Michael W Bowman M.D. FACS
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. It travels across the top of the foot or instep and then supplies sensation to the web space in between the first and second toe. A small motor branch comes off at the level of the ankle and supplies a small muscle on the dorsum or top of the foot called the Extensor Digitorum Brevis.
Any condition that causes swelling or inflammation around the Deep Peroneal Nerve may produce pressure on the Deep Peroneal Nerve and Deep Peroneal Nerve Compression Neuropathy. This is known as Anterior Tarsal Syndrome. Symptoms include numbness in the first webspace and pain or burning on top of the instep and in front of the ankle. Occasionally pain or tingling may radiate back up the leg. The symptoms are often worse with tight shoes that increase pressure across the instep. Tapping over the nerve (Tinel's test) may produce increased discomfort or tingling. There may be weakness or atrophy of the Extensor Digitorum Brevis muscles, noted as a depression on the anterior and lateral aspect of the foot.
Causes of Anterior Tarsal Syndrome are repeated use of tight shoes or boots; direct trauma to the top of the foot or ankle, such as a crush injury; tight bands of scar tissue across the nerve; and arthritis of the underlying joints or a foot fracture causing swelling underneath the nerve.
Treatment of Anterior Tarsal Syndrome begins with avoidance 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 surgery 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. The skin is then closed and a protective dressing applied. Weight-bearing is limited for the first two weeks. Early range of motion exercises are begun immediately to allow range of motion of the nerve and help reduce scar formation. Risks with this condition and surgery are anesthesia related risks, wound healing problems or infection, failure of the nerve function to improve and rarely a condition called Reflex Sympathetic Dystrophy, resulting in pain and stiffness.