10: Fractures

Question 1

Which factors influence peak bone mass?

Answer 1

• EXERCISE –> Wolffs Law
• Diet (Calcium) + Vit D
• genetic predisposition
  
  • • expecially later in life (not peak bone mass: homrones (e.g. menopause))

Question 2

What are the two ways a bone can heal?

Answer 2

1. Surgical healing
2. Healing by Callus

Question 3

Explain Surgical Healing in bone

Answer 3

1. 2 broken parts are put back together in direct contact
   
   • compression of bones against each other
   • can directly join again with formation of new bone

Question 4

What are the 4 Phases of fracture healing by Callus?

Answer 4

1. 1 Week
   
   • Haematoma
2. 1-4 Weeks
   
   • Soft Callus formaition
3. 4-16 Weeks
   
   • replaced by Hard Callus (woven bone)
4. 17 and beyond
   
   • Remodelling

Question 5

What happens in the first Week after a fracture (with Callus healing)?

Answer 5

Haematoma of the bone

• Also together with infiltration of immune cells
  
  • Macrophages, Leukocytes, IL-16
    
    • sent out healing signals
• Granulation tissue forms (i.e. new tissue in wound healing)
• progenitor cells invade

Question 6

What happens in Weeks 1-4 of fracture healing by Callus

Answer 6

Formation of a soft callus

• Production of Cartilage by Chrondroblast (Type II collagen) and Fibroblast
• Proteoglycans produced that prevent bone mineralisation
• Chrondrocytes release calcium into ECM and destroy proteoglycans (vie enzyme degradation) –> allows mineralisation

Question 7

What happens in Week 4-16 of fracture healing by Callus

Answer 7

Formation of Hard Callus

• soft callus is transformed into hard Callus by
  
  • invaded with blood vessels
  • chondroclasts brek down calcified callus
  • replaced by ostioid (Type I collagen) from ostoblasts
  • Osteoid Calcifies –> Woven bone

Question 8

What happens after 16 Weeks of fracture healing by Callus?

Answer 8

Bone Remoddeling

• woven to lamellar bone
• shape changes relative to stress –> wolffs law (allows thick cortex formation + loss in medulla)
  *

Question 9

What type of fracture is this?

Which forces produce this type of fracture?

Answer 9

It is a Sprial fracture

• due to twisting of bone

Question 10

What type of fracture is this?

Answer 10

It is a oblique fracture

• compression of bone

Question 11

What type of # is this?

Which forced do you need for it?

Answer 11

Production of a Butterfly fragment

• direct hit on bone

Question 12

What kind of # is this?

Which forces are needed for it?

Answer 12

Transverse

• pulling force needed

Question 13

What is a green stick #?

Answer 13

in young bones:

• thick, flexible periosteum can keep bone stat is fractured on one side together (bone bends and breaks)