Stages of fracture healing (HIDOCR)

1. Haematoma formation
   • size limited by elastic periosteum and arterial spasm
2. Inflammatory phase
   • vascular dilation, exudate, polymorph infiltration
3. Demolition phase
   • Macrophages digest clot, fibrin and debris
   • Macrophages & osteoclasts remove dead bone fragments
4. Organisation
   • Granulation tissue formation with ingrowth of capillary loops from below the periosteum and from fracture bone ends
5. Early callus/late callus
   • Osteoid laid down in haphazard arrangement of fibril
   • Mineralise to form woven bone +/- cartilage
   • Woven bone absorbed by osteoclasts and osteoblasts which lay down lamellar bone (with haversian blood systems)
6. Remodelling
   • Normal shape of bone is remodelled over many months and marrow cavity reforms

Abnormalities of fracture healing

• Non-union: when foreign material interposed
• Delayed-union: (1) sepsis (2) movement (3) FB (4) ischaemia (5) poor nutrition
• Malunion
• Fibrous union: occurs when there is excessive movement. Cells can differentiate into synovial cells and results in a pseudoarthrosis