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LEAH FCP > Small animal fracture repair > Flashcards

Small animal fracture repair Flashcards

1
Q

What are orthogonal radiographs?

A

Radiographs taken at right angle to each other

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2
Q

What is a fracture score

A

Numerical value given to fracture to determine how difficult fracture repair will be based on biological & non-biological factors

The higher the score the more demanding the fracture will be to repair

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3
Q

What are patient factors to consider when fracture scoring

A

weight of animal
- heavier = higher score

age
- younger = lower score

boisterousness & ability to manage cage rest

concurrent illnesses

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4
Q

What are fracture factors to consider when fracture scoring

A

type of fracture
- does it allow compression plating or require external fixator?

open or closed?

associated with soft tissue injuries

single or one of several fractures?

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5
Q

What are owner factors to consider when fracture scoring

A

will they comply with post-op instructions?

finances

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6
Q

What are surgeon factors to consider when fracture scoring

A

are they able to manage this fracture?

is the correct equipment available?

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7
Q

what are the normal forces on a long bone due to weight bearing and muscle contraction

A

Bending
Torsion
Tension
Axial compression

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8
Q

Name the forces acting on this bone

A
  1. axial compression
  2. tension
  3. bending (when weight bearing, leg placed at angle to ground or asymmetrical muscle contraction)
  4. torsion (when body changes direction with leg planted on ground)
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9
Q

why is it important to consider tension & compression aspects of the long bone in certain fracture types?

A

All diaphyseal bones are asymmetrically loaded when weight bearing

The mandible is also asymmetrically loaded during mastication

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10
Q

Which side should a plate be applied to?

A

Tension side as it will not be broken by tensile forces but will be by successive compressions

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11
Q

What are the tension aspects of the femur, tibia, radius, humerus & mandible

A
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12
Q

What are the consequences of axial compression on fractures?

A

good if fracture is transverse (at right angle to long bone) or if fracture interdigitates

if not the compression of a comminuted (multiple fragments) or oblique fracture causes fracture to collapse or shear

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13
Q

What are the consequences of tension on fractures?

A

tension produced by ligaments or tendons pulling on one of the bone fragments causes fracture to be distracted & needs to be overcome with lag screwing or tension bands

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14
Q

What are the consequences of torsion on fractures?

A

results in rotation of fracture site

requires management with plates, external fixator or interlocking nail

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15
Q

What are the consequences of bending on fractures?

A

occurs due to asymmetrical nature of bone loading

pin in centre of medullary cavity is best suited at counteracting this force

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16
Q

When does primary bone healing occur

A

when there is bone to bone healing

requires intimate contact of bone ends (preferably under compression)
- requires application of bone plate & extensive dissection & manipulation of soft tissue

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17
Q

When does secondary bone healing occur

A

When there is intervening callus formation

Doesn’t require accurate reduction of fracture

18
Q

What is strain in bone healing

A

teh change in length over the original length of the fracture

if there is a small gap & much movement then strain is high & fracture fails to heal as tissue ruptures

to reduce strain the gap can be widened
- bone ends resorb or
- fracture becomes progressively stiffer by formation of granulation tissue, callus & bone

19
Q

What is the purpose of post-operative radiographs after fracture repair

A

used to assess:
- alignment of fracture
- positioning of implants
- encroachment of implants into joints or soft tissues or bridging of growth plates in young animals

20
Q

In what situations should radiographic assessment be made after a fracture repair?

A

prior to removal of implants

if progression is not as anticipated

there is evidence of sepsis

21
Q

What are common options for fracture repairs

A

intramedullary pin & cerclage wire

plating (+/- compression)

intramedullary nail

external fixator

pin & tension band

combination

22
Q

Describe the intramedullary pin

A

good at counteracting bending forces as it lies in centre of bone

poor at axial compression unless bone column reinstated
- generally reformed with aid of cerclage wires

increase in pin diameter results in disproportionate increase in strength

cerclage wires draw fragments to their normal position & fix them relying on circular cross-section of bone to produce stability

if fracture is transverse (at right angle to long axis of bone) then rotation is possible
- doesn’t occur with oblique fracture
- to prevent rotation plate can be used in addition to pin (plate rod combination) or external fixator

23
Q

Describe the normograde placement of an IM pin

A

pin is placed from proximal end of proximal fragment

small skin incision is made & pin seated into bone

once pin is positioned in medullary cavity & advanced to just proximal to fracture site, the fracture is reduced

then pin is pushed into distal fragment

24
Q

Describe retrograde placement of an IM pin

A

Pin enters proximal fragment distally (from fracture site)

leaves proximal bone fragment & small wound is made in skin & pin is pushed through

Pin then redirected and driven into distal fragment & fracture is reduced

25
Q

What kind of repair has been done here

A

Tibial fracture repaired by IM pin & multiple cerclage wires

26
Q

What is the function of an external fixator in a transverse fracture?

