DE9310668U1 - screwdriver - Google Patents

Description

Leibinger GmbH
lG-69 464
16.07.1993

screwdriver

The invention relates to a screwdriver with the features of the preamble of claim 1.

Bone screws, i.e. screws used in surgery in particular, are screwed into the bone using a screwdriver, just like the usual screws, and then unscrewed again if necessary. In the field of medical technology, there are special requirements for the system consisting of screwdriver and screw. During a surgical procedure, the screws are usually screwed into the bone under difficult conditions. In particular, blood or tissue can hinder the screwing process. In many surgical procedures, the space in which the screw is to be screwed into the bone is very difficult for the screwdriver to access.

During surgical interventions, it is often necessary that only a very narrow channel is available for the screwdriver or its blade (see below) or that this channel should be kept as narrow as possible for various reasons.

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For example, in surgery on the human lower jaw, situations arise in which a bone screw is screwed into a bone and only a cannula through the cheek to the lower jaw is available for inserting the screwdriver or screwdriver blade. This cannula should be as narrow as possible in order to carry out the procedure through the cheek as gently as possible and thus to keep nerve damage, damage to the blood vessels and also negative cosmetic consequences of the operation as low as possible. There is therefore a need to keep access to the surgical area, in this case to the head of the screw to be screwed in, as narrow and tight as possible.

On the other hand, when inserting the screw, it is necessary to temporarily hold it on the blade of the screwdriver so that the surgeon can use the screwdriver to position the screw at the desired location on the bone and then screw it in.

In the state of the art of general screw technology (i.e. not in the field of surgery), screwdrivers are known for this purpose for slotted screws, the blade of which is split and can be spread by means of a sleeve so that the blade clamps itself force-fittingly in the slot of the screw, so that the screw is held on the blade of the screwdriver.

From the German publication DE 22 14 466 it is known to provide so-called Allen keys with clamping devices for polygon socket screws. Finally, screwdriver bits for general tools for use in mechanical engineering, which are detachably attached to a tool holder by spring-loaded locking balls, are known. However, these spring-loaded clamping or locking balls are used to hold the screwdriver bit in a hand holder.

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The invention is based on the task of designing a screwdriver of the type mentioned at the beginning in such a way that screwdriver blades with the smallest possible diameter can be used and, in addition, the screw can be held reliably and with simple means on the screwdriver, whereby screwing the screw into the bone should be as easy as possible for the surgeon and the view of the surgical area should be as unobstructed as possible. In addition, the surgeon should have as few tools as possible to choose from in order to be able to carry out the necessary measures.

According to the invention, this object is achieved by a screwdriver with the features of claim 1.

This solution according to the invention has the particular advantage that the screwdriver and in particular its blade have a relatively small diameter, so that this tool makes it relatively easy for the surgeon to see the screw and also to control what is happening at the operation site.

According to another solution to the above-mentioned problem according to the invention, when using a screw with a head that has an external polygon, it is provided that a spring is arranged in the blade of the screwdriver on the recess in such a way that its spring force acts perpendicular to the longitudinal axis of the recess, and that the spring has a body at its radially inner end or acts on such a body, wherein the body is supported on an outer wall of the polygon when the recess of the blade is pushed over the polygon and in the process compresses the spring against the spring force.

According to a preferred embodiment of the screwdriver according to the invention of the first variant (claim 1), it is provided that the blade of the screwdriver is a polygon, in particular a hexagon or square body, and that

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accordingly, the recess in the head of the screw is an internal polygon, in particular an internal hexagon or an internal square.

Preferably, the body connected to the spring is designed such that it has a spherical, i.e. rounded, surface, in particular a spherical surface, at least in a partial area.

According to a preferred embodiment of the screwdriver according to the invention according to the second variant, it is provided that the body connected to the spring or the body interacting with the spring has a spherical surface, in particular at least partially a spherical surface.

Preferably, the spring has an elongated shape and extends with its longitudinal axis parallel to the longitudinal axis of the blade, wherein the spring has a compressible protrusion which protrudes into the interior of the recess when the recess of the blade is not pushed over an external polygon of a screw.

