DE3347983C2 - - Google Patents

Description

The invention relates to an acetabular endoprosthesis with the features according to the preamble of the patent Proverbs 1 or 2.

In a known acetabular endoprosthesis of this type (DE-OS 23 01 810) there is the use of bearings on took the joint ball from two approximately along one Diameter plane of the inner surface of the split bearing segments by a spring washer in the outer Ring grooves of the bearing segments are held together are. The ring grooves are close to the front one free edge of the bearing segments. To insert the Joint ball in the already implanted holder the bearing segments on the joint ball put on so that the surgeon with the joint ball the ge thereon and by the spring washer holding bearing segments in the receiving shell can push. In the inner surface of the holder there is an annular groove in which the on pushing process into the grooves of the bearing segments pressed spring ring pops up, so that this the joint ball together with the bearing segments  Form fit is fastened in the receptacle.

A disadvantage of this known acetabular endoprosthesis is that the spring ring the bearing segments during the insertion process may not be able to hold that one in any case allows perfect insertion. Because of the Operation available operating room, at for example in the area of a hip joint, very limited is, the surgeon touches it with his fingers seated joint straight up and must with your fingers the pressure required for insertion Articulated ball and the bearing segments placed above it apply. This easily leads to a counter side shift of the bearing segments because of this can only be held together by the spring washer moreover, not fully in the groove during the insertion process the bearing segments. When there is a shift the surgeon forced to re-align the Make storage segments and the insertion process to start over.

Another known endoprosthesis the bearing insert also consisted of two identically formed bearing segments, the parting plane of which is approximately vertical right to the level of the opening of the bearing insert and against the prosthesis when installed slipping out through a springy into the receptacle shell snap-in retaining ring are held (DE-AS 26 28 530). Are the cradle during the operation and the joint ball with the associated bone ends connected and are now intended to use the bearing and joint ball are inserted into the holder, so is it is necessary to first hold the retaining ring over the Slide the ball and then the two Apply bearing segments to the joint ball and  to hold onto it. Just like the one discussed above Known prosthesis must also hold on with special Care is done because the bearing segments are slippery on the Articulated ball are very mobile and already at a low easy bumping on the edge of the receiving tray can, so that the exact arrangement and insertion of Have to start something new. This also affects the Articulated ball seated retaining ring as a handicap because of it disrupts access to the bearing segments.

To the handling difficulties described above bearing operations to be avoided during the operation already have endoprostheses with one-piece bearing inserts been beaten (DE-OS 23 23 456, DE-OS 28 26 690, US-PS 38 63 273), in which the bearing use of his Opening edge has outgoing slits through which elastic fingers which can be bent outwards are formed. The deformation The finger becomes available after the joint ball is inserted in the installed state of the endoprosthesis by one on the Preventing screw-on ring nut or the like. But since the ring nut on the neck of the Joint ball must sit because it is deformable Can only hinder fingers if their diameter is smaller than the ball diameter is, it in turn interferes with the hold of the bearing insert on the joint ball. Beyond pose the slots interrupt the partially spherical bearings surface. This proves to be a disadvantage especially if - in another embodiment of endoprostheses this type - the use of bearings in the receptacle projections arranged on the outside of the fingers are held is that with recesses in the receptacle in positive engagement to intervene. Because when inserting the bearing insert with the joint ball arranged in it, the fingers have to move around the radial thickness of these projections is more inward be bow than they did after snapping into the Are receptacle. Because one exactly on the inner surface of this  Articulation of the fingers against such a strong bending would prevent, however, so that the bearing insert with the Ge Steering ball cannot be inserted into the cradle te, this means that in the area of the fingers the storage area of the bearing insert not exactly adapted to the joint ball can be, but has a certain game.

Finally, there is also an endoprosthesis with one piece Bearing use known (DE-AS 29 03 366), in the compliant Fingers in favor of one on the opening edge of the bearing insert arranged elastically bendable lip is dispensed with. Around this bearing insert against in the receiving tray To be able to keep pulling out, he also points to the outside side on a circumferential elastically deformable lip, which at the Push in behind a projection on the inner surface of the receptacle can snap into the shell. However, both sealing lips need to the insertion of the joint ball into the bearing insert or the bearing to allow use in the cradle, relatively be easily deformable with the result that they are also opposite a separating force, which is installed on the prosthesis works, allow a certain deformation. This expresses itself in an insufficiently tight fit of the joint ball and the Bearing use.

Starting from an acetabular endoprosthesis at the beginning written type, it is therefore an object of the invention, an Endopro propose these with a multi-part bearing insert, which however, when inserting the endoprosthesis like a one-piece bearing can handle use and still an almost uninterrupted Offers storage space for the joint ball.

