DE29611140U1 - Arrangement of a screwdriver and a corresponding screw - Google Patents

Description

WILHELM3:-:;i£iLl£h:& PARTNER

• PATENT ATTORNEYS · · · ·

EUROPEAN PATENT ATTENDANCE MANDATORY LICENCES BREVETS OPEN

DR. RER. NAT. ROLF E. WILHELMS DR. RER. NAT. HELMUT KILIAN DIPL.-PHYS. ECKART POHLMANN

DIPL. ING. LEONHARD HAIN

Eduard-Schmid-Strasse 2 D-81541 Munich
Telephone (O 89) 65 20 91
Telex 523 467 (wilp-d)
Fax (0 89) 6 51 62 06 Electronic Mallbox:
X400: C = DE, A = DBP,
S = Wilhelms Kilian + Partner

GP8770DE

Landanger-Landos, Blanc, Carriou, Lebeau, Michelet, Pinsolle

France

Arrangement of a screwdriver
and a corresponding screw

Priority: 26 June 1995 - France - No. 9507661

Description

The invention relates to an arrangement comprising a screwdriver and a corresponding screw, which is intended in particular, but not exclusively, for traumatological or corrective jaw-facial microsurgery.

It is known that a maxillofacial surgeon uses small plates with holes through which a screw passes to fix the plate. This screw has very small dimensions, as will be explained in detail later. To correct fractures in the facial skull, for example in classical traumatology, plates are used that have different shapes depending on the type of fracture. Such plates can, for example, have the shape of an X if the bone fragment

Landanger-Landos et al GP8770DE

above the bridge of the nose as it is curved. They can also be L-shaped if during corrective surgery (adding or removing) the surgeon wants to create a step to receive the broken bone.

To screw in a screw, it is known to use a screwdriver with a gripping claw at the end, which is arranged at an angle of 120°, for example, to grip the head of the screw and hold it in contact with the screwdriver. These claws are attached to a sliding sleeve that encloses the shaft of the screwdriver. To release the lock, the sleeve and the claws are pulled back, thus ending the clamping of the screw.

This known design has various disadvantages: Firstly, it has a relatively large external volume, since the holding claws enclose the head of the screw. It also makes it necessary to provide an undercut for the holding claws under the head of the screw, which is then disruptive when this screw is inserted into a plate. Finally, the surgeon's view in the operating field is impaired or obscured by the shaft of the screwdriver and the external gripping claws.

Another type of screwdriver has already been proposed, the end of which consists of a truncated pyramid, profiled to fit into a corresponding recess in the head of the screw. Such a design is very difficult to use because of the small dimensions of the surgical screws used and the necessarily close tolerances. It is also very expensive.

The invention is therefore intended to create an arrangement of a screwdriver and a corresponding screw which takes up as little space as possible and which does not attack the head of the screw from the outside, without having the disadvantages of the second known embodiment described above.

Landanger-Üandos et al GP8 770DE

take.

According to the invention, the free end of the shaft of the screwdriver has an axial shoulder that is polygonal in cross-section and conical in longitudinal section, as well as radial wings on both sides of the shoulder, and the screw is provided with a head in which an axial housing is recessed with a polygonal cross-section that is complementary to the shoulder and opens into two lateral radial slots on both sides, the housing and the slots being designed to receive the shoulder and the wings, and the insertion of the shoulder into the housing of the head of the screw by means of a press fit ensures that the screw is held in place by the screwdriver.

This special design, in combination with an appropriate hardness of the shaft, ensures sufficient breaking strength, which prevents any risk of deformation of the neck or wings when screwing in the screw.

Preferably, the base and wings are formed in one piece with the rest of the shaft.

According to another characteristic of the invention, the screwdriver has an ergonomic handle consisting of two complementary longitudinal elements. One of these elements forms the handle proper, is mounted so as to rotate freely with respect to the second element and is intended to hold the screwdriver in the inner palm of the operating surgeon. The other element is an intermediate insert which forms the active part, is fixed to the shaft of the screwdriver and is slightly longer than the first mentioned element. It is intended to accommodate the surgeon's fingers so that he can evenly rotate the shaft of the screwdriver when screwing it in.

The surgeon can thus hold the handle in the palm of his hand so that he can control the insert and the shaft of the screwdriver.

Landanger-Liandos et al GP8770DE

hers to screw in the screw, which is firmly connected to the end of the shaft by a clamp or press fit.

