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A U E R S & T > Chapter 78 -Bone grafts > Flashcards

Chapter 78 -Bone grafts Flashcards

1
Q

What has been the historical significance of autografts in equine fracture treatment?

A

Autografts have been the historical gold standard for equine fracture treatment to increase both bone matrix and progenitor cells at the fracture site.

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2
Q

According to the text, what are the classifications of bone grafts based on?

A

Bone grafts are classified according to preservation, source, and composition

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3
Q

What distinguishes autografts from allografts and xenografts?

A

Autografts are harvested from the same individual, allografts from a genetically different individual of the same species, and xenografts involve tissue transfer between two members of different species.

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4
Q

What are the typical applications of autogenous cancellous bone grafts in horses?

A

Autogenous cancellous bone grafts are commonly used in long bone fractures, arthrodeses, and comminuted phalangeal fractures, with harvest sites including the sternum, tuber coxae, and proximal tibia.

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4
Q

What are the three major functions of bone grafts, as established by Urist in 1965?

A

The three major functions of bone grafts, established by Urist in 1965, are osteoinduction, osteoconduction, and osteogenesis.

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5
Q

What is osteoinduction, and how does it relate to bone grafts?

A

Osteoinduction refers to the process of signaling new bone formation, stimulated by bone trauma and the addition of a bone graft.

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6
Q

How does osteoconduction contribute to the formation of new bone in bone grafts?

A

Osteoconduction contributes to the formation of new bone by providing physical support for osteoprogenitor cells on a matrix that acts as a scaffold.

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7
Q

What is osteogenesis in the context of bone grafts, and what is its relationship to cancellous bone?

A

Osteogenesis in the context of bone grafts refers to the formation of osteoid by osteoblasts and is associated with surviving cells, especially in cancellous bone.

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8
Q

Describe the standard series of events associated with bone graft incorporation, paralleling the process of fracture repair.

A

The standard series of events associated with bone graft incorporation includes the formation of a host-dependent hematoma, neovascularization, progenitor cell proliferation, and graft resorption and remodeling.

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9
Q

What factors influence the rate, contributions, and successful incorporation of a bone graft?

A

What factors influence the rate, contributions, and successful incorporation of a bone graft? Factors influencing the rate, contributions, and successful incorporation of a bone graft include the:
1) host bed 2) viability of the bone graft 3 ) volume of bone grafted 4) growth factor activity of the host 5) metabolic activity index and 6) homosctructural function of the bone graft.

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10
Q

How is the metabolic activity index used to represent recipient condition in bone graft procedures?

A

The metabolic activity index (MAI), a composition of heart rate, blood flow, basal metabolic rate, respiratory rate, and body temperature, is used to represent recipient condition in bone graft procedures.

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11
Q

Why is a healthy, highly vascularized host bed crucial for the success of graft survival and incorporation?

A

is crucial for the success of graft survival and incorporation.

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12
Q

What are the vital components for the osteogenic, osteoinductive, and osteoconductive properties of bone grafts?

A

Vital components for the osteogenic, osteoinductive, and osteoconductive properties of bone grafts include viable cells on graft components and graft microstructure.

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13
Q

How does structural damage or compromised cell viability impact graft incorporation and its value in the healing process?

A

Structural damage or compromised cell viability delays graft incorporation and reduces the value of the graft for the healing process.

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14
Q

What mechanisms are reported to enhance the function and incorporation of bone grafts, especially allogeneic or acellular grafts, according to the text?

A

Mechanisms reported to enhance the function and incorporation of bone grafts include the addition of antibiotics, the use of adult mesenchymal stem cells (MSCs) and platelet-rich plasma (PRP), and combining bone marrow–derived MSCs with allografts

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15
Q

What are the sites for Autograft harvest?

A

Sternum, tuber coxae and proximal tibia

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16
Q

Where is bone autograft harvest typically performed during orthopedic surgery?

A

As a separate procedure initiated during orthopedic surgery.

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17
Q

Why is the use of a different team recommended during bone autograft harvest?

A

To reduce surgical time, maintain graft asepsis, and facilitate rapid graft transfer between harvest and surgical sites.

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18
Q

How many usable nuclei are there within the sternum for bone autograft harvest?

A

Six or seven.

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19
Q

In which position is the sternum easily accessed for autograft harvest in horses?

A

Dorsal recumbency.

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20
Q

Why might the sternum be less desirable for forelimb fractures during autograft harvest?

