WO1997036558A1

WO1997036558A1 - Shaft prosthesis part and material kit for use therewith

Info

Publication number: WO1997036558A1
Application number: PCT/EP1997/001646
Authority: WO
Inventors: Franz Copf; Srecko Herman; Wolfgang KÜSSWETTER
Original assignee: Franz Copf; Srecko Herman; Kuesswetter Wolfgang
Priority date: 1996-04-02
Filing date: 1997-04-02
Publication date: 1997-10-09
Also published as: DE19613081A1; EP0891168A1

Abstract

The invention concerns a part (18) for a prosthesis to be cemented in place, said part having a plate section (22) which projects radially over a shaft section (20) and carries a post section (28) to be provided with a joint element (30). A first through-bore (32) extends through the shaft section (20) to the top of the plate section (22). A further through-bore (34) is provided in the edge of the plate section (22) projecting over the shaft section (20). In this way, when the prosthesis part is cemented in place, an intermediate space (36) between the cavity (16) in the bone and the shaft section (20) can be forcibly filled with cement compound (56) via the first through-bore (32) whilst a vacuum is realized in this intermediate space (36) via the second through-bore (34).

Description

Prosthesis part for a stem prosthesis and material kit for use with such

The invention relates to a red tooth part according to the preamble of claim 1, and to a material kit that can be used when cementing such a.

Shaft prostheses with such prosthesis parts are used in particular in the case of artificial hip joints to replace the

Joint ball of the femur used. For their implantation, a recess is created in the bone to be provided with the prosthesis, which is slightly larger than the shaft section of the prosthesis. The recess created in the bone is then filled with a biocompatible cement, and when the shaft section is inserted into the recess, the liquid cement is increasingly displaced and the cement level rises in the bone recess towards its open end. If more viscous cement is used, it can also be applied to the outer surface of the shaft section and introduced into the bone recess together with the shaft section.

A low-viscosity cement has the advantage that it can better adapt to the microstructure of the surface of the bone recess, which is advantageous in terms of firm, reliable anchoring of the prosthesis to the bone. However, liquid cements are difficult to insert in situ in the bone recess, since the bone is generally essentially horizontal when the patient is lying down.

The present invention is therefore intended to provide a stem prosthesis according to the preamble of claim 1.

CONFIRMATION COPY be formed that the space obtained after insertion of the prosthesis between the outer surface of the shaft section and the inner surface of the bone recess can be reliably forcibly filled with liquid cement.

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

In the shaft prosthesis according to the invention, in addition to the shaft section and the pin section, there is a plate section which covers the open end of the bone which is to be provided with the prosthesis. A bore is provided in the shaft section itself, through which cement can be guided into the vicinity of the deepest point of the bone recess. The space to be filled with cement can be vented or connected to a vacuum source via the further bore provided in the plate section. In this way, the liquid cement can completely fill the above-mentioned space without trapping air bubbles.

Advantageous developments of the invention are specified in the subclaims.

In a stem prosthesis according to claim 2, the cross-sectional shape of the stem portion ensures that even with a snug fit of the stem portion into the essentially oval or round cross-sectional end portion of the bone, larger local areas of the space to be filled with cement remain, over which the cement then enters of the bone recess in the longitudinal direction. A stem prosthesis according to claim 3 is well adapted to the rough course of the volume of a femur filled with cancellous bone.

In the case of a stem prosthesis according to claim 4, it is ensured that the plate section covers the corticalis of the bone to be provided with the prosthesis at the free opening obtained by resection.

If the plate section of the prosthesis is formed according to claim 5, a larger part of the greater trochander can remain on the bone in a hip joint prosthesis.

In the case of a stem prosthesis according to claim 6, the distribution of the cement released through the first bore takes place in a substantially uniform manner (with respect to the axis of the stem portion) in the circumferential direction.

The development of the invention according to claim 7 allows regions of this recess that are remote from the deepest point of the bone recess to be filled from the start. On the one hand, this reduces the filling time and, on the other hand, allows the bore section in the lower part of the shaft section to be selected with a somewhat smaller diameter, which is advantageous with regard to the mechanical strength of the lower end of the prosthesis.

The development of the invention according to claim 8 is also advantageous with regard to the high mechanical strength of the lower part of the shaft section. With the development of the invention according to claim 9 it is achieved that the lower end of the shaft section is automatically centered when inserted into the bone recess. In this way it is ensured that the intermediate space to be filled with cement has essentially the same thickness in the circumferential direction, so that the cement flows uniformly into the various partial areas of the intermediate space.

The further development of the invention according to claim 10 is advantageous with regard to a slight obstruction of the cement flow and with regard to a good insertion of the shaft section into the bone recess.

A prosthesis according to claim 11 can optionally be used with or without a centering part. Centering parts with different basic dimensions can also be easily put on according to the respective needs.

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

1 shows a longitudinal section through the end of a thigh bone on the hip joint side with an inserted stem prosthesis part, shown at a point in time when the cement was only partially filled;

FIG. 2: a top view of the upper side of the prosthesis part according to FIG. 1;

FIG. 3: a top view of the underside of the prosthesis part according to FIG. 1; and Figure 4: a similar view as Figure 1, but in which a modified stem prosthesis part is shown.