According to the invention, this object is achieved by the features according to the characterizing part of claim 1 or 2.  

In the endoprosthesis according to the invention the bearing insert is therefore completely different from two designed storage segments, one of which (main Bearing segment) essentially the shape of a hemisphere shell and thus the joint ball without any Division can encompass while the other (bearing ring) forms a slotted ring that is elastic enough is expandable that it is pushed over the joint ball can be. Through a positive connection of the two bearing segments, the elements of which on each other facing edges, it is possible to both bearing segments from the outset onto the joint ball to put on and there like a one-piece bearing to keep the sentence, even under the influence of the emergency agile pushing force experience no displacement could hinder the insertion process. The holding elements, the in the inserted condition of the bearing insert with the Take the receptacle into positive engagement and that Prevent pulling out are on the outside of the slotted bearing ring arranged. The bearing ring forms in contrast to the described bearing inserts elastically deformable fingers also on the outside Edge area of the bearing insert except for the only one Slot continuous bearing surface for the joint ball.

As holding elements on the bearing ring that with the recording shell engage in positive engagement, either comes in in a known manner (DE-OS 23 01 810) one on the Groove provided on the outside of the bearing ring and a spring washer arranged therein or one on the outside protruding bead of the bearing ring into consideration. The Lock washer snaps into the inner surface of the opening provided bowl provided an annular groove, so that it partially in this and partly in the groove on the outside the bearing ring lies; the bead jumps due to the radial elasticity of the bearing ring in a corresponding  Groove the receptacle. The embodiment has the spring ring arranged in a groove of the bearing ring special advantage that the inner surface of the bearing insert of from the outset very precisely on the spherical surface of the joint ball can fit because during the insertion process a deformation of the Bearing use is not necessary. Rather, the spring is pushed ring during the insertion process until the groove is reached into the groove of the bearing ring.

Further advantageous configurations of the endoprosthesis according to the invention result from claims 3 to 12, of which the configurations according to claims 6 to 8 and 10 are already known per se.

Embodiments of the endo- Joint prosthesis are below based on the Drawings explained in more detail. In the drawings shows

Figure 1 is a schematic representation showing in cross section the endoprosthesis according to the invention in one embodiment as a prosthetic hip joint.

Fig. 2 is a sectional view of a receptacle shell of the endoprosthesis according to the invention;

Fig. 2a is a partial front view of the edge of the receiving tray according to Fig. 2;

Fig. 3a, b are sectional views of two embodiments of retaining rings;

Fig. 4a to 4c side view, front view and an enlarged detail of a tool for removing the implanted endo prosthesis;

Figure 5 is a sectional view of a bearing segment forming a bearing ring.

Fig. 6 is a sectional view of a main bearing segment, which together with the bearing ring of FIG 5 forms a bearing insert of the endoprosthesis according to the invention;

FIG. 7 shows an end view of the bearing ring according to FIG. 5;

. Fig. 8 is a sectional view analogous to Figure 5 of a modified embodiment of the bearing ring;

Fig. 9 is a representation of the mutually associated edges of the bearing ring and of the main bearing pad of FIGS 5 and 6 in an enlarged scale, which allow a mutual form-fitting connection.

FIG. 10 is a bearing insert of the endoprosthesis according to the invention in the assembled state;

FIG. 11a to 11d show successive phases of the pushing on of the bearing insert of FIG. 10 on a joint ball of the endoprosthesis, and

Fig. 12 shows a cross section through the bearing insert and the receiving shell in the assembled state with the joint ball.

In Fig. 1 an inventive acetabular endoprosthesis is illustrated in one embodiment as a prosthetic hip joint 10 in the form of an implanted. The hip joint 10 has a thigh insert 12 with a joint ball 16 , a bearing insert 20 , a receiving shell 30 and a retaining ring 40 . The thigh insert 12 comprises a shaft 14 , with which it is fixed in the hollow of the proximal thigh bone with the aid of a casting agent 15 , and a neck 18 .

