CH649913A5

CH649913A5 - Cementlessly anchorable joint socket

Info

Publication number: CH649913A5
Application number: CH186981A
Authority: CH
Inventors: Adam Prof Dr Med Schreiber; Hilaire Jacob
Original assignee: Sulzer Ag
Priority date: 1981-03-19
Filing date: 1981-03-19
Publication date: 1985-06-28

Abstract

In order to avoid cutting a screw thread into the pelvic bone, which has hitherto been necessary, the outer surface of the outer shape, formed as a truncated cone (1), of the socket is provided with depressions (5) which are interrupted by webs (6) in the circumferential direction. In this way, transverse ribs (7) are formed between the depressions (5), and these deform on insertion of the socket into the bone and ensure secure primary fixation by a barb-like anchorage in the artificially produced socket bearing of the bone until the cementlessly anchored socket is retained by tissue growing in or on. <IMAGE>

Description

       

  
 

**WARNUNG** Anfang DESC Feld konnte Ende CLMS uberlappen **.

 



   PATENTANSPRÜCHE
1. Im Becken zementfrei verankerbare Gelenkpfanne zur Aufnahme des Gelenkkopfes einer Hüftgelenkprothese, wobei die Aussenform der Pfanne einen rotationssymmetrisehen Kegelstumpf bildet, dadurch gekennzeichnet, dass im Mantel des Kegelstumpfes (1) durch Stege (6) unterbrochene, zirkulare Vertiefungen (5) vorhanden sind, zwischen denen in Umfangsrichtung verlaufende Querrippen (7) verbleiben, wobei die Tiefe (t) der Vertiefungen und ihr Abstand (a) in Abhängigkeit vom Material der Gelenkpfanne so gewählt sind, dass sich die Querrippen (7) beim Einsetzen in den Knochen verformen.



   2. Gelenkpfanne nach Anspruch 1, dadurch gekennzeichnet, dass das weite Ende (3) des Kegelstumpfes (1) durch einen als Anschlag wirkenden Rand abgeschlossen ist.



   3. Gelenkpfanne nach Anspruch 1 aus Polyäthylen der Klassifikationen HDPE oder UHMW, dadurch gekennzeichnet, dass die Tiefe (t) der Vertiefungen 1-4 mm und ihr Abstand (a) von Sohle zu Sohle 2-5 mm betragen.



   Die Erfindung betrifft eine im Becken zementfrei verankerbare Gelenkpfanne zur Aufnahme des Gelenkkopfes einer Hüftgelenkprothese, wobei die Aussenform der Pfanne einen rotationssymmetrischen Kegelstumpf bildet.



   Für eine zementfreie Verankerung sind künstliche Gelenkpfannen für Totalprothesen des Hüftgelenkes der vorstehend genannten Art bekannt (CH-PS 568 735); die Form des Kegelstumpfes ist dabei gewählt worden, weil sich gezeigt hat, dass die ebenfalls bekannten   haibkugelsehalenför-    magen Pfannen, besonders bei der angestrebten zementfreien Verankerung, durch elastische Verformungen infolge der wechselnden Be- und Entlastungen des Beckenknochens relativ leicht aus ihrer Verankerung herausgedrückt werden.



  Zur Fixierung im Beckenknochen ist in den Mantel des Kegelstumpfes bei den bekannten Pfannen ein Gewinde eingeschnitten, mit dem die Pfanne in ein entsprechendes Gewinde in das künstlich geschaffene Pfannenlager des Beckenknochens eingeschraubt wird.



   Die Fixierung dieser bekannten Pfanne mit Hilfe eines Gewindes hat sich in der Praxis als nachteilig erwiesen, da das Schneiden eines Gewindes mit der für eine zementfreie Fixierung erforderlichen Genauigkeit in das operativ geschaffene kegelstumpfförmige Pfannenlager im Beckenkno   ehen    erhebliche Schwierigkeiten bereitet.



   Aufgabe der Erfindung ist es daher, eine Gelenkpfanne für eine zementfreie Verankerung zu schaffen, bei deren Implantation das Schneiden eines Gewindes in den Beckenknochen entfällt.



