DE4215888A1 - Acetabulum for high joint prosthesis - has shell-shaped cap with several apertures for anchoring elements with outer anchoring set - Google Patents

Abstract

The cap (1) has a rotation-symmetrical outer shell surface, in whose inside is to be mounted the femur head of the prosthesis. The cap has several through apertures (7), each for an anchoring element (8) with an external anchoring set (14). The anchoring element is so held in the respective aperture that it can move from it starting position, with the anchoring set within the cap outer shell surface (5), into an anchoring position with the anchoring set protruding beyond the shell surface. ADVANTAGE - No need for cementing, and long-term fixation.

Description

The invention relates to an acetabular cup for a hip joint Endoprosthesis with a rotationally symmetrical, i. a. in the essential spherical cap-shaped outer envelope surface send, bowl-shaped (outer) cap that at an implan tation with its outside in a correspondingly milled Insert acetabulum and anchor it in it, and in the interior of which the femoral head of the endoprosthesis is to be supported.

Today there are essentially in medical application Chen two categories for attaching a hip socket in the Pelvic bones. Either the so-called primary fixation with the help reached by bone cement or it is pressed or screwable hip cups used, the shape or strength  are to be firmly anchored. Doing this with everyone Implantation techniques specific difficulties and consequences problems, which ultimately lead to serious damage against the prosthesis itself or the surrounding bone being able to lead.

For cemented pans (e.g. made of polyethylene) is as The main disadvantage is the insufficient long-term stability to name, which is partly the result of tribological properties materials used in medicine. Beyond that, however, a physiological bone remodeling is going on observed the implants at which the initial form closure can be lost and due to relative movements between implant and bone additional abrasion from the outside on the outside of the acetabulum. Such abrasion dusts of materials that are compatible with the tissue lead to pro gressive Eastern Colysen and for the destruction of the bone substance with the corresponding consequences. Attempts of recent years by using more abrasion-resistant materials or also by Metal reinforcements of polyethylene pans the described Avoiding disadvantages does not lead to the desired success guided.

With cement-free implantation techniques today we three possible solutions, each with its own disadvantages followed:

For example, acetabular cups are made of high-strength aluminum oxide ceramic knows the excellent tribological properties own, the production of which, however, is extremely expensive is intensive. Incidentally, there are also implantation techniques difficult, so these acetabular cups are rare cases have been used, especially since the primary supply was found to be insufficient.

They are also in the field of cementless implanta  tion technique made of metal acetabular cups have winch, which screw into the bone tissue is. These acetabular cups are usually also available with a Designated insert made of polyethylene or ceramic provided, which is held in the outer cap and on his the open end of the cap an i. a. ku has gel-shaped bearing surface, which the bearing surface for forms the femoral head of the prosthetic hip joint.

However, it has been shown that these acetabular cups according to Im plantation can have a migratory behavior, which u. a. on the height of the thread and the volume of that Of the entrapped bone. Especially at such acetabular cups with low thread flanks result in a significant easing rate, while at higher Thread flanks affect the adjacent soft tissues can be pulled, so that after implantation restbe difficult to remain. There is also one in these screwable acetabular cups if necessary a change of the Positioning during the implantation as well as a possibly subsequent re-operation becomes extremely difficult and often not possible.

Finally, are part of the cementless implantation technology known. Clamping pans known from an i. a. bullet dome-shaped or spherical bowl-shaped cap Metal, which is milled in a corresponding Bone tissue is pressed in, leaving the outer envelope surface such a cup-shaped clamping pan by a circumference difference from the so-called pan storage created by milling deviates to create a primary fixation. However, since the stability of this fixation method is rare is enough, i. a. additional bone screws are provided, by means of which a clamping pan is to be additionally fixed. However, such bone screws can only be used in the os Fix the ileum as the bone thickness of the other neighboring one  Bones are not sufficient for the insertion of bone screws enough. If there are relative movements between the kno tissue-fixed bone screws and the acetabulum, see above this can lead to broken screws or broken bones as well as others lead to adverse consequences.

