Thursday, July 9, 2009

AVASCULAR NECROSIS

This is dead bone from interruption of its vascular supply. This can happen from:
- vessel being damaged (trauma, radiotherapy, vasculitis)
- embolism (lipid, sickle cell)
- venous stasis from compression by osteomyelitis causing increased intraosseous pressure.

I've got no idea why steroids and alcoholism do it.

The nuclear changes come in 4 stages:
1. cold spot because there is no blood supply and therefore no tracer delivery
2. hot spot as new bone is laid down around the edges
3. pain and a hot spot - the pain is because your subchondral bone, which gets its nourishment from the synovium, crumples.
4. the entire femoral head collapses because the repair was not good enough.

The treatment is to replace the dead bone with a bone graft.
If caught early, core decompression to reduce the intraosseous pressure can be tried.

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