Chapter 2.1 Flashcards
Name biological complications associated with conventional fracture treatment (compression plates)?
- Iatrogenic soft-tissue damage
- Early bone necrosis underneath the plate
- Late stress protection of the bone
- Late stress protection of the bone refers to a phenomenon where a bone loses density or weakens over time due to reduced mechanical stress placed on it, often as a result of a rigid implant like a metal plate used to fix a fracture, leading to a potential risk of re-fracture once the implant is removed because the bone has become less adapted to normal loading conditions; essentially, the bone is “protected” from the usual stresses it experiences, causing it to become weaker in that area.
What is the principle of biological fracture healing in long bone fractures are characterized by?
Minimal biological damage during repair with flexible fixation.
How is minimal biological damage achieved in fracture healing?
- Eliminating anatomical reduction
- Practicing indirect reduction techniques
- Concentrating on axial alignment of the fragments.
What does flexible fixation in biological fracture healing involve?
Wide bridging of the fracture zone using
* locked nails
* bridge plating
* internal/external fixators.
What type of healing occurs under optimal biological conditions rather than absolute stability?
Indirect bone healing with callus formation.
What is the role of limited contact devices like the LC-DCP?
To reduce plate-bone contact without loss of friction to transmit forces.
What technique reduces bone necrosis during fracture treatment?
Locked-screw technique (LCP - locking compression plate, UniLock).
What instruments are required to facilitate the surgical approach to a fracture?
- Retractors
- Levers
- Elevators.
What is the difference between indirect and direct reduction methods?
Indirect methods keep the fracture area covered by soft tissue, while direct reduction exposes the fracture surgically.
What is a standard instrument well suited for direct fracture reduction?
Pointed reduction forceps.
What is used as a temporary reduction device in difficult fractures?
Intra-medullary nail.
True or False: Drills with three flutes are advantageous over conventional two-flute drills in oscillating mode?
True
What types of screws are generally used in veterinary practice?
- Cortex screws
- Cancellous bone screws
- Locking screw (techniqually a cortical screw)
- Cancellous screw
- Cortical screw
- Partial threaded Solid cancellous screw
- Partial threaded Cannulated cancellous screw
What are the characteristics of cancellous bone screws?
They have a larger outer diameter, a deeper thread, and a larger pitch than cortex screws.
Cortical (left)
Cancellous screw (right)
Where are cancellous bone screws typically used?
In metaphyseal or epiphyseal bone.
What is the design purpose of cortex screws?
Designed for the diaphysis.
What is the maximum recommended screw diameter relative to the bone diameter?
Should not exceed 40% of the diameter of the bone.
List the available sizes of cortex screws.
- 5.5 mm
- 4.5 mm
- 3.5 mm
- 2.7 mm
- 2.0 mm
- 1.5 mm
What is a unique feature of self-tapping screws?
They can be inserted by simply screwing them in after a pilot hole is drilled.
True or False: Self-tapping screws should be used as lag screws.
False
What is required for non-self-tapping screws before insertion?
A predrilled pilot hole
Then use a tap (cuts a thread in the bone that corresponds to the screw thread profile)
What is the design characteristic of cancellous bone screws?
They have a relatively thin core and wide, deep threads.
What are the two types of cancellous bone screws?
- Fully threaded screws
- Partially threaded screws
What is the primary use of fully threaded cancellous bone screws?
For fastening devices such as plates to metaphyseal and epiphyseal bone.
What is the primary use of partially threaded cancellous bone screws?
Used as lag screws.
What is a shaft screw?
A cortex screw with short threads and a shaft, used as a lag screw in diaphyseal bone.
What is the function of a cannulated screw?
Has a central hollow core and is inserted over K-wires that act as guides.
What sizes are available for cannulated bone screws?
- 3.5 mm
- 6.5 mm
What type of fractures are cannulated bone screws particularly suited for?
Reconstruction of metaphyseal or epiphyseal fractures.
What technique is used to achieve compression with a lag screw?
Overdrilling the bone thread in the near fragment.
What happens when the shaft screw’s (cortex screw with short thread) head is inclined?
It avoids engaging in the gliding hole, maintaining compression.
Drill bit needed for a 1.5, 2.0, 2.7, 3.5, 4.5, 5.5 cortical screw?
