Wrist arthrodesis plate and method using a wrist arthrodesis plate

Abstract

A wrist arthrodesis plate (20) consisting of a distal region (21) and of a proximal region (22) which adjoins the distal region (21) in the direction of a longitudinal axis (A). The plate (20) is of such a shape and size that the distal region (21) of the plate can be fastened to the carpus (1) and a proximal region (22) of the plate can be fastened to the radius (3) by fastening devices, such as screws, which can be inserted into plate holes. A distal end region (29), which comprises a farthest distal location (23) of the plate (20), is of a shape and size that the distal end region (29) can be placed with the farthest distal location (23) exactly, and only, on a carpal bone from the group comprising trapezium (11), trapezoid (10), capitate (9) and hamate (8), without covering any part of the laterally adjacent bones.

Claims

1. A wrist arthrodesis plate for fusion between carpal bones and radius, the carpal bones consisting of a distal row of carpal bones and a proximal row of carpal bones, the distal row of carpal bones being formed by an os trapezium, an os trapezoideum, an os capitatum and an os hamatume and the proximal row of carpal bones being formed by an os scaphoideum, an os lunatum and an os triquetrum, said plate defining a longitudinal axis and consisting of a distal region and of a proximal region, wherein the distal region and the proximal region directly and axially adjoin each other in a direction of the longitudinal axis, the plate is fastenable to at most two carpal bones lying in a longitudinal direction and not a metacarpal bone, the plate being of such a shape and size that the distal region is fastenable to a carpus and the proximal region is fastenable to a radius with the aid of fastening means, which are inserted into plate holes formed in the distal region and in the proximal region, wherein the distal region has (i) a distal end region which comprises a distal-most location of the plate and (ii) a substantially constant width, the distal region being of such a shape and size that (i) a first area of the distal end region is fastenable to precisely one bone of the distal row of carpal bones, without covering parts of laterally adjacent bones of the distal row of carpal bones, (ii) a second area of the distal region is placeable on or over only one bone of the proximal row of carpal bones, and (iii) the second area of the distal region is fastenable at most to the bone of the proximal row of carpal bones on or over which it is placeable.

2. The plate as claimed in claim 1, wherein the distal-most location has a maximum width, which corresponds approximately to the maximum width of a human capitate.

3. The plate as claimed in claim 1, wherein the distal region has a width of 10 mm to 15 mm.

4. The plate as claimed in claim 1, wherein the distal region has a length of 15 mm to 30 mm.

5. The plate as claimed in claim 1, wherein a distal-most plate hole of the proximal region is at a distance of at most 20 mm to 35 mm from the distal-most location of the plate.

6. The plate as claimed in claim 1, wherein the plate has a length, along the longitudinal axis, in the range of 55 to 85 mm.

7. The plate as claimed in claim 1, wherein the proximal region has a length of 35 to 60 mm.

8. The plate as claimed in claim 1, wherein the plate extends in the longitudinal direction at least in a first surface or with a first tangent along the longitudinal axis and extends in a second surface or second tangent, at an angle to the first surface or first tangent, along the longitudinal axis.

9. The plate as claimed in claim 8, wherein the angle between the second surface or the second tangent and the first surface or first tangent is about 45°, and/or the second surface extends by a length of 7.5 mm to 8.5 mm.

10. The plate as claimed in claim 9, wherein the plate, after the second surface, extends in a proximal direction in a third surface or a third tangent along the longitudinal axis.

11. The plate as claimed in claim 9, wherein the plate, after the second surface or after the third surface, transitions in the proximal direction in a fourth surface or along a fourth tangent into the first surface.

12. The plate as claimed in claim 1, wherein the plate extends in the longitudinal direction in a third surface at a distance from the first surface and substantially parallel thereto.

13. The plate as claimed in claim 1, wherein the proximal region of the plate has a maximum width of 8 to 20 mm.

14. The plate as claimed in claim 1, wherein the distal region, at an angle range of +/−45° to a perpendicular to the longitudinal axis, has a maximum of four plate holes for fastening the plate to the precisely one bone of the distal row of carpal bones.

