A pelvic radiograph done for other reasons shows increased sclerosis of the right femoral head with normal appearance of the right hip joint.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEirtG2YoMyus4rRWcU6Zb3NOvy4fup2w5Bv7prdwRus9Zl9aAmg_zcjX0bEho8SLySZEUa7XlpKJ9p8HpdArL866e2O90gJAXy8uUKAcJnCEJ5oILuyJgbTRyAJdOn_zsUChyrDLHJ4cQ/s320/avascular_necrosis_CT.jpg)
CT scan performed later confirms the finding of avascular necrosis (areas of mixed lysis and sclerosis in the femoral head with normal hip joint).
Facts
- Relatively common disease, femoral head most common site
- Predisposing factors: hip dislocation, femoral neck fracture, corticosteroid usage, collagen vascular disease, hemoglobinopathies
- Often affecting young adults
- Early diagnosis is important to establish AVN as the cause of hip pain (excluding infection, neoplasm, fracture, or tendon tear) and to stage AVN for treatment
Imaging
- Radiograph most widely used as initial study. Both AP and frogleg views should be obtained to detect subchondral fracture or cortical depression. It may be normal, abnormal or nonspecific.
- CT can be done to determine severity of secondary degenerative joint disease or extent of collapse of the femoral head (use for planning of either osteotomy or joint replacement)
- MRI is the most sensitive imaging method.
Imaging Pathway
- Suspicious for AVN in a high-risk patient with hip pain -> AP and frogleg lateral radiograph of the symptomatic hip
- If radiograph is definite for AVN -> MRI to look for AVN in the opposite side IFknowledge of asymptomatic AVN in the opposite side is clinically important
- If radiograph is equivocal or normal -> MRI to confirm the diagnosis of AVN and to exclude other causes
- If MRI cannot be performed, a bone scan with SPECT imaging reasonable
Reference:
www.guideline.gov/content.aspx?id=15734
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