Updated: 1/6/2018

Interdigital (Morton's) Neuroma

Topic
Review Topic
0
0
Questions
2
0
0
Evidence
2
0
0
https://upload.orthobullets.com/topic/7041/images/idn 2.jpg
https://upload.orthobullets.com/topic/7041/images/mortons.jpg
Introduction
  • Compressive neuropathy of the interdigital nerve
  • Epidemiology
    • demographics
      • middle-aged females (9:1)
    • body location
      • most commonly involves the 2nd and 3rd interdigital nerve between the metatarsal heads
  • 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 diagnosis
  • 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 
Surgical 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)
        • most common
        • caused by tethering of plantar neural branches that prevent retraction following resection
      • inadequate resection (not proximal enough) 
        • 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
 
 

Please rate topic.

Average 4.8 of 15 Ratings

Thank you for rating! Please vote below and help us build the most advanced adaptive learning platform in medicine

The complexity of this topic is appropriate for?
How important is this topic for board examinations?
How important is this topic for clinical practice?
Questions (2)
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
ARTICLES (2)
Topic COMMENTS (11)
Private Note