The present invention has for its object a Generic hip socket to create, which is good Primary fixation and long-term fixation with a relative simple implantation technique allows cementless implantation, which i. a. a re-operation that may become necessary easily possible, and in addition with good tri biological properties and satisfactory biocompatibility is relatively inexpensive to manufacture.

According to the invention, this object is achieved by that the cap has at least two through openings, in each of which one with little on its outer face anchoring element provided at least with an anchoring approach held so (i.e. arranged and connected to the cap) is that it is from a starting position in which the Anchoring approach within the outer envelope surface of the cap is to be moved into an anchoring position, in which the anchoring approach laterally over the outer shell surface of the cap protrudes and therefore after an implantation engages in the acetabular tissue surrounding the acetabulum.

A preferred embodiment of the present invention is that the through holes are essentially radial to the central axis or axis of symmetry of the cap and thus also overall to the central axis of the acetabulum fen, although the through openings are basically visible Lich could have a different course, as long as this is not parallel to the central axis of the cap.

Although basic to the realization of the inventive principle  additionally two through openings and thus two anchors sufficient elements, it has been shown that for a reliable fixation is useful if more than two ver Anchor elements are present, which are preferably essentially Chen evenly over the circumference of the cap and thus the Acetabulum are distributed, d. H. so that in the Top view of the cap between two adjacent ones Through openings essentially the same Zen tri angle to the central axis is included. An education with five through openings and accordingly five anchoring elements has generally been particularly useful shown.

A most preferred embodiment of the present invention manure is that the through openings as slots are trained, although in principle, for example se could be designed as bores.

In an embodiment in which the through openings are slit-shaped, there are the anchoring elements elements preferred as tabs or lamellae and are wide rer embodiment of the present invention preferred pivotally held on the cap, conveniently each at its end section facing the edge of the cap, since a spreading effect can be realized in this way, which is at a tendency of the cap, from the milled out Ladle bearing of the acetabular tissue to emerge, still ver strengthens if the anchoring approaches in an appropriate manner are trained like this in more detail below is explained.

The anchoring approaches of the anchoring elements are before pulls in the manner of teeth formed in a lateral Chen top view of a side surface of an anchoring element mentes can be substantially triangular and preferably a tooth head designed as a cutting edge  indicate how this is explained in more detail below is.

Furthermore, it has proven to be particularly useful if the anchoring elements each with several anchoring devices sentences are provided, preferably in the longitudinal direction of a formed as a tab or the like. Anchoring element are arranged one another.

The invention is based on an embodiment further explained with reference to a drawing. It shows

Figure 1 seen a central section through an inventive acetabular cup in the direction of section line II in Figure 3, wherein the anchoring elements are in their starting position.

FIG. 2 shows a representation according to FIG. 1, in which the anchoring elements are in their anchoring position after the implantation;

Figure 3 is a plan view of the outside of the cap in the direction of arrow III in Figure 1, the anchoring elements are shown in their initial position with solid lines and in their anchoring position with dash-dotted lines.

Figure 4 is seen a plan view of the inside of the cap in the direction of arrow IV in Figure 2, ie with anchoring elements located in the anchoring position; and

Fig. 5 is an enlarged perspective Dar position of an anchoring element.

The drawing shows a (outer) cap, generally designated 1 , of an acetabular cup, generally designated 2 , for a hip joint endoprosthesis which, in addition to cap 1, also has a shell-shaped bearing body, designated 3 (see FIG. 2), as will be explained below.

The cap 1 is rotationally symmetrical to its central axis 4 and has a substantially kugelkalottenför shaped outer envelope surface 5 , which is to be used with an implantation with its outside in a correspondingly milled acetabulum, not shown in the drawing. The cap 1 is provided on its outside with concentric to the central axis 4 circumferential grooves 6 , into which cancellous bone should grow after the implantation, although these grooves are not mandatory.

The cap 1 has five through openings 7 , which are designed as slots and extend radially to the central axis 4 of the cap 1 , the through openings 7 being arranged uniformly distributed over the circumference of the cap 1 (see FIGS. 3, 4).

In the slot-shaped through openings 7 , an anchoring element 8 is held, ie arranged here and connected to the cap 1 , as is explained below.

