Subtalar Fusion (Subtalar Arthrodesis)
The subtalar joint is below the ankle joint and allows side-to-side or tilt movements of the heel.
The purpose of subtalar fusion (arthrodesis) surgery is to remove the painful arthritic subtalar joint surfaces and fix them together, with the aim that bone will grow across and fuse the joint (‘arthrodesis’).
In other words, the surgery tries to encourage the body to heal bone across the painful joint as if it were a broken bone so that there is no longer a joint there to cause pain.
Screws are used to compress the prepared joint surfaces and stabilise the joint to assist in achieving fusion. Once fusion has occurred then the screws are redundant but are not routinely removed. Once fusion has occurred then the joint will be rigid and this usually results in abolition / substantial improvement in painful symptoms.
This surgery does not typically significantly affect the up and down movement of the ankle. Walking will not be altered on flat ground. When walking on uneven surfaces the ankle may feel less flexible.
The subtalar joint
This joint lies beneath the ankle joint and allows side to side movement of the heel bone. Pain from this joint is often worst when walking over uneven ground.
The surgery is usually performed through a 5 cm incision over the outer side of the ankle. The arthritic joint surfaces are removed and the joint surfaces fixed together with a screw(s) through the heel. The operation takes approximately 1 hour. Sometimes bone graft is required and this is usually taken from the area just below the knee (through a 4 cm incision) if required.
After surgery, your leg will be immobilised in a backslab (half plaster) for 2 weeks. Elevation of the foot above the level of the hip is important in helping to prevent infection over the first 14 days.
No weight must be taken though this leg for 6 weeks.
The total time in plaster cast / removable boot is normally 12 weeks.
Main Risks Of Surgery
Swelling - Initially the foot will be swollen and will need elevating. The swelling will disperse over the following weeks and months but will remain evident for up to 6-9 months.
Infection – The risk of deep infection occurring is approximately 1%. You will be given intravenous antibiotics at the time of surgery to help prevent this. It is important to keep the foot elevated over the first 14 days to reduce the swelling and the risk of infection. If there is an infection, it may resolve with a course of antibiotics but may rarely result in failure of the fusion.
Bleeding - Mr Redfern usually performs this surgery under tourniquet (a tight band on the thigh to prevent bleeding) and so there is rarely any significant bleeding at the time of surgery. There can often be some blood seeping into the plaster and bandages after the surgery. This rarely requires more than observation and blood transfusion would be extremely rare (risk <1%).
Delayed or non-union – This is when the joint is slow to fuse or fails to fuse and bone does not grow across the joint sufficiently. Up until 6-12 months the bones lack of fusion is described as delayed but if not fused by a year then a non-union is likely. The risk of this is approximately 5%. Smoking increases this risk very substantially. If a non-union does occur and it is painful (which is not always the case), then further surgery is usually needed. The chances of the bones not healing properly again after a second attempt (further surgery) is approximately 25%.
Mal-position – Ideally, the fusion surgery is performed so that the bones heal up in the optimal position for function and appearance. Mr Redfern takes great care to judge the best position during surgery, but as you are asleep and lying down during surgery, it is not always possible to achieve this (risk <5%). If the position is not optimal following surgery, this can usually be accommodated by custom insoles and footwear although these are not usually required. Rarely is further surgery required.
Nerve damage – There are several nerves crossing the ankle to supply sensation to the ankle and foot as well as controlling muscles in the foot. Despite great care in handling the tissues very delicately, small sensory nerves can be damaged during the surgery and this may leave a patch of numbness in the area of the incision of beyond this. This numbness may be temporary or permanent. There is approximately a 5% risk of this happening. The risk of suffering a nerve injury affecting the muscle function in the foot is <1% in Mr Redfern’s practice.
