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Small Animal Surgery > Internal Fracture Fixation (1 of 4) > Flashcards

Internal Fracture Fixation (1 of 4) Flashcards

1
Q

What are the 2 general types of fracture fixation?

A

Non-surgical

Surgical

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2
Q

What is an example of a non-surgical fx fixation?

A

External coaptation

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3
Q

What are 2 examples of surgical fx fixation?

A

External skeletal fixator (ESF)

Internal fracture fixation

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4
Q

What are the 4 main goals of fx fixation?

A

Restore length and alignment
Minimize motion at fx ends
Permit early ambulation and use of as many joints as possible during healing
Balance forces that promote healing with those that promote resorption

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5
Q

What does “alignment” mean with regards to fx fixation?

A

Means alignment of the limb, not the fracture fragments

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6
Q

Why is it important to minimize motion at the fx ends?

A

Rubbing causes bone to wear away

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7
Q

What is Wolff’s law?

A

Bone remodels based on the forces applied

  • Thickens in response to increased force
  • Weakens in response to decreased forces
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8
Q

What are 4 pros of internal fixation?

A

Variety of options
Promotes normal muscle/joint fxn
Fewer re-checks
Nothing externally to monitor

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9
Q

What are 3 cons of internal fixation?

A

Expense
Needs surgeon training
May need second surgery to remove

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10
Q

What are 3 pros to external coaptation?

A

Limited supplies needed
Specialized training is limited
Avoids a prolonged surgical procedure

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11
Q

What are 4 cons to external coaptation?

A

Frequent re-checks and bandage changes
Only for very specific fxs
Risk of bandage morbidity preventing continued use
Immobilized joints

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12
Q

What are 2 main indications for external coaptation?

A

Fx below the knee or elbow

Fx expected to heal rapidly

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13
Q

In addition to being below the knee or elbow, what are 4 more specific indications for the fx to be eligible for external coaptation?

A

Minimally displaced and amenable to reduction
Transverse, simple, closed
Greenstick
Non-articular

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14
Q

What are some things that may hinder fracture healing?

A

Metabolic dz
Steroids
Immunosuppressants

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15
Q

What are the two approaches for internal fixation?

A

Open anatomic reduction/reconstruction (surgical approach)

Biological osteosynthesis

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16
Q

What are 3 qualities of the open anatomic reduction/reconstruction approach?

A

Primary bone healing (

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17
Q

What are 3 qualities of the biological osteosynthesis approach?

A

Avoids disruption of fx hematoma
Less rigid fixation
Secondary healing

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18
Q

What is the desire when using biological osteosynthesis approach?

A

Restore length, alignment and provide support to allow bone to heal

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19
Q

What type of fx is open anatomic reconstruction required for?

A

Articular fractures

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20
Q

What type of fx is open anatomic reconstruction most appropriate for?

A

Repair of transverse, oblique, segmental and minimally comminuted fractures

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21
Q

What are the two kinds of biological osteosynthesis?

A

“Open but do not touch”

“Minimally invasive osteosynthesis”

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22
Q

What is “open but do not touch” biological osteosynthesis?

A

Fx is surgically approached and visualized and the ends are not manipulated

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23
Q

How is the fracture fixed with “open but do not touch” biological osteosynthesis?

A

Fx is reduced via traction of bone away from the fracture with minimal disturbance of the hematoma.

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24
Q

What is “minimally invasive osteosynthesis”?

A

Implants are placed through incisions distant to the fx, fracture is NOT approached

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25
Q

What is the goal of biological osteosynthesis?

A

To return limb alignment and length to normal without disruption of the fx

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26
Q

What are 4 considerations when selecting an implant?

A

Fx type and location
Bone affected
Patient factors
Surgeon preference

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27
Q

What are some patient factors you should consider?

A

Age
Comorbidities
Environment
Size/weight of patient

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28
Q

What is the difference between the implant needs of an older dog vs. a younger dog?

A

Old dogs need something that will be stable longer d/t prolonged healing.
Young dogs need something that will be less stable because they heal fast.

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29
Q

Why do you want a less stable implant for a younger dog?

A

Because if it’s too stable, Wolff’s Law will result in bone resorption.

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30
Q

What is a primary implant?

A

It provides rigid support/stability during healing

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31
Q

What are 3 examples of a primary implant?

A

Bone plates
Interlocking nails
External skeletal fixators

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32
Q

What is a secondary implant?

A

Devices used to help maintain reduction, or strength of the bone while applying the primary implant.

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33
Q

What are 3 examples of a secondary implant?

A

Kirschner wires (K-wire)
Cerclage wire
Interfragmentary screws

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34
Q

What 2 materials can you find plates in?

A

Stainless steel

Titanium

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35
Q

Which plate material is most common?

