DE4211347C2 - Cup for a hip joint endoprosthesis - Google Patents

Description

The invention relates to a cup for a hip joint endoprosthesis, with a metallic outer shell and with one in the outer shell arranged inner shell, which consists of plastic material and a cavity in the form of a spherical section for receiving a has prosthetic femoral head, the outer shell and the Inner shell, starting from the edge of the pan, has a meridial one Has recess.

From DE 91 01 766 U1 is a pan of the type mentioned known, which has an outer shell and an inner shell, wherein both shells a meridial, starting from the edge of the pan, have side recess. The recess in the outer shell corresponds to the anatomically predetermined shape of the incisura acetabuli,  and the recess of the inner shell is designed to the freedom of movement of the femur when implanted Improve hip prosthesis. The outer shell becomes form-fitting anchored in the natural pelvic bone and in this way the entire pan stability and sufficient adhesion with the given to human pelvic bones. The inner shell is regular positively mounted and exists in the recess of the outer shell made of relatively thick-walled plastic material with a cavity in Shape of a spherical section that the head of a prosthetic Femur part of the hip joint endoprosthesis and one abrasion-free joint movement over the longest possible To ensure the period. The high level of dimensional stability which the entire pan is lent through the outer shell prevented however, a sufficiently tension-free shape adaptation while walking solution of the prosthesis to the constant change in shape of the natural Acetabulum, which changes the natural movement or is even disturbed.

From EP 0 051 729 A1 a concentric acetabular implant known which one about the axis of rotation of the inner surface shows recess running out and is horseshoe-shaped. This well-known socket implant is intended to be the part of the articular surface replace, which due to its structure and cartilage thickness than wear de support surface for the femoral head. So little natural having to replace alloplastic tissue as possible, this well-known socket implant has the thinnest possible Wall thickness and should cover the entire surface with the natural pelvic bones are firmly anchored.

From DE 33 31 191 C2 a plastic pan for cement-free Anchoring known in the pelvic bone, its hemispherical Cavity has an eccentricity to the outer surface, in which anchoring peg on the thick-walled area on the outer surface is arranged. To ensure good and low-stress deformability  To achieve the entire pan is a slit-shaped recess provided that starts from the thin-walled pan area and itself extends at least to the axis of rotation of the cavity. The Shape adaptation of this plastic provided with a recess pan is therefore very large. The constant walking movements of the prothe table femoral head can give way through deformation, so that the abrasion between the prosthetic femoral head and the socket cavity space is reduced. However, it happens because of the low Dimensional rigidity of the pan to undesired relative movements between the plastic pan and the pelvic bone or one previously cement layer applied to the bone, so that on the outside surface of the plastic pan creates an undesirable abrasion that to particle migration in the tissue, and thus leads to pain.

The object of the invention is therefore a pan of the beginning ten kind so that on the one hand the pan the natural Follow the movements of the pelvic bone with sufficient flexibility can, on the other hand compared to pure plastic pans Relative movement between the pan and pelvic bone is reduced.

This task is invented in the pan of the type mentioned at the beginning solved according to the invention in that the recess of the outer shell runs at least to its pole, and that the outer surface of the metallic outer shell in predetermined area sections has open-pore or open-cell structure.

The advantages of the invention are in particular that the necessary elasticity to adapt to the shape of the pelvis in two stages, namely by means of those reaching at least to the pole Recess of the outer shell and by means of the recess on the edge the inner shell is realized, and in particular in that Relative movement between the outer shell and bone and between the The outer shell and the inner shell are highly polished metal surfaces are seen that significantly reduce the inevitable abrasion.  

It is therefore possible according to the invention to determine the overall rigidity of the Pan system in the desired way - compared to the known slotted plastic pan - to increase and therefore better to the Adjust the elasticity of the natural bone, but the necessary adaptation of the shape of the inner pan to the walking movement of the to ensure prosthetic femoral head. In addition, the unwanted relative movement between the plastic material and the Bones or the bone cement avoided, the relative movement distributed to the movement between the pelvic bone and the outside surface of the outer pan and between the inner shell and the Inner surface of the outer pans, and these relative movements cause Chen significantly reduced abrasion, since each one is polished Metal surface takes part in the relative movement. Furthermore the socket according to the invention enables resection in the implant to be carried out very economically, namely in the area of the Aus no resection is required.

The outer surface of the metallic outer shell is given in Section sections with an open-pore or open-cell Provide structure in which bone tissue can grow, whereby in these sections a flat and firm bond between the outside shell and pelvic bones are created.

Length, width and the rest of the shape of the preferably slit-shaped The recesses of the outer shell and the inner shell place the desired deformability of the entire pan. These parameters can be chosen so that a desired low-stress shape adaptation solution to the constant changes in shape of the natural acetabulum can be achieved while walking with little abrasion.  

The recesses in the outer shell and the inner shell have approximately the same shape, with preference the recess of the inner shell is larger than the outside taking the outer shell. Both recesses have same orientation so that the inner shell itself only on the inner surface of the outer shell, but not through the larger recess on the bone trims to even a small surface contact between Inner shell and bone tissue or bone cement too prevent.

Is particularly preferred for primary fixation of the socket at least one fastening element, preferably a kno screw, radially through the outer shell directed to the outside and serves to fasten the outer scha le in the pelvic bone. The inner shell can be preferred after placing the fastener, e.g. B. means attach a snap connection to the outer shell.