According to a particularly preferred embodiment, the screwdriver is characterized in that the screwdriver blade has a hollow prismatic body, the outer surface of which forms an external polygon and the inner surface of which forms an internal polygon.

This design allows the use of a screwdriver for internal and external polygonal screws, whereby the inner and outer diameters of the screw heads that can be handled with a screwdriver are different.

Advantageously, the screwdriver described above is characterized in that the screwdriver blade has a spring transverse to the inner surface, the

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Spring force acts transversely to the inner surface, whereby the spring rests against an outer wall of the screw head's molded part when the screwdriver blade is pushed onto the molded part of a screw head, thereby tensioning the spring. This means that the respective screw can be held on the screwdriver blade until it is securely screwed into the respective assembly point.

The same applies to a further embodiment in which the screwdriver can be characterized in that the screwdriver blade has a spring on its outer surface, the spring force of which acts transversely to the outer surface, whereby the spring is supported against an inner wall of the shaped part of the screw head when the screwdriver blade is pushed into the shaped part of a screw head and the spring is thereby tensioned.

In the following, embodiments of the invention are described in more detail with reference to the drawing. It shows:

Fig. 1 shows a schematic side view of a screwdriver according to the invention, with the blade shown partially in section;

Fig. 2 a screwdriver according to Fig.l also from de:
Fig.l;

from the side in the direction of arrow P according to

Fig. 3 is an axial plan view of the screwdriver according to Fig. 1 in the direction of arrow P;

Fig. 4 is a plan view of a head of a screw used together with a screwdriver according to Figs. 1 to 3, and

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Fig. 5 shows another embodiment of a screwdriver according to the invention for use with a screw whose head has an external hexagon;

Fig. 6 is an axial plan view of the screwdriver according to Fig. 5 in the direction of arrow P;

Fig. 7 shows a further embodiment of a screwdriver for use with a screw whose head is provided with an external polygon, in a section parallel to its longitudinal axis, but at a distance from it;

Fig. 8 shows a section through a screwdriver according to Fig. 7 perpendicular to the section according to Fig. 7 and containing the longitudinal axis;

Fig. 9 is a section through a screwdriver according to Figs. 7 and 8 perpendicular to the longitudinal axis;

Fig. 10 shows another embodiment of a screwdriver suitable for use with internal and external polygon head screws, in a side plan view;

Fig. 11 the screwdriver according to Fig. 10 in a frontal plan view of the screwdriver blade in a slightly reduced representation;

Fig. 12 is a partial sectional view of the screwdriver blade according to fig. II along the line A-A;

Fig. 13 another embodiment of a screwdriver for use with polygon socket screws in a side plan view; and

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Fig. 14 is a partial sectional view along the longitudinal axis of the screwdriver blade according to Fig. 13 in an enlarged view.

The screwdriver 10 according to the figures has a blade 12 at its distal end. In the sense of the invention, the term "blade" is to be understood as the component of a screwdriver that engages with a screw in order to screw the screw into or out of a bone.

The longitudinal axis 14 of the blade 12 is therefore also the axis of rotation when screwing in or unscrewing a screw.

The screwdriver 10 has a base 16, which in the illustrated embodiment is designed as a hexagon, just like the blade 12. The base 16 is inserted into a correspondingly designed hexagon socket in a handle (not shown). The surgeon thus grasps the screwdriver 10 by the handle (not shown) in order to screw a screw 30, which is shown in Fig. 4 in a top view of the head, into a bone.

Thus, the screwdriver 10 has a shaft 18 which at one end merges into the base 16 to which the handle is attached, while the other end of the shaft 18 merges into the blade 12 which engages the screw.

This is a screwdriver 10 that in principle has a replaceable blade 12. This is related to the replaceability of the blade 12, which is subject to mechanical wear. A rigid screwdriver 10 with the same working function is also conceivable, but whose blade 12 is firmly connected to the handle.

