Thomas F. Higgins, MD; Sean E. Nork, MD;

James P. Stannard, MD; and Philip J. Kregor, MD

Created October 2006 and Revised October 2011

Locked Plating

Locked Plating

Definition

Locked plating, for the purposes of this talk,

is a screw and plate construct for the

purposes of osteosynthesis, in which the

screw engages the plate with a mechanism

which secures a fixed angle between the

two.

HistoryLocked plating, improvised in various ways

for years, and in development for many

years, came into widespread commercial

availability and clinical use in the United

States between 1998 and 2002.

Five stages of new Medical Technology

1. Experimentation

2. Skepticism

3. Fevered enthusiasm / overuse

4. Complications and despair

5. Judicious use

Like much new medical technology, the

employment of locked plating was

complicated by a lack of a thorough

understanding of indications and

mechanism of action

The ideal recipe for implant and construct

stiffness is still not fully understood.

Where maximizing construct stiffness was once

the ultimate goal, locked plating has likely

created some situations where constructs have,

in fact, become TOO stiff.

The correct employment of locked plating

techniques necessitates understanding the

following:1. Mechanism of action of locked plating2. Differences from non-locked plating3. Indications for locked plating4. Contra-indications / misuses of locked

plating

Recommended Reading

Gauthier et al, Injury 2003,

Vol 34 Supplement 2, pp. B63-76

Mechanics of locked plating

Traditional (non-locking) plates rely on

friction between the plate and the bone

achieved by terminally tightening of

screws passed through the plate to the

bone.

Locked plating does not require that the

plate be compressed to the bone, as the

interface between the plate and screw is

secured without this plate-bone

compression

With non-locking fixation, failure of

fixation may initiate with toggle between

the screw and plate, subsequent loss of

compression between the plate and bone

Correct and incorrect sequencing in the application of locked

plating

Surgical Technique Reduce the joint (if applicable)

LAG First (Lag, then Lock)

Re-confirm alignment

Lock

After the second locked screw, no change

can be made

The next twelve slides should be viewed as a

“slide show”. The screws with green “x”’s

represent locking screws, and the screws

without “x”’s are non-locking.

Lab Exercise

Metaphyseal Fixation

Lab Exercise

Metaphyseal Fixation

Lab Exercise

Metaphyseal Fixation

Lab Exercise

Metaphyseal Fixation

Reduction of Shaft

Lab Exercise

Metaphyseal Fixation

Reduction of Shaft

Metaphyseal Fixation

Reduction of Shaft

Metaphyseal Fixation

Reduction of Shaft

Metaphyseal Fixation

Reduction of Shaft

Metaphyseal Fixation

Reduction of Shaft

Metaphyseal Fixation

Reduction of Shaft

Metaphyseal Fixation

Reduction of Shaft

Metaphyseal Fixation

Reduction of Shaft

Locked Plating Advantages

Increased rigidity

Decreased toggle

Potential use as a reduction tool

May permit fixation with less stripping of

soft tissues

May be helpful in osteoporotic bone

Locked Plating Disadvantages Very expensive Constructs may be too rigid Some percutaneous applications be self-

drilling– That must be unicortical or strips near cortex

No tactile feedback on bone purchase They “allow you to stop thinking”

– Reduction must still be achieved, it is not magically achieved by locking implant

List ofIndications for Locking

(Framework)

Indications for Locking Biological Fixation

– Spanning Comminution (bridging)– Percutaneous Techniques in selected indications

Implant as reduction tool

Metaphyseal / Bicondylar Articular Fractures– Short Articular Segment – Periprosthetic Fractures

Osteoporosis

Biological FixationWithout necessitating compression of the

plate to the bone to achieve fixation, locked

plating may be applied percutaneously, or

with less damage to the vascularized tissue

immediately adjacent the bone.

Obese 33 yo female with bilateral open femur fractures

I&D, Spanning external fixation

Locking plate is secured to the peri-

articular segment, the metaphyseal is not

disturbed or dissected, and then the plate is

secured to the diaphysis.