15. The plate as claimed in claim 1, wherein the distal end region has a maximum of six plate holes for receiving a bone screw for fastening the plate to the precisely one bone of the distal row of carpal bones.

16. The plate as claimed in claim 1, wherein the plate contains titanium or consists of titanium.

17. A method using a wrist arthrodesis plate according to claim 1 for fusion between carpal bones and radius, the method comprising: fastening the proximal region of the plate to one of the radius and a carpal bone of the proximal row, and fastening the distal region of the plate to precisely one carpal bone of the distal row of carpal bones.

18. The method as claimed in claim 17, wherein the distal region is fastened to the carpal bone of the distal row of carpal bones with a maximum of four screws.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further aspects of the invention can be gathered from the following figures, schematically showing:

(2) FIG. 1 the anatomy around the wrist,

(3) FIG. 2 a wrist arthrodesis plate according to the invention,

(4) FIG. 3a a side view of a first wrist arthrodesis plate according to the invention,

(5) FIG. 3b a plan view of the plate according to FIG. 3a,

(6) FIG. 4a a side view of an alternative embodiment of a wrist arthrodesis plate according to the invention, and

(7) FIG. 4b a plan view of the plate according to FIG. 4a.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) FIG. 1 shows a schematic representation of the anatomy around the wrist. In the proximal direction P, the carpus 1 adjoins the radius 3 and ulna 4. Distally D from the carpus lies the metacarpus 2. The carpus 1 has the bones os triquetrum 5, os lunatum 6 and os scaphoideum 7. Distally D from the three carpal bones 5, 6, 7 lie the carpal bones os hamatum 8, os capitatum 9, os trapezoideum 10 and os trapezium 11. A distal end region 29 with the distal-most location 23 of the wrist arthrodesis plate 20 according to the invention (see FIG. 2) can be placed on a single one of the four carpal bones os hamatum 8, os capitatum 9, os trapezoideum 10 and os trapezium 11. The bone plate does not extend to the metacarpus 2. Between the proximal region 22 and the distal locations 23, the plate can lie over or on one of the further bones, i.e. os triquetrum 5, os lunatum 6 or os scaphoideum 7, but without being fastened thereto.

(9) FIG. 2 shows a bone plate 20 according to the invention in the intended position of use. The plate 20 is produced from pure titanium or a titanium alloy and has a longitudinal axis A. Along the longitudinal axis A, the plate has a length L of about 55 mm to 85 mm (see also FIGS. 3a/3b and 4a/4b).

(10) The plate 20 is composed of a distal region 21 and of a proximal region 22, which adjoins the latter in the proximal direction P. Depending on the nature of the treatment, the distal region 21 has a length of 16 mm to 28 mm along the longitudinal axis A. The proximal region 22 has a length of ca. 40 mm to 50 mm along the longitudinal axis A.

(11) The proximal region 22 of the plate 20 lies on the radius 3 and can be fastened thereto. The distal region 21 lies on the carpus 1 and can be fastened thereto. The distal end region 29 has six plate holes 24 (only labeled once, for clarity). With screws (not shown), the distal end region 29 can be fastened via the plate holes 24 to a single carpal bone from the group os hamatum 8, os capitatum 9, os trapezoideum 10 and os trapezium 11 (see FIG. 1), without laterally adjacent bones being covered. The proximal region 22 has a plurality of plate holes, specifically five round holes 25, 25′ (only labeled once, for clarity) and an oblong hole 26 for fastening the proximal region with screws (not shown) to the radius 3.

(12) The distal region 21 of the plate therefore extends across the carpus 1. However, the distal end region 29 lies on only one of the carpal bones 8, 9, 10, 11 and is also fastened only to said one carpal bone 8, 9, 10, 11. No region of the plate is fastened to the metacarpus 2 or touches the latter.

(13) The distal region 21 has a saddle-shaped depression 27. On account of the depression 27, the plate 20 extends, at the more distal end of the distal end region 29, at an angle of about 10° with respect to a more proximal region of the distal end region 29. The wearing comfort of the plate 20 is increased by this depression 27.

