Morton's neuroma

What is a Morton’s neuroma?

Morton's disease is also known as Morton's neuroma. It is one of the foot pains that leads to consultations in general medicine, osteopathy and rheumatology, and podiatry.

This condition mainly affects women, around the age of menopause, but it can also be seen in men from the age of 20. It generally affects one foot, its main location is the 3rd intermetatarsal space, it can also appear at the level of the 2nd intermetatarsal space, and the other spaces are exceptionally affected.

It usually causes:

• A thickening of the tissue of the nerve membranes
• A sharp pain similar to burning sensations
• A sensation of electric shock between the toes
• Discomfort mainly in the 3rd intermetatarsal space

The causes of Morton's neuroma

This concerns the compression of the plantar nerve or interdigital nerve in the intermetatarsal space, causing a thickening of the tissue membranes of the nerve. The nerve tissue is replaced by fibrous tissue, the nerve becomes hard, and loses its ability to transmit and its elasticity.

What are the symptoms of Morton's neuroma?

There are several symptoms and signs:

Pain is the main symptom.

It involves the appearance of particularly sharp, burning pains whose source is located at the third or second intermetatarsal space, that is, at the base of the toes. This pain radiates to the adjacent sides of the toes. It is triggered when the patient is standing and especially when walking.

The patient is then obliged to take off their shoes, which is characteristic. They can no longer wear shoes that are too tight or high-heeled.

Less typically, it may be simple pain in one toe, plantar pain, or even pain in the heel or calf. Rarely, it presents as paresthesia (unpleasant, strange sensations) that are poorly localized.

The signs observed during examination are few but typical, including:

• Pain triggered by hyperextension of the toes (true Lassègue’s sign)
• Cutanous hypoesthesia of the toes in the affected space, as well as dysesthesia (strange sensations) and paresthesia (tingling).
• Palpation of a more or less hard mass between two toes at their base.

The examiner’s finger can displace this mass, which is mobile upwards, that is, towards the dorsal side of the foot. The other hand presses the metatarsal heads transversely to bring them closer together (in the manner of shoes that are too tight) and can then perceive a characteristic “click” or snap, which may sometimes trigger a sharp pain reminiscent of the usual symptoms. This is Mulder’s sign.

When standing, there may sometimes be a spreading of the affected toes, and a claw or hammer deformity of one or more toes may also be associated.

When the patient walks, they may sometimes adopt an antalgic posture, that is, a compensatory gesture to avoid putting weight on the painful area and thus avoid pain.

The overall examination must not be forgotten, in particular the search for a contracture of the posterior muscle chain (gastrocnemius muscles), a gait disorder, or a loss of strength in toe flexion (pulp support relieves the metatarsal heads).

Other possible associated causes of foot pain

The diagnosis can be difficult, especially since other conditions can cause confusion and may sometimes be associated. Morton’s neuroma should not be confused with other conditions such as:

• Metatarsalgia of mechanical origin; the pain is more localized under the metatarsal heads or at the metatarsophalangeal joint. This may show instability with effusion (second ray syndrome)
• Fracture of the sesamoid bones of the foot (the pain from these fractures is highly localized).
• Fracture of the bones of the forefoot (case history and exquisitely tender spot)
• A foreign body that went unnoticed
• A corn (clavus)
• A dermatological condition

Diagnosing a Morton’s neuroma

The diagnosis is clinical. The history reveals pain mainly in winter when wearing closed shoes, or in tight shoes such as ski boots.

The pain may force the patient to remove their shoes to massage their foot.

On clinical examination, the Mulder’s sign supports the diagnosis.

X-rays

In foot conditions and ankle pathology, radiographic assessment is an essential extension of the clinical examination. We need X-rays of both feet, standing, from the front and side.

Ultrasound

Ultrasound allows a dynamic examination of the forefoot, and the localization and size assessment of Morton’s neuroma.

MRI

MRI is theoretically the examination of choice for exploring soft tissues, as it can rule out possible associated conditions. However, its reliability for diagnosing “Morton’s” is sometimes compromised in advanced forms with fibrous predominance.

Medical treatment of a Morton’s neuroma

Mesotherapy can be proposed; it consists of the superficial injection of a mixture of medications including painkillers and non-steroidal anti-inflammatory drugs. It must not contain cortisone (a steroidal anti-inflammatory).

The local application of cold or heat can relieve pain.

Shoes for Morton's Neuroma

Pain from Morton's neuroma is especially present in winter in closed shoes. Changing your footwear habits in winter can relieve pain by wearing shoes that are softer and wider at the forefoot.

In summer, with open shoes and walking barefoot, the pain tends to subside.

Orthopedic Insoles

Orthopedic insoles can be recommended, especially in cases of associated conditions such as metatarsalgia.

Orthoses or Splints, Toe Spacers

Wearing a splint or orthosis is not recommended, however, silicone toe spacers are worth trying. They are placed in the painful space and held in place by a sock, hence worn with a closed shoe.

Laser Treatment and Cryotherapy

Laser treatment for Morton's neuroma can be recommended for pain relief, by inducing a heating effect around the neuroma that helps reduce inflammation and pain.

Cryotherapy treatment, also known as cryosurgery, consists of placing a probe into the nerve under ultrasound guidance and burning the pathological deep layers of the nerve with temperatures reaching -50°.

Injections

Cortisone injections are performed under ultrasound guidance and are indicated in the early, inflammatory stage of Morton's neuroma. The risks of repeated injections are skin discoloration (dyschromia), fragile skin, and the risk of lipoatrophy, and thus atrophy of the plantar fat pad.

Surgical treatment of Morton's neuroma: the operation

When the previously mentioned treatments are insufficient, surgery may sometimes be necessary. Two procedures can be proposed depending on the size of the nerve and the duration of the symptoms.

• If the lesion is small in diameter, generally less than 5 millimeters in its longest dimension on ultrasound, and relatively recent, only nerve release will be performed, neurolysis, with cutting of the intermetatarsal ligament and removal of the synovial bursa when it is hypertrophic. This gives good results even if the intermetatarsal ligament later re-forms.
• If the lesion is significant on ultrasound, measuring more than 5 millimeters in its longest dimension, and has been present for over a year, treatment involves resecting, removing the nerve. This is a neurectomy, with cutting of the intermetatarsal ligament and removal of the synovial bursa when it is hypertrophic.

The scar is located on the top of the foot for either neurolysis or neurectomy, as a scar on the sole of the foot risks causing painful skin thickening, like a callus.

Recovery after the operation

The procedure is performed on an outpatient basis, meaning you can leave the clinic the same day. It is necessary to wear a postoperative shoe for a period of 1 month, the time needed for the nerve to heal or for the nerve stump to retract.

Resumption of sports activities is considered 45 days after the procedure.

Postoperative exercises and rehabilitation

After surgery, we will show you exercises to do yourself, so it is mainly self-rehabilitation in the absence of any associated pathology.

It is necessary to do the following exercises :

• Stretch the posterior muscle chains, the calf muscles or gastrocnemii.
• Massage the plantar fascia (the sole of the foot), the scar, and the operated area.
• Strengthen the intrinsic muscles of the foot.