49.Bone grafts

Question 1

source of mesenchymal stem cells for bone differentiations

Answer 1

–cambium layer of periosteum–bone marrow– fat(cell # decrease with age)

Question 2

growth factors act on target cells in what 3 fashions

Answer 2

1. autocrine–same or similar phenotypic cells2. paracrine–different cell phenotype/adjacent cells3. endocrine–different and remote population of cellsusually cell surface receptor mediated and results in the change of one or more gene of the target cell

Question 3

types of growth factors used to stimulate bone (5)

Answer 3

1. TGF beta–nonspecfic2. Bone morphogenic proteins (BMP 2–0.15 mg and carrier absorbable collagen sponge, CaP)3. Fibroblast growth factor–angiogenesis and fibroblast prolif (early stages)4. Insulin like growth factor–bone lengthening & cell prolif5. platelet derived growth factor–initial fracture healing (released from alpha granules of platelets)

Question 4

four strategies of bone grafts

Answer 4

1. osteogenesis–autogenous cancellous bone graft, bone marrow2. osteoinduction–DBM, BMP, autogenous cancellous bone graft, allogenic bone grafts3. osteoconduction–autogenous cancellous bone graft, cortical bone graft, allogenic bone grafts4. osteopromotion–PRP, autogenous cancellous bone graft

Question 5

Osteogenesis for bone grafts

Answer 5

supplies and supports bone forming cells;providing fully differentiated and undifferentiated cellsautogenous cancellous bone graftorbone marrow

Question 6

T/FBone marrow is an osteogenic bone graft. It lacks scaffolding or osteoconductive material to be efficacious on its own

Answer 6

TRUE

Question 7

osteoINduction property of bone grafts

Answer 7

materials with the capacity to INDUCE formation when placed in a site where bone formation would not normally occurrecruit and stimulate cells demineralized bone matrixTGF betaInsulin like growth factorBMP 2, 4, 7

Question 8

osteoCONductive property of bone grafts

Answer 8

provides a scaffold; physical material to build fromautogenous cancellous bone graft allogenic bone graftautogenous cortical bone graft

Question 9

osteopromotion property of bone grafts

Answer 9

enhances the regenerating bonedifferent from osteogenic and osteoconduction in that bone formation is enhanced WITHOUT cells or a scaffold but osteopromotion itself cannot stimulate bone formationPlatelet rich plasma

Question 10

gold standard bone graft

Answer 10

AUTOGENOUS CANCELLOUS BONE GRAFTosteogenic (has all cells of several lineages)osteoinduction (contains cytokines and growth factors in normal local environment)osteoconductive (provides scaffold)osteopromotion (provides platelets and derived factors to enhance formation)

Question 11

areas to obtain autogenous cancellous bone graft

Answer 11

iliumhumeral greater tuberclemedial tibiasubtrochanteric fossa-femurfemoral condylesmandiblerib

Question 12

when can you repeat an autogenous cancellous bone graft in the humerus vs the proximomedial tibia

Answer 12

humerus 8 weekstibia 12 weeksrestoration occurs more completely in the prix humerus than the tibia

Question 13

what is the optimal size or a cancellous particle for bone graft

Answer 13

3-6 mmcurette size #000-#2

Question 14

what kind of bone graft properties does allogenic bone graft have

Answer 14

osteoconductiveosteoinductiveLACKS viable cells but growth factors are dispersed amongst the collagen matrix underlying the mineral content

Question 15

T/F allogenic bone grafts (whether cancellous or cortical) lack viable osteogenic cells

Answer 15

TRUEallogenic bone grafts lack viable cellsbut they still have osteoinductive and osteoconductive properties

Question 16

pros/cons to allogenic bone grafts

Answer 16

pros–no donor site morbidity, no shortage of supplycons–small risk dz transmission, histocompatibility issues (mostly ameliorated due to processing)

Question 17

T/Ftissue matching for allogenic bone grafts is necessary

Answer 17

FALSEtissue matching for allogenic bone grafts is NOT necessary

Question 18

healing of cortical allografts

Answer 18

heal slower w a greater inflammatory response caused by residual antigenic materialhaversian system of graft is Not incorporated into bone but rather it is resorbed over time (months–years)

Question 19

demineralized bone matrix

Answer 19

decalcified (w acid) bone ground to small sizes22-25%calcium down to <3% after decalcificationremoving calcium allows native or exposed growth factors to be available for healingosteoinductive can be mixed w autogenous cancellous graft for more properties

Question 20

TPLO study with DBM into osteotomy

Answer 20

DBM dogs went to activity 2 weeks earlier

Question 21

3 basic strategies associated with the use os stem cells in bone regeneration

Answer 21

1. culture expanded autologous2. culture expanded allogeneic3. selective mesenchymal stem cell retention strategies

Question 22

in a dog model using a femoral defect what were the healing rates with allomatrix vs allomatrix + bone matrix and selective retention stem cell techniques

Answer 22

allomatrix==33%allomatrix + bone marrow ==50%selective retentions stem cell techniques == 100%

Question 23

synthetic materials for bone graft substitutes

Answer 23

1. ceramics2. calcium phosphate ceramics (Hydroxyapaptite)3. coralline 4.Tricalcium phosphate5. biphasic calcium6. nanocrystalline calcium phosphate7. calcium sulfate when used alone are osteoconductive