DE4205018C1 - Artificial hip joint bearing shell - has bottom edge side opening to retain guiding pin, permitting alignment before inserting anchorage screws - Google Patents

Abstract

The hemispherical shell (1) includes an opening at one side in its equatorial zone, for a guiding pin (7) with a hole through its centre, for inserting a locating rod. Higher up, on the opposite side are live holes (3) so that two securing screws (5) can be inserted at selected positions. The pin and its opening are shaped to permit tilt for alignment, without the pin falling out. The pin has a countersunk head (10) and the opening has a matching seating surface. The head is followed by an undercut part which is followed by an externally threaded part (12) and the remainder is smaller in diameter, with a helical groove (18). Above the undercut and externally threaded parts is an outwardly projecting tongue (15). USE/ADVANTAGE - Artificial hip joint bearing shell. Good alignment is ensured before the shell is secured.

Description

The present invention relates to an acetabular cup for an artificial hip joint.

Such implants are numerous Executions become known. Be here for example on the following publications noted: CH 6 68 180 A5, FR 85 03 713 A1, DE 36 20 460 C1, DE 32 05 527 C2, CH 6 63 893 A5, EP 02 11 169 A1, DE 83 35 354 U1, DE 72 40 856 U1 and finally DE 90 16 523 U1. In some of these Publications, but especially in the the latter is already the problem of correct Positioning the socket in the Pelvic bone socket discussed. Before that Bone screws that form the calotte of the acetabular cup enforce, be screwed into the bone, the socket must be positioned exactly because otherwise in the event of incorrect alignment Bone screws out of the pelvic bone again have to be unscrewed afterwards exact alignment of the socket under certain circumstances have to be turned in the bones in places that are adjacent to those previously brought in and now unusable threads in which previously the Bone screws have been inserted. this has serious disadvantages for the stability of the Anchoring the socket in the anyway damaged bones.  

According to DE 90 16 523 U1 is therefore provided been the calotte in the equatorial area penetrating hole for the introduction of a Threading aid through a concentric around this formed segment of a cylindrical tube border, so that after a first driving in Joint socket into the pelvic bone socket a Fine positioning is possible.

In practice it has now been shown that this type the fine positioning offers advantages compared to previously known approaches. The Manageability is still limited in that the threading aid, the more usual Way from one in the equatorial area provided hole in one in the pubic bone introduced bore engages, is rigid, so that the fine positioning of the socket after Driving into the pelvic bone socket is possible but through the rough positioning when driving in Areas is restricted.

Joint pans with at least one each are pivotable fixation element became known from the publications DE-91 10 508 U1, CH-6 71 509 A5, CH-6 74 927 A5, US-49 36 861, EP-03 80 045. The pivotable Fixation elements, partly designed as pivotable bone screws, facilitate the Implantation of the socket. As a disadvantage with these known joint pans, however out that the pivotable fixation element can easily fall out of the hole in the calotte. The reintroduction of the element during the most fairly confusing situation during the Operation is quite cumbersome.

Against this background, it is now the task of present invention to provide an acetabular cup the after the first introduction into the Pelvic bone socket easy to position can be aligned by a swiveling Fixation element before moving into the Pelvic bone socket is hammered in and the Bone screws through the calotte in the Pelvic bones are screwed in, the pivotable fixation element against one Fall out should be secured.

This problem is solved by the joint socket the features of claim 1.

Accordingly, intervenes in the equatorial area provided bore a freely around its longitudinal axis in pivotable in all directions by up to 10 ° Lead splint. Before inserting the pan into the Pelvic bone socket becomes a hole in the pubic bone or in the ischium or in the connecting leg Bone lamella attached, in which said Lead splint is to be set. The split pin can also be clamped behind this bone lamella will. Whose free pivotability allows it to align the pan more precisely, even when the split pin in the hole in the bone is set or clamped behind the bone lamella is. Opposite rigid spigot joint socket according to the invention more degrees of freedom for positioning on.

