Ch 42 ESF Flashcards
What are Duraface pins?
What biomechanical advantages do they have?
Duraface pins are a negative profile pin by IMEX which has a tapered transition from the shaft to the negative profile threads, avoiding the stress-riser seen with a rapid transition
When compared to the corresponding positive-profile pin, they have 55% increase in pin stiffness and an average 54% increase in ultimate pin strength and a 2.3-4.9-fold increase in cyclic fatigue.
ESF is MIO
pros (5)?
risks (3)?
cons vs plates (5)?
- closed reduction or OBDNT
- preserve # haematoma and blood supply
- offer relative stability
- reduced soft tissue trauma
- can be easily dyaminised
- can be removed
long term risks:
-infection
stress protection
implant migration/failure
disadvantages compared to plates:
- increase infection risk due to percutaneous
- eccentric pacement, thus increased bending moments on pins
- not last if delayed healing occurs
- pin loosening cause morbidity
- increase owner compliance/nursing care
When may the use of a Duraface fixation pin be beneficial?
Stabilisation of smaller segments
Non-load sharing conditions
Biologically compromised bone
Large soft tissue envelope requiring a longer working length
Name the following ESF clamps
A - SK clamp (IMEX)
B - TITAN (Securs)
C - Securos U-Clamp (Securos)
Note the two different pin sizes and locations within the Securos clamps
List the possible methods of augmentation to increase frame stiffness
1.Articulations (interconnecting bars which do NOT cross the fracture)
2.Diagonals (Interconnecting bars which DO cross the fracture gap)
interconnecting bars resist shear/bending/rotation
3.Combined IM pin-ESF frame (pin should fill no more than 40%) - resist bending
4.Combined interlocking nail-ESF
5.combined plate + ESF
increase stiffness of bars will increase overall contruct strength and redue stress on individual pins thus protect pin-bone interface
What is the general rule for sizing of acrylic connecting bars?
The diameter of the acrylic bars should be 2-2.5 times the diameter of the bone, and the diameter of the scrylic bar should be 3-4x that of a comparable stainless steel connecting bar
What is vaporization when regarding acrylic connecting bars?
Above what size does vaporization become a concern?
Vaporisation is a consequence of excessive heat produced within larger-diameter acrylic columns, resulting in a vacuum and potential voids within the material that can decrease the density and stiffness of the column
Vaporisation is a concern if acrylic columns are over 25mm
List the commercially available veterinary acrylic systems
What is the full set time of these products?
What is the working time of epoxy-resin/putty? What is the full set time
Acrylx (IMEX)
APEF (Innovative Animal Products)
Full set time is 12-15 minutes
Epoxy putty (Knead-It) has a working time of 3-4min and a set time of 10-12 min
Management of fractures of the long bones of eight cats using external skeletal fixation and a tied-in intra-medullary pin with a resin-acrylic bar
AJ Worth
Median time to complete removal of the construct was 7 (range 5–12) weeks
The resin-acrylic ESF/tied-in IM pin construct was versatile and lightweight and allowed even highly comminuted non-load-sharing fracture configurations to be stabilised successfully using a biological strategy. Failure of the pin/acrylic interface did not occur and the frames provided sufficient strength as evidenced by healing without failure of the bar in these cases. A resin-acrylic ESF construct is inexpensive and affords the occasional orthopaedist the means to provide rotational stability when IM pinning has been used as the primary mode of fracture repair for short-oblique and transverse fractures. An extensive and costly clamp/bar inventory is not required, and there is greater flexibility for the orientation and placement of fixation pins than allowed by traditional linear bar systems.
What are the recommendations for wire size and tension for circular ESF?
What is the recommended rate and rhtyhm of distraction osteogenesis?
Rate of 1mm/day
Rhythm of 0.5mm q12hr
Distraction Osteogenesis
phenomenon in which bone is induced to form in the space between two bone segments that are pulled apart at a measured rate (Ilizarov)
If drawn apart at a rate of approximately 1 mm per day, bone is regenerated in a process that is histologically similar to active physis.
circular external skeletal fixation frames are uniquely well suited for this type of progressive distraction.
used for:
the correction of angular limb deformities,
to lengthen bone
to transport bone segments across a defect.
After an osteotomy is performed, the bone is left stable over the course of few days. This delay, called the period of latency, is necessary for the formation of a fracture hematoma
What is a hybrid ESF?