   Erfindungsgemäss wird diese Aufgabe dadurch gelöst, dass im Mantel des Kegelstumpfes durch Stege unterbrochene, zirkulare Vertiefungen vorhanden sind, zwischen denen in Umfangsrichtung verlaufende Querrippen verbleiben, wobei die Tiefe der Vertiefungen und ihr Abstand in Abhängigkeit vom Material der Gelenkpfanne so gewählt sind, dass sich die Querrippen beim Einsetzen in den Knochen verformen.



   Für die Fixierung dieser neuen Pfanne muss im Knochen lediglich das passgenaue Pfannenlager ohne Gewinde, beispielsweise durch Fräsen, hergestellt werden. In dieses wird dann die Pfanne in Richtung ihrer Achse einfach eingepresst oder leicht eingeschlagen, wobei sich die Querrippen entgegen der Einschlagrichtung umbiegen und widerhakenartig in der Wand des Pfannenlagers  einhaken . Auf diese Weise wird die sogenannte primäre Fixierung gewährleistet, durch die die Pfanne gehalten werden muss, bis an sie Gewebe anbzw. in ihre Vertiefungen eingewachsen ist; die Stege in Umfangsrichtung zwischen den einzelnen Vertiefungen übernehmen dabei die Aufgabe einer Verdrehsicherung.



   Um ein zu tiefes Einpressen bzw. Eindringen der Pfanne in den Knochen zu verhindern, kann es zweckmässig sein, wenn das weite Ende des Kegelstumpfes durch einen als Anschlag wirkenden Rand abgeschlossen ist.



   Bei der Dimensionierung einer Pfanne aus Polyäthylen hat es sich als vorteilhaft erwiesen, wenn die Tiefe der Vertiefungen 1-4 mm und ihr Abstand von Sohle zu Sohle 2-5 mm betragen; obwohl körperverträgliche und -beständige Kunststoffe die bevorzugten Werkstoffe für die neue Pfanne sind, kann diese auch aus einem in der Implantattechnik üblichen Metall oder einer Metall-Legierung gefertigt werden.



   Im folgenden wird die Erfindung anhand von Ausführungsbeispielen im Zusammenhang mit der Zeichnung näher erläutert.



   Fig. list eine Seitenansicht einer ersten Ausführungsform;
Fig. 2 ist eine Aufsicht in Richtung der Achse des die Aussenform bildenden Kegels auf ein zweites Ausführungsbeispiel;
Fig. 3 schliesslich ist der Schnitt   111-111    von Fig. 2.



   Die Aussenform der Gelenkpfanne ist ein rotationssymmetrischer Kegelstumpf 1 (Fig. 1), dessen Symmetrieachse mit 2 bezeichnet ist. Koaxial zum Mantel der Aussenform angeordnet ist vom weiten Ende 3 her ein   haibkugelförmiger    Hohlraum 4 (Fig. 3) als   Pfannensehale    für die Aufnahme des Gelenkkopfes einer nicht dargestellten Femurprothese aus dem Pfannenkörper herausgearbeitet.



   Erfindungsgemäss sind in die Mantelfläche des Kegelstumpfes 1 Vertiefungen 5 eingearbeitet, zwischen denen entlang einer Mantellinie verlaufende Stege 6 vorhanden sind; diese dienen, wie erwähnt, als Verdrehsicherung.



   Zwischen den parallel zueinander in Umfangsrichtung verlaufenden Vertiefungen 6 verbleiben Querrippen 7; deren Höhe und Abstand sind materialabhängig so gewählt, dass sich mindestens ein Teil von ihnen beim Einpressen der Pfanne in den vorbereiteten Beckenknochen elastisch verformt und somit die primäre Fixierung fördernden, widerhakenartigen Verankerungen an der Knochenwand bilden.



   Die in Fig. 2 und 3 gezeigte zweite Ausführungsform der neuen Gelenkpfanne unterscheidet sich von derjenigen nach Fig. 1 nur dadurch, dass sie am weiten Ende 3 einen über die Mantelfläche des Kegelstumpfes 1 vorstehenden Rand 8 hat, der als Anschlag beim Einsetzen der Pfanne in den Knochen dient.



