DD239524B3 - intervertebral disc prosthesis - Google Patents

Description

The invention relates to a multi-part endoprosthesis of the nucleus pulposus.

Intervertebral endoprostheses that serve as replacements for degenerated or destroyed discs are known in several embodiments.

For example, FR 1,222,634 describes cushion-like intermediate layers or plastic intermediate bodies.

Also known are intervertebral endoprostheses, which consist of a recessed into the vertebral body bearing cup and a ceramic spacer body (CH-PS 624,573). A further development of this prosthesis is described in Swiss Patent 640,131. The further development is that the bearing bodies are provided with raised edges which are intended to prevent the spacer body from sliding out.

In US-PS 4,309,777 a round, sleeve-shaped interdigitated prosthesis is described in the compression springs to ensure a certain elasticity.

SU-PS 825.433 describes an existing from a liquid-filled cushion disc prosthesis, which is firmly anchored by means of hook-shaped projections in the adjacent vertebral bodies.

Also described was already a multi-part intervertebral disc prosthesis, which consists of rotationally symmetrical end plates with concave central part and linsenförmigem, convex spacer.

The known intervertebral disc prostheses have the disadvantage that they either do not ensure compliance with a minimum distance of the vertebral bodies, that by relatively high specific pressures exerted by the bearing pans, the surrounding bony tissue is destroyed, that the bearing body must be incorporated into the adjacent vertebral bodies and / or that partly lengthy manipulation of the patient is required.

The invention has for its object to provide an endoprosthesis of the nucleus pulposus, which guarantees a minimum distance between two adjacent vertebral bodies, which ensures mobility and excludes by low specific support pressures a mechanical destruction of the adjacent vertebral bodies.

This problem is solved in that the intervertebral disc prosthesis consists of extensive, approximately oval or round base and cover plates (end plates) and a symmetrically smaller central part, each with specially curved surfaces (cylinder segments) facing each other faces. The axes of rotation of the bends (cylinder segments) of the middle part are at an angle of 90 ° to each other and are thus toric surfaces. The adjacent surfaces of the base and cover plates are also cylinder segments, with the same radii of curvature as the middle part. As a result, a mobility in approximately physiological dimensions is possible.

The end plates are the two vertebral bodies to directly on the inner edge strip and z. B. be anchored stable by means of a peripheral toothing and / or planar toothing and / or a bioactive coating. The application of bone cement is also possible.

Depending on the position of the cranially or caudally curved movement surfaces, the intervertebral disc prosthesis acting on the low-friction principle can be manufactured in four different embodiments.

The middle part can be made variable in height according to the cranio-caudal extension of the disc space.

The disc endoprosthesis can be adapted to the normal spine curvature.

In one embodiment of the invention, it is possible to attach as an additional safeguard against an undesirable change in position of the middle part of this cranially and caudally reaching, centrally located pin. These engage in recesses, which are incorporated in the base and cover plates. The recesses are advantageously either circular (blind hole-like) and have a larger diameter than the pin or they are groove-shaped. Conversely, cones facing the center of the segment, end plates and bores in the middle part or combined variants are also possible.

The endplates and midsection are fabricated from implant-proven materials (e.g., metal, polyethylene, polyurethane, ceramic, bioactive material) and can facilitate implantation in the center of the disc space via an anteriorly located marker.

For radiological representation, the plastics used can be marked accordingly.

The invention enables an approximately complete replacement of the nucleus pulposus and guarantees a physiological mobility as well as a buffering in the spine segment with suitable material combinations.

The invention will be explained in more detail below with reference to two exemplary embodiments. The accompanying drawings show

Fig. 1: schematic representation of an intervertebral disc prosthesis embodiment 1 Fig. 2: schematic representation of an intervertebral disc prosthesis embodiment 2 Fig. 3: schematic representation of an intervertebral disc prosthesis with additional securing by pins and with

circular recesses Fig. 4: schematic representation of an intervertebral disc prosthesis with additional pin securing and groove-shaped recesses.

Embodiment 1

The embodiment 1 relates to the figures 1 and 2.

The intervertebral disc prosthesis consists of a cover plate 1, a middle part 2 and a base plate 3.

The cover plate 1 and the base plate 3 are the same size and preferably round or oval. The middle part is symmetrically smaller.

All touching surfaces are cylinder segments with the same radii of curvature. The upper and lower curvature of the middle part 2 have at an angle of 90 ° to each other standing axes of rotation and are thus toric surfaces.

An anchoring of the intervertebral disc prosthesis to the adjacent vertebral bodies is carried out by means known per se.

The disc endoprosthesis can be adapted to the physiological conditions of the intervertebral space and spinal cord lordosis. It is provided with a vent marking, which facilitates a correct implantation.

Embodiment 2

Embodiment 2 relates to FIGS. 3 and 4.

The intervertebral disc prosthesis is designed as in embodiment 1. In addition, however, it has in the cover plate 1 and the base plate 3 blind hole-like circular recesses 4, projecting into the cranially and caudally reaching centrally located pin 5. The diameter of the recesses 4 is always greater than the diameter of the pin 5, on the one hand to ensure mobility and on the other hand to limit the maximum mobility. The length of the pin 5 is dimensioned so that they do not touch the bottom of the recess 4.

It is also possible to realize a limitation of the maximum mobility over groove-shaped recesses.

Documents considered:

DD 234609 (A 61 F 2/44) DE-PS 3023353 (A 61 F 1/02)

Claims (5)

1. intervertebral disc prosthesis, consisting of base and cover plate (end plates), which coincide in shape and size and border with curved surfaces to a middle part arranged therebetween, characterized in that the upper and the lower surface of the central part (2) are cylinder segments whose Curves intersect at an angle of 90 °. 2. intervertebral disc prosthesis according to claim 1, characterized in that the base and cover plate (1,3) are round or oval and circumferentially equal, that the central part (2) is symmetrically smaller in the circumference and that the radii of the curvature are the same. 3. intervertebral disc prosthesis according to claim 1 and 2, characterized in that it comprises a ventral mark for determining the position during implantation. 4. intervertebral disc prosthesis according to claim 1 to 3, characterized in that the central part (2) is provided with cranially and caudally reaching pin 5, either in circular recesses (4) or in groove-shaped recesses (6) of the base and cover plate ( 1.3) protrude to limit the movement and to increase the positional security of the central part (2). 5. intervertebral disc prosthesis according to claim 1 to 3, characterized in that the base and cover plate (1,3) with pins (5) are provided and that the central part (2) either circular recesses (4) or groove-shaped recesses (6) for receiving the pin (3) for the movement limitation and to increase the position security of the central part (2). For this 2 pages drawings