Argos SpineNews 1

April 2000
News from the world of Spinal surgery and biomechanics
Focus on :
Birth of Argos’ website
Spineview software
History of spinal surgery
When biomechanics
interfaces with statistics
Fourth Argos meeting
The Montreal Imaging
and Orthopedics
research Laboratory
and Orthopedics
research Laboratory
A N O R T H O L I N K P U B L I C A T I O N

Another step forward in communication between surgeons ! . . . . . . . . . . . . . . . .7
Argos
A new dimension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Organization chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Members list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
3 partners, 3 orientations, 1 goal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
International training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Birth of Argos’ Website . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Web Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
History of spine surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
News . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Functional testing of spinal implants . . . . . . . . . . . . . . . . . . . . . .18
SpineView - a tool designed to improve quality of care . . . . . . . . . . . . . . .19
Mechanical characteristics of rod . . . . . . . . . . . . . . . . . . . . . . . . .29
When biomechanics interfaces with statistics . . . . . . . . . .34
Numerical simulation of scoliosis surgical treatment .35
The Montreal Imaging and Orthopedics
research Laboratory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
Clinical case - Instrumentation in spinal fusion . . . . . . . . . . . . . . . . . . . . .43
S U M M A R Y
Evaluation
Communication
For more information,
bibliography, French
version, please log on to
Argos website.
www.argos-europe.com
News from the world of Spinal surgery and biomechanics
April 2000
Training

April 2000 - N°1 ARGOS SpineNews 6
by Alexandre TEMPLIER
ARGOS General Manager - Editor in Chief
EDITORIAL STAF
Editor in chief
Alexandre Templier
Production/Art director
Karim Boukarabila
Board of editors
the Argos committee
Writer/Translator
Alexandre Templier
Patrick Bertranou
Philippe Strauss
Assistant publisher
Carl Stéphane Parent
Cédric Caloin
ARGOS COMITTEES
Communication Committee :
Patrick Bertranou, MD
Philippe Bedat, MD
Henri Costa, MD
Pierre Kehr, MD
Charles-Marc Laager
Pierre Soete, MD
Training Committee :
Jean-Paul Steib, MD
Jean-Paul Forthomme, MD
Franck Gosset, MD
François Lavaste, PhD
Richard Terracher, MD
Jean-Marc Vital, MD
Evaluation Committee :
Wafa Skalli, PhD
Jacques De Guise, PhD
Michel Dutoit, MD
Alain Graftiaux, MD
Henry Judet, MD
Christian Mazel, MD
Tony Martin, MD
EDITORIAL HEADQUARTERS :
ORTHOLINK (US)
546 Hillgreen Drive, Beverly Hills CA
90212 USA
Phone (310) 557-2000
Fax (310) 843 9500
ORTHOLINK (CE)
33, rue Vivienne
75002 Paris FRANCE
Phone (33) 6 08 43 82 81
Fax (33) 1 45 08 46 67
ARGOS
SpineNews
VOLUME 1, NUMBER 1
Editorial
Dear Members and readers,
First and foremost, on the occasion of the release of the first
issue of our journal “ARGOS SPINE NEWS”, we would like to
express our most heartfelt thanks for the tremendous response
on our previous journal. Your remarks and encouragement in
“The Connector” proved invaluable to us.
You have fully grasped the importance of communication in our
association and definitely contributed to helping us address
Argos’ members needs for information.
As you read through this issue, you will notice that ARGOS has
steadily expanded; the recent launch of our Internet site is ano-
ther mile stone toward better and larger communication with
the “Spine world”.
The consolidation of our three activities: Communication,
Training and Evaluation led us to expand our committees’ staff
who will undoubtedly make full use of our upgraded tools.
While preserving its spirit of creativity, rigor and friendship,
the introduction of additional training tools such as the Spine
Simulator, Argos Clinical Database and Spine View will boost
not only the efficiency of each one of us but and mostly enhance
the prestige and influence of Argos in the world.
With all of our best wishes for the new millenium !

… Another step forward in
communication between surgeons
Communication
The day was given over to lumbo-
sacral Arthrodesis and to the pain
that it can engender and divided
into three parts tackling three
major themes.
Post-operative pain:
- premature
- medium term
- long term
These three cases are very different
and through analyses, actual cases
and discussions we shall get to
know their specifics.
7 ARGOS SpineNews N°1-April 2000

Premature post-operative pain
Professor Kehr and Doctor Gosset
were privileged to open this
congress. They explained imme-
diate post-operative pain. The most
painful moment remains waking up
and with it the fear of feeling dis-
comfort. One can be confronted by
a premature radicular pain caused
by the bad positioning of screws.
Remaining vigilant is therefore a
must, especially if the patient
shows signs of deficiency. A scan
would show a possible error in the
line of the disc or screw diameter.
The appearance of a haematoma or
a possible unknown herniated disc
appears could also be detected.
The two authors finished their
exposé by concluding that the dia-
meter of a well-chosen screw
avoids haematomas and prevents
other complications, it is nonethe-
less necessary to be careful of pre-
vious screw holes and that a curet-
tage remains useful.
Presentation of immediate post-
operative imagery was given by
Professor Dosch, who demonstra-
ted the various useful criteria in the
domain of scanography
Radiography, scanning and IMR
were all touched upon.
Radiography is an very exact exa-
mination to check for the correct
positioning of material. However a
centred radiography, with detailed
section will allow for a good assess-
ment, contrary to a standard radio-
graphy which is far less effective.
Scanners remain very viable with
regard to imagery, especially in the
case of titanium screws, a satisfac-
tion rate of 87% whereas screws
made from chrome cobalt only
register a satisfaction rate of 68%.
As for IMR, it can analyse a root
perfectly if the material is in tita-
nium, with any other material the
results would be nil or almost non-
existent.
He finished with the figure of false
routes which is situated between 10
& 40%, a figure which would seem
to be associated with old statistics,
and would be reduced to 0% were
there navigation.
Doctor Caux illustrated brilliantly
the explanation of treatment proto-
col in post-operative pain. Several
pharmaceutical means were evoked
upon.
First, AINS which is non-mor-
phine solution and the most impor-
tant treatment. It cancels the pain
chain, however with patients of 75
April 2000 - N°1 ARGOS SPINE NEWS 8
and over one should remain vigi-
lant.
Then there is paracetamol which
has a central action but which
creates allergies, morphine-based
analgesic or codeine, dextropo-
poxyphene and tramadol are grou-
ped together, were all mentioned.
Their effects are varied depending
upon the person treated.
The use of morphine can be carried
out intravenously or with a PCA
pump. (90% Satisfaction). But eva-
luation of the pain is very impor-
tant. Drowsiness may ensue and it
is an effect which should not be
ignored. In effect, adaptation for
each particular patient is necessary
(Age and condition).
In conclusion, a strict and regular
supervision is indispensable.
The three orators went on to dis-
cuss the origins of pain. If it provo-
ked by a radicular compression,
there is a risk of motor deficiency, a
paraesthesia or a radicular inflam-
mation.
However, care is necessary with
regards to the nerve root which can
become inflamed in which case the
pain will be radicular or rachidian.
Doctor Mazel presented his interactive clinical cases.
Best poster reward : Doctor Viego-Fuertes
Doctor Kumano from Japan

9 ARGOS SpineNews April 2000 - N°1
In all events, putting a drain in
place remains a possibility, but cer-
tain surgeons who have carried out
this practice have noticed the out-
break of infection.
The first medical case that Doctor
Mazel analysed was that of woman
who had been suffering over the
last six months from pain when wal-
king. The surgeon who took her in
hand did X-rays, but nothing was
detected. She therefore underwent
an IMR where a misalignment of
L4-L5 was seen. A “floating”
arthrodesis was done and the result
was satisfactory for despite inter-
mittent pain, she was back walking
very quickly. Meanwhile, this inter-
mittent pain became more regular
and the patient came back with a
deficiency on the left-hand side.
The discovery of a weak disk was
made in addition to which she suf-
fered from temperature and urinary
infections. She was admitted into a
re-education centre when several
weeks later the infection went into
remission.
The diagnosis of a post-operative
spondylosis was made, she was
then treated with anti-biotherapy,
but there is a remaining doubt as to
what became of the damaged disc.
Medium term
post operatory pain
The second part of the congress
centred around medium term pain.
Doctor Kunogi began by explai-
ning the clinical analysis of lum-
bago after lumbar arthrodesis
where he groups two categories :
- Twinflex
- Rigid
The Twinflex category seems to suf-
fer less ruptures than Rigid, (33 %
1- M.Viejo-Fuertes was rewar-
ded for his presentation du
embryological development and
the importance of ligamentum fla-
vum. Morphogenetic, anatomic
and histological studies have been
carried out to demonstrate pro-
prioceptive role of this yellow
ligament. The yellow ligament is
derived from a mesenchymateux
tissue and develops with the ver-
tebral structures, and this will
make the difference with the
other ligaments.
2- M. Claude Argenson made a
presentation on an anterior endo-
scopic graft in fractures.
Two phases were exposed :
- Mini-approach
- Videoscopy
A lumbar fracture which is fixed
by screws and median hooks is
much more aesthetic.
3- The last poster was that of M.
Dutoit which shows the impor-
tance of zygapophysis synovial
cysts. It is a relatively rare lesion
which causes troubles resembling
a paralysing hernia. It is the pos-
ter which most held the public's
attention.
Posters selected for presentation.
Three of the posters selected were retained by the participants.
This article will be
soon available in french at
Communication
Vote for poster presentations. As a conclusion, Professor Kehr gave us a synthesis of the whole day.

