Biomechanics Flashcards
Palierne
2 locking plate constructs
VCOT 2019
Omission of 3rd innermost locking screw
~led to a 20% reduction in stiffness
~increased relative displacement of 40%
Beever
PO complications associated with ESF
VCOT 2018
Complications associated with
~Transarticular frames
~Age
Wagoner
Fiberglass & Thermoplast
VCOT 2018
FG > TP cranially
Lateral splints 64% reduction in frontal plane motion with FG
Macedo
2.5 mm Locking nail
VCOT 2017
Nail compared to 2.4 mm bone plate
1/2 torsional strength
1/3 stiffness
Slippage of the locking mechanism was probably the cause of the early failure
Marturello
I-Loc Feline Fx
VetSurg 2021
Time to clinical union?
Mean fill?
Time to clinical union 7.2 weeks
Mean fill of 50%
I-Loc 3 is likely appropriate for all feline humeri
I-Loc 4 is well sized for feline femora
Muro
Stiffness Type II Ex Fix vs. LCP
VetSurg 2021
ESF stiffer than LCP
~ML Bending
~Axial Compression
Equal in CC Bending
Type II ESF stiffer
ML bending than in CC bending
LCP stiffer
CC bending than in ML bending
Kaczmarek et al VCOT 2020
Compare the biomechanics strength of the LCP and polyaxial locking system.
Polyaxial locking system 32% weaker than LCP
Watrous et al VCOT 2018
What where the conclusions regarding 1.5mm LCP vs 1.5mm vs 2.0mm plates?
Torsion stiffness - 2.0 > 1.5 stacked> 1.5 LCP = 1.5
Compression - 1.5 stacked = 2.0 = 1.5 LCP»_space; 1.5
Overall 1.5 LCP similar to 1.5
Pallierne VCOT 2022
2 screw vs 3 screws in locking plate model
Omission of the third innermost locking screw during bridging osteosynthesis subjected to compression forces led to a -13.3% reduction in the number of cycles to failure
-23.5% reduction of the load withstood by the plate before plastic deformation occurred
3 screw > 2 screw stiffer
3 screw < 2 screw displacement
3 screw > 2 screw number of cycles to failure
3 screw > 2 screw load at irreversible deformation
All constructs failed by plate bending at the gap between the two cylinders.
Park VCOT 2022
Effect of Bidirectional Insertion of External Skeletal Fixation Pins on Axial Pullout Strength in Canine Cadaveric Bone
Pins used for external skeletal fixation should be placed unidirectionally to the desired position with fluoroscopic guidance, intra-operative depth gauge measurements or measurements from preoperative radiographs.
Repositioning pins results in loss of peak pullout strength with TRO (tapered run out) and PP pins (positive profile).
Positive profile pins had significantly greater pullout strength than TRO and TNP pins placed unidirectionally to the desired position.
Method of insertion had no effect on peak pullout strength of TNP pins.
TRO and PP pins inserted unidirectionally to the desired position had significantly greater peak pullout strengths than insertion bidirectionally or if the shaft of the pin violated the cis-cortex.
Adding an IM to a plate results in
Reduces plate strain
Increases stiffness
Radius ex fix
Ia
Ib
IIa
IIb
Tibial ex fix
Ib
III
Ex fix femur/Humerus
Ia
Ib
4 A’s of Fracture repair
Alignment
Apposition
Apparatus
Activity
