DE29500476U1 - Prosthetic wrist - Google Patents

Description

Implant-Service GmbH, Oehleckerring 14A, 22419 Hamburg

Wrist prosthesis

The invention relates to a wrist prosthesis which is to be implanted as a replacement for the natural wrist in the case of a corresponding clinical picture. The present invention is based on the object of creating a wrist prosthesis by means of which, after its implantation, the movement sequence of the wrist can be at least essentially completely restored, i.e. not only swiveling forwards and backwards, but also movement of the outstretched hand to the left and right, whereby, in addition - with little wear in the actual joint part - a long service life should be achieved.

The solution to this problem is characterized in accordance with the invention by a carpus element with three essentially

533/32

Bremen:

Hollerallec 32, D-2S209 Bremen
Pustf. 10 71 27. D-2UO71 Bremen

Telephone (04 21)3 40 90
leietox (04 21)3 49 17 68
Telex 244 95Hbopntd

Berlin:

Uhlandstroßc 173/174 D. 10719 Berlin

Telephone (0 30) 8 Bl IO 3ft Fax (ü 30) S Sl 39 Telex 183 661 fruno ti

Kiel:

Nienumnsweg

Telephone (04 31) K 40 Fax [04 3 3)8 40

BOEHMERT & BOEHMERT, NÜRHEMANN and PARiTNEit

a plane arranged, peg-shaped projections, which extend from the top of an integral plate-shaped section at a mutual distance essentially vertically upwards, and with a substantially cylindrical bearing pin, which projects over a connecting section approximately centrally from the top of the plate-shaped section, runs transversely to the peg-shaped projections, the longitudinal axis of which lies essentially in the plane as the longitudinal axes of the peg-shaped projections, and which is pivotably mounted about its longitudinal axis in a cylindrical bearing bore of a sliding element, which has on its top a slot extending to a side surface for inserting the connecting section, as well as by a radial element with a conical shaft to be implanted in a forearm bone, which has on its upper end section facing away from the shaft a concave bearing shell forming an articular surface for receiving the sliding element, the underside of which facing the articular surface of the articular surface of the Bearing shell corresponds .

The concave bearing shell is preferably essentially oval, as will be explained below using an example, and supports the carpus element with its bearing pin via the sliding element in such a way that in the implanted, healed state not only a hinge movement of the hand in question forwards and backwards is possible, but also a lateral pivoting to the left and right.

For optimal adaptation to the anatomical conditions, the bearing pin, which extends over its

BOEHMERT & BOEHMERT,

connecting section below the middle pin-shaped attachment is integrally connected to the plate-shaped section, not at right angles to the longitudinal axis of the middle pin-shaped attachment, but its longitudinal axis preferably runs at an acute angle to the plate-shaped section, so that the bearing pin is thus pivoted laterally to the plate-shaped section. In a corresponding manner, the vertical axis of symmetry of the essentially symmetrical bearing shell preferably runs at the same acute angle to the longitudinal axis of the shaft, so that the sliding element in the implanted state is received essentially centrally by the bearing shell with the hand extended and can slide in it when the hand is pivoted sideways to the left or right.

At least one sliding surface of the elements, which are usually made of a tissue-compatible metal, is preferably provided with a titanium-niobium coating, since two metal surfaces obviously slide against each other and, accordingly, good sliding properties with low abrasion must be ensured.

Further preferred embodiments of the present invention are described in the subclaims.

The invention is explained in more detail below using an embodiment with reference to a drawing. It shows:

Fig. 1 is a side view of the carpus element of a wrist prosthesis according to the invention;

BOEHMERT & BOEHMERT, &Ngr;&phgr;^^&Mgr;&Agr;&Igr;^ yjp PARTÜtER

Fig. 2 shows a section through the carpus element according to Fig. 1, seen in the direction of the section line II-II,-

Fig. 3 a side view of the radial element of the wrist prosthesis;

Fig. 4 is a side view of the radial element according to Fig. 3, seen in the direction of arrow IV in Fig. 3;

Fig. 5 is a top plan view of the radial element according to Figs. 3 and 4, seen in the direction of arrow V in Fig. 3;

Fig. 6 shows a section through the radial element according to Figs. 3 to 5, seen in the direction of the section line VI-VI in Fig. 3;

Fig. 7 is an exploded view of the wrist prosthesis; and

Fig. 8 is a somewhat simplified schematic representation of the implanted wrist.

