extension of indications for dynamic stabilisation systems ......with the dynamic stabilization and...

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Extension of indications

for dynamic stabilisation systems

based on selectable stiffnesses

by

Stefan Freudiger Ingenieurbüro Flugwesen und Biomechanik IFB AG, Bremgarten/BE, Schweiz

Michel Lorrain Institut National des Sciences Appliquées, Toulouse, France

Gilles Dubois Nouvelle Clinique de l’Union, L’Union, France

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mechanical properties of DYNESYS (state-of-the-art)

and SpineShape S-IV (new)

DYNESYS (state-of-the-art)

SpineShape (new)

one stiffness given by cord, spacer

and pretension

three different stiffnesses given by

three different material grades:

• stiff (low flex)

• medium (mid flex)

• elastic (high flex)

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Known effect of DYNESYS for experimentally destabilised motion segments

The same effect will be achieved with SpineShape stiff rod

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But SpineShape extends the range of stiffness properties towards higher

elasticities for longitudinal loads

-400

-200

0

200

400

600

800

-2 -1 0 1 2 3 4 5[mm]

[N]

(one rod)

dynamic stabilisation

fusion

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...as well as for transversal loads

-150

-100

-50

0

50

100

150

200

250

300

0 2 4 6 8 10[mm]

[N]

(one rod)

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adaptation of properties in relation to clinical indications

First principle Normally the natural degenerative process is silent (i.e. without

symptoms).

Abnormally painful instabilities may appear with loss of

segmental integrity and with abnormal mouvements.

DYNESYS has proven in the past 20 years that it is capable to

restore the natural degenerative process and so is SpineShape

with stiff-rods expected to do.

Second principle Use of a mild implant (e.g. SpineShape elastic-rod) in an early

degenerative state is preferable over an invasive implant in a

late degenerative state.

The challenge will be to differentiate between patients with a

spontaneous healing potential and patients on a inevitably

worsening path.

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Illustration of the second principle

stable equilibrium

displaced neutral zone

elastic rods

more controlling than

load carrying

indifferent equilibrium

random motions

medium rods

controlling and load

carrying

unstable equilibrium

amplified motions

stiff rods

more load carrying

than controlling

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Examples of the second principle

elastic rods

foraminal stenosis

facet syndrome

disc bulging

disc herniation

hypomobility with

retrolisthesis

adjacent segment

protection

medium rods

post-discectomie

post nucleotomie

syndrome (iatrogenic

instability)

recurrurrent disc

herniation

stiff rods

dynamic stenosis

degen. spondylolis-

thesis ( grade 1)

hypermobility with

anterolisthesis

degenerative

scoliosis (Aebi I)

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allocation of indications into categrories of instability

degrees to be treated

Indication stiff med. elastic

Dynamic stenosis x

Dynamic stenosis with associated decompression x

Degen. spondylolisthesis (grade 1 acc. Meyerding) x

Degen. spondylolisthesis (grade 1 acc. Meyerding) in young patient x

Hypermobility with anterolisthesis x

Hypomobility with retrolisthesis x

Recurrent herniated disc x

Post-nucleotomy syndrome (iatrogenic instability) x

Facet syndrome x

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We know that the best indications for

DYNESYS are phase 2b to phase 6.

We always treated patients with signs

of dystability

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discopathy hypomobile...

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...which still allows a discrete retrolisthesis which is autoreducible...

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...and with the dynamic stabilization this retrolisthesis can be neutralized.

e.g. SpineShape elastic rod

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discopathy “hypermobile” in

spondylolisthesis and

retrolisthesis

Phase 4

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This dynamic dystability causes a severe sciatica with an articular cyst.

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With the dynamic stabilization and resection of the cyst the patient was re-stabilized and

is able to carry out her profession and her normal leisure sportive activities (golf) after a

follow-up of over six years.

e.g. SpineShape stiff rod

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dynamic stenosis in one level

18 The radiculography confirms the severity of the unstable stenosis...

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...which after re-stabilization the spine was perfectly stabilized, still

allowing a controlled range of motion.

e.g. SpineShape stiff rod

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central stenosis... Phase 6

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...and lateral stenosis

right slide:

liberation and re-stabilization in three levels have given this patient with a heavy duty

occupation a complete recuperation even follow-up of over five years

e.g. SpineShape stiff rod

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The natural story can influence the results

Patient 70 y, claudication

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The natural story can influence the results

Two years FUP

Adjacent disc intact

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The natural story can influence the results

Four years FUP

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F.U. 10 YEARS

Same case: Woman operated in 2000 (40 y)

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F.U. 10 YEARS

50 y with an intact disc (above)

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In the same patient, different stage of degeneration can occur at the same

time.

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The need of elasticity varies

according to each patient‘s

age and pathology

Thank you!

Consequently

e.g. medium rod with elastic end above