Osteoid osteoma of the hamate.

Uncommonly affecting the carpus, osteoid osteoma, a benign bone lesion, will involve the hand in 10% of cases. With negative initial radiographs and persistent tenderness in a 15-year-old boy after a fall, a wrist magnetic resonance imaging revealed extensive hamate edema without a fracture line. He was casted for a presumed hamate fracture. Without complaints of dysthesias or weakness, marked localized tenderness over the hamate, mild dorsal carpal edema, and limitation of wrist motion was noted 6 months later despite immobilization and rest. A computed tomography (CT) scan revealed a round, osteolytic lesion ulnarly at the hamate hook's base. Within the classic zone of sclerosis, a central calcification was visualized. Irregular periosteal bone formation is seen on the hamate hook and the dorsal aspect of the hamate. A volar curetting of the lesion was performed without grafting as stability was not threatened. Permanent sections consisted of a bony nidus with compact sclerotic, poorly organized osteoid. The central tissue was vascular with many osteoblasts, fibroblasts and mesenchymal cells. Following surgery, his pain remitted completely. Characteristics of pain and swelling have been consistent among reported cases of osteoid osteoma. Presentation may include warmth, erythema and restriction of motion. A delay in diagnosis is present in all cases involving the hamate usually due to negative plain radiographic findings. Magnetic resonance imaging findings further delayed diagnosis and treatment. Lesions are more accurately and frequently diagnosed in children with the use of CT.