CH640131A5 - Complete intervertebral prosthesis - Google Patents

Description

640 131

Claims (2)

PATENT CLAIMS 1. Total intervertebral prosthesis, in particular for cervical vertebrae, in which a bearing body carrying a joint socket and having an at least essentially rectangular or square outline is anchored in the adjacent end surfaces of two vertebrae facing one another, with a spacer body being inserted between the bearing bodies, characterized in that in that each bearing body (4) has in one of its longitudinal sides, seen from the level of the edge of its socket (7), a recess (6) and on the longitudinal side parallel thereto a protruding tab (8), the recess (6) and the tabs (8) are matched to one another in such a way that when the spacer body (5) is inserted, the tab (8) of one bearing body (4) engages in the recess (6) of the other bearing body (4). 2. Prosthesis according to claim 1, characterized in that the depression (6) and the tab (8) are provided with oblique boundaries (9) or flanks (10) running essentially parallel to one another. The invention relates to a total intervertebral prosthesis, in particular for cervical vertebrae, in which a bearing body containing a joint socket and having an at least substantially rectangular or square outline is anchored in the adjacent end faces of two vertebrae facing one another, with a spacer body being inserted between the bearing bodies. Intervertebral prostheses of the type mentioned are known (DE-OS 2 804 936). With the previous design of these prostheses, which are primarily used as cervical vertebrae prostheses, there is a risk that, due to the relatively high mobility of the cervical vertebrae, the spacer body, which is preferably of essentially convex lens-shaped design in a known manner, is pushed out of the bearing sockets ; The spacer can slide relatively easily backwards out of the previous bearing shells, primarily in the case of movements that are referred to as "nodding the head". The object of the invention is therefore to create a total intervertebral prosthesis in which there is increased security against the spacer body sliding out of the socket-like recesses of the bearing bodies. According to the present invention, this object is achieved in that each bearing body has a depression in one of its longitudinal sides, seen from the level of the edge of its socket joint, and a projecting lug on the longitudinal side parallel thereto, the depression and the lobe being matched in this way that when the spacer body is inserted, the tab of one bearing body engages in the recess of the other bearing body. In the new design, the two bearing bodies engage with each other with their dorsal and ventral sides. As a result, their sliding movement on the spacer body is largely guided, so that forward and backward displacements of the prosthesis parts relative to one another are made more difficult. In addition, the spacer body is “caught” by the tab of one bearing body, which also overlaps the other bearing body in its depression during pitching movements, which prevents it from slipping out of the bearing sockets. The invention is explained in more detail below using an exemplary embodiment in connection with the drawing. 1 shows an exemplary embodiment of a cervical vertebrae prosthesis, which is inserted schematically between two cervical vertebrae, in a rear view and partly in section; Fig. 2 is the step II-II of Fig. 1. A bearing body 4, which has a rectangular or square outline, for example, is inserted into a recess made, for example, with a cutter, in a vertebral body 1, on which projections 3 of the vertebral processes are indicated on both sides of FIG. In the outer, i. H. The adjacent vertebra 1 facing surface of the bearing body 4 is a joint socket 7 embedded, which is adapted in shape and size to a spacer body 5, which is inserted between the bearing body 4 of two adjacent vertebrae 1 as a prosthesis body. The spacer body 5 is lens-shaped in the present example, but can also be a sphere, a sphere-like or an elliptical body. Each bearing body 4 has two anchoring pins 2 on its base surface facing the vertebrae, with which it is pressed or driven into drilled holes in the vertebrae 1 that have been prepared for operation. Considering the plane containing the edge of the joint socket 7 as the reference plane, each bearing body 4 has a depression 6 either on its dorsal or ventral side according to the invention, into which a projecting tab 8 of the other bearing body 4 engages as a counterpart. As the head moves up and down, the cooperating recess 6 and tab 8 move relative to each other; the lobe 8 either dives deeper into the recess 6 or slides out of it partially, without creating such a large gap between the two, especially during the downward movement, that the spacer body 5 can slide backwards out of the joint sockets 7. In order to guide the movement of the bearing bodies 4 even during lateral tilting movements of the head, the depressions 6 are additionally designed in the form of troughs with an oblique boundary 9, which is assigned oblique flanks 10 of the tab 8 running essentially parallel thereto. The bearing body 4 and the spacer body 5 are made of materials proven in implant technology, in particular high-molecular polyethylene (HDPE) for the bearing body 4 and bioceramics, especially high-purity and dense A1203, for the spacer body 5 have proven themselves. 2 5 10 15 20 25 30 35 40 45 50 55 S I-sheet drawings