1.5 screw needs a 1.1 drill bit
2.0 screw needs a 1.5 drill bit
2.7 screw needs a 2.0 drill bit
3.5 screw needs a 2.5 drill bit
4.5 screw needs a 3.2 drill bit
5.5 screw needs a 4.0 drill bit
Drill bit needed for 2.5 and 4.5 cancellous screw?
3.5 screw needs a 2.5 drill bit
4.5 screw needs a 3.2 drill bit
What is a lag screw?
A lag screw refers to a type of screw used to provide interfragmentary compression between two bone fragments.
Both fully threaded and partially threaded screws can be used as lag screws.
What is the difference between fully threaded and partially threaded lag screws?
A fully threaded lag screw engages the far cortex while having a larger clearance hole in the near cortex. A partially threaded screw engages only the far cortex.
The fully threaded cortex lag screw requires specific drilling techniques to achieve proper placement.
When must a lag screw be inserted to achieve maximal interfragmentary compression?
The lag screw must be inserted in the middle of the fragment, equidistant from the fracture edges, and directed at a right angle to the fracture plane.
This positioning is crucial for effective compression.
What is the purpose of reaming the near cortex with a countersink before screw insertion?
To increase contact between the bone and screw head.
This step is performed after measuring the depth of the drill hole but before tapping.
What situations call for the use of a position screw instead of a lag screw?
A position screw is preferable when the insertion of a lag screw will cause a fragment to collapse into the medullary cavity.
This helps maintain the position of the fragments during surgery.
What is a fixed angle device in orthopedics?
A fixed angle device is a type of implant that maintains a specific angle between the screw and plate, advantageous in metaphyseal fractures.
Locking head screws can function as fixed angle devices.
Describe the technique for lag screw fixation after fragment reduction.
- Drill the gliding hole the same diameter as the screw thread. 2. Insert the drill sleeve and drill in the far segment the same diameter as the screw core. 3. Countersink the hole. 4. Measure the screw length. 5. Tap the thread hole. 6. Insert and tighten the screw.
The lag screw must be inserted through the center of both fragments and directed at a right angle to the fracture plane.
True or False: Lag screws can only be used in fully threaded form.
False.
Both fully threaded and partially threaded screws can be used as lag screws.
Fill in the blank: A lag screw must be inserted through the _______ of both fragments.
center
This positioning is essential for achieving maximal interfragmentary compression.
What is the consequence of failing to overdrill the near cortex?
The screw will not compress the fracture.
What are the steps for inserting a position screw?
- The fragments are reduced and maintained in position.
- Both fragments are drilled with thread holes, measured, and tapped.
- The inserted screw will not collapse the fragment.
What is the first step in the principle of position screw insertion?
Determine the desired function of the plate (neutralization, compression, bridging, or buttress).
What type of drill sleeve is used for the dynamic compression plate (DCP)?
A standard drill sleeve.
What is the diameter of the screw hole compared to the screw core for a 3.5 mm cortical screw?
The screw hole is slightly larger (2.5 mm) than the core of the screw (2.4 mm).
What should be done if the correct screw length is not available?
Choose the next longer screw.
What is the diameter of the hole that needs to be tapped for a 3.5 mm screw?
3.5 mm.
How many fingers are recommended for tightening a 2.0 mm screw?
Two fingers.
How many fingers are recommended for tightening a 2.7 mm screw?
Three fingers.
What does DCP stand for?
Dynamic Compression Plate
DCP is a surgical device used for fracture fixation.
What are the four functions that the same DCP plate may perform?
- Compression
- Neutralization
- Bridging
- Buttress
These functions refer to different modes of stabilization for fractures.
What is the screw hole design of the DCP intended to allow?
Axial compression by eccentric screw insertion
This design facilitates the movement of bone fragments for compression.
What sizes of cortex and cancellous screws does DCP 4.5 accommodate?
- 4.5 mm cortex screws
- 4.5 mm shaft screws
- 6.5 mm cancellous bone screws
Different sizes of DCP plates are used with specific screw sizes.
When was the DCP introduced?
1969
The introduction of DCP represented a significant advancement in orthopedic surgery.
How does the screw head function within the DCP hole design?
