Lecture 14 Short Notes Flashcards
What is external skeletal fixation (ESF)?
a form of bone fixation that uses pins or wires inserted into bone fragments, connected by clamps or bolts
What are the primary uses of ESF?
-manage fractures
-correct bone deformities
What components are essential in an ESF frame?
-pins
-clamps
-connecting elements (rods, rings, freeform connections)
What types of pins are used in ESF?
-half-pins
-full pins
-tensioned fine wires
What is the optimal diameter of pins used in companion animals?
25 to 35% of the bone width at the insertion site
Why should pins larger than 35% of bone width not be used?
they increase the likelihood of bone fracture due to the oversized holes required
What are the advantages of threaded pins over smooth pins?
-stiffer
-stronger pin-bone interface
What is the mechanical performance of ESF clamps affected by?
-the design
-how tightly they are tightened
What are the current nomenclature types for ESF frames?
-unilateral (type 1)
-unilateral biplanar
-bilateral (type 2)
-bilateral planar (type 3)
-circular
Which type of ESF frame is the weakest?
unilateral ESF frames
How are the mechanical properties of a bone-frame construct optimized?
by minimizing the length of pins, wires, and connecting elements
What is a major disadvantage of ESF compared to other fixation systems?
more owner compliance is generally required for proper management
What can result from pins passing through muscle?
-increased drainage
-pin loosening
-pain and reluctance to bear weight
What type of wires are typically used in circular ESF?
-tensioned wires
-olive wires (not routinely used)
What is the benefit of hybrid constructs in ESF?
they can provide greater stiffness than traditional wire constructs
What is crucial for external fixation in fracture treatment?
mechanical stability must be achieved without compromising adjacent soft tissues
What method enhances the accuracy of pin placement in external fixation?
fluoroscopy
What is the typical procedure for securing an external fixation frame to the bone?
far-near-near-far pin placement
How does bone healing compare between external fixation and plate fixation?
bone healing is more rapid after external fixation
What are the limitations of bridging plates in fracture fixation?
subjected to high bending moments, leading to implant fatigue failure and screw pullout
What is the advantage of intramedullary implants like Steinman pins and Kirschner wires?
ability to restore axial alignment of a bone while providing high resistance to bending
What is the hallmark design feature of modern interlocking nails?
Interlocking screws inserted through holes along the nail length
What are the indications for interlocking nails (ILN)?
diaphyseal fractures of the humerus, ulna, femur, and tibia
What complication is associated with standard interlocking nails?
acute construct instability, also known as slack
What design was developed to improve the stability of the nail-locking device interface?
Angle-stable ILN (AS-ILN)
What unique feature does the AS-ILN prototype include?
self-centering and self-locking mechanism
What are the benefits of using angle-stable ILNs according to in vitro studies?
significantly less angular deformation in torsion and bending compared to standard ILNs
What was the clinical outcome for dogs treated with the AS-ILN?
faster clinical union and less lameness compared to standard nails
What is a significant finding from a study on the AS-ILN for feline fractures?
the smaller I-Loc system is safe and effective for cats
What is the purpose of a bone screw?
fixation of a fracture by providing stability through compressive force
What are the main components of a screw?
-head
-core
-threads
What is the major diameter of a screw?
the largest diameter of the screw measured from the outside tip of one side of the thread to the outside tip of the other side
What is the difference between cortical and cancellous screws?
cortical screws are designed for dense cortical bone, while cancellous screws are for trabecular bone
What is the function of a plate screw?
to attach plates to bones and provide compression of the plate against the bone
What is the recommended number of bicortical screws for most applications?
at least three bicortical screws (six engaged cortices) on either side of the fracture
Which type of screw provides interfragmentary compression between bone fragments?
lag screw
How should a lag screw be inserted for maximum interfragmentary compression?
perpendicular to the fracture line and in the center of the fragment
What is cerclage wire primarily used for?
to pull bone fragments together to rebuild the shaft
What should cerclage wires NOT be used for?
as the sole means of fracture repair
What are the ideal configurations for using cerclage wires?
long oblique fractures or fractures with a large butterfly fragment
What can compromise the effectiveness of cerclage wire?
tissue caught between the bone and the wire
What are the common methods of securing cerclage wires?
-twist
-single loop
-double loop knots
What is a significant disadvantage of the Targon® nail compared to the I-Loc™ nail?
torsional instability due to locking mechanism slippage
What is the pitch of a screw?
the distance between the threads on the screw, equivalent to the distance a screw advances with one turn
What should be done if the appropriate length screw is not available when placing a plate screw?
the next longer screw length should be used
What is a common issue with partially threaded cancellous screws?
prone to failure due to stress concentration at the junction of the threaded and non-threaded portions
What can reduce the ability of cerclage wire to withstand loading events?
scratching, notching, or kinking the wire
Which knot has the greatest strength when securing cerclage wires?
double loop knot
What is one potential complication of improperly positioning the cerclage wire knot?
increased irritation of overlying soft tissues
