Osteoid osteoma in the medial malleolus

A case of osteoid osteoma in an unusual location is reported. The osteoma was diagnosed, and the nidus was localized to the anterior colliculus of the medial malleolus based on the clinical symptoms and on the findings in radionuclide bone scanning, tomography, and computerized tomographic (CT) scanning. After precise radiographic localization of the nidus, it was determined that the lesion could be excised surgically without compromising the ankle joint. The tumor was removed by en block excision and curettage. At 10 months follow-up, the patient was free of pain without impairment of function.