When a patient develops a severe flat foot deformity it can cause severe pain on both the inner (medial) and sometimes the outer (lateral) side of the foot. The deformity consists of three parts, collapse of the arch (“planus”), angulation outward of the heel bone (“valgus”) and twisting of the forefoot (supination) and is hence known as “planovalgus” collapse. The Tibialis Posterior is a muscle in the leg whose tendon runs on the medial side of the ankle to attach onto the navicular bone in the medial midfoot. Its purpose is to hold the arch up and stop the heel from squashing out to the side.
This tendon becomes stretched or torn and hence can no longer hold the foot in a strong stable position for weightbearing and “pushoff” during walking. It is then often necessary to reconstruct this tendon.
Simply sewing it back together is not adequate. It will fail again if not reinforced and the biomechanics of the foot corrected at the same time. As such, another tendon is used for reinforcement and the heel bone is cut to move it back under the leg. The Achilles tendon is usually tight and needs to be lengthened at the same time.
The time to consider this surgery is if the patient has a painful “planovalgus” deformity, which is severely limiting activity. Non operative treatment options such as orthotics, braces, and physiotherapy should already have been exhausted. The joints that allow side to side movement of the foot, (the subtalar joint complex), need to be mobile and not arthritic. The procedure also has a higher risk of failure in patients with a severe deformity or are very heavy.
Patients with diabetes, rheumatoid arthritis, or who smoke, are at a much higher risk of complications from surgery and may choose to avoid an operation at all.
You will be given a full briefing of how to prepare for your procedure well in advance of the day of surgery. In very general terms you will need to...
- Let our team know what other medication you are taking and follow our guidelines on taking these medications in the days / weeks before surgery.
- This is particularly pertinent to blood thinning medications such as aspirin, warfarin, clopidogrel and Xarelto.
- Let our team know if you develop symptoms of any illness (including a cold or fever) or if you believe you may be pregnant.
- If you smoke, stop smoking ideally several days or weeks ahead of the procedure, but at the very least not smoke after midnight the night before surgery.
- Maintain your strength and mobility as best as possible.
- Ensure the foot is clean, do not use moisturizer on the day of the surgery
- Not eat or drink anything for a minimum of 8 hours prior to admission.
- Bring all available and relevant imaging with you to hospital.
A general anaesthetic is usually supplemented with a nerve block or local anaesthetic. A tourniquet is applied around the thigh and an incision made on the innerside arch of the foot. Deep inside the arch the tendon that moves the lesser toes down (flexor digitorum longus or FDL) is found and divided where it crosses the tendon to the big toe. It is believed that the big toe tendon joins the stump of the other tendon to provide movement thereafter.
The FDL tendon end is brought out into the wound, pulled tight, and fixed into the navicular bone by drilling a hole, pulling the tendon into the hole, and fixing it there with a screw. The Tibialis Posterior tendon may be explored and repaired.
Next is the correction of the position of the heel bone. This is important to protect the smaller transferred FDL tendon. The heel bone is cut across (usually with a minimally invasive technique using a burr), shifted across medially so it lies directly under the longitudinal axis of the leg, and put back together with a screw.
The Achilles tendon is lengthened if necessary. Incisions are closed with dissolving stitches, and a cast or cam walker boot applied.
After recovering from the anaesthetic, it is best to stay in bed with the foot elevated as much as possible for the first night. If getting out of bed, it is important that crutches or a frame are used to avoid putting any weight on the foot.
It is extremely important to keep the foot elevated (above the level of the heart) as much as possible to reduce swelling. This is especially important over the first 2 weeks.
Most patients stay in hospital two or three nights and will use strong pain relieving medications for a week or so. The incisions will be checked before discharge, but thereafter the dressings and boot are to be left in position until your review appointment. This will mean having to use plastic bags and tape to protect the foot when showering.
At 10-14 days you will be seen and the wounds checked, and dressings are removed. The boot will be reapplied, or if cast has been used, a boot fitting is necessary.
Wriggle the toes and foot in the boot as comfortable. You may be allowed to remove the boot for showers, but otherwise it stays on all the time including sleeping. At around 6 weeks after the surgery, an x-ray is undertaken to ensure the heel bone is knitting together well, and you will be able to start walking in the boot
It is usually about 4-6 weeks more before the boot comes off. Typically, it is not possible to drive until this time. You may gradually increase the amount of walking you do, but you must be guided by the ache and swelling in the foot. If its feeling tight and sore, rest and elevate the foot more and walk less.
After weaning out of the cam boot, you will need arch support orthotics in your shoes, which should, in most cases, be maintained lifelong.
All surgery carries with it some form of risk. Common risks that apply to all surgery, including flat foot reconstruction, are...
- Formation of a blood clot (“DVT” or deep vein thrombosis) Pieces of clot in the leg can break off and lodge in the lungs causing a pulmonary embolism. This can be very serious, and in rare cases even cause death.
- Nerve damage.
- Difficulty getting the wound to heal.
- Abnormal pain reactions or nerve hypersensitisation known as complex regional pain syndrome (CRPS)
Risks specifically related to this procedure include...
- Non-union of the heel bone osteotomy.
- Stretching of the tendon reconstruction causing recurrent deformity.
- Persistent pain
- Development of subtalar or midfoot arthritis.
- Hardware prominence in the heel requiring screw removal.
In some cases, subtalar fusion is a better option for this condition. For more information on refer to Other Foot Fusions.