What are the diagnostic and treatment approaches for Morton's neuroma?

Diagnostic and Treatment Approaches for Morton's Neuroma

MRI and ultrasound are the most effective diagnostic tools for Morton's neuroma, with ultrasound offering higher diagnostic capabilities (90% sensitivity, 88% specificity) compared to MRI (93% sensitivity, 68% specificity). 1

Diagnosis

Clinical Evaluation

• Pain in the forefoot, typically between the third and fourth toes (most common) or second and third toes
• Sensation of walking on a pebble or having a fold in the sock
• Pain worsens with tight footwear and weight-bearing activities
• Characteristic pain reproduction with lateral compression of the forefoot
• Mulder's click: palpable/audible click when squeezing the metatarsal heads while applying pressure to the plantar aspect of the interspace

Imaging Studies

1. Ultrasound (First-line imaging)

   • Highest diagnostic capability with 90% sensitivity and 88% specificity 1
   • Advantages:
     • Lower cost than MRI
     • Allows dynamic assessment
     • Enables clinical correlation during examination
     • Can guide therapeutic injections

2. MRI (Alternative or confirmatory)

   • 93% sensitivity but lower specificity (68%) 1
   • Advantages:
     • Increases surgeon confidence in diagnosis and treatment planning
     • Excellent for detecting associated conditions
     • Useful when ultrasound findings are equivocal
   • Note: Gadolinium contrast is not essential but may improve detection 1

Treatment Algorithm

Step 1: Conservative Management (First-line)

• Footwear modifications (wide toe box, low heels)
• Orthotic devices with metatarsal pads to spread metatarsal heads
• Activity modification to reduce pressure on the forefoot
• NSAIDs for pain management

Step 2: Corticosteroid Injections

• Ultrasound-guided injection into the affected intermetatarsal space
• Typically provides temporary relief
• May be repeated if beneficial (limit to 3 injections)

Step 3: Surgical Management

For patients with persistent symptoms after 3-6 months of conservative treatment:

Surgical Technique: Neurectomy (complete excision of the neuroma)

• Approach options:
  • Dorsal approach: Lower risk of painful scarring, recommended as primary approach 1, 2
  • Plantar approach: Better exposure but higher risk of painful hyperkeratotic scarring (7.1% complication rate) 3

Outcomes and Expectations

• Success rates: 80-85% of patients report significant pain relief after neurectomy
• Potential complications:
  • Sensory deficit (common): pulpar hypoesthesia in 12-30% of cases 2
  • Recurrent neuroma (stump neuroma): 10-20% of cases
  • Wound complications: more common with plantar approach (5.2-7.1%) 3
  • Persistent pain: may occur if diagnosis was incorrect or if adjacent interspace also affected

Important Clinical Pearls

• Morton's neuroma is not a true neuroma but perineural fibrosis of the common plantar digital nerve 4, 5
• Most commonly affects the third intermetatarsal space (between 3rd and 4th metatarsals) 2
• Multiple neuromas can occur in adjacent interspaces in approximately 3-7% of patients 2
• Differential diagnosis must rule out metatarsophalangeal joint pathology, stress fractures, and plantar plate tears
• Patients should be counseled about the high likelihood of numbness in the affected web space after surgery

The diagnostic approach should prioritize ultrasound due to its superior diagnostic capabilities, while treatment should progress systematically from conservative measures to surgical neurectomy when necessary, with proper patient counseling regarding expected outcomes and potential complications.