Phases of Fracture Healing

Question 1

What are the 4 phases of fracture healing?

Answer 1

1. Haematoma + Inflammation.
2. Soft callous formation.
3. Hard callous formation.
4. Remodelling + consolidation.

Question 2

Outline the details of the haematoma + inflammation phase of fracture healing.

Answer 2

• The bone will bleed.
• Spindle-shaped haematoma forms.
• Fibrin forms a meshwork to clot blood + seal the fracture site.
• Inflammatory cells digest and reabsorb dead bone + other debris - causing an increase in calcium.
• Cytokines are released causing proliferation, which attracts osteoprogenitor cells.
• Angiogenesis will occur.

Question 3

In what time period does haematoma + inflammation take place?

Answer 3

0-3 days.

Question 4

Outline the details of the soft callus phase of fracture healing.

Answer 4

• A granulation tissue equivalent appears.
• Osteoprogenitor cells differentiate into chondroblasts, osteoblasts + fibroblasts.
• Invasion of capillaries from the endosteum + periosteum.
• Ongoing destruction of haematoma + debris.
• Laying down of collagen, possible cartilage + early organic bone substance.
• Not yet true bone, more of a collagenous tissue.
• Not strong enough for weight bearing.

Question 5

In what time period does the soft callus phase of fracture healing occur?

Answer 5

2-3 weeks.

Question 6

What is the function of fibroblasts?

Answer 6

Make collagen.

Question 7

What is the function of osteoblasts?

Answer 7

Make bone-forming cells.

Question 8

What is the function of chondroblasts?

Answer 8

Make early cartilage.

Question 9

Outline the details of the hard callus (stage 1) phase of fracture healing.

Answer 9

• Osteoblasts now dominate + start to secrete calcium + phosphate.
• Early bone is formed.
• Grows from fracture edges across fracture gap.
• A bony collar is formed due to the overcompensation of healing.
• This protects the fractured site.

Question 10

In what time period does the hard callus (stage 1) phase of fracture healing occur?

Answer 10

End of week 4.

Question 11

Outline the details of the Hard callus (stage 2) phase of fracture healing.

Answer 11

• The site has basic protection.
• Osteoblasts + osteoclasts remove + re-lay extra bone.
• Still thickened but begins to resemble the normal bony look.

Question 12

In what time period does the Hard callus (stage 2) phase of fracture healing occur?

Answer 12

1-3 months.

Question 13

Outline the details of the remodelling + consolidation phase of fracture healing.

Answer 13

• Vital to have the bone exposed to forces during the stage.
• Osteoclasts stimulate the removal of inefficient + excess bony areas.
• Osteoblasts begin to correctly lay down aligned and stronger bone.

Question 14

In what time period does the remodelling + consolidation phase of fracture healing occur?

Answer 14

3-12 months.