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Michaelmas 5th year > Small animal ortho > Flashcards

Small animal ortho Flashcards

1
Q

What does kyphosis mean

A

Dorsal curvature of the spin
True kyphosis = a deformity vs false kyphosis = due to pain

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2
Q

What is scoliosis

A

Lateral curvature of the spine

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3
Q

What is valgus

A

Lateral deviation of the distal portion of the limb

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4
Q

What is varus

A

Medial deviation of the distal portion of the limb

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5
Q

What is palmigrade and platigrade

A

Palmigrade = all parts of manus flat against ground
Plantigrade = all parts of pes flat against ground

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6
Q

What is truncal sway and what might cause it to be increased or decreased

A

= movement of the spine/pelvis when walking
> Increased with hip pain to avoid flexing hip
> Decreased with spinal pain

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7
Q

Signs of thoracic limb lameness

A

Weight shifted caudally **
Head not; down on sound **
Shortened strides
Faster swing phase on sound leg; so shorter stance phase on lame one
May circumduct limbs
Abnormal tracking

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8
Q

Signs of pelvic limb lameness

A

Weight shifted cranially**
Hip hike; increased vertical movement in the lame leg i.e higher on lame side
May bunny hop with hip pain
Increased truncal motion with hip pain
Limb circumduction

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9
Q

How do we grade lameness

A

0 = sound
1= mild; hard to spot
2 = moderate; normal stride length and partial weight bearing
3 = moderate; shortened stride length and partial weight bearing
4 = severe lameness; toe touch weight bearing, minimal use of the limb
5 = non weight bearing lameness

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10
Q

How should weight be distributed between legs (objective gait analysis)

A

Symmetrical
Thoracic limbs take 60% of weight, pelvic limbs take 40%

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11
Q

What markers do osteoblasts express
What about osteoclasts

A

Blasts = ALP, OC
Clasts = TRAP and cathepsin K

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12
Q

What are the two mechanisms of bone development

A

Endochondral ossification
Intramembranous ossification

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13
Q

What is the key difference between endochondrial ossification and intramembranous bone formatino

A

With endochondral ossification, there is a cartilage model made first which is resorbed and replaced with bone –> important in long bone growth and fracture healing

Intramembranous has no chondral elements; important in circumferential bone growth

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14
Q

What is the immature and mature bone structure

A

Immature = woven bone; haphazard connections
Mature = lamellar

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15
Q

What is plexiform bone

A

Special form of bone that is rapidly formed and brick-like
Seen in young, fast growing animals e.g pigs, ruminants, horses and can be remodelled to lamellar bone

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16
Q

Structure of cancellous bone

A

Vertical plates
Horizontal rods so strength in multiple directions

High surface area allows it to be resorbed and formed very quickly to mobilise and store minerals

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17
Q

What type of bone is the spine rich in

A

Cancellous

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18
Q

What are diaphysis, epiphysis, metaphysis

A

Shaft of lone bone = diaphysis
End = epiphysis
Region between the two = metaphysis

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19
Q

Bone turnover cycle

A

Driven by osteoclast action releasing growth factors from bone matrix (e.g TGF-beta)
This causes recruitment of osteoblasts, get osteoid formation, then mineralisation

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20
Q

What is Wolff’s law in bone remodelling

A

Bone struture remodels according to the loads it is exposed to; aligning on lines of principle stress
Loading stimulates net formatino

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21
Q

What are the 3 phases of fracture healing

A

Inflammatory stage = shortest
Repair stage
Remodelling stage = longest

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22
Q

What des comminution of a fracture refer to

A

Degree of fragmentation

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23
Q

What is primary bone healing

A

Bone healing which does not involve callus formation
May be contact or gap healing
- Gap healing = when fragments not in direct contact but within 1mm of each other

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24
Q

Cause of acromegaly

A

Excess growth hormone from the pituitary
= acquired disease; more common in males
get increase in bone formation leading to broad head and large clubbed paws

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25
Q

What is a pituitary dwarf

A

Animal which has a congenital lack of growth hormone

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26
Q

What can excess thyroid hormone lead to in relation to bones

A

Osteoporosis secondary to increased metabolic rate

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27
Q

What are thyroid hormones involved in with bone formatino

A

Cartilge maturation

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28
Q

Stages of endochondral ossification (NB: only get this in long bones)

A

Mesenchyme –> chondroblasts - condrocytes - mineralised scaffold - bone

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29
Q

What is periosteal bone formation

A

Occurs when periosteum is separated from underlying bone and get formation of new bone

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30
Q

What is Marie’s disease

A

Periosteal reaction; hypertrophic osteopathy
Get proliferation of new bone along limb bone diaphyses

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31
Q

What would a growth plate look like on X ray if there had been a failure of mineralisation

A

It would widen; so get a wider radiolucent growth plate

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32
Q

What happens in an angular limb deformity

A

There is premature growth plate closure due to trauma or infection so get differnetial growth rates of bones e.g radius vs ulna

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33
Q

What does osteopaenia mean

A

Thinning of bone so reduced radioopacity
[opposite to osteosclerosis]

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34
Q

What is osteoporosis

A

Deficiency of bone mass due to imbalance between formation and resorption
Get normal bone structure just less of it
- Affects cancellous bone
Bones have thinner trabeculae so are less likely to be able to withstand normal force and can get compression fractures

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35
Q

What is osteomalacia and what are the signs

A

Softening of bones due to failure of mineralisation
Related to a relative deficiency of phosphorus and/or vitamin D

Get bone resorption and accumulatino of unmineralised osteoid on trabecular surfaces

  • Clinical signs: slow onset, shifting lameness, osteophagia, low fertility, hypophosphataemia and anaemia
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36
Q

Why might a dog get osteomalacia

A
  • Low phosphorus from vegetarian diets
  • Low vit D with low UV light level or lactation
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37
Q

What is rickets

A

disease of growing bones where there is failure of mineralisation due to vitD/phosphorus deficiency and physis remains unmineralised and increases in depth

Bones feel thicker because unmineralised osteoid protects the bone ‘beneath’ from actino of osteoclasts so don’t get normal remodelling with age

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38
Q

Clinical rickets signs

A

Curvature and fracture of bones
Enlarged joints
Abnormal teeth alignment due to failure of jaw growth
Spinal deformities
May have epiphyseal separatino

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39
Q

What is osteodystrophia fibrosa

A

Extreme form of osteomalacia due to hyperparathyroidism (primary or secondary)

Get bone removal by osteoclasts and replacmeent with fibrous connective tissue

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40
Q

WHat is rubber jaw a sign of

A

Osteodystrophia fibrosa
Can squeeze canines togehter as jaws have softened

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41
Q

What is nutritional hyperparathyroidism caused by

A

Excess phosphorus and low calcium/vitD
Classic with just meat/offal diets since these have a high P:Ca ratio

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42
Q

How does a fall in plasma Ca:P ratio affect bone resorption

A

This fall stimultes release of PTH by parathyroid glands which stimulates osteoclast action

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43
Q

How can renal failure lead to osteodystrophia fibrosa

A

Via secondary yperparathyroidism

CKD leads to impaired excretion of phosphate so this rises in concentration
And less activated vitamin D gets produed in the kidneys so can’t take as much Ca2+ up from gut

So overal plasma Ca:P falls so get parathyroid gland stimulation to make PTH which activates osteoclasts
Don’t restore balance because normally PTH stimulates phosphate removal from kidney but not possible in chronic renal disease

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44
Q

How does vitamin D poisoning cause osteodytrophy

A

Get deposition of calcium in the wrong spots including artery walls, alveolar walls, kidney, intestinal mucosa

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45
Q

What diet is vitamin A poisoing associated with

A

High liver diet (tends to be cats)

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46
Q

What osteodystrophic changes does vitamin A poisoning cause

A

Promotes osteoblast activity so get more bone deposition so get exostoses i.e new bone formation around joints and foramina from which CNs emerge

Deforming cervical spondylosis

Cartilage damage
OSteoporosis due to stimulating osteoclasts

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47
Q

How does vitamin A deficiency cause osteodystrophy

A

Abnormalities of modelling membranous bones of skull and get too small skull volume and spinal canal
Because osteoclasts are responsive to vitamin A so in defieicny don’t get enough action

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48
Q

What are the 4 As of fracture fixation

A

Apposition = presence/size of fracture gap
Alignment = anatomical positioning of fragments relative to each other
Apparatus = type/size/number/position/function of implants
Activity = biological activity of bone

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49
Q

When would you need a load sharing vs load bearing construct

A
  • Load sharing: for when there is anatomic reconstruction so the bones take some of the load
  • Load bearing: for when bone isn’t taking load e.g with comminuted fractures and bridging fixation
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50
Q

What three factors must a fracture have to use external coaptation only for management

A
  • Minimally displaced
  • Intrinsically stable
  • Rapid healing potential
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51
Q

What issues can prolonged use of external coaptation devices cause

A

Muscle strophy
Contracture; imbalance in tendons in growing animals

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52
Q

How are intramedullary pins useful

A

Gives excellent resistance to bending
- Not good at resisting other forces

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53
Q

When can we use cerclage wire

A

To compress fractures circumferentially
Only use on oblique fractures

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54
Q

When to use pin and tension band wiring

A

For fractures under tension; convert the tensile force to compression force
Used in avulsion fractures

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55
Q

How does a self-tapping screw work

A

Has a cutting blade on the tip which cuts a thread into the bone so no need to use a tap first

56
Q

Difference between cortical screws and cancellous screws

A

Cortical screws have a narrower thread and coarser pitch (more threads)

Cancellous screws have a wider thread and a finer pitch (fewer threads)

57
Q

What is the difference between placing something as a positional screw vs lag screw

A

Positional: just cuts thread in near and far cortex but doesn’t pull the two cortices closer together

Lag: overdrill the hole to make a glide hole on the near cortex so when it tightens in to the near cortex, it pulls them closer together

58
Q

What is a locking screw

A

Screw with a separate thread on the screw head so it works specifically with a locking plate

59
Q

How is an interlocking nail useful

A

Similar to an IM pin; goes down medulla but has holes in it and bolts across to engage with the bone so it can now resist torsion, axial xompression and tensino

60
Q

What are the three modes a bone plate can be used in

A

Compression
Neutralisation
Bridging

61
Q

What do you need for compression plating

A

Plates with specific holes; compression plates
These holes have a shape that guides the screw head towards the fracture so pulls the ends together

62
Q

What does neutralisation plating mean

A

The fracture is first compressed with other implants and then the plate is placed as a load sharing construct

This is useful for oblique/spiral fractures

63
Q

How does bridging plating work

A

The bridge is placed to align above and below the comminuted fragment
- This is load bearing so must be very strong
Doesn’t give any compression

64
Q

Why are locking plates better for bone healing

A

There is an angle stable construct from locking the screw head into the plate
Therefore don’t need to squeeze onto the bone and doesn’t kill the periosteum as with non-locking
So better fracture biology

65
Q

What is the minimum number of screws for locking vs non-locking plates

A

Locking = minimum 4 cortices contained by a screw per fragment; i.e two screws
Non-locking plates = 6 cortices per fragment so 3 screws minimum

66
Q

What is an arthrodesis

A

Where bones are made to fuse by debriding away cartilage, packing with bone graft and fixing together
Joint space fills with bone

67
Q

Difference between direct and indirect reduction

A

Direct fracture involved manipulation of the fractured ends to reduce the fracture
With indirect reduction, the fragments are manipulated from away from the fracture site itself

68
Q

Advantages of closed reduction

A

= not opening fracture site to reduce fracture
Avoids stripping soft tissues from bone so get maintenance of the periosteal blood supply
+ preserves fracture clot

69
Q

Which bones is it easier to do acloser reduction on

A

Those where the bone can be seen more easily through the skin e.g tibia/radiu/ulna
Vs femur which is embedded in lots of muscle

70
Q

How is traction important for indirect reduction

A

TO straighten the bones
Can suspend the limb with some bodyweight to encourage the msucles to stretch

71
Q

Which approach to fracture repair would we use if we wanted to achieve anatomical reconstruction and compression

A

Open reduction with direct technique

72
Q

What are type 1a/1b/2 linear frames

A

1a = all half pins
1b = half pins on two aspects with separate connecting bars
2 = at least some full pins through whole bone

73
Q

When can’t we use type 2 external fixator frames

A

On humerus and femur due to risk of entering a body cavity; use for distal limb only

74
Q

What are circular frames useful for

A

When there is very small amount of space. to put in implants so very thin wires must be used; the circular frame can be used to make the wire very strong

75
Q

When might we use a freeform external fixator

A

Mandibular fractures

76
Q

What type of fractures would we use external fixator frames for

A

Generally communited fractures since this. isa bridging form of fixation

If we want to reconstruct a fracture should do with internal implants and compression

77
Q

Autograft

A

= from the same animal

78
Q

Allograft

A

= from same species but different animal

79
Q

Xenograft

A

= different species

80
Q

What are the three functions of bone grafts

A

Osteoinduction; recruitment of osteogenic cells via cytokines

Osteoconduction: scaffold structure provision for bone to grow onto

Osteogenesis: provision of live cells capable of producing bone

81
Q

Features of autogenous cancellous bone graft

A

= harvested from proximal humerus usually using drill and curette
Good at all 3 Os

82
Q

Features. ofcortical bone fraft

A

Limited biological property so more for mechanical support
e.g where large osteosarcoma is removed in limb sparing surgery

83
Q

Features of freeze dried cancellous bone chips as a graft

A

No cells alive at all so no osteogenesis
Good as a scaffold network (osteoconduction)

84
Q

Features of demineralised bone matrix as a bone graft

A

No live cells so no osteogensis
But proteins are exposed for osteoinduction, also scaffold

85
Q

Features of bone morphogenic protein as bone graft

A

Powerful osteoinduction!!
Can’t do other Os

= cytokines

86
Q

Gustilo-anderson classification of open fractures

A

1 = <1cm wound
2 = >2cm wound but without extensive soft tissue damage
3 = extensive soft tissue damage e.g degloving, avulsions, skin flaps

87
Q

What should we do if soft tissue closure cannot be achieved

A

Go for external fixation and then do open wound management
- no point wasting time on internal implants as high chance of infection

88
Q

When would we swab and culture a fracture wound

A

Only if infected
Otherwise just culture commensals

89
Q

Salter harris types 1-5

A

1 = transverse through growth plate
2 = through growth plate and metaphysis
3 = through growth plate and epiphysis
4 = through growth plate, metaphysis and epiphysis
5 = compression fracture of growth plate

90
Q

What are the two types of forces that might be acting on growth plates

A

Pressure
Tension

Knowing which is acting is important for when fixing it

91
Q

Which bones most commonly get physeal fractures and where on the bone

A

Femur most common; then humerus, tibia; radius

Much more common in distal physis than proximal physis

92
Q

What is the preferable internal fixation device for repairing physeal fractures

A

Smooth K wires
<10% width of the physis

93
Q

How would we fix an avulsion of the tibial crest and what causes it

A

Caused due to tension force of the patellar ligament
Fix using pin and tension band wiring to convert tension force to compression

94
Q

How do. we fix fracture of medial humeral epicondyle

A

Need alignment and compression
Put epicondyle back in place, use K wires to attach it and then a lag screw

95
Q

Why might we use a washer before a lag screw when fixing growth plate fractures and when is it especially important

A

To stop the screw head from counter-sinking into the soft bone
- Especially good for young animals with soft bones

96
Q

Consequences of physeal trauma

A

Fracture
Compression esp at distal ulnar physis
Complete closure will shorten bone
Partial closure; asymmetric shortening can cause angular deformity

97
Q

In the radius and ulna how much do the different growth plates contribute to growth

A

Radius: 40% from proximal one, 60% from distal

Ulna: 15% from proximal growth plate, 85% from distal one

98
Q

Why is the distal ulnar physis particularly sensitive to trauma

A

Because the physis is conical rather than plate

99
Q

Which dogs is early cessation of ulnar growth normal

A

Chondrodystrophic breeds eg basset hounds, daschunds

100
Q

What result comes from early distal ulnar GP cllosure

A

Radius curvus since radius continues growing which ulna acts as a bowstring

Manifestation = carpal valgus

101
Q

Which dogs are more prone to traumatising distal ulnar GP

A

Large breeds

102
Q

Primary bone tumour types

A

Osteosarcoma = makes bone

Myeloma, lymphoma and chondrosarcoma don’t

103
Q

Secondary bone tumour types

A

Squamous cell carcinoma via local invasion to bone

ANy metastatic tumour

104
Q

What is the most common canine malignant bone tumour

A

Osteosarcoma
Accounts for 90% of cases

105
Q

Which bones are more commonly affected by osteosarcomas

A

Mostly appendicular skeleton esp distal radius the most, prox humerus prox tibia

24% axial skeleton
Very small amount 1% from soft tissue

106
Q

Do osteosarcomas cross joint surfaces

A

No - they stay in original bone

107
Q

X ray characteristics of osteosarcoma

A

Mottling of bone structure
Less clear metaphysis
Fuzzy edge of bone with some elevation from bone

