Bone Healing/Fx Decision Making

Question 1

4 fundamental questions of fx decision making

Answer 1

1. Is it anatomically reconstructible or not?
2. Where is the fx?
3. What are the fx biomechanics? (How strong does it need to be to heal?)
4. What is the fx biology? (How long will it take to heal?)

Question 2

anatomically reconstructible achieves

Answer 2

absolute stability w/ no fx gap and interfragmentary compression

Question 3

> 3 pieces =

Answer 3

not anatomically reconstructible

Question 4

load sharing is achieved if…

Answer 4

a fx is anatomically reconstructible (2 (maybe 3) piece fx)

Question 5

stability of a fx = 5 key considerations

Answer 5

1. Type of fx
2. Whether anatomically reconstructed
3. Method of repair
4. Single or multi-limb injury
5. Patient size + activity levels

Question 6

list the biological factors of fx assessment

Answer 6

1. Age of animal
2. Blood supply
3. Location of fx/type of bone
4. Infection
5. Concurrent disease/injuryes

Question 7

how does bone type influence fx healing?

Answer 7

Metaphyseal fxs heal faster than diaphyseal dt higher cancellous to cortical bone ratio
- pelvis and scapula also have high cancellous bone = heal faster

Question 8

4 stages of indirect bone healing

Answer 8

1. Inflammation - fx haematoma + GFs
2. Soft callus –> fibroblasts form fibrous tissue
3. Hard callus –> cartilage tissue undergoes endochondral ossification
4. Remodelling: via osteoclasts + osteons (Haversian remodelling) - months to years

Question 9

when does indirect bone healing occur

Answer 9

if >2% strain

Question 10

3 requirements of direct bone healing

Answer 10

1. Perfect anatomic reduction (gap <1mm)
2. Absolute stability (<2% strain)
3. Good blood supply

Question 11

describe process of direct bone healing

Answer 11

bone healing proceeds directly to the harversian remodelling stage where bone formation by osteons across fx line

Question 12

a simple, uncomplicated fx in a young animal – you would expect to see a mineralised callus in how many wks?

Answer 12

as fast as 2-3wks post op

Question 13

radiographic findings of an xs large callus w/ no bridging mineralisation indicates

Answer 13

viable non-union

Question 14

rad finding /w absence of callus in fx where indirect healing expected indicates

Answer 14

non-viable non-union

Question 15

which stage of indirect bone healing is radiographically apparent?

Answer 15

the hard callus

Question 16

the size of the callus (given a good blood supply exists) is proportional to…

Answer 16

the degree of instability

Question 17

no radiographic callus is expected in what type of healing?

Answer 17

direct

Question 18

direct healing usually results in absence of fx lines on rads in how many weeks?

Answer 18

8-12wks

Question 19

why may fracture lines appear larger 2-3wks post op in direct healing?

Answer 19

dt some bone resorption – widening the gap to reduce strain (as small gaps magnify strain)

Question 20

how does strain act on comminuted fxs?

Answer 20

comminuted fxs dissipate strain –> callus/indirect healing

Question 21

what type of bone is used in bone grafts?

Answer 21

cancellous –> highly trabecular/spongey bone

Question 22

why are autogenous bone grafts used?

Answer 22

histocomptability/ no problem with rejection or inflammation of the graft is cancellous bone is translocated w/in the body from the same individual

Question 23

what do bone grafts provide?

Answer 23

1 Osteogenesis: viable translocated bone cells produce new bone

2. Osteoinduction: GFs induce surrounding pluri-potent cells to transform into fibroblasts + osteoblasts to produce new bone
3. Osteoconduction: encourages revascularisation via provides trellis/framework for new blood vessels to bridge gap

Question 24

Do cancellous bone grafts provide structural support?

Answer 24

no