process.

Preoperative exams

Most of the time, simple X-rays are enough. Specific images must be requested before surgery to measure the axes of the ankle and confirm joint wear.
In specific cases, for instance when a poor bone quality is suspected, a CT-scan may be requested by the surgeon to ensure that the implant will anchor normally in the bone. An MRI is rarely necessary in this indication but is able to inform on the vitality of the talus, which is one of the possible causes of ankle prosthesis failure.

Surgery and its aftermath

Surgical procedure for total ankle arthroplasty

The aim is to implant the three components of the ankle prosthesis into the joint.
An incision is done anteriorly on the ankle. Tendons, arteries and nerves are protected and retracted to allow joint exposure. Implants will be anchored into the tibia or talus bone; it is necessary to create the corresponding space. The bone cut has to be as economical as possible to preserve the bone stock. For this, the surgeon uses several successive instruments called “jigs” which will help the cutting but also the good positioning of the implants.
The ankle prosthesis is cementless. It is fixed into the bone by impaction, exactly as a nail in a wall. This provides the implants with an immediate stability so that a full weight-bearing is allowed immediately on the operated limb.

At the end of the procedure the ankle is placed in a removable boot cast. It aims to rest the skin and the tendons until wound healing, usually for 15 days.

Postoperative course

The postoperative boot is removable so that the dressing is accessible. It is then changed every two days.
The ankle prosthesis is designed to allow an immediate full weight-bearing on the operated limb to restore as fast as possible the joint’s function. The boot and crutches helps the patient to regain confidence in his newly operated ankle.
Once the wound is healing, usually around the 15th day, the boot is no longer necessary and walking is allowed without crutches. A physiotherapy program is started in order to maintain the ankle’s motion and to helps recover a normal walking pattern.
Non weight-bearing sport (biking, swimming) are authorized after the 3rd postoperative month. It doesn’t constitute a surgical objective. If the patient it comfortable with it, he can progressively increase his activity level with his pain as a limit. It is of his interest to favor non weight-bearing sports instead of running sports. However, resuming sport after a total ankle arthroplasty is never guaranteed.
Finally, in the best case, the ankle is forgotten between 6 and 12 months after surgery.

How to decide?

The risks

A total ankle arthroplasty , as any for any arthroplasty, carries a certain number of risks, fortunately quite rare. It is essential to be aware of them before deciding:

  • Wear: the polyethylene component wears by natural friction against the metal part. This is its normal functioning.
  • Loss of anchorage: the implant no longer “holds” in the bone for various reasons.
  • Infection: when a bacterium comes into contact with the prosthesis, it develops and compromises the prosthetic functioning. The infection can occur in a variable time after the surgery, either by contamination from the operative wound, or by migration of a germ from another infected organ (urinary tract infection, dental, skin wound, etc.). Antibiotics are therefore delivered during surgery to minimize this risk.
  • Deep vein thrombosis: the use of a tourniquet during the surgery followed by an immobilisation by boot during 15 days, is at risk to form a blood clot (thrombosis) in the veins of the operated leg. The clot can then migrate to the lung, phenomenon called pulmonary embolism. A preventive treatment is set up for 15 days.

How long does an ankle prosthesis last?

The ankle prosthesis is an implant recently “mature” after 30 to 40 years of development and progress since the first generations. Current “3rd generation” implants offer reliable results. The most recent studies describe a survival of more than 90% at a 10-years followup. This means that 10 years after surgery, more than nine out of ten patients still have their prosthesis functional.
However, although reliable, it must be considered that the total ankle prosthesis remains an implant still under development.

Choosing between the different surgical options

The main alternative to the ankle prosthesis is the arthrodesis, also called fusion, which has been the reference solution until now. This trend has reversed since the development of the most recent ankle implants.
Arthrodesis is a definitive procedure whose short and long-term consequences are known and reliable. After surgery, an immobilization in a boot is mandatory with forbidden weight-bearing for 3 months. In the long term, walking adapts to the loss of ankle’s mobility, most often without limping. However, the disappeared mobility is partially transferred to the adjacent joints (subtalar, mid-tarsal, knee). They are overloaded and may also develop osteoarthritis. This is an argument in favor of total ankle prosthesis.

Conversely, the ankle prosthesis provides much simpler short-term follow-up, since full weight-bearing is allowed immediately after surgery. The long-term evolution (beyond 10 years) is the least well-known point. The prostheses’ lifespan that we observe today is related to the implants of 10 years ago. Improvements made since then are expected to extend the lifespan of today’s implanted protheses, but this should not be confirmed before the next decade. In case of failure, the ankle prosthesis is removed and “converted” into arthrodesis.

To make a decision the selection criteria are multiple:

  • patient’s age at the time of the intervention
  • functional request (sports…)
  • acceptance or not of the risk of new surgeries
  • etc …

Which surgeon for this surgery

The ankle prosthesis is a complex procedure because it requires a rigorous technique in a hardly accessible operating area. The surgeon’s technical skill matters a lot for this surgery.
What’s more, the number of total ankle prostheses implanted every year in the world is quite low compared to other joints’ prostheses such as hip and knee.
As a result, only surgeons who often practice this procedure have acquired the experience brought by the number and the repetition of this operation.

It is therefore best to contact surgeons trained for this procedure. This is all the more true as scientific studies have shown better results for teams with the largest annual number of patients.