Acetabular component with improved liner seal and lock

Abstract

An acetabular component for a hip replacement system comprises an acetabular shell, and a liner having a seal for insertion into the acetabular shell. In the preferred embodiment, the shell has a smooth tapered surface in its peripheral inner surface, and the liner has several annular ridges protruding from its outer surface. Upon insertion of the liner into the shell, the annular ridges of the liner come into sealing engagement with the smooth tapered surface of the shell. This sealing engagement substantially prevents a migration of debris along an interface of the liner with the shell. The liner is provided with several peripheral tabs for interference fit with several peripheral notches in the shell. An interlock comprising another liner ridge and a shell groove, provide a positive engagement to hold the liner in the shell as it bottoms therein. In an alternative embodiment, each notch is provided with protruding lips which project into the notch and firmly grasp one of the tabs of the liner upon insertion of the liner into the shell. In this manner, micromotion between the liner and the shell is substantially inhibited.

Description

[0001]This application is a continuation of application Ser. No. 08 / 466,607 filed on Jun. 6, 1995 now abandoned.This is a reissue of U.S. Pat. No. 5,766,260, issued Jun. 16, 1998, which was based on application Ser. No. 08 / 847,887, filed Apr. 28, 1997, which is a continuation of application Ser. No. 08 / 466,607, filed Jun. 6, 1995, abandoned.BACKGROUND OF THE INVENTION[0002]Prosthesis components for replacing anatomical joints are well known in the art, including total hip replacement systems. These systems include acetabular components and femoral components which interact with the acetabular components to replicate the articulation between the head of a femur and an acetabulum, or cotyloid cavity, of a pelvic girdle. The acetabular component typically comprises two parts, a metal acetabular shell and a polyethylene liner for insertion into the acetabular shell.[0003]Acetabular shells typically have openings in the shell, including screw holes, which give rise to at least two proble...

AI Technical Summary

Benefits of technology

[0008]The acetabular component for a hip replacement system according to the present invention comprises an acetabular shell and liner, with an integrally formed seal and interlock. The seal is formed between the acetabular shell and the liner upon insertion and interlock of the liner into the acetabular shell. The seal is provided to substantially prevent a migration of poly debris along an interface of the outer surface of the liner with an inner surface of the acetabular shell. The interlock provides a positive engagement between the liner and shell to indicate a complete and proper seating of the liner and shell. The outer surface of the liner is of a shape complementary to the inner surface of the acetabular shell so that substantially all of the outer surface of the liner is supported by the acetabular shell upon insertion of the liner into the shell.

[0010]The sealing engagement of the seal ridges with the smooth portion prevents debris generated by the articulation of a femoral head component with the inner surface of the liner from migrating along the liner / shell interface. This ultimately prohibits the debris from passing through openings in the acetabular shell and damaging the bone into which the acetabular component is implanted. Typically, these openings in the acetabular shell include screw holes provided for attaching the acetabular shell to the bone with bone screws.

Problems solved by technology

Acetabular shells typically have openings in the shell, including screw holes, which give rise to at least two problems.

First, wear debris that is generated from the articular movement between a femoral head component and the liner can migrate between the liner and the acetabular shell, pass through the openings in the acetabular shell, and cause damage to the bone into which the acetabular shell is implanted.

Second, debris can also be generated as a result of minor movement between the liner and the acetabular shell, commonly known as micromotion.

This debris can also pass through the openings in the acetabular shell and cause damage to the bone.

While these interlocking means serve to reduce the amount of debris generated by micromotion, they fail to solve the problem of migration of debris from the prosthetic articular surface between the acetabular shell and liner.

Thus, despite these efforts, large numbers of polyethylene particles still have access to the acetabular bone.

The main disadvantage of this approach is that the plugs fail to prevent the migration of debris through holes that have bone screws inserted therethrough.

The debris will still migrate around the screws and through the holes, and ultimately damage the bone.

Additionally, many acetabular components are now made without screw holes to prevent migration of polyethylene debris into bone behind the metal shell, but this can compromise fixation of the shell to bone in cases in which screws are necessary.

The inventor herein is aware of only one design that obviates both of the problems mentioned above, but the usefulness of this design has its own limitations.

Because the taper interface must fit tightly with each other to be effective, it is virtually impossible to seat the polyethylene liner onto the inner dome surface of the metal shell.

Although such a configuration does provide a sealing effect between the liner and the acetabular shell, the design is unsuitable as liners formed from polyethylene deform over time which interferes with the desired smooth motion between the head and liner.

Moreover, because all the load exerted on the liner is concentrated at the peripheral interface with the acetabular shell, the thickness of the shell must be relatively large, which, for acetabular components of smaller joints, requires a relatively and unacceptably thin liner.

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