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Table 1 Preoperative stages of the 71 hips classified according to the Steinberg's classification system.

From: Indications for free vascularized fibular grafting for the treatment of osteonecrosis of the femoral head

Stage Characteristics Number of Hips
0 Normal radiographs, bone scan, and MR images 0
I Normal radiographs, abnormal bone scan, and MR images  
   A: mild < 15% of head involvement 0
   B: moderate 15% to 30% 2
   C: severe > 30% 1
II Abnormal radiograph  
   A: mild < 15% of head involvement 1
   B: moderate 15% to 30% 3
   C: severe > 30% 24
III Subchondral collapse producing a crescent sign  
   A: mild < 15% of articular surface 0
   B: moderate Crescent beneath 15% to 30% 1
   C: severe Crescent beneath > 30% 2
IV   
   A: mild < 15% of surface collapsed and depression is < 2 mm 2
   B: moderate 15% to 30% collapsed or 2 to 4 mm depression 8
   C: severe > 30% collapsed or > 4 mm depression 24
V Joint narrowing with or without acetabular involvement  
   A, B, or C Average of femoral head involvement, as determined in Stage an d estimated acetabular involvement 3
VI Advanced degenerative changes 0