ZA200506742B

ZA200506742B - Cutting and forming device

Info

Publication number: ZA200506742B
Application number: ZA200506742A
Authority: ZA
Inventors: Romano Mark-Matthys; Hans Gelpke
Original assignee: Synthes Ag
Priority date: 2005-08-23
Filing date: 2005-08-23
Publication date: 2006-05-31

Description

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English translation of the International Patent Application No. PCT/CH2003/000183 "Cutting and forming device” in the name of Synthes AG Chur any CUTTING AND FORMING DEVICE

The invention relates to a device for cutting a wire and, at the same time, forming a sleeve for protecting the end of the wire in accordance with the introductory portion of claim 1.

Kirschner wires or similar fixation elements frequently are used, for example, when conducting a surgical intervention or for stabilizing bones or bone fragments by means of an external fixator. Depending on the application, these must be brought to a desired length after they are fixed at the bone or at the bone fragment. Kirschner wires or fixation elements are severed with wire cutting tools in order to shorten them.

US patent 4,051,596 of HOFMANN discloses a wire cutting tool with two concentric sleeves, which can be rotated within one another. This known device comprises cutting edges, which are concentric with the longitudinal axis of the sleeves. It is a disadvantage of these known wire cutting devices that, when used during a surgical intervention, the portion of the Kirschner wire, remaining at the bone or bone fragment, is squeezed after it is severed at the place of cutting and has a bur or sharp edges or pointed ends are formed, so that irritations may be produced by the Kirschner wire at the adjoining soft parts.

The invention is to provide a remedy here. It is an object of the invention to provide a device, which, by means of a cutting edge, which can be moved circularly about the Kirschner wire, a bur-free cut through the Kirschner wire or other fixation element, which is to be severed, is made possible. At the same time. it permits a protective sleeve to be pressed onto the end of the severed

Kirschner wire.

Pursuant to the invention, this object is accomplished with a device for cutting a wire and simultaneously forming a protective sleeve for the end of the wire, the device having the distinguishing features of claim 1.

The advantages, achieved by the invention, are seen essentially therein that, due to the inventive cutting device a) a bur-free severing of a Kirschner wire or of a different fixation element becomes possible, b) no sharp edges or pointed ends are formed during the severing process and

Cc) because the Kirschner wire is guided in a borehole, a severing surface, perpendicular to the longitudinal axis, can be produced and the rear end of the Kirschner wire may be provided with a protective sleeve without any refinishing, such as the removal of sharp edges or pointed ends.

In a preferred embodiment, the two sleeves are configured in such a way, that the borehole in the inner sleeve serves to accommodate a guiding or

Kirschner wire and has a diameter d and the constriction of the borehole in the outer sleeve serves to accommodate a sleeve to protect the end of the wire and has a diameter D, D being greater than d. Due to this configuration of the borehole in the inner sleeve, it can be achieved that a circular cutting edge, surrounding the guiding wire, is formed at the front end of the inner sleeve, while the sleeve, protecting the end of the wire, is held fast radially in the outer sleeve by the configuration of the constriction, so that a second circular cutting edge, surrounding a guiding while, is formed at the inner end of the sleeve, protecting the end of the wire, by the wall of the central borehole of the sleeve, protecting the end of the wire.

In a further embodiment, the distances “a” and “b” are such, that "a" is greater than 'b". Due to the different eccentricities of the borehole in the inner sleeve and the constriction, a guide wire can be severed by rotating the inner sleeve relative to the outer sleeve and, at the same time, the sleeve, protecting the end of the wire, can be squeezed onto the end of the guiding wire.

In yet a further embodiment, at least one of these sleeves is equipped at its rear end with an actuating lever disposed transversely to the borehole axis at its rear end, as a result of which greater shear forces can be exerted on the guiding wire.

In a different embodiment of the inventive device, the latter additionally comprises a sleeve, protecting the end of the wire, with a rear end, a front end and a central borehole. The sleeve, protecting the end of the wire, can be pushed parallel to the longitudinal axis into the constriction and the rear end of the sleeve, protecting the end of the wire, can be brought axially to contact the front end of the inner sleeve. Furthermore, the central borehole of the sleeve, protecting the front end of the wire, is provided at the rear end with a cutting edge, which is concentric with the central borehole. Since the longitudinal axis of the constriction and the axis of the borehole in the interior sleeve as disposed eccentrically to the axis of rotation of the inner sleeve, which is formed by the longitudinal axis of the circularly cylindrical inner sleeve coinciding with the borehole axis in the outer sleeve, the Kirschner wire is sheared off between the first and second cutting edges when the inner sleeve is rotated relative to the outer sleeve.

