ENDOPROOTHESIS OF PHYSIOLOGICAL INTERVERTEBRAL DISC MOVEMENT FOR THE LUMBAR AND CERVICAL PART OF THE VERTEBRAL COLUMN.

摘要

Endoprosthesis of the intervertebral disc, for the complete replacement of the intervertebral disc in the area of the lumbar and cervical spine, composed of articulating sliding components, presenting the upper sliding component means for a fixed union with an upper vertebral body and the lower sliding component means for a fixed joint with a lower vertebral body and a sliding surface being arranged between the sliding components, in which a) a first sliding component (11, 12) is configured such that the opposite side at the junction with a vertebral body it presents a convex curvature, or convexity (16), and a. the radius of curvature of convexity (16) i. It is identical in frontal and transverse view and originates from the rotation of the smaller circular segment, which is between the two points of intersection of a secant (18) with a circumference (19), the secant (18) not passing by the center of the circle, and the rotation taking place around the segment of the secant (18) inside the circumference (19) as the axis of rotation, and ii. corresponds in sagittal view to a circular segment whose radius corresponds to the distance of the secant (18) to the circumference (19) of subpoint a) a. i., and b. the convexity (16) is enclosed by an edge (14), and b) a second sliding component (11, 12) is configured on the inner side with a concave articulation surface, or concavity (17), and the geometry of the concavity (17) is defined so that a. This has a gap corresponding to the convexity (16) of the first sliding component (11, 12), which b. it is enclosed by an edge (14), and c) the edges (14) of the two sliding components (11, 12) a. have an angle that opens outwards (opening angle, 21) with respect to each other, b. differentiating the opening angles (21) at least in the medial frontal section with respect to the medial sagittal section by the different inclination of the edges (14), to allow the maximum possible surface contact of the edges (14) in case of movement of terminal grade of the sliding components (11, 12), and c. transforming the different inclinations of the edges (14) in one another in a diffuse manner, d. the inclinations of the edges (14) being equal or different in case of opening angles (21) equal in a plane of vertical section on both sides of the articulation surface, and d) the angle of movement in the dorsoventral direction is greater than in Laterolateral direction, which results from the different radii of curvature sagittally with respect to frontal, and e) the maximum possible movement of the sliding components (11, 12) with respect to each other is set by a. the radius of curvature and the height of the convexity (16) with respect to the respective edge (14), and b. the configuration of the corresponding concavity (17) in each case, especially the height with respect to the respective edge (14) and the shape with respect to the corresponding convexity (16), and c. the surrounding edges (14) that run obliquely or horizontally in convexity (16) and concavity (17).