What is a Flexor Digitorum Longus Tendon Transfer to Posterior Tibial Tendon?

The flexor digitorum longus (FDL) is one of the tendons responsible for bending the toes down to the floor. The goals of a FDL tendon transfer surgery are to relieve pain and to help restore the arch in patients with painful fallen arches. A fallen arch occurs when the foot loses its support and flattens out, generally due to weakening of tendons and ligaments in the foot.


Tendon transfer surgery is indicated for people with a flexible flatfoot that can be moved into a more normal position. The posterior tibial tendon (PTT) is a main support for the arch of the foot. If it becomes diseased, it no longer functions properly and the arch begins to fall. The patient begins to walk on the inside of the foot as it flattens. The toes may begin to turn outward resulting in a flatfoot deformity. When non-surgical treatment such as arch supports fail to provide relief, surgery may be necessary.

If the deformity becomes stiff or arthritis develops, more advanced surgery is needed. This typically includes re-making the arch by fusing bones of the foot together. Patients with other medical problems may be too sick to safely undergo surgery. 


The PTT connects to the navicular bone near the middle of the foot at the instep. In this surgery, your foot and ankle orthopaedic surgeon will remove the FDL tendon from its usual position and transfer it to the navicular bone. This helps support or replace the diseased PTT to improve function. The diseased PTT is cleaned up or removed to eliminate it as a source of pain. 

Specific Technique

The surgery is done through an incision on the inside of the ankle and foot. The initial step is to remove the scarred or inflamed tissue of the PTT. The tendon may be completely removed if it is severely damaged.

Just below the PTT is the tendon of the FDL. Your surgeon will cut the FDL so that it is as long as possible. They will drill a hole in the navicular bone and place the end of the FDL through the bone. While the foot is held in the corrected position, your surgeon will attach the tendon to the bone. It may be held in place with stitches and/or an anchor or screw. The incision is then closed. Other procedures may be performed with the tendon transfer to improve the arch. These can include moving or shifting of bones and stretching of the calf muscles or Achilles tendon.


Patients usually are placed in a well-padded dressing with a splint or split cast. No weight is allowed on the ankle and foot. Patients are given crutches, a walker, or a knee walker/scooter. This procedure may be done as an outpatient or may require an overnight stay. 

At two weeks the sutures are removed and a new cast or removable brace is applied. At six weeks most patients transition into a walking cast or boot with a well-molded arch. 

At three months, patients return to a shoe with an arch support. Elastic hose may be used for swelling and physical therapy may be prescribed to help with walking and to restore muscle strength and joint flexibility. It may take up to one year for patients to fully recover. 

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.

Standard wound complications can occur and may include delayed healing and infection. Irritation of an adjacent nerve can occur and may cause numbness or burning. These symptoms typically resolve with time. Rarely the repositioned tendon may pull out of the navicular bone and require re-placement. A more common problem is failure to restore the arch and a residual flat foot.

Can I expect pain relief with this surgery? 

Typically, improvement in pain control is achieved with the procedure. The use of arch supports often is recommended even after successful surgery. Ankle bracing may also be helpful. 

What alternatives do I have if my arch is not restored or falls again?

If the arch is not restored or falls further, and arch supports and/or bracing are not helpful, additional surgery may be considered.  


Original article by Beatriz Garcia-Cardona, MD
Contributors/Reviewers: Glenn Shi, MD

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