In fifteen patients who had a subcapital fracture of the femoral neck
(twelve displaced fractures and three non-displaced fractures), magnetic
resonance imaging of the femoral head was done with two-dimensional Fourier
transform spin-echo technique within forty-eight hours of injury. The
magnetic resonance image did not show avascular necrosis of the femoral
head in any of the patients. In eleven patients, there was a decreased
signal at the base of the femoral head, immediately adjacent to the
fracture. This decreased signal corresponded to a recognized band of
necrosis and hemorrhage next to the site of the fracture and was not
related to the viability of the femoral head. No other changes were seen on
the images. We concluded that this type of magnetic resonance imaging is
inadequate to determine the viability of the femoral head within
forty-eight hours after a patient sustains an acute intracapsular fracture
of the femoral neck.