With that, the further advantage can be achieved that, in the event that the sleeve, protecting the end of the wire, is not used, the guiding wire cannot be severed. Accordingly, the additional security can be attained that the guiding wire can be shortened only when the sleeve, protecting the end of the wire, is inserted in the device.

In a further embodiment, the inventive device comprises a housing with a central axis and a cavity, in which the two sleeves can be accommodated and which passes through the housing coaxially to the central axis. Furthermore, the cavity at the front end of the housing has a borehole with a longitudinal axis, which is parallel to the central axis of the housing, from which it is removed by a distance c.

The diameter of this borehole corresponds to the external diameter of the sleeve, protecting the end of the wire, so that a compressed fit connection can be established between the sleeve, protecting the end of the wire, and the Kirschner wire by rotating the outer sleeve in the cavity of the housing.

In yet another embodiment of the inventive device, one of the sleeves includes a catch and the other sleeve a recess, the catch being freely movable about an angle of rotation a within the recess when the sleeves are rotated relative to one another. The angle of rotation a preferably ranges from 90° to 180°. With that, it can be achieved that, at the end of the cutting process, the catch and the stop surface lie against one another in the recess, so that the two sleeves cannot be rotated further relative to one another but can be rotated together relative to the housing. The pressing process between the sleeve, protecting the end of the wire, and the Kirschner wire, can then be carried out by rotating the two sleeves relative to the housing.

The eccentricities a, b and c preferably fall within the following ranges: - eccentricity a between 0.2 mm and 0.8 mm, - eccentricity b between 0.2 mm and 0.8 mm and - eccentricity ¢ between 0.05 mm and 0.4 mm.

In a different embodiment of the inventive cutting device, a shoulder with a flat supporting surface, which is at right angles to the axis of the borehole, is formed by the constriction in the borehole in the outer sleeve, so that the front end of the inner sleeve can be bought to rest on this supporting surface. By means of this configuration, it can be achieved that a first circular cutting surface can be produced at the outlet of the borehole in the inner sleeve and a second, circular cutting edge, concentric with the longitudinal axis of the constriction, can be produced at the transition of the supporting surface to the constriction in the outer sleeve. Because of the eccentricity of the axis of the borehole in the interior of the sleeve and the a. longitudinal axis of the constriction, the Kirschner wire can be sheared off by rotating the two sleeves relative to one another.

The invention and further developments of the invention are explained in even greater detail by means of the partially diagrammatic representations of several examples. In the drawing

Fig. 1 shows a longitudinal section through an embodiment of the inventive device,

Fig. 2 shows a section B-B through the embodiment of the inventive device, shown in Fig. 1,

Fig. 3 shows a view from A of the embodiment of the inventive device, shown in Fig. 1, with sleeves and housing positioned for introducing the sleeve, protecting the end of the wire, and the Kirschner wire,

Fig. 4 shows a view from A of the embodiment of the inventive device, shown in Fig. 1, with sleeves rotated relative to one another and

Fig. 5 shows a view from A of the embodiment of the inventive device, shown in Fig. 1, after the sleeves are twisted relative to one another and with respect to the housing.

An embodiment of the inventive device 1 is shown in Fig. 1. It comprises a hollow cylindrical housing 5 with a cavity 8, having a longitudinal axis 2, as well as two sleeves 3; 4, which are disposed in the cavity 8 in such a manner, that they can be rotated about the longitudinal axis 2. The outer sleeve 4, having a longitudinal axis 28, is developed with an eccentric borehole 14, which has an axis 9 and passes longitudinally through the sleeve 4. The inner sleeve 3 is mounted in this borehole 14 so that it can be rotated coaxially about the borehole axis 9. On the outside, the outer sleeve 4 is configured circularly cylindrically and concentrically with the longitudinal axis 28. On the outside, the inner sleeve 3 is configured circularly cylindrically and coaxially with the borehole axis 9 and has a borehole 12 with an axis 13, which is eccentric with respect to the borehole axis 9. This borehole 12 accommodates a Kirschner wire 20 or a different fixation element. At the front end 18 of the outer sleeve 4, the borehole 14 has a constriction 17, as a result of which a supporting surface 23, on which the front end 19 of the inner sleeve 3 can be brought to rest, is formed perpendicularly to the axis 9 of the borehole 14.

