Study On The Relationship Between Magnetic Resonance Image Staging And Necrosis Index Of ANFH

ObjectiveTo explore the relationship between Magnetic Resonance Image staging and necrosis index of ANFH by using MRI image, and try to find the critical point of collapse to provide more comprehensive reference standards for the clinical when using Magnetic Resonance Image to predict the possibility of collapse of ONFH.Methods69patients (60femoral heads in all) who were diagnosed of ONFH by Magnetic Resonance Image and of which the images can clearly display the stage in our department during2012July to2014January were retrospected. Each femoral head was classified with the classification system put forward by Hungerford and Lennox. On the other hand, each femoral head was calculated to get a necrosis index (NI) according to the following formula as NI=(the angle of the lesions in the middle of coronal section/180)*(the angle of the lesions in the middle of sagittal section/180).The relation between the MRI staging and NI were compared with histopathology and a critical point of the femoral head collapse was tried to determine.ResultsThe case of the ONFH in each stage were34,32,18and16, and the necrosis index mean value were0.32±0.20(95%CI:0.25-0.39),0.49±0.17(95%CI:0.43-0.55),0.62±0.18(95%CI:0.53-0.71)and0.83±0.23(95%CI:0.70-0.95), the difference of which was proved significantly different (P<0.05). D-value of the necrosis index mean value between any two stage was proved significantly different (P<0.05). There were only three cases of stage Ⅱ whose NI was over0.53, while the NI of each case of stage Ⅲ is over0.53.ConclusionNecrosis index of ONFH extends with the stage aggravating. Necrosis index 0.53can be used as a critical point of collapse. When the MRI images can not showed a clear stage, to combine with the necrosis index can provide more comprehensive information to predict the possibility of collapse of the femoral head.