Study design
This is a prospective controlled cohort observational study.
The experimental hypothesis predicted that patients treated with the ARTbrace would report a significant in-brace correction of major, minor, thoracic and lumbar curves for both the main prospective group and SRS & SOSORT restrictive criteria [17–19]. Although it is difficult to compare the different braces used around the world, we present the results in the same form as the Rigo System Cheneau (RSC) results [20].
Setting of the study: the five innovative concepts
Like (RSC) the general correction principle is detorsion and sagittal normalisation, i.e. with a minimum of distraction which usually favours the flat back [21]. However, the methodology of the ARTbrace achievement differs radically.
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The mathematical basis of the torso column is the circled helicoid with horizontal generating circle described by the French mathematician Robert Ferréol [22].For a circled helicoid, the Cartesian parameterization is the parameterization of the circle with diameter carried by Ox, with center (a,0,0), with radius b, forming an angle alpha with the horizontal. For torso column alpha = 0 (Figure 4).
The aim is to get not only a straight spine, but a reverse torso moulding opposite to scoliosis i.e. overcorrection of the scoliosis curvature. This overcorrection is possible only if the vertebral bodies are not distorted. Otherwise, we favour the correction accentuating the asymmetry of pressure on the vertebral body.
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The second concept is that of the squeeze attachment for cylindrical hay bales. Pressures are spread over the entire cylinder surface; this is contrary to the principle of the push and counter-push of the historical Lyon brace or other three point braces. As usual in the correction of 3D deformities of the scoliotic spine, room should be provided for migration of lateral curvature, rotated vertebrae and breathing exercises. In this design, actually various 3-point pressure systems are provided to correct the lateral curvature and vertebral rotation from different anatomical planes. In the ARTbrace the shape of the brace is not a straight spine like the Sforzesco or the old Lyon brace, but an overcorrected spine with reverse scoliosis (concept 1). This is possible thanks to the superposition of two corrective bending mouldings (Figure 5).
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The third concept is the wrench and bolt principle to “unscrew or untwist” scoliosis. For instance, the Chêneau brace uses the principle of pressure and expansion in many precise areas [23]. For a double major curve in the ARTbrace, the thoracolumbar area is the fixed point with unscrewing between this fixed point and the pelvis for lumbar curvature and the shoulder girdle for thoracic curvature. For a thoraco-lumbar curve, the fixed points are at the cranial and caudal parts of the spine and the unscrewing is done at thoracolumbar level. The pelvis is the «bolt head» which is stabilized by a symmetrical pelvic base like a key. Lumbar and thoracic segments above act as a wrench for the detorsion of scoliosis (Figure 6).
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The fourth concept is detorsion with a fixed sagittal plane. Axial elongation brings the vertebral bodies near the central axis in the frontal plane, and by untwisting the scoliotic spine between the pelvis and the shoulder the horizontal plane is corrected. So both geometrical detorsion and mechanical detorsion of the cylinder are working together. Untwisting the spine is done maintaining the curvatures in the sagittal plane. Indeed, the screw is not straight, but curved. However, curving the screwdriver is useless. The new solution is the moulding in frontal bending which respects lordosis and kyphosis and allows untwisting whilst retaining the curvatures in the sagittal plane. The spine in the sagittal plane is fixed as physiologically as possible. Only the frontal and horizontal planes are mobile (Figure 7).
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The fifth concept according to Panjabi is the coupled motion behaviour of the spine. The moulding is 2D but the correction is 3D. The direction of rotation may differ depending on the incurvation of the spine in the sagittal plane. When there is a flat back, the initial scoliotic rotation may be increased by the correction in the frontal plane. Restitution of physiological curves in the sagittal plane seems to decrease the scoliosis rotation (Harrison Fryette’s laws)
Principle I: When the spine is in a neutral position, sidebending to one side will be accompanied by horizontal rotation to the opposite side.
Principle II: When the spine is in a flexed or extended position (non-neutral), sidebending to one side will be accompanied by rotation to the same side [24].
Although these laws have not been described in the context of scoliosis, we often see an accentuation of the rotation during pre-surgical bendings in supine position.
