DE4329220A1 - Medical wire-twisting forceps - Google Patents

Abstract

The invention relates to wire-twisting forceps for medical applications which can be used to bend and, where appropriate, cut off wires employed intra-operatively for bone fixation - e.g. Kirschner wires in fracture treatment - at their end projecting from the bone. For this purpose, the wire is fixed in the forceps at its end near the bone and is bent up to 180<o> on continued compression of the handles. Fixation of the wire in the forceps does not result in any forces or moments being applied to the bone, so that loosening or breaking of the wire from the bone is avoided. In different embodiments, the wire can also be cut to the desired length prior to the bending operation.

Description

The invention relates to a wire cutter for medical applications, with the Wires used intraoperatively for bone fixation - e.g. B. Kirschner wires in fracture treatment - at its end protruding from the bone can be bent and possibly cut off without being in the bone significant bending moments, shear or normal forces are initiated.

In wire osteosynthesis in surgical fracture treatment Bone fragments with wires - mostly with so-called "Kirschner" wires ("K-wires") - connected to each other. Often, the bone fragments too e.g. B. in the sense of Zuggurtungssoteosynthese with additional thinner Wires looped around the thicker K-wires and through a borehole through the bone, stabilized (M. E. Müller, M. Allgöwer, R. Schneider (1991) Manual of Internal Fixation. Springer Verlag, Berlin, Heidelberg, New York). Those recommended in the "Manual of Internal Fixation" The wire gauge of the K-wires used for the spiking is for the patella (P. 566) and for the olecranon (p. 460) 1.6 mm. On p. 323 of the "Checklist Traumatology, Heim, U., Baltensweiler, J., Thieme Verlag 1984 "is for the Patellazuggurtostesynthese specified a wire thickness of 1.8 mm. Larger and more stressed bone fragments - e.g. B. Zuggurtungsostesynthesen in Area of the trachanter major at the hip - require even stronger wires, smaller bone fragments and less stressed bone fragments correspondingly thinner. The most common wire sizes are between 1.4-2 mm.

In classic tension belt osteosynthesis, this becomes from the bone protruding end of the K-wire shortened to a certain length and then bent (M. E. Müller, M. Allgöwer, R. Schneider (1991) Manual of Internal fixation. Springer Verlag, Berlin, Heidelberg, New York). Through the It will bend and push the wire end into the bone Migration of the wire in the bone and rotation of the wire around its Longitudinal axis prevented. The K wire in the sense of Tension belt osteosynthesis looped thinner wire becomes a stable abutment offered. There has been a bend in the Bone drilled wire end proven by 180 °, mostly one two turns by 90 ° each is preferred (M. E. Müller, M. Allgöwer, R. Schneider (1991) Manual of Internal Fixation. Springer Verlag, Berlin, Heidelberg, New York). The wire usually follows the Cut about 1.5 cm to 2 cm out of the bone, the first kink then takes place almost 1 cm from the bone border, the second - more distant - Bend the wire almost 5 mm behind the first.  

Usually, side cutters or the like are used to cut the wire. Tools for bending the wire end, bending sleeves and pliers, e.g. B. flat and needle nose pliers.

A disadvantage of such a bending process is that Bending the wire will exert leverage on the bone since especially when turning the wire to 180 ° for the second time Bone protruding wire can no longer be used with a normal flat nose pliers or the like can be held so that as Counterbearing when bending the wire the wire end sunk in the bone serves. The bending moments and shear forces occurring in the bone can undesirable loosening especially in osteoporotic bone of wire in the bone, occasionally even breaking out of the wire lead out of the bone. The desired stability of the wire in the bone can be greatly reduced.

The problem of high stress on the bone bearing of the wire Leverage in the wire bending is in the sense of the invention by a special medical wire cutters loosened, which on the one hand the wire on his Exit point fixed to the bone and in a further step the Wire bends. It then serves as a counter-bearing when bending the wire no longer the wire end sunk in the bone, but the one in the Pliers jaws of the pliers fixed wire so that none when bending the wire Bending moments, transverse or normal forces through the wire on the bone be exercised.

It may be advantageous to use the same medical wire Cut wire cutters to the desired wire length so that the Machining process with the wire cutters takes place in two steps. By doing one step the wire is cut to the appropriate length, in second step bent through an angle of up to 180 °.