Mixture of osteolysis and irregular new bone formation

108
Q

How do we diagnose an osteosarcoma

A

This is a histological diagnosis so need biopsy

109
Q

What are the histological hallmakrs of osteosarcoma

A

Osteoblasts (oval cells) producing osteoid (pink)

110
Q

Characteristics of osteosarcoma spread

A

Highly metastatic; happens early in disease i.e before presentation

Haematogenous spread; first to lungs; then other organs

Less metastatic in cats; less metastatic from axial skeleton

111
Q

What are the two common tumours of joints in dogs and how is the prognosis different

A
  • Synovial sarcoma; much more favourable prognosis
  • Histiocytic sarcoma
112
Q

What are the 3 major components of fracture assessment

A

Biological i.e how well will it heal

Mechanical i.e can it be reconstructed vs needing bridging

Clinical factors e.g patient and client compliance and confort level

113
Q

What is the goal in articular fracture surgery

A

To slow and minimise degenerative change i.e arthritis progression

114
Q

What are the principles of articular fracture repair

A
  • Perfect reduction of articular surface
  • Rigid internal fixation
  • Interfragmentary compression of fracture gap
  • Early mobilisation and use of joint
115
Q

What are avulsion fractures

A

Where there is detachment of bone fragment at the origin/insertion of a tendon or ligament

Especially happens where arge muscle groups go onto a bone near a weak point

116
Q

Principle of avulsion fracture repair

A

Implants must resist the original tensile force
Convert distracting forces into compression using tension band principle

117
Q

Which side should a plate be places on - tension or compression side?

A

Tension side

118
Q

Where do humoral fractures typically occur and how do we manage them

A

On distal 1/3 of bone
Use plate fixation
DO NOT USE CASTS

Tension side is craniolateral but much easier to fit the plate on the medial surface since this is flatter

119
Q

Where do radius/ulna fractures typically occur and how can we manage them

A

At distal diaphyses; esp in toy breeds

Best is plate and screw repair

Could do external fixation
External coaptation could only be used for simple transverse fractures with stability and good aposition

120
Q

What complication in fracture repair is common in toy breeds and so what approach should we take

A

Prone to atrophic non-union due to poor fracture biology

Do open fracture reduction and internal fixation

121
Q

How do we deal with femoral fractures

A

Go for internal fixation
Tension side is lateral which has good surgical access

Avoid external fixation due to large muscle mass (may have to use if can’t reconstruct fracture)

122
Q

Where is tension side on humerus, femur, tibia

A

Humerus = cranial/lateral
Femur = lateral
Tibia = medial

123
Q

What to remember about presentation of tibial tuberosity avulsion fractures

A

May present with very mild lameness - need to X ray

124
Q

How many pins/fragment is mimumum for external skeletal fixator and how thick should the pins be

A

Minimum 3 pins per fragment, ideally 4
Pins should be 20% bone diameter

125
Q

Which specific ortho exam test must be done conscious

A

Patella luxation since grade changes dependent on muscle tone

126
Q

Which ortho exam tests can only be done on sedated or GA patients

A

Ortalana test of hip laxity
Barden’s lip lift
Thumb displacement test for hip luxatino

127
Q

What is an abnormal amount for thumb to lift in barden’s lip lift test

A

> 5mm; suggests hip laxity

128
Q

Does a larger or smaller angle of reduction on ortolani test for hip laxity suggest wrose laxity

A

LArger angle (that legs are abducted before get reduction into place) = more severe

129
Q

What medium do we use for culturing joint fluid

A

Bone meat broth

130
Q

Where do we feel for effusions in stifle

A

Behind patella lig

131
Q

Where do we feel for effusions in elbow

A

Caudlly for bulge between olecranon and lateral epicondyle

132
Q

Where do we feel for joint effusion at carpus

A

Cranially; get lack of definition of carpal bones

133
Q

Where do we feel for effusion at the hock

A

Cranialy and caudally

134
Q

What does indirect trauma mean in terms of causing a frature

A

Wasn’t the actual trauma that caused the fracture but the impact from it
e.g jumping on the floor, getting force travelling up limb and causing fracture at a weak point

135
Q
A

Michaelmas 5th year (41 decks)

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