Foot drop occurs when the muscles and tendons that flex the foot up are no longer working. Commonly, it is the result of a nerve injury, stroke, or nerve disease (neuropathy). It also can occur after an injury to a muscle or tendon. If a person is unable to flex the foot up when walking, the foot or toes can drag on the ground. This can make walking difficult and lead to frequent falls.
The goal of a foot drop procedure is to improve a patient’s ability to actively flex the foot and ankle up in situations where this function is weak or lost completely.
When the muscles that flex the foot up are not working, but other muscles around the foot and ankle still function, tendon transfer surgery can be helpful. If there is no muscle function at the ankle, this procedure cannot be performed. A patient must have some working muscles for a tendon transfer procedure to be successful.
Usually, initial treatment involves use of an off-the-shelf or custom brace called an AFO (ankle foot orthosis), which helps to improve the position of the foot while a person is walking. When this brace is no longer helpful, surgery can be considered. You should discuss your options with your foot and ankle orthopedic surgeon before proceeding with surgery.
The surgical procedure for a foot drop is called a tendon transfer. In general, a tendon transfer is a procedure in which a tendon (and attached muscle) that is still working is taken from one part of the foot and moved to another part of the foot to try to replace the missing muscle function. The most common tendon transferred is the posterior tibial tendon.
A posterior tibial tendon transfer procedure can involve the posterior tibial tendon alone or transfer with two other tendons, the peroneus longus and the anterior tibialis. When all three tendons are used it is called a Bridle procedure.
Multiple incisions are needed to move the tendon from one position to another. The posterior tibial tendon is taken off its insertion on the navicular bone on the inner side of the foot. This is the first incision. A second incision is made above the ankle and the tendon and muscle are identified. The tendon is pulled into this second incision and then transferred in between the tibia and fibula bones to the front of the ankle.
Another incision is made on the top of the foot at the bone to which the tendon is going to be transferred. The tendon is routed under the skin to this bone and fixed into a tunnel in the bone.
If a Bridle procedure is performed, a second tendon, the peroneus longus, is cut above the level of the ankle on the outer side of the leg. This tendon is then routed to the front of the ankle and the free end is attached to the posterior tibial tendon and the anterior tibial tendon in a bridle configuration. With this construct the posterior tibial muscle pulls on all three tendons to pull the foot up. The posterior tibial tendon is routed to the top of the foot as described above.
Occasionally, the ankle can be very stiff from long-standing weakness. If it is not possible to pull the ankle up for attachment of the tendon transfer, the Achilles tendon is lengthened to help bring the foot and ankle up. This is done either through an incision on the calf or an incision right over the Achilles tendon. The location of the incision is based on which portion of the Achilles is too tight.
The ankle is placed in a splint in the operating room to hold the position of the foot and ankle and protect the newly transferred tendon(s). Strict elevation and non-weightbearing are enforced over the first 10 to 14 days. Stitches are removed in about two weeks, after which the foot will be in a cast for about six weeks. The patient usually is non-weightbearing during this time.
Once the cast is removed, the patient will be allowed to walk in a special boot. Physical therapy to retrain the tendon(s) in its new position continues for 8-12 weeks. A night splint is worn for three months after surgery to prevent premature stretching of the tendon transfer.
As swelling improves a custom-molded brace can be worn in an athletic shoe and the walker boot is discontinued. Once the patient’s strength and motion are improved with physical therapy, the brace may be discontinued. The goal of the surgery is for the patient to walk in a regular shoe without the need for a brace.
Risks and Complications
Potential complications of this treatment can include wound infection, deep infection that can compromise the tendon transfer, and failure of the tendon or tearing of the repair.
Will I have “normal” ankle movement after this procedure?
A foot drop procedure changes the function of the ankle and allows a patient to walk without a brace. However, it is not possible to restore normal strength and full range of motion with this procedure.
Will I be able to pull up my toes?
Often a nerve injury that causes a foot drop also limits the ability to pull up the toes. The tendon transfer will not restore this function. If this is a concern, make sure that you mention it to your doctor.
Will I be able to walk without a brace?
The purpose of the procedure is to try to improve function of the ankle so that a patient can walk without a brace. However, with severe nerve injury it is not always possible to guarantee that a patient will be brace-free all the time.
Can foot drop surgery be performed if I have no working muscles at all?
The foot drop tendon transfer surgery only works if some of the muscles around the ankle are still working.
Is there a “best time” to have the procedure after a foot drop occurs? Is sooner better than later?
Nerve injuries can improve very slowly over time. At the initial time of injury, it is possible that over months to a year, the foot drop will actually improve and strength will return. By about one year, if no function has returned, a foot drop procedure is reasonable to consider.
For a long-standing foot drop (that is, the injury happened many years ago) a foot drop procedure can still work if the other muscles around the ankle are still working. So no matter how long ago it happened, it is reasonable to seek the opinion of a foot and ankle orthopedic surgeon to see if you are a candidate for this procedure.
Will I need physical therapy?
It is helpful to have formal physical therapy to help retrain the muscle for its new function. Therapy continues until progress is made in both strength and motion and you are able to transition out of the boot or brace.