Fracture Healing and Remodeling

Question 1

What are 3 theories that govern bone remodeling?

Answer 1

1) Wolff’s Law: bone remodels in response to mechanical stress
2) Piezoelectric Charges: bone remodels in response to electric charges; compression side is electronegative and stimulates osteoblast formation
tension side is electropostive and stimulates osteoclasts
3) Hueter-Volkman: Bone remodels; tension promotes longitudinal growth while compression inhibits growth

Question 2

What are the stages of bone healing?

Answer 2

1) Inflammation
2) Repair
3) Remodeling

Question 3

Type X collagen expression by hypertrophic chondrocytes is characteristic of which of the following aspects of fracture healing?

Answer 3

Cartilage callous formation and calcification

Question 4

What are internal variables important for bone healing?

Answer 4

1) Blood flow (most important)
2) head injury
3) mechanical factors

Question 5

What are external variables are important for bone healing?

Answer 5

1) Low Intensity Pulsed Ultrasound: creates nanomotion at fracture site
2) radiation: decreases healing
3) COX-2: causes mesenchymal cells to differentiate into osteoblasts
4) Bone stimulators: can decrease osteoclast activity and increase osteoblast activity

Question 6

What are patient factors are important for bone healing?

Answer 6

1) Nicotine: increased healing time and incidence of nonunion
2) DM: can take 1.5x as long to heal fractures
3) Diet: protein, Vit D and calcium deficiencies increase healing time
4)

Question 7

Which medications can affect fracture healing?

Answer 7

1) Bisphosphonates: prolonged healing time
2) NSAIDS: prolonged healing time
3) Coticosteroids: 6.5% higher rate of nonunion
4) Quinolones: toxic to chondrocytes

Question 8

What type of fracture healing occurs in a femoral shaft fracture treated with an intramedullary nail?

Answer 8

Secondary fracture healing