School ager with right hip pain

Radiograph and CT of osteoid osteoma of the femur
AP radiograph of the pelvis shows a round lucent lesion in the right femoral neck. Coronal 2D reconstruction and axial CT without contrast of the pelvis shows the lesion to be centered in the cortex, to have a central calcification in a radiolucent nidus, and to be surrounded by reactive sclerosis. There is also a left hip effusion on the lower left CT image.

The diagnosis was osteoid osteoma of the femur.