Diagnosis: Osteoid osteoma.
Discussion: Osteoid osteoma comprises approximately 12% of all benign bone neoplasms, most commonly seen in the cortex of long bones. The most common bones to be involved are the femur and tibia. The phalanges of the hands and feet are also commonly involved-- seen in 21% of cases.
The radiographic hallmark is a cortically-based lesion with a radiolucent nidus, and associated dense reactive osteosclerosis. It is most often seen in young patients, and in males more than in females. The symptoms of focal pain are typical.
These lesions are generally seen to good advantage on both plain radiography and CT, though CT offers more anatomic detail. CT will generally show a cortically based lesion, almost always less than 1.5 cm in size and round or oval in shape. It demonstrates low attenuation with surrounding sclerosis which may be mild or extensive. This focal low attenuation is referred to as the nidus. There may be calcification within the nidus. The nidus generally shows post-contrast enhancement.
Most studies have shown that CT is more sensitive at detection of osteoid osteomas than non-enhanced MRI, however, a recent study demonstrated that dynamic contrast-enhanced MR has a similar accuracy to thin-section CT. Osteoid osteomas generally demonstrate the hypervascularity of the nidus of the osteoid osteoma.
Osteoid osteomas demonstrate increased uptake on bone scans.
They are treated either with surgical resection and radiofrequency ablation. NSAIDS can provide symptomatic relief.