Subjects
Since May 2013 all patients of JCdM at the ‘Clinique du Parc – Lyon’ were treated with the new Lyon brace (ARTbrace) instead of the classical EDF plaster cast. Our initial aim was to avoid the plaster cast, but very quickly, the ARTbrace appeared to be a much more effective solution compared to the former plaster casts and it was even better tolerated. So the whole treatment was continued with the same brace. In this prospective study of all patients of JCdM, the main group consisted of 225 patients with 304 curves from 20° to 55°. 245 primary curves with 26 double major curves and 59 secondary curves. Only patients with angulation exceeded 55° were excluded. Lumbar scoliosis continued to be treated with the short brace GTB [25]. The SRS/SOSORT criteria compliant group consisted of 64 patients with 84 curves.
All the data is recorded on Excel, and statistical analysis has been done with SPSS v20.
Description of the brace
ART is the Acronym for Asymmetrical, Rigid, Torsion brace. The name was created by Stefano Négrini, the inventor of the Sforzesco brace [26].Like the Sforzesco brace, the ARTbrace is constructed with 2 rigid asymmetrical lateral pieces of polycarbonate. They are connected posteriorly at the midline by a duraluminium bar like the historical Lyon brace. All metal parts are similar to those of the Lyon brace. Both anterior and lower ratcheting buckles are rigid, the upper third is Velcro (Figure 8).The brace is not in complete contact with the body: there is an expansion in the concavity which is there to allow room for the body’s expansion during inhalation (Figure 9).
The new segmental CAD/CAM moulding
To obtain a torso column on the opposite side of the scoliosis, the superposition of three electronic instantaneous full 3D mouldings is necessary. These mouldings are made with the full 3D instantaneous raster stereography digitizer Orten. Markers are placed on the optical jersey:
A visually monitored control with a posterior and profile view is mandatory to obtain the ideal posture (Additional file 1).
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The First moulding is performed in self active axial elongation for the pelvis and the shoulders. Pelvic version and harmony of curvatures in the sagittal plane are monitored carefully, but without trying to correct them (Figure 10).
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The second moulding is performed in lumbar shift and physiological lordosis for the lumbar spine. On the concave side, the axillary-trochanter line is vertical (Figure 11).
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The third moulding is performed in thoracic shift and physiological kyphosis for the thoracic spine. On the concave side, the axillary-trochanter line is vertical. To improve the high thoracic shift, the hand is placed on the head which bows towards the concavity (Figure 12).
Additional file 1:de Mauroy’s segmental moulding for ARTbrace.(MP4 15 MB)
For a single thoracolumbar curve, both thoracic and lumbar shifts are made in the same direction.
Modelling of the trunk shape with shapes overlay
These modifications are made using the software OrtenShape.In the frontal plane moulding 2 is superimposed on moulding 1, then moulding 3 (Figure 13).Similarly in the sagittal plane, the second moulding is superposed on the first one, then on the third moulding (Figure 14).Changes are made at constant volume and detorsion which is a result of both corrections in the frontal plane and the sagittal plane (Figure 15).
Specific design and curve pattern
A specific classification is not used, indeed most classifications were developed for surgery. For bracing, a specific classification was developed by Rigo for the specific needs of the RSC brace [27].
For the ARTbrace, the sagittal plane, pelvic tilt and axial balance are strictly controlled. The only modifications concern the frontal plane:
For a single thoracic curve, the second moulding is used only if the lordosis of the first moulding is incorrect and if this is the case we do not need the frontal shift.
For a single thoraco-lumbar curve, both thoracic and lumbar shifts will be made in the same direction.
For a double curve, the horizontal plane of overlay is at the level of the transitional vertebra, usually at the lumbosacral junction.
For a double thoracic curve, we give priority to the main rib hump, mainly the lower curve and in this case, the plastazote pad will be used to control the upper curve.
If the shoulders are unbalanced, it is also possible to make the upper end of the brace asymmetric at the axillary level like the historical Lyon brace.
No specific segmental derotation is required as the ARTbrace causes a global helical untwisting.