Figures 1 and 2 show an exemplary embodiment of the carpus element 2 of a wrist prosthesis designated as a whole by 1 (see Figure 7). The carpus element 2 has three peg-shaped projections 3, 4 and 5 arranged in a plane, which extend vertically upwards from the upper side 6 of an integral plate-shaped section 7 at a mutual distance a.

Furthermore, it is provided with an integral bearing pin 8, which is connected via a connecting section 9 approximately centrally

BOEHAiERT & BOEHMERT, CORPORATE PARTNERSHIP

protrudes from the underside 10 of the plate-shaped section 7. The cylindrical bearing pin 8, which runs transversely to the pin-shaped projections 3-5, is arranged such that its longitudinal axis 11 lies in the same plane as the longitudinal axes 12-14 of the pin-shaped projections 3-5. The longitudinal axis 11 of the bearing pin 8 runs at an acute angle α to the plate-shaped section 7, so that the bearing pin 8 does not run at a right angle to the longitudinal axis 12 of the pin-shaped projection 3, but is bent laterally to it.

The bearing pin 8 has a diameter d of 7.7 mm and a length 1 of 17 mm and is mounted in a cylindrical bearing bore 25 of a sliding element 26 (see Fig. 7), which has a slot on its upper side 27 extending to a side surface 28 for the lateral insertion of the connecting element 9. The bearing pin 28 is held in the bearing bore 25 by means of a snap ring 31. The underside 29 of the sliding element 26 is doubly curved and corresponds to the joint surface of a radial element 17, which is described further below.

The two outer peg-shaped projections 4 and 5 are of equal length. Their total length is 15 mm with a diameter of 2.7 mm. The middle peg-shaped projection 3 is about twice as long with a total length of 28 mm. It is provided with a profile consisting of longitudinal grooves 15. Its greatest width e is about 7 mm in both directions.

The two outer pin-shaped projections 4 and 5 are connected to the middle pin-shaped projection 3 via a

BOEHMERT & BOEHMERT, HQRQEMA^IN mi© PARTNER

connected to the cross-section 16 arranged at a distance b from the plate-shaped section. The free end section of the outer peg-shaped projections 4 and 5 protruding upwards over the cross-section 16 is each approximately 5 mm long.

Fig. 3-6 show the radial element of the wrist prosthesis, designated as a whole by 17. It has a conical shaft 19 to be implanted in a forearm bone 18 (see Fig. 8) and at its end

19 facing away from the upper end section a joint surface

20 forming a concave bearing shell 21 for receiving and supporting the sliding element 26, in which the bearing pin 8 of the carpus element 2 is pivotably mounted. In the embodiment shown, the length L at the upper edge is approximately 25 mm and the width B approximately 15 mm with a larger recess depth t of approximately 6 mm. The radius of curvature R of the bearing shell 21 is approximately 16 mm in the longitudinal direction and the radius of curvature r in the direction perpendicular to it is approximately 6 mm, whereby the bearing shell 21 is thus approximately oval. The underside of the sliding element 26 is designed accordingly. The joint surface 20 is provided with a titanium-niobium coating.

In particular, it can be seen from Fig. 3 that the vertical axis of symmetry 22 of the symmetrically designed bearing shell 21 runs at the same acute angle a. to the longitudinal axis 23 of the shaft 19 as the bearing pin 8 of the carpus element 2 to its plate-shaped section 7, so that the bearing pin 8 or the sliding element 26 lies essentially centrally in the bearing shell 21 or on its sliding surface 20 when the hand is extended (see Fig. 7).

