Overview
Patients with Morton?s neuroma present with pain in the forefoot, particularly in the ?ball? of the foot. However, not all pain in the forefoot is a Morton?s neuroma. In fact, most chronic pain in the forefoot is NOT the result of a Morton?s neuroma, but rather is from metatarsalgia – inflammation (synovitis) of the ?toe/foot? joints. The symptoms from Morton?s neuroma are due to irritation to the small digital nerves, as they pass across the sole of the foot and into the toes. Therefore, with a true Morton?s neuroma, it is not uncommon to have nerve-type symptoms, which can include numbness or a burning sensation extending into the toes. There are several interdigital nerves in the forefoot. The most common nerve to develop into a neuroma is between the 3rd and 4th toes. With a true neuroma, the pain should be isolated to just one or two toes.
Causes
The source of this pain is an enlargment of the sheath of an intermetatarsal nerve in the foot. This usually occurs in the third intermetatarsal space, the space between the third and fourth toes and metatarsals. It occurs here, at the site third intermetatarsal nerve, since this intermetatarsal nerve is the thickest being comprised of the joining of two different nerves. It also may occur in the other intermetatarsal areas, with the second interspace being the next most common location.
Symptoms
A Morton’s neuroma usually causes burning pain, numbness or tingling at the base of the third, fourth or second toes. Pain also can spread from the ball of the foot out to the tips of the toes. In some cases, there also is the sensation of a lump, a fold of sock or a “hot pebble” between the toes. Typically, the pain of a Morton’s neuroma is relieved temporarily by taking off your shoes, flexing your toes and rubbing your feet. Symptoms may be aggravated by standing for prolonged periods or by wearing high heels or shoes with a narrow toe box.
Diagnosis
A thorough subjective and objective examination from a physiotherapist is usually sufficient to diagnose a Morton’s neuroma. Investigations such as an X-ray, ultrasound, MRI, CT scan or bone scan may sometimes be used to assist with diagnosis, assess the severity of the injury and rule out other conditions.
Non Surgical Treatment
Relief of symptoms can often start by having a good pair of well fitting shoes fitted to your feet ensuring that the shoes don’t squeeze your foot together. Once footwear is addressed patients may require a small pre-metatarsal pad to be positioned onto the insole of the shoe to help lift and separate the bones in the forefoot to alleviate the pressure on the nerve. If the patients foot structure and mechanics is found to be a contributing cause, a custom made orthotic is usually the most convenient and effective way to manage the problem. Sometimes an injection of local anaesthetic and steroid is recommended to assist in settling acute symptoms.
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.
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