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