Osteonecrosis complicating comminuted fracture of proximal humerus. A, Oblique coronal T1-weighted image demonstrates displaced fracture through neck of proximal humerus (curved arrow). Geographic region of abnormal marrow within articular fragment is characteristic of osteonecrosis (long arrow). B, Oblique coronal fat-suppressed, T2-weighted image shows hyperintense rim of reactive tissue (arrow) surrounding now hypointense fatty avascular marrow.