Flexor Hallucis Longus
The flexor hallucis longus (FHL) is the primary flexor muscle of the big toe. It originates at the back of the leg, transitions into a long tendon as it enters the foot and attaches on the bottom of the big toe.
The peroneus brevis (PB) muscle starts in the leg and continues along the outside of the ankle. It then takes a sharp turn and ends on the outside of the foot. The peroneus brevis works with the peroneus longus (PL) to turn the ankle and foot outward.
The FHL to PB tendon transfer is a surgery to improve the function of the foot. The FHL is passed behind the ankle to the outside of the foot to either assist or replace the damaged PB tendon.
The goal of this surgery is to restore the power of the ankle and foot to turn outward, which is required for cutting and turning movement.
Repeat ankle sprains can lead to peroneal tendon tears. If left untreated, the tendon may be irreparable, requiring a tendon transfer. Nerve disorders with poor muscle function (often seen in the cavus foot) also may require a tendon transfer.
Patients with active infection should not have this surgery. Vascular disease, poorly controlled diabetes, or heavy smoking also can be reasons to not have this surgery.
An incision is made over the course of the PB around the outside of the ankle. The PB is examined carefully and any degenerative portion is removed. A second incision is made on the inside of the foot and the FHL is identified and pulled from the inside of the foot to the outside of the foot where the PB inserts. The FHL can be directly attached with a screw or suture to the bone where the PB inserts. After the tendon transfer, the wound is closed with sutures.
Recovery varies from patient to patient. Six to eight weeks of rest may be needed and is dependent on associated procedures. This is followed by physical therapy and gradual return to activity. Return to full function may take up to a year.
Risks and Complications
All surgeries come with possible complications, including the risks associated with anesthesia, infection, damage to nerves and blood vessels, and bleeding or blood clots. With this procedure there also is the risk of continued PB problems, persistent weakness and scarring.
What happens to my big toe if you are transferring the FHL?
Full toe function will not be lost because there is another tendon that attaches to the great toe to help flex it. Following transfer, it is expected that the patient will lose some strength of the great toe. Despite this, patients are satisfied with their toe function.
What outcome can I expect from this procedure?
Isolated tendon transfer has shown good results. However, outcomes are difficult to predict as the procedure is often performed with other procedures, such as correction of a cavus foot.