Posttraumatic necrosis of the talus: the Hawkins sign versus magnetic resonance imaging.

Magnetic resonance imaging (MRI) is reported to be more sensitive than plain radiographs, computed tomography, or radionuclide bone scanning in detecting osteonecrosis. Few cases of MRI scans falsely negative for osteonecrosis have been reported. A 36-year-old man with posttraumatic necrosis of the body of the talus proven by biopsy had three serial MRI scans that were interpreted as showing the talus to be viable. Eight weeks after injury, the plain radiographs did not show subchondral resorption of bone in the talus (Hawkins sign) and, thus, did correctly indicate necrosis. Most likely a non-union of the talus neck fracture resulted in the false-negative MRI scans.