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Phase 1 > AO Principles > Flashcards

AO Principles Flashcards

1
Q

according to AO, what is the most common microbial agent causing the majority of orthopedic infections?

A

Staph intermedius

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2
Q

what three methods of planning fracture fixation will aid in implant selection?

A

direct overlay
intact contralateral bone
bone specimen of a similar size animal

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3
Q

what are the six basic modalities used to decrease pain, reduce inflammation, and stimulate normal healing?

A 
local hypo and hyper thermia
massage
therapeutic exercise
hydrotherapy
ultrasound 
electrical stimulation
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4
Q

what is effleurage?

A

superficial or light stroking massage used to relax and acclimatize the animal

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5
Q

what is petrissage

A

deep kneeding and squeezing of muscle and surrounding soft tissues

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6
Q

what is cross fiber massage

A

a deep massage concentrated along the lines of restrictive scar tissue and is designed to promote ROM

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7
Q

what is tapotement

A

percussive massage manipulation with a cupped hand

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8
Q

what is screw purchase dependent on?

A

the implant-bone interface… therefore, the goal is to achieve as much contact area as possible

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9
Q

what is the maximum size diameter screw that should be used?

A

use a screw diameter that does not exceed 40% of the diameter of the bone

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10
Q

What drill do you use for a threaded hole for a 1.5 cortical screw?

A

1.1 mm

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11
Q

What drill do you use for a threaded hole for a 2.0 cortical screw?

A

1.5 mm

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12
Q

What drill do you use for a threaded hole for a 2.7 cortical screw?

A

2.0

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13
Q

What drill do you use for a threaded hole for a 3.5 cortical screw?

A

2.5 mm

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14
Q

What drill do you use for a threaded hole for a 4.0 cancellous screw?

A

2.5 mm bit

also does not have a glide hole size

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15
Q

What drill do you use for a threaded hole for a 4.5 cortical screw?

A

3.2 mm

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16
Q

What drill do you use for a threaded hole for a 5.5 cortical screw?

A

4.0

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17
Q

What drill do you use for a threaded hole for a 6.5 cancellous screw?

A

3.2 mm

use a 4.5 bit for the glide hole

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18
Q

why do we countersink lag screws?

A

it will increase the contact between the bone and screw head

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19
Q

when might a shaft screw in lag fashion be appropriate over a screw with threads the whole way?

A

a shaft screw will prevent the threads from becoming engaged in the glide hole on the near cortex. this can occur because an inclined screw will produce axial force and then the force will shift the screw head alone the bone surface towards the fracture - making it easier for the threads to engage the glide hole

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20
Q

which drill sleeve would you use for a DCP plate? For an LC-DCP?

A

use the standard drill sleeve for a DCP

use the universal drill sleeve for an LC-DCP

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21
Q

what is the greatest force that should be applied, dependent on screw size, to tighten a screw? in terms of fingers/hand

A

two finger tight for 2.0 mm screw
three finger tight for 2.7 mm screw
whole hand tight for 3.5 mm screw

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22
Q

why do we apply plate screws at each end of the plate, then close to the fracture, then the remaining plate holes?

A

to ensure axial alignment of the plate to the bone

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23
Q

what size screws do you use with a DCP 4.5 mm plate?

A

4.5 mm cortical or 6.5 mm cancellous

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24
Q

what size screws do you use with a 3.5 DCP plate?

A
  1. 5 mm cortical

4. 0 mm cancellous

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25
Q

In a DCP plate, how much compression is allowed per hole? Dependent on plate size

A

for DCPs 3.5 and 4.5, allows up to 1 mm compression

for DCP 2.7 allows 0.8 mm compression

26
Q

For a DCP plate, how much inclination is possible in the longitudinal and transverse plane?

A

up to 25 degrees in the longitudinal plane

up to 7 degrees in the transverse plane

27
Q

what does it mean for a screw to be eccentrically placed? Which color of the drill guide will allow for it?

A

this is done on the DCP plate to allow for axial compression
use the GOLD collar in the load position
the gold drill guide produces a hole 1.0 mm off center from the fracture

28
Q

Which side of the drill guide do you use for a neutral screw?

A

green places it in neutral

technically, the hole is 0.1 mm off center so it still gives a tiny bit of compression

29
Q

what are the advantages of the LC-DCP plate

A

decreased plate bone contact
even distribution of stiffness
ease of contouring
symmetrical evenly distributed plate holes

30
Q

which drill guide should you use for the LC-DCP?

A

use the universal drill guide

you should also use the universal guide for a DCP in buttress/bridging fashion

31
Q

Are the plate holes of the LC-DCP symmetrical? why or why not?

A

they are symmetrical because this allows for eccentric placement of a screw in either direction and therefore compression for segmental fractures

32
Q

how much inclination in the longitudinal and transverse planes can an LC-DCP allow?

A

40 degrees longitudinally

7 degrees transversely

33
Q

what sizes do veterinary cuttable plates come in? how long are they>

A

they come in a size that can take 1.5 and 2.0 mm as well as a size that accepts 2.0 and 2.7 mm
they are 300 mm long with 50 holes

34
Q

can you stack cuttable plates?

