Accessory ossicles

Last revised by Jeremy Jones on 6 Jan 2025

Accessory ossicles are secondary ossification centers that remain separate from the adjacent bone. They are usually round or ovoid in shape, occur in typical locations and have well-defined smooth cortical margins on all sides.

In most cases, they are congenital in origin, although they may occur as a result of trauma or local degenerative disease 2.

The significance of accessory ossicles is their potential to mimic avulsion fractures.

Cases and figures

  • Figure 1: the foot
  • Figure 2: accessory ossicles of the foot
  • Figure 3: accessory ossicles of the foot
  • Case 1: fabella
  • Case 2: os triangulare
  • Case 3: os trigonum
  • Case 4: os subepicondylare mediale
  • Case 5: Os calcaneus secundarius & os intermetatarseum
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