Current concepts on osteonecrosis of the femoral head

Table 1 Risk factors for osteonecrosis of the femoral head

Direct	Indirect
Femoral head/neck fracture	Chronic corticosteroid use
Hip dislocation	Excessive alcohol consumption
Slipped capital femora epiphysis	Coagulation disorders
Radiation	Hemoglobinopathies
Sickle cell disease	Dysbaric phenomena
Caisson disease	Autoinmune diseases
Myeloproliferative disorders	Smoking
	Hyperlipidemia

Table 2 Ficat and arlet classification system

Stage	Features
0	Normal radiographs (silent hip)
I	Slight abnormality as patchy/opaque areas, minor osteopenia
II	Sclerotic or cystic lesions
	IIa: No crescent sign
	IIb: Crescent sign without flattening of the femoral head
III	Flattening of the femoral head or femoral head collapse
IV	Femoral head collapse and osteoarthritis of the hip (joint space narrowing, osteophytes and acetabular changes)

Table 3 Steinberg staging system

Stage	Features
0	Normal radiograph, bone scan and magnetic resonance imaging
I	Normal radiograph, abnormal bone scan and or magnetic resonance imaging
	IA Mild (involves < 15% of femoral head)
	IB Moderate (involves 15% to 30% of femoral head)
	IC Severe (involves > 30% of femoral head)
II	Cystic and sclerotic changes in the femoral head
	IIA Mild (involves < 15% of femoral head)
	IIB Moderate (involves 15% to 30% of femoral head)
	IIC Severe (involves > 30% of femoral head)
III	Subchondral collapse (crescent sign) without flattening of the femoral head
	IIIA Mild (involves < 15% of femoral head)
	IIIB Moderate (involves 15% to 30% of femoral head)
	IIIC Severe (involves > 30% of femoral head)
IV	Flattening of the femoral head/femoral head collapse
	IVA Mild (involves < 15% of femoral head)
	IVB Moderate (involves 15% to 30% of femoral head)
	IVC Severe (involves > 30% of femoral head)
V	Joint space narrowing and/or acetabular changes
	VA Mild
	VB Moderate
	VC Severe
VI	Advance degenerative joint disease

Table 4 Clinical and imaging differences between osteonecrosis femoral head and subchondral insufficiency fracture

	SIF	ONFH
Age/sex	Elderly/female	30 s to 40 s
Etiology	Osteoporosis/obese	Steroid/alcohol
Bilateral	Rare	50%-70%
Shape of the band	Iregular, disconnected	Smooth
High signal of the proximal	Yes	No
Segment on gadolimium MRI

From Yamamoto T. In: Yamamoto T. Subchondral Insufficiency Fractures of the Femoral Head. Clinics in Orthropedic Surgery 2012: 4: 3. SIF: Subchondral insufficiency fracture; ONFH: Osteonecrosis femoral head; MRI: Magnetic resonance imaging.