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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!