AU2004266431B2

AU2004266431B2 - Intervertebral disk prosthesis

Info

Publication number: AU2004266431B2
Application number: AU2004266431A
Authority: AU
Inventors: Arnold Keller
Original assignee: Cervitech Inc
Current assignee: Cervitech Inc
Priority date: 2003-07-21
Filing date: 2004-06-16
Publication date: 2009-06-11
Anticipated expiration: 2024-06-16
Also published as: IL172608A0; BRPI0412782A; JP2007533335A; DE502004006595D1; ZA200601352B; CA2531144A1; EP1646337B1; ES2302000T3; EP1512384A1; WO2005018508A1; EP1646337A1; ATE389375T1; CN1826091A; PL1646337T3; KR20060056337A; AU2004266431A1; MXPA06000747A; CN100563603C; RU2340312C2; RU2006105201A

Description

Cervitech, Inc. CERTO26PWO D/so 5 Intervertebral disk prosthesis A known type of intervertebral disk prosthesis (WO 01/01893) has two metal cover plates and a polyethylene prosthesis core which forms a pair of slide surfaces 10 with one of the two cover plates and is fixed on the other cover plate. For this fixing, the cover plate is provided with edge ridges whose undercut connection profile cooperates with a complementary connection profile on the underside of the prosthesis core. On the 15 right and left lateral edges of the cover plate and of the prosthesis core, such connection profiles are provided parallel to one another. In addition, there is one such profile running in a straight line on the dorsal edge of the cover plate and of the prosthesis 20 core. There is no such profile on the ventral edge, with the result that the prosthesis core can be pushed into the connection profiles of the cover plate from the ventral direction. The prosthesis core is secured in the assembled position by a pair of locking elements 25 provided on the ventral edge. Although the connection profiles are produced almost free of play, an important concern in prosthesis production is to ensure that, even in the case of production tolerances, it is possible to rule out any movement of the prosthesis 30 core relative to the cover plate holding it. In particular, rotation movements of the prosthesis core relative to the cover plate holding it must be ruled out. 35 The prior art gives no indications as to how this problem could be solved. FR-A-2718635 discloses connection profiles only on parallel, lateral edges of the cover plate. They are absent in all the nonlateral - 2 and nonparallel edge areas. For knee prostheses, FR-A 2632516 discloses the fixing of a polyethylene part in a retaining profile by means of horseshoe-shaped connection profiles, but this does not afford any guarantee that the 5 nonparallel sections of the connection profiles will also remain in engagement with one another. For a shoulder prosthesis, FR-A-2780635 discloses the fixing of a polyethylene part on a retaining part by means of connection profiles extending exclusively at an angle with 10 respect to one another. This cannot be adapted to the shape requirements of an intervertebral disk prosthesis. The present invention provides in a first aspect an intervertebral disk prostheses in which the connection 15 profiles include at least one pair of connection profile sections which are symmetrical with respect to the AP direction and are arranged at an angle to one another. AP direction signifies the anteroposterior direction. The profile sections arranged at an angle to one another 20 according to embodiments of the invention create a triangular configuration which counteracts twisting of the prosthesis core relative to the cover plate if play exists between the connection profiles of the cover plate and of the prosthesis core. The connection profiles may 25 basically be made up exclusively of such profile sections arranged at an angle to one another. However, these may also be provided additionally to connection profiles arranged in parallel on the lateral edges of the cover plate and of the prosthesis core. They are intended to 30 run in an substantially straight line and are preferably arranged at least on the dorsal side. The angle between the profile sections arranged at an angle to one another typically is not greater than 1500. The limit preferably lies for example at 1400. 35 The present invention provides in a second aspect an intervertebral disk prosthesis with two cover plates and a N:Terth\Cases\atent\59000-5g9g995g493 AU\Specis\Amended Speci Pages 2 and 5.doc 19105109 - 2a prosthesis core which is connected to one of the cover plates by means of connection profiles which are undercut in a complementary manner, characterized in that the connection profiles include at least one pair of profile 5 sections which are symmetrical with respect to the AP direction and are arranged at an angle to one another. N:\Perth\CsesPatent5OOO.5 99 \P59493.AU\Specis\Amended Specl Pages 2 and 5.doc 19105O09 - 3 The invention is explained in more detail below with reference to the drawing which depicts an advantageous illustrative embodiment and in which: 5 Fig. 1 shows a perspective view of the end plate with the prosthesis core secured on it, Figs 2 to 4 show different views of the same end 10 plate without prosthesis core, and Figs 5 and 6 show perspective views of the prosthesis core. 15 The end plate 1, which is normally used as the lower end plate, has an approximately oval contour and comprises a toothed fastening surface 2 for bearing on the vertebral body and a flange 3 which comes to lie on the ventral side of the vertebral body and can be 20 screwed to the latter via screw holes 4. On that side opposite the fastening surface 2, the one normally lying to the top, the cover plate 1 forms a support for the prosthesis core 5. This support consists of a plane surface 6 and, surrounding the latter, an edge 7 which 25 is composed of two parallel sections 7' on the lateral sides of the plate and of a dorsal edge 7'' . The outer contour of the edge 7 corresponds to the oval contour of the cover plate. On its side facing toward the surface 6, the edge is provided with a profile ridge 8 30 and, below the latter, with an undercut 8'. The connection profile thereby formed on the inner side of the edge 7 runs in a straight line in the lateral sections 7' and parallel on both sides. In the dorsal section 7'', the connection profile is composed of two 35 sections 9. In each of these sections, the connection profile runs in a straight line. The profiles of both sections are arranged symmetrically with respect to the AP axis 10 of the implant and enclose an angle a which, in the example shown, is 1400.

