Ankle Fusion for Arthritis
Arthroscopic Ankle Fusion (Arthrodesis)
When ankle arthritis reaches end stage levels then an ankle fusion may become necessary. This is a very successful operation in relieving pain and correcting deformity with a long track record of success. Most surgeons in the U.K. now perform this through keyhole techniques. Occasionally an open technique may be indicated in cases where there is gross deformity or previous plates and screws that may need to be removed.
Alternatives treatments
I will discuss in detail any potential alternative treatments with you, these may include: Non-surgical options such as injections and braces which can be effective in the early stages of arthritis. Sometimes keyhole surgery is useful to remove painful bone spurs and remove loose bodies or cartilage flaps. By the time an ankle fusion is indicated these so called joint preserving options will probably have been tried and would not be indicated. The main alternative to an ankle fusion therefore is then a total ankle replacement. On occasions bone realignment surgery may also be considered. I would have discussed your individual options with you before deciding on which operation you should have, and you will need to understand all the pros and cons of each option before proceeding.
What happens during this surgery?
In this operation a keyhole approach is made to the front of the ankle and the joint surfaces are prepared for fusion. This is done through two small incisions in the front of your ankle. Preparation of the joint means that any bone spurs are shaved away, the remaining cartilage covering the joint is cleared down to the underlying bone which is then breached so that bleeding surfaces are reached. This encourages the two surfaces to heal together just like when a broken bone heals. When the joint preparation is complete screws are put across the joint through separate small 5-10 mm incisions on the inside of the lower leg whilst ensuring that the foot is in a flat 90-degree position.
The operation usually takes around one to two hours and you will have four or five small (5-10mm) incisions which are closed with absorbable sutures. A below the knee half plaster is then used.
What are the risks of this operation?
Be certain to read this information together with the section on the general risks of foot and ankle surgery. Other than those general risks there are some risks that are especially important in an ankle fusion and I will describe them below:
- Infection – A small risk of infection exists at a rate of around 1 %. This is higher in diabetics or those who smoke. Some cases can be treated with antibiotics alone. More severe cases may need surgery to remove the screws and perform a clear out. Often multiple operation may be needed to eradicate any deep infection and the fusion operations may have to be repeated and more extensive open fusion surgery may be required, occasionally using external fixation frames and plastic surgery to achieve skin cover. Extremely rare cases may end in a below the knee amputation.
- Bleeding– Excessive bleeding may lead to formation of congealed blood under the skin (Haematoma) this may need surgery to evacuate in rare cases.
- Nerve injury and numbness– sensory nerves to the foot cross the ankle. Whilst care is taken to avoid injury occasionally, they can be bruised or rarely cut. This will not affect walking ability but may cause a patch of numbness on the back or outside of the foot. Sometimes a small regrowth of the nerve may lead to a painful nodule in the scar (neuroma), this may need to be surgically excised if it continues to cause pain.
- Non-union -This is when the fusion fails to take place and bones fail to fuse together. There will then be some micromotion possible at the ankle joint which can remain painful. This may eventually result in the screws breaking due to fatigue failure. If this happen then you may need the procedure repeated to ensure a solid fusion occurs. You may find that bone graft is used, or an open approach adopted in repeat of the operation. This complication occurs in under 5% of cases. Rates are higher in smokers, those with a high BMI and those with medical comorbidity.
- Mal union– This is when the ankle is fused in a less functional position that may result in symptoms. The aim of this surgery is to fuse the ankle in a position that results in the foot being square and flat to the ground, if this is not achieved then you may find it difficult to walk. In most the deformity is mild, and a shoe insert is likely to solve the problem. More severe cases may need repeat surgery to break the fusion again and reposition the foot. Fortunately, this has never been required in my practice.
- Injury to Blood vessels (artery) – The arterial supply to the foot cross the ankle at the front and the back. These are at risk of injury. Bleeding from these can cause, a haematoma or aneurysms that may need further surgery and in extremely rare circumstances may compromise the supply to the foot.
- Thrombosis – Blood clots in the calf (Deep vein Thrombosis) can occur after lower limb surgery. These can break off and go to the lungs causing pulmonary embolism (PE). We assess individual risks of thrombosis and balance against the side effects of blood thinning injections. You are likely to be offered these injections for the time you are in plaster. Usually for six weeks. Please take some time to read the information material that I have written on VTE.
- Hardware removal- sometimes the screws can cause symptoms by rubbing against the skin or into other joints. If this happens then we may elect to remove the screw(s). This is generally delayed until after the fusion is complete so that the presence of the screw is no longer essential. This will mean you having a secondary operation.
- Complex Regional Pain Syndrome or CRPS- this is a rare complication that can result in post op pain as well as symptoms such as skin colour changes, tingling or sweating and may affect the whole of the foot and sometimes the entire lower leg. It occurs in less than 0.5% but can result in a poor outcome and prolonged recovery.
Smoking
Smoking is a serious risk factor in hindfoot surgery but especially when considering fusion or fracture surgery. The rates of wound healing problems and infection are significantly higher in smokers. The chance of the fusion failing to heal (non-union) is also considerably higher if you smoke. It is therefore essential for the best outcome that you stop smoking if you are a smoker. I would like you to have been a non-smoker for at least three months or preferably 6 months prior to an ankle fusion operation.