The anchoring elements 8 are each ausgebil det as tabs and at their edge 9 of the cap 1 facing Endab section hinged to the cap 1 . As the pivot axis is used on the side surfaces 10 , 10 of the anchoring element 8 projecting pin 11 which is mounted in a recess 12 of the cap 1 . For this purpose, the cap 1 is provided on the end face of its edge 9 with a groove which forms the recesses 12 for the storage of the pivot axes of the anchoring elements 8 formed from the pins 11 . The groove 12 is closed at its end facing the edge 9 of the cap 8 by a ring 13 , the height h of which is so much smaller than the height H of the groove-shaped recess 12 that the pins 11 can pivot in the remaining recess 12 .

The anchoring elements 8 are each provided with two anchoring lugs 14 on their outer end face. The anchoring lugs 14 , which are each arranged one above the other in the longitudinal direction of the la-shaped anchoring elements 8 , are each formed as teeth which are triangular in a side plan view of a side face 10 of the anchoring element 8 , the tooth heads 15 each forming a cutting edge.

The anchoring lugs 8 each have an edge 9 of the cap 1 facing the lower edge 16 which in the anchoring position ( FIG. 2) is substantially perpendicular to the central axis 4 of the cap 1 .

The anchoring elements 8 are thus held on the cap 1 so that they each pivot from their initial position ( Fig. 1), in which the anchoring lugs 14 are located within the outer envelope surface 5 of the cap, in an anchoring position ( Fig. 2) are in which the anchoring lugs 14 each project laterally over the outer envelope surface 5 of the cap 1 . As can be seen in particular from FIG. 2, the tab-shaped anchoring elements 8 fill the slot-shaped passage opening 7 assigned to them in the anchoring position ( FIG. 2) in essence, so that hardly any cancellous bone in the cap 1 or after implantation. whose slot-shaped through openings 7 can grow into it. As can also be seen from Fig. 2, the anchoring elements 8 in the anchoring position affect the inner envelope surface 17 of the cap 1, each with its inner end face 8 '. The anchoring elements 8 can be provided at their end section facing away from the articulation end with an eyelet or hook-shaped extension 18 projecting from the inner end face 8 ', the purpose of which will be explained further below.

The cap 1 is seen with a central threaded bore 19 , in which first - that is, when the anchoring elements 8 are still in the starting position according to FIG. 1 - a threaded pin 20 is screwed in, which has a slot 20 'at its lower end. is provided for engagement for a screwdriver or the like. In Implantationszu stood a plug 21 is screwed into the threaded bore 19 .

As has already been mentioned above, is arranged also referred to as shell-shaped inlay stock body 3 in the cap 1, which directed towards the open side of the cap 1 spherical segment-shaped inner face 3 'forms the bearing surface for the femoral head, not shown, of the endoprosthesis. The bearing body 3 consists of ceramic, while the cap 1 consists of a CrCoMo steel.

As can be seen from FIGS. 1 and 2, the inner envelope surface 17 of the cap 1 is conically tapered from the edge 9 thereof.

The operation of the acetabular cup 2 according to the invention and the corresponding implantation technique are as follows:

After the acetabular tissue of the acetabular tissue has been milled out in accordance with the outer envelope surface 5 of the cap 1 of the hip socket 2 , the cap 1 is inserted into the socket bearing 19 with the threaded pin 20 screwed into the threaded hole 19 , with all anchoring elements 8 in the inside are pivoted starting position, in which therefore their anchoring lugs 14 lie within the outer envelope surface 5 of the cap 1 . Then a tool 22 , which is provided on its head 22 'with a threaded hole 23 , the thread of which corresponds to the external thread of the threaded pin 20 , is screwed onto the threaded pin 20 . The lateral surface 24 of the head 22 'is conical like the inner re envelope surface 17 of the cap 1 . When screwing on the tool 22 on the threaded pin 20 therefore comes first the edge 25 of the head 22 'with the inner end faces 8 ' of the anchoring elements 8 and each swings progressively about its pivot axis 11 to the outside. The tooth tips 15 of the anchoring approaches 14 thus pass over the outer envelope surface 5 of the cap 1 and penetrate progressively into the bone tissue.

