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Accessory Navicular

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Topic updated on 02/03/13 4:55pm
Introduction
  • Accessory navicular is a normal variant seen in up to 12% of population
    • majority of patients are asymptomatic
      • more commonly symptomatic in females
  • Pathoanatomy
    • occcurs as a plantar medial enlargement of the navicular bone
      • usually does not begin to ossify prior to age 8
    • exists as accessory bone or as completely ossified extension of the navicular
Anatomy
  • Ossification of navicular bone
Classification
 
Radiographic Classification
Type 1 Sesamoid bone in the substance of the tibialis posterior insertion
Type 2 Separate accessory bone attached to native navicular via synchondrosis
Type 3 Complete boney enlargement
 
Presentation
  • Symptoms
    • medial arch pain that is worse with overuse
      • due to repeated microfracture at the synchondrosis or from inflammation of the posterior tibialis tendon insertion
  • Physical exam
    • tender at the medial and plantar aspect of the navicular bone
    • flexible flatfoot (pes planus)
Imaging
  • Radiographs
    • recommended views
      • AP, lateral, external obliques
        • best seen with a external oblique views  
    • findings
      • will see bony enlargement or accessory bone
  • MRI
    • helps delineate insertion of tibialis posterior tendon 
Treatment
  • Nonoperative
    • activity restriction, shoe modification, and non-narcotic analgesics
      • indications
        • as first line is of treatment
      • modalities
        • the use of arch supports or pads over the boney prominence may be helpful
      • outcomes
        • nearly all children and adolescents who have a symptomatic accessory tarsal navicular bone become asymptomatic when they reach skeletal maturity
    • short period of cast immobilization
      • indications
        • pain is refractory to activity modification and shoe modifications
  • Operative
    • excision of accessory navicular  
      • indications
        •  recalcitrant cases that have failed extended nonoperative management
Technique
  • Excision of accessory navicular
    • bone should be resected flush with the medial cuneiform
      • most common cause of persistent symptoms after surgery is inadequate bone resection
    • may need to transfer tibialis posterior tendon to the undersurface of the navicular
      • will improve symptoms but will not correct flatfoot deformity

 

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Qbank (2 Questions)

TAG
(OBQ08.160) An 18-year-old male complains of a painful prominence over his medial midfoot for the past 2 years. NSAIDs and orthotics have failed to provide relief. Physical exam demonstrates a firm, nonmobile, tender bump on the medial midfoot with no skin changes. A radiograph is provided in figure A. Which of the following is the best treatment option? Topic Review Topic
FIGURES: A          

1. Custom AFO brace
2. Steroid injection
3. MRI of the foot and chest CT scan
4. Open biopsy
5. Surgical excision

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