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Module 13-15 Fracture repair 2 > Bone grafts > Flashcards

Bone grafts Flashcards

1
Q

What are the features of bone grafts?

A

1) Osteoinduction
2) osteconduction
3) osteogenesis
4) osteopromotion

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2
Q

What are indications of bone grafts?

A
  • enhancing fracture healing and stimulating healing of fracture gaps
  • artrodesis
  • treatment of comminuted fractures
  • used in older animals or when delayed healing is percieved
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3
Q

What is osteoinduction?

A
  • induced bone formation when placed into a site
  • recruit mesenchymal cells to form osteoblasts/clasts
  • related to presence of growth factors such as BMP, TGF, IGF

Osteoinduction is when non-osseus tissue becomes osteogenic.

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4
Q

What is osteoconduction?

A
  • scaffold material for mesenchymal stem cells and progeny to migrate into
  • three dimensional process of in-growth of capillaries, perivascular tissues, osteoprogenitor cells into structure of the graft
  • may or may not be load bearing
  • can be naturally occuring or synthetic
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5
Q

What is osteogenesis?

A
  • new bone formation from transferred osteoblasts
  • only about 10% of transferred cells survive
  • autogenous calcellous bone grafts the best
  • bone marrow is also osteogenic (lack scaffolt material to be efficacious on its own)
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6
Q

What is osteopromotion?

A
  • enhanced regeneration of bone
  • achieved by
    1) introduction of substances that enhance bone regeneration
    2) mechanical strategies that induce proliferation and differentation of stelm cells

–> e.g. Platelet rich plasma

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7
Q

Types of bone grafts?

A

1) Autografts
- cancellous
- cortico-cancellous
- cortical (vascularized, non-vascularized)
2) Allografts
- cancellous bone chips
- cortical grafts
- demineralized bone matrix
3) growth factors
- bone morphogenic protein
4) Synthetic
hydroxyapatite

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8
Q

Autograft?

A

From same animal

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9
Q

Allograft?

A

From different animal

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10
Q

Xenograft?

A

From different species

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11
Q

What type of bone grafts are considered gold standard?

A

Autogenous cancellous bone grafts

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12
Q

Where can you harvest autogenous cancellous bone grafts?

A

1) proximal lateral humerus (base of greater tubercle)
2) ilial wing (dorsal or lateral) - less risky
3) proximal lateral femur
4) distal femoral condyle
5) medial proximal tibia

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13
Q

Estimated viability of autogenous bone grafts?

A

3 hours after harvest the graft viability decrease to:
- 57% in blood soaked swabs
- 46% in saline
- 70-73% in ice and buffered solution

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14
Q

What are indications of bone grafts?

A
  • enhancing fracture healing and stimulating healing of fracture gaps
  • artrodesis
  • treatment of comminuted fractures
  • used in older animals or when delayed healing is percieved
  • filling cavities (e.g. cysts)
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15
Q

Advantages of cancellous grafts?

A
  • rapid stimulation of direct bone formation
  • early osteoinduction
  • early vascularization
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16
Q

What is the optimal size of a cancellous bone graft?

A

2-4mm
if <0,7mm will be swept away in granulomatous response
if >4mm may act as sequestrae

17
Q

Complications of cancellous bone grafts?

A

pain
infection
fracture
Blood loss
Prolongation of anaesthetic time
increased discomfort to the patient

18
Q

How to use bone grafts in delayed union?

A
  • remove sclerotic tissue
  • remove fibrous tissue
  • stabilize fragments
  • place graft around fracture site
19
Q

Allogenous cancellous bone grafts?

A
  • problematic availability
  • provokes a strong rejection response
  • osteogenesis less productive, re-vascularization very variable
  • if cells removed prior to transplant the graft can still contribute to healing through its osteoconductive and osteoinducive powers
  • particularly susceptible to infection
20
Q

Advantages of cortical bone grafts?

A
  • it has osteoconductive and osteoinductive properties
  • supportive or weight bearing function
21
Q

Indications for use of cortical bone grafts?

A
  • treatment of multifragmented diaphyseal long-bone fractures
  • limb lengthening procedures
  • management of malunion or non-union fractures
  • limb salvage procedures for primary bone tumours
  • graft in vertebral fusion - wobblers
  • arthrodesis
22
Q

Properties of cortical bone ALLOgrafts?

A
  • slow healing
  • envoke inflammatory response
  • resorption can take months or years
  • do not supply cells
  • if support is required need rigid internal fixation and compression
  • limited stock (cadaver)
  • aseptic removal, freezer (-70)
  • no osteogenesis
  • slow revascularization and incorporation

Complications: infection, implant loosening/breakage

23
Q

Limitation of cortical autograft?

A

Limited amount of bone can be taken out
donor sites:
- rib
- ulna
- iliac wing
- medial tibial cortex

24
Q

Types of cortical bone grafts?

A
  • bone chips
  • onlay bone graft
  • tubular
  • corticocancellous
  • sliding onlay
25
Q

Xenografts?

A

Lyophilized calf bone is generally used after it has been defatted and freeze dried

Used simply as a support

26
Q

Vascularized grafts?

A
  • not commonly used
  • difficult, microvascular anastomosis
  • expensive equipment
27
Q

Synthetic grafts?

A
  • ceramics, injectable calcium phosphate, bioactive glass and glass ionomer cements

Poor clinical results, unpredictable resportion rates and inflammatory reactions

28
Q

Bone morphogenic proteins?

A

rhBMP-2
- promotes differentiation of mesenchymal stem cells
- applied on absorbable sponge
- expensive

Module 13-15 Fracture repair 2 (8 decks)

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