screw placement and types 59 y/o male moped rider matter · 2018-05-08 · 10/2/2017 1 screw...
TRANSCRIPT
10/2/2017
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Screw Placement and Types
Matter
The Blasted Distal Femur Facture: How to
Improve Outcomes
Abstract ID#: 1506
Friday October 13, 2017
Kyle Jeray
University of South Carolina, Greenville
59 y/o Male Moped Rider
• Pinpoint open
• Contralateral tibial shaft
fracture
• Disabled but works as
painter
• Smokes 1 ppd
• Drinks 3-6 beers/day
• NIDDM, HTN
59 y/o Male• CT
• Treatment Choice?
Evaluation of Distal Femur Fractures• CT scan – gives details about articular surface
involvement
– May be beneficial to wait until after external fixation (if being used)?
5. How Often Do We See (Hoffa) Coronal Plane
Fractures with Intra-articular Fractures of the Distal
Femur?
• A – 10%
• B - 35%
• C – 50%
• D – 75%
Evaluation of Distal Femur Fractures• Don’t forget the Hoffa fragment!
– 38% of intercondylar distal femur fractures have a coronal plane fracture
(Nork et al, J Orthop Trauma, 87:564, 2005)
– Most precisely diagnosed via CT scanning
76% single condyle
85% lateral condyle
Open fx 2.8 x coronal
fx than closed fx
Coronal fx diagnosed
in 47% with CT and
only 21% with xray
only
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59 y/o Male
• Treatment Choice?
3. Which Implant When Used Alone is
Contraindicated for a Comminuted Distal
Femur Fracture?
A - Condylar buttress plate
B - Blade plate
C - Dynamic Condylar Screw (“DCS”)
D - Locked plate
E - Retrograde medullary nail
These are Fixed
Angle Devices
Condylar Buttress Plate Is Not
Its ALL about the SCREWS!
• Instability with
metaphyseal
comminution
(medially)
• Implant does not resist
varus collapse
• Need locking screws
to create fixed angle
construct
Screws Outside the Plate Important! Screws Outside the Plate Important!
• Don’t forget about
reduction
• Lag screws of
appropriate length
• Standard or
headless?
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How Many Screws?
• Enough to create
stability – Rule of
thumb is 8 cortices
• Signs of fixation
frustration Cables
Plate Length and Screw Numbers
• Shorter plates less
working length
• Short plates stiffer
• Shorter plates higher
risk of failure
I= bh3/12
Unicortical versus Bicortical?
• Not as much fixation
as bicortical screws
• Does not minimize
stress at end of plate
versus standard
screws
59 y/o - Post-op Day 19
Failure Why? Not the Plate
• Screw length often as
important as number!
• Only the lag screw
survived
Failure Why? Location!
• Place screws in good
bone!
• Missed posterior
condyles
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Similar Case
• Reduction completed
before plate applied
• Note screws location and
length
• You control the stiffness
Start Over
• Nonlocking screws
outside the plate
• Locking screws in
plate to provide
support to resist
varus
Better?
• Longer plate
• Longer screws
• Better position of
screws
• Improved joint
reduction
Reduction and Mechanics
Reduction and Mechanics
• Are screws alone enough?
• Bone quality plays a role
• Osteoporotic bone may
require plate support or
locking screws in plates
Mechanics – Nonlocking Screws
with “Large” Washer to support
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HealedFCL reduces construct stiffness:
� Standard bicortical drill hole
� Narrow, flexible screw shaft
� Controlled motion envelope ∆d
� Cantilever bending of screw shaft
� Increased screw working length
Far Cortical Locking
How can the stiffness of locked internal fixators be controlled?
1. in-house testing; 2. Field, Injury, 99; 3. Stoffel, Injury, 2003; 4. Bottlang, JBJS, 2009
A
↑ plate elevation ↓ stiffness: 35% (2→6 mm) 1 ↓ strength, ↓ clinical useB
B
Far Cortical Locking ↓ stiffness: > 80% → comparable strength 4D
D
Approach Gain Cons
↓ plate cross-section ↓ stiffness ↓ strengthA
Stoffel, Injury, 2003
“One or two holes should be omitted on each side of the fracture to initiate
spontaneous fracture healing, including the generation of callus formations. ”
C ↑ plate span ↓ stiffness: ns2 , 5% 1, 60%3 ↓ strength: 33% 3, longer plates
C
∆dsmallload
displacement [mm]
axia
l lo
ad [
N]
LP FCL
high
load
� Parallel gap motion
� Bi-phasic stiffness
Far Cortical Locking Screws
51 y/o MCA
open distal femur
fracture
3 Months F/U
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Summary
• Screws matter!
• Locking screws have a role create fixed angle to
support varus forces in distal femur
• Nonlocking screws work consider medial
fixation as well if using nonlocking screws
Summary
• Far cortical locking screws can decrease the
stiffness of the construct and encourage callus
formation
• By varying location of screws the surgeon can
effect the stiffness as well (working length)
• How many screws? Just enough but not too
many!