Morton's Neuroma
Intermetatarsal Nerve Entrapment
Web Space Involvement
Critical Must-Knows
- 3rd Web Space: Most common location (65%), followed by 2nd web (30%).
- NOT a True Neuroma: Perineural fibrosis from compression, not nerve tumor.
- Mulder's Click: Pathognomonic - palpable/audible click with lateral metatarsal squeeze.
- Conservative First: Wide shoes, metatarsal pad, corticosteroid injection (30-40% response).
- Surgical Neurectomy: Dorsal (most common) or plantar approach; expect permanent numbness.
Examiner's Pearls
- "3rd web space most common (not 2nd)
- "Mulder's click is pathognomonic sign
- "Not a true neuroma - it's perineural fibrosis
- "Conservative fails in 60-70% - surgery indicated
- "Warn patient: numbness is EXPECTED after surgery
Clinical Imaging
Imaging Gallery
Key Exam Points - Morton's Neuroma
The 3rd web space is most common - NOT the 2nd.
- Mulder's Click: Compress metatarsal heads laterally while pressing web space plantarly. Positive = click + symptom reproduction.
- NOT a True Neuroma: Perineural fibrosis from compression, not neoplastic.
- Post-Op Numbness is EXPECTED: Warn patients they will have permanent numbness between affected toes after neurectomy.
- Stump Neuroma: Most common surgical complication (10-15%).
Morton's Neuroma vs Other Forefoot Pathology
| Feature | Morton's Neuroma | Metatarsalgia | MTP Synovitis |
|---|---|---|---|
| Web space (plantar) | Under MT heads | MTP joint | |
| Burning, shooting | Aching, pressure | Aching, swelling | |
| To adjacent toes | Local | Local | |
| Mulder's click +ve | Callus under MT | Drawer test +ve | |
| Removing shoes | Rest | Splinting |
3rd Web Space
Mulder's Click
Not a Neuroma
Stump Neuroma
At a Glance
Morton's neuroma is a compressive neuropathy of the common digital nerve, most commonly affecting the 3rd web space (65%), not the 2nd. It is NOT a true neuroma but rather perineural fibrosis from repetitive compression beneath the transverse metatarsal ligament, with an 8:1 female predominance. Patients report burning, shooting pain radiating to adjacent toes, often relieved by removing shoes. Mulder's click (palpable click with lateral metatarsal squeeze while pressing the web space) is pathognomonic. Conservative management (wide shoes, metatarsal pad, corticosteroid injection 30-40% response rate) is first-line. Surgical neurectomy (dorsal or plantar approach) achieves 80-85% good outcomes; permanent numbness between affected toes is expected and must be counseled. Stump neuroma (10-15%) is the most common surgical complication.
Morton's Neuroma - 3MB
Memory Hook:3MB - 3rd web, Mulder's click, Burning pain. The three key features of Morton's neuroma.
Mulder's Test - CLICK
Memory Hook:CLICK - perform Mulder's test to get the diagnostic click.
Treatment Ladder - SWIM
Memory Hook:SWIM through treatment - Shoes, Wedge pad, Injection, then (neuro)Mectomy.
Complications - SNaP
Memory Hook:SNaP - Stump neuroma, Numbness (expected), Plantar scar. Key complications to discuss.
Overview and Epidemiology
Morton's Neuroma (interdigital neuroma, Morton's metatarsalgia) is a common cause of forefoot pain representing compression neuropathy of the common digital nerve.
Terminology
- Misnomer: Not a true neuroma (not neoplastic)
- Correct Term: Interdigital nerve compression or perineural fibrosis
- Historical: Named after Thomas Morton (1876), though Durlacher described it earlier (1845)
Epidemiology
- Prevalence: 30% of patients with forefoot pain
- Gender: Female predominance 8:1 (high heels, narrow shoes)
- Age: 4th-6th decade most common
- Bilateral: 15-20% bilateral involvement
Web Space Distribution
- 3rd Web: 65% (between 3rd and 4th metatarsals) - MOST COMMON
- 2nd Web: 30% (between 2nd and 3rd metatarsals)
- 4th Web: 3% (rare)
- 1st Web: 2% (very rare)
- Multiple: 2-3% have involvement of more than one web space
Why 3rd Web Most Common?
