A 6 cm long and 4 x 4 mm wide bone fragment is located on the caudo-lateral aspect of the right ulna. The bone fragment begins 2 cm distal to the Tuber olecrani, tapers and ends in a pointed tip. The fragment is sclerotic when compared to the adjacent cortex and is surrounded by a radiolucent rim. A severe brush border periosteal reaction extends from the olecranon along the ulna to end distal of the fragment. The periosteal new bone appears more lucent when compared to the cortical opacity.

An isolated, elongated, smoothly marginated mineral opacity is evident cranial to the humeral condyles.

• Sequestrum right ulna with severe surrounding periostitis
• Small bony fragment cranial to humeral condyles

The changes are suggestive of a traumatic insult which has led to sequestrum formation of the ulna. The small bony fragment cranial to the humeral condyles can also be traumatic in origin and represent for example a chip fracture of the radial head. Differential diagnosis is dystrophic mineralisation of a tendon.