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Ortho > Fixation Constructs > Flashcards

Fixation Constructs Flashcards

1
Q

Which forces are neutralized by a cast?

A
  • Bending and a little rotational
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2
Q

Which forces are neutralized by an IM pin?

A
  • Bending

- Can still have a lot of compression and torsion on a transverse or short oblique

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3
Q

Which forces are neutralized by cerclage wire?

A
  • Torsion or rotation

- Must be on a long oblique fracture

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4
Q

Which forces are neutralized by a plate?

A
  • Bending, compression, and rotation
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5
Q

Which forces are neutralized by an external fixator

A
  • Bending, compression, and rotation
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6
Q

Which forces are neutralized by an interlocking nail?

A
  • Bending, compression, and rotation
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7
Q

What factors can a surgeon not control?

A
  • Age
  • Character of the fracture
  • State of the soft tissues
  • Systemic or local bone disease
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8
Q

What factors can a surgeon control?

A
  • Tissue handling
  • Asepsis
  • Poor reduction
  • Inadequate immobilization
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9
Q

What does a high fracture score indicate?

A
  • Fracture that would allow for immediate load sharing and enhanced healing
    e. g. long oblique fracture of the tibia in a healthy 9 week old puppy
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10
Q

Moderate fracture score

A
  • Older dog with a transverse fracture
  • Load sharing; healing still delayed
  • Young dog with a non-reducible fracture
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11
Q

Low fracture score?

A
  • Generally non-reducible old fractures in older dogs
  • Compromised healing
  • Fracture must be very rigid
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12
Q

How long do most low fracture scores have to be maintained?

A
  • 6 weeks or more of VERY rigid construct
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13
Q

What fixation methods neutralize all fracture forces?

A
  • Interlocking nail
  • External skeletal fixator
  • Plate
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14
Q

When to use closed reduction?

A
  • Cast or external skeletal fixator

- Pros are minimize surgery time, reduce chance of infection, enhance healing, preserve blood supply

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15
Q

When to use open reduction

A
  • Articular fracture

- Comminuted non-reducible fracture of long bone (that’s open)

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16
Q

When to use definitive stabilization?

A
  • Minimally displaced fracture with bending forces
  • Neutralize bending forces (cast)
  • Neutralize rotational forces (joint above and below)
  • Axial compression means fracture configuration must be able to withstand the load
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17
Q

Pros of definitive stabilization

A
  • Inexpensive
  • Noninvasive
  • Doesn’t require a lot of equipment
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18
Q

Cons of definitive stabilization

A
  • Not a lot of motion - will have some muscle atrophy
  • May lose some ROM of the joint above and below
  • Not overly rigid, which may delay healing
  • Difficult with wound management
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19
Q

Post-operative cast care

A
  • Evaluate in 24 hours and then in 7-10 days
  • Change if there is a foul smell, if the dog stops using their limb or changes how they are using it, if it has a foul odor
  • Monitor toes and monitor for pressure sores
  • Young dogs may need a new cast every 1-2 weeks
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20
Q

Advantages of external skeletal fixator

A
  • Rigid fixation with minimal invasion
  • Adjustable and versatile
  • leaves wounds accessible
  • Can maintain limb length
  • Gradual increase in load bearing
  • Minimal inventory, minimal instrumentation
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21
Q

Indications for external fixation

A
  • 1° fracture fixation
  • Adjunct stabilization
  • Corrective osteotomy
  • Limb lengthening
  • Open and infected fractures
  • Transarticular stabilization
  • Delayed or non-union
  • Avian fracture
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22
Q

Instruments for external fixation

A
  • Smooth or threaded pins
  • Connecting bars
  • Clamps
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23
Q

Know the different types of external skeletal fixators

A
  • just know them
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24
Q

What is a tie-in?

A
  • Aid in reduction
  • Control bending
  • Use on humeral and femoral fractures as it’s hard to get pins proximally
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25
Q

What ancillary stabilization tactics can be used?

A
  • Add IM pin
  • Add cerclage wire
  • Add screws
  • Can also do more connecting bars
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26
Q

Diameter of pins in ESF

A
  • 25%
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27
Q

What must you remember with caring for ESF?

A
  • Don’t forget the owner
  • Carefully discuss aftercare
  • Post-op full bandage
  • Then a bumper bandage 3-4 days post-op
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28
Q

Circular fixator - when to use?

