Bone graft- Dayton

Question 1

what does a bone need to heal?

Answer 1

1. vascular system ( periosteal/edosteal and surrounding soft tissue.
2. cellular activity ( osteocytes and growth factors.. primary bone =cutting cone and secondary bone = bone callus)
3. mechanical stability
4. healthy patient immune system ( hgA1c, Ca, PTH, Vit D3, etc)

Question 2

tell me more about mechanical stabilization

Answer 2

directly affects cellular activity
inappropriate motion interferes with healing
absolute rigidity may slow healing
controlled micro-motion can stimulate healing.
has biologic significance

Question 3

what is the most important factor for healing?

Answer 3

vascularity!!! we need nutrients in order to properly heal - no matter the problem.

Question 4

what is the function of a bone graft?

Answer 4

1. structural support ( prevent collapse/subsidence [one into the other]
2. void filler ( tumor excision, lengthening, revision)
3. improved healing ( add biologic components to healing site[upregulates healing], many bone grafts are just scaffolds)

Question 5

what is the biology of a bone graft?

Answer 5

osteoconduction
osteoinduction
osteogenesis
osteostimulation

Question 6

what is osteoconduction?

Answer 6

provides the matrix or scaffold for bone growth

Question 7

what is osteoinduction?

Answer 7

• protein growth factors recruit and encourage mesenchymal cells to differentiate into osteoblastic lineages.
• complicated multistep process involving many known and unknown factors
• we must recognize the body does this without graft materials
• offers new healing

Question 8

what is osteogenesis?

Answer 8

transplanted osteoblasts and periosteal cells directly produce bone.

Question 9

what is osteostimulation?

Answer 9

up regulation of local cells. ( this can be done electrically and or chemically)
signalling for new bone to be made
this encompasses the entirety of the process.

Question 10

what are the types of bone grafts?

Answer 10

autograft
allograft
xenograft

Question 11

what are the types of allografts?

Answer 11

cortical: hard layer of outer most bone
cancellous: soft inner bone
BMA = bone marrow

Question 12

Tell me about allograft bone grafts?

Answer 12

these come from cadavers, or from the bone you have elsewhere.
-within cadavers it is cleaned and dry freezed

Question 13

tell me about xenografts?

Answer 13

these come from other species. like coral!

not as popular or effective. Material does not adhere well.

Question 14

what are bone graft substitutes?

Answer 14

1. genetically engineered growth factors ( signals for bone healing/formation and then recombine manufacturing which can then be added to the site.
2. allograft= DBM?
3. synthetic = BTCP?

Question 15

what are autogenous bone grafts?

Answer 15

BONE FROM YOU!
“gold standard”- other material judged next to this one
however no definitive research to prove healing characteristics ( osteoconduction, osteoinduction, or osteogenesis)
- draw backs = limited supply and donor site morbidity… you can only take so much from the iliac crest. sometimes taking bone from the hip is more invasive and problematic then the actual bone repair needing to take place.

Question 16

what are some autogenous donor sites?

Answer 16

1. iliac crest
2. proximal tibia
3. distal tibia
4. segmental fibula
5. calcaneus ( photo shows cube taken out)
6. local bone at surgical site

Question 17

tell me about autologous marrow grafts?

Answer 17

• no growth factor, BMP, chemical or mechanical means can contribute directly to bone healing except through cellular stimulation
• stem cells, mature bone cells, platelets and other hemotopoetic cells are present in bone marrow.
• increasing local cellular activity improves healing
• low cost, easily available, low morbidity.

Question 18

what is the destiny of bone marrow stem cells?

Answer 18

1. mesenchymal stem cells ( differentiate into = osteocytes, muscle, fibrous, adipose)
2. hematopoetic stem cells ( differentiate into = blood cells)

*** we use stem cells in hopes that they become what we need.

Question 19

how is the blood marrow obtained?

Answer 19

11 gauge cannula. access in distal aspect of lower leg… tibia

Question 20

tell me about composite grafts? why not combine grafts to take advantage of individual properties?

Answer 20

• B- tricalcium phosphate ( osteoconductive, porous, high protein and cellular affinity)
• autogenous bone marrow ( osteoinductive and osteogenic)

Question 21

What are the details about beta tri-calcium phosphate?

Answer 21

• synthetic bone graft substitute widely available
• osteoconductive
• heals bone by direct formation, not creeping substitution.

Question 22

why is beta tri-calcium phosphate widely acceptable?

Answer 22

( wet compressive strength slightly less than cancellus bone… it is non structural, but there is no disease transmission)

Question 23

why is beta tri-calcium phosphate osteoconductive?

Answer 23

pore size = 100-400 um
interconnected pores ( resembles bone in the ways bone marrow can move through)
excellent pore affinity and attachment
excellent reabsportion and in-growth characteristics

Question 24

tell me about the evidence based medicine studies done on dogs…

Answer 24

positive bone healing results with use of bone marrow and beta tri-calcium phosphate.

Question 25

significance of beta tri calcium phosphate and defects caused by fibulectomy?

Answer 25

12/14 patients were able to develop new bone and were able to regenerate the fibula. ( yet again we see the bone marrow and BTCP save the day)

Question 26

how does a BMA inection work for a non union?

Answer 26

we are able to trick the body by introducing new biology the body will get sigals to heal. otherwise it might not have done so.

Question 27

what are the concerns for patients who have had multiple revisions?

Answer 27

soft tissue blood supply
overall patient health
length
stability 
bone health
( some of the new designs for implants have failed)

Question 28

what are some variations of bone allograft forms?

Answer 28

fresh- highly antigenic, limited use

fresh frozen- less antigenic

freeze dried- most common, least antigenic, 5 yr shelf life
( slides show how it was made more porous and can replace metal fixation piece giving patient better results)

• ** these are osteoconductive, FDA approved,
• ** drawbacks= 1. must undergo creeping substitution for incorporation, as well as 2. bone formation proceeds from edges to inside.