Physiology of Bone Healing

Following a fracture the broken ends of the bone the healing starts and procedes in several stages :

A haematoma is formed between the broken ends of the bone and in the surrounding tissues

An acute inflammatory reaction occurs and there is an accumulation of macrophages which phagocytose the haematoma, inflammatory exudate and small fragments of bone without blood supply ( 5 days )

Granulation is formed around the broken ends with new blood vessels

Osteoblasts develop in large numbers in the haematoma around the bone. They secrete non-lamellar osteoid. The non-lamellar osteoid is quickly organised into lamellar osteoid. It is then calcified and turns

into callus ( 3 weeks )

Osteoclasts are formed in the callus which shape the new bone removing excess callus and open up a medullary canal in the callus ( in weeks or months )