Clinical Presentation

A 6-year-old boy with hip pain.

Further Work-up

(A) Anteroposterior radiograph of the pelvis: there is sclerosis of the proximal diaphysis of the right femur that is incompletely imaged (arrow). (B) Axial computed tomography (CT) image: there is a central, well-defined lytic lesion with thick subperiosteal new bone formation (arrow).

Differential Diagnosis

• Osteoid osteoma: These findings are consistent with oste-oid osteoma.

• Osteomyelitis (Brodie abscess): This can be difficult to differentiate from osteoid osteoma. Often, there is a lucent tract extending from the nidus, as well as cortical destruc-tion.

• Stress fracture: