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Small Animal Final Year > Principles of fracture management 2 > Flashcards

Principles of fracture management 2 Flashcards

1
Q

Name some different types of screws

A

Cortical/Cancellous

Partially/fully threaded

Self tapping/ non self tapping

Locking / not locking

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2
Q

What is the size of the screw mean?

A

Size of screw = thread diameter

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3
Q

What is the thread of a screw?

A

a helical structure used to convert between rotational and linear movement or force

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4
Q

Name the 3 different types of screws on this image

A

Left - locking

Middle - cortical

Right - cancellous

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5
Q

What is a self tapping screw?

A

A self-tapping screw is a screw that can tap its own hole as it is driven into the material.

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6
Q

What properties does a self tapping screw have?

A

Thread on screw

Cutting flutes at the end of the screw

Cuts thread into bone as screwed in

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7
Q

What properties does a non self tapping screw have?

A

No cutting flutes

Use a tap to cut the thread before placing the screw

Thread of profile of tap = thread profile of screw

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8
Q

What type of screw is this -

Self tapping or non self tapping?

A

Self tapping

It has cutting flutes

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9
Q

What type of screw is this - self tapping or non-self tapping?

A

Non self tapping

Blunt end

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10
Q

Are self tapping or non self tapping screws faster to place?

A

Self tapping - faster to place as do not need to tap before hand to place it

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11
Q

Why should you take care when placing self tapping screws?

A

Care with placement, can fracture bone

If replacing screw, dont make a second thread

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12
Q

Name 3 BONE screws

A

Lag screw

Positional screw

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13
Q

Name some PLATE screws

A

Non locking: for axial compression or neutral (no compression)

Locking

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14
Q

What does a POSITIONAL screw do and how is it placed?

A

Both cortices of the bone are drilled and tapped

Screw holds 2 pieces of bone together i.e. in position

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15
Q

What screw is shown here?

A

Positional screw

both cortices of the bone are drilled and tapped

screw holds 2 pieces of bone together

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16
Q

What are the order of events for placing a 3.5mm positional screw?

A

Placing 3.5mm positional screw

  1. Drill a 2.5mm hole in the cis and trans cortices (using a 2.5mm drill guide)
  2. Measure the depth of the hole using a depth gauge; add 2mm
  3. Use a 3.5mm tap in a 3.5mm guide, tap both cortices Not necessary if screw is self-tapping
  4. Place a 3.5mm screw of the appropriate length
  5. Screw should be tight but do not over-tighten otherwise strips

Counter-sinking is not necessary for a positional screw.

This applies to a positional screw in a bone, or in a plate.

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17
Q

What are lag screws - how are they placed and what do they do?

A

The near cortex if ‘over’ drilled to the same diameter as thread

The far cortex is prepared normally - drill to shaft diameter, tap to thread diameter

Screw compresses/squeezes 2 pieces of bone together

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18
Q

What is this screw, how does it work?

A

Lag screw

Near cortex is over drilled to same diameter as thead

Far cortex is perpared normally

Screw compresses/sqeezes 2 pieces of bone together

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19
Q

When should you use a lag screw?

A

For oblique fracture only

(oblique fracture = more than 3odegrees to long axis. Apply lag screw perpendicular to the fracture, so the squeezing action is to squeeze the fracture rather than to shear the fracture)

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20
Q

How should a lag screw be placed and in what type of fracture?

A

Oblique fractures only

Fracture should be help reduced with bone holding forceps

leg screw at 90degree to fracture line - to compress, otherwise it will shear (which we do not want)

It should lead to primary bone union - lag screws are a way of achieving NO gap and absolute stability in oblique fracture

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21
Q

What are the steps involved with placing a 3.5mm lag screw?

A

How to place 3.5mm lag screw

  1. Drill a 3.5mm glide hole in the cis cortex (drill guide)
  2. Place a 2.5/3.5mm insert sleeve into the glide hole
  3. Drill a 2.5mm hole in the trans cortex
  4. Remove the insert sleeve
  5. Countersink the hole (not if placed through a bone plate)
  6. Measure the depth of the hole using a depth gauge; add 2mm
  7. Using a 3.5mm tap in a 3.5mm guide, tap the trans cortex
  8. Choose a 3.5mm screw of the appropriate length
  9. Place it in the prepared hole and screw it in until tight.
  10. Do not over-tighten the screw
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22
Q

What happens if you tighten a lag screw too tight?

A

If tightened too tight - bone fractures or strip the thread in the far cortex, the bone mini fractures around the screw and then do not have intact break

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23
Q

What are the functions of fully threaded bone screws?

A

Positional screw

Lag screw

Depends on how the ci cortex is prepared - over drill or tap.