The upper end of a thigh bone is shown at 10 in FIG. From this the joint head is sawn off along a line which is initially essentially transverse (horizontal) to the bone axis and which rises towards the greater trochander. The free edge of the corticalis thus obtained is designated by 14.

After sawing off the femoral head, a recess 16 has been created in the femur 10 by removing the cancellous bone.

A prosthetic part 18 cast from a biocompatible metal or a biocompatible alloy is shown in the interior of the bone thus prepared. It comprises a shaft section 20 which, roughly speaking, has the shape of a twisted pyramid frustum having a right-angled cross section, which increasingly becomes a circular cross section towards the small end.

A plate section 22 is located at the upper end of the shaft section 20. The upper bone end is prepared according to its edge contour. The plate section 22 has a main section 24 which drops under operating conditions at a small angle of approximately 5-10 to the bone axis and a side section 26 which rises at an angle of approximately 60 obliquely to the greater trochander from a point adjacent to the shaft axis or bone axis.

As can be clearly seen from FIG. 1, the plate section stands 22 so far over the upper end of the shaft section 20 in the radial direction that it closes the edge 14 of the femur 10 created by the bone preparation in a cover-like manner.

A pin section 28 is formed on the plate section 22 and is inclined inwards and upwards at an angle of approximately 40-70 °, in the normal case of approximately 60 to the plane of the main section 24.

A through bore 32 is provided in the shaft section 20, which extends from the lower end face of the shaft section 20 through the latter and the plate section 22 and opens out on the upper side of the plate section 22.

In the plate section 22, a second through hole 34 is provided in a region on the edge, which leads there from the upper side of the plate section 22 to its underside. The through hole 34 is aligned in the direction perpendicular to the drawing plane of FIG. 1 essentially with the base point of the axis of the pin section 28. Under operating conditions (patient lies essentially in the drawing plane of FIG. 1), the through hole 34 lies at the highest point of the Intermediate space 36 which lies between the outer surface of the shaft section 20 and the inner surface of the recess 16.

In order to fill the intermediate space 36 free of bubbles with a liquid biocompatible cement under operating conditions, the upper end of the through bore 32 is connected via a line 38 to a dispenser 40 for this liquid cement, as shown schematically in FIG. The second through hole 34 is via a line 42 is connected to a vacuum source, shown as blower 44.

In order to ensure that the intermediate space 36 is filled uniformly (in relation to the axis of the shaft section 20) in the circumferential direction and at the same time to ensure that the lower end of the shaft section 20 is centered in the recess 16, the lower shaft end is provided with a cylindrical bearing surface 46 provided, on which a centering part 48 is seated. The latter has a hub section 50 and a large number of convex spring fingers 52 which are molded onto the hub section 50.

The centering part 48 can be a part molded from a biocompatible plastic or a part made from a biocompatible

Metal or such an alloy cast or machined part. In a modification, the centering part 48 can also be formed in one piece with the shaft section 20 and the remaining prosthesis parts and, like the other sections of the prosthesis, can be made from a biocompatible metal or a biocompatible alloy or a biocompatible ceramic material.

The prosthesis part described above can be fixed as follows in the previously prepared bone end as described above:

A plug 54 is produced from the resected section of the femur, the diameter of which corresponds essentially to the cross section of the recess 16 at the deepest end. This plug is pressed against the lower end of the recess 16 using a suitable tool. Now the lines 38 and 42 are connected to the holes 32 and 34. A thicker (in practice about 1-2 mm thick) layer of a cement mass is applied to the edge of the underside of the plate section 22, the basic components of which correspond to the bio-compatible cement which is contained in the dispenser 40. However, the cement paste contains fillers or other additives which increase the viscosity, so that the cement paste acquires a pulpy consistency similar to that of a sealant.

The prosthesis part 18 is now pressed into the recess 16, the lower end of the shaft section 20 being guided and centered by the centering part 48. This axial advancement of the prosthesis part 18 comes to an end when the underside of the plate section 22 reaches the edge 14 of the open bone end. The cement mass is partially displaced inwards and outwards, as indicated at 60 and 64, from the joint between the plate section and 22, where the resection line follows the edge contour of the plate section 22 well. At other points where the edge 14 could not be worked exactly on the edge contour of the plate section 22, the cement mass forms a sealing joint, as indicated at 62. The cement paste 64, which has leaked outwards over the outer surface of the plate section 22 and the femur 10, is removed with a scraper.

Now the intermediate space 36 lying between the inner surface of the recess 16 and the outer surface of the shaft section 20 and the underside of the plate section 22 is tightly closed. The intermediate space 36 is now subjected to negative pressure and at the same time the stamp of the dispenser 40 is moved. The space 36 increasingly fills with the liquid Cement, the last section of the space filled with cement lying in front of the through hole 34, so that the space 36 as a whole is filled completely and without bubbles.

