bone growth and fracture healing

Question 1

Long bone anatomy

Answer 1

diaphysis (shaft)
metaphysis- flare end of shaft
epiphysis-
on joint side of physis
plate
medullary canal

Question 2

cortical vs cancellous

Answer 2

diaphysis| metaphysis
resists: bending; torsion| resists absorbs compression
laid down circumferentially | site of longitudinal growth
less biologically active | very biologically active

Question 3

fracture biology

Answer 3

four stages

Question 4

Stage 1

Answer 4

1) inflammation
hematoma fibrin clot
platelets, neutrophils,
by products of cell death lysosomal enzymes
Fibroblasts
mesenchymal & osteoprogenitor cells (transformed endothelial cells from medullary canal/ periosteum
angiogenesis-oxygen gradient required, macrophages produce angiogenic factors under hypoxic conditions
treatment:
NSAIDs
Platelet concentrates (buffy coat)
PDGF, TGF-B, IGF, VEGF

Question 5

Stage 2

Answer 5

soft callus
begins when pain and swelling subside
until bony fragments united
some stability but angulation can still occur
treatment:
replace cartilage DMB (demineralised bone matrix)
autogenous cancellous bone graft- gold standard osteoconductive, osteoinductive

Question 6

stage 3

Answer 6

hard callus
conversion to woven bone
endochondral and membranous bone formation
increasing rigidity

Question 7

stage 4

Answer 7

conversion of woven bone into lamellar bone
medullary canal is reconstituted
responds to loading characteristics wolff’s law

Question 8

strain % of change of initial dimension

Answer 8

too low mechanical induction of tissue differentiation fails

too high healing process does not progress to bone formation

Question 9

non union

Answer 9

failure calcification fibrocartilage
excessive instability, excessive osteoclasis
abundant callus formation
-too rigid to the point movement too limited to trigger induction of tissue differentiation
sclerosis- excessive bone around the edges

Question 10

alternative treatment

Answer 10

different fixation

bone grafting