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24
Q

What are partially threaded screws used for?

A

There are no near threads - functions exclusively as a LAG screw

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25
Q

What is a non locking plate screw?

A

Screw is placed in the bone through the place

The head of the screw engages the plate

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26
Q

What is this screw here?

A

Non locking plate screw

screw is palced in the bone through the plate

the head of the scew engages the plate

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27
Q

Have you had a break recently?

A

probs not

so got get a tea or lucozade (tred) or a hot choc (anna)

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28
Q

What is a lag screw?

A

A lag screw is used to compress fracture fragments

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29
Q

How can a plate screw be used as a lag screw?

A

Fracture should be reduced

Lag screw should be placed at 90 degrees to the fracture line

  1. fracture should be reduced
  2. plate is applied
  3. lag screw should be placed at 90 degrees to the fracture line
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30
Q

What are some mechanical functions of a plate?

A

Compression

Neutralisation

Bridging

Locking - neutralisation and bridging

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31
Q

What does the size of the plate mean?

A

Size of plate = the size of screws the plate works with

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32
Q

How does a non locking plate work?

A

Screw is placed in the bone through the plate

The head of the screw engages the plate

Screw pulls/tightens plate down onto the bone

friction between plate and bone maintains stability

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33
Q

What 2 things do you need to happen when using a non locking plate?

A

Means 2 things - for contact to happen, screws need to be TIGHT and also need CONTACT between plate and bone - cannot generate friction or equal and opposite forced without these 2 things.

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34
Q

What is non locking plate contouring?

A

Plate - bone friction depends on CONTACT between plate and bone

Plate needs to be contoured

Use bending irons or press

  • can contour the plate to the anatomical shape of the bone that you are applying the shape to
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35
Q

What are the 3 mechanical functions of plates

A
  1. Compression plate
  2. Neutralisation plate
  3. Bridging plate
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36
Q

How does a COMPRESSION plate work?

A

Compression plate - dynamic

Apply AXIAL compression to TRANSVERSE fracture

Aim for primary bone union - contact healing

Achieved using a DYNAMIC COMPRESSION PLATE

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37
Q

What is the most popular plate used?

A

Compression plate

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38
Q

What is the difference between these 2 colours of drill guide and what plate are they used with?

A
  • Green and gold drill guide
  • Green - gives central drill hole
  • Gold - off centre drill hole - allows eccentric, off centre hole or screw in the plate, so as you tighten, the head of the screw will be forced to move down the metal work of the plate in the direction of the fracture and will compress the fracture

Used with a compression plate

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39
Q

What kind of plate can you only apply to a transverse fracture?

A

Can only apply compression plate to transverse fracture

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40
Q

How do you use a dynamic compression plate i.e. how does it work?

A

Dynamic Compression Plate

Oval holes

  • Screw other side of fracture fixed
  • screw inserted eccentrically (away from centre)
    • using GOLD drill guide
    • guide has ARROW showing direction / amount
  • as tightened, head shifted down towards centre
  • pulls bone with it -towards fracture
  • thereby compresses the fracture site
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41
Q

What is show here in this radiograph - what plate is used for what type of fracture?

A

Transverse fracture - dynamic compression plate for axial compression

42
Q

What is a dynamic compression palte neutral screw?

A

Oval holes, neutral screw

  • Screw inserted centrally using green drill guide
  • as tightened, screws pulls plate down onto bone
  • does not move in plate hole
  • does not move the bone

COMPRESSION screws placed first (maximum of 3) THEN neutralisation screws

43
Q

When placing a dynamic compression plate, do you place the compression screws or the neutralisation screws first?

A

COMPRESSION screws palced first (maximum of 3) THEN neutralisation screws

44
Q

What is the maximum number of compression screws that can be placed in a dynamic compression plate?

A

maximum of 3

45
Q

What is a neutralisation plate used for?

A

Something else such as screws or K wires bring the fracture together, but they are not strong enough along to take the forces of weight bearing, so the plate neutralises remaining forces, so patient can weight bare on the bone

46
Q

What is used along side a neutralisaion plate?

A

Neutralisation plate

  • Other implants are used to reconstruct the fracture
    • stabilise it against some forces
    • bone takes some load
  • However, implants not strong enough alone
    • further implants needed
    • to neutralise the remaining forces;
    • implants take remaining load

Load sharing between bone and implants

47
Q

What fractures should you use a neutralisation plate on?

A

Only use neutralisation plates on oblique or spiral fractures usually

48
Q

When is a bridging plate used?

A

Fracture is NOT reconstructed

Bone is unable to take any load i.e. unstable to all forces

The plate must take all of the load

Bridging = spans a fracture gap

49
Q

Which type of plate spans a fracture gap?

