Magnetic resonance imaging of the hip after displaced femoral neck fractures.

This study was designed to determine the sensitivity of magnetic resonance imaging (MRI) in the detection of ischemia or avascular necrosis after displaced intracapsular hip fractures. Magnetic resonance imaging was performed on 20 patients who had hemiarthroplasties performed for Garden IV intracapsular fractures. Sixteen patients had in vivo coronal T1-weighted spin-echo imaging from the day of injury to 60 days after fracture. After hemiarthroplasty, all 20 resected femoral heads had in vitro T1 imaging. A coronal slab was then cut from the center of the femoral head and studied histologically. The in vivo, in vitro, and histologic slides correlated well. None of the MRI images depicted areas of ischemia or avascular necrosis in patterns observed in nontraumatic necrosis. Avascular bone can be indistinguishable from normal bone in both MRI and histologic sections for a considerable amount of time after vascular insult. Magnetic resonance imaging is not a prognosticator for posttraumatic osteonecrosis in the first two weeks after fracture.