DE10000521A1 - Ceramic sandwich insert for an artificial hip joint - Google Patents

Abstract

The invention relates to a sandwich insert with an inner sliding shell (1) made of ceramic, which is enclosed by a plastic jacket (2), for insertion into an outer metal shell of an artificial hip joint. DOLLAR A In order to increase the turnover strength with a small space requirement, it is proposed that the sliding shell (1) have a pin (3) at its outer end facing away from the opening.

Description

The invention relates to a sandwich insert with an inner sliding shell made of Ke ramic, which is enclosed by a plastic jacket, for insertion in a outer metal shell of an artificial hip joint.

An artificial hip joint usually consists of a sliding cup that is directly attached or via a plastic jacket in an outer. Metal shell is inserted. This metal shell is implanted in the pelvic bones. The combination Sliding shell with a plastic jacket is called a sandwich insert.

A shaft is implanted in the femur on which a ball head is placed is arranged, which articulates in the sliding shell.

Again and again it can hit the ball with artificial hip joints head shaft come to the acetabular cup. The impact forces are great enough, this can dissolve the mechanical acetabular cup of lead. Sandwich pan systems in particular are at risk here because the predominantly used PE (polyethylene) only an insufficient Wi who can stand up to these impact forces.

Sandwich inserts are made in a number of ways.

In one system, the ceramic sliding shell or insert is made of plastic overmolded, with recesses being arranged on the sliding shell. Disadvantageous this is due to the poorer polyethylene (PE) properties caused by the Heating of the same result. There is also a thermal shock for the ke ram sliding cup. In addition to the extrusion costs due to the injection mold and The handling of the hot parts is disadvantageous because of the large space requirement.  

In an alternative system, the sliding shell is a conical clamp anchored in the plastic jacket, with sometimes low strength of the Composite component. The large space requirement is also disadvantageous here.

Warm pressing of the sliding shell into the plastic is also preferred coat used. Here, however, the strength of the Composite component. There are also tight tolerances due to the press connection note.

The invention has for its object a sandwich insert according to the waiter Concept of claim 1 to improve so that a high level of turnover small space requirement is achieved.

According to the invention, this object is achieved in that the sliding shell has a pin at its outer end facing away from the opening, whereby the turnover strength is significantly increased with a small space requirement, since the Spigot requires almost no additional space.

The pin is advantageously on the central axis or the axis of rotation arranged the sliding shell and has an axial length of 1-8 mm, preferably from approx. 2 mm. This length is sufficient to increase the turnover strength chatting. However, other lengths can also be used.

In a preferred embodiment, the pin is in art by means of a fit arranged fabric jacket. This can be an oversize fit, transition fit or a tight fit, depending on the desired resistance confi guration.  

The pin can completely protrude through the plastic jacket, into it gene or at least partially enclosed by the plastic jacket. Be preferably it is also completely enclosed by the plastic jacket.

The cross section of the pin forms an N-flat with N = 2, 4, 5 or 6. Alternatively the cross section of the pin can also form a polygon or be oval.

The sliding shell preferably has a spherical or an outer surface graded design. Spherical designs have a very small construction space requirements.

In an advantageous embodiment, the plastic sheath clasps the slide le at its open end.

The sandwich insert is preferably produced by pressing in the slide le in the plastic jacket.

Further features of the invention result from the figures that follow are described. It shows:

Fig. 1 shows an inventive insert in sandwich spherical design,

Fig. 2 shows a sandwich insert according to the invention in a graduated design and

Fig. 3 advantageous embodiments of the cross sections of the pin.

Fig. 1 shows a sandwich insert with a sliding shell 1 in a spherical design. During manufacture, this sliding shell 1 is pressed into the plastic jacket 2 . The plastic jacket 2 is preferably made of polyethylene (PE). The upper edge of the sliding shell is flush with the upper edge of the plastic jacket 2 leads. To increase the strength, ie also for better anchoring tion of the sliding shell 1 in the plastic jacket 2 , a pin 3 is arranged on the end of the sliding opening th end of the sliding shell on the axis of rotation or central axis 4 . This pin 3 protrudes into the plastic jacket 2 in this embodiment.

Fig. 2 shows an alternative embodiment having a stepped design of the sliding cup 1 on its outer side. Here, too, a pin 3 is arranged on the central axis 4 , which is completely enclosed here by the plastic jacket 2 . The axial length of the pin 3 is approximately 2 mm.

Since the sliding shell 1 is pressed into the plastic sheath 2 in the preparation, the pin 3 is inserted by means of a fit in the plastic jacket. 2

At its open end, the plastic jacket 2 clasps the slide shell 1 , which improves the fastening. The collar 5 of the plastic jacket 2 resting on the top of the sliding shell 1 covers almost half of the upper edge.

Fig. 3 shows cross-sections of the various embodiments of the peg 3. It is a cross section of the pin 3 perpendicular to the central axis 4 ge shows.

Fig. 3a shows an oval cross-section to increase the rotational strength, Fig. 3b a double and Fig. 3c a polygonal cross-section. This has the advantage of being able to be rotated with relatively high plastic displacement.

FIG. 3d shows a 4-flat or a square spigot 3 and FIG. 3e a 5-flat as spigot 3 . Another advantage is a 6-flat as a cross-section of the pin.

Claims (12)

1. Sandwich insert with an inner sliding shell ( 1 ) made of ceramic, which is enclosed by a plastic jacket ( 2 ), for insertion into an outer metal shell of an artificial hip joint, characterized in that the sliding shell ( 1 ) faces away from the opening outer end has a pin ( 3 ). 2. Sandwich insert according to claim 1, characterized in that the pin ( 3 ) on the central axis ( 4 ) of the sliding shell ( 1 ) is arranged. 3. Sandwich insert according to claim 1 or 2, characterized in that the pin ( 3 ) has an axial length of 1-8 mm, preferably of about 2 mm. 4. Sandwich insert according to one of claims 1 to 3, characterized in that the pin ( 3 ) is arranged by means of a fit in the plastic jacket ( 2 ). 5. Sandwich insert according to one of claims 1 to 4, characterized in that the pin ( 3 ) protrudes into the plastic jacket ( 2 ) or extends completely through it. 6. Sandwich insert according to one of claims 1 to 4, characterized in that the pin ( 3 ) is at least partially closed by the plastic jacket ( 2 ). 7. Sandwich insert according to one of claims 1 to 6, characterized in that the cross section of the pin ( 3 ) forms an N-flat with preferably N = 2, 4, 5 or 6. 8. Sandwich insert according to one of claims 1 to 6, characterized in that the cross section of the pin ( 3 ) forms a polygon. 9. Sandwich insert according to one of claims 1 to 6, characterized in that the cross section of the pin ( 3 ) is oval. 10. Sandwich insert according to one of claims 1 to 9, characterized in that the sliding shell ( 1 ) has a spherical or a stepped design on its outside. 11. Sandwich insert according to one of claims 1 to 10, characterized in that the plastic jacket ( 2 ) clasps the slide shell ( 1 ) at its open end. 12. Sandwich insert according to one of claims 1 to 11, characterized in that the sliding shell ( 1 ) is pressed into the plastic jacket ( 2 ).