Achilles tendon injuries, particularly when they become chronic, can be difficult to treat. In cases where the Achilles tendon is severely ruptured and traditional methods cannot repair the damage, flexor hallucis longus (FHL) tendon transfer surgery offers a solution. This surgery involves using the tendon from a muscle in the foot to help repair the damaged Achilles tendon, improving function and reducing pain.
What is Flexor Hallucis Longus (FHL) Tendon Transfer?
The FHL tendon transfer procedure is used to treat chronic Achilles tendon ruptures, particularly when the tendon is too damaged to heal on its own. The FHL tendon, which is located near the big toe, is harvested and re-routed to replace the damaged part of the Achilles tendon. This procedure is typically used when the Achilles tendon has been torn for several weeks or months and other methods are unlikely to succeed.
Why is FHL Tendon Transfer Used?
Chronic Achilles tendon rupture often occurs when the initial injury is not treated promptly, leading to a retracted tendon with a large gap between the two ends. Traditional tendon repairs might not work in these cases. The FHL tendon, which is strong and capable of compensating for the damaged tendon, is used to restore the function of the foot and ankle.
How is the Surgery Performed?
The surgery involves the following key steps:
- Harvesting the FHL Tendon: The patient is positioned so that the surgeon can access the tendon through a small incision near the ankle. The FHL tendon is carefully detached from its attachment to the big toe.
- Preparing the Achilles Tendon: The damaged Achilles tendon is cleaned and prepared for the transfer. The surgeon creates a tunnel in the heel bone (calcaneus) to insert the FHL tendon.
- Attaching the FHL Tendon: The harvested FHL tendon is threaded through the tunnel and sutured to the Achilles tendon. This creates a new connection that allows the FHL tendon to perform the same functions as the Achilles tendon, such as helping with walking and running.
Post-Surgery Recovery
After the surgery, the patient is required to rest the foot and avoid putting weight on it for several weeks. Typically, a plaster cast or a walking boot is used to maintain the ankle in a slightly bent position (5° to 10° of plantar flexion). Gradual rehabilitation begins after a few weeks, and patients are encouraged to perform ankle exercises to restore mobility and strength.
What are the Benefits of FHL Tendon Transfer?
- Improved Strength and Function: The main goal of the surgery is to restore the plantar flexion (downward movement of the foot), which is essential for walking, running, and performing other everyday activities. Studies have shown that patients can regain nearly normal strength in the affected leg after surgery.
- Satisfaction with Results: The majority of patients are satisfied with the results of the surgery. Many report returning to their normal activities with minimal discomfort.
- Safe and Reliable: FHL tendon transfer is considered a safe procedure, with a low risk of major complications when performed by experienced surgeons.
What are the Risks and Complications?
As with any surgery, there are potential risks involved. Some of the most common complications include:
- Infection: Some patients may develop infections at the site of the surgery. These can usually be treated with antibiotics.
- Weakness of the Big Toe: After the FHL tendon is transferred, patients may experience a slight reduction in the strength of their big toe, which could affect balance. However, most patients do not report significant problems with this.
- Clawing of Smaller Toes: In some cases, the toes may become curled (claw toes) due to changes in tendon tension. This can usually be managed with further surgery if necessary.
Long-Term Outcomes
A study involving 28 patients who underwent FHL tendon transfer showed a significant improvement in ankle and foot function. The American Orthopedic Foot and Ankle Society (AOFAS) ankle-hindfoot score, which assesses the overall function of the foot and ankle, improved substantially after surgery. Patients reported an average score of 90.4 out of 100 at their final follow-up, indicating good recoveryonclusion
FHL tendon transfer is a highly effective treatment for chronic Achilles tendon ruptures with significant defects. Although the surgery is not without risks, such as the potential for reduced strength in the big toe or infection, it offers a reliable solution for restoring function in patients with severe Achilles tendon injuries. The procedure allows many patients to return to their normal daily activities and is a trusted option when other treatments have failed.
