WO1999012498A1 - Prosthetic member - Google Patents

Abstract

The present invention relates to a prosthetic member (10) that comprises an anchoring recess (26) allowing for the growth of bony tissue. This prosthetic member is made in the shape of a forged part comprising a plurality of prosthesis sections (10A, 10B, 10C) which can be forged respectively using a two-part forming tool.

Description

 Prosthesis part

The invention relates to a prosthesis part according to the preamble of claim 1.

Such a prosthesis part is described in DE 37 07 518 AI.

After implanting such a prosthetic part, cancellous bone grows between the anchoring pillars of the anchoring cage, as a result of which the prosthetic part is dynamically and firmly connected to the end of the femur.

Such prosthetic parts have so far been precision castings. The production of the lost molds is associated with high costs, so that the prosthesis parts are also expensive.

The present invention is intended to develop a prosthesis part in accordance with the preamble of claim 1 in such a way that it implants the advantages without cement

Prosthesis parts with an open anchoring cage, which offers a variety of anchoring surfaces, but is cheaper to manufacture.

This object is achieved according to the invention by a prosthesis part with the features specified in claim 1.

By forging, anchoring cages can also be manufactured inexpensively in small series. The malleable metals from which the prosthetic part according to the invention according to, are also characterized by good strength and toughness, as is desired for prosthetic parts. The metal is also given a favorable structure by forging.

Advantageous developments of the invention are specified in subclaims.

A prosthesis part, as specified in claim 2, has on the one hand an open structure which is particularly favorable for the ingrowth of cancellous bone, but can still be produced inexpensively, the contour of the anchoring pillars partly by forging in the die and partly by machining is generated. Machining can be carried out inexpensively on numerically controlled machine tools despite the relatively complicated contour of the anchoring cage, the latter being controlled on the basis of the drawing data for the anchoring cage.

With the development of the invention according to claim 3, it is also possible to manufacture the surface sections of the anchoring pillars facing away from the outer surface of the cage, that is to say inwards, by drop forging or to produce them in a simpler manner by machining, since there is good access to these surfaces.

When building a prosthesis part from several segments, the different cage segments are held together in a very simple manner.

By attaching the holding elements according to claim 5, a very robust and withstand high loads blocking the holding elements- With the development of the invention according to claim 6, an improvement in the cohesion between the different cage segments is again achieved.

Alternatively, the cage segments can also be connected by welding, as specified in claim 7.

According to claim 8, an anchoring cage is obtained in a very simple manner with a simple geometry of the plate-shaped cage segments.

The development of the invention according to claim 9 is advantageous with regard to a good ingrowth of the cancellous bone and with regard to keeping notch stresses in the latter.

The development of the invention according to claim 10 is advantageous with regard to simple geometry of the prosthesis segments with a large anchoring area and provision of a large number of anchoring shoulders.

If, according to claim 11, the prosthesis part is made up entirely of plate-shaped cage segments, overall there are particularly favorable production costs with a well-open anchoring cage.

The developments of the invention according to claims 12 to 14 are advantageous with regard to a particularly intimate mutual penetration of bone structure and anchoring cage.

The production of the prosthesis part from titanium or a titanium alloy according to claim 15 is with regard to high mechanical resilience and good biocompatibility of the prosthesis part are an advantage.

The invention is explained in more detail below on the basis of exemplary embodiments with reference to the drawing. In this show:

FIG. 1: a lateral, ventral view of a prosthesis part for an artificial hip joint;

FIG. 2: a top view of the right, medial side of the prosthesis part shown in FIG. 1, with a support pin being shown in axial section;

3 shows a lateral, ventral view of a central prosthesis segment of the prosthesis according to FIGS. 1 and 2;

FIG. 4: an axial top view of a modified anchoring pillar for the prosthesis segment according to FIG. 3;

FIG. 5: a top view of a modified middle prosthesis segment which can be used instead of the prosthesis segment according to FIG. 3;

