Fracture Objectives- Dr. Huck Flashcards by Robin Lemoine

What appendicular bone cannot be repaired with an interlocking nail and why?

Radius. Because of the curvature of the radius. Interlocking nail would displace the fracture.

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What are the primary benefits of external skeletal fixation compare to plating ?

Can be placed with minimal disruption of the fracture fragments
Useful for treatment of grade II and III open fractures
Implants can be removed in stages to increase the loading on the bone- Wolff’s Law
Low cost compared to internal fixation devices.

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Basic guidelines for placement of trans- fixation pins.

Clamps connecting the pins and rods should be at least ______cm away from skin.

1 cm

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What fractures are not amenable to external coaptation?

Never cast an OPEN FRACTURE or if it involves a JOINT.

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What is the most common complication associated with open fractures?

Osteomyelitis.

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What complications are associated with external skeletal fixation?

Pin tract drainage
Loosening or pins and wires
Osteomyelitis
Ring sequestrum
Nerve or vascular damage

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The following are describes of which type of internal fixation approach:

Primary bone healing
Perfect bone reconstruction
Rigid fixation with compressions at bone ends
REQUIRED FOR ARTICULAR FRACTURES: transverse, oblique, segmental fractures.

Open Anatomic Reduction/ Reconstruction

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Difference between yield point and failure point on a stress-strain curve for any material.

Yield point: when the material begins to deform __________. Occurs between _________ and ____________ deformation. Permanently deformed.

Failure point: material cannot withstand anymore ______ and fails.

Yield point: when the material begins to deform PLASTICALLY. Strain exceeds the materials ability to recover, rendering it permanently deformed. Occurs between ELASTIC and PLASTIC deformation.

Failure point: material cannot withstand anymore STRAIN and fails.

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Retrograde or Normograde?

Pin placed coming distally

Retrograde

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Why is Wolff’s law important when considering fracture fixation?

Bone remodels based on the forces that are applied. When there are increased forces(weight bearing) the bone remodels and thickens. But if there are decreased forces(non-weight bearing) the bone resorbs and weakens.

In simpler terms: Weight bearing is important so bone will remodel and will not reabsorb over the line leading to osteopenia.

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When is dynamization best applied with regards to the timing of fracture healing?

~ 6 weeks post repair

Callus must be present to achieve benefits of dynamization

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What percentage of the intramedullary canal should be filled if this is the primary source of fixation.

With cerclage: 70% canal fill

With plate: 35-40% canal fill

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Pros and cons of internal fixation vs. external coaptation.

The following are disadvantages for ________:

requires frequent rechecks and bandage changes
only for specific fractures
risk of bandage morbidity preventing continued use
immobilized joints

External coaptation

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Difference between elastic and plastic deformation.

Elastic: ____________change in shape.

Plastic: ___________change in shape.

Elastic: REVERSIBLE

Plastic: PERMANENT

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Difference between stress and strain.

Stress(cause or effect): external ________ applied to any cross sectional area.

Strain(cause or effect): _________ of a loaded material as compared to its original form. Measured in length.

Stress is the CAUSE: External FORCE applied to any cross sectional area.

Strain is the EFFECT: DEFORMATION of a loaded material as compared to its original form

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How is a lag screw used in fracture repair?

Tightening the screw pulls the trans cortex closer to the cis cortex causing COMPRESSION across the fracture.

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Difference in severity between the various open fracture grades.

Which type of fracture is seen commonly with bite wounds? There is mild soft tissue trauma without extensive soft tissue damage. This open wound is >1cm in size.

Type II

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What lends the most strength to tension band fixation?

Figure 8 wire between hole and pin

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What is unique about buttress plating compared to other plating modes?

Most or all screw hols should be filled.

No as stable because the main force of the one is going along the fracture like so when the animal bears wight the fracture wants to distract.

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Which screw, lag or position, provides more stability?

LAG provides more stability than a position screw.

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Normograde or Retrograde?

Pin placement beginning proximally

Normograde

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What plate types can be used to achieve compression of a fracture?

Dynamic Compression Plates (DCP)

Limited Contact Dynamic Compression Plates (LC-DCP

Locking Compression Plates (LCP)

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Why would someone choose to utilize a skewer pin in conjunction with a cerclage wire?

For use in SHORT oblique fractures. To aid in maintenance of reduction and promote compression across the fracture line.

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How does the use of dynamization promote bone healing?

Allows increased axial loading of the fracture to enhance callus hypertrophy and remodeling of the fracture.

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What are the 4 factors that should be considered when choosing implants for fracture fixation?