A

Prevents rotation & offers some resistance to axial compression

27
Q

What kind of repair has been done here

A

Transverse humeral fracture repaired with IM pin & external fixator

28
Q

Describe the intramedullary interlocking nail

A

requires special jigs to ensure screws enter nail

prevent rotation and bending

can only be used in straight bones (e.g., tibia and femur)

not used commonly

29
Q

Describe the external fixator

A

repairs fracture with series of pins placed through skin & connected to connecting bar

pins attached to bar with clamps or epoxyresin

versatile repair & counteracts all forces applied to fracture (esp. if in combination with IM pin)

good for open fractures where open wound management may be required

30
Q

What are some complications of external fixators

A

pins prone to infection

may be discharge (esp. when pins pass through large muscle mass)

require frequent examination & may require re-application of loose pins

may require staging down (removing few pins to change load bearing from fixator to bone)

several follow up radiographs may be necessary

31
Q

Describe plate fixation

A

allow reconstruction of comminuted (multi-fragmented fractures

protect against axial and rotational forces (less good at bending as not positioned along central axis)

can be locking or non-locking

32
Q

Describe locking vs non-locking plate fixation

A

non-locking:
- require plate to adhere to screws & bone by friction

locking:
- has thread in plate where screws engage as well as in bone
- diameter of screws in plate greater than screws in bone
- special guides required to align screw with thread of plate

33
Q

What is a buttress plate

A

has strong central section that bridges a comminuted section of fracture

plate takes all the load

34
Q

what is a neutrilisation plate

A

allows reconstruction of the fracture & acts as a scaffold, taking some of the load, the rest is taken by the reconstructed bone

35
Q

what is a compression plate

A

compresses fracture by making use of eccentrically placed screws in oval screw hole

screw starts at top of slope & when tightened moves down slope & shifts the one fragment towards the fracture (hence compressing it)

the bone takes all the load

36
Q

What is cyclical loading

A

Repeated application of stress on plate over time, which can lead to fatigue & eventual failure if load is unevenly distributed or exceeds plate’s threshold

37
Q

What is the primary cause of plate failure & how can it be mitigated in the humerus, femur & tibia?

A

Trans cortex is incomplete, which, combined with absence of section of ulna, exposes plate to cyclical loading & failure.

In humerus, femur & tibia, this bending tendency can be managed using:
- IM pin
- Rod plate combination

38
Q

What are avulsion or tension fractures & give examples?

A

fractures produced by distractive forced generated internally

as a result they are exposed to distractive forces during healing

larger fragments can be repaired by placing screw & compressing it using lagging technique

alternatively distractive forces can be converted into compressive forces using a tension band

examples:
- tibial tuberosity distracted by quadriceps
- olecranon distracted by triceps
- greater trochanter by gluteal muscles (image)

39
Q

Describe lag screws

A

with lag screw compression can be applied to fracture

near hole is over drilled to have same diameter as thread so it doesn’t grip

when screw is tightened it pulls far fragment against near

used to produce rigid fixation & counteract distractive forces

40
Q

Describe tension bands

A

fracture is reduced (aligned & then 2 pins used to fix it in position)

figure of 8 wire is applied opposite distractive force & 2 arms are tightened

with wire tightened & pulling in opposite direction to distractive force it results in compressive force applied to fracture

41
Q

What are some things to consider when dealing with avian fractures

A

pneumatised bone with periosteal blood supply must be preserved during fracture repair

avian bone is brittle & more prone to splintering

avian bone heals primarily from endosteum

healing is rapid

anatomical abnormalities due to flight adaptations
- e.g. keep, coracoids & synsacrum

primary wing feathers originate in periosteum of ulna & tail feathers in pygostyle

fractures involving joint or within 10mm have poor prognosis

due to thin & brittle bones, IM pins & external fixators are used rather than plates

42
Q

What is going on here

A

humeral fracture repaired with IM pin tied into uniplanar external fixator

clamps replaced with epoxyresin to reduce weight of device

LEAH FCP (49 decks)

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