After finding the correct position, the Joint socket then in a press fit in the Pelvic bone pan beaten and by means of at least two bone screws in the pelvic bone  fixed, so that a stable three-point Fixation results.

The pivot pin of the guide pin can can be advantageously realized in that the Hole in the equatorial area facing the inside of the Dome towards conically widening contact surfaces and the split pin has a head with it accordingly has tapered contact surfaces. Alternatively for this purpose it can be provided that the bore after a cylindrical section to the inside of the Dome expanded towards hemispherical, so is trough-shaped, and the split pin has a head correspondingly is hemispherical.

To protect against falling out ensure the cotter pin is in its place pivotable storage against falling out secured by the fact that the hole in the equatorial Area of the socket with an internal thread and the split pin partially with one corresponding external thread is provided, wherein between the head and the external thread unthreaded section is provided, the wider is the bore with the internal thread. The split pin is therefore once in the hole set and rotated until be External thread section from the internal thread of the Hole emerges. After that the Guide split pin the hole only with his unthreaded section between its external thread and his head. This is again the Swiveling of the pin is guaranteed.

According to a further advantageous embodiment the cotter pin shows one through him in his  Continuous threading channel in the longitudinal direction. This enables the rough positioning of the Pan is facilitated by the fact that a long Threading aid, for example in the form of a strong wire, through the pin first can be placed in the hole in the bone and the pan to the Pelvic bone socket can be guided and the Guide pin is placed in the hole in the bone can be.

In addition, the joint socket can be used on the other Seen from the equatorial plane behind the split pin parallel to the equatorial plane extending locking element in the form of a tab-shaped approach can be provided that similar as in the case of DE 90 16 523 U1 as a segment arranged concentrically around the bore a cylindrical tube can be formed. This approach offers an additional one  Locking option given at the same time Possibility of fine positioning.

The distal end of the guide splint points advantageously an enlarged surface that is realized for example by a spiral groove. This will reduce the friction between the Pelvic bone in the area of the bone hole and the Guide cotter pin increased so that this after Insert a first stop in the bone hole offers the exact alignment of the socket. The prerequisite for this is that the The diameter of the bone hole is approximately that Diameter of the guide pin corresponds.

The invention is based on an embodiment explained in more detail according to the drawing figures. Here shows:

Fig. 1 is a plan view of the implantation finished pan according to the invention,

Fig. 2 is a sectional view taken along line II-II in Fig. 1,

Fig. 3 is a view of an embodiment for the split pin, and

Fig. 4 is a sectional view of the Führungssplints of FIG. 3.

Below are the same parts with the same Provide reference numerals.

Fig. 1 shows a plan view of the socket 1 according to the invention, as seen in the direction of the pole P of the calotte. A circular recess 17 is provided around the pole P in a well-known manner, which allows the surgeon to feel the wall of the pelvic bone socket. In the exemplary embodiment shown, the joint socket 1 is provided with a structured open-mesh surface 16 , as can be produced, for example, according to DE 41 06 971 C1 and is used for secondary fixation of the joint socket in the bony bed by ingrowth of bone material.

The calotte is interspersed with a number of openings for bone screws 5 , two of which are provided with reference numerals 3 and 4 , respectively.

In the equatorial area, a bore 2 passes through the wall of the socket 1 , as can be clearly seen from FIG. 2. This bore 2 has a cylindrical section 13 , which is followed by a widening towards the interior of the calotte, in the form of conically widening contact surfaces 8 . In the cylindrical section 13 , the bore 2 is provided with an internal thread 11 . Through the bore 2 , the guide split pin 7 engages with a head 10 facing the interior of the calotte, which has conically tapering contact surfaces 9 which lie against the contact surfaces 8 of the bore 2 . In the area of the cylindrical section 13 of the bore 2 , the guide split pin 7 is also cylindrical with a smaller diameter. This allows the split pin 7 to be pivoted about the longitudinal axis 6 of the bore 2 in all directions, namely by up to 10 °. The cylindrical part of the guide pin 7 is connected to the outside by an external thread 12 , which is distally joined by a section with a spiral annular groove 18 .