A

yes - you can stack cuttable plates

you should use the plate with the smaller holes or shorter of the two placed superficially

35
Q

what is unique about reconstruction plates?

A

they have deep notches that make them easier to bed and contour
they come in 2.7, 3.5, and 4.5

36
Q

what function is a plate serving when combined with a lag screw through the plate?

A

it is acting as a neutralization plate that is protecting the interfragmentary compression achieved with the lag screw from all rotational, bending, and shearing forces

37
Q

what is the function of a buttress plate? where along the bone is it likely to be used?

A

a buttress plate prevents collapse of a fracture - usually preventing collapse of the adjacent articular surface
to prevent sliding of the plate, the screw hole is placed opposite to the slope in the plate hole

38
Q

what is the function of a bridging plate

A

acts as a splint to maintain the correct length of the bone - prevent axial deformity as the result of shear or bending forces

39
Q

how does a rod aid a plate-rod construct

A

adding an IM pin will reduce the internal plate stress and increase the fatigue life of the plate
the IM pin also reduces the strain concentration at the screw hold to approximately the strain present at the solid center of a similar plate that is not supported by the IM pin

40
Q

what are the elements of an LCP combination hole?

A
  • one half of the hole has the design of the standard DCP/LC-DCP for conventional screws including lag screws
  • the other half of the hole is conical and threaded so that it may accept the matching thread of the new locking screw head
41
Q

what are the two ways an LCP can be applied?

A

as a conventional dynamic compression plate for rigid fixation
or as a pure internal fixator with unicortical locking head screws

42
Q

describe elements of the UniLock system

A
  • available as 2.0 and 2.4 mm - the 2.0 accepts all 2.0 screws. The 2.4 accepts 2.4 and 3.0 mm locking head screws, 2.4 mm non locking cortical screws, 2.7 mm emergency screw
  • never seen anyone use this ever
43
Q

describe elements of the clamp rod internal fixator

A
  • comes in 2.0, 2.7, 3.5
  • affordable and strong
  • never even heard of this one
44
Q

what are positive profile pins? what size do they come in?

A

a positive profile pin has a shaft diameter that is the same its whole length - this reduces the bending stress
they come in 1-6 mm

45
Q

what diameter acrylic or epoxy bar is comparable to a 3.137 mm stainless steel bar?

A

19 mm acrylic or epoxy

46
Q

what size pins should be chosen for an external fixator

A

pin diameter should be no more than 25% of the bone diameter

47
Q

how far away should the pins in an external fixator be?

A

at least two pin diameters from the fragment edge

48
Q

for interlocking nails with the screw or bolt not locked directly in the nail, where should you place the screw/bolt in relation to the fracture

A

because the screw or bolt does not lock directly into the nail, it is best if the hole is located as far away from the fracture site as possible

49
Q

what is the range of sizes that IM (steinmann) pins come in?

A

2-5 mm in diameter

230-300 mm long

50
Q

what is the range of sizes for a K wire?

A

0.8-2.0 mm in diameter

150 mm to 300 mm in length

51
Q

what is the optimal size of IM pin?

A

about 70% of the bone diameter

if combining with a plate, 50% of the bone diameter

52
Q

what is the range of size that orthopedic wire comes in

A

0.5 - 1.5 mm (24-16 gauge)

53
Q

how far apart should cerclage wire be placed?

A

distances between half to the entire bone diameter

54
Q

what is the initial tension and load to loosen for a twist cerclage?

A

70-100 N

260 N to loosen

55
Q

what is the initial tension and load to loosen for a single loop cerclage?

A

150-200 N

260 N to loosen

56
Q

what is the initial tension and load to loosen for a double loop cerclage?

A

300-500 N

666 N to loosen

57
Q

what are the five factors in the pathogenesis of osteomyelitis

A 
tissue ischemia
bacterial inoculation
bone necrosis and sequestration
fracture instability
foreign material implantation

but mainly tissue damage in the presence of bacterial contamination

58
Q

what are the three components of any biolfim?

A

the offending microbe(s)
the microbe produced glycocalyx
host biomaterial interface

59
Q

What makes bacteria resistant to antimicrobial agents when in a biofilm?

A
  1. the biofilm acts as a molecular filter - hard for antimicrobials to perfuse to the target
  2. the microbes enter a quiescent growth pattern in a biolfilm which means they arent reproducing and then the antimicrobials can’t act
  3. the biofilm microenvironment is harsh - low pH, high CO2, low PO2 and hydration - and most antimicrobials are then rendered ineffective
60
Q

what is the most important predisposing factor for refracture following implant removal?

A

open screw holes

it makes them especially weak against torsional forces –> oblique fracture

61
Q

what does the stiffness of an implant depend on?

A

the material itself as well as the design and dimensions of the device

62
Q

Under similar bending condition and cross sections, titanium plates will deform twice as much as a steel plate. Why is that?

A

the steel has a higher (200 GPa) modulus of elasticity than titanium (100 GPa)

Phase 1 (35 decks)

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