Abstract. A symptomatic osteoid osteoma of the left femoral head in a 14-year-old boy is described.Osteoid osteomas are common benign bone tumours found typically in the long bones of the lower limbs, usually in the metaphyses or diaphyses. They frequently cause persistent, aching pain, worse at night and relieved by aspirin. The typical radiologic appearance is a lucent nidus with surrounding dense cortical thickening. In this case, the location in the left femoral head is unusual and we have been unable to find any reference to this site in the English language literature.
Case reportA 14-year-old boy presented with a 4-month history of increasing pain in the left hip and along the thigh to the left knee.Examination demonstrated slight limitation of internal rotation, flexion and extension, mainly due to discomfort. Straight leg raising was also slightly diminished. * Present address: Clinical Fellow in Magnetic Resonance Imaging, Princess Margaret Hospital, University of Toronto, 500 Sherbourne St., Toronto, Ontario, M4X 1K9, Canada AP and lateral radiographs of the left hip were normal. No loose body or other abnormality was identified. The bone trabecular pattern was also normal.99mTc MDP bone scan (Fig. 1) revealed slightly increased activity in the medial half of the left femoral head. The blood flow and blood pool images of both hips were within normal limits.CT scan of the left femoral head (Fig. 2) showed a rounded lucent area in the anterolateral portion of the left capital femoral epiphysis. It had a dense central nidus and the lucent area was surrounded by dense sclerotic bone.From the CT scan, the lesion was felt to be an osteoid osteoma. No attempt at surgical removal of the lesion was made as it was felt this would produce unnecessary damage to the articular surface of the femoral head. The patient was therefore treated conservatively with aspirin with relief of his pain.
DiscussionOsteoid osteoma is a benign bone tumour seen predominantly in young males in the first three decades of life. It is fairly common; in a Mayo clinic series, osteoid osteoma comprised 11% of all benign bone tumours [71.The commonest sites of predilection are the metaphyseal and diaphyseal regions of the tibia and femur, especially the proximal femur. Lesions may be seen in other long bones, the tubular bones of the hands and feet, and even in the appendicular segments of the spine. R !_ Fig. 1. 99mTc MDP bone scan of both hips. There is increased activity in the medial half of the left femoral head (arrowheads)