The outer surface of the outer shell is particularly preferred in the cranial area with an open-pore or open provided cellular structure so that the bone tissue in this structure grows in, which in this area  a flat solid bond between the outer shell and Bone arises, which is the anchorage by means of the befe Stigungselementes improved, but in this Area the natural elasticity of the bone derjeni adapts to the metal.

The inner shell can also be particularly preferably in a predetermined, preferred cranial area or firmly attached to the outer shell at its edge the.

Advantageous developments of the invention are through characterized the features of the subclaims.

The following is an embodiment of the invention explained in more detail with reference to the drawing.

Show it:

Fig. 1 shows a cross section through the outer cup and inner shell of a ladle;

FIG. 2 shows a top view of the open side of the pan according to FIG. 1; and

Fig. 3 is a plan view of the outer shell of FIG. 1.

Figs. 1 to 3 show a pan of a Hüftge steering endoprosthesis in an overall view, Fig. 1 and 2 and in a single view of the outer cup, Fig. 3. The outer shell 2 is made of metal, has an outer surface 3, which in the cranial Edge area with an open-pore or open-celled metal structure 9 is seen ver, cf. Fig. 3. The outer pan 2 is bounded towards its open end by an edge 8 , which may have an inward bead 6 . The outer shell 2 also has a bore 7 through which a fastener, for. B. a bone screw can be anchored in the bone tissue.

In the outer shell, the z. B. around a through the pole 1 a axis of rotation 1 can be rotationally symmetrical, an inner shell 20 made of plastic material is used, which has a cavity 22 in the form of a spherical section which is limited by an inner surface 24 . The inner shell 20 has an edge surface 26 toward the open end of the pan. The outer surface of the inner shell 20 is adapted to the inner surface 4 of the outer shell 2 , and between the outer shell and the inner shell a suitable snap connection, z. B. an inward edge bead 6 of the outer shell and a corresponding recess of the inner shell, realized Lichen.

The outer shell 2 has a from the pan edge 8 meri dial extending recess 10 , which extends in the Darge embodiment to the axis of rotation 1 or the corresponding pole 1 a beyond. The width of the recess 10 increases towards the pole 1 a of the outer shell 2 .

According to FIG. 2, the inner shell 20 also has a meridially extending recess 30 starting from the edge surface 26 , which likewise extends — in the embodiment shown — beyond the axis of rotation 21 of the inner shell 20 . The recess 10 and the recess 30 have approximately the same course, but the recess 30 is dimensioned such that the inner shell 20 does not protrude into the recess 10 of the outer shell 2 when the inner shell and outer shell are inserted into each other so that the two recesses 10th , 30 seen in the direction of axis 1 are aligned. A firm connection between the inner shell 20 and the outer shell 2 takes place, for. B. on the circumferential edge of the snap connection 6 , 7 or a rich in the cranial loading area flat connection instead.

The axis of rotation 1 of the outer shell 2 and the axis of rotation 21 of the inner shell 20 run parallel to one another and have an eccentricity e to one another in the exemplary embodiment shown.

Claims (11)

1. pan for a hip joint endoprosthesis, with a metal outer shell and with an inner shell arranged in the outer shell, which consists of plastic material and has a cavity in the form of a spherical section for receiving a prosthetic Fe murkopfes,
wherein the outer shell and the inner shell each have a meridially extending recess starting from the pan edge,
characterized in that the recess ( 10 ) of the outer shell ( 2 ) extends at least up to its pole ( 1 a), and that the outer surface ( 3 ) of the metallic outer shell ( 2 ) cut in predetermined areas has an open-pore or open-cell structure. 2. Pan according to claim 1, characterized in that the recess ( 30 ) of the inner shell ( 20 ) extends over the axis of rotation ( 21 ) of the inner shell ( 20 ). 3. Pan according to one of the preceding claims, characterized in that the recesses ( 10 , 30 ) to the pole ( 1 a) of the outer shell ( 2 ) widen out. 4. Pan according to one of the preceding claims, characterized in that the recesses ( 10 , 30 ) of the outer shell ( 2 ) and the inner shell ( 20 ) have approximately the same shape and are arranged in alignment with one another. 5. Pan according to one of the preceding claims, characterized in that for primary fixation at least one fastening element ( 5 ) through the outer shell ( 2 ) is directed radially outwards into the adjacent bone tissue. 6. Pan according to claim 5, characterized in that the fastening element ( 5 ) is a bone screw. 7. Pan according to one of the preceding claims, characterized in that the outer surface ( 3 ) of the outer shell ( 2 ) has an open-pore or open-cell structure only in the cranial area. 8. Pan according to one of the preceding claims, characterized in that the inner shell ( 20 ) is firmly connected to the outer shell ( 2 ) only in a predetermined area. 9. Pan according to one of the preceding claims, characterized in that the inner shell ( 20 ) on the edge ( 8 ) of the outer shell ( 2 ) can be latched. 10. Pan according to one of the preceding claims, characterized in that the axis of rotation of the cavity ( 22 ) of the inner shell ( 20 ) has an offset against the pole ( 1 ) of the outer shell ( 2 ). 11. Pan according to claim 8, characterized in that the inner shell ( 20 ) only locally in the cranial area on the inner surface ( 4 ) of the outer shell ( 2 ) is BEFE Stigt.