It is possible to first fix the wire end protruding from the bone in the jaws of a pair of pliers ( Fig. 6). B. can be secured with a quick release fastener ( 28 ). With the help of the cutting jaws ( 12 ) and ( 26 ) the wire can also be cut to the desired length of just under 2 cm. The wire can then be bent with a separate hand lever. Of course, it is also possible to cut the wire only in this operation, which z. B. can be accomplished by passing the wire past a blade, as shown in another embodiment in Fig. 2.

Of course, wire cutting can be completely dispensed with, so that the pliers only for bending the previously shortened conventionally Wire can be used. In this case, of course, the Cutting jaws.  

However, it is particularly advantageous if the third hand lever is dispensed with and the bending and possibly also cutting process can be accomplished by continuously compressing only two handles. Fig. 1 to Fig. 5 show exemplary embodiments of such a construction, the handle ( 2 ) being omitted from the drawing in Fig. 1 for the sake of clarity, but the design of which corresponds to the handle of Fig. 2.

In the exemplary embodiment in FIG. 1, the wire was not cut off. This machining process (wire fixing and bending without wire cutting) is first described. With such a construction, the wire is packed at its end close to the bone when the initially opened pliers are compressed. There must now be a power transmission to both the jaws and the bending mechanism which ensures that the wire is clamped in the jaws with a greater moment than the moment which acts on the wire to bend the wire. In the embodiment in Fig. 1 this is solved constructively as follows: One of the two jaws is movable as a "counter jaw" ( 7 ) on the handles - z. B. over the central bolt ( 5 ) - stored. When the two hand levers are pressed together, the hand lever ( 2 ) (see Fig. 2) does not act directly on the movably mounted jaw ( 7 ), but via a bending lever ( 3 ), which in turn is movably mounted in the movably mounted jaw. Appropriate dimensions of the lever action of the parts connected to one another can ensure that the torque effective for clamping the wire is greater than the bending moment required for bending the wire and exerted on the wire by the bending lever ( 3 ) (for a calculation see the illustration description for Fig. 1).

The bending of the wire can e.g. B. can be realized by a guide or articulated storage of one or more bending wedges. In the embodiment of Fig. 1 to Fig. 5 the wire is used, a hinge-like manner in the counter jaw (7) mounted Umbiegehebel (3) to bend. Due to the hinge-like mounting of the bending lever and positioning of the bearing relative to the jaw, around which the wire is bent, the wire can be bent by 180 ° with a rotation of the bending lever ( 3 ) of only 90 °.

If the wire is also to be cut off at the same time in such a solution, the wire can be guided past a blade during the bending process, which shortens the wire to the corresponding length, as is shown in the exemplary embodiment in FIG. 2. It is particularly advantageous if a different (greater) force is exerted by the wire bending lever on the K-wire when the wire is cut off. For this purpose, the hand lever ( 2 ) - directly or through a corresponding additional linkage - can act on another point ( 10 ) of the wire bending lever at the beginning of the machining process in order to achieve a more favorable transmission ratio when cutting the wire. A slight disadvantage can arise with this solution in that the movably mounted jaw ( 7 ) cannot securely clamp the wire end when cutting the wire, since the torque required for clamping can possibly be caused by the change in force acting on the wire bending lever by the second hand lever ( 2 ) when cutting the wire is not reached. However, this disadvantage is not very serious, since when the wire is cut off no significant leverage acts on the bone anyway, so that a fixation of the wire end is not absolutely necessary when the wire is cut off.

Instead of leading the wire past a blade, it is also possible to unwind the wire in the sense of a pair of pliers before the bending process. If this is to be released by squeezing only two handles, the force of the handles must be effective in three places: on the clamping jaws, on the wire bending mechanism and on the wire unwinding mechanism. As shown in Fig. 3, this can be done using a movable - e.g. B. in the central bolt ( 5 ) - mounted jaw ( 17 ) can be achieved, with the help of the additional linkage ( 13 ) and ( 14 ) a large force is exerted. The additional linkage also acts on the wire bending lever ( 3 ) and, via this bending lever, also on the counter jaw ( 7 ), so that when the wire is bent over after it has been pinched off, it can then be securely fixed in the jaws ( 7 ) and ( 8 ). The auxiliary linkage (13) and (14) can either be connected hinge-like manner with a further rod with the hand lever (2), or the storage of the additional rods (13) and (14) takes place as in Fig. 2 in a slotted hole storage, allows the rods to slide in this storage.