- Junction of medial and lateral plantar nerve branches
- Nerve thicker at this level
- More tethered → less mobile → more susceptible to compression
Pathophysiology and Anatomy
Relevant Anatomy
Common Digital Nerves:
- Branches of medial and lateral plantar nerves
- Pass beneath transverse metatarsal ligament
- Divide into proper digital nerves to adjacent toes
3rd Web Space Peculiarity:
- Receives branches from BOTH medial and lateral plantar nerves
- Results in thicker, less mobile nerve
- More susceptible to compression
Pathophysiology
Compression Mechanism:
- Nerve passes between metatarsal heads
- Compressed against transverse metatarsal ligament (above)
- Metatarsal heads compress from sides
- Toe extension stretches nerve
Histopathology:
- Perineural fibrosis (NOT neoplastic)
- Demyelination and axonal degeneration
- Renaut bodies (subperineurial fibrosis)
- Endoneurial and epineurial fibrosis
- Small vessel thrombosis and arteriolar thickening
Risk Factors
- Footwear: High heels (transfers weight forward), narrow toe box
- Foot Type: Pes planus, hypermobile first ray
- Activities: Running, ballet, activities with repetitive forefoot loading
- Anatomical: Long metatarsals, tight intermetatarsal space
Clinical Features
History
Pain Characteristics:
- Location: Web space (plantar aspect)
- Quality: Burning, shooting, electric shock-like
- Radiation: To adjacent toes (3rd and 4th in 3rd web neuroma)
- Numbness: Tingling or numbness in affected toes
- Aggravating: Tight shoes, high heels, walking, prolonged standing
- Relieving: Removing shoes, massaging forefoot, rest
Red Flags for Alternative Diagnosis:
- Night pain (consider tumor, infection)
- Swelling (synovitis, gout)
- Constitutional symptoms
- Multiple toe involvement (peripheral neuropathy)
Physical Examination
Mulder's Test (Key Examination)
Technique:
- Hold foot with one hand around metatarsal heads
- Apply lateral compression (squeeze metatarsals together)
- With other hand, press affected web space from plantar to dorsal
- Positive = palpable/audible CLICK + symptom reproduction
Sensitivity/Specificity:
- Sensitivity: 62-98%
- Specificity: 95%
- Highly specific but variable sensitivity
Web Space Compression Test
- Direct pressure on affected web space (plantar and dorsal)
- Reproduces symptoms
- Less specific than Mulder's
Sensory Examination
- May have decreased sensation in adjacent toes
- Two-point discrimination may be abnormal
- Often normal early in disease
Investigations
Clinical Diagnosis
- Diagnosis is primarily CLINICAL
- Imaging not always required if classic presentation
- Used to confirm diagnosis or exclude other pathology
Ultrasound
Findings:
- Hypoechoic, ovoid mass in web space
- Often at level of metatarsal heads
- Dynamic compression may demonstrate lesion
Advantages:
- Widely available, low cost
- No radiation
- Dynamic assessment
- Operator-dependent
Size Threshold:
- Lesions more than 5mm are significant
- Correlation with symptoms improves with size
MRI
Indications:
- Atypical presentation
- Failed treatment (exclude other pathology)
- Preoperative planning for large or recurrent neuromas
Findings:
- T1: Low to intermediate signal mass
- T2: Low signal (fibrosis)
- Located between metatarsal heads
Diagnostic Injection
- Local anaesthetic injection into web space
- Relief confirms diagnosis
- Can be combined with corticosteroid for treatment
Exam Pearl
Morton's neuroma is a CLINICAL diagnosis. Imaging confirms but a positive Mulder's click with classic symptoms is often sufficient for diagnosis and conservative treatment initiation.
Management
Non-Operative Management
First-Line - Shoe Modification:
- Wide toe box (MOST IMPORTANT)
- Low heel (under 2.5cm)
- Soft, cushioned sole
- Avoid pointed shoes
Metatarsal Pad:
- Placed PROXIMAL to metatarsal heads
- Spreads metatarsals apart
- Reduces nerve compression
- 50-60% improvement with shoe mods + pad
NSAIDs:
- Short-term symptom relief
- Not disease-modifying
Corticosteroid Injection:
- 30-40% long-term relief
- Temporary response common
- Technique: Inject into web space from dorsal
- Multiple injections increase risk of fat pad atrophy
- Maximum 3 injections recommended
Other Injections:
- Alcohol sclerosing injections (30% ethanol)
- Multiple sessions required
- Variable results (60-80% in some studies)
Expected Outcomes:
- 30-40% achieve adequate relief
- 60-70% eventually require surgery
- Conservative trial 3-6 months before surgery
Post-Operative Numbness is EXPECTED
Neurectomy involves excising the nerve, so permanent numbness between the affected toes is an EXPECTED outcome, not a complication. Patients MUST be counselled about this preoperatively to avoid dissatisfaction.