FIG. 6: a section along the section line VI-VI from FIG. 5;

FIG. 7: a lateral, ventral view of a further central prosthesis segment which can be used in the prosthesis part according to FIGS. 1 and 2;

Figure 8: an enlarged partial section through the thesis segment according to Figure 7 along the section line VIII - VIII there;

FIG. 9: a ventral view of a further middle prosthesis segment which can be used in the prosthesis part according to FIGS. 1 and 2;

Figure 10; an enlarged partial section through the prosthesis segment of Figure 9 along the section line X - X;

FIG. 11: a ventral view of a prosthesis blank for a further modified prosthesis part;

FIG. 12: a section along the section line XII-XII from FIG. 11; and

Figure 13: a section perpendicular to the central plane through another prosthetic part.

A prosthesis part, which serves for implantation in the upper end of a femur 12 indicated by dashed lines, is designated overall by 10 in FIG. For this purpose, the upper section of the femur 12 carrying the joint ball is resected and a recess 14 is created in the femur, which corresponds to the clear outer contour of the prosthesis part 10.

The prosthesis part 12 has a support plate 16 which has a horizontal plate section 18 and a plate section 20 which rises obliquely upwards towards the minor trochanter. A support pin 22, which rises obliquely upwards, is formed on the plate section 18, onto which a joint ball 24, indicated by dashed lines, can be placed. An anchoring cage, designated overall by 26, is cast onto the underside of the support plate 16. This cage structure consists of four curved longitudinal anchoring posts 28, 30, 32, 34, which essentially define the shape of a curved pyramid with a rectangular cross section at the top and an increasingly round cross section at the bottom. Two curved additional anchoring posts 36, 38 extend from the upper end of the plate section 18, the shape of which is adapted to the greater trochanter of the femur and which are at a smaller distance from one another than the adjacent anchoring posts 32 and 34.

In the interior of the clear contour of the anchoring cage 26 predetermined by the anchoring posts 28-38, further anchoring posts are provided which run in oblique directions between the anchoring posts 28-38. Of these, three such anchoring pillars 40, 42, 44 that also stiffen the anchoring cage 26 are shown.

The anchoring pillars each have a cylindrical core 46 with a large number of axially spaced anchoring collars 48.

Typically, the cores 46 of the anchoring posts 28 to 34 have a diameter of 2.0-4.5 mm, the diameters of the anchoring collars are each approximately 0.8-1.5 mm larger than the diameter of the cores. The axial

Extension of the anchoring collars is approximately 0.6-1.2 mm, their distance from each other approximately 3-6 mm.

The cores can have a diameter of approximately 1.5-3 for the stiffening inner anchoring pillars 40, 42, 44 mm, the diameter of the anchoring collars is approximately 0.6-1.2 mm larger than the core diameter, and the axial dimension of the anchoring collars can be approximately 0.5-1 mm, their axial spacing approximately 2-4 mm.

A shaft section 50 is molded onto the lower end of the anchoring cage 26. This has an olive-shaped end section 52. A channel 54 extends through the interior of the shaft section 50.

To implant the prosthesis part described above, the end of the thigh bone is resected as described above, the upper edge of the cortical being receiving a contour corresponding to the edge contour of the support plate 16. The bone material removed from the bone end during the production of the recess 14 is ground in a bone mill and filled into the anchoring cage 26. The prosthesis part 10 is then inserted into the proximal end of the femur 12, so that the support plate 16 now forms a new upper end for the bone.

After insertion of the prosthesis part 10, it is connected to the upper end of the femur in a partially load-bearing manner. In the further healing process, the ground cancellous bone grows together and fills the cage structure, while growing up against the corticalis and the remaining cancellous bone remains.

After the healing process has ended, there is a continuous cancellous bone volume in the area of the anchoring cage 26, which has grown around the cage structure.

