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Updated: Nov 6 2023

Accessory Navicular

Images - lateral - wheeless_moved.jpg navicular.jpg pic 1.jpg pic .jpg
  • summary
    • Acessory Navicular is a common idiopathic condition of the foot that presents with an enlargement of the navicular bone.
    • Diagnosis is made with plain radiographs of the foot showing a plantar medial enlargement of the navicular bone.
    • Treatment is generally conservative with shoe modifications and a short period of cast immobilization in patients with symptoms. Surgical excision is indicted for patients with progressive pain that have failed extended nonoperative management.
  • Epidemiology
    • Incidence
      • accessory navicular is a normal variant seen in up to 12% of population
      • majority of patients are asymptomatic
    • Demographics
      • more commonly symptomatic in females
  • Etiology
    • Pathophysiology
      • pathoanatomy
        • occurs as a plantar medial enlargement of the navicular bone
        • exists as accessory bone or as completely ossified extension of the navicular
    • Genetics
      • inheritance pattern
        • autosomal dominant
    • Associated conditions
      • flat feet
      • posterior tibial tendon insufficiency
  • Anatomy
    • Osteology
      • navicular bone normally has a single center of ossification
        • ossifies at age 3 in girls and 5 in boys and fuses at 13 years of age
      • an accessory navicular is a normal variant from which the tuberosity of the navicular develops from a secondary ossification center that fails to unite during childhood
        • the accessory navicular does not begin to ossify prior to age 8
    • Muscles
      • tibialis posterior inserts onto the tuberosity (medial) of the navicular bone 
        • innervated by tibial nerve
    • Ligament
      • plantar calcaneonavicular (spring) ligament originates from sustentaculum tali and inserts on to navicular
        • plantar support for head of talus
      • bifurcate ligament attaches the anterior process of the calcaneus to the navicular and cuboid bones
        • lateral support
      • dorsal talonavicular ligament connects the neck of the talus to the dorsal surface of the navicular bone
        • dorsal support
    • Blood Supply
      • dorsalis pedis artery (dorsal aspect)
      • medial plantar artery (plantar aspect)
      • anastomosis between dorsalis pedis and medial plantar arteries (medial surface of tuberosity)
  • 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 bony enlargement
  • Presentation
    • Symptoms
      • asymptomatic
        • majority of patients are asymptomatic
      • medial arch pain
        • often worse with overuse
        • due to repeated microfracture at the synchondrosis or from inflammation of the posterior tibialis tendon insertion
    • Physical exam
      • inspection
        • may have swelling in region
        • medial foot tenderness
          • firm and tender at the medial and plantar aspect of the navicular bone
  • Imaging
    • Radiographs
      • recommended views
        • AP, lateral, external obliques
          • best seen with an external oblique view
      • findings
        • will see bony enlargement or accessory bone
    • MRI
      • indications
        • evaluation for other pathology
  • Treatment
    • Nonoperative
      • activity restriction, shoe modification, and non-narcotic analgesics
        • indications
          • first-line of treatment
        • modalities
          • the use of arch supports or pads over the bony prominence may be helpful
          • a UCBL orthosis may invert the heel during walking and decrease symptoms
          • orthotics must offload pressure from the accessory navicular or they will exacerbate symptoms
        • outcomes
          • most 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
        • indication
          • recalcitrant cases that have failed extended nonoperative management
  • Technique
    • Excision of accessory navicular
      • approach
        • medial approach to the foot
        • an incision is made from distal third of talus to medial cuneiform
        • identify the posterior tibialis and then reflect the tendon (either plantar or dorsal)
      • resection technique
        • the synchondrosis between the accessory navicular and native navicular can typically be identified easily
        • resect the accessory navicular (a 1/4" curved osteotome may facilitate the resection) through the synchondrosis
        • trim down the body of the navicular (typically with osteotomes and rongeurs) to remove any medial prominence
        • resection is typically in line with medial border of the medial cuneiform
        • do NOT advance the posterior tibial tendon. The advancement does not enhance the result and increases downtime and morbidity
      • flatfoot deformity correction
        • this is not performed concomitantly with the procedure unless the flatfoot is the primary pathology
  • Complications
    • Persistent medial prominence and pain
      • the most common complication is persistent medial prominence and pain when the body of the navicular is not trimmed sufficiently
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