Accessory navicular bone

When Os Tibial externum ( Syn: externum navicular, navicular secundarium, navicular acessorium, navicular bipartitum; engl. Accessory tarsal navicular, accessory tarsal scaphoid ) is a common (10-16 %) variation in the scaphoid of the foot ( navicular ). In about half the cases it occurs on both sides.

Clinic

It is a hard swelling in the sense of an absorber to the inner tarsus, about an inch below and in front of the medial malleolus tip, ie at the scaphoid, palpable. Occasionally, on a load and pressure pain, especially if this malformation occurs together with a puncture. The diagnosis is confirmed with a radiograph.

Variants

  • Type 1: The os tibial externum in the narrower sense is a 2-3 mm large, rotund sesamoid bone at the insertion of the tendon of the tibialis posterior. It does not form cartilage to the scaphoid.
  • Type 2: The os tibial externum is triangular and up to 12 mm in size. This has a cartilage connection to the scaphoid. This type is more than 50 % of the most common. There is a failure to fusion of the bone cores from which the scaphoid bone forms in early adolescence.
  • Type 3: Here's the scaphoid constitutionally widely protruding inwardly formed ( navicular cornutum, English:. Cornuate navicular ). This is in contrast to the first two identify forms no gap.

Therapy

Most the os tibial externum is asymptomatic, so makes no complaints. A treatment is then required. Otherwise, it is treated with custom-made deposits with soft padding on the distention. Only in very exceptional cases, in case of failure of conservative therapy and severe suffering, surgery should be considered.

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