It is also possible to firmly attach one of the two cutting blades to the counter jaw, as shown in Fig. 4. So that different wire thicknesses can be cut off and clamped in the jaws at the same time, the counter jaw must not be mounted like a hinge joint, but must be movable in the bending and cutting plane. This can e.g. B. an additional linkage can be achieved in which the counter jaw ( 7 ) is mounted, or the storage of the counter jaw takes place in a sliding hole, as shown in Fig. 4.

Instead of simultaneously exerting force on the cutting and bending mechanism, it is also possible to exert a force on the cutting mechanism first and after cutting the wire on the bending mechanism. In the embodiment of FIG. 5, this is achieved in that the cutting jaw ( 22 ) is pressed against the other cutting jaw ( 12 ) via an eccentric drive ( 24 ). In this embodiment, it must be ensured that the force acting on the bending mechanism only begins after or at the end of the cutting process. For this purpose, the additional rod ( 14 ) is mounted in the gliding hole ( 16 ) of the handle ( 2 ) in such a way that it only transmits a force to the bending lever ( 3 ) when the handles have been pressed together to a certain extent.

The following pictures are used to explain some of the preferred ones Design examples and functional principles. Show it:

Fig. 1 a pair of wire cutters for bending wires with two driving handles. Cutting the wire is not possible with this version. The wire ( 9 ) to be bent protrudes from the bone ( 18 ). The second handle, which drives the bending lever ( 3 ), has been omitted in the drawing for better clarity; its shape and position correspond to the illustration of the handle ( 2 ) in Fig. 2. The force of the handle is determined by the bolt ( 4 ) of the bending lever ( 3 ) transferred to the bending lever ( 3 ), the central pin ( 5 ) serving as a counter bearing. Via the bolt (6) of the Umbiegehebel is connected hinge-like manner with the counter-jaw (7) which in turn is mounted in the central pin (7). During the bending process, the moment fixing the wire ( 9 ) in the jaw ( 8 ) and in the counter-jaw ( 7 ) must be greater than the bending moment with which the wire is bent around the jaw ( 8 ). In the following, the corresponding mechanical verification of this functional principle is calculated for the starting position at the beginning of the bending process, in principle this calculation can also be extended to the entire bending process, whereby the distribution of the forces according to the position of the bending lever ( 3 ) must be taken into account. For the sake of simplicity, it should also be assumed that the force of the handle ( 2 ) acts on the bolt ( 4 ) of the bending lever ( 3 ) in the horizontal direction at the beginning of the bending process. Corresponding to the lever arms a and b, the force of the handle ( 2 ) F _{G is distributed} over the reaction forces F _H on the bolt ( 6 ) and F _D as the wire bending force. The force F _B acting on the counter jaw and on the jaw of the handle ( 1 ), which determines the holding torque of the wire in the jaws, is calculated from the force F _H and the lever arms A and B. This results in the following relationships:

F _B = B / A * F _H , F _H = b / (a + b) * F _G , F _D = a / (a + b) F _G.

In order for the wire to be fixed in the jaw and counter jaw with a greater bending moment than the torque exerted on the wire by the wire bending lever ( 3 ), the following must apply:

F _B * l <F _D * L.

From this follows after inserting the relationships given above:

B * l * b / A <a * L.  

The following geometrical examples can be found for a typical example Dimensions:

A = 32 mm; W = 25 mm; a = 4 mm; b = 10 mm;
L = 10 mm; l = 8 mm.

After inserting into the above inequality:

62.5 <40.

In this case, the wire is securely clamped on Given at the beginning of the bending process.

Fig. 2 a pair of wire cutters for bending and cutting wires with two driving handles. The handle ( 2 ) acts on the bending lever ( 3 ) at two different points. At the beginning of the compression of the handles, the handle acts on the pin ( 10 ) as a counter bearing with a relatively small lever arm on the bending lever ( 3 ), so that in this phase a large force is exerted on the wire so that it is on the blade ( 12 ), which is firmly connected to the handle ( 1 ), can be easily cut off. In this phase, the wire is not firmly fixed in the jaw ( 8 ) of the handle ( 1 ) and in the counter jaw ( 7 ). After the wire has been cut off, the handle ( 2 ) acts via the bolt ( 11 ) as a counter bearing with a larger lever arm on the wire bending lever ( 3 ). The force relationships explained in Fig. 1 are now effective, so that the wire is firmly clamped in the jaws during the bending process.