of ruptures). These ruptures are
due to screw problems. Generally,
it is possible to notice that they
become detached from the upper
part, which causes pain in the leg or
in the lower back, pain which will
disappear once the nerve root has
been secured. Fractures of the pel-
vic ring following a sacral-lumbar
fusion increase by 5 % in women of
over 50.
These are the mechanical
constraints which seem difficult to
put up with.
The problems of pseudo-arthrosis
in the context of an instrumented
arthrodesis were evoked upon by
Professor Vital. Re-operations for
pseudo-arthrosis are due to various
causes such as : smokers, discs pla-
ced too high, the inadequacies of
grafts.
When an IMR is carried out on a
patient who has an instrumented
rachis, a persistent modic reveal
itself to be a suspicion for a pseudo-
arthrosis. It is nonetheless neces-
sary to wait for surgery before pro-
nouncing a diagnosis. A patient
who can properly explain the pains
he is suffering and who can place
himself correctly are an important
source of prevention.
Then followed a presentation by
Professor Logroscino on the role of
anterior support in the prevention
of post-operative pain. The PLIF
(Posterior Interbody Fusion) single
level anterior support for an arthro-
desis, was one of the points deve-
loped for it is a system which allows
for a renewal, a reduction and a
very satisfactory alignment. Its
advantage being that it allows a cir-
cumferential arthrodesis, moreover
it is a less traumatic and cheaper
method.
The use of large surface cages
gives a far better result than smal-
ler cages.
Finally, a good fusion is a guarantee
of the ridding of pain.
Pseudo-arthrosis and lumbago after
lumbar arthrodesis is a very impor-
tant theory in the view of Doctor
Kumano. For him, the factors allo-
wing alleviation of the pain :
- screws
- cages
In fact, poly-axial screws seem far
better for avoiding complications
and consequently pain. Titanium
cylindrical cages are more accep-
table, a multi-axial connection bet-
ween the screws and rods (a very
demanding technique) provides an
excellent anterior fusion and avoids
complications and lumbago pro-
blems.
The discussion following lent
towards the necessity of the use of
cages. Several doctors participated
in this debate, M.Argenson toge-
ther with several other colleagues
believed that are cages of interest
but in the event of further need for
surgery, it is necessary to increase
in width, which is very tedious. For
Doctor Kumano, anterior fusion is
necessary especially if restoring
the height of the foramen, but
others, such as Professor Vital,
thought that height restoration is
not always necessary.
Finally, Doctor Kunogi pointed out
that isolated cages bring about
complications and are more uns-
table.
Doctor Mazel presented another
medical case, concerning a 54-year
old woman suffering from a “repe-
titive” discopathy, several proposi-
tions of treatment were made from
the assembly : Dr Vital would carry
out a biopsy, Dr Logroscino a dyna-
mic scintigraphy. In fact a arthro-
desis was done and no post-opera-
tive problem was detected.
After a year, however, the patient
suffered from lumbago pains. A dis-
cography was carried out, post-ope-
rative MRI shows complete reco-
very. Long term problems In his
exposé on problems linked to lum-
bago, Doctor Antonnetti spoke of
the necessity to carry out previous
tests. Patients must be listened to
and observed. Signs of non-organi-
city can be detected and it is these
signs which indicate that the per-
son is not a good candidate for sur-
gery.
Spinal X-ray scanning and numerical analysis demonstrations.

11 ARGOS SpineNews N°1 - April 2000
Functional surgery for non-functio-
nal pathology is the key to success.
Observing particular gestures of
the patients such as : arrival (correct
walking, limping ), facial expression
(grimace, smile), ease of undres-
sing, muscular force and reflexes,
allow an opinion to be forged on the
necessity to operate or not. One
solitary sign of non-organicity
may not be sufficient to refuse to
carry out the operation.
After an initial general visualisation
of the patient, Doctor Rohmer stu-
died his psyche. For him, all lumbar
pain has a psychological conse-
quence, very often, patients do not
want to upset their daily lives
because of their illness. Care
should be taken with hyperactive
patients for very frequently, it is
they who are incapable of freeing
themselves from work to find the
time necessary for their operation.
Pain is no longer a physical sensa-
tion, it is an intolerable phenome-
non for society.
It must be remembered that “lum-
bago is to the workplace what
migraine is to conjugal duty”.
Professor Dosch showed keen
interest in long term imagery, he
affirmed that late complications
due to material are in the order of 1
to 4%. Those linked to grafts are 3
to 9%. The results engendered fol-
lowing a standard radiography are
68%, concerning an IMR after
ablation of material, the results are
satisfactory but indirect, for the
graft must be sufficiently solid just
as the pseudo-arthrosis. The scan-
ner remains the surest examination
after an ablation of material.
However, it is indispensable to
take detailed sections and interpret
the results with flexibility .
It is necessary to remain vigilant vis
à vis mechanical problems which
can be based on two elements :
- recurrences
- hypertonia
In a general manner, long term ima-
gery provides results but it is neces-
sary to wait for more precise ans-
wers.
Criteria of non-organicity and the
evaluation of the psyche were the
basis of the discussion that follo-
wed. The radiologist and the psy-
chiatrist do not have, according to
them, the power to decide, they
cannot submit their opinions nor
remarks, the decision remains that
of the surgeon. It is certain that
patient's remarks such as “whatever
you do, it will not change a thing !”,
are to be taken into account for a
sentence such as this is a criterion
of non-organicity. The use of the
corset was mentioned at several
points as well as infiltration or dis-
cography, tests which can be neces-
sary.
Doctor Lazennec showed us how to
adjust the position of an lumbo-
sacral arthrodesis. To begin with it
is necessary to evaluate the infil-
tration, give attention to the sagittal
balance and try to localise the pain
which can come from the ligament
or the disk. The position pelvic can
also be at fault.
With regard to sagittal balance, it is
necessary to measure the sacrum
swing (Sacral Tilting) which should
be equal to 41°, pelvic version
which should be at 12° and the inci-
dence angle which on average must
near to 53°.
The ideal solution would be to
increase the swing of the sacrum
and to reduce the pelvic version.
Vertebral osteotomy for the flat
back was presented by Professor
Argenson. It is a safe intervention
in several cases, it is necessary to
Communication

These informations,
the bibliography or
French version will be soon
available on
the Website…
Those informations,
the bibliography or
available on
the Website…
localise the pain, correct the cypho-
sis and carry out a posterior osteo-
tomy. Results are not immediate,
but the use of the median hooks
technique is very efficient. In
effect, it gives a minimum conges-
tion in the canal and avoids screws
being wrenched out, a large exten-
sion is recommended in order to
reduce compression.
It was Professor Guigui who then
explained the outcome of the levels
above and below. He showed two
groups, one being the patients
decompresses with and the other
without arthrodesis, from which
three worsening factors :
- arthrodesis
- the importance of the time factor
- use of instrumentation.
It should be noted that there is no
clinical difference between the two
groups. It is certain that the indi-
cation of arthrodesis must be reflec-
ted upon.
The last debate of this congress ten-
ded to wards the source of pain.
The reminder of the rachis balance
in relation to the hips was made.
Doctor Lazennec reiterated his
idea that pain due to mis-positio-
ning of the sacrum is lateral and
that they is almost certainly due to
the sacroiliac ligament as well as
the thoraco-lumber junction. The
pain for the arthrodesis in L5/S2 is
better tolerated than that in L4/S2.
Finally, Professor Argenson under-
lined the fact that it is necessary to
remain prudent in the large lumbo-
sacral fixations for scoliosis.
Doctor Mazel also stated a medical
case. It could be called 'a tale of suf-
fering' The patient a 40 year old
man was a physical instructor. He
underwent a hexatriolone injection
in L4/L5, then a chemical arthro-
desis. (something which no longer
takes place. Three years later, he
complains of pain and an laminec-
tomy is done.
He improves, but two years later,
the appearance of lumbago is evi-
dent. He undergoes new X-rays,
but nothing is detected.
The question now is: What to do
now for this patient who is now
incapable of covering a distance of
100 metres ? ■ PS.
73 rd Annual Meeting of the Japanese Orthopaedic
Association
6-9 April, 2000 - Kobe JAPAN - Information : +81 78 382 5985
E-mail: seikei@med.kobe-u.ac.jp
Paediatric Orthopaedic Society of North America
1-4 May, 2000 - Vancouver CANADA - Information : 847/384-4246
E-mail: goldberg@aaos.org
27th European Symposium on Calcified Tissues
6-10 May, 2000 - Tampere FINLAND
E-mail: secretariat@congcreator.co
7th Congress of AOLF
10-13 May 2000 - Beyrouth LIBAN - Information +961 1 613 619
(fax)
55 th Annual Meeting of the Canadian
Orthopaedic Association
3-7 June, 2000 - Alberta CANADA
Spine Across the Sea III
(Joint Meeting with the Japanese Spine Research Society)
23-27 July 2000 - Kamuela HAWAI - Information +1 847 698 1630
First Interdisciplinary World Congress
on Spinal Surgery
27 August to 1 September 2000 - Berlin GERMANY
Information +49 30 857 903 0
12th conference of the European Society
of Biomechanics
27-30 August, 2000 - Dublin IRELAND - Information : 353 1 667 1713.
E-mail: esb2000@ted.ie
ISO Congress
11-15th September 2000 - Stockholm SWEDEN
Eurospine 2000
10-14 October 2000 - Antwerp BELGIUM
Information +32 3 240 20 40 (fax)
16 th Meeting of the North American Spine Society
31 October-3 November 2001, Seattle WASHINGTON
Information +1 847 698 1630
Agenda

Argos
A new structure,
for a new dimension
Communication
S
ome four years ago, when it
was created, ARGOS set
itself the task of promoting
information, training and evalua-
tion in the treatment of spinal
pathologies. An authority giving
pride of place to clarity and dia-
logue, it has kept clear all along of
any dogmatism and striven to allow
the scientific debate to range over
the widest possible field. It is early
days yet to appreciate how such a
complex part translates to public
health. Yet ARGOS has managed to
carve out a one-of-a-kind place for
itself and now stands alone in its
own right in today’s context of ever-
increasing deontological require-
ments. It convenes on a yearly
basis, makes for easier face-to-face
meetings between clinicians (more
than 30 clinicians from different
countries have been welcomed in
1999 into Argos training centers),
and promutes research schemes
(Spineview, clinical follow-up) and
training programs (in situ contou-
ring for the correction of deforma-
tions, dynamic fixation of the lum-
bosacral spine). It also makes its
presence felt in the field of evalua-
tion. It is firmly geared to collect
and survey clinical data, and has
moved further into the production
of annual morbidity reports. As a
pointer to ARGOS’ global vision
and commitments, the associa-
tion has spread across national
boundaries and enjoys fast glo-
bal expansion. It branched out in
Belgium last year, and Japan hosted
last March the first non-European-
based annual event focusing on
dynamic instrumentation.
Argentina saw in last september the
first edition of an annual event
dedicated to dynamic fixation of the
lumbosacral spine and the correc-
tion of deformations by the in situ
contouring technique.
Three advisory committees
Intense technological changes, and
notably the advent of the Internet
(see the article on ARGOS Web
site), are set to step up diffusion,
both geographically and in scope.
Such a context of fast expansion
only fueled the rationale for revam-
ping the European mother entity. A
major overhauling of the organiza-
tional framework simply had to be
undertaken to adapt to new requi-
rements, as a very real and practical
way of supplementing the effecti-
veness of the association. ARGOS
announced three multiprofessio-
nal teams involving surgeons, bio-
mechanical engineers and people
from managerial spheres. They are
expected to lay down guidelines
and manage the association’s key
missions. They will be centered on
a structure organized into three
advisory committees that will
include the Communication sec-
tion, the Training section , and the
Evaluation section . The commit-
tees will convene twice a year and
are meant to be most effective ins-
truments in maximizing the efficacy
of the actions undertaken by the
association. For example, the
Evaluation comitee will be expec-
ted to audit evaluation centers and
issue “methodological labels” that
will be the guarantee that every
evaluation approach reaches the
highest requirements of reliability
and quality. The Training comitee,
for one, will be expected to audit
training centers and deliver agree-
ments.
A viable and productive
growth
ARGOS’ members sitting on the
board, and who may or may not sit
on the various committees, will
naturally add to global cohesion.
Intercommittee informatory circu-
lars and Argos’ Web site will also
make for an easier two-way flow of
information. Transcommittee coun-
cils may also be contemplated at a
later stage. ARGOS, a scientific
society with a global vision, has
now reached maturity and come
into its own with unique resources
to allow clinicians and researchers
to take an active part in the global
sharing of views on the issues of
spine surgery. It is time the asso-
ciation shifted towards an organi-
zational framework better suited to
and consistent with the
specificity of its goals. Only then
will it derive full benefit from the
scope of it members’ expertise and
enjoy a viable and productive
growth. ■ AT.

