Bone grafts

Question 1

What are the four classification strategies of bone grafting, with examples?

Answer 1

Osteogenesis: Autogenous cancellous bone graft (also has osteoinductive, osteoconductive and osteopromotive properties).
Osteoinduction: demineralized bone matrix.
Osteoconduction: anything that provides a scaffold for bone formation, can be absorbable/nonabsorbable, natural/synthetic, may or may not have load bearing properties.
Osteopromotion: PRP, hydrogels, biphasic calcium phosphate

Question 2

What is the proportion of cells that survive with autogenous cancellous bone grafting?

Answer 2

60% (up to 3 hours after harvesting)

Question 3

When does maximum osteogenesis occur after autogenous cancellous bone grafting?

Answer 3

8 weeks

Question 4

What are the most common sites for autogenous cancellous bone graft collection?

Answer 4

Proximal humerus, wing of the ilium, proximomedial tibia, femoral condyles, subtrochanteric region of the femur

Question 5

How quickly does restoration occur after autogenous cancellous bone graft collection from the proximal humerus and the proximal tibia?

Answer 5

Humerus: 8-weeks
Tibia: 12-weeks

Question 6

What is the ideal size of autogenous cancellous bone graft material?

Answer 6

3-6mm

Question 7

How do autogenous cancellous bone grafts heal?

Answer 7

Proactive substitution: cyclical pattern of vascular invasion, subsequent bone formation and resorption

Question 8

How do cortical allografts heal?

Answer 8

Creeping substitution: after vascular penetration the bone is slowly resorbed by osteoclastic and immunologic activity and replaced with host bone. Can take months to years.

Question 9

What is demineralized bone matrix?

Answer 9

Bone that has been ground to specific particle sizes and has been decalcified with use of acids.

Question 10

What is the calcium content of demineralized bone matrix?

Answer 10

<3% (22-25% in normal bone)

Question 11

What classification of bone graft does demineralized bone matrix fall under?

Answer 11

Osteoinductive. If combined with allogenic cancellous bone chips can have osteoconductive component. Mix with blood/bone marrow at the surgical site to provide cells for osteogenesis.

Question 12

What effect do BMP-2 and 7 have on bone healing?

Answer 12

Stimulate differentiation of osteoprogenitor cells into osteoblasts.

Question 13

What are some examples of synthetic bone graft substitutes?

Answer 13

Ceramics, calcium phosphate ceramics, tricalcium phosphate, biphasic calcium phosphate, calcium sulfate, coralline bone graft substitutes, hydrogels

Question 14

What is the ideal pore size of a ceramic to allow osteoprogenitor cell infiltration?

Answer 14

300-500 um