Slides down the inclined shoulder of the cylinder
This movement allows for fracture compression.
What is the maximum displacement per hole for DCP 3.5 and 4.5?
Up to 1.0 mm
This allows for effective compression during fracture fixation.
What is the maximum displacement per hole for DCP 2.7?
Up to 0.8 mm
This is slightly less than the larger DCP sizes.
How many eccentrically placed screws can be used on either side of a fracture?
DCP
One or two
This flexibility allows for optimal compression and stabilization.
If a screw is placed eccentrically, or at the side of the screw hole, it will slide downwards along the sloping plane as the screw is tightened; however, if it is placed in the neutral position, or in the center of the hole, it will not slide or provide compressive force.
What is the inclination angle allowed for screws in the longitudinal plane of a DCP?
DCP
25º
This inclination helps in adjusting the position of the screws during placement.
What is the inclination angle allowed for screws in the transverse plane of a DCP?
DCP
Up to 7º
This provides additional flexibility in screw placement.
What are the two types of drill guides for DCP plates?
- Eccentric (load) hole with a gold collar
- Concentric (neutral) hole with a green collar
These guides are selected based on the intended function of the plate.
In a neutral position, how much is the DCP hole off-center?
0.1 mm off-center.
What effect does the gold drill guide have on hole placement with a DCP?
Produces a hole 1.0 mm off-center away from the fracture.
What is the purpose of using the universal drill guide in buttress/bridging mode with a DCP?
To prevent any gliding of the plate relative to the bone.
What should be used when applying the LC-DCP?
The LC-DCP guide or universal guide.
What does LC-DCP stand for?
Limited Contact Dynamic Compression Plate.
What are the advantages of LC-DCP design?
- Decreased plate bone contact
- Even distribution of stiffness
- Ease of contouring
- Symmetrical evenly distributed plate holes
What materials is the LC-DCP available in?
Stainless steel and pure titanium.
What advantage does titanium have in the context of LC-DCP?
Outstanding tissue tolerance.
How does the area of plate-bone contact in LC-DCP compare to DCP?
The area of contact is greatly reduced.
It spares the capillary network, leading to improved cortical perfusion.
Describe the geometry of the LC-DCP plate.
It has a ‘scalloped’ underside for even distribution of stiffness.
What is the maximum sideways inclination for screws in the LC-DCP?
Up to 7º.
What is the maximum longitudinal inclination for screws in the LC-DCP?
Up to 40º.
What modes can screws be inserted in with the LC-DCP?
Compression
Neutral
Bridging
Buttress.
What does the LC-DCP universal drill guide allow for?
Placement of the drill bit in a neutral or eccentric position.
What happens when the inner drill sleeve of the universal guide is extended and placed against the plate hole?
An eccentric drill hole will result.
What occurs when the spring-loaded guide is pressed against the bone?
The inner tube retracts, allowing the outer tube to glide to the neutral position.
What are cuttable plates designed for?
Use in small animals
Cuttable plates are versatile and can be custom cut to accommodate various fracture situations.
What are the available sizes for veterinary cuttable plates?
- Smaller plate for 1.5 mm and 2.0 mm screws
- Larger plate for 2.0 mm and 2.7 mm screws
Each plate is 300 mm long with 50 round holes.
How can cuttable plates increase implant stiffness?
By stacking plates on top of each other
This can be done using plates of the same hole size or with a smaller hole plate on top of a larger hole plate.
What is a key characteristic of reconstruction plates?
Deep notches between the holes
This allows contouring in an additional plane compared to regular plates.
Are reconstruction plates as strong as compression plates?
No
They are not as strong and may be further weakened by heavy contouring.
What type of fractures are reconstruction plates especially useful for?
Fractures of bones with complex 3-D geometry
Examples include the pelvis, particularly the acetabular region, and the distal humerus.
Fill in the blank: Cuttable plates are not _______ plates.
compression
What is the purpose of using special bending pliers with reconstruction plates?
For contouring
Contouring is necessary to fit the plates to complex bone geometries.
What may need to be added to counteract bending forces in comminuted fractures?
Intramedullary pins
This can be used in a plate-rod technique.
What are the dimensions available for reconstruction plates?
