Anatomy Chap 7 & 8: Disorders of bone tissue and skeletal system

How Fractures are Classified

1. By Cause

2. By Structural Characteristics

By Cause

• Stress Fracture

• Pathological Fracture

Stress Fracture

• Caused by abnormal trauma (sudden physical force)

Examples: Falling, sports injuries

Pathological Fracture

• Caused by a disease that weakens the bone

Example: Bone cancer, osteoporosis

By Structural Characteristics

• Non displaced

• Displaced

• Greenstick

• Closed

• Fracture

• Open Fracture

Non displaced

Bone breaks but stays aligned

Displaced

Bone breaks into 2 or more pieces and the pieces shift out of alignment

Comminuted

• Bone breaks into 3 or more pieces

• Pieces are misaligned

Greenstick

Incomplete break: One side cracks, the other side bends

Closed Fracture

Bone breaks, but the skin is not pierced

Open Fracture

• Bone breaks through the skin

• High risk of deep bone infection

How Fractures Heal (8-12 weeks)

1. Hematoma Formation

2. Soft Callus Formation

3. Hard Callus Formation

4. Bone Remodeling

Hematoma Formation

• Broken blood vessels cause bleeding, forming a fracture hematoma (blood clot)

• Cells move into the area:

• Fibroblasts

• Macrophages

• Osteoclasts

• Osteogenic cells

• These convert the clot into granulation tissue (soft fibrous mass)

Soft Callus Formation

• Fibroblasts deposit collagen

• Osteogenic cells turn into chondroblasts, which make fibrocartilage

• Collagen + fibrocartilage = soft callus

Hard Callus Formation

• Osteoblasts build a hard bony collar (hard callus) around the fracture

• Acts as a temporary splint

• Must keep the bone immobilized so it doesn’t break again

Bone Remodeling

• Osteoclasts remove small bone fragments

• Osteoblasts lay down spongy bone filling gaps and preventing the bone from healing shorter

• Over time, spongy bone becomes compact bone again