A

Stainless steel

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36
Q

Which plate material is stiff and fails by bending?

A

Stainless steel

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37
Q

Which plate material is more fatigue resistant?

A

Titanium

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38
Q

Which plate material is less reactive/more biocompatible?

A

Titanium

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39
Q

Which plate material is more expensive?

A

Titanium

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40
Q

What are the 5 most common types of plate?

A 
Dynamic compression plate (DCP)
Limited contact dynamic compression plate (LC-DCP)
Veterinary cuttable plates
Lengthening plates
Reconstruction plates
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41
Q

What is special about the screw holes in a DCP?

A

They allow screw placement that promotes compression of the fx ends

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42
Q

What shape are the screw holes in a DCP and why?

A

They’re oval to allow for angulation

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43
Q

What is important to remember about placing a DCP?

A

Must be right up against the bone or else fixation won’t be as strong.

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44
Q

Describe the plate surfaces on the DCP.

A

They’re all flat

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45
Q

What is different about the shape of the LC-DCP compared to the DCP?

A

LC-DCP has a contoured underside to allow stress to be more evenly distribute across the plate

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46
Q

What is a major difference between the LC-DCP and the DCP?

A

LC-DCP has less contact with the bone for less disruption of periosteal vascularity.

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47
Q

Describe a veterinary cuttable plate.

A

More screw holes
Good for smaller bones
No compression

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48
Q

Does a semi-tubular plate provide compression?

A

No

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49
Q

What is a lengthening plate used for?

A

Highly comminuted fx

50
Q

Does a lengthening plate provide compression?

A

No

51
Q

What is a major weakness in lengthening plates?

A

Love to bend right in the middle

52
Q

What is special about a reconstruction plate?

A

Can be contoured in all 3 directinos

53
Q

What is a reconstruction plate used for?

A

Fx of curved bones

54
Q

What is a locking plate (LCP)

A

A “fixed angle implant” that has threaded locking screw heads.

Think of it like an internal external fixator

55
Q

What makes the LCP better than the DCP?

A

Because the screws lock into the plate, it removes need for plate-bone contact, and instead the stability comes from the screw in the bone and locked to the plate

56
Q

Do you need to contour an LCP?

A

No

57
Q

What patients are the LCPs good for?

A

Old animals and/or really comminuted fractures that will take longer to heal.

58
Q

Can you use an LCP in a puppy?

A

NO! Wolff’s Law

59
Q

What are 2 benefits to the LCP compared to the DCP?

A

LCP needs a greater amount of force to cause implant failure

Pull-out of screws only happens under significantly higher forces

60
Q

What are 3 types of bone that an LCP would be better for.

A

Osteoporotic bone
Soft bone
Comminuted fx

61
Q

What are LCPs excellent for?

A

MIPO (Minimally Invasive Plate Osteosynthesis)

62
Q

What is a cortical screw used for?

A

Diaphyseal bone (dense cortical bone)

63
Q

What is a cancellous screw used for?

A

Softer bone like metaphyseal or epiphyseal bone

64
Q

What is a locking screw used for?

A

When you’re using a locking plate.

NOTE: Wouldn’t really use them otherwise because they’re expensive.

65
Q

What type of thread pattern can you use as a lag screw?

A

Partially threaded

66
Q

What are 4 steps you need to take if you’re not using a slef-tapping screw?

A

Drill, measure, tap, screw

67
Q

What is a cannulated screw, and what is it used for?

A

Center is hollow.

Used for minimally invasive procedures

68
Q

When would you used screws?

A

Can be used with a primary implant, or as a secondary implant

69
Q

What is the goal when using screws?

A

To get as much contact with bone, with a sufficiently stable implant of minimal size

70
Q

What diameter should your screw be?

A

Not exceeding% of the bone diameter in diaphyseal bone

71
Q

What does the screw size refer to?

A

Outer diameter vs. core diameter

72
Q

What does the core diameter of the screw determine?

A

The bending strength

73
Q

What does outer diameter of the screw determine?

A

Pull out strength

74
Q

What are 3 characteristics of a cancellous screw?

A

Increased outer diameter to core diameter ratio
Deeper thread
Larger pitch (gives better purchase in softer bone)

75
Q

What are 3 characteristics of cortical screws?

A

Decreased outer diameter to core diameter
More shallow thread
Decreased pitch

76
Q

How can you tell if a screw is self-tapping?

A

Will have a fluted tip

77
Q

What type of screw has the largest core diameter?

A

Locking screws

78
Q

T/F: Locking screws are also self-tapping.

A

True

79
Q

In a DCP, how do the screws work with the plate?

A

Generates friction between bone and plate necessary for stability of fixation
Loading limb results in shared forces between bone and plate

80
Q

In a LCP, how do the screws work with the plate?

