Cup

Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone

Patent

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Details

623 18, A61B 232

Patent

active

057024731

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION

The present invention relates to a cup-shaped member for a hip joint prosthesis for implantation into a cavity in the bone tissue in the acetabulum. The cup-shaped member comprises an acetabular cup made of metal, a ceramic or any other suitable material, preferably of titanium. The exterior shape of the cup-shaped member is rotationally symmetrical around a central axis of symmetry.


BACKGROUND TO THE INVENTION

Artificial hip joints have been used and implanted into humans for a long period of time. The joints normally comprise one femoral part which is intended to be inserted or implanted into the femur and which carries a ball-shaped articulation element, normally made of metal or a ceramic material. The joint further normally comprises a cup-shaped member, i.e., an acetabular cup, which is to be inserted into or attached to the acetabulum, and which is to hold a complementary, cup-shaped liner, normally made of Ultra High Molecular Weight Polyethylene (UHMWPE) or a similar polymer material, in which the ball-shaped element is to articulate or rotate.
The depth of the bone tissue which is available in the acetabulum for attaching the acetabular cup is limited in most directions. The acetabular cup per se is furthermore rather flat and shallow, which means that the cup at least to some extent may be considered to be more or less placed directly onto the surface of the bone tissue and not into the bone tissue, this in contrast to most other commonly used bone implants, such as screw-shaped dental implants or standard femoral implants. These factors make it difficult to design an acetabular cup that easily will be attached to the bone tissue by means of the shape of the cup or to design efficient attachment means for the cup.
Some prior art acetabular cups are disclosed in for instance DE-A-24 54 635, DE-A-26 45 101, U.S. Pat. Nos. 3,903,549 and 4,795,470.
A metal which is commonly used in bone implants is titanium because of its proven affinity with bone tissue and its good biocompability. One particular property of titanium is its tendency to form a close connection with bone tissue. The formation of this close connection is often termed "osseointegration". One factor which may be important for a proper ossseointegration process is a relatively good fit between implant and bone tissue. Another important factor that will affect the degree relative immobility between implant and bone tissue.
The object of the present invention is to provide an acetabular cup which provides conditions favourable to the osseointegration process by influencing the factors described above and to provide a cup which will be firmly attached to the bone tissue.


BRIEF DESCRIPTION OF THE INVENTION CONCEPT

This object is achieved in that the outer side of the cup, that is the side which is to face the bone tissue, is provided with at least one circumferentially oriented bead close to the edge of the cup-shaped element, said bead having a barb-like shape in section and consequently allowing the cup-shaped element to be pushed into said cavity but counter-acting the removal of said cup-shaped element from said cavity, said outer side including said bead(s) being provided with a rough structure serving as a file or saw when said cup is pushed and/or rotated into said cavity.
Further advantageous embodiments are set forth in the dependent claims.


BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a side view of an acetabular cup according to the invention
FIG. 2 shows a view of the cup of FIG. 1
FIG. 3 a section along the line III--III in FIG. 2,
FIG. 4 shows a perspective view of the cup and
FIG. 5 details of the thread.


DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

In this preferred embodiment the cup-shaped member comprises an acetabular cup 1 which is shown in detail in FIGS. 1-3. The cup 1 is intended to hold a complementary liner which may be attached to the cup according to any standard procedure or by any standard means.
The cup comprises two main parts, one spherical seg

REFERENCES:
patent: 4145764 (1979-03-01), Suzuki et al.
patent: 4164794 (1979-08-01), Spector et al.
patent: 4795469 (1989-01-01), Oh
patent: 4813959 (1989-03-01), Cremascoli
patent: 4871368 (1989-10-01), Wagner
patent: 4883491 (1989-11-01), Mallony et al.
patent: 4963154 (1990-10-01), Anapliotis et al.
patent: 4997447 (1991-03-01), Shelley
patent: 5108446 (1992-04-01), Wagner et al.
patent: 5263986 (1993-11-01), Noiles et al.

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