Both the nailed and

plated fractures heal

with callus

Percutaneous Techniques are a form of “biological

plating”

(in selected indications)

15 y.o. male

This is a functions like a nail:Secondary healing, Relative stability

Percutaneous / Submuscular Plating

Metaphyseal / Bicondylar Articular Fracture

36 y.o. male skier

36 y.o. male skier

With bicondylar involvement, and very small

articular segment, locking fixation allows us

to secure the joint surface back to the

diaphysis in the correct orientation

4 months out

Long Standing 6 months

Use of Locked Plate as Reduction Tool

1. Lock plate to articular segment in correct

alignment

2. Provisionally affix plate to diaphysis

3. Confirm alignment

4. Secure plate to the diaphysis with non-

locking or locking screws

Obese 47 y.o. female Open Distal femur fracture

Reduce Joint

Reduce jointm then

set the correct

orientation of the

plate on the

articular fragment

(as with this jg)

Make sure it is not

flexed or extended

on the lateral view

(done in this case

with jig)

After joint reduction,

make sure that the plate

is correctly aligned to

the articular segment.

Then connect to

diaphysis.

Connect reduced joint to Diaphysis

Short Articular Segment

Open Femur Fracture

27 y.o. male

Motorcycle vs. flatbed truck, then guard rail

Open L femur with segmental loss,

Segmental L tibia

Very small remaining articular segment

ORIF and cement spacer in metaphysis

Well healed after subsequent bone grafting

35 y.o. vs. tractor

Femoral neck fracture plus intertrochanteric

fracture equals short articular segment

Periprosthetic Fractures

(This is also a form of a short

articular segment)

Obese 64 y.o. female

72 y.o. male TAAPeriprosthetic Fracture

“Periprosthetic” = Short Articular Segment

Osteoporosis

74 y.o. diabetic female

Locking Plate Principles

Locking plate is an IMPLANT, not a

technique

There are unique techniques

Beware the siren call of M.I.S. (Mal-

aligned Implant Surgery)

Locking Implants Still Require Reduction

Unclear Indications/ Non-indication

Compression plating in healthy diaphyseal bone

does not require locking

16 y.o. male, healthy bone, non-locking fixation

18 y.o. female, diaphyseal injury. Locking fixation not necessary

Partial Articular Fractures “B-type fractures”

require buttress, not locking.

24 y.o. male Snowboarder vs. Half-Pipe

Beware “too rigid” construct

72 y.o. Rheumatoid female on multiple cytotoxic medications. Ground level fall. Repaired with this

locking construct

The experience over the last ten years with

locking fixation has demonstrated that we

now have the ability to make a construct “too

strong” or “too stiff”

Particularly in

1.Comminuted metaphyseal fractures, or

2.Very simple transverse or spiral patterns

rigid immobilization of the fracture may

obliterate all motion, and prevent the

formation of callus, leading to non-unions.

In these patterns, the correct answer may be a

wider spread of our fixation, allowing more

motion around the fragments, and the

formation of a more vigorous healing

response

Failed varus

nonunion revised to

this, allowing more

motion in the

metaphysis and a

callus response.

One other potential response to the problem of excess stiffness in locking constructs has been so called “far cortical locking”. This entails over-drilling the near cortex and then placing a screw that engages the far cortex and locks in the plate (see diagram, next slide).

This may theoretically allow more motion in the construct, and reduce strain at the screw – plate interface.

At the time of this publishing, this technology has not been proven clinically, but may have some promise in the future.

“Far cortical locking”

Locked Plating Mechanics Summary

1. Understand the biomechanical difference

from conventional plating

2. Understand the limitations

3. Reduce and lag before locking

Locked Plating Indications Summary

Biological Fixation

Plate as a reduction tool

Metaphyseal / Articular Fractures

Short articular segments / periprosthetics

Osteoporosis

Locked Plating Huge advance in plating

Must understand biomechanics and what the

various constructs accomplish

Need to know and understand the new “rules”

of locked plating, as we understand them, and

not just apply locked plating blindly

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Thank You

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Questions/Comments

If you would like to volunteer as an author for the Resident Slide Project or recommend updates to any of the following slides, please send an e-mail to ota@aaos.org