BOEHMERT & BOEHMERT, NCFREUSMANKT ui& PARITNtEK

In the implanted state, the radial element 17 of the wrist prosthesis 1 is anchored in the forearm bone 18 in such a way that the upwardly open bearing shell 21 is located in the end section of the bone 18, while the carpus element 2 with its peg-shaped projections 4 and 5 each protrudes into a metacarpal bone and its longer, central peg-shaped projection 3 protrudes into the lower middle finger bone, with the crossbars 16 acting as abutments. The sliding element 26 rests approximately in the middle of the articular surface 20 of the bearing shell 21, so that the hand with the implanted carpus element 2 can be pivoted forwards and backwards in the bearing shell 21, with the connecting section 9 moving into a recess 30 that is provided on both sides of its slot for the connecting element 9. In addition, a lateral pivoting movement to the left and right in the direction of the double arrow 24 is also possible, whereby the bearing pin 8 slides to the left or right in the sliding surface 20 of the bearing shell, so that the natural movement sequence of the wrist can essentially be restored with the wrist prosthesis according to the invention.

BOEHMERT & BOEHMERT, N0&DE$/LVNN

List of reference symbols

1 wrist prosthesis

2 Carpus element

3 cone-shaped attachment

4 cone-shaped attachment

5 cone-shaped attachment

6 Top {of 7)

7 plate-shaped section

8 bearing journals

9 Connection section

10 subpages (of 7)

11 Longitudinal axis (of 8)

12 Longitudinal axis (of 3)

13 Longitudinal axis (of 4)

14 Longitudinal axis (of 5)

15 long sides (of 13)

16 Crossbar

17 Radial element

18 forearm bones

19 shaft

20 Articular surface (of 21) (sliding surface)

21 Bearing shell

22 vertical axis of symmetry (of 21)

23 Longitudinal axis (of 19)

24 Double arrow

25 bearing bore (of 26)

26 Sliding element

27 Top (of 26)

2 8 Side surface (of 26)

29 subpage (of 26)

30 recesses (in 26)

31 Snap ring

Claims (19)