Fig. 3 a pair of wire cutters for bending and cutting wires with two driving handles. The handle ( 2 ) now acts via a slot ( 17 ) as a sliding bearing on the rods ( 13, 14 ). Rod ( 13 ) acts on the cutting jaw ( 17 ), the cutting edge ( 12 ), which is firmly connected to the handle ( 2 ), serves as a counter jaw for pinching off the wire. In the present example, the cutting jaw ( 17 ) is also mounted in a hinge joint-like manner in the central bolt ( 5 ). When the handle ( 2 ) and handle ( 1 ) are pressed together, the bending lever ( 3 ) and the cutting jaw ( 17 ) are therefore subjected to a force in accordance with the geometric lever ratios. As soon as the wire is pinched off, the bending lever ( 3 ) can bend the wire around the jaw ( 8 ) of the hand lever ( 2 ). Here, too, the lever ratios must be selected so that the wire is securely clamped in the jaws during the bending process.

Fig. 4 a pair of wire cutters for bending and cutting wires with two driving handles. The wire ( 9 ) is pinched off with the aid of the cutting edge ( 12 ) and cutting edge ( 19 ). The cutting edge ( 12 ) in the above examples is firmly connected to the handle ( 1 ), cutting edge ( 19 ) to the counter jaw ( 20 ). In order to ensure a complete pinching off of the wire and the subsequent fixing of the wire in the jaws even with different wire diameters, the counter jaw is displaceably mounted in the central hole in a longitudinal hole ( 21 ).

Fig. 5 a pair of wire cutters for bending and cutting wires with two driving handles. The cutting jaw ( 22 ) is mounted in the central bolt ( 5 ). When the handles are pressed together, the handle ( 2 ) presses via the eccentric ( 24 ) onto the bolt ( 23 ), which is firmly attached to the cutting jaw ( 22 ) as a counter bearing. As a result, the wire between the cutting jaw ( 12 ) and the cutting jaw ( 22 ) is cut off while the rod ( 14 ) slides in the slide hole ( 16 ) of the handle ( 2 ) and does not exert any force on the bending lever ( 3 ). Only after the cut has been made does it lie against the upper edge of the sliding hole ( 16 ), so that a force transmission for bending the wire now occurs.

Fig. 6 a pair of wire cutters for bending and cutting wires with three driving handles. The wire is first pinched off by squeezing the handles ( 1 ) and ( 2 ) over the cutting jaws ( 12 ) and ( 26 ) which are firmly connected to these handles and easily run past each other. The wire is firmly clamped in via the jaw ( 25 ) firmly connected to the handle ( 2 ) and the jaw ( 8 ) firmly connected to the handle ( 1 ). The wire can be clamped in place using the catch ( 15 ), and the wire can be released again by pulling back the lever ( 28 ). The wire can then be bent by actuating the handle ( 27 ), which is firmly connected to the bending lever ( 3 ).

Claims (16)