A

Due to the proximity between the graft harvest and fracture surgical sites.

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21
Q

What is the recommended incision length for approaching the 4th, 5th, and 6th sternebrae? How many sternebrae has the horse? Where should be taken?

A

An 8- to 10-cm ventral midline incision.

6-8 sternebrae
More causal sternebrae should be chosen because they are covered by less muscle, are closer together and contain more cancellous bo

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22
Q

How is hemostasis maintained during sternebrae autograft harvest?

A

With electrocoagulation.

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23
Q

What instrument is used to reflect and remove hyaline cartilage over the sternebrae?

A

A periosteal elevator or rongeur.

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24
Q

What should be avoided during curettage to prevent penetrating the thoracic cavity?

A

Curettage should not go beyond the hyaline cartilage at the end of each sternebrae.

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25
Q

Why should incorporation of cartilage into the cancellous bone graft be avoided?

A

To avoid complications.

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26
Q

How are the pectoral fascia and subcutaneous tissues closed after sternebrae autograft harvest?

A

As separate layers, typically with continuous suture patterns.

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27
Q

Why might a drain be incorporated into the subcutaneous space for the first 24 hours after sternum autograft harvest?

A

To avoid fluid accumulation due to the dependent and vascular nature of the location.

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28
Q

What type of suture pattern is recommended for closing the skin after sternum autograft harvest?

A

Tension-relieving suture pattern, such as vertical mattress.

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29
Q

Where is the skin incised for tuber coxae autograft harvest?

A

Along the ventrocaudal eminence of the tuber coxae.

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30
Q

How much bone is exposed during tuber coxae autograft harvest?

A

4 to 5 cm.

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31
Q

How are cancellous bone columns removed from the tuber coxae?

A

Using hollow drill bits (4–6 mm).

32
Q

What should be avoided during tuber coxae autograft harvest to prevent complications?

A

Puncture through the thin medial cortex of the ileum.

33
Q

What are the recommended closure techniques after tuber coxae autograft harvest?

A

Separate fascial and subcutaneous tissue layers closed with continuous suture patterns; skin sutured with tension-relieving sutures.

34
Q

What complications are associated with traditional bone autograft harvest techniques and sites?

A

Incisional edema, drainage, infection, dehiscence, and osteomyelitis in the donor bone.

35
Q

How many noncollagenous matrix proteins are present in the bone fracture environment?

A

Over 200.

36
Q

What two key components form the nanostructure in bone?

A

Collagen and hydroxyapatite (HA).

37
Q

How do natural and synthetic bone graft substitutes create a biomimetic environment for bone formation?

A

Through structure and composition.

38
Q

What benefits do prepared grafts offer over traditional autografts?

A

They obviate harvest morbidity, are not affected by harvested cell survival, and provide virtually unlimited customizable graft material.

39
Q

How does decellularization of bone tissue affect immunogenicity?

A

It reduces immunogenicity while conserving three-dimensional ECM structure.

40
Q

What additional capabilities can exogenous cells confer to bone graft substitutes?

A

Osteogenic capabilities.

41
Q

What elements are often incorporated into bone graft substitutes that may not be feasible with natural bone grafts?

A

Growth factors, antimicrobials, and genetically modified cells.

42
Q

How do inorganic and organic components in bone graft substitutes direct cell differentiation and ECM production?

A

They stimulate distinct osteogenic pathways.

43
Q

What has the confirmed contribution of exogenous adult MSCs led to in the use of bone graft substitutes?

A

Their use as MSC carriers.

44
Q

What role do bone graft substitutes play in supporting both exogenous and endogenous cell osteogenesis?

A

They support both types of cell osteogenesis.

45
Q

Why may there be a slow adoption of bone graft substitutes in equine therapies?

A

Due to a relative abundance of autologous bone and the associated costs for fewer applications.

46
Q

What is demineralized bone matrix (DBM) typically created by?

A

Treatment of bone with hydrochloric acid.

47
Q

What is the purpose of hydrochloric acid treatment in creating DBM?

A

To destroy osteocytes, reduce antigen stimulation, while retaining bone morphogenetic proteins (BMPs) and insoluble collagen matrix.

48
Q

What size range of equine DBM particles was found to be the most osteoinductive in a study?

A

2 to 4 mm3.

49
Q

In what equine model was bone formation in DBM sites inferior to autogenous cancellous bone graft sites?

A

Equine rib cortical defect model.

