Osteoid Osteoma

George M Wu, MD
Nayer Nikpoor, MD

October 18, 1994

Presentation

Imaging Technique

Imaging Findings

Bone scintigraphy indicates increased blood flow (arrow) and increased blood pooling (arrow) in the distal one-third of the left tibia. On the delayed image, there is a fusiform area of increased radiotracer uptake in the left tibia surrounded by areas of less intense radiotracer uptake (arrows). Conventional radiographs demonstrate thickened cortex with central linear lucency (arrow) and mild periosteal reaction in the corresponding area of the patient's distal left tibia.

Differential Diagnosis

Diagnosis

Discussion

The hallmark of osteoid osteoma is dull or aching pain, initially mild and intermittent but increasing in intensity and persistence with time. Soft tissue swelling and tenderness are often associated with progression of the disease. Because of the indolent nature of early osteoid osteoma, patients may wait months to years before seeking medical attention. Additional clinical manifestations depend on the age of the patient and the location of the lesion. For example, osteoid osteoma can cause growth aberrations, muscular atrophy and skeletal deformity in the immature skeleton. Fifty to sixty percent of osteoid osteoma occur in the femur or tibia, and seventy percent in the long bones. Twenty percent of cases are located in the hands and feet. The vertebral column, innominate bone, skull, mandible, maxilla, clavicle, scapula, ribs and radius are infrequent sites of involvement.

The classic radiographic appearance of osteoid osteoma is a centrally located oval or round radiolucent area, measuring less than 1 cm in diameter, surrounded by a zone of uniform bone sclerosis. However, this appearance may be modified according to the specific skeletal location and the precise site of involvement in that bone. In the long tubular bones, the osteoid osteoma is typically located in the diaphyseal cortex; the nidus is a radiolucent lesion with peripheral bone sclerosis and cortical thickening from endosteal and subperiosteal new bone formation. The nidus may be radiolucent or contain variable amount of calcification. The degree and extent of the sclerotic reaction surrounding the nidus is also variable. Rarely, there may be more than one nidus in a single osteoid osteoma, or more than one osteoid osteoma, each with its own nidus, may be found in the same bone.

On scintigraphy, osteoid osteoma appears as an increased area of radiotracer uptake on the blood-flow, blood-pool and delayed phases of the bone scan. There is usually an intense area of radiotracer uptake in the region of the nidus and less intense uptake in the sclerotic bone. This pattern has been designated as the double-density sign and is virtually diagnostic of osteoid osteoma. Osteomyelitis has a more uniform pattern of radiotracer uptake, and an abscess cavity may actually have decreased radiotracer uptake.

Computed tomography can be helpful in cases where conventional radiography and scintigraphy are ambiguous. It is most useful in defining osteoid osteoma in the spine, osseous pelvis and femoral neck.

Surgical removal of the nidus results in complete cure. Recurrences are rare and usually result from incomplete resection due to a second nidus in the lesion or a second lesion in the same bone or different bone. Failure of surgery to relieve the patient's symptoms may also suggest that the diagnosis of osteoid osteoma was incorrect. There has been no reports of malignant transformation or metastasis from the lesion.

References

2. Resnick D and Niwayama G. Tumors and tumor-like lesions of bone: imaging and pathology of specific lesions. In: Diagnosis of bone and joint disorders. Philadelphia: WB Saunders, 1988:3620-35.

3. Smith FW, Gilday DL. Scintigraphic appearances of osteoid osteoma. Radiology, 1980;137:191-5.

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