Magnetic resonance imaging and the diagnosis of avascular necrosis of the femoral head.

Low back pain and/or pain radiating to one or both lower limbs can result from causes other than intervertebral disc disease. Recently three patients presented with low back pain radiating down the legs. When CT examination of the lumbar spine proved unrewarding, magnetic resonance imaging (MRI) was performed. Avascular necrosis (AVN) of the femoral head was diagnosed and subsequently treated before femoral head collapse occurred. In patients with unexplained low back pain, AVN of the hip should be considered and ruled out by MRI, even if conventional plain films, polytomes, and radionuclide scans are negative. The early diagnosis of AVN of the femoral head may be critical in determining whether a surgical revascularization procedure might be successful in treatment, or replacement with an endoprosthesis will be necessary, if femoral head collapse has already occurred.