Variable geometry rim surface acetabular shell liner

Abstract

An acetabular shell liner having a variable rim surface geometry, which improves range of motion of the femoral component within the liner and decreases the incidence of dislocation and subluxation, and methods of making and using the acetabular shell liner. Prosthetic devices, more particularly hip joint prostheses, containing the acetabular shell liner having a variable rim surface geometry are also provided.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of U.S. patent application Ser. No. 09 / 808,228 filed on Mar. 14, 2001, which claims priority to U.S. Provisional Patent Application No. 60 / 189,182 filed on Mar. 14, 2000. The disclosure of this prior application is incorporated by reference in its entirety.BACKGROUND OF THE INVENTION [0002] 1. Field of The Invention [0003] This invention relates generally to acetabular prosthetic devices and more particularly to an improved acetabular shell liner wherein the liner has a variable geometry rim surface. [0004] 2. Related Art [0005] Artificial implants, including hip joints, shoulder joints and knee joints, are widely used in orthopedic surgery. Hip joint prostheses are common. The human hip joint acts mechanically as a ball and socket joint, wherein the ball-shaped head of the femur is positioned within the socket-shaped acetabulum of the pelvis. In a total hip joint replacement, both the femoral head and...

AI Technical Summary

Benefits of technology

[0018] Methods and structures according to this invention include a method of producing an acetabular liner in which the rim surface geometry varies, rather than being set, in order to optimize the range of motion and minimize interference with the neck of the femoral component. This variable geometry rim surface is employed around the edge of the internal concave surface of the liner, i.e. around the circumference of a generally hemispheric acetabular liner inside diameter, and allows for delayed interference, or impingement, with the neck or stem portion of the femoral component, resulting in an increased range of motion. Thus, this variable geometry rim surface delays when the neck of the femoral component contacts the rim surface of the liner during articulation, allowing an increase in the range of motion of the femoral component and optimization of the liner.

[0019] Increasing the range of motion has many benefits and advantages. For example, increasing the range of motion allows a patient a greater range of movement. Second, an increase in the range of motion provides the surgeon with greater room for error in component positioning, or clocking, during surgery. Since it is not currently possible to accurately measure the precise angle required for implantation of an acetabular component in a particular patient, it is difficult to place an implant at precisely the correct angle. A surgeon generally relies on personal experience in making this assessment. While a locking mechanism, such as a spline interface between the liner and the shell, is beneficial because it allows for multiple reorientations of the liner, fine tuning the positioning of the acetabular component during the intraoperative assessment of range of motion and stability is difficult and often imprecise. Surgeons will benefit from a wider range, or larger target area for acetabular component orientation provided by the increased range of motion.

[0020] Third, a broader range of motion decreases the likelihood of dislocation or subluxation, as it is less likely the femoral component will contact the rim of the liner and lever out of the internal concave surface of the acetabular component. Finally, a broader range of motion aids in preventing wear on the liner or shell. If a femoral component regularly contacts the rim surface of the liner, the liner will wear, releasing polyethylene debris. This debris may cause osteolysis when it escapes into nearby bone and tissue, which may lead to aseptic loosening of the implant. Additionally, if the liner wears thin, the neck of the femoral component may contact the metal shell, resulting in fatigue to the metal that may cause the neck or shell to break, or metal debris to be released into nearby bone and tissue.

Problems solved by technology

Since it is not currently possible to accurately measure the precise angle required for implantation of an acetabular component in a particular patient, it is difficult to place an implant at precisely the correct angle.

While a locking mechanism, such as a spline interface between the liner and the shell, is beneficial because it allows for multiple reorientations of the liner, fine tuning the positioning of the acetabular component during the intraoperative assessment of range of motion and stability is difficult and often imprecise.

Third, a broader range of motion decreases the likelihood of dislocation or subluxation, as it is less likely the femoral component will contact the rim of the liner and lever out of the internal concave surface of the acetabular component.

If a femoral component regularly contacts the rim surface of the liner, the liner will wear, releasing polyethylene debris.

This debris may cause osteolysis when it escapes into nearby bone and tissue, which may lead to aseptic loosening of the implant.

Additionally, if the liner wears thin, the neck of the femoral component may contact the metal shell, resulting in fatigue to the metal that may cause the neck or shell to break, or metal debris to be released into nearby bone and tissue.

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