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At the end of the blade 12 facing the screw, a cavity 24 in the form of a bore is arranged in the same (Fig. 1), with the axis of the bore being perpendicular to the longitudinal axis 14 of the blade 12. A spring 22 is arranged in the cavity 24, which in Fig. 1 is supported at one end on the bottom of the cavity 24, while the opposite, other, radially outer end of the spring 22 is rotatably connected to a body 20 which is spherical (rounded) at its radially outer end. In the embodiment shown, the body 20 is spherical in its section protruding sideways from the cavity 24. The rotatability of the body 20 ensures less material wear and more convenient insertion of the blade 12.

Furthermore, the shaft 18 of the screwdriver 10 has a taper 26, which serves, for example, for attaching coding (color coding) or the like and takes on a holding function in the handle.

The body 20 is held in the cavity 24 in the blade 12 by means of a flange 28. The body 20 compresses the spring 22 so that the body 20 is permanently prestressed radially outward.

The screwdriver described above with reference to Figs. 1 to 3 (corresponding components are provided with the same reference numerals) is used together with a screw 30 according to Fig. 4. Fig. 4 shows the screw in an axial top view of its head 34, in which a recess 32 is formed.

Since in the illustrated embodiment according to Figs. 1 to 3 the blade 12 of the screwdriver is shaped as a hexagon, the recess 32 in the head 34 of the screw 30 is correspondingly shaped as an internal hexagon, as shown in Fig. 4. If the blade 12 is thus inserted into the recess 32 in the head 34

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the screw 30 is inserted, then the body 20 is pressed radially inwards against the spreading force of the spring 22, with the radially outermost point of the body 20 resting on the inner wall 36 of the recess 32. This creates a spreading force between the blade 12 and the head 34 of the screw 30, due to which the screw 30 is held force-fittingly on the blade 12. The size of this force-fitting connection can be adjusted by means of the spring 22. The stronger the spreading force of the spring 22 when compressing while inserting the blade 12 into the recess 32, the greater the holding force with which the screw 30 is held on the blade 12.

Once the screw has been screwed into the bone, the screwdriver 10 can be pulled out of the recess 32 against the holding force generated by the spring 22.

Additional external screw holding devices are not required and are therefore not required.

The screwdriver described above allows blades with a particularly small diameter of e.g. 1.5 mm as well as screws with a diameter of 2 mm or more. This allows extremely narrow surgical access and guide cannulas for attaching the screwdriver.

Fig.5 shows a further embodiment of a screwdriver, which, unlike the embodiment according to Figs.1 to 4, is used with a screw whose head does not have a polygonal recess, but rather a polygonal projection, i.e. a so-called external polygon.

Figures 5 and 6 show a first embodiment of a screwdriver for use with a screw that has an external polygon, the embodiment shown is an external hexagon.

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A blade 40 of the screwdriver has a recess 42 which is hexagonal in shape as shown in Fig. 6. A recess 45 is formed on the side of an edge of the hexagonal recess 42, in which a spring 44 is arranged. The spring 44 is spot-welded to the blade 40 of the screwdriver at point 47, for example by laser welding.

The spring 44 is elongated, e.g. as a spring wire, with the longitudinal axis of the spring 44 extending essentially parallel to the longitudinal axis 44 of the blade. The spring 44 has a protrusion 46 which projects radially inward into the recess 42.

If the blade 40 of the screwdriver is pushed over a screw with an external hexagon head as shown in Figs. 5 and 6, the protrusion 46 of the spring 44 comes into sliding contact with one side of the external hexagon and is tensioned, i.e. the protrusion 46 of the spring 44 is pressed radially outwards and thus creates a tensioning force between the blade 40 and the screw. The screw is not shown in the figures, since screws with an external hexagon are known as such.

The solution according to Figures 5 and 6 is characterized by low manufacturing costs and high functional reliability.

Figures 7 to 9 show another embodiment of a screwdriver for use with a screw whose head has an external hexagon.

