Nerve transfer surgery for the leg and foot

What a nerve transfer is

When a nerve is cut, crushed or stretched so badly that it cannot regrow to its target in time, the muscle it supplies can waste away. A nerve transfer moves a healthy, less critical nerve branch, called the donor, and connects it to the injured nerve or the muscle’s own nerve branch close to the muscle, called the recipient. The donor’s fibres then grow into the muscle over a shorter distance and can bring it back to life.

Motor nerve transfers in the upper limb are well established. In the lower limb the technique is not yet widely used, but a review of 43 articles found a number of options.^[1]

When it is considered

• Foot drop after peroneal nerve injury. This is the most studied use in the lower limb. Of the 36 articles on motor transfers, 16 described transfers for peroneal nerve injury and 17 for femoral nerve injury (for the thigh muscles). Two described the tibial nerve and one the obturator nerve.^[1]
• A nerve injury with a long gap or a delay, when a graft is unlikely to reach the muscle in time. See nerve grafting and nerve repair.
• Iatrogenic injury, such as foot drop after spine, hip or knee surgery. In a series of 28 people with foot drop after an operation, 83% improved ankle lift after nerve release, neurolysis and nerve transfer, though these were combined procedures at a single institution.^[4]

Sensory nerve transfers, which restore feeling to a small area, have also been described in the lower limb.^[1]

Foot drop: how it is done

For foot drop, the donor is usually a motor branch of the tibial nerve (for example, a branch to the soleus muscle) or a branch of the superficial peroneal nerve. It is joined to the deep peroneal nerve or to the branch to the tibialis anterior, the main muscle that lifts the foot.^[2,5] The donor is chosen so that giving up its branch is tolerated. In one series, the donor deficits included weak toe flexion in 2 of 11 people and a smaller calf in 7.^[5]

What results to expect

• A pooled analysis of 41 people (four case series) found a wide, bimodal spread of ankle lift strength, with a mean of 2.1 on a 0–5 scale. Some people did very well and others gained little. Age, timing, donor nerve and site of injury did not clearly predict the result in that analysis.^[2]
• In a 2012 series of 11 people, one regained grade 4 strength, three regained grade 3, and four regained no muscle activity. Recovery began on average about 7.6 months after surgery. Nine could walk and take part in activities, and seven did not wear a brace.^[5]
• In a study of eight people who had the soleus branch of the tibial nerve transferred, half reached grade 3 or better and could walk without an assistive device.^[6]
• A systematic review of traumatic peroneal nerve injuries found a good motor grade (3 or better) in 62.9% after nerve transfer, compared with 81.4% after nerve release, 78.8% after end-to-end repair, and 49.0% after nerve grafting. Those groups were not matched, so they should not be compared head-to-head.^[3]

Regrowth is slow. In one series, clinically apparent recovery began about 7.6 months after surgery, and in another, new electrical activity in the foot-lifting muscles appeared between 10 and 15 months.^[5,6]

Alternatives and combinations

• Brace (ankle-foot orthosis) and physical therapy
• Tendon transfer, in which a working tendon is rerouted to lift the foot. One review describes tendon transfer combined with nerve surgery as coordinated care for foot drop after knee dislocation.^[7]
• Nerve release, repair or grafting, depending on the injury

Nerve transfer can also be combined with other procedures.

Risks

Risks include infection, bleeding, wound-healing problems, numbness or weakness from the donor nerve, incomplete recovery, and the possibility that the transfer does not work. Delay lowers the chance of success, since muscles that have been without a nerve supply for a long time may not recover.^[1]

Is it right for you?

The decision depends on the nerve injured, how long ago, what nerve studies show, your health and goals. A careful history, examination, nerve testing arranged with another specialist and imaging help decide. Read about foot drop, common peroneal nerve compression and nerve laceration. Dr. Ozturk performs this procedure for appropriate patients, and an evaluation is how to find out whether it fits your situation.

When to seek care

Consider an evaluation if you have new weakness lifting your foot after an injury or an operation, especially if it has not improved after several weeks.