Clinical History.—This 9-year-old boy fell from his bicycle and landed on his left shoulder. Following the injury, the shoulder and upper arm became swollen. There was decreased motion of the left arm, which he was unable to lift.
Physical Examination.—He was a well-developed and well-nourished boy in general good health. The only positive findings on examination were limited to the left arm. There was soft tissue swelling of the upper arm and shoulder area. There was some pain elicited in the shoulder area when his arm was moved. He was unable to lift the arm.
The laboratory studies all yielded normal results.
Denouement and Discussion
Solitary Bone Cyst
Solitary bone cyst is not a true neoplasm and the pathogenesis is unknown. Several theories have been advanced as to the cause of bone cyst and Edeiken and Hodes1 say "the most likely explanation of bone cyst is