A tendon transfer is a procedure where a healthy tendon is taken and moved to replace the function of a diseased or inactive tendon. A tendon transfer restores the movement or action to a previously paralysed or diseased muscle and joint.
The concept of "robbing Peter to pay Paul" in this way, using a healthy part of the body to address problems elsewhere, is not new. Tendon transfers have been used for over a hundred years, particularly for polio. However, the procedure is highly technical and is only undertaken by foot and ankle specialists.
Do I need a tendon transfer?
- Most commonly, in foot and ankle surgery, tendon transfers are used for painful flat feet when the diseased posterior tibial tendon is replaced by the transfer of the flexor digitorum longus tendon from the leg. This is usually combined with an osteotomy, or cuts to the bone in order to realign the heel.
- It is also used in cases of polio, much more so in the past, when the nerve supply to the muscle has been damaged by the polio virus. In foot and ankle surgery, we most often see this as a case of foot drop. One of the other functioning tendons is rerouted to allow the foot to be lifted again (ankle dorsiflexion).
- This is also the case with foot drop following spinal damage or surgery, when a muscle has been paralysed due to nerve damage.
- Upperlimb surgeons use tendon transfers for tendon ruptures caused by rheumatoid disease and if the main nerve to the upper limb (brachial plexus) has been damaged - most commonly in motorcycle injuries.
How does the procedure work?
In the case of adult acquired flat foot and posterior tibial tendon dysfunction, it firstly requires detailed assessment of the patient and foot to ascertain whether the tendon transfer is the correct surgery or if a fusion is needed.
Through a long incision from the ankle to the forefoot, the diseased posterior tibial tendon (PTT) is carefully exposed along with the healthy Flexor Digitorum Longus (FDL).
The diseased tendon is excised (cut out) if it is inadequate and the FDL tendon is exposed from the ankle to deep in the sole of the foot. The fine connections between the FDL tendon and its neighbouring Flexor hallucis longus tendon are divided at the Knot of Henry.
The harvested tendon is then carefully prepared and rerouted through a drill hole in the navicular bone - the site of the insertion of the PTT. The foot is carefully placed in the correct position and the tendon tensioned to the right length and sutured in place.
If at the same time the supporting ligament of the joint is lax, the spring ligament is reefed to assist in the reconstruction. The surgery takes about an hour and a half.
The surgery is meticulous and great care is taken to avoid cutting the major nerves which lie right next to the tendons. The tendon and supporting soft tissues need to be balanced and tensioned correctly.
How long will it take to recover?
You are likely to spend two to three nights in hospital after the operation. You will need to rest with your foot elevated for the first seven to ten days, mobilising on crutches only when necessary.
You will have a fibreglass cast below the knee for the first six weeks, elevating your foot as much as possible. Your cast will be removed between six weeks post surgery.
Physiotherapy is required to optimise results and your physiotherapist will advise you when you are ready to start limited weight bearing. Typically, you will be able to weight bear in a removable walker boot which is designed to protect the foot during the early stages of weight bearing.
Patients whose work is office based usually return to work with their feet in the walker boot or plaster after two to four weeks. If your work requires you to be physically active, this period is more likely to be 12 weeks.
In the longer term, the ankle can be stiff following tendon transfer and physiotherapy plays a very important role in recovering strength and mobility. Recovery varies for every individual patient, but it generally takes 12 months to make a full recovery and return to full range of activities at which stage, results are generally very good.