Overview

interdigital neuromaMorton’s neuroma is named after Dr Morton who first described this condition in 1876. It is sometimes called Morton’s metatarsalgia or interdigital neuroma. It is a condition that affects one of the common plantar digital nerves that run between the long bones (metatarsals) in the foot. It most commonly affects the nerve between the third and fourth metatarsal bones, causing pain and numbness in the third and fourth toes. It can also affect the nerve between the second and third metatarsal bones, causing symptoms in the second and third toes. Morton’s neuroma rarely affects the nerve between the first and second, or between the fourth and fifth, metatarsal bones. It tends to affect only one foot. It is rare to get two neuromas at the same time in the same foot.

Causes

Although the exact cause for this condition is unclear, a number of factors can contribute to the formation of a neuroma. Biomechanical deformities, such as a high-arched foot or a flat foot, can lead to the formation of a neuroma. These foot types bring on instability around the toe joints, leading to the development of the condition. Trauma can cause damage to the nerve, resulting in inflammation or swelling of the nerve. Improper footwear that causes the toes to be squeezed together is problematic. Avoid high-heeled shoes higher than two inches. Shoes at this height can increase pressure on the forefoot area. Repeated stress, common to many occupations, can create or aggravate a neuroma.

Symptoms

Neuroma pain is classically described as a burning pain in the forefoot. It can also be felt as an aching or shooting pain in the forefoot. Patients with this problem frequently say they feel like they want to take off their shoes and rub their foot. This pain may occur in the middle of a run or at the end of a long run. If your shoes are quite tight or the neuroma is very large, the pain may be present even when walking. Occasionally a sensation of numbness is felt in addition to the pain or even before the pain appears.

Diagnosis

Plain x-rays of the foot may demonstrate that one or more of the metatarsals are long (Figure #5). Not uncommonly, the second and/or third metatarsal may be long relative to the third or fourth. This can create a situation where excessive load is occurring in and around the vicinity of the interdigital nerve.

Non Surgical Treatment

Anti-inflammatory drugs may be recommended to dull the pain and lessen swelling. Neuropathic pain medications such as the antionvulsants and / or antidepressants may be tried as well. Many are able to recover from this issue at home by icing the area, resting the feet, and by avoiding wearing narrow or tight shoes. If these remedies do not work to alleviate symptoms, the doctor may give special devices to separate the toes and avoid the squeezing of the nerve. Steroid injections may reduce pain and swelling. Surgery may be required if these do not help.

Surgical Treatment

Patients are commonly offered surgery known as neurectomy, which involves removing the affected piece of nerve tissue. Postoperative scar tissue formation (known as stump neuroma) can occur in approximately 20%-30% of cases, causing a return of neuroma symptoms. Neurectomy can be performed using one of two general methods. Making the incision from the dorsal side (the top of the foot) is the more common method but requires cutting the deep transverse metatarsal ligament that connects the 3rd and 4th metatarsals in order to access the nerve beneath it. This results in exaggerated postoperative splaying of the 3rd and 4th digits (toes) due to the loss of the supporting ligamentous structure. This has aesthetic concerns for some patients and possible though unquantified long-term implications for foot structure and health. Alternatively, making the incision from the ventral side (the sole of the foot) allows more direct access to the affected nerve without cutting other structures. However, this approach requires a greater post-operative recovery time where the patient must avoid weight bearing on the affected foot because the ventral aspect of the foot is more highly enervated and impacted by pressure when standing. It also has an increased risk that scar tissue will form in a location that causes ongoing pain.

Prevention

It is not always possible to prevent a Morton’s neuroma. However, you probably can reduce your risk by wearing comfortable shoes that have low heels, plenty of toe space and good arch support.

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