   Bei den gezeigten Beispielen, denen je eine Ausführungsform der Pfannen aus Polyäthylen zugrundeliegen, beträgt die Tiefe t der Vertiefungen 5 beispielsweise 2 mm, während ihr Abstand a, gemessen von Sohle zu Sohle, 3 mm ist.



   Für die Implantation der neuen Pfanne hat sich beispielsweise als zweckmässig erwiesen, im Knochen eine in Form und Abmessungen an den Kegelstumpf 1 passgenau angepasste Ausnehmung zu schaffen, die gegebenenfalls sogar ein wenig enger als die Aussenform der Pfanne sein kann; anschliessend wird die Pfanne in diese Ausnehmung mit einem gewissen Druck eingepresst. Da ihre   Form -    und auch diejenige der eigentlichen Pfannenschale   4-    vollkommen rotationssymmetrisch sind, kann die Pfanne bei der Implantation um ihre Achse beliebig gedreht und ohne Beachtung einer bestimmten Lage, beispielsweise einer markierten Stelle des Randes der Pfanne relativ zu einem Bezugspunkt am   Beckenknochen,    eingesetzt werden, was ein weiterer Vorteil der neuen Konstruktion ist.  



   Die erfindungsgemässe Ausbildung der Mantelfläche des



  Kegelstumpfes 1 gewährleistet eine sichere Primär-Fixierung der Pfanne im Knochen, während ihre Kegelstumpfform gleichzeitig eine   grossfläehige    Abstützung im Knochen er   möglichst,    die den elastischen Verformungen des Beckens bei Be- und Entlastungen in gewissem Umfang nachkommen kann. 



  
 

** WARNING ** beginning of DESC field could overlap end of CLMS **.

 



   PATENT CLAIMS
1. An acetabular socket that can be anchored in the pelvis without cement for receiving the joint head of a hip prosthesis, the outer shape of the socket forming a rotationally symmetrical truncated cone, characterized in that circular recesses (5) interrupted by webs (6) are present in the jacket of the truncated cone (1), remain between which in the circumferential direction transverse ribs (7), the depth (t) of the recesses and their spacing (a) are selected depending on the material of the socket, so that the transverse ribs (7) deform when inserted into the bone.



   2. joint socket according to claim 1, characterized in that the wide end (3) of the truncated cone (1) is closed by an edge acting as a stop.



   3. joint socket according to claim 1 made of polyethylene of the classifications HDPE or UHMW, characterized in that the depth (t) of the depressions 1-4 mm and their distance (a) from sole to sole 2-5 mm.



   The invention relates to a joint socket that can be anchored in the pelvis without cement for receiving the joint head of a hip joint prosthesis, the outer shape of the socket forming a rotationally symmetrical truncated cone.



   For a cement-free anchoring, artificial joint sockets for total hip prostheses of the aforementioned type are known (CH-PS 568 735); the shape of the truncated cone was chosen because it has been shown that the well-known hemispherical cups, particularly in the case of the cement-free anchoring sought, are relatively easily pushed out of their anchoring by elastic deformations due to the changing loading and unloading of the pelvic bone.



  For fixation in the pelvic bone, a thread is cut into the surface of the truncated cone in the known pans, with which the pan is screwed into a corresponding thread in the artificially created pan bearing of the pelvic bone.



   The fixation of this known pan with the aid of a thread has proven disadvantageous in practice, since the cutting of a thread with the accuracy required for cement-free fixation into the surgically created frustoconical socket bearing in the pelvic bone causes considerable difficulties.



   The object of the invention is therefore to create a joint socket for cementless anchoring, the implantation of which eliminates the cutting of a thread in the pelvic bone.



   According to the invention, this object is achieved in that there are circular recesses interrupted by webs in the jacket of the truncated cone, between which there remain transverse ribs running in the circumferential direction, the depth of the recesses and their spacing being chosen depending on the material of the joint socket so that the Deform the transverse ribs when inserting them into the bone.



