Fig. 1.

Aneurysmal bone cyst (ABC) of the left iliac wing adjacent to the acetabulum in a 14-year-old-male that presented with worsening left hip pain in the past 8 months. a Anteroposterior radiograph reveals a very large expansile, osteolytic lesion of the left ilium extending into the superior acetabulum. b Axial T2-weighted magnetic resonance imaging (MRI) reveals multiple fluid levels characteristic of an aneurismal bone cyst. c Coronal T2-weighted MRI demonstrating extension into the supra-acetabular region with no involvement of the joint. d Anteroposterior pelvic radiograph 2 years postoperative reveals no signs of local recurrence and complete bone healing of the entire cystic area. The patient at most recent follow-up was very active and had returned to high school baseball, wrestling, and football without limitation