[Avascular necrosis of the femoral head:correlation of imaging and pathological findings].

OBJECTIVE: To investigate the relationship between imaging and pathological findings of avascular necrotic of the femoral head (ANFH). METHODS: A comparison among of conventional radiography, computerized tomography (CT), magnetic resonance imaging (MRI), gross section and pathological examinations was performed in 20 femoral heads in 15 patients undergoing total hip replacement for established ANFH. RESULTS: ANFH involved the anterosuperior aspect of femoral head in all hips. Necrotic femoral heads consisted of cartilage, necrotic area, reactive repaired area and extralesional area. The reactive repaired area surrounded necrotic area. Imaging findings: 1) on conventional radiography and CT, as compared with the extralesional area, the necrotic area appeared to be of an equal density (11), a lower density (7) and a higher density (2) On MRI, the necrotic areas revealed adipose intensity (3), blood like intensity (1), aquatic intensity (2), fibrous intensity (9) and non-homogeneous intensity (5); 2) the reactive repaired area separated the necrotic and extralesional areas. Both on plain radiography and CT, the reactive repaired area showed a sclerotic band surrounding the necrotic area and a hypo-density inner line adjacent to sclerotic band was seen in 11 femoral heads on CT and 7 on conventional radiography. A band of low signal in the proliferative zone was seen on MRI in all hips and a rim of high signal intensity inside the low-signal margin (double-line sign) was seen in 3 hips on T2W images. CONCLUSION: Conventional radiography, CT and MRI can display the grossly discernable necrotic, reactive repaired and extralesional areas accurately. Characteristic imaging findings are observed in the reactive repaired area.