In the end position of the tool, which is shown in Fig. 2 in the right part with dash-dotted lines, the lateral surface 24 of the head 22 'of the tool 22 is on the inner envelope surface 17 of the cap 1 and on the inner end faces 8 ' of the anchoring elements 8th at which are then in their anchoring position, in which the tooth-shaped anchoring lugs 14 protrude radially beyond the outer envelope surface 5 in the manner shown in the left part of FIG. 2 and engage in the acetabular tissue. In the anchoring position, the tool 22 is then unscrewed from the threaded pin 20 and the threaded pin 20 itself is screwed out of the threaded bore 19 , which is possible by engagement of a screwdriver or the like in the slot 20 'in a simple manner. Then the plug 21 is screwed into the threaded bore 19 and the bearing body 3 is inserted, as can be seen from the left part of FIG. 2. The implantation process is now complete.

If a reoperation is required later or the hip socket 2 may need to be repositioned during an operation, the surgeon can grip the bore 18 'of the eyelet-shaped extension 18 of the respective anchoring element 8 with a suitable hook-shaped tool and pivot it radially back.

It can easily be seen that the acetabular cup 2 according to the invention is not only relatively simple and inexpensive to manufacture, but that it can be implanted in a very simple manner, which clearly results in an excellent primary fixation and also an excellent long-term fixation. since the positive engagement of the anchoring lugs 14 in the tissue is retained and, moreover, cancellous bone grows into the grooves 6 .

Apart from the other advantages already described, there is a significant advantage - as stated - that even during the operation the relative positioning of the cap to the acetabular tissue can be changed effortlessly and essentially without damage that the anchoring elements in their starting position withdrawn and after correcting the positioning (if necessary after rotating the cap 1 about the central axis) into the anchoring position.

Reference list

1 (outer) cap
2 hip socket
3 bearing bodies
3 ′ inside (of 3 )
4 central axis (from 1 to 2 )
5 (outer) envelope surface (of 1 )
6 grooves
7 through openings (of 1 ; for 8 )
8 anchoring element (in 7 )
8 ′ inner end face (of 8 )
9 rand (of 1 )
10 faces (of 8 )
11 pin (= swivel axis of 8 )
12 recess (groove) (of 1 )
13 ring
14 anchoring approach (of 8 )
15 tooth heads (of 14 )
16 (lower) edge (from 14 )
17 (inner) envelope surface (of 1 )
18 match (of 8 )
18 ′ hole (in 18 )
19 threaded hole (of 1 )
20 threaded pins
20 ′ slot (out of 20 )
21 sealing plug
22 tools
22 ′ head (of 22 )
23 internal threads (of 22 )
24 outer surface (from 22 ′ )
25 rand (from 22 ′ )

Claims (26)

