Fixation Constructs Flashcards
1
Q
Which forces are neutralized by a cast?
A
- Bending and a little rotational
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
3
Q
Which forces are neutralized by cerclage wire?
A
- Torsion or rotation
- Must be on a long oblique fracture
4
Q
Which forces are neutralized by a plate?
A
- Bending, compression, and rotation
5
Q
Which forces are neutralized by an external fixator
A
- Bending, compression, and rotation
6
Q
Which forces are neutralized by an interlocking nail?
A
- Bending, compression, and rotation
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
8
Q
What factors can a surgeon control?
A
- Tissue handling
- Asepsis
- Poor reduction
- Inadequate immobilization
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
10
Q
Moderate fracture score
A
- Older dog with a transverse fracture
- Load sharing; healing still delayed
- Young dog with a non-reducible fracture
11
Q
Low fracture score?
A
- Generally non-reducible old fractures in older dogs
- Compromised healing
- Fracture must be very rigid
12
Q
How long do most low fracture scores have to be maintained?
A
- 6 weeks or more of VERY rigid construct
13
Q
What fixation methods neutralize all fracture forces?
A
- Interlocking nail
- External skeletal fixator
- Plate
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
15
Q
When to use open reduction
A
- Articular fracture
- Comminuted non-reducible fracture of long bone (that’s open)
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
17
Q
Pros of definitive stabilization
A
- Inexpensive
- Noninvasive
- Doesn’t require a lot of equipment
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
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
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
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
22
Q
Instruments for external fixation
A
- Smooth or threaded pins
- Connecting bars
- Clamps
23
Q
Know the different types of external skeletal fixators
A
- just know them
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
25
What ancillary stabilization tactics can be used?
- Add IM pin
- Add cerclage wire
- Add screws
- Can also do more connecting bars
26
Diameter of pins in ESF
- 25%
27
What must you remember with caring for ESF?
- Don't forget the owner
- Carefully discuss aftercare
- Post-op full bandage
- Then a bumper bandage 3-4 days post-op
28
Circular fixator - when to use?
- With short just-articular bone fragments
- Uses wires, so takes up less space
- Can apply to radius, tibia, humerus, and femur
29
Pros of external fixation
- versatile
- Cheap
- Non-reconstructable
- Closed reduction or minimal approach
- Wound management
- No permanent implants
- Dynamization (staged disassembly)
- Allows early limb use)
30
What can you use to replace the whole connecting bar?
- Epoxy resin or methyl methacrylate
| - Replace clamps or connecting bar
31
What type of pins do you use with a free-form ESF?
- Threaded pins
32
Factors that affect bone healing?
- Age
- Fracture location
- Cell response
- Circulation
- Concurrent soft tissue
- Stability of the bone segment
- Aseptic technique
- Activity of the patient
33
What is the normal blood supply to the long bone?
- Nutrient artery
- Proximal and distal metaphyseal arteries
- Periosteal arteries
34
What direction is normal blood flow to the bone?
- Centrifugal
| - medullary canal to periosteum
35
What direction is fracture blood flow?
- Centripetal
| - From surrounding soft tissue
36
What happens to blood supply during fracture?
- Centripetal (from surrounding tissue)
- Medullary tissue is disrupted
- metaphyseal vessels enhanced
- Extraosseous vasculature
37
Which reduction will have the least effect on blood supply?
- Closed reduction
38
Which types of reduction are most biologic?
- Closed reduction with cast or external fixation are most biologic
- Rapid callus formation
39
When is fracture healing evaluated?
- 2-8 weeks post op in puppies
- Otherwise probably 4-6 weeks initially
- 12, 10, or 16 weeks post op
40
What is strain?
- Ratio between ∆ in gap width to total gap width
| - See the slide for an example of how to calculate it
41
Does strain increase/decrease with increasing fracture rigidity?
- Decreases
42
Do tissues become more or less tolerant of strain as a fracture heals?
- Less tolerant!
43
Indirect bone healing
- callus formation
| - Fibrous connective tissue and cartilage callus
44
Direct bone healing
- 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
45
Intramembranous bone healing
- 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
46
What cell type differentiates into osteoblasts with intramembranous bone healing?
- Mesenchymal cells differentiate into osteoblasts
| - Combination of direct and indirect bone healing
47
What % strain can occur with intramembranous healing?
- 5% strain
48
What are bone grafts used for?
- Enhance bone healing for fracture repair and arthrodesis
49
What do bone grafts provide?
- mesenchymal stem cells, osteoblasts, growth factors, bone for scaffold
50
Osteogenesis
- New bone development and support
| - Osteoblasts
51
Example of a graft that allows for osteogenesis
Cancellous autograft
52
Osteoinduction
- Induces differentiation of mesenchymal cells into osteoblasts
53
Osteoinduction example
Demineralized bone matrix
54
Osteoconduction
- Acts as a scaffold for host bone
55
Example of osteoconduction
- Cortical allograft
56
Osteointegration
- Surface bonding between graft and host bone
57
Where can you get autogenous cancellous bone?
- Proximal humerus
- Proximal tibia
- Ilium
58
Cancellous autograft properties of osteogenesis, osteoinduction, and osteoconduction
- Great for all three
59
Radiographic union
- Point at which healing has progressed to the point where there is evidence of bone bridging of all fracture lines in all views
60
Clinical union
- Point at which healing has progressed ot the point in strength that the fixation can be removed
61
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
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
How long can direct healing take to occur?
<3 months
3-6 months
6-12 months
>1 year
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
Delayed union
- Fractures that heal more slowly than anticipated
| - Progressive signs of bone activity visible on radiographs
64
What is the #1 cause of delayed union?