   To fix this new socket, all that is required is to make the precisely fitting socket bearing without thread, for example by milling, in the bone. The pan is then simply pressed or slightly hammered into this in the direction of its axis, the transverse ribs bending against the direction of impact and hooking into the wall of the pan bearing like a barb. In this way, the so-called primary fixation is ensured, by which the pan must be held until tissue is attached to it. has grown into their recesses; the webs in the circumferential direction between the individual depressions take on the task of securing against rotation.



   In order to prevent the pan from being pressed or penetrated too deeply into the bone, it can be expedient if the wide end of the truncated cone is closed off by an edge which acts as a stop.



   When dimensioning a pan made of polyethylene, it has proven to be advantageous if the depth of the depressions is 1-4 mm and their distance from the sole to the sole is 2-5 mm; Although body-compatible and resistant plastics are the preferred materials for the new cup, it can also be made from a metal or a metal alloy that is common in implant technology.



   The invention is explained in more detail below on the basis of exemplary embodiments in conjunction with the drawing.



   Fig. List is a side view of a first embodiment;
Fig. 2 is a plan view in the direction of the axis of the cone forming the outer shape of a second embodiment;
3 is finally the section 111-111 of FIG. 2.



   The outer shape of the socket is a rotationally symmetrical truncated cone 1 (FIG. 1), the axis of symmetry of which is designated by 2. Arranged coaxially to the jacket of the outer shape, a hemispherical cavity 4 (FIG. 3) is machined from the wide end 3 as a socket shell for receiving the joint head of a femoral prosthesis, not shown, from the socket body.



   According to the invention 1 recesses 5 are incorporated into the lateral surface of the truncated cone, between which there are webs 6 running along a surface line; as mentioned, these serve as anti-rotation devices.



   Cross ribs 7 remain between the depressions 6 running parallel to one another in the circumferential direction; their height and spacing are selected depending on the material so that at least some of them deform elastically when the socket is pressed into the prepared pelvic bones, thus forming barb-like anchors on the bone wall that promote primary fixation.



   The second embodiment of the new joint socket shown in FIGS. 2 and 3 differs from that according to FIG. 1 only in that it has at the wide end 3 an edge 8 projecting beyond the lateral surface of the truncated cone 1, which acts as a stop when the socket is inserted in serves the bones.



   In the examples shown, which are based on an embodiment of the pans made of polyethylene, the depth t of the depressions 5 is, for example, 2 mm, while their distance a, measured from sole to sole, is 3 mm.



   For the implantation of the new cup, it has proven to be expedient, for example, to create a recess in the bone that is precisely matched in shape and dimensions to the truncated cone 1, which may even be a little narrower than the external shape of the cup; the pan is then pressed into this recess with a certain pressure. Since their shape - and also that of the actual socket shell 4 - are completely rotationally symmetrical, the socket can be rotated around its axis during implantation and used without regard to a specific position, for example a marked position on the edge of the socket relative to a reference point on the pelvic bone what is another advantage of the new design.



   The inventive design of the lateral surface of the



  Truncated cone 1 ensures a secure primary fixation of the socket in the bone, while its truncated cone shape at the same time provides extensive support in the bone, which can to a certain extent meet the elastic deformations of the pelvis during loading and unloading.

Claims

PATENT CLAIMS 1. An acetabular socket that can be anchored in the pelvis without cement for receiving the joint head of a hip prosthesis, the outer shape of the socket forming a rotationally symmetrical truncated cone, characterized in that circular recesses (5) interrupted by webs (6) are present in the jacket of the truncated cone (1), remain between which in the circumferential direction transverse ribs (7), the depth (t) of the recesses and their spacing (a) are selected depending on the material of the socket, so that the transverse ribs (7) deform when inserted into the bone.

2. joint socket according to claim 1, characterized in that the wide end (3) of the truncated cone (1) is closed by an edge acting as a stop.

3. joint socket according to claim 1 made of polyethylene of the classifications HDPE or UHMW, characterized in that the depth (t) of the depressions 1-4 mm and their distance (a) from sole to sole 2-5 mm.

The invention relates to a joint socket that can be anchored in the pelvis without cement for receiving the joint head of a hip joint prosthesis, the outer shape of the socket forming a rotationally symmetrical truncated cone.