During the filling of the intermediate space 36 with cement and during the hardening of the cement (typically about 5 minutes), the surgeon can make even smaller positional corrections on the prosthesis part 18. After the cement introduced into the intermediate space 36 has hardened, the sealing joint 62 also hardens.

The plug 54, when filling the intermediate space 36 with liquid cement, prevented a larger closed cement volume from accumulating below the prosthesis part 18. The latter would be disadvantageous with regard to any necessary removal of the prosthesis part and its replacement by another prosthesis part.

The prosthesis part shown in the drawing is intended for use with a joint prosthesis for the right hip. It goes without saying that a prosthesis part for the left hip has a shape which is substantially symmetrical with the prosthesis part shown, the second through bore 34 in particular lying again at the upper edge of the plate section 22, so that it also overlies it last amounts of air can be withdrawn from the space 36.

In the modified exemplary embodiment according to FIG. 3, the first through bore 32 is a stepped bore with a diameter decreasing towards the lower end of the shaft section 20. This way the bottom end of the shaft section 20 compared to the embodiment according to FIGS. 1-3 greater wall thickness and thus greater mechanical strength. In order to compensate for the increase in the flow resistance for the liquid cement due to this reduction in cross-section, radial branch bores 66 are provided in the wall of the shaft section 20 distributed over its length and open out into the outer surface of the shaft section 20. These second bores 66 are distributed in such a way that they do not cause any significant local weakening of the shaft section 20. This can be ensured, for example, by arranging the branch bores 66 along one or more spiral lines 68.

The line 38 is preferably a flexible hose which, like the dispenser 40, is a disposable part. At the end of the line 38 designed as a hose, a truncated cone-shaped coupling piece 70 is provided, by means of which an easily producible and easily releasable connection to the free end of the through bore 32 can be established. The coupling piece 70 is frictionally seated in the correspondingly gated end portion 72 of the bore 32. In order to facilitate its removal even when contaminated with cement, it is made of a plastic material to which the cement adheres only poorly.

Claims

claims

1. prosthesis part with a shaft portion (20) which can be inserted into a bone recess (16) and a pin portion (28) on which a joint part (30) can be fastened, characterized in that between the shaft portion (20) and the pin portion (28) A plate section (22) is provided which protrudes on all sides over the shaft section (20) and the plane of which includes an angle of between approximately 40 and approximately 70 with the axis of the pin section (28); and that a first through hole (32) extends through the shaft section (20) and the plate section (22) lying above it, and a second through hole (34) extends through the region of the plate section (22) projecting beyond the shaft section (20) ) extends.

2. Prosthesis part according to claim 1, characterized gekennzeich¬ net that the shaft portion (20) has the shape of a substantially quadrangular transverse cross-section having a truncated pyramid.

3. prosthesis part according to claim 2, characterized gekennzeich¬ net that the pyramid is twisted about its longitudinal axis.

4. Prosthesis part according to one of claims 1-3, characterized in that the plate section (22) projects over the shaft section (20) by about 3-8 mm, preferably between about 4 and about 6.

5. prosthesis part according to any one of claims 1-4, characterized characterized in that the plate section (22) has a side section (26) which is tilted upwards out of the plane of a main plate section (24), preferably by an angle corresponding to the angle of attack of the pin section (28).

6. prosthesis part according to any one of claims 1-5, characterized in that the first through hole

(32) opens out into the lower end face of the shaft section (20).

7. prosthesis part according to any one of claims 1-6, characterized in that from the first through hole

(32) branch bores (66) with a radial extension component, which open into the lateral surface of the shaft section (20).

8. prosthesis part according to claim 7, characterized in that the branch bores (66) are offset from one another in the axial direction and in the circumferential direction, in particular along one or more helix lines (68) are distributed over the shaft portion (20).

9. prosthesis part according to one of claims 1-8, characterized in that an elastically deformable centering part (48) is provided on the free end of the shaft portion (20).

10. Prosthesis part according to claim 9, characterized in that the centering part (48) has a plurality in

Has circumferentially distributed convex spring fingers (52).

11. Prosthesis part according to claim 10, characterized in that the spring fingers (52) from a hub section (50) are worn, which is attached to a bearing surface (46) of the shaft section (20).

12. Material kit for use in cementing a prosthetic part according to one of the claims

1-11, characterized by a first volume of liquid hardenable cement (56) and a second volume of pasty hardenable sealing compound, the hardening time of the sealing compound being longer than that of the cement (56).

13. Material kit according to claim 12, characterized gekennzeich¬ net that the sealing compound (58) has similar basic chemistry as the cement (56), but is provided with at least one additive, through which it receives pasty consistency.

14. Material kit according to claim 12 or 13, characterized gekennz¬ eichnet that the cement (56) is contained in a dispenser (40) which - optionally via a line (38) - with the free end of the first through hole (32) is.

15. Material kit according to claim 14, characterized in that the dispenser (40) or the line (42) connected to it has a truncated cone-shaped coupling piece (70), which in a tapered end portion (72 ) the first through hole (32) can be used in a frictional manner.

16. Material kit according to claim 15, characterized gekennzeich¬ net that the coupling piece (70) is made of a material on which the cement adheres poorly.