A
  • With short just-articular bone fragments
  • Uses wires, so takes up less space
  • Can apply to radius, tibia, humerus, and femur
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29
Q

Pros of external fixation

A
  • versatile
  • Cheap
  • Non-reconstructable
  • Closed reduction or minimal approach
  • Wound management
  • No permanent implants
  • Dynamization (staged disassembly)
  • Allows early limb use)
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30
Q

What can you use to replace the whole connecting bar?

A
  • Epoxy resin or methyl methacrylate

- Replace clamps or connecting bar

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31
Q

What type of pins do you use with a free-form ESF?

A
  • Threaded pins
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32
Q

Factors that affect bone healing?

A
  • Age
  • Fracture location
  • Cell response
  • Circulation
  • Concurrent soft tissue
  • Stability of the bone segment
  • Aseptic technique
  • Activity of the patient
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33
Q

What is the normal blood supply to the long bone?

A
  • Nutrient artery
  • Proximal and distal metaphyseal arteries
  • Periosteal arteries
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34
Q

What direction is normal blood flow to the bone?

A
  • Centrifugal

- medullary canal to periosteum

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35
Q

What direction is fracture blood flow?

A
  • Centripetal

- From surrounding soft tissue

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36
Q

What happens to blood supply during fracture?

A
  • Centripetal (from surrounding tissue)
  • Medullary tissue is disrupted
  • metaphyseal vessels enhanced
  • Extraosseous vasculature
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37
Q

Which reduction will have the least effect on blood supply?

A
  • Closed reduction
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38
Q

Which types of reduction are most biologic?

A
  • Closed reduction with cast or external fixation are most biologic
  • Rapid callus formation
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39
Q

When is fracture healing evaluated?

A
  • 2-8 weeks post op in puppies
  • Otherwise probably 4-6 weeks initially
  • 12, 10, or 16 weeks post op
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40
Q

What is strain?

A
  • Ratio between ∆ in gap width to total gap width

- See the slide for an example of how to calculate it

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41
Q

Does strain increase/decrease with increasing fracture rigidity?

A
  • Decreases
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42
Q

Do tissues become more or less tolerant of strain as a fracture heals?

A
  • Less tolerant!
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43
Q

Indirect bone healing

A
  • callus formation

- Fibrous connective tissue and cartilage callus

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44
Q

Direct bone healing

A
  • Rigid fixation
  • Contact healing with direct Haversian canal remodeling
  • Gap healing of 150-300 µm
  • Initial fibrous bone replaced by longitudinal reconstruction of fracture sites
  • Cutting cones with osteoclasts, capillary buds, and osteoblasts
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45
Q

Intramembranous bone healing

A
  • type of direct bone healing
  • Differentiation of mesenchymal cells into osteoblasts
  • Can occur with up to 5% strain
  • Bone deposited on bone away from fracture site
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46
Q

What cell type differentiates into osteoblasts with intramembranous bone healing?

A
  • Mesenchymal cells differentiate into osteoblasts

- Combination of direct and indirect bone healing

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47
Q

What % strain can occur with intramembranous healing?

A
  • 5% strain
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48
Q

What are bone grafts used for?

A
  • Enhance bone healing for fracture repair and arthrodesis
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49
Q

What do bone grafts provide?

A
  • mesenchymal stem cells, osteoblasts, growth factors, bone for scaffold
50
Q

Osteogenesis

A
  • New bone development and support

- Osteoblasts

51
Q

Example of a graft that allows for osteogenesis

A

Cancellous autograft

52
Q

Osteoinduction

A
  • Induces differentiation of mesenchymal cells into osteoblasts
53
Q

Osteoinduction example

A

Demineralized bone matrix

54
Q

Osteoconduction

A
  • Acts as a scaffold for host bone
55
Q

Example of osteoconduction

A
  • Cortical allograft
56
Q

Osteointegration

A
  • Surface bonding between graft and host bone
57
Q

Where can you get autogenous cancellous bone?

A
  • Proximal humerus
  • Proximal tibia
  • Ilium
58
Q

Cancellous autograft properties of osteogenesis, osteoinduction, and osteoconduction

A
  • Great for all three
59
Q

Radiographic union

A
  • Point at which healing has progressed to the point where there is evidence of bone bridging of all fracture lines in all views
60
Q

Clinical union

A
  • Point at which healing has progressed ot the point in strength that the fixation can be removed
61
Q

How long can clinical union take to occur for ESF and IM pin fixations varying on age?

<3 months
3-6 months
6-12 months
>1 year

A
  1. <3 months: 2-3 weeks
  2. 3-6 months: 4-6 weeks
  3. 6-12 months: 5-8 weeks
  4. > 1 year: 7-12 weeks
62
Q

How long can direct healing take to occur?

