A well-nourished 17-year-old of average height and weight was referred for evaluation of persistent right lower leg pain of 3 months' duration. He was not taking any medications, had no allergies, and denied trauma to the area.
The pain was localized to the mid aspect of the right anterolateral tibia; it was exacerbated by walking and exercise and slightly alleviated with rest and ibuprofen. A subtle lump was palpable in the mid shin area laterally.
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Plain radiographs of the tibia and fibula revealed marked sclerosis and cortical thickening at the mid diaphysis of the tibia; an oval lucency was detected within the posterolateral cortex, consistent with a nidus (A). A helical CT scan demonstrated cortical hyperostosis that involved the posterolateral aspect of the tibial cortex; the nidus measured 7 × 14 mm (B). Osteoid osteoma was diagnosed.
Osteoid osteomas account for about 10% of all benign bone tumors.1 They can arise in any bone. The typical tumor site is the cortical bone, most commonly the tibia and femur.1,2 The tumors develop in immature bones and thus are usually found in persons younger than 20 years. The male-to-female ratio is 2:1.
The tumor is composed of osteoblasts and an osteoid that forms a small (less than 2 cm) radiolucent nidus, which is surrounded by an increased neural and arterial supply. The pain probably results from the increase in neural cells around the nidus; it typically worsens at night and is relieved by NSAIDs or aspirin.2,3 The abnormal growth is likely a response to the increased arterial supply around the nidus; in some patients, this may be palpable.1
Osteoid osteomas can be managed with watchful waiting and NSAIDs as needed, surgical excision and curettage, or radiofrequency (RF) ablation.1 Surgery can be painful and inaccurate identification or incomplete excision of the tumor can lead to recurrence. RF ablation is more widely used and allows for osteonecrosis without injury to the adjacent bone.1
This patient and his parents chose RF ablation. Six months after treatment, he had no symptoms and the lesion had not recurred.