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Aurélien COURVOISIER, Raphaël VIALLE, Wafa SKALLI - EOS 3D Imaging: assessing the
impact of brace treatment in adolescent idiopathic scoliosis - Expert Review of Medical Devices -
Vol. 11, n°1, p.1-3 - 2014
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EOS 3D Imaging: assessin
g the impact
of brace treatment in adolescent
idiopathic scoliosis
Aure
´
lien
Courvoisier
Author for correspondence:
Pediatric Orthopedic Surgery
Department, Grenoble University
Hospital, Joseph Fourier
University, BP 217 38043
Cedex 09 Grenoble, France
aurelien.courvoisier@gmail.com
Raphae
¨
l Vialle
Pediatric Orthopedic Surgery
Department, Armand Trousseau
Hospital, AP-HP, Paris 6
Universisty, 12 rue Arnold
Netter 75012 Paris, France
Wafa Skalli
Biomechanics Laboratory,
Arts et Me
´
tiers ParisTech,
151 Bvd de l’ho
ˆ
pital 75013
Paris, France
One of the major revolutions in the field of adolescent idiopathic scoliosis (AIS)
during the past 10 years is the development of 3D imaging devices in standing
position, such as EOS (EOS Imaging). 3D vision of the spine is new; we need to
be humble and learn how it may help in the management of AIS. But we now
have access to the transverse plane deformity. We do not know how to heal
idiopathic scoliosis. Thus, the main issue in the field of AIS management is to
avoid progression of mild scoliosis. Brace treatment is the main treatment option
for mild scoliotic patients during growth. However, the efficacy of brace treatment
is not consensual. We have demonstrated through a 3D analysis of brace
treatment that some braces are truly efficient, some are not and others worsen
the spinal deformity. Therefore, we have to anticipate the effect of a brace on a
specific patient. With 3D analysis we are now able to evaluate if a brace really
improves the spinal shape in the 3 dimensions or not. Moreover, we have the
patient 3D geometry (spine and rib cage) and we are able to collect objective
clinical data that could help achieve relevant parametric finite element models.
These models could help in the prediction of brace effect but they need to be
validated with clinical data. We see a close future where we will all have the 3D
trunk shape of our patients on our screens along with all computed angles we
need and then an instant prediction for the best-fit brace geometry for our
patient.
One of the major revolutions in the field
of adolescent idiopathic scoliosis (AIS)
during the past 10 years is the develop-
ment 3D imaging in standing position.
The concept of AIS as a 3D deformity
was brought for the first time in the
early 80s by Perdriolle
[1] and Dubousset
and Graf
[2]. Before them, AIS was a
curve on a single AP view radiograph.
From the concept to the routine use of
3D, we had to wait until the 21st cen-
tury and the work of Georges Charpak,
the 1992 Nobel Prize of physics, to see
the development of standing position
stereoradiography and its evolution in
the actual EOS system (EOS Imag-
ing)
[3]. Accuracy and reproducibly of
the system and its software for 3D
reconstruction of the spine have been
validated and are constantly improv-
ing
[4]. From now on, 3D analysis of the
spine in a standing position is possible
routinely.
Now that we have the tool, we have
to learn how to use it. AIS professionals
all over the world have learned AIS
from the patient and from standard AP
and lateral X-rays. 3D is new and EOS
provides a large amount of data. We
therefore need to be humble and learn a
new way to describe AIS. EOS and 3D
have created a lot of questions and but
few answers yet. One thing is sure; we
now have a good point of view on the
transverse plane, which we think, is
where we can early detect a progressive
AIS deformity. We have demonstrated
that a progressive curve had a specific
3D pattern, which can be detected early
before the progression of the Cobb
angle
[5]. This test could be accessible at
the first clinical exam from a single EOS
KEYWORDS: 3D • Brace treatment • EOS Imaging • finite element model • idiopathic scoliosis
stereoradiography and could predict the evolution of a mild
scoliotic curve (Cobb angle <25˚). Before, we had to wait
6 months or one year and consecutive radiographs to diagnose
a progressive curve.
We do not know how to heal idiopathic scoliosis. Thus,
the main issue in the field of AIS manageme nt is to avoid
progression. But progression was the only way to be sure to
treat only true progressive AI S. Now, by mean s of the 3D
progressive pattern, i t is pos sible to treat on ly pro gressive
AISatthefirstexam.Butatthisstage,formildscoliosis
with a Cobb angle below 25˚, treatment options are not
consensual. Most surgeons would recommend a simple med-
ical supervi sion b ut few would initiate a brace treatment.
