By identifying the patients for whom the model predicts a significant progression the
investigators could focus their efforts on being more pro-active towards brace wear for
those at risk of progression. With the advent of new growth modulation techniques, these
patients could also potentially receive early management of their curves to prevent
further progression and diminish the need for surgical correction and fusion of their
curve. Alternatively, by identifying the patients that will not progress immediately at
the first visit, the investigators could arguably decrease their number needed to treat
from 4 to 2 by removing those patients that won't progress no matter what their treatment
is. So, the prediction model will not only have an impact for the patients at risk of
progression but will also impact those that are braced despite having a low risk of
progression.
Patient enrollment:
Patients who meet the inclusion criteria will be offered enrollment in the project. If
the family wishes to enroll in the project, the informed consent process will be
undertaken and the patient will be enrolled.
If Patients need to be treated with brace No changes in the usual treatment and
monitoring will be instituted. Therefore, patients will be allowed to undergo brace
treatment. The investigators are aware that brace treatment could have an impact on curve
progression but these patients are still included as progression despite brace treatment
may give meaningful information regarding these difficult-to-treat curves. Patient under
brace treatment will have to remove brace at least the night before their appointment and
follow-up spine radiographs. Also the protocol requires that patients have at least one
spine radiograph out of brace every 12 months. Bracing compliance will be evaluated as a
specific covariable in the upcoming study. To better understand the impact of bracing on
progression, the investigators will be using brace monitors, pressure sensitive
transducers that can monitor brace wear and brace effectiveness, in their multicenter
study and use the data generated by these monitors as a co-factor in an improved
prediction model.
If patients need to have surgery Although patients showing sufficient curve progression
to undergo surgical correction will not be kept in the prospective cohort after surgery,
their data will still be analyzed to assess the correlation between local 3-D
measurements and curve progression.
-Data collection.Data collected at first visit will include:
- - body-mass index (weight and height)
- family history.
- - sexual maturity (start of menses for girls)
- rib prominence.
- - initial radiographic evaluation.
Data collected at each follow-up visit (ideally
every 6 months)
- - body-mass index (weight and height)
- menarchal status,
- skeletal maturity.
- - Radiographic evaluation (at least every 12 months during the study period, without
brace).
- - Image acquisition and transfer to central measurement site.
Image acquisition
is standardized between sites according to standard operating procedures. All
images are acquired with the EOS™ system in the same fashion based on the
position proposed by Horton et al. that standardized lateral radiographs by
using a hand-on-clavicle position. The radiographs are all taken in the same
way thus minimizing variability. For the centers without an EOS™ system for
part or for the entire study, utilization of calibration belts will allow
radiographs to be taken in a calibrated environment. The position used for
image acquisition is the same as for the EOS™ system.
- - Three-dimensional reconstructions of the spine The stereo radiographic images
are used to create an external three-dimensional representation of the
vertebral body using a specific algorithm.
First, a spline is fitted through
the centers of the vertebral bodies both on the PA and lateral views. The
information from both images is then used to reconstruct a 3-D spline or curve
which will act as a rough three-dimensional scaffold onto which the local
vertebral and intervertebral reconstructions will take place. The vertebral
endplates are represented by a crude preliminary model of the spine by using a
set of cubic templates roughly representing each vertebral body stacked on top
of one another to form the spinal column. A global configuration of the
deformable spine model is thus described for each cubic template associated
with each vertebral level. The final reconstruction can then be completed using
a priori knowledge from a database of scoliotic and normal vertebrae that were
measured by the investigator's research group. The a priori knowledge model
relies on the description of each vertebra by a deformable model, which
incorporates statistical knowledge about its geometrical structure and its
pathological variability. The statistically optimized reconstructions will be
used to determine the intervertebral disk shape at each level.
- - Three-dimensional stereoradiographic reconstructions of the pelvis.
The pelvis will be reconstructed in 3-D for all normal and AIS subjects using a
combination of the Non-Stereo Corresponding Points (NSCP) and Non-Stereo Corresponding
Contours (NSCC) methods, which were successfully by the investigator's team to
reconstruct the spine in 3D. Preliminary evaluation of the technique gave an overall
accuracy of 1,6 mm, which is adequate for the calculation of clinical geometric indices
of the pelvis. Four steps are required with this 3D reconstruction technique:
1. Identification of seven specific regions of the pelvis;
2. Display of a preliminary model with 45 control points. The control points can be
modified in real time by the user (NSCP);
3. Interactive identification of regional contours (NSCC);
4. Generation of the personalized 3D pelvic model by deforming a generic 3D pelvic
model using 3D geometrical kriging.