4D Global correction of the ARTbrace
The mechanical action of the ARTbrace is carried out:
Along the vertical axis of the spineIn the three sagittal, frontal and horizontal planes of the spine (Figure 16).In ARTbrace, the reference plane is the horizontal plane at the thoracolumbar junction. The anterior and posterior muscle chains in the frontal plane intersect at this level. The middle brace closure with ratcheting buckle must be strict (Figure 17).The elongation along the axis of the spine is carried out during the first moulding. The spring effect moves the apical vertebrae near the spinal axis. This is the correction of the internal geometric vertebral torsion (Figure 18).
This classical elongation in braces such as the Milwaukee brace has the disadvantage of reducing the curvatures also in the sagittal plane.Segmental mouldings in the lumbar and thoracic areas overcome this disadvantage, and reproduce physiological curvatures in the fixed sagittal plane (Figure 19).The correction in the horizontal plane is on the whole external surface of the trunk. In the case of a double curvature, there is a first untwisting between the pelvis and the reference thoracolumbar plane, and a second untwisting between the reference plane and the shoulder girdle (Figure 20).The correction in the frontal plane is also exerted on the entire external surface of the trunk. It is the shift that is achieved with mouldings 2 and 3 which allows this correction. The translation is at the apical vertebra level and not below, as in the old Lyon brace (Figure 21).For a single thoracolumbar curve, it is the reference thoracolumbar plane which ensures derotation of the entire trunk, between both pelvic and scapular planes. The lever arm is more important and the curve is therefore better corrected (Figure 22).In the frontal plane, it is also the reference thoracolumbar plane that will translate between both scapular and pelvic girdles. Lumbar and thoracic shifts take place in the same direction (Figure 23).
The 4D global correction of ARTbrace occurs during the day and the movement is obtained by balancing among both frontal and horizontal anatomical planes. The inversion of the curvatures automatically creates an expansion in the concavity that allows the 4th dynamical dimension, i.e. contact during movement and breathing.
Practical issues
How to check the brace
Clinically, the height of the child in brace is measured, because the gain in height is an average of 1.58 cm due to the untwisting of the spine. This is an excellent clinical indicator of the effectiveness of the brace. In the sagittal plane, alignment of Tragus – Acromion - Trochanter - Ankles is checked.
Frontal and sagittal X rays are performed 3 to 4 days after fitting the brace with the ultra low dose EOS system which also allows a 3D reconstruction if necessary.
The metal bar must be vertical in the frontal plane and the C7 axis well balanced.
Adjusting the brace is made in the supine position. The middle ratcheting buckle is checked at the chondro-costal level. The tightening of the lower ratchet closure does not compress the abdomen, but stabilizes trochanters. Upper Velcro closure must be tight enough to prevent the tingling in the upper limbs.
It is always possible to add on a plastazote pad inside the polycarbonate, but in practice this is an exception.Indications of the sitting posture are given with feet behind the chair, buttocks in front of the seat, polycarbonate touching the edge of the table and forearms on the table (Figure 24).
In the ARTbrace, the fixed point is the lower part of the thorax at the thoracolumbar junction. The dynamic movement of the posterior part of the spine is better in this posture. It is the fourth dimension of the brace. The child will relax in the listening posture on the back of the chair. Alternating these two extreme postures seems to be more dynamic.
Protocol and every day usage
All patients and parents give an informed consent and approval to use this new brace instead of the old plaster cast.
Similarly to the plaster cast, the total time is advised with weaning of a maximum of 10 minutes to allow for a shower.
Unlike clubfoot treated by serial casting according to the Ponseti method [28], there is little data in the literature regarding the time required to achieve a creep of the concavity in scoliosis. The Lyon experience is as follows: below 30° scoliosis, the total time is 1 month. The time required is two months for scoliosis between 30° and 39° and 4 months for scoliosis of more than 40° [3, 10, 11].
Indeed, continuous stretching for more than 3 weeks is necessary to permanently change the length of a ligament (creep), as for an ankle sprain. If the brace is removed for more than one hour, the viscoelastic structures return to their original length with only elasticity.
Physiotherapy is essential throughout the total time period; it is identical to that which was recommended with the plaster cast [29].
Sport is permitted with the brace and even recommended to better adjust the tension of the muscle chains. When the paraspinal musculature is active, it creates a pre-stressed beam along the spine which protects the vertebral body from collapsing [30].