UNUSUAL PRESENTATION OF AN OSTEOID OSTEOMA

We present a case of osteoid osteoma of the humerus diagnosed after it presented clinically as impingement syndrome. Clinical and magnetic r esonance imaging data supported impingement, but standard non-surgical treatment did not provide complete pain relief. Subacromial injection resolved the anterior shoulder pain and unmasked medial arm and axill ary pain. Humerus X-rays revealed a lytic diaphyseal lesion, and en-bl oc resection of the humeral mass diagnosed an osteoid osteoma, This ca se is unusual in that only 1% of osteoid osteomas present in the humer al shaft. The clinical features and presentation of impingement and os teoid osteoma are discussed.