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Accessory Tarsal Navicular

 

synonyms:Accessory Navicular, accessory tarsal navicular, accessory scaphoid, os tibiale, os tibiale externum, prehallux, os naviculare secundarium, and navicular secundum

Accessory Navicular ICD-9

  • Consider 732.5  Juvenile osteochondrosis of foot Calcaneal apophysitis Epiphysitis, os calcis Osteochondrosis (juvenile) of: astragalus (of Diaz) calcaneum (of Sever) foot NOS metatarsal: second (of Freilberg) fifth (of Iselin) os tibiale externum (of Haglund) tarsal navicular (of Köhler)

Accessory Navicular Etiology / Epidemiology / Natural History

  • normal variant seen in up to 12% of population (Coskun, N, Surg Radiol Anat 2009;31:19
  • associated with flat feet (pes planovalgus)
  • medial arch pain with overuse

Accessory Navicular Anatomy

  • Accessory navicular is on the medial aspect of the arch, posterior and medial to the tuberosity of the tarsal navicular.
  • Accessory navicular bones have variable attachements with the insertional fibers of the posterior tibial tendon.

Accessory Navicular Clinical Evaluation

  • Erythema, tenderness overlying the navicular tuberosity.

Accessory Navicular Xray / Diagnositc Tests

  • A/P, lateral and obliqueviews of the foot. Often only seen on the external oblique xray.
  • Bone scan can be helpful in unclear cases or patients with bilateral accessory naviculars

Accessory Navicular Classification / Treatment

  • Type I: sesamoid contained within the posterior tibial tendon, 30%.  Rarely symptomatic
  • Type II: most commonly symptomatic; 8-12mm ossicle seperated from the normal navicular.  Separated into 2 types based on the angle of attachment to the navicular. IIa connects with the talar process by a less acute angle:risk for avulsion injury. IIb connects at an acute angle; susceptible to shearing forces.
  • Type III: ossicle united to the navicular by a bony bridge forming a prominent navicular tuberosity. Rarely symptomatic.
  • non-op semi-rigid orthosis with a medial arch support (Bennett J Pediatr Orthop 10:445;1990), activity modifications, shoe modifications to avoid pressure over prominent navicular, NSAIDS, most symptoms resolve spontaneously, short period of cast immobilization if severe.
  • Surgical excision indicated if fails non-op treatment. Consider fixation for patients with very large accessory naviculars.
  • Percutaneous Drilling of symptomatic accessory navicular has demonstrated good results in young athletes. (Nakayma S, AJMS 2005;33:531)
  • Percutaneous drilling technique:
    -general anesthesia  or local
    -1.0mm Kirschner wire introduced percutaneously from the posterior part of the prominence on the accessory navicular
    to the primary navicular through synchondrosis at 5 to 7 different points under radiographic fluoroscopic
    guidance
    -foot immobilized below-the-knee cast with moderate equinovarus position for 3 weeks.

Accessory Navicular Associated Injuries / Differential Diagnosis

Accessory Navicular Complications

Accessory Navicular Follow-up Care

  • Full weightbearing 2 weeks post-op. 
  • 4 weeks: cast removed, active exercise started
  • 6 weeks: light jogging allowed
  • 8 weeks: gradually return to sport specific exercise
  • 10 weeks: full activity if painfree

Accessory Navicular Review References

  •  Zachary C, Foot and Ankle Clinics, 2010;15:337-347
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