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99 Cards in this Set

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What are the basic goals of fracture repair?
Factures should be SAFe
Stability
Alignment
Function
Name the forces acting on fractures
CRAB
Compression
Rotation
Avulsion
Bending
The goals of fixation are:
Prevent collapse
Resist bending in all directions
Counter torsion
Is a closed reduction possible if the fracture is 2-3 days old?
Not so much
Biological fracture management is best achieved by what type of reduction?
Open but do not touch
If you have an avulsion fracture, what must be part of your fixation plan?
A tension band to counteract the pull of the tendons and ligaments

Think about the figure 8 wire we put on the plastic bones.
True or False
A half pin lodges in the medullary cavity of the bone but does not penetrate it.
True--ish

It can go all the way to the cortex...it just doesn't exit the bone on the other side
Which of the following is external fixation a good option:
a. open reduction
b. closed reduction
c. Open but do not touch
b and c
How does an avulsion fracture occur?
The insertion point of a tendon or ligament is fractured and separates from the rest of the bone. The bone will break before the tendon usually - especially young animals. There is a lot of force from that tendon and ligament.
You should consider a fracture infected if its more than ________ hrs old by the time you see it.
4
Why is open reduction essential for articular fractures?
You need accurate realignment at articular surfaces or patient will have arthritis
If fragments are not stabilized then shearing can occur and new blood vessels are damaged. This prevents the process of __________.
Bridging
A long oblique fracture is greater than ____ degrees.
45
What's a greenstick fracture?
Incomplete fracture where part of the cortex stays intact.
When would you use external coaptation (splints and bandages)?
Young patient (heals faster but check it often)
Closed fracture
Fairly stable
Patient you can sort of control - if patient can't tolerate strict confinement then forget it
What is the princple of biologic fracture management?
To restore alignment and achieve stability with minimal disruption of the blood supply
Which external fixation systems accept positive profile pins and allow you to add clamps at any location?
Imex SK
Securos
Which fixation system is best for correcting angular limb deformities?
Ring Fixators
- controls all the forces and the roundness reduces pointy parts
The diameter of a pin should not be greater than _______% of the bone diameter.
25-30%
Which Salter Harris Fracture types affect the articular surface?
3,4,5
You need at least ____ pins to distribute the load and stabilize a fragment.
2
True or False
A fracture is REDUCIBLE if there is not more than 2 fracture lines and it can bear weight when you line it back up.
True
What are three things you could implement into your treatment plan that would minimize complications?
Limited activity of patient
Physical Therapy to minimize biological complications like muscle contractures
Make a model before attempting a complicated fixation to ensure there is no mechanical failure
True or False
Angling pins makes them stronger
True
What is the best way to counteract bending forces?
Short pins
Place connecting bar close to the bone where there is minimal soft tissue to penetrate.
Why are postive profile pins stronger than negative profile pins?
Positive profile means that the diameter of the pin doesn't get smaller where the threads are. This makes the pin a more solid and stonger unit.
Why do we pre-drill the holes in the bone?
Preserve the bone quality and makes a more snug fit into the bone.
General post surgery care recommendations include:
bandages for some short period of time
activity restriction
clean the pin-skin interface
antibiotics for the first 7 days
pain mgmt
If the bone diameter is 10 mm, what should the diameter of the pin be?
2.5 mm maximum

You don't want the diameter to get over 30% of the bone diameter.
Will the fracture be more stable if the pins are long or short?
Short
What things can the surgeon do to influence pin length?
insert in the plane with the least soft tissue to go through before you hit the bone
If you are asked to draw pin placements on a picture of a fracture, what should you keep in mind about pin spacing?
Close to the fracture to minimize the length of connecting bar between pins and evenly spaced.
Where is the weakest part of the fixator?
At the pin-bone interface
What's the difference between cortical and cancellous threads on pins?
Cortical threads are finer and closer together.
Free form fixators are ideal for which type of patient?
small dogs and cats
What are the common sites for an osteosarcoma
Towards the knee - on either side of the knee joint
Away from elbow - proximal humerus nad distal radius and ulna
Describe how a Fractured Coronid Process occurs.
Growth of Ulna and Radius is not synchronized. Either the ulna grows fast or radius grows slow. Ulna hits the humerus and puts pressure of the medial coronoid process of ulna and may fracture.
Compression forces have the most devastating effect on which type of fractures:
a. transverse
b. oblique
c. commuted
b. and c. becuase in a transverse fracture the compression force along the bone actually pushes the fractured pieces together while in the other two a shearing results and the bone gets shortened, blood vessels get damaged.