CRPS - This stands for complex regional pain syndrome. It occurs rarely in severe form and is not properly understood (risk <1% in Mr Redfern’s practice). It is thought to be inflammation of the nerves in the foot and it can also follow an injury. We do not fully understand why it occurs. It causes swelling, sensitivity of the skin, stiffness and pain. It is treatable but in its more severe form can takes many months to recover and can leave persisting pain and sensitivity.
Deep Vein Thrombosis (DVT) - This is a clot of blood in the deep veins of the leg. The risk of a clot occurring is reported as <1% after foot and ankle surgery which is generally substantially lower than after hip or knee surgery. Suspicion of DVT is raised if the leg becomes very swollen and painful. There are tests that can be performed to confirm / exclude the presence of a DVT. If confirmed, you will probably require treatment with a blood thinning agent (heparin preparation and / or warfarin or similar drug such as Rivaroxaban). The main concern with regards a DVT is that rarely (<1:1000 chance with foot and ankle surgery) a piece of clot can break away in the leg and travel to the lungs which is much more serious and can be life-threatening. This is called a pulmonary embolus and signs of this include chest pain and shortness of breath.
Once you have left hospital but remain non weight-bearing on the operated leg, you will probably require treatment with a blood thinning agent (low molecular weight heparin injections or oral drugs such as Rivaroxaban or Aspirin). Mr Redfern or his team will discuss this with you whilst you are in hospital.
Whilst in hospital following surgery it is likely that you will be treated with a blood thinning agent (LMWH - low molecular weight heparin injections) to minimise the risk of DVT/PE but this does not afford total protection and exercises to keep the toes and knee moving are advised, as well as remaining generally mobile. You are also likely be fitted for a compression stocking to be worn on the unoperated leg after surgery.
If you are concerned that the leg has become more swollen and painful (some swelling always occurs after surgery), or if you experience chest pain/shortness of breath, then you should contact Mr Redfern’s team at the hospital, your general practitioner, or the accident and emergency department immediately.
Post-Operative Course: Subtalar Fusion
1. Below knee cast (backslab plaster) applied at end of surgery
2. Expect some numbness in foot for 12-24 hours whilst the anaesthetic block is working
3. Pain medication and strict elevation of foot
4. Blood drainage through cast expected and should not cause alarm
1. Bathing possible with shower cover (usually provided by ward)
2. Elevation of leg as much as possible for first 2 weeks
3. Mobilisation non-weight bearing with physiotherapist guidance (crutches/frame/scooter)
4. Discharge home usually on day 2–3
5. No weight bearing on the operated leg for the first 6 weeks
1. Outpatient appointment (OPA) for review of wounds and removal stitches
2. Application of new cast/removable boot at the same appointment
3. If using removable boot then you may remove this to shower/bath if wounds healed
4. You will be allowed to weight-bear on the operated leg when standing only
5. You must NOT weight-bear on the operated leg when walking for 6 weeks
6. You may return to driving at this stage ONLY IF left leg surgery and automatic vehicle
(Otherwise you must not drive until 3 months after surgery)
1. OPA review and allowed to partial weight bear in removable boot (50% body weight)
2. To remain in boot until 3 months following surgery
3. Using crutches/frame/scooter until 3 months post surgery
12 weeks (3 months)
1. Outpatient review (OPA) with x-ray or scan on arrival
2. Usually the boot can be removed at this stage if xrays satisfactory
3. Begin physiotherapy and rehabilitation program
4. Gradually increase activity level as symptoms dictate
5. May return to driving at this stage
6. Begin physiotherapy strengthening / rehabilitation regime
7. Strength improves over the first 9 months or so after surgery
8. Expect some aching discomfort intermittently for the first 4-6 months
In general 4 weeks off work is required for sedentary employment, 12 weeks for standing or walking work and 16 weeks for manual / labour intensive work. We will provide a sick certificate for the first 2 weeks; further certificates can be obtained from your GP.
You may return to driving after outpatient review at 2 weeks post surgery only if it was the left leg operated on and only and in an automatic vehicle – otherwise you will be unable to drive until 3 months after surgery.