Osteosis

• Also called Aseptic necrosis or Ischaemic necrosis
• Degeneration and necrosis of osseous tissue
• Due to bone marrow pressure and ischaemia resulting from
  • Fractures
  • Excessive heat e.g. horn disbudding
  • Neoplasia (osteosarcoma and lymphosarcoma)
• Grossly:
  • Necrotic bone difficult to recognise
  • Sometimes, periosteum becomes dry, dull and detaches easily
  • On longitudinal section
    • Yellow-white necrotic bone
    • Scattered cancellous and endosteal bone
• Histologically:
  • Empty lacunae or contain dead osteocytes
  • Matrix remains mineralised
• Necrotic bone is slowly resorbed, sequstered or covered by new woven bone
• Persists
• May not be detected radiographically
• Associated with Calve-Legg Perthe's disease