An ESF with a linear componenet on one side of the fracture and a circular component on the other side of the fracture. Commonly used for juxta-articular fractures
What are the safe corridors for the humerus, antebrachium, femur and crus?
Green = safe
Yellow = hazardous
Red = unsafe
What is the relationship between the stiffness of a transfixation pin and its length?
The stiffness of a transfixation pin is inversely proportional to its length to the third power
How far should the clamps be placed from the skin surface?
1cm
What are the principles of pin insertion to preserve the bone-pin interface?
1 - Selection of appropriate pin size - should not exceed 25% the diameter of the bone
2 - Adequate exposure of the bone with retraction of surrounding soft tissues
3 - Predrilling - All pins should be pre-drilled with a drill bit 0.1mm smaller than the core diameter of the pin. Significantly decreased mechanical and thermal injury
4 - Low-speed pin insertion - Drill speeds under 300rpm. This decreased thermal injury while avoiding wobble of the hand-chuck
What is the recommended timing for destabilisation when indicated?
Young dogs - 4-6 weeks
Adult dogs - 6 weeks
Older dogs and cats - 8-10 weeks
Name the following ESF configuration
A: Type Ia (unilateral, uniplanar)
B: Type Ib (unilateral, biplanar)
C: Type I-II hybrid
D: Type II modified (bilateral, uniplanar)
E: Type II (bilateral, uniplanar with all full pins)
F: Type III modified (bilateral, biplanar)
What are the available options for hybrid connecting bars?
What angulation does each allow?
Spherical washers and nuts - 10 degrees
C: Hybrid adapter - up to 65 degrees
D: VariBall locking hybrid rod (IMEX) - 100 degrees
What are the general rules for pin configuration?
3-4 pins per segment
Far pins placed first, followed by near pins and then interpositional pins
Place pins ¾ bone diameter away from adjacent joints
Place pins ½ bone diameter awat from the fracture line
What angle of insertion is aimed for when placing fixation pins in the vertebral bodies
45 - 60 degrees
mandibular pins
Effects of Transfixation Pin Positioning on the
Biomechanical Properties of Acrylic External
Skeletal Fixators in a Fracture Gap Model
Joachim Lahiani 2023
Twenty-four type I acrylic ESF were built simulating a fracture gapmodel.
Transfixation pins were placed centric (n¼12) or eccentric at ¼ of the column
diameter (n¼12) in the acrylic columns
Eccentric pin positioning decreased failure loads by
28% in bending (p<0.001).
Conclusion Eccentric position of transfixation pins within the acrylic columns alters
the biomechanical properties of type I ESF constructs. While acrylic offers several
advantages, when forming the columns, frame strength will be optimized if pins are
centrally located.
Description of and complications associated with reinforced,
free-form external skeletal fixation for treatment
of appendicular fractures in cats: 46 cases (2010–2019)
Yeh 2021
46 cats with fractures repaired with rFF-ESF
With the rFF-ESF technique, bending
the fixation pins and binding them together with orthopedic wire provides sufficient stabilization to allow postoperative radiographs to be obtained prior to PMMA application
43/46 (93%) cats had a successful outcome
fixator removal of 8 weeks
26% cats had major (n = 3) or minor (9) complications.
4 factors associated with postop
complications:
body weight
tibial fracture
use of a type 2 fixator
use of destabilization
Nolte et al29 found that type 2 fixators and tibial fractures were both risk factors for nonunion in cats.
Perry et al3 found that increasing complexity of ESF constructs in cats resulted in an increased complication rate, compared with bone plate stabilization of tibial fractures.
Witte et al12 recorded 3 nonunions
in 8 cats with distal tibial fractures stabilized
with hybrid ESF constructs.
Beever et al4 did not report any complications associated with stabilization of tibial fractures with ESF in cats, although it was not clear whether type 1 or 2 constructs were used
large retrospective study26 also did not
find an association between ESF and postoperative nonunion in cat
Transarticular elastic external skeletal fixator correction
of a stifle rotational deformity and patellar luxation
in a dog
Tiffany Chen
External transarticular orthodontic
chains connected to ESF pins placed in the femur and
tibia were used to gradually correct a 90 stifle rotational
deformity, and a transphyseal staple was used to correct
left femoral varus.