Because we know that each step toward progression of a
scoliotic curve is a point of no return, we think that the ear-
lierthetreatmentisstarted,themoreefficientitwillbe.
Despite the actual recommendations
[101],wethinkamild
scoliosis (Cobb <25˚) needs a brace at the firs t exam, if we
can prove it is a potentially severe curve. The controversy
stands in the surgeons’ opinion of the efficac y of brace
treatment. Several authors have underlined the lack of statis-
tical evidence of brace treatment e fficacy
[6]. However, we
have recently demonstrated that this lack of statistical evi-
dence should not restraint the use of brace treatment
[7].
Some braces are truly efficient, some are not and others
worsen the spinal deformity. Our plea is to invite AIS pro-
fessionals to consider a specific brace for each specific
patient and not to standardize brace treatment. And most of
all we need to analyze the 3D e ffect of the brace on the
spine.
The difficulty of brace treatment is to obtain a ‘patient-
specific’ treatment. Between the patient’s scoliotic curve with
its specificity (age, magnitude, reducibility, location, and so on)
and a ‘patient-specific-tolerable’ brace, stands a great gap,
which could be filled partially with 3D Imaging. The main
issue is to predict the effect of a brace on a specific patient.
Before 3D, we could only predict the effect of braces empiri-
cally. With 3D, we are able to start digitizing each step of the
whole process of brace conception.
The first main step is to achieve a 3D reconstr uction of
the rib cage an d the external trunk sha pe along with the
spine. Then we will need the most realistic finite element
model (FEM) of the spine and chest. We have yet progressed
toward this goal with a recent s tudy on the validation of a
method of 3D reconstruction of the rib cage in scoliotic
patients
[8,9]. With actual s ystems of computer- assisted con-
ception of braces, the external trunk shape is easily obtained.
A combination of the external trunk shape with the EOS 3D
skeletal reconstruction of the spine and chest should provide
a patient-specific 3D geometrical model. It is the key point
to assess the effect of a brace on the whole trunk with
parametric FEM.
Parametric FEM of the scoliotic spine an d the growing
spine have been developed during the past 10 years
[10,11].
Numerical models were also created to predict the e ffect of
brace t reatment but their main limitation was that they were
not clinically validated
[12,13]. With 3D analysis of the spine
and brace tr eatment, we have the patient 3D geometry and
weareabletocollectthemissingclinicaldatainorderto
achieve m ore relevant parametric FEM. But there are still
problems to solve. For example, flexibility of the curve is a
difficult parameter to implement in a FEM because it relies
on different factors like the age of the patient, the location
and the severity of the curve
[14]. It is true for severe curves,
but flexibility becomes more negligible for mild scoliosis as
they are almost all completely flexible. This is the reason
why we promote a brace treatment for mild scoliosis
below 25˚.
Nonetheless, the harder work is now to collect 3D data
on our patients and to distinguish what is efficient or not
with the different types of braces for each s pecific type of
curve. We have to leave the era of empiric conception of
braces and to formalize the process. The principles of correc-
tion are similar for most of braces but each d esigner c laims
to reach better correction in the three planes than the other.
We need to overwhelm our egos and reach re producible sci-
entific data. With 3D analysis, we are now able to evaluate
if a brace really improves th e spinal sha pe in the 3 dime n-
sions or not. Once brace conception will cease to be a self-
interested busin ess on a self-designed brace, randomized pro-
spective studies will reassure skeptical surgeons on brace
efficacy.
EOS 3D Imaging system is a great tool, which announces a
great improvement of our knowledge of AIS and its manage-
ment. EOS software improves permanently and engineers are
working on more automation of 3D reconstruction. Further-
more, EOS system is a low-dose imaging system, which is
more suitable for the follow-up of children than standard full
spine X-rays. Tomorrow, we will all have the 3D trunk shape
of our patients with on our screens along with all computed
angles we need. We will have parametric models that will
instantly predict the best-fit brace for our patient. Then the
clinical and 3D radiological data during the follow-up will
improve the model. It is not science fiction it is the close
future.
Financial & competing interests disclosure
The authors have no relevant affiliations or financial involvement with
any organization or entity with a financial interest in or financial conflict
with the subject matter or materials discussed in the manuscript. This
includes employment, consultancies, honoraria, stock ownership or options,
expert testimony, grants or patents received or pending, or royalties.
No writing assistance was utilized in the production of this
manuscript.
References
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Website
101 Scoliosis Research Society Bracing Manual.
www.srs.org/professionals/education_
materials/SRS_bracing_manual/