Osteonecrosis of the Hip | AVN
Pathogenesis / Pathology
- Most therories are = compartment syndrome of femoral head
- Rigid bony head encompasses bone marrow & vessels
- Blood flow in head will be inversely proportional to pressure in the bone marrow
- Final common pathway = intravascular coagulation » venous thrombosis & retrograde arterial occlusion & ischaemia
- Fat embolism theory
- Altered lipid metabolism with steroids or cessation
- Fat emboli in the subarterioles
- Lipocyte hypertrophy theory
- Prolonged steroids ↑ marrow fat
- Accumulative stress theory
- Multiple accumulated stresses on bm & osteocytes
- Acute infarction theory
- Acute disruption of flow e.g. Fracture
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