According to Fig.7 to 9 (in particular Fig.9), a blade 50 of a screwdriver is equipped with a ball 52 which is pre-tensioned radially inwards. Two spring steel wires 54, 56 serve to pre-tension the ball 52 radially inwards. The spring steel wires 54, 56 each pass through a

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Recess 58 or 60 such that they can be bent radially in relation to the longitudinal axis 14 of the blade 50. The ends of the spring steel wires 54, 56 are each inserted with a precise fit into holes 62, 64. This means that the spring steel wires 54, 56 can be bent radially by the ball 52, which is held in a cage 65 (Fig. 8). As Fig. 9 shows, the ball 52 projects radially inwards over a side edge of the hexagonal recess 68 in the blade 50. If the blade 50 with its recess 68 is pushed over an external polygon of a screw (not shown), the ball 52 is pressed radially outward against the pre-tensioning force of the spring steel wires 54, 56 and thus generates a tensioning force between the blade 50 and the external polygon of the screw, so that the screw is securely held in the blade 50.

A cover 66 covers the cage 65 for the ball 52 and the other components interacting with the ball 52.

Both embodiments according to Figs. 5 and 6 on the one hand and Figs. 7 to 9 on the other hand are characterized by the fact that the size of the spring and the associated components is very small, so that the blade as a whole can only have a very small diameter.

Figures 10 to 12 illustrate another embodiment of a screwdriver for use with a screw whose head has either an external hexagon or an internal hexagon.

The same parts as in the previous embodiment are provided with corresponding reference numerals.

The blade 40 of the screwdriver according to Figs. 10 to 12 has a substantially hollow prismatic shape, wherein the outer surface 70 is provided with a head of a polygon socket screw in

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can be brought into engagement and the inner circumferential surface 72 can be brought into engagement with the head of an external polygonal screw.

In the present example, for the sake of simplicity, only a spring 44 is arranged on the inner surface 72, which is spot-welded to the blade of the screwdriver at point 47, e.g. by laser welding.

The spring 44 is aligned substantially parallel to the longitudinal axis of the screwdriver blade and has a protrusion 46 which projects radially inward into the recess 42.

It is understood that one or more such springs 44 can also be arranged on the outer surface 70. However, different designs of spring clamps can also be provided for clamping on the inner surface and on the outer surface.

Figures 13 and 14 show another embodiment of a screwdriver suitable for use with polygon socket head screws. The prismatic blade 50 has an axial multi-stage bore 58 in which a rod-shaped spring element 54 is firmly fitted.

In the area of the stepped bore 58 that extends toward the free end of the blade 50, the latter widens to such an extent that the spring element 54 can move in the radial direction.

Across the enlarged area of the bore 58, a through-bore 76 is provided in the blade in the radial direction, which is completely penetrated by the spring element 54. A ball element 52 is accommodated in the transverse bore 76, which protrudes slightly from the bore 76. In the area of the bore 76 in which the ball element 52 is located, the bore 76 tapers so far that the ball cannot fall out of the bore. On the inner

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The ball rests against the spring element 54. This means that the ball element 52 is held captive in the bore 76.

When the blade 50 is pushed onto a polygon socket head screw, the ball engages the polygon socket of the screw, whereby the ball is pushed radially back into the interior of the bore 76. The spring element 54 can bend in the stepped bore 58 to such an extent that the ball is pushed far enough into the bore 76 to enable the blade 50 to be pushed completely into the corresponding recess in the screw head. However, since the spring element 54 tends to push the ball element 52 radially outwards, the screw is held firmly to the blade.

This clamping mechanism, described in connection with a blade for an internal polygon screw head, can of course also be used in the context of a blade for an external polygon screw head.

In all the embodiments described above, the pull-off force, e.g. of a screw from the blade, can be set to > 0.2 N by appropriately designing the spring elements. In the case of screws that are used to attach very small bone fragments, if the pull-off force is too high, the tool can be released from the implant even after screwing in, causing the bone to shift, especially since the screws are not all inserted at the same time and a structure that is relatively firm after all screws have been attached can initially be very unstable, for example with the first screw or screws. From this point of view, the pull-off force of a screw should be in the range of 1 N.

As a rule, i.e. in the case of simple and inherently stable fractures (even if the stability is impaired by repositioning the fragments

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to each other), the holding force can be in the range of 0.2 N to several N.

In the traumatology of the large bones in the human body (e.g. long bones), a higher pull-off torque or a higher pull-off resistance must be achieved right from the start, since, for example, larger screws are used in the orthopedic field and handling is often not as delicate as is the case in the microsurgical field.