Particularly preferred embodiments of the invention are described in more detail below with reference to the accompanying drawings. They show

Fig. 1 is a scaled partial axial sectional view of an embodiment of the screwdriver of the arrangement according to the invention,

Fig. 2 is a partial perspective view on an enlarged scale of the end of the shaft of the screwdriver of Fig. 1,

Fig. 3 is a side view of the end portion of the shaft shown in Fig. 2 from the side of one of the wings, with the head of a corresponding surgical screw engaged therewith,

Fig. 4 is a cross-sectional view along the line 4/4 in Fig. 3,

Fig. 5 is a front view of the free end of the end portion of the shaft shown in Figures 1 to 4,

Fig. 6 is a partially sectioned longitudinal view on an enlarged scale of the surgical screw shown in Fig. 3 and

Fig. 7 is an end view of the screw head of Fig. 6.

The assembly shown in Fig. 1 is particularly intended for maxillofacial surgery, as already indicated, and consists of a screwdriver 1 and a corresponding screw 2, the head of which can be engaged with the end of the shaft 3 of the screwdriver.

The screwdriver 1 has an ergonomic handle consisting of two separate and complementary longitudinal elements. A part 4 forms the actual handle and the device for picking up and holding the screwdriver inside the hand, namely in the middle of the inner palm,

Landanger-Landos et al GP8770DE

while the second element, namely an intermediate insert 5, represents the active part during manual screwing.

The handle 4 is freely rotatable with respect to the insert 5 and the active part formed by it is longer than the part 4. The surface of the insert 5 has axial grooves and other devices (for example knurls and notches) for holding the fingers.

The insert 5 is secured by an axial screw 6 which is seated in an axial bushing or sleeve 7 of the handle 4, in which an axial receptacle 8 is suitably formed for this purpose.

Abutment means are provided in the sleeve 7 to axially hold the screw 6 and thus the insert 5. In the illustrated embodiment, these abutment means consist of an inner radial projection 9 which forms a cylindrical reinforcement on the inner wall of the sleeve 7 between the head 6a of the screw 6 and the end of the insert 5. The outer annular surface of the reinforcement 9, which is remote from the insert 5, serves as a receiving seat for the head 6a of the screw 6. This design thus prevents the insert 5 and the screw 6 from becoming detached from the handle 4, while still allowing the insert 5 and the screw 6 to rotate freely with respect to the handle 4.

The sleeve 7 is firmly secured in the handle 4 by suitable means, such as those represented by a transverse pin 11.

The free end of the shaft 3 has an axial extension 12, the cross-section 13 of which is polygonal (Fig. 2 and 4) and the longitudinal section 14 of which is conical. In the embodiment shown, this polygonal cross-section is hexagonal, a profile that represents a good compromise between the requirement to produce a component with low costs and very small dimensions and a regular and sufficient

Landanger-IJandos et al GP8770DE

-S-

Distribution of the clamping load or clamping effect in the recess in the head of screw 2.

Two wings 15 run on both sides of the extension 12 in the radial direction and in the longitudinal direction. They are connected to the shaft 3 via rounded grooves 16.

The conical part 14 is delimited by ridges 17 which start from the vertices of the polygonal cross-section 13 and are connected to the rest of the shaft 3 via rounded grooves 18, as are the surfaces lying between the ridges 17. The free polygonal end 12a of the extension 12 projects axially by a distance e beyond the free ends of the wings 15.

The screw 2 is provided with a head 19 in which an axial housing 21 is recessed or formed with a polygonal cross-section that is complementary to the polygonal cross-section 13 and opens on both sides into two radial slots 22 that are arranged diametrically opposite one another. This means more precisely that the cross-section of the free surface 12a of the projection 12 is slightly smaller than the cross-section of the housing 21 so that the projection 12 can penetrate there until it is firmly seated on the walls of the housing 21 due to the friction of the ridges 17.

Preferably, the axial receptacle 21 is hexagonal in shape, with the walls in this design running parallel to the screw axis and the edges lying parallel to one another in pairs.

Due to the small dimensions of the screw 2 and, in addition, the special conditions of the environment of an operating field, it is necessary to hold the screw at the end of the screwdriver 1, which also has its reasons in the convenience and simplicity of the work.

Holding the screw via its polygonal recess 13 is sufficient for the user of the screwdriver 1 to achieve a good temporary fastening of the screw to the screw

Landan-ger-liandos et al GP8770DE

screwdriver and can exert its rotational action without the screw deviating from the extension of the screwdriver axis.

