Morton’s neuroma is a local thickening of the lining of the plantar nerve at the level of its passage between the heads of the metatarsal bones. The resulting neuroma leads to pain in the area of the metatarsal and two toes, which are provoked by wearing shoes squeezing the toes. Diagnosis is carried out on the basis of clinical signs, radiography and ultrasound of the foot. The treatment is conservative (anti—inflammatory, blockades, physiotherapy), if it is ineffective, surgical (resection of a neurinoma or dissection of the interplatelet ligament).
ICD 10
G57.8 Other lower limb mononeuralgias
General information
Morton’s neuroma is caused by a lesion of one of the common plantar finger nerves at the level of the heads of the metatarsal bones, passing between which the nerve can be compressed by a transverse interplatarsal ligament. Most often there is a unilateral lesion of the common finger nerve in the 3rd interdigital space, less often in the 2nd and extremely rarely in the 1st or 4th. Mostly women are ill. Morton’s neuroma is quite common in the practice of specialists in the field of neurology, traumatology and orthopedics.
Historically, the disease is called Morton’s neuroma, although in a clinical sense, neuroma is a nerve neoplasm, and in Morton’s neuroma there is a local thickening, not a nerve tumor. A more consistent term in relation to this pathology is metatarsalgia — pain localized in the area of the heads of the metatarsal bones. Along with this, the names perineural fibrosis, interplatelet neuroma, plantar neuroma are used.
Causes
Among the main reasons for the occurrence of Morton’s neuroma, the leading place is given to excessive load on the anterior part of the foot. It may be associated with the constant wearing of high-heeled shoes, the use of too tight and /or uncomfortable shoes, improper gait, overweight (for example, obesity), prolonged walking, standing work, sports loads. Morton’s neuroma can develop due to the presence of deformity of the foot, more often with flat feet, Hallux valgus.
Various foot injuries (fractures, dislocations, bruises) can provoke the formation of Morton’s neuroma due to direct damage to the nerve, its compression by a hematoma or as a result of the development of post-traumatic transverse flatfoot. Other provoking triggers include chronic foot infections, bursitis or tendovaginitis of the foot, obliterating atherosclerosis or obliterating endarteritis of the lower extremities, the presence of a lipoma located at the level of the metatarsal bones.
The above factors have an irritating or compressive effect on the common finger nerve. As a response, there is a local compaction and thickening of the nerve sheath, reactive degeneration of its fibers, perineural growth of connective tissue. Chronic traumatization can cause the formation of inflammatory infiltrates and lead to fusion of epineural tissues with surrounding musculoskeletal structures.
Symptoms
The most characteristic pain is in the distal parts of the foot, more often in the 3-4 fingers. The pain is characterized by a burning character, sometimes accompanied by “shooting holes” in the fingers. In some cases, patients complain of discomfort and the feeling of a foreign object allegedly trapped in shoes. At the beginning of the formation of Morton’s neuroma, pain syndrome is closely associated with wearing shoes. Patients note significant relief when removing shoes. Over time, these symptoms may disappear, and then reappear. Exacerbation is more often provoked by wearing tight shoes.
The progression of Morton’s neuroma leads to the transformation of the pain syndrome. The pain becomes constant, increases when wearing any shoes, does not go away when it is removed, but only decreases. There is numbness of the fingers. Initially, the periodic nature of the pain syndrome contributes to the fact that patients turn to doctors already in the advanced stage of the neuroma, when conservative therapeutic methods are ineffective.
Diagnostics
Patients with Morton’s neuroma can consult a neurologist, orthopedist, traumatologist or podologist. It is possible to establish a diagnosis based on clinical data. A pathognomonic symptom is a positive test with compression of the foot in the frontal plane, which is characterized by an increase in pain and its irradiation into the fingers innervated by the affected finger nerve.
To clarify the diagnosis, radiography of the foot is used, which in most patients reveals the presence of longitudinal-transverse flat feet. However, radiography, as well as CT of the foot, does not allow visualization of neurinoma. During MRI, Morton’s neurinoma is defined as an indistinctly delimited area of increased signal intensity. However, visualization of a neuroma using MRI is difficult and can give false negative results. The optimal diagnostic method is ultrasound in the area of the presumed localization of the neurinoma. Instrumental studies also make it possible to exclude the presence of traumatic injuries, tumors (chondromas, osteomas, lipomas), hematomas; to differentiate Morton’s neuroma from foot arthritis and deforming osteoarthritis.
Treatment
Conservative therapy begins with the replacement of shoes with more comfortable, soft, loose and not causing overload of the anterior parts of the foot. It is advisable to use orthopedic insoles, metatarsal pads and finger separators. The patient is advised to avoid prolonged standing and prolonged walking. To relieve pain, nonsteroidal anti-inflammatory drugs (ibuprofen, nimesulide, diclofenac) are prescribed, local anesthetics are injected into the interdigital spaces or therapeutic blockades are performed in the area of the corresponding metatarsophalangeal joint. Physiotherapy is actively used: magnetotherapy, acupuncture, medicinal electrophoresis, shock wave therapy. In the absence or low effectiveness of conservative methods, they switch to surgical treatment.
In relation to Morton’s neuroma, two types of operations can be performed. More gentle is the dissection of the transverse interplastic ligament. The operation is performed on an outpatient basis, takes no more than 10 minutes. Within a couple of hours after its implementation, the patient can walk, leaning on his leg and feeling almost no discomfort. However, in some cases, after such an intervention, a relapse of the pain syndrome is possible. More radical is excision of Morton’s neuroma, i.e. resection of the affected nerve. This operation requires more time, but can also be performed on an outpatient basis. In the postoperative period, immobilization of the foot is not required. After the operation, the patient retains numbness of the interdigital space for some time, which does not affect the supporting function of the foot in any way.
Prevention
The use of comfortable shoes of a suitable size allows you to prevent the formation of a neuroma. Women who prefer high heels are recommended to have relaxing foot baths and foot massage in the evenings. It is important to prevent flat feet, including wearing shoes with a support or a small heel. People with formed flat feet or deformities of the fingers (hammer-shaped toes, Hallux valgus) should always wear special insoles, orthopedic inserts in shoes and corrective pads.