e5-05: Morton Neuroma

Morton neuroma is a common podiatric condition affecting the forefoot. It affects 10 times as many women as men and is usually diagnosed between 40 and 60 years of age. It mainly affects the third interspace but can also occur in other interspaces.

Anatomically, a Morton neuroma is an enlargement of the third common digital branch of the medial plantar nerve. The third common digital nerve receives a communicating branch from the lateral plantar nerve that passes deep to the deep transverse metatarsal ligament in the third interspace. It is a benign growth from the fibrous coverings of the nerve.

Many etiologies have been proposed, including trauma, ischemia, overpronation, equinus, intermetatarsal bursitis, and nerve entrapment due to mechanical impingement by the deep transverse metatarsal ligament.

A. Symptoms and Signs

The most common complaint is shooting pain with associated numbness or burning in the third interspace or the third and fourth toes that is worse with weight bearing. These symptoms are exacerbated by wearing tight shoe gear and are typically improved with massage and rest. Diagnosis is mainly based on clinical findings and should include attention to shoe gear, gait, and neurologic abnormalities. A Mulder click may be palpated with compression of the foot from medial to lateral with simultaneous dorsal to plantar pressure on the third interspace. The affected toes may also appear to spread apart, which is referred to as the Sullivan sign.

B. Imaging

Plain films may assist in ruling out other causes of forefoot pain such as arthritis, avascular necrosis, and fractures. MRI is not necessary for diagnosis but can be used to rule out soft tissue masses and visualize a neuroma. Ultrasound is less expensive and can be used as an adjunct diagnostic tool.

A. Conservative

Initial nonsurgical treatment of a Morton neuroma consists of wearing shoes with a wider toe box and avoiding tight shoe gear or high heels that aggravate symptoms. Metatarsal pads, orthotics, oral medications, and local injections with a corticosteroid and local anesthetic or alcohol sclerosing agents are also used.

B. Surgical

When patients do not respond to conservative management, surgical excision or decompression of the neuroma is recommended. Nerve decompression entails releasing the deep transverse metatarsal ligament to allow more space for the nerve. If the nerve is resected, the most common postoperative complication is a stump neuroma. A stump neuroma may be more painful than the original condition.

• If the patient has not responded to conservative treatment and symptoms persist.

• If the diagnosis is uncertain or another source of forefoot pain is suspected.