In the above case, there is a central calcification. Is this always present?
No, central mineralisation is often absent, but when present is helpful.
What is the term used for the central translucent region and what is it composed of?
It is called a nidus and consists of a meshwork of vessels, osteoclasts, osteoid, and sometimes woven bone.
What additional information can be expected from an MRI?
MRI typically shows an inflammatory reaction (oedema and contrast enhancement), that may be very intense and involve neighbouring structures. This should not be interpreted as representing an agressive lesion.
What causes inflammation in this bone lesion and how can this be exploited?
Prostaglandine secretion, that responds well to NSAIDs. This feature may help in diagnosis and treatment.
What are the most common locations for osteoid osteomas?
Although they can be found almost anywhere, over half these lesion are found in the femur (especially proximal / neck) and mid tibia. About 11% occur in the foot and ankle region.
A cortical based sclerotic lesion is noted at the lower fibular metaphysis with central sclerotic nidus with regular thin osteolytic halo. Features typical of osteoid osteoma.