Morton’s neuroma is benign hypertrophy of one of the common digital nerves within the metatarsal interspaces of the foot. The vast majority of these neuromas, about 75 percent, develop within the third interspace between the third and fourth digits with the remainder, up to 22 percent, occurring in the second interspace. Very rarely does this occur in the first or fourth interspace. While somewhat debated, most authors agree the etiology of this condition is caused by nerve impingement from the deep transverse inter-metatarsal ligament which lies directly dorsal and courses perpendicular to the affected nerve.
Risk Factors Include Foot Types, Improper Footwear, Obesity
Risk factors associated with development of a neuroma are either flat or very high arched foot types, tight fitting or high-heeled shoes, obesity, and certain types of high-impact sporting events.
Multiple Approaches to Diagnosis
Diagnosis of a Morton’s neuroma can be made from a number of subjective and objective findings. Typically, patients will complain of pain in the forefront that can radiate into the digits on either side of the affected interspace. The pain is often described as burning or tingling and affected patients will often complain of a sensation that a foreign object is under their foot. A physical exam will reveal pain with deep palpation between the affected metatarsal heads, without pain at the metatarsal heads themselves.
A palpable “click” with reproduction of painful symptoms can be felt when applying pressure dorsally just proximal to the affected digits while applying medial to lateral compression of all five metatarsal heads. In difficult to diagnose patients, modalities such as ultrasound, MRI, and diagnostic injection can be utilized as well.
Conservative Treatment Recommended To Start
Conservative treatment is typically employed first and includes shoe gear modification, activity modification, and use of NSAIDS. Custom orthotics with a built-in metatarsal pad are often an effective way to reduce the amount of pressure applied to the painful site.
Corticosteriod injections are also used to reduce inflammation, as well as shrink the hypertrophied nerve, but studies vary widely with regard to the efficacy of this treatment. When conservative treatment fails, surgical excision of the affected nerve is indicated. This is done fairly easily through either a dorsal or plantar approach and reported success rates for surgical excision are greater than 90 percent.