A

A bridging plate

50
Q

What is the problem with using a bridging plate and what can you do to prevent or help this?

A

Potential for plate to fail mid section

Use a larger plate or auxillary fixation device e.g. intradeullary pin. need something to strengthen the bridging plate and this usually means using an additional plate or a bigger plate. Plate is weak at resisting bending so could use an IM pin to help it also.

51
Q

What are some negatives associated with plate application?

A

Has a biological cost:

requires dissection

trauma to the none

disruption of soft tissue attachment/bloody supply

52
Q

What are locking plates?

A

Screw head locks into plate

  • implant stability = locking mechanism
  • stability does not depend on bone quality
  • Security of screw no longer dependent on quality of bone
53
Q

If you have poor quality bone, which plate are you best to use?

A

Locking plates where screw head locks into plate hole rather than being dependent on holding into the bone

Does not compress plate onto bone: no periosteal vascular distubrnace and exact contouring not necessary

54
Q

Does locking or non locking internal fixation NOT require accurate contouring?

A

Locking internal fixation does NOT require accurate countouring necessary

55
Q

What are some properties of NON LOCKING plates as an internal fixation:

  1. Friction or no friction?
  2. Accurately contoured?
  3. How tight should screw be?
  4. What does the plate do?
A

Non-locking plate

–Friction between plate & bone

–Plate is accurately contoured

–Screw needs to be tight = close to stripping

–Plate can pull fracture into / out of alignment

56
Q

What are some properties of NON LOCKING plates as an internal fixation:

  1. Friction or no friction?
  2. Accurately contoured?
  3. How tight should screw be?
  4. Any chance of stripping?
  5. What does the plate do?
A

Locking plate

  1. No friction between plate and bone (internal fixator)
  2. Plate is approximately contoured
  3. Screw tightness does not depend on bone thread quality
  4. No chance of screw/thread stripping
  5. Plate holds fracture in alignment / malalignment
57
Q

What can cause plate failure?

A

Plate failure

  • Plates inherently strong and prevent rotation, compression and bending
  • However, will bend if exposed to cyclical loading •if trans-cortex is not intact
  • Non-reconstructed fracture = bridging plate
  • Plate fails generally through a screw hole
  • Screw hole = weakest point / stress concentrator
58
Q

Where is the weakest point on a plate?

A

screw whole = weakest point/stress concentrator

59
Q

How can you avoid plate failure?

A

Having an intact trans cortex or combine with an IM pin to avoid the problem

60
Q

What makes plates weak to bending?

A

Plates are weak against bending if cyclically loaded

61
Q

What is an external skeletal fixator?

A
  • A device that Fixes bones (the Skeleton ) using pins that are inserted into the bone
  • It is External to the skin and bone
  • The frame maintains bone position and consists of:
    • bars
    • clamps / putty / expoxy resin
62
Q

What are some external skeletal fixator frame types?

A

Linear

Circular

Free form (putty / epoxy)

Hybrid

63
Q

What kind of external skeletal fixator is this?

A

Linear ESF

64
Q

What is a linear external skeletal fixator?

A

Longitudinal connecting bars

Clamps

Pins into bone

Many applications

versatile

65
Q

Which type of external skeletal fixator (IA, IB, IIA, IIB, III) is the strongest and which is the weakest?

A
66
Q

What is a type 1A external skeletal fixator?

A
67
Q

What is a type 1B external skeletal fixator?

A
68
Q

What is a type IIB external skeletal fixator?

A
69
Q

What is a type IIA external skeletal fixator?

A
70
Q

What is a type 3 external skeletal fixator?

A
71
Q

What is a circular external skeletal fixator?

A

Thin wire suspended by rings

More versatile

More applications

More complex

More demanding

72
Q

What is a circular external skeletal fixator useful for?

A

Good for complex fracture applications

73
Q

What is this?

A

Circular external skeletal fixator

74
Q

What kind of fixator is this?

A

Free form Epoxy Putty

Clamps and bars replaced by resin or epoxy putty

75
Q

What are some pros and cons of free form epoxy putty external skeletal fixators?

A

Pros:

  • Very adaptable
  • Infinite combinations
  • Bespoe frame

Cons:

  • Messy
  • Cannot adjust post-op
  • Tricky to de-stage
76
Q

Is secondary or primary bone healing faster?

A

Secondary bone healing is much faster than primary

77
Q

Can external skeletal fixators be combined with other things?

A

ESF can be combined with other techniques to overcome their limitations e.g. IM pin tied in ESF

78
Q

What is external skeletal fixator basic application?

