The Design of the Anterior Tarsal

Anterior Tarsal Syndrome affects a part of the foot known as the anterior tarsal tunnel. The primary nerve involved in this condition is Deep Peroneal Nerve, which crosses over the front of the ankle joint.

Here is a deeper look at this part of the foot:

  • The Deep Peroneal Nerve runs down the anterior (or front surface) of the shin and anterior to the ankle.
  • At the level of the ankle, together with the extensor tendons, it runs underneath a broad band of tissue called the Extensor Retinaculum, which holds them in place. 
  • The nerve also travels across the top of the foot (instep) and supplies sensation to the webbed space in between the first and second toe. 
  • A small motor branch of the nerve comes off at the level of the ankle and supports a small muscle on the dorsum (top) of the foot called the Extensor Digitorum Brevis.

Symptoms and Nerve Issues

Any condition that causes swelling or inflammation around the Deep Peroneal Nerve may create and apply pressure on the Deep Peroneal Nerve (Deep Peroneal Nerve Compression Neuropathy). As the condition advances, it can be recognized as Anterior Tarsal Syndrome, a chronic entrapment health issue where the Deep Peroneal Nerve sits in a too-tight space within the structure of the foot.

Symptoms include:

  • numbness in the first web space of the foot
  • pain or burning on top of the instep and in front of the ankle
  • pain or tingling radiating back up the leg. 

The symptoms are often worse when wearing tight shoes, which increase pressure across the instep. Tapping over the nerve (Tinel's test) may produce increased discomfort or tingling. There may also be weakness or atrophy of the Extensor Digitorum Brevis muscles, noted as a depression on the anterior and lateral aspect of the foot.

Causes

Causes of Anterior Tarsal Syndrome include repeated use of tight shoes or boots; direct trauma to the top of the foot or ankle, such as a crush injury; the growth of tight bands of scar tissue across the nerve; arthritis of the underlying joints; or a foot fracture causing swelling underneath the nerve. All of these causes can change the structure and/or natural spacing within the foot, entrapping and putting pressure on the Deep Peroneal Nerve.

Treatment

Treatment of Anterior Tarsal Syndrome begins with a patient avoiding the use of tight shoes or boots. Occasionally, injection of Xylocaine and Cortisone close to the nerve is helpful.

In severe cases, neurolysis of the nerve may be required. In this surgical procedure, a small incision is made on the front of the ankle or top of the foot. The Extensor Retinaculum, or scar-like bands over top of the nerve, are released, and the nerve is freed from surrounding tissue. Any underlying spurs due to arthritis are removed as well. The skin is then closed and a protective dressing applied. 

Following surgery, weight-bearing is limited for the first two weeks. Early range of motion exercises are begun immediately to allow a healthier range of motion of the nerve and help reduce scar formation. 

Risks with this condition and surgery are primarily anesthesia-related risks. Other risks include wound healing problems or infection; failure of the nerve function to improve; and rarely, development of a condition called Reflex Sympathetic Dystrophy, which leads to pain and stiffness.