Biology 2121 Independent Notes Bone Repair and Fractures

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Biology 2121 Independent Notes

Bone Repair and Fractures

I. Fractures

Most people have experienced bone fractures. Slips, falls, etc. are often the causes of bone fractures. Some people may be at higher risks for fractures than others. Recent research shows that people are at more risk for fractures if:
1. Have low bone density and frail bones.

2. Increased blood levels of the amino acid homocysteine

3. Excessive levels or intake of the fat soluble vitamin A
Fractures are classified based on the following criteria:
1. Position of the bone ends after fracture

  • Displaced fractures means that the end of the bone are out of normal alignment

2. The completeness of the break

  • Complete or incomplete

3. Position of the break compared to the axis of the bone

  • Linear (parallel to the axis of the bone) or transverse (perpendicular to the axis of the bone)

4. If the bone penetrates or breaks the skin.

  • Simple or compound (bone pushes through the skin)

5. Location of the fracture.

Common Fractures (table 6.2)
1. Greenstick

  • Common in children

  • Only one side of the shaft of the bone breaks

  • Bends and breaks due to child’s flexible bones

2. Compression

  • Bone is crushed

  • People who have soft bones or osteoporotic bones are susceptible

3. Spiral

  • Opposing forces twist the bone and break it.

4. Epiphyseal

  • Break occurs at the junction between the epiphysis and diaphysis

5. Depressed


  • Bone shatters into 3 or more pieces

  • Brittle bones of the old

II. Repair – Simple Fracture
The repair process of a simple fracture takes place following the steps:
1. Hematoma

  • Blood vessels burst or hemorrhage.

  • Blood clots in the local area called a “fracture hematoma”

  • Bone cells die – swelling and inflammation occurs

2. Fibrocartilage Callus Formation

  • Fibroblast and osteoblast cells enter from the periosteum and endosteum

  • Fibroblasts produce collagen fibers that mend the break

  • Osteoblasts produce spongy bone

3. Bone Callus

  • Spongy trabeculae appears in the fibrocartilage callus

  • Converted to the bony callus

4. Remodeling

  • Bony callus is remodeled

  • Compact bone is laid down to reconstruct the shaft walls

If there is a compound or major fracture that cannot heal on its own or must be set by other than traditional means:

  • Screws, plates, pins, etc. may be used for extensive breaks

  • Often times bone grafting may be used:

    • A bone graft is surgery to place new bone into spaces around a broken bone or bone defects.

    • The new bone can be taken from the patient's own healthy bone (this is called an autograft) or from frozen, donated bone (allograft).

    • A surgeon makes a cut over the bone defect. The bone graft is shaped and inserted into and around the area. The new bone is held in place with pins, plates, or screws. Stitches are used to close the wound. A splint or cast is usually used to prevent injury or movement while healing.

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