Socket for hip joint prosthesis

Abstract

This invention relates to a socket for a hip joint prosthesis which allows a great freedom of motion over at least 60.degree., with at least two externally fixed pins, wherein the rim of the socket is offset over at least a section relative to the plane of the rim to form a notch parallel to the rim. The socket has also means for its exact and rapid positioning in the acetabulum.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a socket for a hip joint prosthesis, with at least two externally fixed pins and a notch.

Such joint sockets are a part of a total hip prosthesis for use in surgical procedures.

In the German Pat. No. 1,806,323 a hip socket is described, wherein its rim has an inclined cut at a portion of the shell, forming planes with an obtuse angle and is made of plastics material. Further is known a hip socket, disclosed in the U.S. Pat. No. 2,910,978, which has three anchoring spikes and a notch with an enlarged inner end portion.

All these known hip sockets have the disadvantage to impair the freedom of motion of the femoral neck portion and hence of the leg especially in the medial direction, and they cannot be positioned correctly in an easy way in the acetabulum.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a socket for a hip joint prosthesis which has none of the described disadvantages.

This goal is reached with a hip socket, wherein its rim is offset over at least a section of the circumference relative to the plane of the rim, and wherein the section of the rim which lies in the plane of the rim has at least one opening.

In an advantageous modification, the plane of the rim and at least a part of the offset section lie in parallel planes.

The invention allows, relative to known means, an increased freedom of motion of the hip joint, a reduced susceptibility for a luxation and an easy and correct positioning in the acetabulum.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows is a top plan view of a preferred embodiment of a hip socket according to the present invention,

FIG. 2 is a sectional view of the socket taken along line II--II of FIG. 1,

FIG. 3 is a bottom plan view of the hip socket of FIG. 1, and

FIG. 4 is a side elevational view of the hip socket of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

It can be seen from FIG. 1 that the hip socket 1 has several ribs 2, which extend radially over the substantially hemispheric shell. As shown in FIG. 2, the shell defines a substantially hemispherical cavity to receive the ball of the femur. There are further two parallel upright pins 3, in which are cut the grooves 4, through which the waste cement can flow when the socket 1 is cemented in the acetabulum. On the side of the opening of the shell the hip socket is bordered by an outwardly protruding rim 5 which extends over at least a section of the circumference. Advantageously the rim 5 extends over about 300.degree. of the circumference of the shell and has a substantially annular face which lies in one plane 6 (FIG. 4). The remaining 60.degree. of the circumference form a notch 7, from which at least a part lies in a plane 8 which is parallel to plane 6 (FIG. 4) and over which the face of the rim is interrupted from the outside of the shell to the cavity. As a result a great freedom of motion is achieved over at least 60.degree., in contrast to the mentioned, known prostheses, which allow a great freedom of motion only at one point.

Opposite to notch 7 the rim 5 has an opening 10, which serves for the rapid and precise positioning of the hip socket 1 in the acetabulum. To this end a wire is drilled in the bone together with the holes for the pins 3, the wire being positioned exactly relative to the holes and remaining in the bone. The opening 10 can thus glide along the wire and guide exactly the pins 3 towards their respective holes. This can be very important because the cement hardens fast and there is not much time left for fastening and positioning the socket.

An appropriate method of operation is described in the pending U.S. application, Ser. No. 347,621, filed Apr. 4, 1973 by the same applicant, which describes the drilling of the holes and wire with special instruments more in detail.

FIG. 2 shows that notch 7 is bevelled inwardly. This bevelling 9 is advantageously not even but has a slight rounding to increase the freedom of motion of the prosthesis in this section.

To avoid any damage to the ball of the femur head, which is advantageously made of plastics material and which is inserted in the hip socket according to the invention and made preferentially of a Cr-Co-Mo alloy, the edges 7a of notch 7 are shaped according to FIG. 3.

It is clear that the invention is not restricted to the described embodiment, as particular elements of the hip socket can be varied. In particular the notch 7 and the rim 5 can be dimensioned such that the freedom of motion of the prosthesis reaches over 60.degree..

Claims

What we claim is:

1. A socket for a hip joint prosthesis comprising a substantially hemispherical shell defining a substantially hemispherical cavity and terminating in a rim having a substantially annular face, said hemispherical shell defining a notch in a wall thereof interrupting the face of said rim from the outside of said shell to said cavity and over a section of the circumference less than half thereof, the face of said rim and at least a part of said notch being disposed respectively in two planes which are parallel to each other, said shell defining guide means for enabling precise positioning of the socket in the acetabulum.

2. A socket according to claim 1, wherein said guide means includes two upwardly protruding pins and an opening in said rim adapted for cooperation with a guide wire.

3. A socket according to claim 2, wherein said upwardly protruding pins are parallel.

4. A socket according to claim 2, wherein each of said pins defines a cement accommodating groove.

5. A socket according to claim 1, wherein an interior edge of said rim is rounded, and wherein said notch extends over about 60.degree..

6. A socket according to claim 1, wherein an interior edge of said notch is beveled.

7. A socket according to claim 6, wherein said beveled edge of said notch is rounded.

8. A socket according to claim 2, wherein said opening in said rim lies diametrically opposite to said notch.