Biology of Fracture Healing

Question 1

what makes up the biology of bone healing?

Answer 1

location
cellular response
soft tissue envelope

Question 2

what happens with blood flow after an injury to bone?

Answer 2

surviving vasculature becomes enhanced
re-establishment of medullary circulation
extraosseous circulation

Question 3

what is extraosseous circulation?

Answer 3

new, transient blood supply from surrounding soft tissues

Question 4

what does instability of a fracture with bone fragments favor?

Answer 4

resorption of bone

Question 5

what is secondary bone healing?

Answer 5

healing via callus formation

Question 6

what are the phases of secondary bone healing?

Answer 6

injury
inflammatory phase
reparative phase
remodeling phase

Question 7

what happens in the inflammatory phase of secondary bone healing?

Answer 7

hemorrhage at fracture site
resorption of bone ends
formation of granulation tissue

Question 8

what is the size of the callus proportional to?

Answer 8

amount of motion at fracture site

Question 9

what happens in the remodeling phase of secondary bone healing?

Answer 9

slow change of callus and bone
haversian remodeling

Question 10

what is required for primary bone healing?

Answer 10

absolute stability

Question 11

how much of a gap should there be for primary bone healing?

Answer 11

<0.8mm

Question 12

what is malunion?

Answer 12

healed fracture in which anatomic alignment was not achieved

Question 13

what is nonunion?

Answer 13

arrested repair process that requires surgical intervention to create environment conducive to bone healing

Question 14

what are some things that can cause a delayed union?

Answer 14

systemic issues
local post injury response
how the fracture was managed

Question 15

how can you tell a fracture is delayed union?

Answer 15

most long bones will have bone bridging the fracture
healing should look active

Question 16

what is a delayed union?

Answer 16

healing slower than anticipated

Question 17

is surgical intervention needed for a nonunion?

Answer 17

yes

Question 18

what is a nonunion a result of?

Answer 18

often technical failure or decision making
poor biology at the fracture site

Question 19

what does a biologically active nonunion look like?

Answer 19

varying amount callus
hypertrophic, slightly hypertrophic, oligotrophic

Question 20

what does a biologically inactive nonunion look like?

Answer 20

atrophic, dystrophic, necrotic, defect
biologically inactive: no cells trying to heal

Question 21

what can you use a bone graft to do?

Answer 21

increase biology

Question 22

what are the types of bone graft?

Answer 22

autogenous: cancellous, cortical
allogenic

Question 23

what are the three properties of an autogenous cancellous bone graft?

Answer 23

osteogenic
osteoinductive
osteoconductive

Question 24

when will healing occur in the presence of infection?

Answer 24

if it is stable
infection not too bad

Question 25

how do fractures get infected?

Answer 25

direct inoculation usually hematogenous extension from soft tissue infection

Question 26

why are infections with surgical implants so hard to clear?

Answer 26

biofilms form on implant: bacterial glycocalyx

Question 27

what is a glycocalyx?

Answer 27

polysaccharide coating

Question 28

why does a glycocalyx matter?

Answer 28

helps protect bacteria prevents identification of antigens alters antibiotic effectiveness

Question 29

how can you treat a fracture site infection?

Answer 29

surgical debridement exchange or autoclave and place implant lavage/drainage stability culture and sensitivity: tissue and implant remove implants after healed

Question 30

what is the most important factor in re-establishing vascularity to the bone?

Answer 30

extraosseous circulation from surrounding soft tissues

Question 31

what happens in the reparative phase?

Answer 31

new blood vessels fibrous tissue cartilage woven bone callus

Question 32

what happens in haversian remodeling?

Answer 32

osteoclastic resorption-cutting cone osteoblasts deposit osteoid along walls of resorption

Question 33

when does haversian remodeling start in primary bone healing?

Answer 33

from the onset

Question 34

what are some things for osteoinduction?

Answer 34

decalcified bone matrix cancellous bone graft

Question 35

what is osteomyelitis?

Answer 35

inflammation of bone marrow, cortex, and periosteum

Question 36

what is the most common form of osteomyelitis?

Answer 36

chronic post-traumatic

Question 37

what does re-establishment of medullary circulation after an injury do?

Answer 37

replaces supply from principal nutrient artery

Question 38

what are the components of primary bone healing?

Answer 38

gap <0.8mm haversian remodeling from onset must have apposition requires absolute stability

Question 39

by 8 weeks _______ of new haversian canals traversed fracture site in contact healing

Answer 39

60%

Question 40

what are the locations for an autogenous cancellous bone graft?

Answer 40

proximal humerus proximal tibia wing of ilium

Question 41

what does an allograft provide?

Answer 41

osteoconduction minimal osteoinduction no viable cells

Question 42

what are the modes of infection?

Answer 42

concurrent vascular compromise soft tissue injury foreign material instability impaired host defense complication with fracture repair most common

Question 43

why are infections so hard to clear?

Answer 43

ischemic areas of tissue structural blockade biofilms: bacterial glycocalyx