Shearing delays union and healing
Shortening compromises function
What is your top DDX if you see osteophytes on the anconeal process?
Fractured Coronoid Process
True or False
An IM pin effectively resists the forces of compression
FALSE

IM pins do not resist compression well at all because there is little grip between the main fragments and the smooth surface of the pin.
What occurs when the radius grows fast or the ulna grows slow?
Ununited Anconeal Process
True of False
An interlocking nail that is locked both distally and proximally with screws resists the force of compression.
TRUE
What tools in your orthopedic tool box resist the force of compression the BEST?
Interlocking nails with distal and proximal screws

Bone plates (because they are attached by screws)

External fixators that use short pins, adequate pin numbers and a short conencting bar span between the pins

Bilateral fixators because the connecting bar is on either side of the limb.
True or False
One of the most important influence on a frame's ability to resist compression forces is the length and number of pins.
True
What does the concept of bridging mean?
The fracture is so unstable that a plate needs to span it (like a gap) and take the load and resist all the forces - especially bending.
This usually happens in the metaphyseal region.
Which device resists the bending force the best?
Bone Plates when they act with the bone - when they have to support all the weight its a little less. Thicker the plate the better.

Fixators are weakest because the connecting bar is far from the bone.
How well does an IM pin resist bending forces?
Pretty good.
Bending resistance is realted to the radius of the pin to the 4th power --> means the larger diameter the IM pin is, the more bending it will resist in all directions.
Great for a femur.
How well do IM pins resist rotational forces?
Not at all
What are some differentials for pelvic limb lameness?
Hip Dysplasia
Pelvic Fracture
Cruciate Ligament Injuries
Luxating Patellas
Hip Luxations
Femoral Fractures
Lumbosacral Disease
Discospondylitis
Why would you rather purchase solid bone plates or bone plates with predrilled screw holes for your new orthopedic practice?
Solid bone plates - each screw hole makes the plate 40% less strong.
Which implements are best at resisting rotational forces?
Interlocking nail and screw
Plates attached with screws
Bilateral & Triangular Frames
Unilateral frames are ok but if you have a large dog, add a second bar on the same side
What is the most common way to reapir an avulsion fracture?
Two K wires to prevent rotation and a tension band wire to resist pull.
Order the following from weakest to strongest:
a. Trangular frame
b. unilateral frame
c. bilateral frame
b,c,a
Which type of pins require you to angle them to make them stable?
The pins that have no threads
True or False
Bilateral or biplanar frames are best for unstable fractures.
TRUE
True of False
You should position the clamps of your fixation device with the bolts facing away from the patient to avoid them hitting themselves with it.
FALSE

The bolts should be on the patient side of the connecting bar. This makes the pin length shorter = stronger.
True of False
Pin loosening is the most common complication of fixators.
TRUE
How is a butressing or bridging implant different from a neutralizing impant?
Neutralization implants share the load between the bone and the implant - used in primary bone healing
What's the principle of internal fixation?
To allow for joint motion
To bear weight
Maintain alignment and stability while optimizing function
List the components of an external fixator.
Connecting bar
Half Pin
Full Pin
Clamp
What is one of the big advantages of free form fixators?
Since the pins do not have to be all connected to one straight connecting bar the pins can be placed in different planes. This type of external fixator works well for an odd shaped fracture, irregular bone shapes (mandible) and for complex fractures where you don’t have a good plane to place all pins in one direction.
List the advantages of external fixators.
Simple Equipment
Adaptable to many fractures
Closed or open-but-do-not-touch technique
All metal can be removed once the fracture has healed
List the disadvantages of external fixators.
Pin loosening before the bone heals (PAINFUL). EF rely on the stability b/w the pin and the bone and there are situations where this will break done. If it breaks down before the bone heals then you can run into infection, instability, etc.
Infection d/t pin loosening
May affect limb function especially if pin has to go through muscle
Scary looking
Tear up the couch
Why are external fixators rarely used in the humerus or femur? Where are they commonly used?
Rarely used in the humerus or femur because of the large amount of muscle mass that the pins would have to penetrate to reach the fractured bone. External fixators are commonly used in the extremities.
How do you determine how many pins are needed in an external fixator? How many are essential?
The number of pins needed is determined by fragment size, pin type, pin diameter and bone quality.

2 pins are essential (MUST HAVE 2 pins). 3 to 4 pins distribute load to interface.
Describe the difference between a bilateral external fixator and a biplanar external fixator.
Bilateral external fixator the pins are on both side of the bone, but they are in the same plane.

A biplanar external fixators there are 2 unilateral frames, but they are coming in at different angles to one another (in a different plane)
Why can the pin diameter be no greater than 30% of the bone diameter?
If the pin is greater than 30% of the bone diameter then you start running the risk of weakening the bone and causing an iatrogenic fracture.
Describe a situation where we might modify the angle of the pin to closer to 90 to the bone.
We may modify the angle to increase the number of pins in a fragment.
What things can the surgeon do to influence the pin length?
You do NOT want the connecting bar touching the skin but you do want the connecting bar as close to the bone as possible
Orientation of the clamps
Muscle and soft tissue mass (the more muscle/soft tissue mass that you put the pin through the longer the pin will be). Surgeon needs to put the fixator where there is the smallest amount of muscle/soft tissue
Pin spacing
What is the rule for pin spacing on an external fixator?
You want the pins spaced 2-3 times the pin diameter. You also want to make sure that the pins are EVENLY spaced over the fragment length and the bone.
How does pin spacing related to connecting bar length?
The closer pin spacing will reduce the connecting bar length.
Describe the difference between a negative profile thread and a positive profile thread.
A negative profile thread is a pin where the diameter of the thread is the same diameter as the shaft.