As can best be seen from FIG. 2, the prosthesis part 10 consists of three prosthesis segments: one in FIG 2 prosthesis segment 10A on the left comprises the anchoring posts 28, 30 and adjacent anchoring posts, which lie in the area predetermined by the anchoring posts 28, 30 or run parallel to the latter. Furthermore, the prosthesis segment 10A includes a segment 16A of the support plate 16, a segment 50A of the shaft section 50, an upper pin segment 60A, and a pin segment 62A located below.

Correspondingly, a central prosthesis segment 10B comprises those anchoring pillars which run in or adjacent to a central plane of the prosthesis part 10, a segment 16B of the support plate 16, a segment 50B of the shaft section 50, an upper pin segment 60B and a lower pin segment 62B. A slot in the segment 50B of the shaft section 50B (similar to that shown in FIG. 3) forms the channel 54 together with slot-free shaft sections 50A and 50C of the prosthesis segments 10A and IOC.

Finally, a prosthesis segment IOC located on the right in FIG. 2 comprises the anchoring pillars 32, 34 and further anchoring pillars which run in the area predetermined by the anchoring pillars 32, 34 or are adjacent to it, a segment 16C of the supporting plate

16, a segment 50C of the sheep section 50, an upper pin segment 60C and a lower pin segment 62C.

The top pin segments 60A, 60B, 60C taken together form an inner pin, onto which the support pin 22, which is designed as a cup-shaped part, is shrunk in the hot state.

Similarly, the underlying pin segments 62A, 62B and 62C together form an inner pin on which an end piece 64 is shrunk in the hot state.

In this way, the three prosthesis segments 10A, 10B and IOC are held together firmly at the upper and lower ends.

The individual prosthesis segments are free of undercuts and can be forged in a two-part die shape. Any burrs remaining after drop forging are removed by machining.

If desired, it is possible to provide small projections and depressions which cooperate on the contact surfaces between the individual prosthesis segments and which together form positioning interlocking connections.

FIG. 3 shows a modified middle prosthesis segment 10B:

A downwardly extending wall 66 is formed on the segment 16B of the support plate 16, the edge contour of which is selected in accordance with the clear outer contour of the prosthesis part 10.

Anchoring pillars 68 are formed on the wall 66, perpendicular to the wall plane, which in turn have a core 70 and axially successive anchoring collars 72 carried by it. A plurality of through openings 74 are also provided in the wall.

The anchoring posts 68 are made from pillar blanks by machining, which are attached to the wall 66 when the prosthesis segment 10B is forged. were formed. Except for a small remaining web, the passage openings 74 are also made by drop forging, the opening walls having a substantially semicircular cross section. The webs remaining in drop forging are cut out with a tool.

The prosthesis segment 10B can also be inexpensively manufactured in a two-part die shape; machining can be carried out inexpensively and quickly.

For the machining of the anchoring piers

68, the anchoring surfaces working together with the cancellous bone can be provided in the form of anchoring channels instead of in the form of anchoring bundles, as shown in FIG. 4. These anchoring surfaces lie in the forging direction and can thus also be produced when the prosthesis segment 10B is forged.

Filling the interior of the anchoring cage 26 delimited by the four anchoring pillars 28, 30, 32, 34 with anchoring surfaces can also be carried out in accordance with FIGS. 5 and 6 in such a way that one forges a wall 66 formed on the segment 16B during die forging Protruding anchoring ribs 76 are formed on the wall sides.

The anchoring ribs 76 are arranged like a net or truss and not only increase the contact area with cancellous bone that is to be illuminated, but also stiffen the wall 66.

These can have different and contoured heights (extension perpendicular to the plane of FIG. 5), as is desired in each case for filling the cage structure. Through openings 77 are machined into the anchoring ribs 76 by machining.

Even with such a prosthesis segment, a good mechanical connection is obtained between cancellous bone that has grown back into the interior of the anchoring cage 26 and the prosthesis part 10.

