Updated: 4/11/2022

Interdigital (Morton's) Neuroma

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  • summary
    • Interdigital Neuromas, also known as Morton's neuroma, is a compressive neuropathy of the interdigital nerve that often leads to plantar forefoot pain.
    • Diagnosis is made clinically with tenderness over the plantar aspect of the involved webspace with a palpable neuroma and a positive Mulder's click on examination. 
    • Treatment is a trial of nonoperative management with a wide shoe box with metatarsal pads. Operative management is indicated for patients with persistent symptoms who fail nonoperative management. 
  • Epidemiology
    • demographics
      • middle-aged females (9:1)
    • body location
      • most commonly involves the 3rd and 4th interdigital nerves between the metatarsal heads (3rd webspace)
  • Etiology
    • Pathophysiology
      • mechanism of injury
        • not fully understood
          • compression/tension of the interdigital nerve around the transverse intermetatarsal ligament
          • repetitive microtrauma
      • pathoanatomy
        • perineural fibrosis and entrapment of the interdigital nerve
  • Anatomy
    • Interdigital nerve
      • location
        • lies plantar to the transverse intermetatarsal ligament between the metatarsal heads
      • components
        • confluence branches of the lateral and medial plantar nerves
  • Presentation
    • Symptoms
      • pain
        • worse with weight-bearing or wearing narrow toe box shoes (e.g. high heels)
        • relief of symptoms by removing shoes and massaging foot
      • paresthesia
        • most commonly on the plantar aspect of web space
    • Physical exam
      • palpation
        • neuroma may be palpable
        • positive web-space compression test
      • provocative tests
        • Mulder's click
          • bursal click may be elicited by squeezing metatarsals together
        • Drawer test at metatarsal phalangeal joint (MTPJ)
          • assess for MTPJ instability
  • Imaging
    • Radiographs
      • recommended views
        • weight bearing AP/lateral/oblique views
      • findings
        • usually normal
        • may see bony deformity
    • Ultrasound
      • indication
        • non-palpable neuroma with clear clinical presentation
      • findings
        • oval, hypoechoic mass oriented parallel to the metatarsal bones
      • outcomes
        • highly operator dependent
    • MRI
      • indication
        • not usually required for diagnosis
        • may be used to rule out other pathologies
  • Studies
    • Common digital nerve block
      • indication
        • confirmatory for accurate diagnosis of interdigital neuroma
      • findings
        • numbness over lateral surface of toe with relief of patient reported pain
  • Differential
    • MTP synovitis
      • consider if there is no relief of pain after well positioned digit nerve block
    • Metatarsalgia
    • Stress fracture
    • MTPJ arthritis
    • Metatarsal head osteonecrosis
    • Neoplasm
    • Lumbar radiculopathy
  • Treatment
    • Nonoperative
      • wide shoe box with firm sole and metatarsal pad
        • indications
          • first line of treatment
        • outcomes
          • results are unpredictable
            • approximately 20% of patients will have complete resolution of symptoms
          • adding anti-inflammatory medications rarely provide any benefit
      • corticosteroid injection
        • indications
          • symptomatic benefit
        • modality
          • usually approached dorsal after isolating the neuroma with palpation or ultrasound
        • outcomes
          • evidence for its effectiveness is weak
          • suggested to provide symptomatic benefit in short term randomized control studies 
    • Operative
      • neurectomy
        • indications
          • failure of nonoperative management
        • techniques
          • dorsal or plantar approach (dorsal most common)
          • neurectomy with nerve burial (bury proximal stump within intrinsic muscles)
          • transverse intermetatarsal ligament release
  • Technique
    • Dorsal neurectomy
      • approach
        • 3 to 4 cm incision just proximal to the involved webspace
        • blunt dissection to avoid injury to branches of superficial peroneal nerve
      • technique
        • spread the metatarsal bones to visualize the webspace, as well as tension the transverse intermetatarsal ligament
        • protecting the neurovacular bundle, transect the transverse intermetatarsal ligament
        • identify the interdigital nerve proximal and distal to the nerve bifurcation
        • resect the nerve at least 3 cm proximal to intermetatarsal ligament
        • reapproximate and repair the transverse intermetatarsal ligament to avoid intermetatarsal head instability
  • Complications
    • Stump neuroma
      • causes include
        • inadequate retraction (traction neuritis)
          • caused by tethering of plantar neural branches that prevent retraction following resection
        • inadequate resection (not proximal enough)
          • most common
          • nerve should be resected at least 3 cm proximal to intermetatarsal ligament
      • resect through plantar or dorsal incision
    • Painful plantar scar
      • increased risk (5%) with plantar incision
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(SBQ18FA.15) A 40-year-old female secretary presents with left forefoot pain that radiates to her 3rd and 4th toes. The pain is exacerbated when she wears high heels. Physical exam is significant for pain and a palpable click with compression of the forefoot. Ultrasound reveals a well-circumscribed hypoechoic mass parallel to the metatarsals within the distal aspect of the 3rd webspace. The patient has failed an appropriate course of conservative management and remains symptomatic. She elects for surgical excision. Compared to a dorsal approach, a plantar approach is associated with:

QID: 211264

Improved clinical outcomes and patient satisfaction

5%

(99/2064)

Increased risk of complications

45%

(935/2064)

Increased risk of sensory loss

6%

(119/2064)

Increased likelihood of complete neuroma excision

33%

(675/2064)

Increased limitation in daily activities

11%

(220/2064)

L 5 A

Select Answer to see Preferred Response

(SBQ18FA.14) A 40-year-old female presents with chronic left plantar forefoot pain, exacerbated by narrow-toed shoes. She has a history of polyarthropathy. Physical exam demonstrates no palpable lesion, but pain is reproduced with forefoot squeeze. She is RF negative but ANA positive. Surgical excision of the painful lesion is performed, and frozen section pathology demonstrates perineural fibrosis without fibrinoid necrosis. These findings are consistent with which of the following diagnoses:

QID: 211253

Morton’s neuroma

81%

(1684/2090)

Neurofibroma

7%

(152/2090)

Benign peripheral nerve sheath tumor

3%

(73/2090)

Plantar fibromatosis

5%

(101/2090)

Rheumatoid nodule

3%

(68/2090)

L 2 A

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