- 4.5
- 3.5
- 2.7
These dimensions provide options for various applications.
What is a downside of using cuttable plates for certain fractures?
They are relatively weak
This may necessitate additional support in cases of comminuted fractures.
What are special veterinary plates designed for?
Use in small animals
AO has developed a variety of special plates due to the non-uniform size of animals.
What dimensions do acetabular plates come in?
2.0 and 2.7
Acetabular plates are specifically designed for veterinary use.
What sizes are veterinary T- and L-plates available in?
2.0 to 3.5
These plates are used in various veterinary surgical applications.
What type of fractures are double hook plates used for?
Proximal femoral fractures and intertrochanteric osteotomies
Double hook plates are specialized for certain fracture types.
What are the available versions of triple pelvic osteotomy plates?
2.7 and 3.5
These plates come in right and left versions with different angles of rotation.
Where are tubular plates particularly useful?
Areas with minimal soft-tissue coverage
Examples include the olecranon, distal ulna, or malleoli.
How should a tubular plate be applied in scapular fractures?
With its convex surface laid against the scapular spine
This method ensures optimal support for the fracture.
What are mini-fragment plates designed for?
Use with the 2.0 mm or 1.5 mm cortex screw
They are tailored for specific types of surgical cases.
What types of mini-fragment plates are available?
- DCP
- Round-hole plates
- Mini L-plates
- Mini T-plates
- Cuttable plates
These plates cater to various fracture types in small animals.
What are the smaller sizes available in the compact system?
1.0, 1.3, and 1.5
These sizes are associated with plates used in veterinary applications. There screws are self-tapping and insert with a star drive screwdriver.
What are the indications for compact systems in veterinary use?
- Maxillofacial fractures
- Metacarpal fractures
- Metatarsal fractures in cats and small dogs
These systems are specifically designed for smaller animals.
What is a limitation of the compact system plates?
Little resistance to bending
This is due to their small cross-sectional area.
What is the function of a Dynamic Compression Plate (DCP)?
To generate axial compression using a tension device or eccentric loaded screws
In what type of fractures is axial compression using a DCP typically possible?
Simple transverse fractures
What is the effect of prebending a DCP before securing it to the bone?
It leads to compression of the opposite cortex at the fracture line
What is the role of a neutralization plate in internal fixation?
To protect the lag screw fixation from rotational, bending, and shearing forces
What does a neutralization plate protect?
The interfragmentary compression achieved with the lag screw(s)
True or False: The function assigned to a plate is dependent on its design.
False
What is achieved through lag screws in combination with a neutralization plate?
Interfragmentary compression
Fill in the blank: A DCP or an LC-DCP applied as a compression plate results in ____ ____ at the fracture line.
axial compression
What is the function of a buttress plate?
To prevent collapse of the fracture.
Specifically used in metaphyseal fractures to support the adjacent articular surface.
When are bridging plates (aka biological plating) indicated?
In nonreducible comminuted diaphyseal fractures
Bridging plates are used to maintain alignment and length in complex fractures. Usually used following some form of indirect reduction.
Why should a longer and stronger plate be used as a bridging plate?
Because it is subjected to the full load of weight bearing
Ensures stability and support during the healing process.
What should be done if a metaphyseal fracture is accompanied by an intraarticular slab fracture?
The slab fracture should be repaired with lag screws and combined with a plate in buttress mode
This combination provides sufficient strength to support the fracture.
What does the soft-tissue envelope surrounding the fracture site do?
Exerts concentric pressure on the fracture fragments
This is crucial for restoring limb length while maintaining vascular supply.
What is the primary function of a bridging plate?
To prevent axial deformity as a result of shear or bending forces
It is crucial for maintaining the structural integrity of the fracture site.
How many screws should be used to fix the ends of a bridging plate to the bone?
At least three screws
This ensures solid fixation and stability of the plate.
What is the benefit of using a plate-rod combination for large comminuted fractures?
It provides synergistic mechanical properties
The combination protects against both bending and axial compression forces.
What percentage of the medullary canal diameter should the intramedullary pin be?
40–50%
This sizing is important for effectively reducing internal plate stress.
What does the addition of an intramedullary pin do to the bridging plate?
Reduces the internal plate stress and increases the fatigue life of the plate
It also decreases strain concentration at the screw hole.
