Findings: A single PA view of the left shoulder demonstrates a well-defined lytic lesion within the proximal humeral diaphysis in a skeletally immature patient. This lesion demonstrates a narrow zone of transition. A pathologic fracture is seen through this lesion.

Diagnosis: Fracture through a solitary bone cyst.

Discussion: A solitary bone cyst is a common lesion which is seen in tubular bones in patients that are less than 30 years old. Specifically, these most commonly occur within the metaphysis.

These are a centrally located lytic lesion with a thin sclerotic margin. Pathologic fracture through the simple bone cyst is common. When a piece of cortical bone lies within the cyst in its dependent portion, this is know as the fallen fragment sign.

Treatment includes surgical intervention or steroid injection. Occasionally, a simple bone cyst may undergo spontaneous regression.

Reference:
Resnick D, Greenway GD. Bone and Joint Imaging, 2nd Edition.
W. B. Saunders, Philadelphia; 1996:1048-1050.

Return to Musculoskeletal Teaching File Page