Organization chart
Christian
Mazel, MD
President
Jean-Paul
Forthomme, MD
Vice President
Alexandre
Templier, Msc, PhD
General manager
Pierre
Kehr, MD
Executive secretary
Alain
Graftiaux, MD
Treasurer
Communication committee
Training committee
Evaluation committee
Wafa
Skalli, PhD
President of the
committee
Jacques
De Guise, PhD
Michel
Dutoit, MD
Alain
Graftiaux, MD
Christian
Mazel, MD
Juan Antonio
Martin, MD
Henry
Judet, MD
Philippe
Bedat, MD
Pierre
Kehr, MD
Charles-Marc
Laager
Jean-Paul
Forthomme, MD
Henri
Costa, MD
Jean-Paul
Steib, MD
President of the
committee
Jean-Paul
Forthomme, MD
Franck
Gosset, MD
François
Lavaste, PhD
Richard
Terracher, MD
Jean-Marc
Vital, MD

Thank you for your contribution !
we will see you next year…

ARGENTINA
Dr. Yvan R. AYERZA
Dr. Juan Pablo BERNASCONI
Dr. Boan OSVALDO FERNANDEZ
Dr. Frederic J. GELOSI
Dr. Felipe Zubiaur LANARI
Dr. Carlos Aroldo LEGARRETTA
Dr. Luis A. PATALANO
Dr. Pablo PLATER
Dr. Victor G. RAMANZIN
Dr. Gustavo RAMIREZ
Dr. Gabriel ROSITTO
Dr. Victor ROSITTO
Dr. Tomas RÜDT
Dr. Eduardo SEMBER
Dr. Carlos A. SOLA
Dr. Gustavo Roberto ZISUELA
BELGIUM
Dr Henri COSTA*
Dr. Guido DELEFORTRIE
Dr. Damien DESMETTE*
Dr. Sabri EL BANNA*
Dr. Jean-Paul FORTHOMME*
Dr. Jean LEGAYE
Dr. Frédéric MATHEI
Dr. Yves RYSSELINCK
Dr. Pierre SOETE*
BRAZIL
Dr. André Rafael HÜBNER
CANADA
Pr. Jacques DE GUISE
CHINA
Pr. John LEONG
FRANCE
Dr Joseph ABIKHALIL
Dr. Michael ALBERT
Pr. Claude ARGENSON
Dr. Xavier ARTIERES
Dr. Mohamed Kamel BENCHENOUF
Dr. Robert BOUVET
Dr. Ilhem CHERRAK
Pr. Denis CORDONNIER*
Pr. Alain DEBURGE
Dr. Jean-François DESROUSSEAUX*
Pr. Jean-Claude DOSCH
Dr. Brice EDOUARD
Dr. Gilles GAGNA
Dr. Franck GOSSET*
Dr. Alain GRAFTIAUX*
Pr. Pierre GUIGUI
Dr. Michel GUILLAUMAT
Dr. Pierre HEISSLER
Dr. Henri JUDET*
Pr. Pierre KEHR*
Pr. François LAVASTE*
Dr. LEONARD
Pr. René LOUIS
Dr. Jean-Luc MARMORAT
Dr. Christian MAZEL*
Pr. Serge NAZARIAN
Pr. Michel ONIMUS
Dr. François PODDEVIN
Dr. Olivier RICART
Pr. Gérard SAILLANT
Pr. Jacques SENEGAS
Dr. Wafa SKALLI*
Dr. Joël SORBIER*
Pr. Jean-Paul STEIB*
Dr. Alexandre TEMPLIER*
Dr. Richard TERRACHER*
Pr. Jean-Marc VITAL*
GERMANY
Dr. Ferdinand KRAPPEL
Pr. Andreas WEIDNER
GREECE
Pr. Demetre KORRES*
HUNGARY
Dr. Tamas ILLES*
ISRAEL
Dr. CASPI
ITALY
Dr. Flavio BADO
Dr. Paolo BONACINA
Dr. Luigi CATANI
Dr. Vincenzo DENARO
Mr. Charles-Marc LAAGER*
Dr. Tonino MASCITTI
Pr. Giovanni PERETTI*
Dr. Carlo PIERGENTILI
Dr. Dario RODIO
Dr. Michele Attilio ROSA
JAPAN
Dr. Kiyoshi KUMANO
Dr. Jun-Ichi KUNOGI
LUXEMBOURG
Dr. Adrien WIJNE*
THE NETHERLANDS
Dr. Willem F. LUITJES
PORTUGAL
Dr. Luis DE ALMEIDA
Dr. Joao CANNAS
ROMANIA
Dr. Mihai JIANU
SENEGAL
Dr. Seydina Issa Laye SEYE
SOUTH AFRICA
Dr. Johan WASSERMAN Honeydew
SPAIN
Dr. Fernando ALVAREZ RUIZ
Dr. Diego BRAGADO NAVARRO
Dr. Sergio CABRERA MEDINA
Dr. Alfonso CAMPUZANO
Dr. J.M. CASAMITJANA FERRANDIZ
Dr. J. Ignacio CIMARA DIAZ
Dr. Jose Maria CORBOCHO GIRONES
Dr. Alvaro DE BLAS ORLANDO
Dr Jose Antonio DE MIGUEL VIELBA
Dr. Angel Jorge ECHEVERRI BARREIRO*
Dr. Manuel FERNANDEZ GONZALES
Dr. Fernando FERNANDEZ MANCILLA
Dr. Luis Antonio GARCIA
Dr. Antonio GIMENEZ
Dr. Francisco GONZALES
Dr. Ernesto GONZALES RODRIGUEZ
Dr. Angel GONZALEZ SAMANIEGO
Dr. Cesar HERNANDEZ GARCIA
Dr. Carlos HERNANDO ARRIBAS
Dr. Juan HUERTA
Dr. Alberto ISLA GUERRERO
Dr. Manuel LAGUIA
Dr. Rafael LLOMBART AIS
Dr. Juan Antonio LOZANO-REQUENA
Dr. Carlos LUNA
Dr. Antonio MARTIN BENLLOCH*
Dr. Jose Ignacio MARUENDA
Dr. Cesar PEREZ JIMENEZ
Dr. Enrique RODA FRADE
Dr. Manuel SANCHEZ VERA
Dr. Hugo SANTOS BENITEZ
Dr. Jose Luis SOPESEN MARIN
Dr. Agustin VELLOSO LANUZA
Dr. Javier VICENTE THOMAS
Dr. Julio Alfonso VILLAR PEREZ
SWITZERLAND
Dr. Philippe BEDAT*
Pr. Michel DUTOIT*
Dr. Bernard JEANNERET
Dr. Denis KAECH
Pr. Thierry SELZ
SYRIA
Dr. Taha ALOMAR
TUNISIA
Dr. Mohamed Habib KAMOUN
Dr. Mondher M'BAREK
Dr. Mongi MILADI*
UK
Dr. Constantin SCHIZAS
USA
Dr. Fabian BITAN*
Pr. Jean-Pierre FARCY*
Dr. Eric JONES
Dr. David LANGE
Pr. Joseph MARGULIES
Dr. William RODGERS
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Argos’ members list
* full members being entitled to sponsor

T
he LBM-
ENSAM (Biome-chanics
Laboratory of the Ecole
Nationale Supérieure d’Arts &
Métiers in Paris), directed by
Professor LAVASTE who began his
first in vitro experiments with
Professor ROY-CAMILLE in 1972,
is today one of the most important
biomechanics research centers in
the world. Its works on in vitro
experiments, numerical modeling
and morphological & functional in
vivo measurements, are applied to
the study of Spine, Knee, Hip,
Shoulder, and generally to the
whole skeleton including muscles
and ligaments. The LBM, affiliated
member of the CNRS (French
National Center for Scientific
Research), got the European
COFRAC certification concerning
In Vitro testing of spinal implants.
Five years of research (1995-2000),
achieved in collaboration with five
of the main French Spinal surgery
departments, allowed the LBM-
ENSAM for a comprehensive ana-
lysis of methods & parameters for
spinal implants evaluation. The
active and sustained involvement of
this laboratory in the International
Standard Organization conventions
of the Technical Committee 150
(Osteosynthesis, chairman : John
Kirkpatrick - USA, secretary : Mark
Melkerson - USA) as official repre-
sentative of the AFNOR, allowed it
for bringing its contribution to
works led by the ASTM
(American Society Testing for &
Materials). (Including the
Corpectomy test method described
by “Cunningham”, see figure 1).
The LBM is today responsible, on
decision of the countries represen-
ted in the ISO TC 150, for the wri-
ting of a complementary standard
on functional testing of spinal
implants.
After this preliminary period, vali-
dation, synthesis and writing of this
standard has still to be done. To do
so, the LBM-ENSAM is currently
preparing a project involving indus-
trial partners interested by contri-
buting to this work, with the help of
the French ministry of Economy,
Finances and Industry.
Eurosurgical, Scient’x, Medtronic,
Euros, Stryker, Sulzer, Kisco, LNE,
CRITT Champagne-Ardennes, CEA
and AFNOR have already applied to
be involved in this project.
The LBM-ENSAM invites the pos-
sible sponsors and private partners
interested by this project to take
contact with the LBM at:
(33) 1 44 24 63 64 (tel),
(33) 1 44 24 63 66 (fax).
The next meeting of the ISO
TC150 will take place to
Stockholm (Sweden)
from September 11th to 25th 2000
Evaluation
Figure 1
Functional testing of
spinal implants :
An ISO TC150 New Work Item
Professor François Lavaste