<3 months
3-6 months
6-12 months
>1 year

A
  1. <3 months: 4 weeks
  2. 3-6 months: 2-3 months
  3. 6-12 months: 3-5 months
  4. > 12 months: 5 months to 1 year
63
Q

Delayed union

A
  • Fractures that heal more slowly than anticipated

- Progressive signs of bone activity visible on radiographs

64
Q

What is the #1 cause of delayed union?

A
  • Lack of stability
65
Q

Other reasons for delayed union?

A
  • Clinical status of the patient
  • nature of the trauma
  • High energy fracture, soft tissue trauma, open?
  • Poor decision making in fracture management
  • Too rigid, unstable, large fracture gap, radiation therapy
  • Drugs: steroids, NSAIDs
66
Q

Nonunion?

A
  • Arrested fracture repair process
67
Q

What must happen to ensure healing with a nonunion?

A
  • Surgical intervention!
68
Q

What usually leads to nonunion?

A
  • Poor decision making and technical failure on the part of the surgeon
  • Instability at the site of the fracture if the most common reason for a non-union
69
Q

Vascular non-union

A
  • Lucent line through fracture site

- Some fibrous tissue but cannot move on

70
Q

Hypertrophic nonunion

A
  • Lots of bony proliferation

- Large amounts of non-bridging callus

71
Q

Treatment for hypertrophic nonunion

A
  • Debridement, grafting, and stabilization
72
Q

Atrophic nonunion

A
  • Biologically inactive pseudoarthrosis

- No evidence of bone reaction at the fracture ends, and the bone ends appear sclerotic

73
Q

Malunion

A
  • Healed fractures in which anatomic bone alignment is not achieved or maintained during healing
  • Deleterious effect on function
  • Can cause arthritis of the affected joint due to malalignment and joint incongruity
  • Require a corrective osteotomy
  • Likely need a referal
74
Q

Osteomyelitis definition

A
  • Inflammatory condition of bone and medullary canal
  • Bacterial or fungal (rarely fungal)
  • Acute hematogenous vs post-traumatic
75
Q

What are most post-traumatic osteomyelitis due to?

A
  • Bacterial infection

- Biofilm (bacteria, glycocalyx, and implant surface)

76
Q

What does a biofilm do?

A
  • Protects bacteria from antimicrobials and host defenses
77
Q

Clinical signs of osteomyelitis

A
  • Pain, tenderness, swelling, erythema (acute)

- Drainage (chronic)

78
Q

Lab findings for osteomyelitis

A
  • NSF on lab work
79
Q

What steps to take for diagnosing osteomyelitis?

A
  • Culture and sensitivity prior to antibiotics (deep aspiration with syringe and culture)
  • Radiographs: varies with stage of disease (may show periosteal reaction and sequestrum)

-

80
Q

Treatment for osteomyelitis?

A
  • Debride necrotic bone to get back to healthy bleeding bone
  • Establish drainage
  • Re-stabilize
  • Antibiotics based on culture for 4-6 weeks
  • Likely worth re-culturing
81
Q

What to do with implants if there is evidence of osteomyelitis?

A
  • If implants are stable, leave in place until the fracture heals
  • Infection will not clear until implants are removed
  • If the fracture is unstable, stabilize or remove and replace (can add an external fixator above and below)
82
Q

Indications for implant removal?

A
  • Clinical union (often fine to leave them in)
  • Radiographic union
  • Growing animal or open physis
  • Interference with function
  • Pain
  • Unstable or loose implants
  • Infection itself isn’t an indication for implant removal, but if infection is present once healing has occurred, it does need to be removed
83
Q

Causes of pathologic fractures

A
  • Neoplasia
  • Osteomyelitis
  • Bone cyst
  • Radiation therapy
84
Q

Radiographic features of pathologic fractures

A
  • Lytic and/or proliferative bone (cancer typically has both)
  • Periosteal reaction
  • Soft tissue mass
85
Q

Quadriceps contracture or tie-down

A
  • Unstable fracture in a young dog
86
Q

Sciatic nerve entrapment

A
  • Not uncommon with pinning a femur

- Avoid by placing the pin normograde if possible

87
Q

Goals for internal fixation

A
  • Adequate reduction
  • Rigid fixation
  • Early active motion
  • Early weight bearing
88
Q

Atraumatic surgery

A
  • goal to preserve function
  • Maintain blood supply
  • Decrease incidence of infection
  • Minimize invasion of soft tissue
89
Q

Implant characteristics

A
  • Biocompatibility
  • Resist corrosion
  • Same alloy to prevent corrosion when implants are mixed
  • 316L stainless steel
  • Never reuse
90
Q

Plate screw

A
  • Anchor a plate to bone
91
Q

Position screw

A
  • Hold bone fragments in anatomic position
92
Q

Lag screw or compression screw

A
  • Compresses two bone fragments
93
Q

Drill bit - what does it correspond to?