A

Screws lock into the plate converting shear and bending stress into comprehensive forces at the bone-screw interface

81
Q

How do you place a lag screw?

A

Drill a glide hole in the near cortex (threads not engaging here) PERPENDICULAR to the fx, far cortex is drilled to the core for the screw. This creates compression when the screw is tightened.

82
Q

How should a lag screw be places relative to a fracture?

A

PERPENDICULAR

NOTE: Never place a screw through a fx unless it is a lag or positional screw. Otherwise, angle away from the fx.

83
Q

What is a position screw?

A

Holds a fragment in place

84
Q

Does a position screw provide compression?

A

No

85
Q

How strong is a position screw compared to a lag screw?

A

Weaker

86
Q

Can you place lag screws through conventional plate holes?

A

Yes

87
Q

Can you place positional screws through conventional plate holes?

A

Yep!

88
Q

What side of the bone is the plate applied to?

A

The tension side

89
Q

What do you need to do to a conventional plate before you apply it?

A

Precisely contour it to the shape of the bone

90
Q

For a stable repair with a conventional plate, how many screws do you need?

A

Need purchase of at least 6 cortices above and below the fracture

91
Q

What is so nice about locking plates?

A

Minimal to no contouring

92
Q

For a stable repair with a locking plate, how many screws do you need?

A

Need purchase of at least 4 cortices above and below the fracture

93
Q

If not placing a lag or positional screw, what should you do regarding screws near the fracture.

A

Should never be placed through fx, instead angle screws away from fx at least 5mm

94
Q

On what does a plate’s function depend?

A

How it is placed on the bone in relation to the fx.

95
Q

What are the 4 different modes we can use with a plate to repair a fracture?

A

Compression
Neutralization
Buttress
Bridging

96
Q

What is compression mode?

A

When plates are used to achieve compression across the fx ends

97
Q

What 2 types of fx is compression mode used for?

A

Transverse

Short oblique

98
Q

How is compression achieved in compression mode?

A

Eccentrically loaded screws

99
Q

Where is most of the load carried in compression mode?

A

Mostly the bone

100
Q

Why do we like compression mode?

A

Because it may promote primary bone healing

101
Q

What is neutralization mode?

A

Plates are used in addition to primarily placed lag or positional screws

102
Q

Why do we use neutralization mode?

A

The plate acts to protect/neutralize the shearing, bending and rotational forces

103
Q

What is buttress mode?

A

Plate used in metaphyseal fractures to prevent collapse of the adjacent articular surface

104
Q

What does buttress mode frequently incorporate?

A

Lag screws

105
Q

Where is the load carried in buttress mode?

A

The plate is subject to full loading (plate supports cortex and resists displacement)

106
Q

What should be done when using buttress mode?

A

Most or all screw holes should be filled

107
Q

What is bridging mode?

A

Where the plate spans the fractured area which cannot be anatomically reconstructed

108
Q

Where is the load carried in bridging mode?

A

All the weight is carried on the plate at the level of the fracture.

109
Q

In bridging mode there is micro-motion at the fracture site, why can this be a good thing?

A

This is a good thing because it promotes secondary bone healing

110
Q

What size plate would you use for bridging mode?

A

A longer plate with fewer screws

NOTE: Ideally, plate goes from top of bone to the bottom

111
Q

What mode is used in biological osteosynthesis/MIPO (Minimally Invasive Plate Osteosynthesis)?

A

Bridging mode

112
Q

What is elastic plate osteosynthesis?

A

A form of bridging mode that is ONLY appropriate for skeletally immature animals (

113
Q

How do you apply elastic plate osteosynthesis?

A

Long, thin elastic implants with minimal screws placed divergently

114
Q

What are 3 qualities of elastic plate osteosynthesis?

A

Spans the entire bone length and is not contoured
Deforms with axial loading within it’s elastic limit
Spares the bone-screw interface from shear force

115
Q

What is an interlocking nail?

A

Internal fixation that combines the benefits of an intermedullary rod and a plate

116
Q

What is an interlocking nail used for?

A

To treat a diaphyseal comminuted fracture

117
Q

What can you NOT use an interlocking nail for?

A

Radius fracture, the curve of the bone prevents you from placing ANY intermedullary device

118
Q

What are 4 risks of internal fixation?

A

Implant failure
Osteomyelitis
Impingement of nerves
Osteopenia

119
Q

What are 3 types of possible implant failure?

A

Loosening
Breakage
Migration

120
Q

What kind of pins do you commonly see nerve impingement with?

A

Femoral IM pins

121
Q

When might you see osteopenia?

A

When the implants are too strong

Small Animal Surgery (13 decks)

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