Chapter 48 Bone Grafts and Substitutions

Question 1

Name 4 different types of bone grafts

Answer 1

Osteogenesis
Osteoinduction
Osteoconduction
Osteopromotion

Question 2

Describe osteogenesis and give examples

Answer 2

Supplies and supports bone-forming cells

Autogenous cancellous bone graft
Bone marrow

Question 3

Describe osteoinduction and give examples

Answer 3

Induces bone formation when placed into a site where no bone formation will otherwise occur

Demineralized bone matrix (allogenic bone)
BMPs

Question 4

Describe osteoconduction and give examples

Answer 4

provides scaffold for mesenchymal stem cells and their progeny to migrate into and proliferate with.

Naturally occurring: trabecular matrix of cancellous bone (allograft)
Synthetic: Bioactive glasses
Collagen, porous bioceramics, polymers, composites

Question 5

Describe osteopromotion and give examples

Answer 5

Enhances regeneration of bone without cells or scaffold. Provides different stimulatory signals to bone-regenerating tissues. osteopromotive stimuli alone cannot induce bone formation. Osteopromotion can be achieved by introduction of substances or materials that enhance bone regeneration or by physical or mechanical strategies that induce proliferation and differentiation of mesenchymal stem cells and their progeny.

Examples: PRP*, hydrogels, and biphasic calcium phosphate (also osteoconductive)

Question 6

What properties does autogenous cancellous bone graft have

Answer 6

all of them: Osteogenetic, osteoinductive, osteoconductive, and osteopromotive

Question 7

Sites for autogenous cancellous bone graft

Answer 7

Iliac crest, proximal humerus, and medial tibia – most common. Ribs and proximal femur less commonly

Question 8

Describe reharvesting and healing times for bone graft sites

Answer 8

Healing varies. Second collection can be obtained from humeral or femoral site 12 weeks after.

Heals more completely in the proximal humerus than the proximal tibia*

Humerus can be reharvested in 8 weeks*

Tibia can be reharvested in 12 weeks*

Question 9

Describe healing of bone graft sites

Answer 9

Healing varies. Defects in proximal tibia heal slower than those located in the humerus and fill more with fibrous tissue
Heals more completely in the proximal humerus than the proximal tibia*

Question 10

What factors are released from platelet alpha granules in PRP and what properties does it have

Answer 10

Contain hundreds of growth factors, cytokines, vasoactive peptides, and extracellular matrix proteins

Osteopromotive

Question 11

What are platelet alpha granules role in bone healing

Answer 11

Hemorrhage and the resulting clot have activated platelets. Platelets are degranulated and platelet alpha granules release growth factors necessary for all wound healing especially bone healing. Alpha granules release IGF-1, PDGF, and TGF-B which are osteopromotive (promotes de novo formation of bone).