The first cutting edge 15 is formed by the circular line-shaped, sharp edged border at the outlet of the borehole 12 at the front end 19 of the inner sleeve 3. In the embodiment of the inventive device, shown here, a sleeve 24 for protecting the end of the wire is introduced into the constriction 17 in the outer sleeve 4. The sleeve 24, which protects the end of the wire, is configured with a central borehole 34 for accommodating a Kirschner wire, the ends of the central borehole 30 having a sharp edge. By these means, a second cutting edge 16, which is directed against the first cutting edge 15, is formed at the end of the sleeve 24, which protects the end of the wire.

Due to the eccentricity “a” of the axis 9 of the borehole 14, which accommodates the inner sleeve 3, with respect to the longitudinal axis 2, and the eccentricity “b” of the axis 13 of the borehole 12, which accommodates the Kirschner wire 20, and of the borehole axis 9, the inner sleeve 3 can be brought into a rotative position relative to the outer sleeve 4, in which the borehole 12 is aligned with the central borehole 30 in the sleeve 20 for protecting the end of the wire. In this position of the inner sleeve 3 (Fig. 3), the Kirschner wire 20 can be introduced through the central borehole 30 in the sleeve 24, which protects the end of the wire, into the borehole 12 in the inner sleeve 3.

By twisting the two sleeves 3; 4 relative to one another (Figs. 4 and 5), the Kirschner wire 20 is severed by means of the shearing motion between the cutting edges 15; 16, caused by the rotation of the latter eccentrically to one another.

For operating the two cutting elements 3; 4, a handrail 6 is disposed perpendicularly to the longitudinal axis 9 of the cavity at the rear end 27 of the housing 5 and a lever 7 is mounted also perpendicularly to the longitudinal axis 9 of the cavity at each rear end 21 of the inner sleeve 3.

Aside from cutting the Kirschner wire 20, a sleeve 24, protecting the end of the wire, can be fastened to the rear end of the Kirschner wire 20 in the same step with the embodiment of the inventive device 1 shown in Figs. 1 to 5. The fasting is accomplished by pressing the side wall 32 of the sleeve 24 protecting the end of the wire, against the Kirschner wire 20 by means of the eccentric arrangement of the constriction 17 at the outer sleeve 4 and the borehole 25 at the front and 26 of the housing 5. Due to the configuration of the eccentricities a, b and c with the condition that a — b = ¢ (Fig. 3), it can be achieved that, in the relative position of the inner sleeve 3, the outer sleeve 4 and the housing 5, shown in Fig. 3, the sleeve 24, protecting the end of the wire, can be introduced into the borehole 25 at the front end 26 of a housing 5 and into the constriction 17 at the front end 19 of the outer sleeve 4 coaxially with the axis 13 of the borehole 12 and the Kirschner wire 20 can be introduced through the central borehole 30 of the sleeve 24, protecting the end of the wire, coaxially with the borehole axis 13 into the borehole 12. The position, shown in Fig. 3, is distinguished owing to the fact that the inner sleeve and the outer sleeve 4 are positioned so that the three eccentricities a, b and c lie on a straight-line and fulfill the condition a = b + ¢ (Fig. 3).

At its rear end 22, the outer sleeve 4 is constructed as a half shell, so that a recess 35 with two stop surfaces 37, parallel to the longitudinal axis 2, is formed at the rear end 22 of the outer sleeve 4. A catch 10, protruding radially at the rear end 22 of the inner sleeve 3, comes to rest at an angle of rotation between the inner and outer sleeves 3; 4 of 135° at one of these stop surfaces 37, so that, upon further rotation of the actuating lever 7 relative to the handrail 6, the two sleeves 3; 4 are rotated relative to the housing 5 (Fig. 5), as a result of which the constriction 17, together with the sieeve 24, protecting the end of the wire and introduced into the constriction 17, is rotated in the housing 5 with respect to the borehole 25. Due to the eccentric arrangement of the axis 29 of the borehole 25 relative to the longitudinal axis 11 of the constriction 17, the sleeve 24, protecting the end of the wire, is squeezed by the walls of the borehole 25 and of the constriction 17 and fixed on the Kirschner wire 20 introduced into the central borehole 30 of the sleeve 24 protecting the end of the wire.

