Glossary



Spinometry

Spinometry is the method, in which the DIERS products formetric 4D and 4Dmotion use the results of the optical examination of the back surface to calculate a correlating model of the spine. This unique technique allows a profound visualization of posture and functionality of the spine. Originally developed as an alternative for x-ray-based longterm documentation of scoliosis, spinometry is also able to cover a wide range of functional diseases and malpositions. Essential posture-related parameters such as pelvic obliquity, pelvic torsion, surface- and spinal rotation or even shoulder obliquity are all obtainable. Spinometry is the basis for a holistic view of the whole human body. Its integration into the complete DIERS product portfolio is fundamental to getting an impression of functional coherency from head to toe.
 


Videorasterstereography

Videorasterstereography is a concact- and radiation-free method to analyse the surface of the human back. The procedure was developed at the "Institut für Experimentelle Biomechanik" of the University of Münster, Germany. Since its function depends on the principle of triangulation, everything needed is a video camera and a projector that projects a pattern of parallel stripes onto the patient's back. The camera then captures the image of the back surface and sends it to a computer system. By analyzing the deformation of the stripes, the system is able to calculate the three-dimensional position of the back.
 


Triangulation

The video camera and the stripe projector are two fixed points with a fixed distance (h) to each other. To that we know the angles each of the camera lens (a) and the projection stripes (ß). These constants allow the calculation of every other angel or distance and the three-dimensional position.
 


Scoliosis

Scoliosis is a lateral curvature or deviation of the spine combined with a rotation of the vertebra. You can easily see the deformity in the coronal plane, but the rotational component of scoliosis is visible in the sagittal plane as well (e.g. hunches). Regarding differential diagnostics there is a distinction between a structural and a nonstructural scoliosis. The latter shows a smaller Cobb-angle (less than 10°) and most commonly a pelvic obliquity because of leg length discrepancies or contractures which is usually not a factor in structural scoliosis.
 


Cobb angle

The Cobb angle, named after the American orthopedic surgeon John Robert Cobb (*1903-1967), was originally used to measure coronal plane deformity on antero-posterior plain radiographs in the classification of scoliosis.

Cobb's angle, a measurement used for evaluation of curves in scoliosis on an AP radiographic projection of the spine. When assessing a curve the apical vertebra is first identified; this is the most likely displaced and rotated vertebra with the least tilted end plate. The end/transitional vertebra are then identified through the curve above and below. The end vertebra are the most superior and inferior vertebra which are least displaced and rotated and have the maximally tilted end plate. A line is drawn along the superior end plate of the superior end vertebra and a second line drawn along the inferior end plate of the inferior end vertebra. If the end plates are indistinct the line may be drawn through the pedicles. The angle between these two lines (or lines drawn perpendicular to them) is measured as the Cobb angle. In S-shaped scoliosis where there are two contiguous curves the lower end vertebra of the upper curve will represent the upper end vertebra of the lower curve. Because the Cobb angle reflects curvature only in a single plane and fails to account for vertebral rotation it may not accurately demonstrate the severity of three dimensional spinal deformity. As a general rule a Cobb angle of 10 is regarded as a minimum angulation to define scoliosis.

 


Spine reconstruction

The reconstruction of the spine is a result of the surface topography of the back. For that two calculations are essential. The image captured by videorasterstereography shows a “map” of the back surface. By drawing a line of symmetry, the back surface can be divided into two symmetric areas. This line is equal to the run of the spinous process line.

In addition to that, during the light optical examination the three-dimensional coordinates of each point of the back is captured. The way these points are positioned in relation to each other gives information on their alignment. In this way we get information of the run of the spinous process line not only in the coronal plane, but also in the sagittal and axial plane as well. This three-dimensional alignment of the spinous process line is crucial for the reconstruction of a spine model.

 


 

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