Magnetic Resonance Imaging of Radiographically Negative Avascular Necrosis of the Femoral Head

Yoo, Myung Chul; Cho, Youn Jae; Kim, In Whan; Park, Gyoung Chean

Abstract

Magnetic resonance imaging has been recognized as more suitable method than radiography and bone scan for the early detection of avascular necrosis of the femoral head. Segmental collapse is the most important factor in the prognosis of patient with avascular necrosis. The authors studied the appearance of avascular necrosis with both radiography and magnetic resonance imaging and then determined which lesions remained unchanged, progressed or led to collapse, as determined wih follow-up radiography in the 61 radiographically negative avascular necrosis of the femoral heads. 1. The necrosis-progression rates according to the extent were 36% in Extent A, 83% in Extent B, and 93% in Extent C. The necrosis-progression rate was significantly correlated with the extent of necrosis initially involved. 2. The necrosis-progression rates according to the location were 37% in Type I, 70% in Type II, and 95% in Type III. The necrosis-progression rate was significantly correlated with the weight bearing area of necrosis initially involved. 3. There was no correlation between necrosis-progression rate and signal intensity. 4.All of the cases which had combinations of the Extent C, and Type III location showed progression. 5. None of the femoral heads that had been treated at the radiographically negative stage was collapsed, but 35% of the femoral heads those had been treated at the radiographically positive stage were collapsed. 6. In the cases which were treated early, all of the Extent C, Type III were collapsed, but none of the Extent A, Type I were collapsed. In conclusion, magnetic resonance imaging is useful for evaluation of the risk of collapse or for anticipation of the prognosis of the affected hip joint as well as for the early diagnosis of radiographically negative avasular necrosis of the femoral head.