table, a radiographic film proces-
sing software has been recently
developed by Claude Kauffmann,
Benoît Godbont and Adib Ben
m’Barek (Laboratoire de recherche
en Imagerie et Orthopédie – LIO –
of Montréal), as suggested by
Jacques De Guise, Director of the
LIO. This software, called
Spineview, offers the same preci-
sion of measurement and the same
reliability as the manual protocol
(for example, precision of ± 1.5° for
intervertebral rotations).
For the user, the first step consists
of digitizing x-rays with a scanner.
Digital images can then be integra-
ted into the patient's file, or stored
independently on a database such
as ARGOS Clinical Follow-up
Database. Two possibilities are
available at this stage: either direct
on site data processing using a com-
puter, or transfer of data by E-mail
to our processing laboratory, which
will return the results after analysis.
Centres not equipped with digital
image acquisition systems can also
send x-rays by mail: they will be
returned to the hospital department
with the results of computerized
processing.
was possible to define a standard
protocol allowing the acquisition of
15 dynamic and postural parame-
ters under uniform and reprodu-
cible conditions: a long axis lateral
film, including C2 and the femoral
heads, to quantify pelvic and spinal
parameters (sacral angle, pelvic
tilt, total inclination of the spine,
etc.); two lateral lumbar dynamic
films (flexion-extension) to measure
the amplitude of intervertebral
sagittal rotation and to locate the
mean centres of rotation. This pre-
cise measuring technique was pre-
sented by Alexandre Templier at
the last SOFCOT meeting in Paris
(preliminary multicentric study
designed to validate the principle of
this protocol and to evaluate its
potential).
Initially performed on a digitizing
E
very surgeon must critically
examine the sound basis of
the treatments proposed to
patients. But is he really equipped
to analyse the technical perfor-
mance, security and benefits rela-
ted to the use of a given technique
in comparison with the available
alternatives? Using lumbar verte-
bral instrumentation as an example,
regarding to the diversity of
implants and associated surgical
techniques, the credibility of this
approach must be based on a rigo-
rous and explicit method designed
to objectively assess and compare
the efficacy of the various strategies
proposed.
Be easily integrated into rou-
tine clinical practice
Although some authors have pro-
posed useful quantitative anatomi-
cal parameters, a simple and com-
plete protocol allowing quantitative
analysis of anatomical, postural and
kinematics parameters in patients
undergoing lumbar fusion has not
been available to date. With an
extensive experience in modelling
and statistical analysis, the ENSAM
biomechanics laboratory of Paris
(LBM), in close collaboration with
five major French spinal surgeons
(Pr. Dubousset, Dr. Mazel, Pr.
Passuti, Pr. Saillant, Pr. Vital), has
invested in the development of a
clinical and radiological protocol
which can be easily integrated into
routine clinical practice, through
the PhD Thesis of Alexandre
Templier, directed by Dr. Wafa
Skalli, co-director of the LBM.
With a few minor adjustments of
the procedures generally used in
each of the participating centres, it
Spine view :
a tool designed to improve
diagnosis & follow-up
Evaluation
Postural analysisDynamic analysis
Rough delineation of vertebral body contour
Automatic vertebral body contour
Automatic registration between the flexion
and extension vertebral body contours
Numerical calculation of dynamic
and postural parameters

Complete dynamic and postu-
ral analysis takes only 10 to
15 minutes.
Postural analysis simply consists of
digitizing the usual anatomical
landmarks (to ensure greater preci-
sion and to facilitate these measu-
rements, geometrical elements
have been introduced into this
digitization step). Dynamic analysis
consists of clicking on several
approximate spots around each ver-
tebral body, on flexion and exten-
sion films. A processing algorithm
(outlining and superimposition
technique designed at the LIO in
Montréal) then automatically and
precisely determines the exact
contour of the vertebral bodies, and
deduces the dynamic parameters.
At each step of the process, the user
is able to qualitatively control auto-
mated processing of digital data and
the plane of visualization of the x-
rays. For example, the film super-
imposition function allows manual
correction of an unsatisfactory auto-
mated result. Complete dynamic
and postural analysis takes only 10
to 15 minutes.
Preoperative parameters determi-
ned in this way can provide a real
aid to diagnosis. Analysis of post-
operative assessments in the light of
this quantitative information could
also be very useful for patient fol-
low-up, particularly for the analysis
of any complications. Other poten-
tial applications would be analysis
of the influence of the type of ins-
trumentation on the residual mobi-
lity of fused segments, evaluation of
the mobility of segments adjacent
to the fusion, and diagnosis of non-
union or hardware failure.
Assessment of correlation between
posture and intervertebral mobility
would be another possible line of
investigation. With this tool, the
concept of the mean centre of
intervertebral rotation, a theoretical
parameter proposed by Pearcy in
the 80’s only accessible, up until
now, to researchers, would acquire
a greater field of clinical applica-
tion. Now that this parameter is
more readily accessible, it would
not be unrealistic to imagine that
this concept could soon become an
index of disc “instability” even-
tough the concept of spinal “insta-
bility” has still to be clarified.
To further develop integrated com-
puter management, Spineview has
been linked with the ARGOS
Clinical Follow-up software. For
the purposes of comparison, inte-
gration of parameters related to dia-
gnosis, surgical procedure and
postoperative course, as well as
quantitative postural and dynamic
data, should greatly improve the
level of scientific evidence for the
conclusions formulated in studies.
a valuable tool for retrospec-
tive and medicolegal assess-
ment
Although there is still room for
improvement, this method consti-
tutes a real progress in the search
for better assessment of the
patient's condition and the proce-
dure performed, and represents a
source of information with an enor-
mous potential. This tool also
makes a considerable contribution
to medical device vigilance sys-
tems, as it meets precision and rele-
vance criteria which should make it
a valuable tool for retrospective and
medicolegal assessment. If a large
number of scientists and hospital
surgeons adopt this common refe-
rence, our speciality will have a real
chance of conducting studies in
which the clarity of the objectives,
the rigorous methodology and the
practical value of the results will
help to further our knowledge of
spinal fusion. ■ PS.

5TH
Internationa
Argos me
FRIDAY JANUARY 26TH 2001, PARIS - MAISON DES ARTS
A spine

l
eeting
S & MÉTIERS - 9BIS AV. D’IENA PARIS XVI
odyssey

F
or any association who wants
to achieve global reach, the
Internet is the only way to go.
ARGOS SPINE NEWS, the official
journal of the ARGOS association,
is proud to announce the launch of
its electronic counterpart: the
ARGOS Web site.
It is now available at www.argos-
europe.com, and reflects ARGOS’
commitment to active and efficient
communication.
Easy point-and-click access
This site is in English and is desi-
gned to supply information to our
members and to introduce our
association. It is fast and convenient
to use, and lets the user access
information on our services and
products.
There is also a presentation on
ARGOS’ mission and the composi-
tion of its committees.
The user can also search through
a database for events in orthope-
dics, and browse through the list of
the articles in ARGOS’ scientific
library. The site also features
easy point-and-click access to the
best sites with extensive spinal
surgery focus. Soon to be added,
which will make it a truly interac-
tive site, will be the discussion
forum.
Even though separated by vast
geographic distances, users will
communicate and exchange infor-
mation freely and expediently,
which is one of the foundations of
Argos’ existence.
An ever-improving medium.
The ARGOS site is intent on
remaining an ever-improving
medium. Your opinions and sug-
gestions to improve our efficiency
are welcome and desired. Please
send them to the following address:
contact@argos-europe.com
PS.
The Launch
of Argos’ Web site :
http://www.argos-europe.com
Communication

Spine-health gives very detailed
information on spinal pathologies
and related subject, such as dia-
gnosis, surgical techniques and
manual therapy. Articles include
thumbnails you can click on to get
full screen pictures.
www.srs.org
The SRS site is an institutional site
and presents research on scoliosis.
It includes a great deal of informa-
tion on varied pathologies : you may
find detailed glossaries as well as
search browser on medical articles.
www.espine.com
The Medical Doctors as individuals
also offer high quality home pages of
quality as this site demonstrates by
being devoted to practitioners and
patients. Comprehensive information
about spinal surgery is presented in a
very simple way. The interface is
well-spaced, clear, and pleasant. ■
deph definition. You will also find
the agenda of congresses and have
possibility to subscribe to the mai-
ling lists of differents specialities.
the home page is clearly composed
with an English/French interface.
www.orthogate.org
A must-see site as far as classifica-
tion and referrencing are concer-
ned; you will also have access to a
fabulous list of links. From institu-
tional sites to internationnal news
groups, every category is listed.
The interface is multilingual, the
presentation is user-friendly and
the loading is fairly fast.
www.spine-health.com
www.orthopedie.com
As complete as possible, this site
provides you with a series of detai-
led clinical cases that you can dis-
cuss on the forum. You can also buy
books and videos or find several
useful services. the screen display
is fast although we regret a certain
austerity in the interface.
www.maitrise-orthop.com
The site is composed of various
interviews, case studies and medi-
cal glossaries, the mass of informa-
tion is presented in an encyclopae-
dic manner : outstandingly
illustrated, numerous medical
explanations, glossaries and in-
Web Review
T
he orthopedic surgery is presented on the internet in various
forms. From academics institutions to enthusiastic medical
practitioners, but also through commercial sites, you will
have access 24 hours a day, to data, services and products. To
save time, here is a selection of links taking into account the
content, presentation, and downloading time.

S
pine surgery and, conse-
quently, its history would
have been very different if
Man had not evolved to a standing
position and subsequently imposed
many different deformations to his
spine. As a consequence of the
interest these deformations and
pathologies always aroused, here is
an opportunity to draw links bet-
ween more or less famous charac-
ters who contributed to the deve-
lopment of orthopedics in general,
and to the study of the spine, in par-
ticular.
Edwin Smith’s Papyrus is known as
the oldest surgery treatise. This
Egyptian papyrus was written in
2645 B.C. by Imhotep, a well-
known architect who designed the
step pyramid in Saqqara. He des-
cribed in it 48 different bone
lesions. Tutankhamen
(1361 -1343 B.C.)
personally contri-
buted in a way to our subject. The
X-ray of his mummy taken by J
E Harris in 1944, revealed
the first cervical laminec-
tomy performed in his-
tory, but the therapeutic
reasons for this opera-
tion are yet unknown.
This pathology may
be associated to the
murderous inten-
tions of a rival to the
throne as one of the
assumptions made
regarding the cause
of his death.
The Greeks as
Alcmaeon (approxima-
tely 500 A.D.), a physician
at the academy of Croton
and disciple of Pythagoras
and who detected canals acting
as links between the organs and the
brain of Man, were intrigued by
those facts. However, the best
known of them all undoubtedly
remains Hippocrates (460-
377 B.C.). The author of
the Corpus Hippo-
cratum associated
the prognosis of
some spinal gib-
bosities with the
lungs. To correct a
few deforma-
tions, he sugges-
ted a dual trac-
tion on the
shoulders and
the legs associa-
ted to a tension that was sometimes
exercised as the practitioner sat on
the hump. The patient was lying
down on a Scammon equipped
with hoists and pulleys. It was a
very early ancestor of our modern
frames. In Rome of the Second
Century after Christ, Galen (131-
201 A.D.) updated the location of
the 4th cervical vertebra at the level
of the medullary core of the dia-
phragm. The fact that he was the
physician in charge of arenas and
gladiators must have facilitated his
investigations.
Evaluation
History of
spine surgery
From an article by R. Roy-Camille

