Bone Growth and Repair Flashcards
(32 cards)
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
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)
What are the features of cortical bone?
- Forms diaphysis
- Resists bending and torsion
- Laid down circumferentially
- Less biologically active
What are the features of cancellous bone?
- Forms metaphysis
- Resists/absorbs compression
- Site of longitudinal growth (physis)
- Very biologically active
What is a fracture?
- Break in structural continuity of bone
- May be a crack, break, split, crumpling or buckle
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)
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)
What are the 4 stages of fracture healing?
- Inflammation
- Soft callus
- Hard callus
- Bone remodelling
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
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
How does angiogenesis occur?
- Oxygen gradient required (low)
- Macrophages – produce angiogenic factors under hypoxic conditions
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
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)
When does stage 2 begin?
When the pain and swelling subside
How long does stage 2 last?
Until the bony fragments are united by cartilage or fibrous tissue
Describe the state of the fracture during stage 2.
- Some stability
- Angulation can still occur
- Continued increase in vascularity
How can stage 2 of fracture healing be affected?
Replace cartilage
-Demineralised bone matrix
Jump straight to bone
- Bone grafts
- Bone substitutes
Why is autogenous cancellous bone graft gold standard?
- Osteoconductive
- Osteoinductive
- Best choice for the majority of bone graft needs
What types of allograft bone is there?
- Cortical
- Cancellous
- Fresh
- Prepared
- Structural
What are the features of allograft bone?
- Osteoconductive
- Not osteoinductive
- Creeping substitution
- Risk of Disease transmission
What occurs during stage 3?
- Conversion of cartilage to woven bone
- Typical long bone fracture (endochondrial and membranous bone formation)
Describe the state of the fracture in stage 3.
- Increasing rigidity
- Secondary bone healing
- Obvious callus
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
What is critical for the progression of fracture healing?
Mechanical properties of tissue and their environment
