Flexor Hallucis Longus (FHL)
A flexor hallucis longus (FHL) tendon transfer to the proximal phalanx is used to treat clawing of the toe.
Small muscles in the foot help to stabilize the toes. When those muscles are weakened by disease, an imbalance occurs that leads to clawing. The clawing puts abnormal pressure on the ball of the foot that can cause an ulcer to form. In addition, clawing may lead to pressure on top of the toe from shoes. Clawing is associated with a variety of underlying disorders, including Charcot-Marie-Tooth disease, diabetic neuropathy, traumatic brain injury, polio, and stroke.
The primary goal of an FHL tendon transfer is to decrease the abnormal pressures on the big toe. This will prevent ulcer formation, or in the case of an existing ulcer, promote healing. An FHL tendon transfer often is done at the same time as other foot procedures.
Indications for the FHL transfer are clawing of the toe with pain and/or ulcer formation that cannot be improved with shoe modification.
This procedure should not be done when there is uncontrolled infection of the soft tissue or bone of the toe. Also, surgery is not recommended if you have poor circulation that would prevent proper healing.
Once the patient is under anesthesia, the foot and ankle orthopedic surgeon makes an incision along the inside of the toe. The surgeon takes care to protect the nearby nerve and artery. The tendon is released from its attachment and a stitch is placed into the end of it. A hole is drilled in the bone at the base of the toe close to the metatarsophalangeal (MTP) joint. The tendon is passed through the hole from the bottom of the toe up to the top of the toe, and a stitch is used to tie the tendon securely back to itself.
Although releasing the tendon can allow the toe to straighten, release of the contracted joint capsule often is necessary as well. In many cases, the FHL tendon transfer is used in combination with other procedures to correct other foot deformities.
Typically, the foot is splinted for 10-14 days while the incision heals. At that point, stitches are removed and a walking boot is worn for four weeks. During that time weight bearing in the boot may be allowed. If there are other procedures performed at the same time, weight bearing may be delayed and a cast may be necessary. Swelling can persist for several months.
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.
Complications specific to the tendon transfer include loss of fixation of the transfer and/or recurrence of the deformity. Stiffness at the big toe MTP joint also can be a problem.
I have an ulcer on my big toe. Can I still have surgery?
While not ideal, some ulcers may not be a barrier to surgery, especially since an FHL tendon transfer usually helps with ulcer healing.