Presentation
Several years of occasional mild pain in the medial aspect of the left foot.
Patient Data
Lateral x-ray exhibits the Os trigonum (the bone particle posteriorly to the talus).
Lateral and antero-posterior x-rays show another bone particle in parallel alignment with the long axis of the 5th metatarsal diaphysis, which is highly suggestive of an unfused apophysis.
On the lateral projection adjacent to the 5th metatarsal base there is an undetermined ossified body, that is also seen on the dorsoplantar and oblique views
XR zoomed & with annotations
These images emphasizes the Os trigonum (is outlined in orange), unfused apophysis of the proximal 5th metatarsal (outlined in blue) and the undetermined ossified body (outlined in green).
Case Discussion
Accessory ossicles can be found in almost every part of skeleton, but the accessory ossicles of foot are the most common. Usually these skeletal variations occur due to unfusion of the accessory ossification centers. The most common accessory bones of the foot in descending order of frequency are: Os trigonum and Os navicular 1.
The unfused apophysis of the proximal 5th metatarsal should be carefully evaluated so as to distinguished it from a wide range of possibilities, such as: Os vesalianum pedis, Os peroneum, Iselin's disease, avulsion fracture, Jones and stress fracture of the fifth metatarsal 2.
Contributed by Dr. Guilherme Pioli Resende M.D. and Dr. Arthemizio Antônio Lopes Rocha M.D.
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