Bone growth and fracture healing Flashcards
How does bone grow
hyaline cartilage model (long bone) primary ossification centre - grow - SOC - at each end - medullary cavity - epiphyseal plate
Long bone anatomy
multiple growth plates
growth plate at knew provides
greatest length at development
What is the metaphysiis
flare at the end
What is the diaphysis
the shaft
What is the Epiphysis
On joint side of physis
Cortical bone is a
it is predominantly ?
impact structure
circular lamellae - blood vessels
diaphysis
resists - bending and torsion
Cancellous bone is a
Shock absorber
mainly metaphysisis
What is a fracture
break in structural continuity of bone
crack, break, split , crumpling
Why do bones fail?
High energy transfer - takes a lot to break
- repetitive stress in normal bones - stress fracture
older people have/ other bone conditions that can cause fracture
low energy transfer in abnormal bones
osteoporosis
osteomalacia, metastatic tumour
Fracture biology is (2)
what process is it?
- mechanical and structural failure of bone
- disruption of blood supply
regernative process (no scar) (4 stages)
What is stage 1 and when does it occur
what cells come?
INFLAMMATION
immediately after fracture - hepatoma and fibrin clot released
platelets , neutrophils, macrophages, lysosomal enzymes
What repair cells come in? (2 - explain)
fibroblasts
mesenchymal and osteoprogenitor cells - (cells in muscle and soft tissue) (cells from the canal) - fibro and osteoblasts
Angiogenesis
- low oxygen gradient in centre of fracture
- macrophages produce angiogenic factors under hypoxic conditions
How might doctors affect inflammation?
NSAIDS
loss of hepatoma - open fracture or surgery
extensive tissue damage - poor blood supply
Platelet concentrates ? what do they release (4)
“Buffy coat”
Platelet derived growth factor (PDGF)
TGFB)
insulin growth factors
VEGF
What is stage 2
soft callus
When does soft callus begin and when does it last until?
what is there a continued increase in?
when pain and swelling subsides
bony fragments are united by cartilage or fibrous tissue
- vascularity
soft callus - how can we affect it?
- replace cartilage (DMB)
- Jump straight to bone (bone graft and substitutes)
What is an autogenous cancellous bone graft
gold standard
- osteoconductive
- osteoinductive
what happens in stage 3?
In a typical long bone fracture what bone formation is there?
hard callus
conversion of cartilage to woven bone
Endochondrial
Membranous
What is increasing in stage 3
rigidity
Obvious callus
What happens in stage 4 bone remodelling ?
Conversion of woven bone to lamellar bone
What is reconstituted in stage 4?
medullary
What is critical for the progression of fracture healing
Mechanical proporties of tissue and their environment
What is strain
Degree of instability
If strain is low what happens?
induction of tissue differentiation fails
too high and healing process does not progress to bone formation
Delayed union is?
failure to heal in expected time
What is non-union (6)
- failure to heal
- failure calcification fibrocartilage
- abundant callus formation
- pain and tenderness
sclerosis