A

ESF basic application

  • Many different types of fixator available
  • Pins are designed for the purpose and can have both positive and negative profile
  • Two are placed at either of bone and an external connecting bar is placed
  • Pins are clamped in position whilst examining the limb for length and orientation of the two joints
  • Further pins are placed to strengthen the construct with two close to the fracture
  • Some limited ability to alter alignment after the pins have been placed
79
Q

Label the following image of a bone physis

A
80
Q

What are some considerations of treating fractures in skeletally immature animals

A

Considerations

  • Occur only in immature animals
    • soft bone
    • very rapid healing (3-4 weeks)
  • Cartilage is weaker than bone so fractures first
  • Physis usually shaped to ‘fit together’ –> stable following reduction (except when there is an intra-articular component)
  • Physis is quite wide, and in SH types I and II, fracture line is transverse –> good contact and ability to load share when reduced
  • Occur at ‘ends’ of bones rather than middle, therefore less bending forces act on fracture
  • Able to use smaller, less rigid implants in most cases
81
Q

What should you avoid when treating fractures in skeletally immature animals?

A

Avoid implants that exert compression accross the physis during other respairs

82
Q

What can happens to limbs in skeletally immature animals with fractures?

A

Most of the growth will stop due to the original injury

Limbs may end up shorter than normal if the animal is very young e.g. 4-5 months compared to 8-9 months

Limbs may deviate during growth if damage to growth plate it asymmetrical, or one of a ‘paired’ bone set is damaged

83
Q

What is the Physeal Fracture-Separations Salter-Harris classification (I-V)?

A
84
Q

How can you treat a Salter-Harris type III or IV fracture?

A

Compress with lag screw

85
Q

When does a Salter-Harris Type V occur?

What can it lead to?

Common or rare?

A

Salter-Harris Type V

  • Type 5 occur when the growth plate undergoes compressive damage without separation of the physis
  • This can lead to premature closure of the growth plate and angular limb deformities
  • The conical shaped distal ulna growth plate is particularly prone to this injury

RARE

86
Q

Which Salter-Harris Fracture types are relatively stable when reduced, with resistance to compression and moderatley good resistance to bending and rotation?

A

I and II

87
Q

Which Salter-Harris Fracture types have an articular component and so must be treated with anatomic reduction and alignment, and rigid stabilisation?

A

III and IV

88
Q

Which Salter-Harris Fracture type predominantly invovles the ulna and is likely to result in angular limb deformities due to prevention of synchronous paired bone growth

A
89
Q

What are some specific considerations with regards to articular fractures?

E.g. what will animals develop and what can make this worse? What is the problem with this area for a fracture?

A

Specific considerations:

  • animals will develop traumatic (secondary) osteoathritis
  • any incongruency (step or gap) in articular surfaces will make OA worse
  • articular surfaces are subject to compressive loads

When you repair the fracture, have to get perfect reduction - essential

90
Q

With an articular fraction, what do you NOT want in the joint and why?

A

Do not want callus in the joint as will restrict amd upset joint movement

91
Q

With articular fractures, do you want primary or secondary bone healing?

A

Must be primary bone healing - no callus

92
Q

With an articular fracture, what must the repair facilitate?

A

Repair must facilitate early limb use or will develop joint stiffness and eventual fibrosis with poor range of motion

93
Q

What is an inevitable consequence of an articular fracture?

A

Arthritis

94
Q

What are the 3 golden rules for articular fractures and repair?

A
  1. Accurate anatomic alignment
  2. Rigid internal fixation - compression. So primary bone union = no callus
  3. As rapidly as possible; max 1-5 days
95
Q

What is arthrotomy?

A

An arthrotomy is the creation of an opening in a joint that may be used in drainage

Approaching an articular fracture will usually require an arthrotomy

96
Q

What should you do during an arthrotomy?

A

Need good surgical approach to ensure:

  • adequate visualisation
  • perfect reduction
  • optimal implant placement

Protect cartilage - dab, lavage

Flush joitn throughly before closer

97
Q

How can compression of articular fracture be achieved?

A
  1. Lag screw
  2. Dynamic compression plate
  3. Reduction forceps then
    • position screws
    • +/- locking plate
98
Q

How can you use a lag screw to fix an articular fracture?

A
99
Q

When using a lag screw to fix an articular fracture, what must you add?

A

Must add an anti-rotational K wire (or screw)

Small locking plate = much better stability

100
Q

If perfect reconstruction/compression not possible with an articular fracture, what else can you consider?

A

Arthroplaty e.g. hip replacement

Arthrodesis e.g. pancapral arthrodesis

Amputation as final resort

Small Animal Final Year (317 decks)

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