1. Fracture type and location 2. Bone affected 3. Patient factors 4. Surgeon preference and experience

Pros and cons of internal fixation vs. external coaptation. The following are disadvantages of _______: - expense to clinic and owner: lots of specialized equip and inventory required - Requires training - May require 2nd sx for explanation

Internal Fixation

When might it be necessary to remove implants?

Cold temperatures, infection, obvious pain from the patient.

What forces are neutralized with the application of an intramedullary pin?

**Resist BENDING forces only**

Basic rules/guidelines for plate fixation of fractures. What type of plate(conventional or locking) needs minimal to no contouring?

Locking Stable repair requires screws at least 4 cortices above and below fracture.

Principle for applying cerclage wire to a fracture. How far apart from the fracture ends should the wire be placed?

*Place 0.5cm from fracture ends, spaces ~ 0.5-1.0x bone diameter apart* Compresses the surfaces effectively while preserving some of the soft tissue attachments to the fragments.

Why must conventional plates(LC-DCP)be perfectly contoured to the bone on which they are applied?

Allows stress to be more evenly distributed across plate(less stress at screw hole) *Less contact with bone = less disruption of periosteal vascularity*

Goals of fracture fixation. Restore ______ and _______ to promote bone healing and limb function.

Restore LENGTH and ALIGNMENT to promote normal bone healing and limb function.

Name that salter harris fracture. Articular fracture that runs though the epiphysis, across the physis, and through the metaphysis.

Type IV

Pros and cons of internal fixation vs. external coaptation. The following lists advantages for internal or external? - Variery of fixation options to promote stable repair. - Can promote normal muscle/joint function during bone healing - Fewer rechecks

Internal Fixation

Appropriate order of steps when assessing and initially treating an open fracture. 1. Systemic stabilization: ______ the wound with __________. 2. One stable: Wear _______. Assess tissue damage, vascular and nerve supply. Assess _______________status of distal limb. Imaging. _______wound, _______culture, start antibiotic treatment.

Systemic stabilization is first priority -Cover wound with sterile dressing and evaluate better once patient is stable -Nosocomial organisms are far more virulent than what’s already in there Once stable: Wear GLOVES. Assess tissue damage, vascular and nerve supply. Assess NEUROMUSCULAR status of distal limb(May be difficult if analgesics already administered).Imaging. Clean WOUND, collect CULTURE, start treatment with Cefazolin

In what direction must a lag screw be placed in relation to the fracture in order to achieve compression?

Perpendicular to fracture line

Basic guidelines for placement of trans- fixation pins. Pins should be placed how far away from the fracture and each other?

1/2 bone diameter

Goals of fracture fixation. Balance the forces that promote ______ versus those that promote _________.

Balance that forces that promote BONE HEALING versus those that promote BONE RESORPTION.

Pros and cons of internal fixation vs. external coaptation. The following lists advantages for internal or external? - Limited supplies - Limited need for specialized training - Avoids prolonged surgical procedure

External Coaptation

Basic guidelines for placement of trans- fixation pins. Pin diameter should be no more than what % of bone diameter?

25%

Principle for applying cerclage wire to a fracture. When you cut the wire, how many twists should you leave?

Leave 203 twists or a 5-10mm arm Do not bend or twist over after cut. This will loosen the wire.

Principle for applying cerclage wire to a fracture. How long should the fracture line be?

at least 2x the diameter of the bone

Goals of fracture fixation. Permit early ________ with use of as many joints as possible during healing period.

Permit early AMBULATION with use of as many joint as possible during healing period. *Need micro motion to promote healing and not cause atrophy.*

Difference in severity between the various open fracture grades. What is the worst type of fracture that you will see?

Type IIIC: arterial +/- nerve supply to distal limb compromised. Requires anastomosis or amputation.

When might a physeal fracture go unnoticed and what are the possible implications of this?

Type V: not visible radiographically but that becomes evident several weeks later when physeal function ceases.

Basic guidelines for placement of trans- fixation pins. How many pins in the bone segment are required for stability?

At least 2 pins

What is the antibiotic of choice when treating an open fracture while waiting for culture results?

Cefazolin

What are the 5 complications associated with internal fracture fixation?

1. Implant failure- loosening, breakage, migration 2. Osteomyelitis 3. Impingement of nerves 4. Osteopenia 5. Delayed, mal or nonunion.

External Skeletal Fixation Types. Unilateral-uniplanar

Type 1 A

Basic rules/guidelines for plate fixation of fractures. What type of plate(conventional or locking) should be precisely contoured to match the normal shape of the bone surface?

Conventional Plates Increases strength of repair and prevents distraction of fracture ends during screw placement. Stable repair requires screws of at least 6 cortices above and below fracture.

Name that Salter Harris Fracture. Runs through the physis and a portion of the metaphysis.

Type II

Name that salter harris fracture. Fracture from crushing injury of the physis.

