6. Fracture and Repair of Bone

6. Fracture and Repair of Bone

• A fracture is any break in a bone. 

Fractures are named according to their 

• severity, 
• the shape or position of the fracture line, or
• even the physician who first described them. 

Among the common types of fractures are the following 

1. Open (compound) fracture: 

• The broken ends of the bone protrude through the skin 

 2. Closed (simple) fracture 

•  does not break the skin. 

3. Comminuted fracture (com- together; -minuted crumbled): 

• The bone is splintered, crushed, or broken into pieces, and 
• smaller bone fragments lie between the two main fragments. 
• This is the most difficult fracture to treat.

4. Greenstick fracture: 

• A partial fracture in which one side of the bone is broken and the other side bends; 
• occurs only in children, 
• whose bones are not yet fully ossified and contain more organic material than inorganic material 

5. Impacted fracture: 

• One end of the fractured bone is forcefully driven into the interior of the other 

6. Pott’s fracture: 

• A fracture of the distal end of the lateral leg bone (fibula), with serious injury of the distal tibial articulation

7. Colles’ fracture 

• A fracture of the distal end of the lateral forearm bone (radius) in which the distal fragment is displaced posteriorly 

• In some cases, a bone may fracture without visibly breaking.

A stress fracture 

• is a series of microscopic fissures in bone that forms without any evidence of injury to other tissues.
•  In healthy adults, stress fractures result from repeated, strenuous activities such as running, jumping, or aerobic dancing. 
• Stress fractures are quite painful 
• and also result from disease processes that disrupt normal bone calcification, such as osteoporosis . 
• About 25% of stress fractures involve the tibia.

• Although standard x-ray images often fail to reveal the presence of stress fractures, they show up clearly in a bone scan.

• The repair of a bone fracture involves the following steps

1. Formation of fracture hematoma. 

• Blood vessels crossing the fracture line are broken. 
• As blood leaks from the torn ends of the vessels, a mass of blood (usually clotted) forms around the site of the fracture. 
• This mass of blood, called a fracture hematoma  hemat- blood; -oma tumor), 
• usually forms 6 to 8 hours after the injury.

• Because the circulation of blood stops at the site where the fracture hematoma forms, nearby bone cells die. 
• Swelling and inflammation occur in response to dead bone cells, producing additional cellular debris. 
• Phagocytes (neutrophils and macrophages) and osteoclasts begin to remove the dead or damaged tissue in and around the fracture hematoma.
• This stage may last up to several weeks.

2.  Fibrocartilaginous callus formation. 

• Fibroblasts from the periosteum invade the fracture site and produce collagen fibers. 
• In addition, cells from the periosteum develop into chondroblasts 
• and begin to produce fibrocartilage in this region. 
• These events lead to the development of a fibrocartilaginous callus  a mass of repair tissue consisting of collagen fibers and cartilage that bridges the broken ends of the bone. 
• Formation of the fibrocartilaginous callus takes about 3 weeks.

3.  Bony callus formation. 

• In areas closer to well-vascularized healthy bone tissue, osteogenic cells develop into osteoblasts, which begin to produce spongy bone trabeculae.
• The trabeculae join living and dead portions of the original bone fragments. 
• In time, the fibrocartilage is converted to spongy bone, and the callus is then referred to as a bony callus. 
• The bony callus lasts about 3 to 4 months.

4.  Bone remodeling. 

• The final phase of fracture repair is bone remodeling of the callus. 
• Dead portions of the original fragments of broken bone are gradually resorbed by osteoclasts.

• Compact bone replaces spongy bone around the periphery of the fracture.
•  Sometimes, the repair process is so thorough that the fracture line is undetectable, even in a radiograph (x-ray). 
• However, a thickened area on the surface of the bone remains as evidence of a healed fracture.

• Although bone has a generous blood supply, healing sometimes takes months. 
• The calcium and phosphorus needed to strengthen and harden new bone are deposited only gradually, 
• and bone cells generally grow and reproduce slowly. 
• The temporary disruption in their blood supply also helps explain the slowness of healing of severely fractured bones.

CLINICAL CONNECTION 



Treatments for Fractures

• Treatments for fractures vary according to age, type of fracture, and the bone involved. 

The ultimate goals of fracture treatment are 

• realignment of the bone fragments, 
• immobilization to maintain realignment, and
• restoration of function. 

• For bones to unite properly, the fractured ends  must be brought into alignment, a process called reduction, 
• commonly referred to as setting a fracture. 

1. In closed reduction, the fractured ends of a bone are brought into alignment by manual manipulation, and the skin remains intact.
2.  In open reduction, the fractured ends of a bone are brought into alignment by a surgical procedure in which internal fixation devices such as screws, plates, pins, rods, and wires are used.

• Following reduction, a fractured bone may be kept immobilized by a cast, sling, splint, elastic bandage, external fixation device, or a combination of these devices.