7.5 Bone Fractures

A fracture is a medical term for a broken bone, occurring when the physical force exerted on the bone is stronger than the bone's structural integrity.

Common Types of Fractures

• Simple (Closed) Fracture: The bone is broken, but the overlying skin remains intact.
• Compound (Open) Fracture: The broken bone ends penetrate the skin, creating an open wound. This carries a higher risk of infection.
• Complicated Fracture: A fracture that causes damage to adjacent organs or tissues.

Bone Repair

Bone is a living tissue capable of self-repair. The healing of a simple fracture occurs in four main stages:

1. Haematoma (Clot) Formation

• Immediately after the fracture, blood vessels within the bone and surrounding tissues are torn, leading to haemorrhage (bleeding).
• A haematoma (a mass of clotted blood) forms at the fracture site.
• Bone cells deprived of their nutrient supply die.
• The area becomes swollen, painful, and inflamed.

2. Fibrocartilaginous (Soft) Callus Formation

• Occurs within a few days.
• New capillaries grow into the haematoma.
• Phagocytic cells (like macrophages) invade the area to clean up cellular debris.
• The ruptured periosteum stimulates osteoblasts (bone-building cells) and cartilage-forming cells.
• These cells secrete a porous mass of bone and cartilage called a callus (or soft callus), which replaces the blood clot and splints the broken ends together.
• This stage takes approximately three to four weeks.

3. Bony Callus Formation (Callus Ossification)

• Beginning about a week after soft callus formation, it is gradually converted into a bony callus of spongy bone.
• Osteoclasts (bone-resorbing cells) break down the cartilage.
• Osteoblasts replace the cartilage with bone.
• A firm union of the bone ends is typically formed after about two months.

4. Bone Remodelling

• This is the final phase, where the bony callus is remodelled.
• Compact bone is formed across the fracture line to connect both sides.
• Osteoclasts remove the excess bone material produced during healing.
• The final structure of the repaired area resembles the original unbroken bone, as it adapts and responds to mechanical stressors.

Science, Technology and Society Connections

• Improper Posture and Bone/Joint Health: Maintaining improper posture increases stress on joints and their supporting structures. This can lead to injury, chronic pain, and premature degeneration of bones and joints.