Bone Regrowth

Question 1

What are the differences between cortical and cancellous bone?

Answer 1

Cortical-
Diaphysis
Resists
Bending
Torsion
Laid down circumferentially
Less biologically active
Cancellous-
Metaphysis
Resists/absorbs
compression
Site of  longitudinal growth (physis)
Very biologically active`

Question 2

What does the first stage of bone repair involve?

Answer 2

Inflammation
Haematoma in the actual fractures drives the inflammatory process. Then the muscles contract to try and stabilise the break (causes pain). Hypoxia leads to macrophage release. Therefore open fractures might heal slower due to loss of haematomas.
Can give platelet concentrates to speed up treatment.

Question 3

What does the second stage of bone repair involve?

Answer 3

A soft callus forms when the swelling and pain has subsided. Stops the bone from shortening.

Question 4

What does the third stage of bone repair involve?

Answer 4

Hard callus which is the conversion of cartilage to woven bone

Question 5

What does the fourth stage of bone repair involve?

Answer 5

Conversion of woven bone to lamellar bone

Medullary canal is reconstituted

Question 6

What is creeping substitution?

Answer 6

When the patient’s own bone slowly grows over an implanted bone repair

Question 7

What are some causes of a delayed union (failure to heal in expected time) in a fracture?

Answer 7

High energy injury
Distraction (increased osteogenic jumping!)
Instability
Infection
Steroids
Immune suppressants
Smoking
Warfarin
NSAID
Ciprofloxacin