1. Medical wire-nose pliers, characterized in that the wire is fixed in the forceps and is bent to an angle of 180 ° when the two handles of the forceps are further compressed. 2. Medical wire-nose pliers according to claim 1, characterized in that the wire when pressing the two handles of the pliers before, after or is cut off during the bending process. 3. Medical wire-nose pliers according to claim 1, characterized in that the strength of the two handles through appropriate storage and use from additional rods to the wire clamping jaws and the bending mechanism is distributed that the wire in the bending process with a larger Bending moment in the jaws or holder is held as that Bending moment caused by the bending mechanism on the wire when bending the same is exercised so that the jaws during the bending process Secure the wire firmly and keep it closed. 4. Medical wire-nose pliers according to claim 2, characterized in that the strength of the two handles through appropriate storage and use of additional rods so on jaws, cutting mechanism and Bending mechanism is distributed that when cutting the wire a large Force acts on the cutting jaws or cutting blade and the wire after Cutting in the bending process with a larger bending moment in the Jaw or holder is recorded as the bending moment caused by the Bending mechanism is exerted on the wire when it is bent, so that the jaws fix the wire firmly during the bending process and stay closed. 5. Medical wire cutters, characterized in that the wire is bent using a bending lever, the one in one of the two jaws or in a guide is stored and from the handles directly or through an additional linkage is driven so that when pressing the bending lever handles the wire from the bending lever around the one wire fixing jaw is bent up to an angle of 180 °. 6. Medical wire pliers, characterized in that the bending of the wire is accomplished with the aid of a bending lever ( 3 ) which is mounted in a hinge-like manner at one end in one of the two jaws and acts on the wire with the other end and directly from the handles or is driven by an additional linkage, so that when the handles are compressed, the wire is bent by the bending lever around the one jaw that fixes the wire up to an angle of 180 °, the bending lever turning itself through the positioning of the bearing relative to the jaw which the wire is bent, only turns up to an angle of about 90 ° in its storage. 7. Medical wire-nose pliers according to one of claims 1-6, characterized in that the one wire clamping jaw ( 8 ) firmly connected to the one handle ( 1 ), the other wire clamping jaw ( 7 ) is mounted in a hinge-like manner, the wire bending lever ( 3 ) z. B. is mounted in a hinge-like manner in this second counter jaw ( 7 ) and is driven via the second hand lever ( 2 ), so that the wire bending lever ( 3 ) at one end on the wire and through its hinge-like bearing at its other end on the counter jaw ( 7 ) exerts a force, the lever ratios being selected so that during the bending phase the bending moment acting on the wire in the wire clamping jaws ( 7 ) and ( 8 ) is greater than the moment acting on the wire by the bending lever ( 3 ). 8. Medical wire-nose pliers according to claim 7, characterized in that the same lever ( 3 ) acting on the wire is used for cutting and bending, which leads the wire before, during or after the bending process past a blade which leads the wire to the desired length cuts off. 9. Medical wire-nose pliers according to claim 8, characterized in that the same lever ( 3 ) acting on the wire is used for cutting and bending, the transmission ratios of this lever and the parts moving it in relation to the driving hand lever ( 2 ) depending on the position the handles are different from each other, so that the cutting process and the bending process take place with different transmission ratios, so that a large force is exerted on the wire during the cutting process and a smaller force is applied when bending. 10. Medical wire-nose pliers according to one of claims 1-7, characterized characterized in that for cutting and bending two different levers acting on the wire be used, both with each other and with the driving handle are articulated with the help of an additional linkage, so that the Force of the handles on both levers according to the lever ratios distributed so that after the cutting process with the help of the cutting lever, that works against a cutting blade firmly connected to the counter handle, when the handles are pressed together, the bending process with Help of the other lever is performed. 11. Medical wire-nose pliers according to one of claims 1-7, characterized in that two different levers acting on the wire are used for cutting and bending, the cutting lever ( 22 ) being connected to the one hand lever ( 2 ) by an eccentric shaft ( 24 ). driven and the bending mechanism is driven only after or at the end of the cutting process. 12. Medical wire-nose pliers according to one of claims 1-7, characterized in that two different levers acting on the wire are used for cutting and bending, the cutting lever ( 19 ) being integrated in the counter jaw ( 7 ), which in turn is movable - for . B. in a longitudinal hole ( 21 ) - to allow complete contact of the counter jaw ( 7 ) on the main jaw ( 8 ) on the one hand and on the shear bar ( 12 ) on the other with different wire thicknesses, the force of the handles via an additional linkage drives both the cutting lever ( 19 ) integrated in the counter jaw and the bending lever ( 3 ). 13. Medical wire cutters, characterized in that the wire is first clamped in jaws by two handles directly - or indirectly with the help of additional linkages - and then directly due to the force due to an additional handle - or indirectly with the help of additional rods. 14. Medical wire cutters, characterized in that the wire is first clamped in jaws by two handles directly - or indirectly with the help of additional linkages - and then directly due to the force due to an additional handle - or indirectly with the help of additional rods - cut and bent becomes. 15. Medical wire-nose pliers, characterized in that the wire is first clamped in jaws and cut off by two steps directly - or indirectly with the help of additional rods - are driven and then by the action of a force Additional handle directly - or indirectly with the help of additional rods - is bent. 16. Medical wire cutters according to one of claims 13-15, characterized characterized in that the handles pressed together to clamp the wire in one Closure can be fixed and released.