Morton’s neuroma

A neuroma is the enlargement, which in medicine is called a tumor, that originates in a nerve. The Morton ‘s neuroma was first defined by Morton in 1876. He described it as a tumor of the nerve that runs through the space between the third and fourth fingers of the foot, called intermetatarsal space. Today it is known that its original name is not totally correct since the lesion does not correspond to the tumor proliferation of the nervous tissue itself, but to the tumor of the fibrous tissue and the blood vessels that surround the nerve.

To better understand the location of Morton’s neuroma, it is convenient to make a brief explanation of the anatomy of the foot. In the foot there are two different nerve branches that will reach the toes through the intermetatarsal spaces, the internal plantar branch that runs along the edge of the inside of the foot and the outer plantar branch that runs along the lateral edge of the foot, these two nerves they originate in turn from a nerve trunk that runs down the leg that will be the tibial nerve. A nerve that comes out of the plantar branches will reach each toe, specifically the first toe or big toe is innervated by two branches, one for each edge of the toe, which originate from the internal plantar nerve. The same thing happens to the second finger as to the first. The innervation of the third toe is different, one border corresponds to the internal plantar nerve and the other border to the external plantar nerve. This implies that in the route of these nerve branches through the intermetatarsal space there will be the same space as in the other fingers for the circulation of the nerves, but twice the volume since two different branches arrive.

In most cases, in 80-85% of cases, Morton’s neuroma occurs right in that intermetatarsal space (third space) where two nerve branches converge. Exactly before the nerve reaches the beginning of the fingers. Less frequently, in 10-15%, the neuroma occurs between the second and third toes (second intermetatarsal space). Morton’s neuroma can occur in one or both feet at the same time. It is more common in women than in men and especially in middle-aged women.

Why is it produced?

The causes of Morton’s neuroma are unknown. But there are a number of factors related to its appearance:

• Increased compression in the area.
• Repeated microtrauma.
• Degenerative diseases of the nervous system .
• Wearing the wrong footwear.
• Biomechanical alterations, specifically forefoot supination.
• Digital deformations: claw or hammer toes.
• There are other factors considered as risk factors for the appearance of Morton’s neuroma:
• Obesity.
• Be a smoker
• Drink alcoholic beverages.
• Bad diet
• Consumption of certain drugs: relaxants, tranquilizers, hypnotics, marijuana, cocaine …

Increased pressure in the area where Morton’s neuroma occurs is thought to cause the nerve that runs through the intermetatarsal space to become “trapped” and injured. This increase in pressure may be due to various circumstances such as biomechanical alterations that transfer greater load to the external area of ​​the foot, which is not designed or prepared to withstand them.

Wearing a high-heeled, narrow-toed shoe also shifts loads to the ball of the foot. Increased pressure and compression of the fingers facilitate “entrapment” of the nerve.

The repeated microtrauma that occurs in this area when we walk or when we run injure the nerve that is restored with reparative tissue (fibrous tissue). Continuous injuries to the nerve cause an accumulation of fibrous tissue that compresses the nerve and forms a tumor at that level. These continuous microtrauma must be combined with the movement that the foot makes when it pushes itself off the ground to take a step. The weight of the body is distributed over the ball of the foot and the toes are flexed upwards. The digital nerve is tensed and compressed by the intermetatarsal ligament, located at this level. This compression also favors the appearance of the neuroma.

In the case of claw or hammer digital deformities, these fingers are in a position in which the nerve is in continuous tension, which favors its injury.

Morton’s neuroma symptoms

The symptoms that appear are the following:

• Nervous type pain, with pricks associated with an electric current or burning sensation.
• Inability to put on shoes due to pain.
• Radiation of pain to the fingers with a sensation of crushing or cramps.
• Increased pain when wearing high-heeled, narrow-toed shoes.
• Reduction of pain when taking off shoes and massaging the area.

How is it diagnosed?

The diagnosis of Morton’s neuroma is based on the history and clinical examination that is performed. Occasionally, a “click” is palpable in the area of ​​the neuroma due to compression. During the examination, the painful point should be located, which when pressing manifests the same pain as when walking. The foot is also compressed laterally causing the pain described. Sometimes an infiltration with an anesthetic is applied to observe the reaction of the pain, if this disappears it is compatible with nerve injury and not with other structures that could be affected.

A radiological study should be carried out to rule out other series of alterations, such as a fracture or fissure of a bone.

Other methods are also used to confirm the neuroma using imaging techniques, such as:

1. Magnetic resonance imaging: It is the most specific diagnostic imaging method in the case of identifying neuromas. It makes it possible to observe the tumor clearly and confirm the diagnosis more precisely for future surgical intervention.
2. Ultrasound In recent years it has been proving to be a cheaper and less invasive alternative to nuclear magnetic resonance, although it is still not possible to observe an image as clear as that obtained with resonance.

The definitive diagnosis of neuroma can only be made by studying the affected tissue, once it has been removed by surgery and analyzed by an expert anatomo-pathologist. In the event that neuroma treatment requires surgical removal, this study should be performed to confirm the diagnosis of the injury.

Morton’s neuroma treatment

Treatment of Morton’s neuroma can consist of two ways:

Conservative treatment, which consists of several therapeutic alternatives:

• Application of orthopedic treatments with the use of orthopedic insoles to try to eliminate pain and inflammation and reduce the pressure that the affected area supports.
• Wear suitable footwear with good toe capacity and a moderate heel (2-4 cm),
• Application of ultrasounds or other types of physical therapies that reduce pain and inflammation.
• Injections with anesthetics and corticosteroids have a controversial application. In some cases good results are obtained, but in others complications may appear that aggravate the problem and force surgical intervention as the last alternative.

In the event that conservative treatments fail, the alternative of surgery remains. This consists of the removal of the tumor tissue and different surgical techniques can be used for this, the most used being those that use a dorsal approach, which allows the skin of the sole of the foot to be left intact, thus avoiding the appearance of possible complications such as hypertrophic scars. or keloids.

How can I avoid it?

To prevent this pathology, it is advisable to wear shoes with heels no higher than 4 cm in height, that do not have a narrow toe and allow free movement of the fingers.
It is advisable to go to the podiatrist periodically to assess the possible existence of any biomechanical alteration that may cause us problems in the future.
Avoid the consumption of alcoholic beverages, tobacco and follow healthy lifestyle habits.