European Vertebral  Deviation Center - Clinique du Parc - Lyon (France)    3D - Bracing

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3D - Bracing

3D Nature of AIS

Course on the LYON METHOD for Scoliosis - Bangalore India 2017



First presentation: SOSORT Wiesbaden 2014

Second Presentation: SOSORT Katowice 2015

3D nature of AIS: implications in non-surgical treatment

From the frontal to the sagittal plane
The fight against gravity starts at Devonian (- 450 million years ago), when vertebrates leave the water (which almost completely nullified the force of gravity by buoyancy) to venture on the ground floor.
Breathing requires taking off the chest of the floor with mobility in the sagittal plane. Coupled movements in the frontal plane and in the sagittal plane will automatically cause a rotation. With bipedia, the sagittal plane has even become the function plane of the spine.

The torso column
The torso column is the mathematical representation of a circled helicoid with generating circle in a horizontal plane perpendicular to the vertical axis of the spine.

Movement of a solid on an axis
Only two movements are possible between a solid and an axis: Translation and Rotation. So relative to an axis, a solid has two degrees of freedom.

In the frontal plane
Motion is the sum of the rotation on the sagittal axis and the translation on the transversal axis.
The Charleston overcorrecting night brace uses this biomechanical action.
Some braces are built on this 3 points system.

In the sagittal plane
Motion is the sum of the translation on the sagittal axis and the rotation on the transversal axis in the frontal plane.
To correct the sagittal plane, it's necessary to use a 5-point system because both physiological lumbar lordosis and thoracic kyphosis must be corrected simultaneously.
This is easier with segmental molding and overlapping shapes.

On the vertical axis
Motion is the sum of the vertical translation or decoaptation and rotation of the apical vertebral.
To facilitate rotation, we must push in the horizontal plane on the posteromedial border of the rib hump convexity and on the sterno-costal cartilage on the opposite concave side. Axial elongation will facilitate derotation.

Evolution of translation along the vertical axis during last century

Coupled motion of the spine
In scoliosis, we are seeing usually a right thoracic inflexion and an opposite rotation to the left of the apical vertebra.
Lateral bending of the thoracic spine does not involve pure lateral bending but accompanies rotation. Coupled axial rotation in the same direction as lateral bending was observed in the neutral, flexed, and extended postures of the thoracic spine. Coupled axial rotation in the same direction as lateral bending were observed in the neutral and flexed postures, while coupled axial rotation in the opposite direction was observed in an extended posture.
This means achieving at the same time convex bending to the right and thoracic kyphosis if we want to correct the scoliosis initial rotation to the left.

From 3D plane geometry to the 3D solid geometry

Segmental derotation and Global detorsion
The segmental derotation at the apex of scoliosis is achieved through a mostly multiple 3-point system. The more complex system is the Chêneau brace with multiple 3 points system.
The overall untwisting or global derotation requires an elongation along the vertical axis between the scapular and pelvic belts, a push up effect on the horizontal plane at the thoraco-lumbar junction and a design of the brace with torsion opposite to scoliosis.
Due to the vertebral deformation, it is often impossible to reverse scoliosis and the segmental molding can indicate the maximal possible correction.

4D dimension is the time
The active correction is always maintained during breathing and motion. Expansions in the concavity must allow deep breath inspiration with concave ribs contact.

From 3D Deviation to 3D vertebral Deformation
The apical vertebra is not only the most rotated, it’s also the most distant from the gravity line with a very strong mechanical compression in the concavity. Ian Stokes describe the vicious circle with asymmetrical growth, vertebral and disc wedging, increasing the vertebral deviation and so one.

3D disc deformation
Is maximum at the lumbar level. Bracing is more efficient in remodelling disc than vertebral body, which explain the best correction of lumbar curves with the brace.

Isostatic balance
The obligation of the contact in 3 zones of 2 adjacent vertebrae, whatever the motion, requires the combination of several movements of translation and rotation at the Functional Spinal Unit. In adults, this mechanism explains the ante, retro listhesis and the rotational dislocations. In children, this mechanism explains the instability of flat back and hyperkyphosis.

3D muscular chaining
In the frontal plane, lateral chains are crossing at the thoraco-lumbar level and for the anterior chain, at knee level. Which explains that children often have trouble with knees in scoliosis.
Sagittal chains are crossing at the pelvic level (reciprocation). It is always difficult to determine whether the muscle is a motor or brake. Therefore unlike polio which requires analytical care, it is often global in idiopathic scoliosis.

Sagittal flexion and apical rotation
The instantaneous centre of rotation (ICR) of the vertebral body is near the posterior wall. During a forward sagittal bending of the spine, concave and convex muscle vectors are oriented towards the concavity. Below 25° of rotation, the ICR is between the two vectors and ensures stability. Above 25° of rotation, the ICR is outside of the two vectors and increases the rotation.
This is why the sport activity with forward bending of the trunk is sometimes contraindicated.

The delivery tricycle speed effect
Usually the weight is in front of the tricycle. For the same major curve, if the turn is approached at low speed, the tricycle will remain more stable that if it is approached at high speed.

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  The website has been updated for the last time on  June 18, 2017