These informations,
the bibliography or
available on
the Website…
The work of the 'elders' influenced
medieval scholars. The oldest sur-
gery treatise known in Western
Europe, the Rogerine, dates back
to the 12th century and includes
Roger of Parma comment about
Traumatology and gave a descrip-
tion of nascent anaesthesiology.
In Bologna and later on, in Verona,
William of Salicet (1210-1277) des-
cribed in a surgical technique trea-
tise the portals of entry to the limbs
and the different types of post-trau-
matic paraplegia. Let us not forget
the essential role Arab medicine
played in those times however the
sole mention made to vertebral sur-
gery is found in At-Tasrif (Practices)
published by Abulcasis who lived
and worked in the heart of the cos-
mopolitan Cordoba.
Later on, surgeons began to leave
Italy in the wake of the Guelf-
Ghibelline wars and many immi-
grated to France. Guido Lanfranchi
published his Chirurgia Magna
Practica in Lyon in 1296 and des-
cribed neurotomy for recurring
pain.
Many who rediscovered
Hippocrates during the
Renaissance followed his example
and devised instruments intended
to correct vertebral deviations.
Ambroise Paré (1509-1590), the
most remarkable of them all, contri-
buted extensively to spine surgery.
In his complete works published in
1575, the author surprised us all in
a chapter entitled On fractures of
vertebrae or spine wheels and their
apophyses or projections. He defi-
ned traumatic paraplegia and sug-
gested an operative procedure but
no record of its application exists.
His influence may explain
Garrison's remark: “until (…) the
second half of the 18th century, sur-
gery was completely in the hands of
the French in Paris”. Thus, the
word 'orthopaedics' was coined by
Nicolas André in his Orthopaedics
or the art of preventing body defor-
mation in children published in
1741. On a lighter note,
Dupuytren's bimalleolar fracture is
known in English-speaking coun-
tries as Percival Pott (1714-1788)
fracture. Although Pott described
this fracture accurately, his contem-
poraries mainly remembered that
he suffered from it. It was not until
Jacques Mathieu Delpech publi-
shed his results in Montpellier in
1816 that Pott's disease was in fact,
established as vertebral tuberculo-
sis.
Hippocrates had already described
the association existing between
simple deviations of the spine and
tuberculosis, but the modest
advances made in the 18th century
cannot be ignored. Bloodless sur-
gery with soft and progressive ver-
tebral reduction techniques was
recommended. The work of the
Levacher brothers (1732-1816 and
1738-1790 respectively) and André
Venel (1740-1791) illustrates this
evolution which the nursing homes
of that period benefited success-
fully from.
The enthusiasm raised by Sciences
and Technologies from the 19th
century onwards intensified the
rate of discoveries. It was a revival
for spine surgery. Although R. Roy-
Camille's paper mainly deals with
contemporary history, let us quickly
mention Boehler and his role in the
orthopaedic treatment of spine
trauma, Harrington whose rod
revolutionized the treatment of
scoliosis in 1961 etc.
This retrospective is a sketch of the
history of spine surgery that under-
lines the importance of individual
as a guide. An intellect whose ini-
tiatives are promulgated to advance
and circulate his ideas amongst dis-
ciples who are sometimes won
over by his charisma. In that the
physician is different from the engi-
neer who often works under secret.
Still, no matter how rich his ideas
are, he must confirm his intuitions
with evident facts to establish the
level of confidence that is the hall-
mark of fruitful exchanges.. ■

Introduction
Current surgical treatments of spinal disorders are
made with various anterior and/or posterior instru-
mentation combined with different surgical tech-
niques. The majority of existing segmental instrumen-
tation is represented by multi hook-wire-screw and
rod systems (1), in order to reach the two main goals
of the spinal surgery: the surgical correction and the
surgical stabilization. The combination of these
implants enable to realize constructs for which mecha-
nical properties are essentially defined by the dimen-
sions of the rod and the chosen material (specified by
the ASTM and ISO standards (8)). This is the reason
why this article will focus on the rod characteristics.
Surgical considerations
Rod characteristics are especially important in spinal
deformation surgical treatments. During this type of sur-
gery, there are two main stages: contouring of the rod
and correction of the spine. Different techniques are
available, using the rod as inductor of correction:
rotation technique, translation technique and in situ
contouring technique (3, 4, 5, 6).
For rotation and translation technique (first group), the
rod is contoured to the profile desired for the correction.
On the opposite, the in situ contouring group needs mul-
tiple contourings of the rod, firstly for insertion,
secondly for correction. Considering these features, the
characteristics of the rod for the two groups can be dif-
ferent. For example the malleability of the rod needs to
be rather low for the first group. For in situ contouring
group, malleability needs to be higher.
If these specifications are not respected, some troubles
may appear : for the first group, if the malleability is too
high, the rod can be unintentionally deformed during
correction. For the in situ contouring group, if the mal-
leability is too low, large bending actions may therefore
follow the contouring of the rod and as a consequence be
responsible for an overstress on the spine.
So, the choice of the material for the rod is very impor-
tant regarding the technique used for the spinal defor-
mation surgery. As there are differences in tensile
strength, elasticity and plasticity among the different
available rods on the market, it is important that the
mechanical properties of the rod be understood and
taken into account prior to their use.
Biomechanical considerations
An important distinction must be made between several
terms which are often confused : Elasticity, Plasticity,
Rigidity, Stiffness, Malleability, Strength, etc... Before
going into details of the previous terms, it is necessary
to understand that the bending effort F on a rod and the
angular displacement α obtained follow a well-establi-
shed curve tense length (fig 1). On this curve, we will
find several zones and points to which a specific voca-
bulary is applied.
When the rod is working in its Elastic zone (F<Elastic
Limit Point Fe on Fig 2), the deformation appears to be
linear and is reversible. The material will revert to its ori-
ginal shape when the force is no longer applied. The
created deformation is not permanent and the rod
returns to its previous shape.
When the rod is working in its Plastic zone (F>Elastic
Limit Point Fe on Fig 3), the deformation appears to be
non linear. When the force is applied, the material will
first go through an elastic stage until the Elastic Limit
Point Fe is reached. Beyond this point, the material will
not return to its initial shape but goes to a new one when
the force is no longer applied.
The concept of Rigidity (or Stiffness) and Elasticity is
specific to the slope of the linear deformation. The stee-
per the slope, the higher the rigidity : you need a grea-
ter force to obtain a (non permanent) deformation. The
lower the slope, the higher the elasticity.
The Malleability of the rod is characterized according to
the importance of the plastic zone (fig 4). The larger the
Plastic zone is, the more malleable the rod is.
Mechanical characteristics
of the rod in spinal surgery
Importance of the proper rod
material choice
Evaluation
Emeric Gallard Msc Eng*,
Jean Paul Steib MD**,
Patrick Bertranou MD***,
Raphael Dumas Msc Eng*,
Alexandre Templier PhD*

30
The uses of a malleable rod does not affect rigidity of the
construct (on fig 4, the slope of the linear deformation is
the same for the two kinds of rods). A construct made with
malleable rod offers identical or superior stress resistance
than a construct made with standard rod and integrity of
the rigidity of the construct is preserved.
Caution : it is important to remember that reducing the
diameter of a rod is not the good solution to contour easier
the rod. Indeed, even if the forces applied to obtain a per-
manent deformation are lower (Fe’<Fe on fig 5), the elas-
tic return of the rod is higher (α’>α on fig 5). Moreover,
diameter reduction will lower the rigidity of the rod (the
slope of the linear deformation is lower).
What about surgery ?
Many surgeons use the in situ contouring technique in
association with other methods for spinal correction (2).
It is well documented (7) that when a rod with inadequate
mechanical characteristics is used for in situ contouring
manoeuvers, it has, due to the elastic return of the metal
deformation, to be bent well over the desired contour to
be achieved. Using such an inappropriate rod, the
maneuver creates an increased tension of the anterior lon-
gitudinal ligament (7).
The rods described and tested in the Bridwell (1) and Voor
(7) articles did not have the intrinsic characteristics neces-
sary to make them usable in the in situ contouring tech-
nique. These rods are either too strong (Isola system) or
very elastic with little or poor malleability (Moss-Miami
system / CD-horizon system). The author notes also that
in situ contouring technique should be performed with
malleable rods.
If the surgeon use a “standard rod”, the forces applied to
obtain a deformation will be stronger and the displacement
will have to be exaggerated to achieve the desired contour
(fig 6a), because a force superior to the Elastic Limit Point
Fe is required. If the surgeon use a malleable rod, the forces
and deformations required to achieve the same deformation
will be lower (fig 6b), because it is easy to go over the Elastic
Limit Point fe. The detrimental over-bending effect αover is
minimized and soft tissues are preserved.
F [N]
Elasticzone
α [°]
Plastic zone =
permanent deformation zone
Breakagezone
Elastic limit point
Breakage limit point
= strength
αfinal = 0
F [N]
Fe
α [°]
▲ Figure 1
▲ Figure 2
αfinal ≠ 0
F [N]
Fe
α [°]
▲ Figure 3
F [N]
Elasticzone
α [°]
Plastic zone =
permanent deformation zone
Breakagezone
Elastic limit point
Breakage limit point
= strength
F [N]
Fe
α [°]
Fe’
α’α’
Ø reduction only (same material)
▲ Figure 5
▲ Figure 4

Conclusion and perspectives
When performing the in situ contouring manoeuver with
a “standard rod”, an over bending movement will be nee-
ded to obtain the final correction. Doing so, it is impos-
sible to avoid strain and/or lesions to any soft tissues (e.a.:
neural structures, disks, ligaments) or bony structures (e.a.:
pedicle, lamina).
It could be dangerous to use a standard rod when in situ
contouring technique or a combination of techniques are
used by the surgeon to correct spine deformities. Our ana-
lysis concurs with the Bridwell and Voor conclusions, and
proposes to complete and document the use of the in situ
contouring technique by duplicating the tests with an
appropriate choice of materials adapted to the in situ
contouring technique.
Mechanical contouring tests are in progress on several
rods in order to quantify bending forces and angles, and
especially to quantify the over bending phenomenon and
its detrimental effects.
For in situ contouring technique (4, 5, 6), the proper rod
material choice and the diameter of the rod are essential. ■
Evaluation
References
(1) Bridwell KH :
Surgical treatment of idiopathic adolescent scoliosis. Spine
1999 Vol.24 (24) pp 2607-2616.
(2) Gennari JM, Tallet JM, Hornung H, Bergoin M :
The treatment of idiopathic scoliosis in adolescents : rota-
tion or in situ bending ? European Journal of Pediatric
Surgery 1997 Vol.7 pp 353-360.
(3) Jackson RP :
Intrasacral fixation and in situ contoured spinal correc-
tions. Spine State Art Rev 1996, 10, 561-86.
(4) Steib JP, Averous C, Lang G :
Traitement chirurgical des scolioses par deux techniques de
correction différentes. Presented at the Groupe d’étude de la
scoliose 26th Annual Meeting, March 1995, Dijon France.
(5) Steib JP :
Les “nouveaux” systèmes d’instrumentation rachidienne
postérieure : l’instrumentation SCS. Cahiers d’enseignement
de la SOFCOT : instrumentation rachidienne 1995, 53, 229-
235
(6) Steib JP :
Spine Contouring System in lombosacral arthrodesis. In :
Margulies JY et al, Lomboscral and spinopelvic fixation.
Lippincott-Raven Publishers ed, Piladelphia, 1996, 421-430
(7) Voor MJ, Roberts CS, Rose SM, Glassmann SD :
Biomechanics of in situ rod contouring of short segment
pedicle screw instrumentation in the thoracolumbar spine.
Journal of Spinal Disorders Vol.10 (2) pp 106-116.
(8) ASTM F67 and F136/ISO 32-2 and 5832-3 for
Titanium. ASTM F138/ISO 5832-1 for Stainless Steel.
▲ Figure 6a
▲ Figure 6b
F [N]
fe
α [°]
αoverαfinal
F [N]
Fe
α [°]
αoverαfinal
LOW ELASTIC RETURN
Respect of soft tissue
Less stress on implants
Intermediate deformation needed
with a malleable rod
HIGH ELASTIC RETURN
Risk of high stress on screw
combined to injury on soft tissue
Intermediate deformation needed
with a standard rod

