Morton’s Neuroma

Definition

• Compressive neuropathy of the interdigital nerve

Epidemiology

• Women > Men – likely shoewear related

Aetiology

• Shoewear – narrow toe box and high heels (squeezes spaces together)
• Bursal Hypertrophy causes compression
• Position:
  • Most common in 3rd space (between 3rd and 4th toes)
  • Then 2nd space, followed by 4th space
  • 4th space uncommon, 1st space virtually unheard of
    • Think again if these areas are affected

Symptoms

• Pain – well-localised to area
• Worse on weight-bearing, especially in high heels
• Burning or numb sensation around toes

Signs

• Pain on palpation between plantar MT spaces
• Mulder’s Click
  • Click felt while palpating on volar aspect and squeezing MTs
  • Painful click felt

Imaging

XR

• Screening for other causes of metatarsalgia-type pain

USS & MRI

• Both potentially useful, but diagnosis is clinical
• MRI has a high false-positive rate
• USS is user-dependent – may not change management

Management

Non-Operative

• Works for the majority
• Activity modification
• Shoewear alteration – avoid heels or narrow toe boxes
• Metatarsal bar to offload forefoot
• Steroid Injection
  • Can work permanently
  • Probably most accurate under USS guidance
  • Diagnostic and therapeutic value

Surgical

• Commonly through a longitudinal incision in IM space
• Nerve lies deep to Transverse Metatarsal Ligament (TMTL)
• Surgical Steps:
  • Divide TMTL
  • Dissect nerve
  • Key: Excise nerve and all its fibres just proximal to the bifurcation and a few centimetres proximal to web space
  • Send for histology to confirm you have excised the original neuroma
  • Minimises risk of neuroma formation

Results

• 80-85% cure rate
• Improved by correct patient selection

Complications

• Primary complication is recurrence – neuroma formation
• Usually due to insufficiently proximal nerve resection