A positive profile thread is a pin where the diameter of the thread is greater than the shaft.
Describe the proper technique for pin placement.
Pre-drill using a drill bit that is slightly smaller than the pin shank/core
Use a SLOW insertion speed for both the drill and the pin
What are the 3 mechanical classifications of internal implants?
Compression
Neutralization
Bridging
Describe compression internal implants.
The fracture faces are compressed together. Therefore the bone and implant work as one to counter the load.
When can we use compression implants?
Simple fractures
Bone plate and lag screw ????
Describe a neutralization implant.
The bone shaft is rebuilt, but you cannot compress the fragments together. The implant is necessary for protecting the primary repair of the bone. The primary implant helps reduce the load, but both the bone and the implant will take the load through the bone.
Describe a bridging implant.
With a bridging implant there is NO contact b/w the proximal and distal fragments. Unlike the other classifications, the implant must bear ALL the load and the bone must heal by secondary bone healing (not primary).
What are the rules when choosing wire for internal fixation?
Most malleable form
Always use the largest diameter possible (thicker is stronger)
Bending strength is proportional to the radius to the 4th power.
So a small increase in wire diameter can have a marked impact on the bending strength of the wire
Describe how cerclage wire works.
The wire goes around the outside of the bone and holds the fracture pieces together like the rings around a barrel. It will only work when all the pieces interlock to rebuild the bone shaft! The wire MUST be in DIRECT CONTACT with the bone. NEVER use this as your sole repair method.
Why is it so important to have the cerclage wire in direct contact with the bone shaft?
If there is tissue between the wire and the bone then the tissue will die, but the wire will not shrink down so there will be space between the wire and the bone which will lead to an unstable fracture.
When do we use skewer pins & cerclage wire?
Used to compress short oblique fractures. It is NOT suitable by itself.
When do we use the tension band technique?
Common avulsion Fractures of the…
Greater trochanter
Olecranon
Medial and lateral malleolus
Tibial crest
Calcaneus
(Cally's GOT MMs )
What are the advantages and disadvantages of IM pins?
Advantages:
Good resistance to bending

Disadvantages*
Poor resistance to axial compression
Poor resistance to rotational forces

*why IM are rarely used by themselves
What is an interlocking nail?
An interlocking nail is an IM pin with holds proximal and distal. The pin is “locked” to the major fragments by screwing bolts into the IM pin holes.
What are the advantages of an interlocking nail?
They are very strong in resisting bending forces
The bolts resist compressive and rotational forces
Easy to place with minimal disruption of blood supply
Where can we use interlocking nails?
Best suited for femur and humerus fractures. Can be used in the tibia if you are careful!!
(FHIN)
How do we decide what size bone plate to use?
Size depends on:
The size of the bone
The weight of the dog
The expected forces
List the different plate types.
Round hole:
Cuttable plates
Lengthening plates
Dynamic compression plate (DCP)
Limited contact DCP
Locking Plate
Flat style
String of pearls
Specialty plates (ex: t plate)
What is the difference between a DCP and a limited contact DCP?
A limited contact DCP has changes to its undersurface so that it doesn’t have as much contact with the bone. It is friendlier to blood supply around the fracture.
Briefly describe the technique for placement of a bone plate.
Open-but-do-not-touch technique
Contour plate to bone shape
Attach plate with screws
6 cortices per main fragment (usually equates to 3 screws in a fragment (bicortical screws))
Almost always performed with an open reduction
What is the function of the screws used with bone plates?
Compress the plate to the bone
Compress the bone fragments
What is the LAG effect?
When the screw doesn't go far enough to plant into the cortex
How common are pelvic fractures?
Represent 1/16th of all fractures - mostly HBCs
True of False
1 in 7 pelvic fractures involve the hip joint
TRUE
What makes up a hemipelvis?
Ilium
Acetabulum
Ishcium
Pubis

Sacrum connect the two but bears no weight so leave a fracture here alone
Most pelvic fractures occur after ______ with the one exception of _______________________.
major trauma

stress fractures of the acetabulum in racing greyhounds
What are the 3 points of the pelvic “triangle” that can help you evaluate the pelvis/hip joint on palpation?
Ilium
Tuber ischiatica
Greater trochanter
How do we diagnose pelvic fractures?
Most affected dogs are non-ambulatory
If ambulatory dog is shifting weight forward and away from pelvic limb(s)
The superficial landmarks (tuber sacrale, tuber ischiadicum, greater trochanter) may be asymmetric)
Bone fragments or instability may be detected during GENTLE rectal palpation