50
Q

What is the most common calcium phosphate ceramic formed when bioreactive calcium phosphate cement is moistened?

A

Hydroxyapatite.

51
Q

What growth factor has a high affinity for calcium phosphate and induces de novo bone formation?

A

Recombinant human BMP-2 (rhBMP2).

52
Q

What polymers are widely used in tissue engineering due to high biocompatibility and biodegradability?

A

Collagen, chitosan, polyglycolic acid (PGA), and polylactic acid (PLA).

53
Q

What may limit the enthusiasm for the use of natural and synthetic polymers in equine applications?

A

Disadvantages such as low mechanical strength, high degradation rates, inflammatory degradation products, and small particle formation.

54
Q

What are the most common bone-substitute ceramics mentioned in the text?

A

Hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP).

55
Q

What are the benefits associated with calcium phosphate-based ceramics?

A

Biocompatibility, osteoconduction, and osteointegration.

56
Q

What glycoproteins naturally bind to calcium phosphate in ceramics?

A

Fibronectin and laminin

57
Q

What factors influence bone formation in ceramic implants?

A

Macrostructure (macroporosity, concavity) and surface structure (microporosity, strut porosity, particle size).

58
Q

Where does bone typically form within porous ceramic implants?

A

Within the inner pores and concave surfaces.

59
Q

What type of surfaces do osteoblasts more readily populate and function on?

A

Grooved surfaces.

60
Q

What role does greater porosity, including micropores within macropores, play in ceramics?

A

It appears to confer better osteoinduction.

61
Q

How does the addition of silicate to calcium phosphate bone graft substitutes affect new bone formation?

A

It is reported to increase new bone formation.

62
Q

What are the different forms of bioactive glass mentioned in the text?

A

Silicate (45S5, 13-93),
borate/borosilicate (13-93B2, 13-93B3),
and phosphate.

63
Q

What bioactive behavior is attributed to the use of bioactive glass as a bone graft substitute?

A

The formation of bonelike carbonate apatite on the surface.

64
Q

What elements are sometimes added to bioglass to enhance bone growth?

A

Copper, zinc, and strontium.

65
Q

How do metals like titanium and tantalum with porosity similar to trabecular bone function as bone graft substitutes?

A

They have mechanical properties that make them potential candidates for bone graft substitutes.

66
Q

What are some disadvantages of trabecular metals?

A

Limited tissue adherence, which may contribute to implant loosening, and local accumulation of metal ions.

67
Q

What is biodegradation, and how does it relate to bone graft substitutes?

A

Biodegradation is a biological mechanism by which certain materials resorb partially or completely over time. It is relevant to the resorption of synthetic bone graft materials.

68
Q

How do polymers break down in the process of biodegradation?

A

From cleavage of hydrolytically or enzymatically sensitive bonds.

69
Q

What are the factors that affect the rate of polymer biodegradation?

A

Polymer chemical structure, hydrophilicity/hydrophobicity, crystalline/amorphous morphology, glass transition temperatures, copolymer ratio, and molecular weight.

70
Q

How does metal degradation occur?

A

By electrochemical dissolution, wear, or a synergistic combination of the two.

71
Q

What is the ideal rate of biodegradation for synthetic bone graft materials?

A

It should parallel the rate of new bone formation.

72
Q

What is the potential advantage of bioreactors in bone tissue engineering?

A

They make it possible to induce and maintain fluid flow shear stress with fluid flow and scaffold structure, closely mimicking in vivo bone processes.

73
Q

What are the disadvantages of using TC as donor site?

A

Time-consuming●● Requires patient in lateral recumbency●● Decubital ulcers or soft tissue trauma overthe tuber coxae may preclude its use

74
Q

What are the risks with the collection of bone graft from sternum?

A

Risk of puncturing thoracic or pericardial cavities exists - pneumothorax and hemothorax

75
Q

What are the risks of Tibia bone graft collection? when is it useful?

A

Risk of pathologic fracture on anestheticrecovery has been recognized

Useful in cases where smaller amounts of graftmaterial (<50 ml) are required, such as inarthrodeses, bone cysts or acute fractures

75
Q

What other sites can be used for collection of bone graft?

A
  1. Humerus (catastrophic fracture during recovery!!),
  2. rib (risk pneumothorax/hemothorax),
  3. 4th coccygeal vetebra (requires tail amputation)
76
Q

what horses are at major risk of tibia fracture during recovery?

A

young horses

A U E R S & T (123 decks)

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