Morton Neuroma (Interdigital Neuroma)
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- Painful condition of the webbed spaces of the toes
- Features perineural fibrosis of the common digital nerve as it passes between metatarsals
- The interspace between the 3rd and 4th metatarsals is most commonly affected.
- The interspace between the 2nd and 3rd metatarsals is the next most common site.
- Systems affected: musculoskeletal, nervous
- Synonyms: plantar digital neuritis; Morton metatarsalgia; intermetatarsal neuroma
- Mean age: 45 to 50 years
- Predominant sex: female > male (8:1)
Etiology and Pathophysiology
- Lateral plantar nerve joins a portion of medial plantar nerve, creating a nerve with a larger diameter than those going to other digits.
- Etiology not fully understood. Four main theories:
- Chronic traction damage
- Inflammatory environment due to intermetatarsal bursitis
- Compression by the deep transverse intermetatarsal ligament
- Ischemia of vasa nervorum
- Nerve lies in SC tissue, deep to the fat pad of foot, just superficial to the digital artery and vein.
- Overlying, the nerve is the strong, deep transverse metatarsal ligament that holds the metatarsal bones together.
- With each step the patient takes, the inflamed nerve becomes compressed between the ground and the deep transverse metatarsal ligament. This can generate perineural fibrotic reaction with subsequent neuroma formation.
- High-heeled shoes
- Transfer more weight to the forefoot.
- Shoes with tight toe boxes
- Cause lateral compression
- Pes planus (flat feet)
- Pulls nerve medially, increasing irritation
- Female gender
- Ballet dancing, particularly associated with the demi-pointe position
- Basketball, aerobics, tennis, running, and similar activities
- Wear properly fitting shoes.
- Avoid high heels and shoes with narrow toe boxes.