(14) In the proximal region 22, the plate 20 has its widest location with a width b2 of about 13.5 mm. The distal region has a maximum width b1 of about 13.5 mm as well. The widths b1, b2 are measured on a path, perpendicular to the longitudinal axis, between the lateral-most locations, or their projections on an axis parallel to the longitudinal axis A.

(15) Depending on the nature of the treatment, the distance l1 from the distal-most plate hole 25′ of the proximal region 22 to the distal-most end 23 is about 25 mm (see the following description of a short plate in FIGS. 4a and 4b) or 31 mm (see the following description of a long plate in FIGS. 3a and 3b). For reasons of clarity, the length l1 has been indicated outside the plate. The length l1 is measured on a direct path from a center of the distal-most plate hole 25′ of the proximal region 22 to the distal-most location 23 of the plate 20.

(16) FIG. 3a shows a first embodiment of a plate 20 according to the invention in a side view. This plate is intended for treatment preserving the proximal row of the carpal bones or for treatment of large patients following a proximal row carpectomy. In the proximal portion 22, with a length 13 of ca. 43 mm, the plate extends in a first surface 30.

(17) Viewed in the proximal direction P from the distal-most end 23, the plate 20 extends in the distal region 21 first in a second surface 31 extending at an angle α with respect to the surface 30. Still in the distal region, the plate then extends in a third surface 32, which is approximately parallel to the first surface 30. By way of a fourth surface 33, the plate transitions from the third surface 32 into the first surface 30. The bend between the fourth surface 33 and the first surface 30 typically also defines the delimitation between the proximal region 22, which can be placed on the radius, and the distal region 21. In the shown embodiment, the length 12 of the distal portion 21 measures 18-22 mm.

(18) In FIG. 3a, the angle α between the second surface 31 and the third surface 32 is about 45°, and the angle β between the third surface 32 and the fourth surface 33 and the angle γ between the fourth surface 33 and the first surface 30 are about 35°.

(19) In the specific example, the first surface 30 and the third surface 32 in FIG. 3a are approximately parallel to each other. However, it is also conceivable to provide a small angle between first surface 30 and third surface 32, for example an angle of up to 10°.

(20) FIG. 3b shows a top view of the plate of FIG. 3a. Identical reference signs denote the same parts. FIG. 3b additionally shows the various holes, in particular plate holes 24 (in the distal region 21) and 25, 25′ (in the proximal region 22) for receiving bone screws, a plate hole in the form of an oblong hole 26, and a hole 28 for receiving a K wire. In the proximal region, the plate has a maximum width b2 of about 13.5 mm and tapers in the proximal direction P. In the distal region 21, the plate has a substantially constant width b1, likewise of about 13.5 mm.

(21) FIGS. 4a and 4b show, analogously to FIGS. 3a and 3b, an alternative embodiment of a plate according to the invention, this plate being suitable for treating a normal-sized hand following a proximal row carpectomy or also for treating a small hand without this intervention. Accordingly, the third surface 32 shown in FIG. 3a is absent: instead, the plate according to the invention shown in FIGS. 4a and 4b transitions directly from the second surface 31 to the fourth surface 33. Accordingly, the length 12 of the distal portion 21 according to FIG. 4a is shorter than in FIG. 3a and typically measures 17 mm. By contrast, the length 13 of the proximal portion 22 is about the same in both embodiments. In the embodiment according to FIG. 4a, the second surface 31 transitions in a gentle radius into the fourth surface 33. The angle position of the second surface 31 and of the third surface 33 with respect to each other and the angle position with respect to the first surface 30 correspond approximately to the angle positions according to the embodiment in FIG. 3a.

(22) The distance of the distal-most plate hole 25′ of the proximal part 22 (designated l1 in FIGS. 3b and 4b) from the distal-most end 23 typically measures 25 mm (FIG. 3a) or 17 mm (FIG. 4a).

(23) The lengths of the second, third and fourth surfaces typically measure between 7.5 mm and 10.0 mm. In the specific embodiment, the length of the second surface measures about 8.0 mm, the length of the third surface about 8.7 mm, and the length of the fourth surface about 9.3 mm.