In the prosthesis segment 10B according to FIGS. 7 and 8, anchoring ribs 76, which carry successive anchoring collars 79 in the longitudinal direction of the ribs, which are similarly dimensioned as the main anchoring pillars 38 to 34, are forged onto a wall 66 hanging from the support plate segment 16B in the direction of the main stress lines. The height (extension perpendicular to the plane of the drawing) of the anchoring ribs 76 is again chosen as is desired in view of filling the space spanned by the anchoring pillars 28 to 32 with anchoring surfaces. If desired, the anchoring ribs 76 can again be provided with through openings (corresponding to the through openings 77 of FIG. 6).

The prosthesis segment 10B according to FIGS. 9 and 10 is very similar to that according to FIGS. 7 and 8, only the wall 66 is omitted and the shaft section segment 50B is connected to the support plate segment 16B via three of the anchoring ribs 76, which now extend on both sides of the central surface of the prosthesis segment 10B . In this way, the anchoring cage of the prosthesis part obtained with the prosthesis segment 10B according to FIGS. 9 and 10 is even more open.

According to FIGS. 11 and 12, one can produce a Prosthesis part 10 also start from a one-piece blank, which is already provided with all desired surface contours of the anchoring pillars during die forging, insofar as these can be produced in the pressing direction. This blank is similar to the prosthesis part 10B according to FIGS. 7 and 8, with the proviso that under the anchoring ribs 76 there are marginal ones which span the same space as the anchoring pillars 28 to 34, so that the anchoring ribs are overall higher. Alternatively, one can also start from a blank without wall 66, which corresponds to a prosthesis segment 10B according to FIGS. 9 and 10.

As can be seen from FIG. 12, the marginal anchoring ribs 76 are machined:

The material volumes 78 lying behind them are partially removed under NC-controlled machining (upper left-hand section of FIG. 12), as a result of which the inner surface of the anchoring pillars 28 to 32 and the surfaces of any further anchoring pillars lying between them and the median plane of the prosthesis part are generated .

Optionally, the side anchoring ribs can also be provided with a row of through openings 81 which follow one another in the longitudinal direction of the ribs, in which case through holes 83 are produced simultaneously in the central anchoring ribs 76, as shown in the lower right section of FIG. 12.

In the prosthesis part shown in FIG. 13, the anchoring cage 26 is formed by a multiplicity of anchoring plates 80, 82, 84, 86. The anchoring plates 80, 82, 84, 86 are alternately provided with indentations 88 from one and the other side, the whole in such a way that a two-dimensional corrugation of the plates is obtained. In addition, through openings 90 are provided in the anchoring plates, which, as shown at 92, have a semicircular cross-sectional edge wall.

In practice, the through openings 92 have a diameter of approximately 3 to approximately 8 mm, preferably approximately 5 mm.

The corrugation of the anchoring plates described above and the through openings 90 result in an intimate interlocking between ingrown cancellous bone material and the anchoring cage 26.

The through openings 90 of adjacent cage segments 80, 82, 84, 86 are offset from one another.

At the upper end of the anchoring plates 80, 82, 84, 86 square cross-section retaining strips 94, 96, 98, 100 are formed; narrower retaining strips 102, 104, 106, 108 are found at the lower plate ends.

The upper retaining strips 94-100 are accommodated in the interior of a recess 110 which is provided in the support plate 16, which is now thicker. The support plate 16 is shrunk onto the holding strips 94, 96, 98, 100 in the hot state.

The holding strips 94 to 108 can in turn be provided with positive locking elements, not shown, on the one hand to facilitate their alignment, and on the other hand to avoid shifting the retaining strips against each other.

Furthermore, the outer ones of the retaining strips can be provided with side surfaces which are inclined downwards and inwards, the side surfaces of the recess 110 which cooperate with these being correspondingly inclined. In this way, an even more secure connection of the holding strips to the support plate 16 is ensured after it has been shrunk on.

