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Ortho > Bone Healing And Grafts > Flashcards

Bone Healing And Grafts Flashcards

1
Q

Primary osteons

A

Form during bone growth

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2
Q

Secondary osteons

A

Form during remodeling

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3
Q

Mechanisms of new bone formation

A

Cutting cones
Intramembranous ossification
Endochondral ossification

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4
Q

Cutting cones

A

Primary bone healing + remodeling

Osteoclasts lead to remove bone, osteoblasts trail to lay down new bone

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5
Q

Intramembranous ossification

A

Does not require cartilage precursor

Increases width of bone

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6
Q

Endochondral ossification

A

Cartilage precursor

Chondrocyte hypertrophy —> calcification —> ossification

Increases bone length

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7
Q

Prerequisites for bone healing

A

Adequate blood supply
Interfragmentary stability
Absence of infection (or subclinical/well-controlled infection)

Bone formation requires low strain (<2%)

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8
Q

Strain

A

Change in length over length under an applied biomechanical force

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9
Q

Goals of fracture stabilization

A

Decrease interfragmentary strain

Decrease fracture gap

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10
Q

Indirect bone healing

A
  1. Hematoma formation
  2. Fibrocartilage callus formation
  3. Bony callus formation
  4. Bone remodeling
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11
Q

Strain tolerance

A

Granulation tissue: 100%
Cartilage: 10%
Lamellar bone: 2%

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12
Q

Types of fracture healing

A
  1. Direct (primary) healing: contact healing, gap healing
  2. Indirect (secondary) healing
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13
Q

Direct (primary) bone healing

A

Occurs only with anatomic reduction + rigid stability

***no micromovement

<2% interfragmentary strain + <1 mm fracture gap (<0.01 for contact healing)

Cutting cones, lack of callus formation

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14
Q

Contact healing

A

Occurs in zones of cortical bone contact (<0.01 mm gap)

Cutting cones, direct formation of lamellar bone in axial direction

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15
Q

Gap healing

A

<1mm, <2% strain

Initially filled with loose connective tissue

Osteoblasts deposit lamellar bone in gap

Cutting cones formed longitudinally

Secondary osteoblasts reconstruction

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16
Q

Indirect (secondary) bone healing

A

Less stable fractures
Callus formation to stabilize / decrease strain
Indirect healing through transformation of fibrous tissue and cartilage

17
Q

Stages of indirect bone healing

A
  1. Inflammation (0-7 d)
  2. Repair (soft callus 1-3, bony callus 3-6)
  3. Remodel (> 8 wks to yrs)
18
Q

Inflammatory phase of indirect bone healing

A

Hematoma formation
Revascularization
Resorption of fragment ends + hematoma

19
Q

Repair phase

A

Hematoma —> granulation tissue

Granulation tissue —> fibrocartilage

Mesenchymal cells differentiate into chondrocytes or osteoblasts

20
Q

Remodeling phase

A

Regain function / strength

Formation of new secondary osteons

External callus disappears

Reestablishment of medullary cavity

Secondary remodeling - involves cutting cones

21
Q

Osteogenesis

A

Osteoblasts in bone graft material contribute to new bone growth

22
Q

Osteoinduction

A

Bone graft recruits osteoprogenitor cells and induces new bone formation

23
Q

Osteoconduction

A

Serves as a scaffold for osteoprogenitor cells

24
Q

Osteopromotion

A

Enhancement of osteoinduction without possession of osteoinductive properties (rare, i.e. enamel matrix)

25
Q

Bone graft functions

A

Osteogenesis
Osteoinduction
Osteoconduction
Osteopromotion
Structural support

26
Q

Bone graft indications

A

Augment repair, speed healing, promote healing of non-unions / infected fractures

Enhancing healing (fracture, osteotomies, delayed/non-union)
Bone loss (fracture, excision from neoplasm)

27
Q

Bone graft sources

A

Autograft
Allograft
Xeongraft

28
Q

Types of bone graft

A

Cancellous bone
Cortical bone
Corticocancellous bone
Demineralized bone matrix
Synthetic bone grafts

29
Q

Cancellous bone graft

A

Metaphyseal trabecular bone
Endosteal + marrow cells
Autogenous is gold standard

Properties: osteogenic, osteoinductive, osteoconductive

30
Q

Cortical bone grafts

A

Strut of long bone providing mechanical support

Osteoconductive (i.e. provides scaffold)

31
Q

Harvesting bone grafts

A

Cancellous - aseptic, prepare surgical site in advance, separate surgical instruments, drill hole through 1 cortex use currette to obtain cancellous bone

32
Q

Cancellous donor sites

A

SA: lateral tubercle of proximal humerus; proximomedial tibia; craniodorsal iliac spine, subtrochanteric region of medial condole of femur

LA: ilium, sternum

33
Q

Bone graft substitutes

A

Synthetics: calcium phosphate, hydroxyapatite, bio active glasses, polymers (osteoconductive)

Growth factors (BMP, TGF-B —> osteoinductive)

34
Q

Assesment of healing

A

SA: 2 orthogonal views, 3/4 cortices with bridging callus

LA: 4+ views

Callus formation, appearance of fracture site, margins of fracture fragments, bone opacity/density, periosteal/endosteal reaction

Ortho (15 decks)

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