Claims

1. Device (1) for cutting a wire and, at the same time, forming a sleeve for protecting the end of the wire with A) an outer sleeve (4), which has a longitudinal axis (28) and comprises a front end (18), a rear end (22) and a borehole (14) having an axis (9) and passing longitudinally through the sleeve (4) and B) an inner sleeve (3), which can be rotated in the borehole (14) coaxially to the axis (9) of the borehole (14) and comprises a front end (19), a rear end (21) and a borehole (12) having an axis (13) passing through the sleeve (3) longitudinally, characterized in that C) the wall of the borehole (12), at the front end (19) of the inner sleeve (3) has a circular cutting edge (15), which is concentric with the borehole axis (13); D) the borehole (14), at the front end (18) of the outer sleeve (4), has a constriction (17), the longitudinal axis (11) of which is parallel to the borehole axis (9) and is at a distance a > 0 from the latter; and E) the axis (13) of the borehole (12) extends parallel to the axis (9) of the borehole (14) at a distance b > 0 therefrom.

2. The device of claim 1, characterized in that a) the borehole (12) in the inner sleeve (3) accommodates a guiding or Kirschner wire (20) and has a diameter d, b) the constriction (17) accommodates a sleeve (24), protecting the end of the wire, and has a diameter D, d) D being greater than d.

3. The device of claims 1 or 2, characterized in that a > b.

4. The device of one of the claims 1 to 3, characterized in that at least one of the sleeves (3; 4) is equipped at its rear end (21; 22) with an actuating lever (7), which is disposed transversely to the borehole axes (9; 13).

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5. The device of one of the claims 1 to 4, characterized in that it additionally comprises a sleeve (24) for protecting the end of the wire, with a rear end (33), a front end (34) and a central borehole (30).

6. The device of one of the claims 1 to 5, characterized in that a shoulder (31) with a flat supporting surface (23), perpendicular to the borehole axis (9), is formed by the constriction (17) and the front end (19) of the inner sleeve (3) rests on this supporting surface (23).

7. The device of claims 5 or 6, characterized in that the sleeve (24), which protects the end of the wire, can be pushed parallel to the longitudinal axis (11) into the constriction (17) and the rear end (33) of the sleeve (24), which protects the end of the wire, can be brought axially into contact with the front end (19) of the inner sleeve (3).

8. The device of one of the claims 5 to 7, characterized in that the walls of the central borehole (30) in the sleeve (24), protecting the end of the wire, has at the rear end (33) a central borehole (30), which embraces the second cutting edge (16) concentrically.

9. The device of one of the claims 1 to 8, characterized in that it comprises a housing (5) with a central axis (2), a front end (26), a rear end (27) and a cavity (8), which accommodates the outer sleeve (4) and passes through the housing (5) parallel to the central axis (2).

10. The device of claim 9, characterized in that the cavity (8) at the front end (26) of the housing (5) comprises a borehole (25) with a longitudinal axis (29), which is parallel to the central axis (2) at a distance ¢ > 0 from the latter.

11. The device of claim 10, characterized in that the diameter of the borehole (29) corresponds to the external diameter of the sleeve (24) protecting the end of the wire, so that a compression connection may be produced between the sleeve (29), protecting the end of the wire, and the wire (20) by rotating the outer sleeve (4) in the cavity (8).

12. The device of one of the claims 1 to 11, characterized in that the actuating lever (7) may be fastened at the rear end (21) of the inner sleeve (3).

13. The device of claim 12, characterized in that one of the sleeves (3; 4) surrounds a catch (10) and the other sleeve (3; 4) a recess (35), the catch (10) being freely movable about an angle of rotation a within the recess (35) when the sleeves (3; 4) are rotated relative to one another.

14. The cutting device of claim 13, characterized in that the angle of rotation « ranges from 90° to 180°.

15. The device of one of the claims 1 to 14, characterized in that the borehole axis (13) is at a distance “a”, which is between 0.2 mm and 0.8 mm, from the longitudinal axis (11).

16. The device of claim 15, characterized in that the distance “a” is between 0.4 mm and 0.6 mm.

17. The device of one of the claims 1 to 16, characterized in that the longitudinal axis (2) of the constriction (17) is at a distance b, which is between 0.2 mm and 0.8 mm, from the longitudinal axis (11).

18. Cutting device of one of the claims 10 to 17, characterized in that the distance c is between 0.05 mm and 0.5 mm.

19. The cutting device of claim 18, characterized in that the distance ¢ is between 0.1 mm and 0.3 mm.