To hold the lower ends of the anchoring plates 80, 82, 84, 86 together, an olive-shaped end body 116 is shrunk hot analogously onto the lower holding strips 102, 104, 106, 108.

It is understood that the edge contour of the individual anchoring plates 80, 82, 84, 86 is selected to be similar to that of the prosthesis segments 10B and the anchoring plates have been given such a macro curvature during die forging that the overall desired desired outer contour of the anchoring cage 26 is obtained.

The anchoring plates 80, 82, 84, 86 are manufactured in such a way that flat blanks including the upper and lower holding strips are first produced, with the through-holes 90 already being produced with the appropriate drop forging, except for a small, permanent middle bar. Then these small bars are cut out and the impressions are made in one or more further forging steps

88 generated and the macro curvature of the anchor plates worried. The support plate 16 and the olive-shaped end body 116 are then shrunk on.

The retaining strips can be used to strengthen the connection 94 to 100 can be connected to one another by welds 118 and to the support plate 16 by welds 120. A similar procedure can be used for the lower holding strips 102 to 108, although not shown in the drawing.

Claims

claims 1. prosthesis part with a support plate (16), on which a joint part (24) can be fastened, and with a Anchoring cage (26), which is firmly connected to the support plate (16), characterized in that at least the anchoring cage (26) consists of forgeable material and at least the anchoring cage (26) is a forged part. 2. Prosthesis part according to claim 1, characterized in that the anchoring cage (26) a plurality of Anchoring pillars (28-44; 28-34, 68; 76), each having a pillar core (46; 70; 75) and successive anchoring collars (48; 72; 79) arranged thereon or through openings (72) formed therein and that the anchoring pillars (28-44; 28-34, 68; 76) are formed on their faces in the outer surfaces of the anchoring cage (26) by die forging and on their surfaces facing the inside of the cage by machining. 3. Prosthesis part according to claim 1 or 2, characterized in that it consists of a plurality of firmly connected prosthesis segments (10A, 10B, IOC) which are each formed on both sides by either die forging and / or machining. 4. prosthesis part according to claim 3, characterized in that the prosthesis segments (10A, 10B, IOC) are held together by parts of the same overlapping holding elements (22; 16, 116). 5. prosthesis part according to claim 4, characterized in that the holding elements (22, 64; 16, 116) are shrunk. 6. prosthesis part according to claim 4 or 5, characterized in that the holding elements (22, 66; 16, 116) are welded to the prosthesis segments (10A, 10B, IOC). 7. prosthesis part according to one of claims 1 to 6, characterized in that the prosthesis segments (10A, 10B, IOC) are welded together. 8. The prosthesis part according to one of claims 3-7, characterized in that at least one of the prosthesis segments (10B) has a plate {66; 80, 82, 84, 86). 9. prosthesis part according to claim 8, characterized in that the edge walls (92) of the through openings (90) are crowned, in particular have a semicircular transverse cross section. 10. Prosthesis part according to one of claims 3-9, characterized in that at least one of the prosthesis segments (10B) has a plate section (66) which on at least one side with anchoring pillars (68 ) is provided. 11. Prosthesis part according to one of claims 8-10, characterized in that the cage structure (26) by plate-shaped cage segments (80, 82, 84, 86) is formed. 12. Prosthesis part according to claim 11, characterized in that the cage segments (80, 82, 84, 86) are corrugated, preferably corrugated in two directions (88). 13. Prosthesis part according to claim 11 or 12, characterized in that the plate-shaped cage segments (80, 82, 84, 86) have a plurality of through openings (90). 14. Prosthesis part according to claim 13, characterized in that the through openings (90) of adjacent cage segments (80, 82, 84, 86) are offset from one another. 15. Prosthesis part according to one of claims 1 to 14, characterized in that it is made of titanium or one Titanium alloy is made.