SL1 - Bone Healing

Question 1

bone is composed of

Answer 1

minerals - Ca, P, Mg

Organic Matrix - type I collagen, proteoglycans, glycosaminoglycans

Question 2

T/F there is separate venous drainage for cortex and medullary canal

Answer 2

true

Question 3

osteoblasts

Answer 3

produce osteoid (unnmineralized bone matrix) on bone surface

Question 4

osteocytes

Answer 4

osteoblasts that have been encased in mineral matrix

maintain bone matrix

Question 5

osteoclasts

Answer 5

active in areas of bone remodeling

reside near bone surface

Question 6

what are the 3 phases of bone healing

Answer 6

inflammation phase

repairative phase

remodeling phase

Question 7

inflammatory phase

Answer 7

lasts about 2-3 weeks

death of osteocytes results in release of lysosomal enzymes

necrotic material at site of the fracture is source of inflammatory respose

Question 8

repair phase

Answer 8

migration of osteoprogenitor cells - forms periosteal callus

angiogenesis - transient blood supply from surrounding soft tissue

deposition of Ca hydroxyapatite in matrix - callus mineralization

cartilage replaced by bone via endochondral ossification

Question 9

remodeling phase

Answer 9

begins when fracture is bridged by callus

woven bone remodeled into lamellar bone via osteoclasts and osteoblasts

Question 10

remodeling phase is directed by ______

Answer 10

stresses of weight bearing

Question 11

types of bone healing

Answer 11

primary/direct

secondary/indirect

Question 12

contact healing

Answer 12

primary bone healing

occurs with compression of bone ends under rigid fixation

no cartilaginous callus formed

Question 13

gap healing

Answer 13

gap between fracture ends is < 1mm

granulation tissue at gap followed by transversely oriented lamellar bone

haversian remodeling occurs at ~ 3 weeks post stabilization

Question 14

T/F primary bone healing outmoded in favor of secondary bone healing

Answer 14

True

exceptions: articular fractures and simple, stable fractures

Question 15

secondary bone healing

Answer 15

fracture ends dont touch

micromotion at fracture promotes formation of callus

bone heals via mineralization of fibrocartilagenous callus into boney callus

Question 16

biological osteosynthesis

Answer 16

secondary bone healing

fracture ends not compressed - protect surrounding soft tissue, protect blood supply

plates in bridging mode, external skeletal fixaition, interlocking nails

Question 17

average fracture healing time

Answer 17

6-8 weeks

Question 18

factors that affect bone healing

Answer 18

fracture configuration/severity

soft tissue damge

stability of repair

presence of infection

patient factors (age, weight, disposition, comorbities)

complience

Question 19

what is required to assess bone healing

Answer 19

orthogonal radiographs

Question 20

4 A’s of evaluation

Answer 20

alignment

apposition

apparatus

activity

Question 21

when does clinical union occur

Answer 21

when bone is strong enough that fixation is no longer necessary

Question 22

what is a delayed union

Answer 22

healing is prolonged beyond normal expected time course

fracture lines remains evident with feathery/wooly ends

callus is visible but lacks appropriate mineralization

no sclerosis of bone ends

Question 23

malunion

Answer 23

failure to re-establish normal function in face of healing

Question 24

which malunions are the lease tolerated

Answer 24

roatation and lateral translation

Question 25

viable nonunion

Answer 25

biologically active fracture with cartilage and fibrous tissue between fracture ends

Question 26

nonviable nonunion

Answer 26

fracture ends are sclerotic with rounded bone edges and visible fracture gap (bone have blood supply) ## Footnote *dystrophic, necrotic, defect, atrophic*

Question 27

treatment options for delayed union

Answer 27

**pre-emptive treatment is ideal** - bone grafts, increased mechanical stiffness of implants, bone morphogenic protein ## Footnote *if delayed untion is anticipated - rechecks q 3-4 weeks*

Question 28

treatment options for non-union

Answer 28

rigid stabilization removal of loose implants encourage biologically active environment - graft, marrow, demineralized bone matrix, bone morphogenic proteins remove non-viable bone +/- amputation