Table 2.

Stage of ON at initial visit and at final followup

Stage	Criteria for staging	Number of shoulders
		At initial visit	At final followup
No necrosis	Normal radiograph and MRI	0	10
Stage I	Abnormal MRI, normal radiograph	120	14
Stage II	Abnormal radiograph with sclerotic or cystic changes in the humeral head but no crescent line	95	52
Stage III	Abnormal radiograph with a crescent sign with humeral head flattening ≤ 1 mm	0	0
Stage IV	Collapse of the humeral head > 1 mm without joint space narrowing	0	51
Stage V	Joint space narrowing	0	38
Stage VI	Advanced degenerative changes	0	50