Greater withdrawal forces are mainly required when removing implants. Although biocompatible implant materials are often used, implants are removed from the body again after the biological process of osteosynthesis has been completed. When removing an implant, pressure in the sense of forward thrust should naturally not be exerted on the implant material, as this could trigger spontaneous fractures in individual cases. It is therefore necessary for the surgeon to be able to exert tensile rather than shear forces, e.g. when unscrewing a screw. Since these tensile forces are difficult to control, the holding force of a screw should be relatively high.

Claims (9)

Leibinger GmbH lG-69 464 16.07.1993 Claims 1. Screwdriver (10) for screws (30) to be screwed into bones, which have a shaped part (32) in their head (34), with a screwdriver blade (12) which can be brought into engagement with the shaped part (32) at least approximately precisely in the direction of its longitudinal axis (14), characterized in that the blade (12) of the screwdriver (10) has a spring (22) whose spring force acts approximately perpendicular to the longitudinal axis (14) of the blade (12), and that the spring (22) has a body (20) at one end or is connected to such a body which, when the blade (12) is brought into engagement with the shaped part (32) of the screw head (34), is supported on a side wall (36) of the shaped part (32) and in the process compresses the spring (22) against the spring force. 2. Screwdriver according to claim 1, characterized in that the blade (12) of the screwdriver (10) is an external polygon, in particular a hexagon or square body, and that the molded part (32) on the head (34) of the screw (30) is correspondingly an internal polygon, in particular an internal hexagon or an internal square, and the spring has the body (20) at its radially outer end or is connected to it. - 2 - lG-59 464 3. Screwdriver according to claim 1,
characterized in that the screwdriver blade (12) has a recess (42; 68) which can be pushed over an external polygon of a screw head in the direction of its longitudinal axis (14), that the blade (40; 50) of the screwdriver has a spring (44; 54, 56) on the recess (42; 68), the spring force of which acts approximately perpendicular to the longitudinal axis (14) of the recess (42; 68), and that the spring (44; 54, 56) has a body (46; 52) at its radially inner end or acts on such a body which, when the recess (42; 68) of the blade is pushed over the polygon, is supported on an outer wall of the polygon and in the process compresses the spring (44; 54, 56) against the spring force. 4. Screwdriver according to claim 1, characterized in that the screwdriver blade (12) has a hollow prismatic body, the outer surface of which forms an external polygon (70) and the inner surface of which forms an internal polygon (72). 5. Screwdriver according to claim 4, characterized in that the screwdriver blade (12) has a spring (44, 46) on its inner surface, the spring force of which acts transversely to the inner surface, the spring being supported against an outer wall of the shaped part of the screw head when the screwdriver blade (17) is pushed onto the shaped part of a screw head, and the spring (44, 46) is thereby tensioned. 6. Screwdriver according to claim 4, characterized in that the screwdriver blade (17) has a spring (44, 46) on its outer surface, the spring force of which acts transversely to the outer surface, the spring (44, 46) when inserted - 3 - lG-69 464 the screwdriver blade on the shaped part of a screw head is supported against an inner wall of the shaped part of the screw head and the spring (44, 46) is tensioned. 7. Screwdriver according to one of the preceding claims, characterized in that the spring (44) has an elongated shape and extends with its longitudinal axis approximately parallel to the longitudinal axis (14) of the blade (40), wherein the spring (44) has a compressible protrusion (46) which, when the recess (42) of the blade (40) is not pushed over an external polygon of a screw, projects into the interior of the recess (42). 8. Screwdriver according to one of the preceding claims, characterized in that the body (46) connected to the spring (44) or the body (52) cooperating with the spring (54, 56) has a spherical surface, in particular at least partially a spherical surface. 9. Screwdriver according to one of the preceding claims, characterized in that the spring (44) has an elongated shape and extends with its longitudinal axis parallel to the longitudinal axis (14) of the blade (40) in the latter and penetrates a radial bore (76), the spring (44) pressing against a ball element (52) which is held in the bore (76), the ball protruding from the bore (76) when the blade is not pushed into a polygon socket of a screw.