For a cement-free anchoring, artificial joint sockets for total hip prostheses of the aforementioned type are known (CH-PS 568 735); the shape of the truncated cone was chosen because it has been shown that the well-known hemispherical cups, particularly in the case of the cement-free anchoring sought, are relatively easily pushed out of their anchoring by elastic deformations due to the changing loading and unloading of the pelvic bone.

For fixation in the pelvic bone, a thread is cut into the surface of the truncated cone in the known pans, with which the pan is screwed into a corresponding thread in the artificially created pan bearing of the pelvic bone.

The fixation of this known pan with the aid of a thread has proven disadvantageous in practice, since the cutting of a thread with the accuracy required for cement-free fixation into the surgically created frustoconical socket bearing in the pelvic bone causes considerable difficulties.

The object of the invention is therefore to create a joint socket for cementless anchoring, the implantation of which eliminates the cutting of a thread in the pelvic bone.

According to the invention, this object is achieved in that there are circular recesses interrupted by webs in the jacket of the truncated cone, between which there remain transverse ribs running in the circumferential direction, the depth of the recesses and their spacing being chosen depending on the material of the joint socket so that the Deform the transverse ribs when inserting them into the bone.

To fix this new socket, all that is required is to make the precisely fitting socket bearing without thread, for example by milling, in the bone. The pan is then simply pressed or slightly hammered into this in the direction of its axis, the transverse ribs bending against the direction of impact and hooking into the wall of the pan bearing like a barb. In this way, the so-called primary fixation is ensured, by which the pan must be held until tissue is attached to it. has grown into their recesses; the webs in the circumferential direction between the individual depressions take on the task of securing against rotation.

In order to prevent the pan from being pressed or penetrated too deeply into the bone, it can be expedient if the wide end of the truncated cone is closed off by an edge which acts as a stop.

When dimensioning a pan made of polyethylene, it has proven to be advantageous if the depth of the depressions is 1-4 mm and their distance from the sole to the sole is 2-5 mm; Although body-compatible and resistant plastics are the preferred materials for the new cup, it can also be made from a metal or a metal alloy that is common in implant technology.

The invention is explained in more detail below on the basis of exemplary embodiments in conjunction with the drawing.

Fig. List is a side view of a first embodiment; Fig. 2 is a plan view in the direction of the axis of the cone forming the outer shape of a second embodiment; 3 is finally the section 111-111 of FIG. 2.

The outer shape of the socket is a rotationally symmetrical truncated cone 1 (FIG. 1), the axis of symmetry of which is designated by 2. Arranged coaxially to the jacket of the outer shape, a hemispherical cavity 4 (FIG. 3) is machined from the wide end 3 as a socket shell for receiving the joint head of a femoral prosthesis, not shown, from the socket body.

According to the invention 1 recesses 5 are incorporated into the lateral surface of the truncated cone, between which there are webs 6 running along a surface line; as mentioned, these serve as anti-rotation devices.

Cross ribs 7 remain between the depressions 6 running parallel to one another in the circumferential direction; their height and spacing are selected depending on the material so that at least some of them deform elastically when the socket is pressed into the prepared pelvic bones, thus forming barb-like anchors on the bone wall that promote primary fixation.

The second embodiment of the new joint socket shown in FIGS. 2 and 3 differs from that according to FIG. 1 only in that it has at the wide end 3 an edge 8 projecting beyond the lateral surface of the truncated cone 1, which acts as a stop when the socket is inserted in serves the bones.

In the examples shown, which are based on an embodiment of the pans made of polyethylene, the depth t of the depressions 5 is, for example, 2 mm, while their distance a, measured from sole to sole, is 3 mm.

For the implantation of the new cup, it has proven to be expedient, for example, to create a recess in the bone that is precisely matched in shape and dimensions to the truncated cone 1, which may even be a little narrower than the external shape of the cup; the pan is then pressed into this recess with a certain pressure. Since their shape - and also that of the actual socket shell 4 - are completely rotationally symmetrical, the socket can be rotated around its axis during implantation and used without regard to a specific position, for example a marked position on the edge of the socket relative to a reference point on the pelvic bone what is another advantage of the new design. ** WARNING ** End of CLMS field could overlap beginning of DESC **.