Flashcards in Bone Growth and Repair Deck (32)
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1
What is the anatomy of a long bone?
-Diaphysis (shaft)
-Metaphysis (Flare at the end of shaft)
-Physis (growth plate)
-Epiphysis (On joint side of physis)
-Medullary canal
2
Briefly describe bone growth.
-Hyaline cartilage model
-Primary ossification centre
-Secondary ossification centre
-Formation of bone (compact bone, periosteum, spongy bone, articular cartilage and epiphyseal growth plate)
3
What are the features of cortical bone?
-Forms diaphysis
-Resists bending and torsion
-Laid down circumferentially
-Less biologically active
4
What are the features of cancellous bone?
-Forms metaphysis
-Resists/absorbs compression
-Site of longitudinal growth (physis)
-Very biologically active
5
What is a fracture?
-Break in structural continuity of bone
-May be a crack, break, split, crumpling or buckle
6
Why do fractures occur?
-High energy transfer in normal bones
-Repetitive stress in normal bones can result in stress fractures
-Low energy transfer in abnormal bones (osteoporosis, osteomalacia, metastatic tumour, other bone disorders)
7
What is the biology behind fractures?
-Mechanical and structural failure of bone
-Disruption of blood supply
-Regenerative process (no scar within the substance of the bone)
8
What are the 4 stages of fracture healing?
-Inflammation
-Soft callus
-Hard callus
-Bone remodelling
9
What takes place during stage 1 of fracture healing?
-Begins immediately after fracture
-Formation of haematoma and fibrin clot
-Aggregation of platelets, PMNs, neutrophils, monocytes and macrophages
-By product of cell death= lysosomal enzymes
-Action of fibroblasts
-Mesenchymal and osteoprogenitor cells
-Angiogenesis
10
What role do mesenchymal and osteoprogenitor cells play in fracture healing?
-Transformed endothelial cells from medullary canal and/or periosteum
-Osteogenic induction of cells from muscle and soft tissues
11
How does angiogenesis occur?
-Oxygen gradient required (low)
-Macrophages – produce angiogenic factors under hypoxic conditions
12
How stage 1 of fracture healing be affected?
NSAIDs
-Very of for pain relief by act against inflammation increasing recovery time
Loss of haematoma
-Can occur in open fractures and surgery
-Slows down recovery process as haematoma kick starts the process
Extensive tissue damage
-Poor blood supply
13
What can be injected if haematoma is loss/want to speed up healing?
Platelet concetrates= Buffy coat
-Platelet-derived growth factor (PDGF)
-Transforming growth factor-beta (TGF-B)
-Insulin like growth factor (IGF)
-Vascular endothelial growth factor (VEGF)
14
When does stage 2 begin?
When the pain and swelling subside
15
How long does stage 2 last?
Until the bony fragments are united by cartilage or fibrous tissue
16
Describe the state of the fracture during stage 2.
-Some stability
-Angulation can still occur
-Continued increase in vascularity
17
How can stage 2 of fracture healing be affected?
Replace cartilage
-Demineralised bone matrix
Jump straight to bone
-Bone grafts
-Bone substitutes
18
Why is autogenous cancellous bone graft gold standard?
-Osteoconductive
-Osteoinductive
-Best choice for the majority of bone graft needs
19
What types of allograft bone is there?
-Cortical
-Cancellous
-Fresh
-Prepared
-Structural
20
What are the features of allograft bone?
-Osteoconductive
-Not osteoinductive
-Creeping substitution
-Risk of Disease transmission
21
What occurs during stage 3?
-Conversion of cartilage to woven bone
-Typical long bone fracture (endochondrial and membranous bone formation)
22
Describe the state of the fracture in stage 3.
-Increasing rigidity
-Secondary bone healing
-Obvious callus
23
What takes place during stage 4?
-Conversion of woven bone to lamellar bone
-Medullary canal is reconstituted
-Bone responds to loading characteristics Wolff’s Law
24
What is critical for the progression of fracture healing?
Mechanical properties of tissue and their environment
25
How is degree of instability expressed?
Magnitude of strain (% change of initial dimension)
26
What happens if strain is too low?
Mechanical induction of tissue differentiation fails
27
What happens if strain is too high?
Healing process does not progress to bone formation
28
Delayed union
Failure to heal in expected time
29
What are the causes of delayed union?
-High energy injury
-Distraction (increased osteogenic jumping)
-Instability
-Infection
-Steroids
-Immune suppressants
-Smoking
-Warfarin
-NSAID
-Ciprofloxacin
30
