Fracture Healing

Fracture healing Dr. Mehzabin Ahmed

Fractures • The break in the continuity of bone is known as a bone fracture • Caused by physical trauma • The degree of fracture can vary widely from a simple crack to fragmentation

Types of fractures 1- Simple fracture- when the bone is broken in one place but the skin is not broken 2- Compound fracture- when the skin is torn by the broken bone 3- Greenstick fracture- when the break is only one side of the bone and the bone bends 4- Comminuted fracture-when there are at least three bone fragments 5- Pathological fracture- trivial trauma causes fractures in a bone that is already diseased/ abnormal

1- Simple fracture

2- Compound fracture

4- Comminuted fracture

3- Greenstick fracture

5- Monteggia fracture

Pathological fractures • Metabolic bone disease like Paget’s disease, Osteoporosis, Osteomalacia • Primary tumors of the bone & bone marrow like Giant cell tumor, Myeloma • Metastasis to the bone from tumors of the breast, bronchus, thyroid & kidney • Congenital bone disorders- Osteogenesis Imperfecta

Healing of fractures • Fractures heal by granulation tissue formation and fibrous repair • This is followed by new bone formation in the fibrous granulation tissue

Factors that influence fracture healing 1) 2) 3) 4) 5)

Proper immobilization Adequate blood supply General nutritional status Presence of infection Presence of foreign bodies or large amount of necrotic bone 6) Administration of corticosteroids

Stages of fracture healing

Stage of hematoma formation- 2-3 weeks Due to the tearing of the blood vessels in the medullary cavity, cortex and periosteum and the periosteum is stripped off from the bone surface.

Stage of soft callus formation- 3 to 8wks after injury Organization of the hematoma with Migration of neutrophils & macrophages to phagocytose the hematoma & necrotic debris. This is followed by the ingrowth of capillaries & fibroblast from the surrounding tissues. New osteoblasts develop

Stage of hard callus formation- 8 to 12 wks after injury Osteoblasts derived from the osteoprogenitor cells migrate into the granulation tissue and deposit osteoid in a haphazard way thus producing woven bone. Thus the ends get closely apposed and direct ossification occurs

Woven bone

Lamellar bone

Stage of remodeling- after 12 wks of injury Initial bone that is formed is woven bone & this is mechanically weak. Remodeling by osteoclastic erosion and organized osteoid synthesis removes excess of the hard callus at the fracture site resulting in the formation of organized lamellar bone

End result of fracture healing

With time new lamellar trabecular bone is laid Minor marrow space fibrosis and cortical irregularity persists at the fracture site

Complications • • • • • • • •

Delayed union- slow healing of the fracture Non union- the bone fails to unite Mal union- the fracture heal but with malalignment Compartment syndrome- bleeding into tight fascial compartments thus compressing the blood vessels and nerves Neurovascular injury- due to direct injury by the fractured bone Infection- common with the compound fractures Post-traumatic arthritis- causes osteoarthritis Growth abnormalities- seen in children with fractures affecting the epiphysial plate

Resources Pathology: Alan Stevens, James Lowe Second edition, Harcourt Publishers, Chapter 24