- - Local three-dimensional measurements of the vertebrae and disks:
The calculated parameters were divided into six categories.
Each category refers to
global (whole spine), regional (scoliotic segment) and local (vertebra) descriptors.
Vertebra centroid is understood as the halfway point between the centers of the two
endplates of the vertebra. The local vertebra axis system is defined by the Scoliosis
Research Society (SRS) 3D terminology group: the origin is at the centroid of the
vertebral body, the local 'z' axis passes through the centers of the upper and lower
endplates, and 'y' axis is parallel to a line joining similar landmarks on the bases of
the right and left pedicles.
1. Cobb Angles: Cobb angles defined as the angle between the upper and lower endplate
of the respective end vertebrae of a curve. Cobb angle was measured in the frontal
plane, in the plane of maximal deformation in 3D and in the sagittal plane for
thoracic kyphosis (T4-T12) and lumbar lordosis (L1-S1).
2. Plane of maximal deformation: Axial angle of the plane in which the Cobb angle is
maximal.
3. Three-dimensional wedging of vertebral body and disk: Wedging of the apical
vertebral body in the plane of maximal deformation (3D plane) and mean maximal 3D
wedging of the two apical intervertebral disks. Maximal 3D wedging represents the
wedging measured in the plane, wherein the wedging value is maximal around the
vertical axis. If apex was a disk, then the mean of the 3D wedging of both apical
vertebral bodies was calculated and only the 3D wedging of the apical disk was
documented. 3D disk wedging was analyzed for all levels of the spine (from T1-T2 to
L4-L5).
4. Axial intervertebral rotation of the apex, upper and lower junctional level and
thoracolumbar level: Rotation between two adjacent vertebrae at upper, apical, and
lower curve levels and thoracolumbar junction (T12-L1) in the axial plane according
to the inferior local vertebrae reference.
5. Torsion: Mean of the sum of intervertebral axial rotation (measured according to the
local referential of the inferior vertebrae) of the two hemicurvatures of the curve
(between upper end vertebra and apex and between lower end vertebra and apex).
6. Slenderness (local T6, T12 and L4 and regional T1-L5): Ratio between the height
(distance between the superior and inferior endplates at the center of the
vertebrae) and the width (measured at the center of the vertebrae using a line
perpendicular to the height line in medio lateral direction) of the vertebral body
for T6, T12 and L4 vertebrae. Ratio between the length of the spine from T1 to L5
and the mean of the width of vertebral bodies of T6-T12 and L4. The same measurement
was made by replacing the width by the depth (a line perpendicular to the height
line at the center of the vertebra in an anteroposterior direction).
- - Geometric pelvic indices:
Geometric pelvic indices will be calculated automatically with the generation of the 3D
pelvic model.
Indices describing the orientation of the pelvis in 3D (positional
indices), based on the line joining the center of both femoral heads (hip axis), will be
calculated first. Pelvic axial rotation is the orientation of the hip axis around the
vertical axis (gravity line) as viewed in the transverse plane. Pelvic obliquity is the
orientation of the hip axis around the horizontal line as viewed from the coronal plane.
Pelvic tilt is the orientation of the pelvis around the medio-lateral axis of the pelvis
as viewed from the sagittal plane. In this last case, at least another landmark from the
pelvis (such as the center of the upper sacral plate) needs to be identified in addition
to the hip axis. The sacral slope (angle between the upper sacral plate and the
horizontal line is also calculated since it is highly correlated with lumbar lordosis.
Sacral obliquity is the angle between the upper sacral plate and the horizontal line.
Morphological indices of the pelvis (not dependent on the patient's position) are
computed in a reference coordinate system based on the hip axis orientation, in order to
eliminate the effect of pelvic axial rotation and obliquity. This means that
transformation into the reference coordinate system allows calculation of morphological
indices in the true coronal, axial and sagittal planes of the pelvis. The investigators
selected the pelvis as their reference system based on the pelvic vertebra principle from
Dubousset, which states that the pelvis can be viewed as a separate vertebra. As
described earlier, numerous morphologic parameters of the pelvis have been used in the
past, as detailed in Tables I to
- III. Of these, after a thorough review of the
literature, the investigators selected what they consider the 7 most pertinent specific
indices.
The investigators based their decision on the potential association of the
pelvic indices with the pathogenesis of AIS. Since they demonstrated the close
relationship between pelvic incidence and lumbar lordosis in AIS, the investigators
selected morphological indices of the pelvis that are correlated with the spine geometry.