Type V

What fracture types MUST be repaired with anatomic reconstruction?

Articular Fractures

When a fracture is below the knee and elbow what are the indications for external coaptation of that fracture?

Needs to be: - Minimally displaced fractures and those amendable to reduction - Transverse, simple, closed fractures - Green stick fractures - Non articular fractures

Name that salter harris fracture. Fracture runs through the physis and the epiphysis and are generally articular fractures.

Type III

Which of the 3 types of screws(cancellous, cortical and locking) is the strongest under bending stress?

Locking Screw 2.9mm core diameter= more resistant to bending Bigger diameter= more resistant to bending.

What are the 4 modes achievable with plate application?

1. Compression 2. Neutralization 3. Buttress 4. Bridging

Principle for applying cerclage wire to a fracture. What types of fractures can you use cerclage wire on?

Long oblique or spiral fractures

3 types of strain that a bone can experience.

Tensile Compression Shear

The following describes which internal fixation approach: - Less rigid fixation - Second healing - "Open but do not touch" - Great for MIPO- Minimally Invasive Osteosynthesis

Biological Osteosynthesis

What types of fractures are suited to repair/stabilization via cross pinning?

Simple, transverse fractures close to the joint **Young (Salter Harries Type I and II)**

External Skeletal Fixation Types. Bilateral-uniplanar

Type 2 A

What is the main mechanism of action of a pin and tension band implant configuration in providing stability at a fracture?

TENSILE COMPRESSIVE: Fixation used to neutralize the pull of muscles/tendons on the fracture fragment. Distractive forces of tendon or ligament are converted into compressive forces.

Why are open fractures more serious injuries than closed fractures?

Because open fractures are more prone to infections and post op complications

What type of fractures are suited to repair/stabilization via diverging pin placement?

Salter Harris Type 1 fractures of the proximal humerus and femoral head.

Why are these fractures( Salter Harris) concerning compared to fractures not involving the physis?

Because they involve the growth plate in younger animals, its more concerning for healing because they can have more long term consequences than a fracture at the soley the metaphysis.

With what fracture type is plating in bridging mode necessary?

Comminuted fracture Used in biological osteosynthesis/MIPO

Why do you not have to contour the plate in the locking plate mechanism?

Thread locking screw head locks into threaded screw hole on plate, preventing the need for plate to bone contact for a stable repair.

What are the two general indications for an external coaptation fixation?

1. Fractures below the knee and elbow | 2. Fractures expected to heal rapidly

Principle for applying cerclage wire to a fracture. What type of internal fixation approach (anatomical or biological) is used?

Anatomic reduction- must be able to reconstruct bone column.

What types of bones are best suited for repair with interfragmentary wiring?

Simple fractures of flat, non-weight bearing bones that interdigitate well

External Skeletal Fixation Types. Bilateral-Biplanar

Type 3. Stiffer than Type 1 and II Strong and rigid.

External Skeletal Fixation Types. Which types can be used on the *humerus and femur*?

Type 1 A and Type 1 B

What is the difference between a position screw and a lag screw?

Position screw is placed ACROSS a fracture line whereas lag screw is placed PERPENDICULAR to fracture line. No compression with position screw. Weaker compared to lag screw. Forces directed at the screw than through the bone.

Difference in severity between the various open fracture grades. Which is the less severe type of open fracture?

Type I : created by bone fragment from inside that retracts back through skin

Goals of fracture fixation. ___________motion at the fracture ends.

MINIMIZE motion at the fracture ends.

What types of fractures are best repaired with tension band?

**Avulsion fractures and some osteotomies**

What types of fractures are amenable to being compressed without risking displacement or further bone damage?

Transverse Simple Closed

External Skeletal Fixation Types. Bilateral-Uniplanar with combination of *full and half pins*

Type 2B

Basic guidelines for placement of trans- fixation pins. How many pins are ideal for optimal stabilization?

3 pins per segment

Principle for applying cerclage wire to a fracture. In which direction should the wire be placed in relation to the fragment?

Perpendicular

Basic guidelines for placement of trans- fixation pins. Increased distance from the skin to the rod = _________ construct stability

Decreased Place connecting rods as close to the bone as possible.

External Skeletal Fixation Types. Unilateral-biplanar

Type 1 B

Principle for applying cerclage wire to a fracture. How many wires must be placed to stabilize the fracture?

At least 2

Which characteristics of cancellous screws make them better for use in cancellous bone/metaphyseal bone compared to cortical screws?

*Cancellous screws have an increased outer diameter to core diameter ratio.* This is why cancellous screws have improved pull out strength

What general fracture type can never be repaired by anatomic reconstruction?

Open, comminuted fractures

Fracture Objectives- Dr. Huck Flashcards

(86 cards)