A
  • Corresponds to the inner shaft
94
Q

Tap - what does it correspond to?

A
  • Corresponds to the threads of the screw
95
Q

Steps for lag screw fixation

A
  • Overdrill the near cortex
  • Drill the far cortex
  • Countersink
  • Measure depth
  • Tap the far cortex
  • Screw slides through the near cortex
  • Pulls far cortex into compression
96
Q

What determines plate length?

A
  • Number of screw holes
97
Q

What determines plate size?

A
  • Cortical screw that the plate hole will accept
98
Q

Plate hole configurations

A
  • Veterinary cuttable plate

- Oblong hole

99
Q

Limited- contact dynamic compression plate

A
  • Tapered edge

- Trying to minimize contact with periosteum

100
Q

Plate configuration

A
  • Narrow, broad, standard
101
Q

What can dynamic compression plates combat?

A
  • Compression
  • Neutralization
  • Buttress
102
Q

How to compress using a dynamic compression plate?

A
  • Drill off center
103
Q

Concepts for applying bone plates

A
  • Select appropriate plate size
  • Select a plate that spans the bone length for diaphyseal fractures (70% of bone)
  • Accurately contour for a non-locking plate
104
Q

How many cortices should be spanned with a plate?

A
  • Minimum three screws or six cortices above and below the fracture
105
Q

Advantages of locking plates

A
  • Screw head locks into the plate, allowing the plate and screw to act as a single unit
  • Locking mechanism provides fracture fixation
  • No contouring
  • Neutral position
  • Increase construct yield strength
106
Q

Concepts for locking plates

A
  • Plate contouring not critical
  • Locking screws must be perpendicular to the plate
  • Reduce fracture before tightening
  • Longer plate with fewer screws is best
107
Q

What type of fractures can get a tape muzzle?

A
  • Minimally displaced
  • caudal fractures
  • Comminuted fractures
108
Q

What type of fractures can get dental bonding?

A
  • malocclusion
  • Caudal fractures
  • Comminuted fractures
109
Q

What else can be used for mandibular or maxillary fractures?

A
  • Stroud wiring (etching with wire placed around the teeth

- Symphyseal wiring

110
Q

Scapular fracture classification

A
  • Stable extra-articular (body)
  • Unstable extra-articular (body or neck)
  • Intra-articular (glenoid)
111
Q

When is fixation indicated for scapular fractures?

A
  • Unstable, extra-articular and intra-articular classifications
  • Generally for scapular neck and glenoid fractures
112
Q

Scapular fractures - what will happen if can’t do surgical management?

A
  • Most will heal
113
Q

Indications for pelvic fracture stabilization

A
  • Weight bearing (acetabulum, ilium, sacroiliac joint)
  • Articular fractures (acetabulum)
  • Pelvic inlet narrowing
  • Contralateral injury
  • Uncontrollable pain (may be a sacral wing fracture)
114
Q

Ilial body fractures

A
  • can heal with two lag screws
  • 2 k wires and hemi-cerclage
  • plates
115
Q

Sacroiliac luxation - when to repair?

A
  • If there is pain or a sacral fracture
116
Q

What is always a concern that you hae to warn the owner about with pelvic fractures?

A
  • Trauma to the bladder or urethra
117
Q

Metatarsal or metacarpal fracture fixation

A
  • Most can be coapted
  • Minimal displacement
  • Consider the age
  • Difficult to place implants in small patients
118
Q

What to do with carpal or tarsal fractures?

A
  • Refer them
119
Q

When to consider coaptation or confinement?

A
  • Mandibular symphyseal fracture
  • Maxillary fracture that is non-displaced
  • Transverse fractures below the elbow and stifle in a young animal
  • Minimally displaced pelvic or scapular fracture
  • Most metacarpal and metatarsal fractures, unless large dogs
120
Q

What fractures to refer in humerus and femur?

A
  • diaphyseal and supracondylar
  • articular fractures
  • physeal fractures
  • Hard to externally coapt
121
Q

What fractures to refer in tibia and radius?

A
  • Comminuted
  • Articular fractures
  • Physeal fracturse
  • Distal radius
  • Geriatric

Ortho (10 decks)

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