Fracture Healing

Question 1

What happens during the first stages of fracture healing?

Answer 1

Bleeding/ Hematoma

Blood vessels are damaged leading to bleeding/hematoma/swelling at fracture site

Fibrin blood clot forming mesh between ends of bone. Inflammatory response - cytokine release and Macrophages clear dead ends of bone.

Fibroblasts lay down granulation tissue to form a ‘scaffold’ (basis of soft callus).

Question 2

Describe the progression from soft callus through to remodelling

Answer 2

Fibroblasts in granulation tissue lay down fibrocartilage/cartilage - spongy material filling gap between fragments. This is week for first 6 weeks hence casting.

New blood vessels form (neoangiogenesis). Periosteum lays down woven bone.
Avascular cartilaginous matrix —> vascularised osseus tissue

Soft callus completely transformed into woven bone. Calcification/mineralisation of cartilage/soft callus. Once hard callus formed, fracture union has occured.

Remodelling - osteoclasts/osteoblasts remove disorganised woven bone and lay down highly organised lamellar bone. Can take upto 2 years. Influenced by weight bearing.

Question 3

What can happen if bones are not allowed to undergo full healing process?

Answer 3

delayed/non-union

Question 4

Describe the difference between indirect and direct fracture healing

Answer 4

Direct - usually only after surgery (open reduction internal fixation) in stable and controlled environment where fracture fragments are in contact. Lamellar bone can be laid down immediately

Indirect - non surgical. follows 4 stages of bleed/inflam/soft/hard/remodelling.