News
Communication
A first special session devoted to dynamic spinal fixation, a mini-congress organized into
conferences, workshops, and experience-sharing meetings, was organised in Tokyo last March by
Dr. Kunogi and his colleagues. This first meeting was a great success. Another meeting was also orga-
nised in Buenos Aires (Argentina) at the end of September 1999 by Pr. Ayerza,
Dr. Ramirez and Dr. SOLA. It focused on the dynamic spinal osteosynthesis
and the in situ contouring technique in the treatment of scoliosis through
a tribute to Pr. Roy Camille, with Dr. Mazel and Pr. Steib as guest speakers.
Other sessions are planned for 2000, again in Tokyo, and potentially in
Spain, which would foster ARGOS’
cross-border expansion.
Dr. Kunogi Pr. Ayerza Dr. Ramirez
Worldwide expansion
Argos training programs
From our web site at www.argos-
europe.com surgeons will be able to
choose from the various official
training centers and obtain indivi-
dually adapted programs. Such trai-
ning will focus on: medical exami-
nations, analysis of case reports, real
surgical procedures, simulations of
surgery on synthetic models, theo-
retical training and personalized
assessments on CD-ROM (surgical
techniques, biomechanics, methods
and tools for diagnosis and clinical
follow-up). Surgeons will then be
given comprehensive training in
spinal surgery.
PGT (Post-Graduate Training)
A meeting intended for General
Practitioners entitled “Lumbosacral
pathologies and their surgical treat-
ment” was held on the initiative of
Dr. PETCHOT in Cergy Pontoise
(France) on May 5th, 1999. Some
fifteen practitioners followed the
training program divided into three
successive lectures, from 8:30 to
10:30 p.m. A similar meeting was
organized by Dr. HECKEL in
Saint Avold (France) on October
15th 1999. These Post-Graduate
Training sessions have proved to be
very efficient in informing General
Practitioners about the latest
advances in spinal surgery.
Argos Spine News
The next issue of our journal is
scheduled for release on
September 30th. Any article
concerning our association or focu-
sed on research in spinal Surgery or
Biomechanics would be most wel-
come. ARGOS SPINE NEWS is
first and foremost a communication
tool allowing ARGOS members to
share their views straightforwardly
on issues that they feel strongly
about. The journal has a worldwide
circulation of over 7,000 copies,
which contributes to both impro-
ving internal communication and
broadening the association’s reach.
Eurospine 1999
ARGOS has a global vision and
takes an active role in various inter-
national scientific events.
One of these was the EUROS-
PINE congress that took place in
Munich (7th-11th September
1999), where ARGOS presented
some of its Communication,
Training, and Assessment activities
(Internet site, Journal, Spine sur-
gery, Synthetic models, Clinical
database), and the outcomes of our
partnerships (Spine View, current
research studies). This meeting
was another opportunity for
ARGOS to be present at interna-
tional level and to increase its
influence with a large audience.
Website
ARGOS has moved onto the
Internet and now is available on
http://www.argos-europe.com.
Please send any comments or sug-
gestions to:
contact@argos-europe.com

A
Biostatistics department was
recently founded by
ARGOS. The move called
for the recruitment of a PhD in
Biomedical computer engineering.
Mrs Ilhem Cherrak is expected to
set up and develop Biostatistics
skills of ARGOS research projects.
Beside this, she will also coordi-
nate and manage ARGOS’ clinical
data collecting network. In charge
of developing the use of compute-
rized evaluation tools (databases,
software programs for quantitative
analyses, developed in collabora-
tion with our research partners),
she will routinely synthetize the
body of clinical data available via
morbidity reports on the various
surgical techniques covered by the
collecting network. She may
moreover be involved in various
research projects initiated by the
Biomechanics Laboratory that
entail collecting and doing a survey
of the available clinical data.
Responsible for the integrity and
consistency of the data managed by
the association, she will also be
expected to insure that the out-
comes of the research work trans-
late as long as possible to the ope-
rational evaluation tools ARGOS’
network makes everyday use of.
With the creation of this depart-
ment, ARGOS has knitted together
the total skills and expertise requi-
red for a top-level partnership with
the clinical disciplines. As an inter-
disciplinary approach, Biostatistics
should be an exciting prospect
future research work in Spine
Biomechanics. ■ AT.
When biomechanics
interfaces with statistics
Evaluation

These informations,
the bibliography or
available on
the Website…
T
he purpose of this study
(which began in 1995, with
the Ph.D. Thesis of Pol
Leborgne, directed by Mrs. Skalli,
and Mr. Lavaste in conjunction
with the Saint Vincent de Paul
Hospital – Paris – (Pr. Dubousset
and Dr. Zeller), performed in the
Biomechanics Laboratory (LBM) of
the ENSAM* Paris, in collabora-
tion with the Ecole de Technologie
Supérieure de Montréal (Jacques
De Guise), the Ecole Polytechnique
de Montréal (J.Dansereau, C.E
Aubin, Y Petit), and the Hospital
Sainte Justine de Montréal (H.
Labelle, J. Joncas), was to stimulate
surgical correction of scoliosis by
rod de-rotation using a personali-
zed Finite Elements Model for a
given scoliotic patient in order to
help surgeons who look forward
optimized method (distraction and
compression, translation towards a
fixed rod or rotation of the rod,
etc…) to optimize their operative
strategies. This work
was co-sponsored by the French
ministry of Education & Research
(MENESR), Sofamor-Danek, The
“Franco-Quebecoise” Association,
and The Claude Bernard
Association.
Personalized geometry was obtai-
ned with a pair of Stereo X-rays
using a specific technique: 3D
reconstruction of corresponding or
non-corresponding points (anato-
mic landmarks viewed only on one
of the two X-rays). Geometrical data
was used to build a 3D Finite
Elements model, including rib cage
and pelvis. Mechanical characte-
ristics were fitted for a given
patient using bending tests: cadaver
experimental characteristics of soft
issues were altered locally or regio-
nally until the model renders the
functional unit’s behavior. De-rota-
tion surgery was simulated in
4 steps: 1- Simulation of patient
prone on the table with traction.
2- Modeling of the rod - rigid links
were considered between hooks or
screws and vertebrae simulating
pedicular or laminar connection
while taking into account sliding
between connecting elements and
rod. 3- Rod insertion on the screws
or hooks. 4- Rod de-rotation around
a moving axis.
For compliance evaluation of the
FE Model, the 3D per-operatively
measured displacement of T1 ver-
tebra was imposed as a boundary
condition (step 1). The 3D geome-
try of the implant was measured
during surgery (step 2). In the same
way, rod displacement was measu-
red during per-operative rod “rota-
tion” (step 4). Finally, vertebral
bodyline and vertebral angulation
were calculated at each step and
compared to per-operative measu-
rements obtained with an opto-
electronic device. For mechanical
personalization, differences bet-
Finite elements
simulation of scoliosis
surgical treatment
3D modeling using CAT scan :
1 - acquisition of numerous slices
2 - digital imaging processing
3 - 3D geometry reconstruction using the
SLICE-O-MATIC software (courtesy of
LIO Montréal)
3D reconstitution
using stereoradiography
Evaluation
1 2
3
3D reconstruction of a scoliotic spine using the SLICE-O-MATIC software
(by Champlain Landry PhD, LIO Montréal).

Stereoradiographies
Geometrical
models
<- Pre & post-op. ->
Peroperative
boundary
conditions
Simulation
results
Peroperative
measurements
EVALUATION
COMPARAISON
Personalized ->
finite-element
model
Global
approach
COMPARISON
CollaborationSOFAMOR/LBM
ween the personalized and non-
altered model reached 20 degrees
for Intervertebral mobility in axial
rotation. Differences between ste-
reo X-rays reconstructed vertebral
bodyline and the simulated one,
were less than 10 mm when mecha-
nical characteristics were altered.
Surgery simulation feasibility was
then assessed. At each step, diffe-
rences between per-operative
measurements and simulation were
always less than 10 mm for
vertebral bodyline (figure 2) and
less than 3 degrees for vertebral
orientations.
Scoliotic specific behavior can
be predicted using personali-
zed mechanical characteris-
tics in a Finite Elements Model.
The first validated results concer-
ning surgery simulation can make
us confident about perspectives.
The Finite Element analysis can
help surgeons to determine correc-
tion strategy and designers to opti-
mize implants. This approach is
currently being applied to the study
of the In Situ Contouring tech-
nique, through the Ph.D. thesis of
Raphaël Dumas at the LBM-Paris,
in collaboration with Pr. Jean-Paul
Steib (Strasbourg – France). We can
expect that this kind of comparison
tool will lead to better surgical
indications in the treatment of
scoliosis. ■ PL.
EJOST
(European Journal of
Orthopadic Surgery &
Traumatology)
The EJOST journal designed
and managed by Pr. KEHR,
ARGOS’ General Secretary is
published by Springer Verlag. It
is the ARGOS’ official scientific
communications tool. Initially
delivered to a limited number of
subscribers, EJOST now has
worldwide circulation of several
thousands. Springer Verlag also
provides that articles will soon
be available on databases such
as Medline.
ÉCOLE SUPÉRIEURE D’ARTS & MÉTIERS
Biomechanics laboratory
151, Bd de l’hôpital 75013 Paris
Phone 33 1 44 24 63 64 - Fax 33 1 44 24 63 66
In brief

Together with his team of researchers, Pr. Jacques A.
De GUISE, who is running the LIO, has got involved
in the Research and Development activities of the
BBRG (Biomechanics and Biomaterials Research
Group) of the École Polytechnique de Montréal, the
LIS3D** of the Hôpital Ste Justine, and the LIVIA***
of the École de Technologie Supérieure de Montréal
embarked on some years ago. The prime purpose of the
research work carried out has consistently been to
design applications clinical professionals can take
advantage of. But this outwardly complex network
merely reflects how close the collaboration clinicians
and engineers are working in actually is. Teams of
research engineers in hospitals typify the North-
American way of integrating technological and bio-
mechanical research into hospital facilities and logis-
tical support, a strategy that has unfortunately not
gained much ground in Europe.
The creation of the LIO is set in this genuinely global
approach. Engineering students in hospitals and
medical students getting to work in a technological
context close to their own environments is the gua-
rantee that both the training given to students and the
research work conducted in the laboratory reach the
highest requirements of quality and relevance. About
ten researchers and clinicians plus twenty university
students or so are currently working at the LIO.
The Montreal
Orthopedics
Introduction
The LIO was officially created in June 1997 as an extension of the
Research Center of the Montreal University Hospital Center (CR-
CHUM*)
* : CR – CHUM : Centre de Recherche du Centre Hospitalier de
l’Université de Montréal / Research Center of the Montréal Univ. Hospital.
** : LIS3D : Laboratoire d’informatique de la scoliose en trois dimen-
sions / 3D scoliosis Computing Laboratory
*** : LIVIA : Laboratoire d’Imagerie, de Vision et d’Intelligence
Artificielle / Laboratory of imaging, vision and artificial intelligence.
The LIO and ARGOS
As part of ARGOS’
commitment to go global and
promote research in spinal
orthopaedics, the association
is to forge links with the
leading international
laboratories in the field. The
privileged relations between
the LBM and the LIO have set
the stage for a first
partnership with ARGOS. They
decided to go it together with
the design of a software called
SPINEVIEW for computerized
quantitative analysis of spinal
dynamic and static
radiographs. Resulting from
the confrontation of two sets
of complementary skills and of
the relentless activities of
these two teams, the
SPINEVIEW software was
given the thumbs-up when
first presented at the last
ARGOS meeting.
We wish both these teams
all the glory they are
rightfully bound for !
(Laboratoire de recherche en
Imagerie et en Orthopédie : LIO)
SPECIAL FILE :
Focus on
Professor
Jacques De Guise

