Morton’s Neuroma

Anthony G. Ryan and Peter L. Munk

A 53-year-old woman presented with unremitting pain in her foot, exacerbated by walking, with occasional shooting pain into her toes.

Figure 58A

Figure 58B

Figure 58C

Figure 58D

Giant Morton’s neuroma.

• Infected intermetatarsal bursa
  
• Foreign body reaction
  
• Tendon sheath ganglion cyst
  
• Synovial cyst with infarcted tissue
  
• Giant cell tumor of tendon sheath

Foot pain is an increasingly common clinical complaint, especially in an aging population engaged in physical exercise programs. The referral of a patient with forefoot pain where Morton’s neuroma is the working clinical diagnosis is an increasing source of referrals, particularly from podiatrists.

This lesion is not a true neoplasm, but a fibrotic overgrowth, the cause of which is unknown, although repetitive biomechanical trauma (e.g., secondary to wearing high-heeled shoes) has been implicated.

It is thought that dorsiflexion of the toes produces friction of the affected nerve against the edge of the intermetatarsal ligament, resulting in fibrosis and consequent enlargement of the nerve sheath, predisposing to further friction.

The lesion (bilateral in ~10% and multiple in as many as 28%) is most commonly found between the second and third metatarsal heads. Compression of the neuroma on walking irritates the associated interdigital nerve, giving rise to the characteristic neuralgia.

A mass of pale fibrous tissue is demonstrable wrapped around the normal nerve.

The mass is seen to be composed of benign perineural fibrosis surrounding a plantar interdigital nerve.

Radiographs are rarely contributory, although widening of the web space may be demonstrable when the lesion is large.