The receiving shell 30 ( FIGS. 2, 2a) has a smooth outer spherical surface 31 which runs out on an outer circular surface 32 which tapers conically outwards. Furthermore, the receiving shell 30 has an inner spherical surface 33 which converges with the inner end of a cylindrical inner surface 34 . The outer end of the cylindrical inner surface 34 merges into a conically tapering circular surface 35 which intersects with the circular surface 32 as shown in the drawing. In the vicinity of the edge of the receiving shell 30 , an inner circular circumferential groove 37 is provided in its cylindrical inner surface 34 for receiving a retaining ring 40 according to FIGS . 3, 3a. The outer spherical surface 31 is closely adapted to the acetabular cartilage or to the natural acetabulum ( Fig. 1), and the inner spherical surface 33 and the cylindrical inner surface 34 together form a support 38 for receiving the bearing insert 20 and are on the outer surface customized. The receiving shell 30 has a plurality of grooves 39 which, starting from the annular surface 35 , extend into the cylindrical inner surface 34 , as shown in FIGS. 2, 2a.

The bearing insert 20 consists of a radially slotted bearing ring 61 or 71 according to FIGS. 5 and 8 and a generally spherical shell-shaped main bearing segment 51 according to FIG. 6. The circular bearing ring 61 ( FIG. 5) has an outer circular circumferential groove 19 , while the bearing ring 71 ( FIG. 8) has a partially or completely circular bead 43 on its outside. As can be seen from FIG. 6, the main bearing segment 51 has an outer spherical surface 52 , a cylindrical outer surface 53 and a spherical inner surface 55 . At its front end, a circular, radially outwardly extending projection 58 and a circular, radially inwardly opening groove 59 are seen in front.

The bearing ring 61 ( FIG. 5) has an outer cylindrical peripheral surface 63 , in which the circumferential groove 19 is provided for receiving the retaining ring 40 . In addition to this, the bearing ring 61 has a conical ring surface 24 , an oblique conical ring surface 26 and a partially spherical inner surface 65 . At its rear part, the bearing ring 61 is provided with a circular, radially inwardly extending ring projection 68 and with a circular, radially outwardly opening annular groove 69 . Similarly, the bearing ring 71 ( FIG. 8) is provided with an outer cylindrical circumferential surface 73 , an annular surface 24 widening conically outwards and an annular surface 26 tapering conically inwards, and also with a partially spherical inner surface 75 . At its rear end, the bearing ring 71 has a circular, radially inwardly extending ring projection 78 and a circular, radially outwardly opening annular groove 79 . The bearing rings 61 and 71 are made of a suitable flexible material and are radially slotted at 64 and 74, respectively, in order to enable radial expansion for connection to the main bearing segment 51 .

Before assembly with the joint ball 16 ( Fig. 1), the main bearing segment 51 and the bearing ring 61 and 71 are connected to a sub-assembly in order to facilitate the hand handling by the surgeon for the reasons mentioned above. For this purpose, the bearing ring 61 (before the operation and before the sterilization or packaging) is expanded outwards in order to allow the ring projection 68 to be pushed over the ring projection 58 . After the bearing ring 61 has been contracted again , the annular projection 68 is taken up in the annular groove 59 , while the annular projection 58 enters the annular groove 69 , as a result of which the main bearing segment 51 and the bearing ring 61 form the subassembly shown in FIG. 10.

9 and 10, as is apparent from the Fig., Of the flexible retainer ring is received in the bearing ring 61 40 in the groove 19, thereby supporting the cohesion of the main bearing segment 51 and the bearing ring 61 in the said sub-assembly. It is within the scope of the invention to produce the bearing ring 61 from a more inflexible material and to assemble it from a multiplicity of part-circular segments which are provided on their outer surface with a groove corresponding to the groove 19 for receiving the flexible retaining ring 40 , which then both forms the part-circular segments holds together as well as on the main bearing segment 51 .

The spherical inner surface 55 of the main bearing segment 51 and the part-spherical inner surface 65 and 75 of the bearing ring 61 and 71 together form a spherical cavity 57 which is adapted to the joint ball 16 and receives this in the assembled state. It goes without saying that the diameter of the opening formed by the edge of the annular surface 26 is smaller than the diameter of the joint ball 16 (cf. FIG. 1).