Activities
The LIO activities are about three thematics that fully
complement and build on each other, namely biome-
chanics/biomaterials, clinical research, and medical
imaging, run by Pr. L’Hocine YAHIA, Dr. Nicolas
DUVAL, an orthopaedic surgeon at the CHUM, and
Pr. Jacques De GUISE respectively. Such activities
extend beyond the scope of clinical research work to
contrive to be both clinically- (degenerative joint
disease, spine and knee surgery, arthroplasty of the hip)
and technically–oriented (2D and 3D processing of
medical images, artificial vision, 3D kinematic analy-
sis of the locomotive apparatus, surgical navigation, and
so on…). The LIO activities are also shaped by tech-
nological transfers and the pooling of skills and exper-
tise in such cutting-edge fields as the analysis of carti-
lage degeneration, knee ligament plasty, and functional
assessment of foot orthoses.
Besides, the partnership entered into by the Québec
research network and the French LBM run by Pr.
François LAVASTE and Wafa SKALLI (Biomechanics
Laboratory of the Paris-based ENSAM-CER) was
mainly centered on the spine, and notably the scolio-
sis. Quite a number of several-month exchanges bet-
ween students and researchers have already been
arranged every year for over 7 years now. Pr. Jacques
De GUISE has recently spent over 12 months conduc-
ting some research work at the LBM as guest profes-
sor (from June 1997 to July 1998). ■ AT.
Outlook
The LIO is expected to contribute to integrating and
consolidating the activities of researchers from a variety
of backgrounds (engineering, computer science, and
medicine) working in the field of orthopaedics. The
body of knowledge acquired over the last few years has
opened the way for a shift of research and development
focus to other issues raised by joint diseases:
• Automated analysis of dynamic and static radiographs
• Application of non-rigid registration by 3D elastic
deformation for modeling of the joint
• Biokinematic modeling of the knee using multibody
dynamic simulation
• Assessment of progression of degenerative joint
diseases and the effect of chondroprotective drugs by
3D MR imaging
• Assessment of osteoporosis and bone substitutes by
biplanar imaging
• Functional evaluation of ligament surgery
• Functional evaluation of hip surgery
• Computer-assisted design and evaluation of pros-
theses and orthoses
• Computer-assisted surgical maneuver
• Application of digital imaging analysis to telemedi-
cine. ■
Imaging and
research Laboratory
Training
Functional evaluation of ligament surgery

Communication
To promote applied research
in orthopaedic surgery.
This is the mission of ARGOS’
three partners (surgeons, biomedi-
cal researchers and industrialists).
The three orientations of the asso-
ciation, namely Communication,
Training and Evaluation, make for a
top-level synergy between all three
partners. This approach, which can
already be associated with a variety
of informational benefits, inclu-
ding various major events and
research projects, is now entering a
new phase with the creation of
foreign national ARGOS groups.
Officially set up in 1999, the
Belgium group now convenes on a
regular basis. The first Argentinean
Argos national congress, which was
held in September 1999 in Buenos
Aires was a real success, regarding
quality of scientific exchanges that
occured around a tribute to
Raymond Roy-Camille. Our japa-
nese collegues, who organized the
first Argos meeting in March 1999,
were also most successful in their
way to join together top-level scien-
tific contents with open-minded
and convivial ambiance. Spain, the
United States, South Africa and
Germany have all been conclusi-
vely approached, which bids fair to
lead, in due course, to the official
creation of a number of national
groups.
Why to create ARGOS national
groups ?
First and foremost, a national group
is a connecting link, the interface
between the ARGOS International
network and home orthopaedic
surgeons. National groups are
expected to contrive to both broa-
den the reach of the Association in
the home country along the three
basic orientations aforementioned
and bind ARGOS and home official
authorities (Department of Health
and Human Services, Department
of In-service Training and so on)
together. The groups have authority
to ask surgeons to more or less for-
mal seminars devised as true
forums for experiences (actual
national meetings are sometimes
held, as in Tokyo in March 1999
and Buenos Aires in September
1999). They are also expected to
foster the development of ARGOS’
projects (Internet site, journal, cli-
nical database, research, and so
on…) on the national level, in full
collaboration with the relevant
committees.
Just like virtual communities pop-
ping up everywhere on the
Internet, the ARGOS International
network is firmly geared to inte-
grate its partners into a cohesive
whole along a global set of opera-
ting rules that bolster information
exchanges. ARGOS is first and
foremost about interconnecting
people, with a reaffirmed commit-
ment to contacts and conviviality.
How to create and operate a
national group ?
The initiative and the procedure
followed for the creation of a natio-
nal group are left to the country. In
relation with and in agreement
with ARGOS International, natio-
nal groups gradually crystallize
around a few key members and
ARGOS’ basic commitments, lea-
ding within a few months to the
creation of a national group laun-
ched officially in full compliance
with national regulations, or just
launched regarding to the Argos
international network, which is the
most important. The official laun-
ching implies the defining of an
organizational structure topped by
a Board of Directors, a Chairman, a
General Secretary, a Treasurer and
a correspondent with ARGOS
International, and a registration
fee. The unformal launching only
needs one or several correspon-
dents with ARGOS international.
Of course, in both cases, members
of the national groups have first to
be registered as members of
ARGOS International.
ARGOS committees :
coordinating organs of the
national groups.
Committees are meant to coordi-
nate and lay down guidelines for
ARGOS International through
national groups. The three com-
mittees (Communication, Training,
International growth
3 partners, 3 orientations, 1 goal

and Assessment) composed of pro-
fessionals convene twice a year, and
notably at the International
Meeting in Paris. Committee mem-
bers, coming from the various
national groups, are to endorse
targets and monitor their progress.
They therefore are the true driving
force of the ARGOS network.
Electronic mail makes real-time
access to information available to
members sitting on the committees.
An elected Chairman chairs each
committee. The tenure is for two
years.
The Communication committee is
meant to increase the efficiency
and encourage the long-term deve-
lopment of ARGOS’ communica-
tions structure (Internet site, jour-
nal). It is also involved in organizing
the Annual International Meeting,
setting up and managing national
scientific committees that are to
compile and assess published mate-
rial for national seminars.
The Training committee spots, puts
forward and approves of ARGOS’
official training staff. It aims to
upgrade training background mate-
rial (synthetic models, CD-ROM,
and so on…) and national seminars.
In collaboration with training ser-
vices, it is also meant to have trai-
ning methods and sessions reco-
gnized by the national authorities
for professional training.
The Evaluation committee detects,
proposes and approves ARGOS’
Recognized as a training organi-
zation by the French authorities
under registration number
31670119662, the ARGOS
Association has been organizing
training sessions since 1997.
Professional training
in orthopaedic surgery
The ARGOS Association moved to
draft annual training reports two
years ago. The reports compile the
various training background mate-
rial developed and used over the
year involved, including the
articles, the lectures produced and
approved of by ARGOS’ members,
the reports of the congresses orga-
nized within the framework of
ARGOS together with the assess-
ments of the training sessions pro-
vided by ARGOS’ training centers.
Such reports fully account for the
major and efficient part played by
ARGOS in professional training in
orthopaedic surgery.
A personalized training
program
ARGOS international network’s
training centers are now available
to anyone with access to the Net.
The Web site’s database filled with
useful information, including a
detailed presentation of the regis-
tered training staff, their degree
courses, the registered specialist
qualifications and all the various
elements connected with the place
where they are in practice, can now
be searched through, allowing
Internauts to apply for a personali-
zed training program while on line.
The training programs have been
defined as several successive days
to be spent in the various centers of
the network. They are then retur-
ned by ARGOS’ Secretariat with a
choice of dates along with accom-
modation detailed information,
once the availability of the training
staff has been checked. Training
sessions get off to an early start with
operating programs, staff meetings
and consultations. Trainee surgeons
also attend theoretical courses in
the various surgical techniques and
all of their biomechanical aspects,
as well as in the assessment tech-
niques implemented by the center.
Let us hope that this approach, lar-
gely derived from the Tour de
France carried out by journeymen
completing their apprenticeships,
will come up to our expectations
and, ultimately, meet our members’
needs for training ! ■ PS.
official evaluation tools. It coordi-
nates the operating and the deve-
lopment of the assessment tools of
ARGOS’ international network (cli-
nical databases, medical software
for the quantitative analysis of
medical imaging, and so on…), and
devises research projects likely to
improve them. The assessment
committee works in close collabo-
ration with the Biostatistics depart-
ment (see article page 15). In colla-
boration with the national groups, it
is also meant to develop the use of
ARGOS’ evaluation tools and ser-
vices in their country. ■ AT.
Argos:
International
training

For more information, see next page and get in touch with your local distributor.
Circle8onReadingServiceCard
Centre Hospitalier de l’Université de
Montréal
1560 Sherbrooke Est Str.
Montreal (Qc)
CANADA H2L 4M1
Phone (514) 281-6000 #8720
Laboratoire d’imagerie, de vision
et d’intelligence artificielle (LIVIA)
École de technologie supérieure
1100 Notre-dame West Str
Montreal (Qc)
CANADA H3C 1K3
Phone (514) 396-8800 #7675
Biomechanics - biomaterials
research group
École Polytechnique
CP 6079 Succ. Centre-ville
Montreal (Quebec)
CANADA H3C 3A7
Phone (514) 3940-4711 #4198
Industrial collaborations :
GERMANY : Telos
CANADA : Arthrolab, BiOp,
Orthomedic, Zimmer
FRANCE : Argos, Eurosurgical, Ceraver
USA : Sofamor Danek,
Proctor and Gamble
Funding :
NSERC, FCAR, FREOM, FCI, FRSQ
University collaborations :
Biomechanics laboratory
of ENSAM (Paris FRANCE)
LIS3D & Hôpital St-Justine (CANADA),
University of Bochum (GERMANY)
5) 1) Arthrosis,study on total hip replacement, 2) Ligament reconstruction, 3D knee modeling, 3) Kinematic analysis, dynamic stability of the knee, functional knee evaluation,
computer aided design and evaluation of prostheses and arthroses, 4) 3D cartilage evaluation, 3D spine modeling, computer assisted surgery, MRI of artificial ligaments
Medical
imaging
2D/3D
digital
imaging
processing,
3D modelisation
and reconstruction,
low radiation
multiplanar imagery
Clinical studies
Diagnostics,
evaluation of
prostheses
and
orthoses
Medical
imaging
2D/3D
digital
imaging
processing,
3D modelisation
and reconstruction,
low radiation
multiplanar imagery
Clinical studies
Diagnostics,
evaluation of
prostheses
and
orthoses
Biomechanics
Study and modeling of
joint function, pathology,
prosthetic replacement
Biomechanics
Study and modeling of
joint function, pathology,
prosthetic replacement
and Orthopaedics
research Laboratory
Research center of CHUM Montreal Canada