-4 The top of the edge 7 forms a plane surface 6' which runs parallel to the support surface 6 and likewise forms a support surface for the prosthesis core. 5 The flange 3 of the cover plate has a slit 11 which runs perpendicular to the connection profile 6 and whose function is explained later. 10 On its top 12, the prosthesis core 5 forms a slide surface which cooperates with the second cover plate (not shown) to form a hinge. The contour of the prosthesis core is identical to that of the cover plate 1. On its underside, it has a plane surface 13 which is 15 intended to bear on the support surface 6 of the end plate 1 and has substantially the same contour shape. It is limited by a connection profile which is formed by a profile ridge 14 and an undercut 14' . This connection profile corresponds in a complementary 20 manner to the connection profile 8, 9 of the edge ridge 7 of the cover plate 1. In particular, the connection profile is composed of two lateral sections 15 and two dorsal sections 16 which correspond respectively to the lateral and dorsal sections of the edge 7 of the cover 25 plate 1 and can cooperate with these in a form-fitting manner. Outside the connection profile 14, 14', on the underside of the prosthesis core 5 there is a plane 30 surface 17 which corresponds to the support surface 6' on the top of the edge 7 of the cover plate 1 and cooperates with this when the prosthesis core is mounted on the cover plate 1. 35 The prosthesis is assembled by means of the prosthesis core being pushed with its connection profile 14, 14' into the corresponding connection profiles 8, 8' from the direction of the open ventral side. When the prosthesis core has been pushed in fully, its profile - 5 ridge 14 fits, not only in the area of the lateral sections 7' but also in the area of the dorsal section 7'', into the undercut 8' of the edge 7 of the cover plate, the connection profiles lying on one another with 5 substantially full-surface contact. At the location where the slit 11 is situated in the gap 3, the prosthesis core has a groove 18 which is flush with the gap 11 when the prosthesis core has reached its end 10 position in which the dorsal connection profiles abut one another. A plate (not shown) is pushed into the gap 11 and the groove 18 and secures the prosthesis core in this position relative to the cover plate 1. The plate is in turn secured by means of also having a bore at the 15 location of the screw hole shown on the left in Fig. 3, through which bore a fastening screw extends. By virtue of the fact that the connection profiles of the prosthesis core and of the cover plate are equipped, 20 respectively, with the sections 9 and 16 which each form a triangle, it is possible, in comparison with known prostheses, to obtain increased stability of the position of the prosthesis core relative to the cover plate 1. In particular, its stability with respect to relative 25 movements in the sense of rotation is thereby increased. It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the 30 common general knowledge in the art, in Australia or any other country. N:\Perth\CasesPatent\5900-59999\P59493.AU\pecis\Amended Spec Pages 2 and 5.doc 19105/09

Claims

1. An intervertebral disk prosthesis with two cover plates and a prosthesis core which is connected to 5 one of the cover plates by means of connection profiles which are undercut in a complementary manner, characterized in that the connection profiles include at least one pair of profile sections which are symmetrical with respect to the AP direction and 10 are arranged at an angle to one another.

2. The intervertebral disk prosthesis as claim in claim, characterized in that the profile sections arranged at an angle to one another run in a substantially 15 straight line.

3. The intervertebral disk prosthesis as claim in claim 1 or 2, characterized in that the profile sections arranged at an angle to one another are arranged on 20 the dorsal side and are held in engagement by means arranged on the ventral side.

4. The intervertebral disk prosthesis as claimed in claim 3, characterized in that the profile sections 25 arranged on the dorsal side are provided in addition to a pair of laterally arranged profile sections.

5. The intervertebral disk prosthesis as claimed in claim 1 or 2, characterized in that the angle between 30 the profile sections arranged at an angle to one another is not greater than 1500.

6. An intervertebral disk prosthesis substantially as herein described with reference to the drawings. 35 N:\Perth\Cases\Patent\59000-59999\P59493.AU\SpeciswAmended Claim Page 6.doc 12/0509