Interdigital Neuroma (Morton Neuroma)

Interdigital Neuroma (Morton Neuroma)

Jeffrey S. Boberg

Cameron L. Eilts

Morton in 1876 attributed associated clinical symptoms of a neuroma to an “affection of the fourth metatarsophalangeal joint” and to injury of the common plantar digital nerve (1). This idea has been supported by characteristic histologic changes that reveal degeneration of the myelinated fibers, thickening and hyalinization of the walls of the epineural and endoneural vessels, and fibrosis of the epineurium and perineurium. These histologic findings alone, however, do not fully explain the pathophysiology. Morscher et al (2) compared 23 biopsies taken from patients with typical intermetatarsal neuroma symptoms and compared them to 25 plantar nerves taken from cadaver specimens. Examination revealed that the only difference between the two specimens was the diameter of the resected nerves. Both groups demonstrated epineural and perineural fibrosis. In addition, the myelinated fibers were reduced in number and size, which is not typical of a traumatic neuroma.

The etiology of interdigital nerve hypertrophy remains a subject for debate. Nissen (3) believed an interdigital neuroma was the result of ischemia. In 1979, Ha’ Eri et al (4) microscopically examined 106 specimens and found that an increase in connective tissue from repetitive trauma and also arterial sclerosis within the interspace resulted in nerve atrophy. Nunan and Giesy (5) postulated that either excessive pronation with hypermobility of the metatarsals or a pes cavus foot type may cause excessive stretching on the nerves causing direct trauma and symptoms.

Recent reports postulate the condition is caused by interdigital nerve impingement against the deep transverse intermetatarsal ligament (DTIL) and should be referred to as intermetatarsal compression neuritis (6). However, a new anatomic study does not support this theory. Kim et al (7) demonstrated that the bifurcation area of the common digital nerve is distal to the DTIL.

Jul 26, 2016 | Posted by in MUSCULOSKELETAL MEDICINE | Comments Off on Interdigital Neuroma (Morton Neuroma)

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