Doctor Antonio Martin Benlloch
has become familiar with many
kinds of spinal instrumentations
during his surgical practice
(Harrington, Luque, Steffee
plates, CD, Isola, TSRH,
Twinflex, SCS). His initial trai-
ning with Professor Manuel
Laguia (Department of
Orthopaedic Surgery Hospital
Clinico of Valencia - Spain) as
well with Dr. J. Luis Bas
(Department of Orthopaedic
Surgery Hospital La Fe of
Valencia - Spain), have allowed
him to form a good idea of how a
spinal fixation system should be
used and what its capacities are.
You’ve been using CLARIS
instrumentation for over two
years now. What clinical indi-
cations do you use it for ?
Antonio Martin Benlloch : We star-
ted using CLARIS instrumentation
in 1996. At the time we had been
looking for a fixation system that
was simple, easy to insert, stable,
and which would allow patients to
achieve functional recuperation as
quickly as possible with the mini-
mum of postoperative bracing.
CLARIS instrumentation seems to
be especially adapted to degenera-
tive lumbar disorders and it is the
system that we use the most often
for lumbar surgeries. We have used
it for 120 operations at this level
and the constructs have been com-
pletely satisfactory. When the lum-
bar curvature of a patient with sco-
liosis is degenerative, we make use
of one of CLARIS instrumentation’s
biggest advantages : the possibility
of combining it with SCS instru-
mentation and its in situ contouring
technique.
The biomechanical tests car-
ried out at ENSAM’s
Biomechanics Laboratory,
indicate that in a screw-rod
construct, the intermediary
pedicle screws undergo for
less stress than those at each
end. Do these observations
seem logical to you and does
your personal clinical expe-
rience support them ?
AMB : These observations are
totally in line with my own clinical
observations. I have never seen a
screw fail at the intermediary
levels, but screws have failed at the
constructs’ extremities.
In a series of 125 cases of lumbar
surgery examined where approxi-
mately 98% were carried out using
CLARIS instrumentation, we had 2
cases with screws broken at S1
level and I am convinced these
incidents were caused by the sur-
gical technique used (only one
screw was placed at the level of the
sacrum) rather than by the screw
itself.
Does the adaptability provided
by the plastic deformation of
the intermediate connectors
seem to you like a definite
advance in simplifying the
surgical maneuver ?
ENSAM’s Laboratory of Biomechanics in Paris
constructed a three-dimensional model using
finite elements in order to understand the biome-
chanical behaviour of the spine when instrumen-
ted with multiple level transpedicular fixation.
Their analysis hightlights significant differences
in the loading conditions experienced by each
vertebra.
For example, the above figure shows the maxi-
mun bending moments of transpedicular screws
in a flexion-extension load of up to 10 Nm.
Bending moment
in screws
Clinical case
The Claris instrumentation in spinal fusion :
a specialist’s point of view
Dr. Antonio Martin Benlloch
Hospital “Clinico Universitario”
46010 Valencia - Spain
Training

AMB : I think that these special
connectors do in fact improve the
adaptability and the compensation
for differences in the screws’ posi-
tions (fig. 1, 2, 3). Using these
connectors means that even if the
pedicles are not aligned although
according to the X-rays the screws
are correctly inserted, there is no
need for concern not even at the
thoracolumbar level, whether there
are fractures, tumors or degenera-
tive scoliosis.
If you simply tighten the locking
connector, the intermediate
connectors adapt efficiently to dif-
ferences in angulation and depth of
the pedicle screws. It’s this very
phenomena that distinguishes
CLARIS from the other instru-
mentation currently available on
the market.
What specific difficulties could
be encountered and possible
errors made, the first time a
surgeon uses CLARIS instru-
mentation ?
AMB : You must take special care
that the rod’s profile corresponds to
the shape of the sacrum. When the
rod is bent, there is usually no more
than 4 or 5 mm between the
connector and the bone, and this
could make the insertion of the
second oblique screw difficult.
You must, in addition, prevent the
hardware from touching the over-
lying joint so that it is not damaged.
At the end of the intervention, you
should make sure that all the loc-
king nuts and the locking connec-
tors are correctly tightened. This
check ensures excellent fixation,
particularly when complementary
maneuvers of reduction and
contouring have been carried out to
adjust the profile. It is important,
especially in short constructs, to
stop rotation using rod-holding for-
ceps.
To prevent malpositioning and
the perforation of the anterior
wall of the vertebral body
during insertion, CLARIS
pedicle screws are not self-
tapping. Do you think that this
precaution provides
additional secu-
rity in screw
placement ?
AMB : I prefer
screws not to be
self-tapping since
it is important for
me to feel the path
of the screw. I also pre-
fer to make the hole in the pedicle
by hand rather than with the power
drill and I favour visual and tactile
inspection over direct video-assis-
tance. I rely on anatomical land-
The intermediate connector AL01
This intermediate connector pre-
sents the distinctive feature of
being adaptable to any screw posi-
tionning, while enabling firm fixa-
tion with no degradation of the
anchoring of the bone.
1
2
3
Training

marks (radiographic appearance
and the patient’s position) when
inserting the screws. It is unwise to
use self-tapping screws in osteopo-
rotic bone since it is very easy to
penetrate the cortical layer. If you
use a screw that is not self-tapping,
even if it is too long, it is impossible
to penetrate the anterior cortex, a
screw that is too long can be with-
drawn and replaced by a shorter
one.
In an in vitro study on screw
pull out strength, Professor
Lavaste (ENSAM
Biomechanics Laboratory)
observed that the resistance
depends mostly on the quality
of the bone ; the influence of
the kind of thread and the
length of the threaded portion
is limited. What do you think
about this ?
AMB : Some authors have shown
that a depth of insertion equal to
50% of the anteroposterior length
of the vertebral body is sufficient
for optimal hold into the vertebra.
Other authors recommend the use
of bicortical screws even in the
intermediary part of the spine. In
my opinion, surgeons should have a
good technique for inserting the
screws and use the least dangerous
methods and instrumentation.
ENSAM recently developed a
finite elements model of the
spine to evaluate the stress
distribution in the CLARIS
pedicle screws under simple
and combined loading modali-
ties of flexion-extension, tor-
sion and lateral bending. The
resulting pullout stresses were
low and remained inferior to
the endurance limit determi-
ned in vitro by Professor
Lavaste, except at the sacral
level. In your clinical expe-
rience, have you observed
postoperative problems rela-
ted to screw pull out ?
AMB : In the series of 120 CLARIS
cases we didn’t observe any screw
pull out. I believe that in too stiff
spines excessive pull out forces can
be caused by correction. You need
to take special care in the correc-
tion in the sagittal plane (restora-
tion of the lordosis).
At the level of the sacrum,
where the bone quality is not
always excellent, fixation
using two divergent screws is
recommended to counter the
higher stresses which are
characteristic of long
constructs. What is your point
of view on this subject ?
AMB : Screw pull out at the level of
the sacrum is a problem which
mainly concerns elderly patients
since their bone quality is
mediocre.
In my opinion, when fixation of the
sacrum can only be controlled
using complicated constructs to
reinforce it, it means that the pro-
blem was not correctly dealt with in
the beginning.
It seems to me that by following the
indications for improving the
screw’s hold at the sacrum level
(inserting the screw into the sacrum
near the vertebral end-place, using
bicortical screws or two divergent
screws) would solve most problems
of sacral fixation.
Blocking screws and the special
CLARIS connector appear to me to
be well suited to S2 fixation.
The Jackson technique, of inserting
a rod into the sacrum, also produces
very good fixation, but the proce-
dure is difficult to carry out.
CLARIS pedicle screws are
cylindrical and not conical so
as to avoid screw loosening
These informations,
the bibliography or
available on
the Website…
Experimental model for screw pull out
▼
CollaborationLBM-SOFAMOR

within the pedicle when the
depth of insertion is adjusted,
and to limit pedicle breakage.
Do you think that this precau-
tion is appropriate ?
AMB : I have never used conical
screws, but I would think that they
could cause two problems : the
fracture of the pedicle and the loss
of the screw’s hold into the pedicle.
It seems preferable to me to use a
cylindrical screw and to opt for a
larger diameter (fig. 4).
The comparison of the beha-
viour in flexion of smooth-col-
lared screws and screws
without a smooth collar shows
that for the same loading pat-
tern applied, the maximum
stress that the smooth-colla-
red screws undergo is 20 %
lower than that of screws
(fig. 5a & 5b) without a
smooth collar ; this should
reduce the risk of fatigue fai-
lure. Does your clinical expe-
rience corroborate this state-
ment ?
AMB : As I have already said, since
we have been using the CLARIS
system, we have observed very few
cases of screw breakage. It is alto-
gether possible that the screw’s
smooth collar has played a role in
this. Whatever the case, one should
remember that CD screws are also
smooth-collared, and to my know-
ledge it is for the same reasons.
The in vivo loads acting on pedicle
screws pertain more to bending
moments than pull-out loads.
What’s more, the triangulation pro-
vided by the use of a transverse link
at the end of the construct gives the
screws better resistance to pull out
than does extending the threaded
portion the entire length of the
screw.
The CLARIS connector’s
adaptability means that it is
sandwiched between the base
of the screw and the locking
nut (fig. 6) thereby preventing
the so called instantaneous
loosening that is sometimes
observed with other types of
hardware. Does your expe-
rience confirm the efficiency
of this screw-connector
assembly ?
AMB : We have never observed the
disassembly of a construct caused
by the loosening of the nut. This is
no doubt due to the efficiency of
the screw-connector assembly.
When other instrumentation is
used, it becomes necessary to insert
wedges to compensate for the dif-
ference in the screw and the
connector’s angulation. This is not
an easy maneuver and can some-
times lead to construct disassembly.
One of the advantages of CLARIS
instrumentation is that it simplifies
the operating procedure. By simply
tightening the locking nut, the cor-
rect screw-connector assembly is
automatically obtained, without the
addition of complementary hard-
ware.
CLARIS proposes reduction
screws (fig. 7) for the treat-
ment of spondylolisthesis.
What is your experience with
this kind of indication ?
AMB : When using the CLARIS
instrumentation in, for example
the case of spondylolisthesis at L5,
I fix the sacrum securely (two
divergent screws), and then pro-
ceed bilaterally with the progres-
sive reduction, continuously chec-
king the state of the L5 roots.
In all cases of spondylolisthesis, it is
vital to know when to stop the
reduction (a 100 % reduction is not
necessarily the best solution).
When the reduction seems suffi-
cient, it is important that there be
no space between the connector
and the locking nut. The connec-
tors are then 2 or 3 mm away from
the pedicle screw support rim. It is
therefore necessary to bend the
rods to bring them near to each
support rim and then tighten the
locking nuts to obtain an optimal
screw-connector assembly. The
5b
6
7
Training
4
Loosening of the screw
Damaging of the pedicule
5a

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