Teaching Case

Six month history of swelling and pain on the dorso-medial aspect of right mid foot.

The boy presented with a six month history of swelling and pain on the dorso-medial aspect of his right mid foot. The swelling had increased in size and was not associated with trauma. On examination there was a well-defined 1cm x 1cm swelling on the medial aspect of the right foot with no overlying skin changes. Plain AP and oblique radiography revealed an accessory well corticated ossicle adjacent to the medial cuneiform bone. Surgical excision of the bone was subsequently performed and the patient made an uneventful recovery with resolution of symptomology.

Numerous accessory bones and ossification centres in the foot and ankle have been described. In the majority of cases these represent incidental findings on radiographs and do not cause symptomology (1). Occasionally these ossicles can become painful due to fracture, degenerative changes, avascular necrosis, and irritation or impingement of adjacent soft tissue (2), or can themselves be mistaken for fractures of adjacent normal bones. The average age of ossification of the medial cuneiform is at two years (3). Bilateral bipartite medial cuneiforms have been reported as an incidental finding on CT scan whilst investigating a fractured intermediate cuneiform (4); however these were not symptomatic. Discriminating between normal skeletal development (including normal variants) and skeletal pathology can be a challenge. An accessory well corticated medial cuneiform ossicle must not be mistaken for a fracture especially if there is pain. An awareness of possible anatomic variants is essential to improve correct diagnostic evaluation