1. acetabular cup for an endoprosthesis, with a rotati onssymmetrische outer envelope surface, schalenformi gene cap, in the interior of which the femoral head of the endoprosthesis is to be stored, characterized in that the cap ( 1 ) has at least two through openings ( 7 ) in which An anchoring element ( 8 ), which is provided on its outer end face with at least one anchoring projection ( 14 ), is held in such a way that it emerges from an initial position ( FIG. 1) in which the anchoring projection ( 14 ) is located within the outer envelope surface ( 5 ) Cap ( 1 ) is in an anchoring position ( Fig. 2) to move, in which the anchoring approach ( 14 ) protrudes laterally over the outer envelope surface ( 5 ) of the cap ( 1 ). 2. acetabular cup according to claim 1, characterized in that the anchoring elements ( 8 ) substantially fill the passage opening ( 7 ) assigned to them in the anchoring position ( Fig. 2). 3. acetabular cup according to claim 1 or 2, characterized in that the anchoring elements ( 8 ) in the anchoring position ( Fig. 2) affect the inner envelope surface ( 17 ) of the cap ( 1 ) with its inner end face ( 8 '). 4. acetabular cup according to one or more of the preceding claims, characterized in that the Durchgangsöffnun gene ( 7 ) substantially radially to the central axis ( 4 ) of the cap ( 1 ). 5. acetabular cup according to one or more of the preceding claims, characterized in that the Durchgangsöffnun gene ( 7 ) are arranged substantially uniformly distributed over the circumference of the cap ( 1 ). 6. acetabular cup according to one or more of the preceding claims, characterized in that five Durchgangsöffnun gene ( 7 ) are provided. 7. acetabular cup according to one or more of the preceding claims, characterized in that the Durchgangsöffnun gene ( 7 ) are designed as slots. 8. acetabular cup according to claim 7, characterized in that the anchoring elements ( 8 ) are designed as tabs. 9. acetabular cup according to claim 8, characterized in that the anchoring elements ( 8 ) are pivotally held on the cap ( 1 ). 10. acetabular cup according to claim 9, characterized in that the anchoring elements ( 8 ) at their edge ( 9 ) of the cap ( 1 ) facing end portion to the cap ( 1 ) are deflected. 11. A hip cup as in claim 10, characterized in that the pivot axes (11) of the anchoring elements (8) (8) projecting pin are each formed by a mentes over the side surfaces (10) of the Verankerungsele, in a corresponding recess (12) of the Cap ( 1 ) is stored. 12. acetabular cup according to claim 11, characterized in that the cap ( 1 ) on the end face of its edge ( 9 ) is provided with a groove which the recesses ( 12 ) for the position tion of the pivot axes ( 11 ) of the anchoring elements ( 8 ) forms; and that the groove ( 12 ) is closed at its end facing the edge ( 9 ) of the cap ( 8 ) by a ring ( 13 ), the height (h) of which is at least smaller by the diameter of the pins ( 11 ) than the height ( H) the groove ( 12 ). 13. acetabular cup according to one or more of the preceding claims, characterized in that the anchoring approaches ze ( 14 ) are designed as teeth. 14. acetabular cup according to claim 13, characterized in that the anchoring lugs ( 14 ) in a side plan view of a side surface of an anchoring element ( 8 ) are triangular. 15. acetabular cup according to claim 13 or 14, characterized in that the tooth heads ( 15 ) of the anchoring lugs ( 14 ) each form a cutting edge. 16. acetabular cup according to one or more of claims 13 to 15, characterized in that the anchoring lugs ( 14 ) each have an edge ( 9 ) of the cap ( 1 ) facing lower flank ( 16 ) which in the anchoring position ( Fig. 2nd ) runs essentially at right angles to the central axis ( 4 ) of the cap ( 1 ). 17. acetabular cup according to one or more of the preceding claims, characterized in that the anchoring elements ( 8 ) are each provided with a plurality of anchoring approaches ( 14 ). 18. acetabular cup according to claim 17, characterized in that the anchoring lugs ( 14 ) of an anchoring element ( 8 ) are arranged one above the other. 19. acetabular cup according to one or more of the preceding claims, characterized in that the anchoring elements ( 8 ) each cut at its end facing away from the articulation end with an eyelet-shaped or hook-shaped extension ( 18 ') projecting from its inner end face ( 8 ') are provided ( Fig. 2). 20. acetabular cup according to one or more of the preceding claims, characterized in that the cap ( 1 ) is provided with a central threaded bore ( 19 ). 21. acetabular cup according to claim 20, characterized in that in the threaded bore ( 19 ) an inwardly projecting thread tap ( 20 ) is screwed in when the anchoring elements ( 8 ) are in the starting position ( Fig. 1). 22. acetabular cup according to claim 20 or 21, characterized in that a sealing plug ( 21 ) is screwed into the threaded bore ( 19 ) when the anchoring elements ( 8 ) are in the anchoring position ( Fig. 2). 23. acetabular cup according to one or more of the preceding claims, characterized in that a cup-shaped bearing body ( 3 ) is arranged in the cap ( 1 ) in a manner known per se, the dome-shaped inside ( 3 ) of which is directed towards the open side of the cap ( 1 ) ') Forms the bearing surface for the femoral head. 24. acetabular cup according to claim 23, characterized in that the bearing body ( 3 ) consists of ceramic in a manner known per se. 25. acetabular cup according to one or more of the preceding claims, characterized in that the cap ( 1 ) consists of CrCoMo steel in a manner known per se. 26. Hip socket according to one or more of the preceding claims, characterized in that the inner envelope surface ( 17 ) of the cap ( 1 ) from its edge ( 9 ) is conically tapered inwards.