The counterpart to the external thread 12 is found in the cylindrical part 13 of the bore 2 , specifically in the internal thread 11 .

The splint 7 is assembled in the following way:

The guide split pin is guided from the inside of the calotte to the bore 2 until the external thread 12 of the guide split pin 7 comes into engagement with the internal thread 11 of the bore 2 . The guide pin is then rotated further in the manner of a screw until the external thread 12 finally disengages from the internal thread 11 . Then the cylindrical section of the guide splint 7 comes to rest in the cylindrical section 13 of the bore 2 . This type of securing the guide pin 7 against unintentional falling out. The free pivotability of the guide pin 7 in the bore 2 assumes that the cylindrical portion 19 of the guide pin 7 is wider than the bore 2 provided with the internal thread 11 .

From Figs. 1 and 2 still a tab-shaped projection 15 can be seen on the socket 1, which is preferably designed as a segment of a cylindrical tube and is used for fine positioning of the acetabulum in the pelvic bone socket.

The guide pin 7 itself is shown separately in FIGS. 3 and 4. Clearly recognizable from this is again in FIG. 3, the head 10 having the tapered contact surfaces 9, the cylindrical portion 19, the portion with the external thread 12 and the distal portion with the annular groove 18, which causes an increase in surface area in this range, leading to a interlocking with the bone material around the bone hole.

In the embodiment according to Fig. 4 of the Führungssplint 7 is provided with a Einfädelungskanal 14, which passes through the split pin 7 in its longitudinal direction. This allows the introduction of an almost wire-shaped threading aid, so that the joint socket according to the invention can be fed to the implantation site in a simple manner by placing the wire on the bottom of the bone hole and guiding the socket down on the wire until the guide splint 7 in the bone hole comes to rest.

Claims (7)

1. In a pelvic bone socket fixable hemispherical socket ( 1 ) for an artificial hip joint with a hole penetrating its wall in the equatorial area ( 2 ) and at least two penetrations ( 3 , 4 ) for bone screws ( 5 ) in their calotte, in which through the hole (2) a freely engages about its longitudinal axis (6) in all directions in order to be swiveled to 10 ° Führungssplint (7), wherein the Führungssplint (7) is secured in its pivotable mounting against falling out in that the bore (2) with an internal thread ( 11 ) and the split pin ( 7 ) is partially provided with a corresponding external thread ( 12 ), and between the head ( 10 ) and the external thread ( 12 ) a thread-free section is provided which is wider than that with the internal thread ( 11 ) provided bore ( 2 ). 2. joint socket according to claim 1, wherein the bore ( 2 ) to the interior of the dome conically widening contact surfaces ( 8 ) for conically tapering contact surfaces ( 9 ) of the head ( 10 ) provided with split pins ( 7 ). 3. joint socket according to claim 1, wherein the bore ( 2 ) after a cylindrical section ( 13 ) towards the interior of the spherical cap extends and the head ( 10 ) of the guide pin ( 7 ) is formed accordingly hemispherical. 4. joint socket according to one of claims 1 to 3, wherein the guide split pin ( 7 ) has a continuous threading channel ( 14 ) in the longitudinal direction. 5. joint socket according to one of claims 1 to 4, in which seen on the outside from the equatorial plane behind the guide split pin ( 7 ) a parallel to the equatorial locking element in the form of a tab-shaped extension ( 15 ) is provided. 6. joint socket according to one of claims 1 to 5, wherein the distal part ( 18 ) of the guide splint ( 7 ) has an enlarged surface. 7. socket according to claim 6, wherein the distal part ( 18 ) of the guide pin ( 7 ) is spiral grooved.