What can the combination plate hole accommodate?
Either a conventional screw or the new locking head screw
The combination plate hole is a key feature in modern internal fixation systems.
What are internal fixators (aka locking plates/screws) primarily designed for?
To provide stability through a locking mechanism between the screw and the plate
Internal fixators have advantages over other plating methods.
What is a key advantage of locking plate/screw systems?
The plate does not need to be in intimate contact with the underlying bone
This reduces the need for exact plate contouring.
How do internal fixators help preserve the periosteal blood supply?
By reducing contact between the plate and the bone
This can lead to less bone resorption under the plate.
What type of fractures are internal fixators useful for repairing?
Acetabular fractures, carpal and tarsal fractures, and in double plating
Their stability makes them versatile for various fracture types.
What is the innovation introduced in the locking compression plate (LCP)?
The combination plate hole
This allows for the use of both conventional screws and locking head screws.
What are the two forms of the locking head screw (LHS)?
- Self-tapping LHS
- Self-drilling and self-tapping LHS
Each type is designed for specific applications in surgery.
What does the conical and threaded part of the combination hole provide?
Angular stability
This is crucial for the effectiveness of the locking head screw.
How can the LCP be applied?
- As a conventional dynamic compression plate for rigid fixation
- As a pure internal fixator with unicortical locking head screws
This flexibility allows for different surgical approaches.
What are the dimensions of plates available with the new combination hole?
Plates 3.5 and 4.5
These plates maintain the same overall dimensions despite the new hole design.
What is the mechanism used in the UniLock locking plate?
Threaded screw heads locked in corresponding threads in the plate
This mechanism ensures stability and secure fixation.
What types of screws are available in the 2.4 UniLock system?
2.4 mm and 3.0 mm locking head screws, 2.4 mm nonlocking cortex screw, 2.7 mm emergency screw
The 2.4 system includes one plate with these four screw types.
What feature do all screws in the UniLock system have?
Self-tapping
This characteristic allows the screws to create their own path in the bone.
What tool facilitates locking the screw head to the plate in the UniLock system?
A special drill guide
The drill guide centers the drill precisely into the hole.
What is a significant advantage of the UniLock system in veterinary orthopedics?
Wider potential applications due to small bones of cats and dogs
This allows for better treatment options in various veterinary cases.
What does CRIF stand for?
Clamp rod internal fixator
CRIF is a system used in veterinary surgery for fracture stabilization.
What are the components of the CRIF system?
A rod, standard screws, and clamps
These components work together to stabilize fractures.
For which types of fractures can the CRIF be used?
Diaphyseal and metaphyseal fractures
It is suitable for use in all sizes of dogs and cats.
What are some properties of the CRIF system?
Excellent versatility, good contouring capability, ease of application, minimal instrumentation, minimal contact with the bone, financially affordable, sufficient strength for immediate weight bearing
These properties make CRIF a preferred choice for fracture stabilization.
How does the CRIF construction benefit blood supply at the fracture site?
It touches the bone only at the clamp sites
This design favors vascularity and promotes rapid indirect bone healing.
What advantage do the clamps provide in the CRIF system?
They can be arranged along the rod and placed on either side, allowing solid fixation even in small fragments
This flexibility enhances the effectiveness of the fixation.
What happens when the screws are tightened in the CRIF system?
The clamp is firmly fixed to the rod
This provides stability to the fracture fixation.
What is required for accurate plate contouring when stabilizing reducible fractures?
Accurate plate contouring is required
This ensures proper alignment and stabilization of the fracture.
Why is contouring of plates necessary before application?
To match the anatomy of the bone and prevent loss of reduction
Especially critical if no lag screws are placed across the fracture.
What tools are best used for contouring plates?
- Hand-held bending pliers
- Bending press
- Bending irons
These tools assist in achieving precise contouring.
What should be avoided when bending plates?
Repeated bending back and forth
This weakens the plate.
Where should plates be bent to maintain their function?
Between the holes
This helps to avoid stress risers.
When using locking head screws, is perfect contouring necessary?
No
The design allows for some flexibility in contouring.
What is recommended for complex 3-D contouring?
Special flexible templates
These templates can be modeled to the bone surface.
