SUB-TALAR FUSION

This is an operation to “fuse” or stiffen the joint in the heel (the “sub-talar” joint)

Sub-talar fusions are done for two main reasons:

• Arthritis of the joint, because of a previous injury that has damaged the joint, a generalised condition such as osteoarthritis or rheumatoid arthritis, or because the joint is just wearing out for some other reason
• Severe deformity of the rear part of the foot, such as a flat foot, high-arched or “cavus” foot, a club foot or other deformity. Sometimes these can be corrected by breaking and reshaping the bones, but in other cases it is best to stiffen the joint in the corrected position, particularly if the joint is already stiff or the foot is weak.

We sometimes inject local anaesthetic or steroid into damaged joints, before any surgery is considered, to see whether this helps the pain. In some people, this gets rid of the pain and surgery is not necessary. In others, pain relief does not last but the results of the injection helps us to decide which joints to fuse.

A cut is made along the outer side of the foot. Usually this is 4-5 cm long. The joint is opened up and the joint surfaces removed and, if necessary, reshaped to correct a deformity. The joint is then put in the correct place and fixed either with a screw passed through a small cut in the back of the heel, or with a staple. Sometimes it is possible to do the operation by arthroscopy (keyhole surgery), in which case there would  just be small puncture wounds.

It is usually necessary to put some extra bone into a sub-talar fusion to get it to heal and to fill any gaps in the fusion left by correcting deformity. Often this extra bone can be obtained from the bone that is cut out to prepare the fusion. Sometimes there is not enough bone from this and artificial bone graft may be used.

Some people who have foot deformities have a tight Achilles tendon (“heel cord”) or weak muscles, or both. The Achilles tendon may be lengthened during surgery by making three small cuts in the calf and stretching the tendon. Weak muscles may be compensated by the tendons of normal muscles to do the work of the weak ones. This might be done at the same time as a sub-talar fusion. These “tendon transfer” operations are planned individually and your surgeon and physiotherapist will discuss this with you.

Some people with deformities of the foot also have deformed toes. Again, these may be corrected at the same time or at a later operation.

Most people who are reasonably fit can come into hospital on the day of surgery, having had a medical check-up 2-3 weeks beforehand. At the end of the operation a plaster backslab (half-plaster) is put on your leg from your toes to just below you knees before you wake up.  After surgery your foot will tend to swell up quite a lot, especially if you have had extra surgery such as a tendon transfer or toe straightening procedure. You will therefore have to rest with your foot raised to help the swelling to go down.

The physiotherapist will teach you how to walk with crutches. We will get you up as soon as possible! Many people get home the same day but some are in hospital for 2-3 days.

The operation can be done under general anaesthetic (asleep). Alternatively, an injection in the back, leg or around the ankle can be done to make the foot numb while the patient remains awake. Your anaesthetist will advise you about the best choice of anaesthetic for you.

Increasingly surgery is carried out with a regional block the leg is numb below the knee by injections adjacent to the nerves behind the knee. You can choose to have sedation so that you sleep lightly during the operation. The block can last 24-48 hrs giving good pain relief, but you will also be given pain-killing tablets as required.

You will need to wear a plaster from your knee to your toes until the joints have fused – usually 12 weeks. For the first 6 weeks you should not put any weight on your foot as it may disturb the healing joint. Touching your foot to the ground for balance is OK, but no more.

By the time you go home you will have mastered walking on crutches without putting weight on your foot. For the first 2 weeks after surgery you should only be up on your crutches for 5-10 minutes per hour to avoid swelling.

10-14 days after your operation you will be seen again in the clinic. Your plaster will be removed and the cut and swelling on your foot checked. If all is well you will be put back into a lightweight plaster. You should continue walking with your crutches.

Six weeks after your operation you will come back to the clinic for an X-ray. If this shows the joint is healing in a good position you can start putting weight through the plaster gradually building up to full weight.

The plaster will be removed after 12 weeks and X-rays taken to check that the fusion is soundly healed. If it is, then you will be able to start learning to walk again without plaster, just with an elastic support bandage.

As explained above, you should not walk on the foot for six weeks after surgery. Your surgeon will advise you when you can start taking some weight on the foot.

When you start putting weight on your foot we will give you a special shoe that you can wear over your plaster

If your foot is comfortable, and you can keep your foot up and work with your foot in a special shoe, you can go back to work within 2-3 weeks of surgery. On the other hand, in a manual job with a lot of dirt or dust around and a lot of pressure on your foot, you may need to take anything up to six months off work. How long you are off will depend on where your job fits between these two extremes.

If you have only your left foot operated on and have an automatic car you can drive within a few weeks of the operation, when your foot is comfortable enough. Most people prefer to wait till the plaster is removed and they can wear a shoe.

After your plaster is removed you can start taking increasing exercise. Start with walking, swimming or cycling, building up to more vigorous exercise as comfort and flexibility permit. Obviously, the foot will be stiffer after surgery and you may not be able to do all you could before. However, many people find that because the foot is more comfortable than before surgery they can do more than they could before the operation. Most people can walk a reasonable distance on the flat, slopes and stairs, drive and cycle. Walking on rough ground is more difficult after a sub-talar fusion because the foot is stiffer. Most people cannot play vigorous sports such as squash or football after a sub-talar fusion.

The main problem is the swelling of the foot, which may take many months to go down fully, and some people’s feet always remain slightly puffy. You may find that only trainers are comfortable for several months. Keeping your foot up, applying ice or wearing elastic stockings may help to keep the swelling down. Swelling is part of your body’s response to surgery rather than the operation “going wrong” but it is a nuisance to many people who may be concerned that something has indeed gone wrong.

The most serious thing that can go wrong is infection in the bones of the foot. This only happens in about 1% of people, but if it does it is serious, as further surgery to drain and remove the infected bone and any infected screws or pins will be necessary. You may then need yet more surgery to get the foot to fuse in a satisfactory position. The result is not usually as good after such a major problem as if the foot had healed normally.

About 5% of sub-talar fusions do not heal properly and need a further operation to get the bones to fuse – basically another sub-talar fusion.

Minor infections in the wounds are slightly more common and normally settle after a short course of antibiotics.

Sometimes the cut is rather slow to heal. This usually just requires extra dressing changes and careful watching to make sure the wound does not become infected.

There is a small risk of developing a deep venous thrombosis (clots in the veins of the leg) after this type of surgery. We will assess if your individual risk is high enough for you to need blood-thinning (heparin) injections while you are in plaster.

Research shows that 10% of sub-talar fusions do not heal in exactly the position intended, either because the position achieved at surgery was not exactly right or because the bones have shifted slightly in plaster. Usually this does not cause any problem, although the foot may not look “quite right”. Occasionally the position is a problem and further surgery is required to correct it.

Sometimes the screw through the heel becomes loose as the bone heals and causes pain or rubs on your shoe. If a staple is used it will be under the scar on the outer side of the foot. This can also sometimes become tender and painful. If the metal does become painful it can be removed – usually a simple operation as a day-case under a brief anaesthetic. We find that about 10% of our patients need the metal taken out.