Implant-Service GmbH, Oehleckerring 14A, 22419 Hamburg Wrist prosthesis claims 1. Wrist prosthesis, characterized by a carpus element (2) with three peg-shaped projections (3, 4, 5) arranged essentially in one plane, which extend from the top (6) of an integral plate-shaped section (7) at a mutual distance (a) essentially vertically upwards, and with a cylindrical bearing pin (8) which projects over a connecting section (9) approximately centrally from the bottom (10) of the plate-shaped section (7) and runs transversely to the peg-shaped projections (3-5), the longitudinal axis (11) of which lies essentially in the same plane as the longitudinal axis 533/32 Bremen: Hollcrallee 32, D-28209 Bremen
PO Box 10 71 27, D-28071 Bremen Telephone (04 21) 3 40 10
Fax (04 21) 3 49 17 6K
Telex 244 95« bopat d Berlin: Uhlandsstrasse 173/174 D-10719 Berlin Telephone (0 30) 8 Kl lOjti Fax (0 30)8 8! 39 Telex 183 66! IVojlü d Munich: Leipzig: _>g# l*ni^is*(hj*r*l'e JS**. .*'liiiSpp.RoscntM-SIrafä« 21 Fax (0 Ml 34 70 10
Telex 524 282 turbo d * · .Iclephin (OjIl 11 y 60 2* &bgr;· *
Telrfax (0.3 41)3103 25 Dusseldorf: Neßlerstrasse 5 D-40593 Düsseldorf Telephone (02 ti) 71 Kg HZ Fax (02 11) 7 18 27 50 Kiel: Niemannsweg D 24105 Kiel tolojAun (04 &Iacgr;.\) (4 40 I Fax (04 31)8 40 BOEHMERT & BOEHMERT se (12-14) of the peg-shaped projections (3-5), and which is mounted so as to be pivotable about its longitudinal axis (11) in a cylindrical bearing bore (25) of a sliding element (26), which has on its upper side (27) a slot extending to a side surface (28) for inserting the connecting section (9), and by a radial element (17) with a conical shaft (19) to be implanted in a forearm bone (18), which has on its upper end section facing away from the shaft (19) a concave bearing shell (21) forming an articular surface (20) for receiving the sliding element (26), the underside (29) of which facing the articular surface (20) corresponds to the articular surface (20) of the bearing shell (21). 2. Wrist prosthesis according to claim 1, characterized in that the bearing shell (21) is substantially oval in shape. 3. Wrist prosthesis according to claim 2, characterized in that the bearing shell (21) is approximately 25 mm long and approximately 15 mm wide at its upper edge and has a larger recess depth of approximately 6 mm. 4. Wrist prosthesis according to claim 2 or 3, characterized in that the radius of curvature (R) of the articular surface (20) of the bearing shell (21) in its longitudinal direction is approximately 16 mm and in the direction perpendicular to it approximately 6 mm. 5. Wrist prosthesis according to one or more of the preceding claims, characterized in that the longitudinal BOEHMERT & BOEHMERT, NÖRDEMAMtt uj» PAR-TNBR axis (11) of the bearing pin (8) runs at an acute angle (α) to the plate-shaped section (7). 6. Wrist prosthesis according to claim 5, characterized in that the vertical axis of symmetry (22) of the substantially symmetrical bearing shell (21) runs at the same acute angle (α) to the longitudinal axis (23) of the shaft (19). 7. Wrist prosthesis according to one or more of the preceding claims, characterized in that the bearing pin (8) has a diameter (d) of approximately 8 mm and a length (1) of approximately 15 to 20 mm. 8. Wrist prosthesis according to one or more of the preceding claims, characterized by a metal construction, wherein the sliding surface (20) of the bearing shell (21) and/or the bearing pin (8) is/are provided with a titanium-niobium coating or the like. 9. Wrist prosthesis according to one or more of the preceding claims, characterized in that the peg-shaped projections (3-5) are each tapered at their free end section. 10. Wrist prosthesis according to one or more of the preceding claims, characterized in that the two outer peg-shaped projections (4, 5) are of substantially the same length. 11. Wrist prosthesis according to claim 10, characterized in that the outer peg-shaped projections (4, 5) are approximately 15 mm long. BOEHMERT & BOEHMERT, NjßRQEMAttN uSb PAR ₁ TIiJER 12. Wrist prosthesis according to one or more of the preceding claims, characterized in that the two outer peg-shaped projections (4, 5) are each connected to the middle peg-shaped projection (3) via a transverse web (16) arranged at a distance (b) from the plate-shaped section (7). 13. Wrist prosthesis according to claim 12, characterized in that the free end section of the outer peg-shaped section (4, 5) projecting upwards beyond the crosspiece (16) is approximately 5 mm long. 14. Wrist prosthesis according to one or more of the preceding claims, characterized in that the two outer peg-shaped projections (4, 5) are cylindrical and have a diameter of approximately 3 mm. 15. Wrist prosthesis according to one or more of the preceding claims, characterized in that the central peg-shaped projection (3) is approximately twice as long as the two peg-shaped projections (4, 5). 16. Wrist prosthesis according to one or more of the preceding claims, characterized in that the central peg-shaped projection (3) is approximately 6 to 7 mm wide and deep. 17. Wrist prosthesis according to one or more of the preceding claims, characterized in that the central pin-shaped projection (3) is provided with a longitudinal groove (15) or similar existing profiling. BOEHMERT & BOEHMERT, NORDEMANN is5s PASUTNHR. 18. Wrist prosthesis according to one or more of the preceding claims, characterized in that the bearing bore (25) of the sliding element (26) extends to the insertion side surface (28) of the sliding element (26); and that a snap ring (31) or the like is arranged adjacent to this side surface (28), which holds the bearing pin (18) in the bearing bore (25). 19. Wrist prosthesis according to one or more of the preceding claims, characterized in that the sliding element (26) in the region of the connecting element (9) is provided with a recess (30) for the connecting element (9) on both sides of the slot.