- Lack of stability
65
Other reasons for delayed union?
- 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
Nonunion?
- Arrested fracture repair process
67
What must happen to ensure healing with a nonunion?
- Surgical intervention!
68
What usually leads to nonunion?
- 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
Vascular non-union
- Lucent line through fracture site
| - Some fibrous tissue but cannot move on
70
Hypertrophic nonunion
- Lots of bony proliferation
| - Large amounts of non-bridging callus
71
Treatment for hypertrophic nonunion
- Debridement, grafting, and stabilization
72
Atrophic nonunion
- Biologically inactive pseudoarthrosis
| - No evidence of bone reaction at the fracture ends, and the bone ends appear sclerotic
73
Malunion
- 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
Osteomyelitis definition
- Inflammatory condition of bone and medullary canal
- Bacterial or fungal (rarely fungal)
- Acute hematogenous vs post-traumatic
75
What are most post-traumatic osteomyelitis due to?
- Bacterial infection
| - Biofilm (bacteria, glycocalyx, and implant surface)
76
What does a biofilm do?
- Protects bacteria from antimicrobials and host defenses
77
Clinical signs of osteomyelitis
- Pain, tenderness, swelling, erythema (acute)
| - Drainage (chronic)
78
Lab findings for osteomyelitis
- NSF on lab work
79
What steps to take for diagnosing osteomyelitis?
- 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
Treatment for osteomyelitis?
- 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
What to do with implants if there is evidence of osteomyelitis?
- 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
Indications for implant removal?
- 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
Causes of pathologic fractures
- Neoplasia
- Osteomyelitis
- Bone cyst
- Radiation therapy
84
Radiographic features of pathologic fractures
- Lytic and/or proliferative bone (cancer typically has both)
- Periosteal reaction
- Soft tissue mass
85
Quadriceps contracture or tie-down
- Unstable fracture in a young dog
86
Sciatic nerve entrapment
- Not uncommon with pinning a femur
| - Avoid by placing the pin normograde if possible
87
Goals for internal fixation
- Adequate reduction
- Rigid fixation
- Early active motion
- Early weight bearing
88
Atraumatic surgery
- goal to preserve function
- Maintain blood supply
- Decrease incidence of infection
- Minimize invasion of soft tissue
89
Implant characteristics
- Biocompatibility
- Resist corrosion
- Same alloy to prevent corrosion when implants are mixed
- 316L stainless steel
- Never reuse
90
Plate screw
- Anchor a plate to bone
91
Position screw
- Hold bone fragments in anatomic position
92
Lag screw or compression screw
- Compresses two bone fragments
93
Drill bit - what does it correspond to?
- Corresponds to the inner shaft
94
Tap - what does it correspond to?
- Corresponds to the threads of the screw
95
Steps for lag screw fixation
- 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
What determines plate length?
- Number of screw holes
97
What determines plate size?
- Cortical screw that the plate hole will accept
98
Plate hole configurations
- Veterinary cuttable plate
| - Oblong hole
99
Limited- contact dynamic compression plate
- Tapered edge
| - Trying to minimize contact with periosteum
100
Plate configuration
- Narrow, broad, standard
101
What can dynamic compression plates combat?
- Compression
- Neutralization
- Buttress
102
How to compress using a dynamic compression plate?
- Drill off center
103
Concepts for applying bone plates
- 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
How many cortices should be spanned with a plate?
- Minimum three screws or six cortices above and below the fracture
105
Advantages of locking plates
- 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
Concepts for locking plates
- Plate contouring not critical
- Locking screws must be perpendicular to the plate
- Reduce fracture before tightening
- Longer plate with fewer screws is best
107
What type of fractures can get a tape muzzle?
- Minimally displaced
- caudal fractures
- Comminuted fractures
108
What type of fractures can get dental bonding?
- malocclusion
- Caudal fractures
- Comminuted fractures
109
What else can be used for mandibular or maxillary fractures?
- Stroud wiring (etching with wire placed around the teeth
| - Symphyseal wiring
110
Scapular fracture classification
- Stable extra-articular (body)
- Unstable extra-articular (body or neck)
- Intra-articular (glenoid)
111
When is fixation indicated for scapular fractures?
- Unstable, extra-articular and intra-articular classifications
- Generally for scapular neck and glenoid fractures
112
Scapular fractures - what will happen if can't do surgical management?
- Most will heal
113
Indications for pelvic fracture stabilization
- Weight bearing (acetabulum, ilium, sacroiliac joint)
- Articular fractures (acetabulum)
- Pelvic inlet narrowing
- Contralateral injury
- Uncontrollable pain (may be a sacral wing fracture)
114
Ilial body fractures
- can heal with two lag screws
- 2 k wires and hemi-cerclage
- plates
115
Sacroiliac luxation - when to repair?
- If there is pain or a sacral fracture
116
What is always a concern that you hae to warn the owner about with pelvic fractures?
- Trauma to the bladder or urethra
117
Metatarsal or metacarpal fracture fixation
- Most can be coapted
- Minimal displacement
- Consider the age
- Difficult to place implants in small patients
118
What to do with carpal or tarsal fractures?
- Refer them
119
When to consider coaptation or confinement?
- 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
What fractures to refer in humerus and femur?
- diaphyseal and supracondylar
- articular fractures
- physeal fractures
- Hard to externally coapt
121
What fractures to refer in tibia and radius?
- Comminuted
- Articular fractures
- Physeal fracturse
- Distal radius
- Geriatric
