A 5-year-old boy was seen because of limited motion in his right arm and a hard, bony mass in the back of his shoulder. The mass was diagnosed as myositis ossificans and was excised. Three months later, it recurred and severely limited right arm motion. His medical history was that, shortly after birth, he had had bilateral large, horny, side growths from his skull from forceps trauma. These were excised at 7 weeks of age and did not recur. He had operative treatment for pyloric stenosis with no residual effects. There was no family history of skeletal disease.
Physical examination showed complete absence of glenohumeral motion of the right arm. A warm, bony, hard mass extended from the region of the proximal humerus to the scapula (Fig 1). Other skeletal abnormalities included short great toes with hallux valgus deformities (Fig 2). Both thumbs lacked motion of the distal phalanx. An