Complications
Surgical Complications
Morton's Neuroma Surgery Complications
| Complication | Incidence | Risk Factors | Prevention/Management |
|---|---|---|---|
| Stump neuroma | 10-15% | Insufficient proximal resection, traction | Adequate proximal cut, avoid tension |
| Numbness | 100% | Expected outcome (not complication) | Warn all patients preoperatively |
| Recurrence | 5-10% | Incomplete excision, adjacent web neuroma | Confirm diagnosis, adequate resection |
| Plantar scar pain | 5-8% | Plantar approach, hypertrophic scar | Prefer dorsal approach when possible |
| Wound infection | 2-3% | Diabetes, poor sterility | Standard perioperative antibiotics |
| Transfer metatarsalgia | 3-5% | Altered gait mechanics | Address forefoot mechanics, orthotics |
Stump Neuroma - Most Common Surgical Complication
Occurs in 10-15% of cases. The cut nerve end forms a painful neuroma at the stump. Prevention includes adequate proximal resection without excessive traction. Management includes revision surgery with more proximal resection into the plantar fat pad.
Numbness is Expected - Not a Complication
Neurectomy involves excising the nerve, so permanent numbness between the affected toes is an EXPECTED outcome. Patients MUST be counselled about this preoperatively to avoid dissatisfaction. This is not a complication but a predictable consequence of the procedure.
Special Considerations
Multiple Neuromas
- 2-3% have multiple web space involvement
- MRI helpful for preoperative planning
- May require staged surgery
- Higher risk of complications
Recurrent Morton's Neuroma
Causes:
- Stump neuroma (most common)
- Incomplete excision
- Adjacent web space neuroma (missed)
Management:
- Confirm diagnosis (MRI, diagnostic injection)
- Conservative measures first
- Revision surgery with proximal resection
- Consider plantar approach for better visualization
Differential Diagnosis
- Metatarsalgia: Pain under metatarsal heads, no radiation
- Stress Fracture: Point tenderness over bone, swelling
- MTP Synovitis: Joint swelling, positive Drawer test
- Freiberg's Disease: 2nd MT head AVN, adolescent female
- Plantar Plate Injury: MTP instability, Drawer positive
- Peripheral Neuropathy: Multiple toes, bilateral
Evidence Base
- Compared corticosteroid injection vs surgical excision
- Surgery superior long-term (82% vs 47%)
- Injection provides temporary relief in many
- Surgery recommended for injection failures
- Sensitivity 62-98%
- Specificity 95%
- Highly specific test
- Positive predictive value excellent
- Similar success rates (80-85%)
- Plantar scar pain 10-15% with plantar approach
- Dorsal approach allows earlier weight-bearing
- Surgeon preference determines approach
- 30% ethanol injection series (4-7 injections)
- 60-80% success in selected series
- Avoids surgery in some patients
- Variable results between studies
- Positive Mulder's click predicts good outcome
- Lesion more than 5mm on imaging associated with success
- Multiple web spaces = worse outcome
- Workers' compensation claims = worse outcome
Viva Scenarios
Practice these scenarios to excel in your viva examination
Classic Morton's Neuroma
"A 48-year-old woman presents with burning pain in the forefoot radiating to the 3rd and 4th toes. The pain is worse with high heels and relieved by removing her shoes. Mulder's click is positive."
Diagnosis: This is a Morton's neuroma of the 3rd web space (classic presentation). Key findings: burning pain, radiation to adjacent toes, positive Mulder's click, exacerbated by footwear.
Pathophysiology: This is perineural fibrosis (NOT a true neuroma) from compression of the common digital nerve beneath the transverse metatarsal ligament. The 3rd web is most common as the nerve receives branches from both medial and lateral plantar nerves, making it thicker and less mobile.
Management:
- Conservative first:
- Shoe modification - wide toe box, low heel (most important)
- Metatarsal pad placed PROXIMAL to MT heads
- Corticosteroid injection if persists
- Surgery if fails conservative (3-6 months):
- Neurectomy via dorsal approach (avoid plantar scar)
- Excise neuroma proximal to MT heads
- 80-85% good outcomes
Counsel Patient:
- Numbness between 3rd and 4th toes is EXPECTED after surgery - permanent
- Stump neuroma risk 10-15%
Failed Conservative Treatment
"A 52-year-old woman has had Morton's neuroma symptoms for 9 months despite shoe modifications, metatarsal pad, and two corticosteroid injections. She wants to discuss surgical options."
Assessment: This patient has failed adequate conservative treatment (9 months, shoe mods, pad, 2 injections). Surgery is now indicated.
Pre-Operative Workup:
- Confirm diagnosis - positive Mulder's click?