Figs. 11a to 11d illustrate the joining of the bearing insert 20 with the joint ball 16, wherein the bearing ring is 61 application. As shown in FIGS. 11a and 11b, the bearing ring 61 expands radially outward against the action of the retaining ring 40 after the articulation ball 16 has been forced into the ring surface 26 . The manual force exerted by the operating surgeon, which is indicated by arrows 81, 83 , is more than sufficient for this. As a result, the bearing ring 61 can be pushed over the joint ball so that it is received in the spherical cavity 57 . Then, the tray 30 is insert through the bearing 20 is pushed, so that the annular surface 35 of the receiving tray 30 comes to the retaining ring 40 engages and presses the latter radially inwards, so that it completely inner half of the outer circular peripheral groove 19 of the bearing ring 61 comes to rest. As a result, the receiving shell 30 slides over the retaining ring 40 until it strikes with its spherical inner surface 33 on the rear outer spherical surface 51 of the bearing insert 20 . In this position, the circumferential groove 19 of the bearing ring 61 is axially aligned with the inner, circular circumferential groove 37 of the receiving shell 30 , whereupon the retaining ring 40 expands radially outward, so that it partly inside the groove 37 and partly inside the groove 19 is included. The retaining ring 40 thus performs a holding function by holding the receiving shell 30 and, via the bearing insert 20, the joint ball 16 accommodated therein, so that it separates (for example an axial displacement) between the bearing insert 20 with the joint ball stored therein and the receiving shell 30 prevented during joint rotation. The individual parts of the endoprosthesis then assume the position shown in FIG. 12.

The arrangement of the bearing insert 20 using the bearing ring 71 according to FIG. 8 takes place in the same way as is shown in FIGS. 11a to 11d. When inserting the assembly thus created in the bearing shell 30 of the bead in the groove 37 enters 43 a, which is connected to the receiving tray 30 via the bearing insert 20 with the joint ball sixteenth It goes without saying that between the partially spherical inner surface 75 of the bearing ring 71 and the joint ball 16 , a certain distance must first be provided to allow the compression of the bearing ring 71 when the bead 43 enters the cylindrical inner surface 33 of the receiving shell 30 .

The bearing insert 20 is divided along a plane 87-87 ( FIGS . 5, 6) which is aligned parallel to the opening plane 85-85 . The opening in the opening plane 85-85 is defined by the edge of the annular surface 26 .

As shown in Fig. 12, the overlap angle γ is about 30 ° and the intended rotation or pivoting movement that allows the endoprosthesis is about 60 °. This overlap angle γ leads to a high separation resistance of the endoprosthesis, the building and dismantling forces of which are, however, very low. For the radial expansion of the bearing ring 61, 71 for the purpose of introducing the joint ball 16 , it is only necessary to bend a thin retaining ring 40 radially outward and / or to bend open the slotted bearing ring 61, 71 . Accordingly, the receiving shell 30 can be easily connected to the bearing insert 20 and the articulated ball 16 therein by a slight radially inward or outward deformation of the thin retaining ring 40 , whereupon, however, a large separation resistance is obtained. Furthermore, since no deformation of the bearing insert 20 is required for the assembly process, there is also no axial play, as a result of which a well-fitting bearing insert is achieved.

The thigh insert 12 and the receiving shell 30 can be made of a rigid implantable metal, e.g. B. corrosion-resistant steel, a titanium or cobalt alloy or from certain types of ceramics. The bearing insert 20 can consist of a material which is suitable for a hinge connection with the hinge ball 16 and has sufficient strength to produce an adequate displacement and separation resistance as well as sufficient flexibility to enable the described function of the bearing ring 61 or 71 . Ultrahigh molecular weight polyethylene (UHMWPE) is suitable for this. Ceramic is suitable for the main bearing segment.

The tool shown in FIGS. 4a to 4c is used to disassemble the implanted endoprosthesis. This can be pushed with the opening 48 over the neck 18 of the thigh insert 12 , and the tips 44 are then inserted into the grooves 39 of the receiving shell 30 , so that beveled edges 47 on the tips 44 (see. Fig. 4c) over the Slide the retaining ring 40 and press it fully into the groove 19 . So that the bearing insert 20 can be removed ent with the joint ball 16 of the receiving tray 30th

However, the design of the bearing insert 20 also enables a different type of separation of the endoprosthesis. For example, rings 61 and 71 inwardly extending holes or slots can be provided near the slots 64 and 74 in the bearing, into which the ends of clamps which are usually present in the operating room can be inserted in order to thereby compress the bearing ring and hold it in place Reduce scope. As a result, either the retaining ring 40 of the bearing ring 61 or the bead 43 of the bearing ring 71 from the groove 37 of the receiving shell 30 is released , so that the bearing insert 20 with the joint ball 16 can be separated from the receiving shell 30 by manual application of force.

