Science of Fractures - Hoffman

Question 1

Explain intramembranous ossification and endochondral ossification:

Answer 1

Intramembranous ossification – mineralization of connective tissue

Endochondral ossification – mineralization of cartilage

Question 2

explain woven bone vs lamellar bone

Answer 2

woven

• immature
• lay down rapidly

lamellar

• mature
• lay down slowly
• stronger

Question 3

Explain 3 phases of fracture healing:

Answer 3

INFLAMMATION

• Pluripotent mesenchymal cells (fibroblasts, osteoblasts, chondocytes)
• Monocytes (osteoclasts)

REPARATIVE
-soft callus formation, fibrous tissue, cartilage, woven bone
-transition to hard callus
Clinical union – fracture site becomes stable and pain free
Radiographic union – plain radiographs show bone trabeculae or cortical bone crossing the fracture site

REMODELING
Replacement of woven bone by lamellar bone
Resorption of unneeded callus
May continue for years!

Question 4

What cells become osteoblasts, chondrocytes, fibroblasts and osteoclasts?

Answer 4

Pluripotent mesenchymal cells (fibroblasts, osteoblasts, chondocytes)

-Monocytes (osteoclasts)

Question 5

How does a soft callus look on an x-ray?

Answer 5

you actually dont see it until it hardens

Question 6

Variables that influence fracture healing:

Answer 6

Injury variables
-damage to blood supply
Patient variables
- age
Tissue variables
-location of the bone
-bone disease
Treatment variables
- apposition of fracture fragments
-fracture stabilization

Question 7

ADvantages and disadvantages of using a plate fiaxation

Answer 7

game-changer

Fracture gap closed by fixation
No formation of external callus
Lamellar bone forms directly across fracture line, this is a much slower process than using a callus intermediate

Question 8

3 zones to know

Answer 8

metaphysis (mature bone)
hypertrophic (weakest zone)
proliferative zone (where cells start, distal) - bone growth problems can occur if you injure this zone

*MATURATION occurs distal to proximal