- Ultrasound or MRI to confirm lesion size, exclude other pathology
- Check for multiple web space involvement
- Assess adjacent toes for other pathology
Surgical Options:
- Dorsal Approach (Preferred):
- Longitudinal incision between 3rd and 4th MT heads
- Divide transverse metatarsal ligament
- Identify nerve, trace proximally, excise at least 3cm
- Allow nerve to retract into soft tissue
- Advantages: avoids plantar scar, early weight-bearing
- Plantar Approach (Alternative):
- Better visualization, reserved for revision or large neuromas
- Disadvantage: plantar scar pain 10-15%
Post-Operative Counselling:
- Numbness between 3rd/4th toes is EXPECTED and permanent
- Heel weight-bearing immediately, normal shoes 4-6 weeks
- 80-85% achieve good outcomes
- Stump neuroma risk 10-15%
Recurrent Symptoms After Surgery
"A patient returns 6 months after Morton's neuroma excision with recurrent burning pain in the same web space. They are unhappy with the result."
Differential Diagnosis:
- Stump Neuroma - most likely (10-15%)
- Incomplete excision
- Adjacent web space neuroma (missed)
- Other pathology (metatarsalgia, stress fracture)
Assessment:
- History: Was there a symptom-free interval? (suggests stump neuroma)
- Examination: Mulder's test, web space tenderness (may be more proximal)
- Imaging: MRI to identify stump neuroma location and size
- Diagnostic injection: Local anaesthetic to affected area
Management of Stump Neuroma:
- Conservative: May try injection, desensitization
- Revision Surgery: More proximal resection
- Plantar approach may provide better visualization
- Cut nerve in deep soft tissue to allow retraction
- Consider nerve capping or translocation to muscle
Prognosis:
- Revision surgery less predictable than primary
- 60-70% success with revision
- Manage patient expectations carefully
MCQ Practice Points
Classic Location Question
Q: Which intermetatarsal space is MOST commonly affected by Morton's neuroma?
A: 3rd web space (65%) - NOT the 2nd. This is a common exam trap. The 3rd common digital nerve receives branches from both medial and lateral plantar nerves, creating a larger and more susceptible nerve.
Pathology Definition
Q: What is the histological nature of Morton's neuroma?
A: Perineural fibrosis - NOT a true neuroma. The pathology shows fibrosis around the digital nerve, not proliferation of nerve tissue. This is why it's more accurately called "interdigital neuritis" or "intermetatarsal bursal swelling."
Clinical Examination
Q: What is Mulder's test and how is it performed?
A: Squeeze the metatarsal heads together with one hand while applying pressure in the interspace from plantar aspect. Positive test: Painful click (Mulder's click) as the neuroma subluxes between metatarsal heads. Sensitivity 60-80%.
Surgical Approach Decision
Q: What is the advantage of the dorsal approach over the plantar approach for neurectomy?
A: Dorsal approach avoids a plantar scar (weight-bearing surface) and allows immediate weight-bearing. The plantar approach has better direct visualization but requires non-weight-bearing for 3 weeks and risks painful plantar scarring.
Australian Context
Australian Epidemiology and Practice
Morton's neuroma is common in Australia, particularly among women wearing narrow footwear and high heels. Conservative management with footwear modification and metatarsal pads is first-line treatment. Surgical neurectomy is typically performed as day surgery in both public and private hospital settings.
Australian Practice Patterns
- Dorsal approach predominant
- Ultrasound widely used for diagnosis
- Most surgery performed by orthopaedic foot/ankle surgeons or podiatric surgeons
- Conservative trial expected before surgery
Podiatric Surgery
- Podiatric surgeons perform Morton's neuroma excision in Australia
- Registration requirements vary by state
- Orthopaedic referral if complex or revision
Indigenous Considerations
- Lower rates of footwear-related pathology
- Access to specialist care limited in rural/remote areas
MORTON'S NEUROMA
High-Yield Exam Summary
KEY FACTS
- •3rd web space MOST COMMON (65%) - not 2nd!
- •NOT a true neuroma - perineural fibrosis
- •Female 8:1, 4th-6th decade
- •Burning pain radiating to adjacent toes
MULDER'S TEST
- •Squeeze metatarsals laterally
- •Press affected web space plantar to dorsal
- •Positive = CLICK + symptom reproduction
- •PATHOGNOMONIC (95% specificity)
CONSERVATIVE
- •Wide toe box shoes (MOST IMPORTANT)
- •Metatarsal pad PROXIMAL to MT heads
- •Corticosteroid injection (30-40% relief)
- •Trial 3-6 months before surgery
SURGERY
- •Neurectomy - dorsal approach (most common)
- •Divide transverse MT ligament, excise nerve
- •80-85% good results
- •Plantar approach: better view but scar risk
COMPLICATIONS
- •NUMBNESS is EXPECTED - warn patient
- •Stump neuroma 10-15% (most common complication)
- •Plantar scar pain if plantar approach
- •Recurrence 10-20%
EXAM TIPS
- •Always say '3rd web most common'
- •Call it 'perineural fibrosis' not 'neuroma'
- •Emphasize post-op numbness is EXPECTED
- •Know Mulder's technique