Claims (12)

1. joint socket endoprosthesis, with a receptacle that can be fastened to a bone and with a shell that can be inserted into the receptacle, composed of two bearing segments, a bearing insert for receiving a joint ball that can be fastened to another bone, which forms a part-spherical bearing surface for the joint ball and in Assembled state of the endoprosthesis overlaps the joint ball with its bearing surface by more than half and is held in the receiving shell by holding elements engaged with the receiving shell in form-locking manner against pulling out, characterized in that the bearing insert ( 20 ) by a hemispherical head -Bearing segment ( 51 ) and formed by a bearing ring ( 71 ), the parts by means of complementary positive locking ( 58, 59; 78, 79 ) at their mutually associated edges to a uniformly manageable bearing insert ( 20 ) can be connected to each other and that the bearing ring ( 71 ) through a single slot elas table is expandable and has on its outside ( 73 ) with the receiving shell ( 30 ) in positive engagement engagement elements ( 43 ). 2. acetabular endoprosthesis, with a receptacle that can be fastened to a bone and has a groove on its inner surface, a bearing insert that can be inserted into the receptacle and is composed of several bearing segments for receiving a joint ball that can be fastened to another bone and that has a part-spherical bearing surface for the joint ball forms, in the assembled state of the endoprosthesis overlaps the joint ball more than half and has on its outer surface a groove for receiving a resilient retaining ring, which engages in the groove of the receiving shell on the bearing insert positively against pulling out of the receiving shell holds, characterized in that the bearing insert ( 20 ) is formed by a hemispherical main bearing segment ( 51 ) and by a bearing ring ( 61 ) which by means of complementary form-fitting parts ( 58, 59; 68, 69 ) at their mutually associated edges a uniformly manageable warehouse insert ( 20 ) can be connected to each other, and that the bearing ring ( 61 ) is slotted and has on its peripheral surface the groove ( 19 ) for receiving the retaining ring ( 40 ). 3. Endoprosthesis according to claim 1 or 2, characterized in that for connecting the main bearing segment ( 50 ) to the bearing ring ( 61, 71 ) at their mutually associated edges each have a radially opening annular groove ( 59; 69, 79 ) and a radially projecting ring projection ( 58; 68, 78 ) are easily seen, which are positively insertable into one another in the elastically expanded state of the bearing ring ( 61, 71 ). 4. Endoprosthesis according to one of claims 1 to 3, characterized in that the bearing ring ( 61, 71 ) is radially elastically together compressible. 5. Endoprosthesis according to one of claims 1 and 3, 4, characterized in that on the circumferential surface of the bearing ring ( 71 ) as the positive engagement with the receiving shell ( 30 ) forming a bead ( 43 ) is formed, which when inserting the bearing insert ( 20 ) can snap into the receiving shell ( 30 ) in a groove ( 37 ) formed in the inner surface of the receiving shell ( 30 ). 6. Endoprosthesis according to one of claims 1 to 5, characterized in that the outer surface of the main bearing segment ( 51 ) is formed by a partially spherical outer surface ( 52 ) and a cylindrical outer surface ( 53 ) located near the edge, and that the bearing ring ( 61, 71 ) has a substantially cylindrical outer peripheral surface ( 63, 73 ) which, when the bearing ring ( 61, 71 ) is combined with the main bearing segment ( 51 ), with the cylindrical outer surface ( 53 ) of the main bearing segment ( 51 ) flees. 7. Endoprosthesis according to claim 6, characterized in that the receiving shell ( 30 ) one to the part-spherical outer surface ( 52 ) and the cylindrical outer surface ( 53 ) of the main bearing segment ( 51 ) and to the cylindrical outer peripheral surface ( 63, 73 ) of the bearing ring ( 61, 71 ) has a complementarily designed inner surface ( 33, 34 ). 8. Endoprosthesis according to one of claims 1 to 7, characterized in that the bearing ring ( 61, 71 ) has an outgoing from its front edge, tapering towards the inner surface ( 65, 75 ) of the bearing ring tapering ring surface ( 26 ). 9. Endoprosthesis according to one of claims 1 to 8, characterized in that the bearing ring ( 61, 71 ) has an outgoing from its front edge, tapered to the outer circumferential surface ( 63, 73 ) extending ring surface ( 24 ). 10. Endoprosthesis according to one of claims 1 to 9, characterized in that the receiving shell ( 30 ) has at its edge a tapered annular surface ( 35 ) to the inner surface ( 33, 34 ) of the receiving shell. 11. Endoprosthesis according to claim 10, characterized in that the receiving shell ( 30 ) has at its front edge a conically widening annular surface ( 32 ) extending towards the outer surface ( 31 ) of the receiving shell. 12. Endoprosthesis according to one of claims 4 to 11, characterized in that the receiving shell ( 30 ) has at least one starting from its front edge, up to the groove ( 37 ) extending groove ( 39 ) in its inner surface ( 34 ) in which to solve the positive engagement of the bearing ring ( 61, 71 ) with the receiving shell ( 30 ) a tool ( 46 ) can be inserted.