Etiology
AS IT GRIPS 3Cs
Alcohol
- > 4000 ml / week
Steroids
- > 20mg / day
- often bilateral
Idiopathic
- incidence of hypercoagulability
- alcohol probably related to most idiopathic
Trauma
- displaced subcapital
- dislocation
Gout, Gaucher's
Rheumatoid, radiation
Infection, increased lipids, inflamm (arteritis)
Pancreatitis, pregnancy
SLE, Sickle cell, smoking
CRF, chemotherapy, Caisson
DDx
Chondroblastoma / Chondrosarcoma
Enchondroma
Bone island
Bone Scan
No increased uptake
MRI
- key feature central signal same as cancellous bone (intermediate) on both T1 and T2
- rim enhances on both T1 and T2 with contrast
- can be centrally enhancing in acute setting on T2
Prognosis
Pleomorphic sarcoma may arise from long standing bone infarcts