The screw is therefore mechanically held to the screwdriver by a press fit in a sufficient manner to allow it to be screwed in properly, but at the same time to allow the screwdriver 1 to be easily separated from the screw 2 once it has been screwed in.

The shaft 3 may preferably be made of stainless steel Z4 0 CD15, which is hardened and tempered and has a strength substantially of 51/53 HRC, which corresponds to a mechanical breaking strength of approximately 200 kg/mm ² .

The screw 2 can be made of TAGV titanium. The appendix 12, which is formed by electroerosion in one piece with the rest of the shaft 3, thus has a higher mechanical strength or resistance than the screw 2 which, if made of titanium, breaks under a force or moment of about 0.450 Nm.

As a non-limiting numerical example and to illustrate the difficulties of handling microscrews in general and microscrews in the specific surgical field, the following approximate values are given:

- Outside diameter of the thread of screw 2: 2 to 3mm,

- Outside diameter of head 19: 3 to 4mm,

- Total length of screw 2: 5 to 10mm,

- Dimension of the hexagonal recess 21 measured over the distance separating two parallel sides of the recess: 1.5 to 2 mm.

The geometry of the lug 12 described above, the fact that it is made in one piece with the rest of the shaft 3 and the appropriate strength of the latter give the lug 12 a mechanical resistance such that any risk

I !.. 5 1 &iacgr; ·

Landanger-Landos et al GP8770DE

deformation of the attachment and the wings 15 is prevented even under extreme forces and moments under the circumstances of a surgical procedure.

After the projection 12 has been partially inserted into the housing 21 and the wings 15 into the slots 12 of the screw 2, which are firmly connected to the screwdriver 1, the surgeon places the handle 4 in the palm of his hand so that he holds it with the middle finger, the ring finger and the little finger, which makes it possible to screw in the screw by rotating the insert 5 and the shaft 3 with the thumb and the index finger to an appropriate torque. The insert 5 can rotate freely with respect to the handle 4, but is held axially thereto. The ergonomic shape of the handle 4 makes this handling considerably easier.

The design according to the invention allows a good cooperation between the screw 1 and the screwdriver 2 thanks to the conical holding part 14, which has a conicity directed outwards from the screwdriver. This conical part 14 ensures that it wedges itself with the walls between the edges of the recess 21 of the screw when the screwdriver 1 is inserted into the recess of the screw.

It may happen, in the circumstances of a surgical operation, that the screwdriver is introduced at an angle in order to place the screw 2. The lug 12 can then absorb a very high torsional moment without risk of deformation, in particular at the wings 15, and thanks to the special design and the fact that it is made in one piece with the rest of the shaft 3, the elastic limit of the metal is never reached. A lug made in one piece with the rest of the shaft of the screwdriver always gives the tool sufficient strength.

In a special embodiment, the disk is

Landanger-L'andos et al GP8770DE

The conical part 14 preferably has a vertex angle of between 3 and 6°: good holding results with good detachability are obtained in particular with a conicity with a vertex angle of 5°.

The design according to the invention can be implemented in various variants. For example, the cross section of the extension 12 can be octagonal or square.

Assembly of a screwdriver and a screw for maxillofacial microsurgery. The free end of the shaft 3 of the screwdriver carries an axial projection 12 with a polygonal cross-section 13 and a conical longitudinal section 14 and radial wings 15 on both sides of the projection, the projection and the wings being formed in one piece with the rest of the shaft. The screw is provided with a head in which an axial receptacle is formed with a polygonal cross-section complementary to the cross-section of the projection and opening into two lateral radial slots on both sides. The receptacle and the slots are designed to receive the projection and the wings in such a way that when the projection is inserted into the receptacle of the head of the screw, friction ensures that the screw is held by the screwdriver. The shaft is made of a material with a suitable strength so that the shaft 3 in conjunction with the design of the attachment 12 has sufficient mechanical resistance so that any deformation of the wings 15 is avoided even in the case of extreme torques applied to the screw 2. Such an arrangement is used in traumatological or corrective jaw-facial surgical procedures.

Claims (8)

Landanger-L'andos et al GP8770DE - 10 - Protection claims 1. Arrangement of a screwdriver (1) and a corresponding screw (2), in particular for traumatological or corrective jaw-facial surgery, characterized in that the free end of the shaft (3) of the screwdriver has an axial shoulder (12) with a polygonal cross-section (13) and a conical longitudinal section (14) as well as radial wings (15) on both sides of the shoulder, and in that the screw is provided with a head (19) in which an axial seat (21) is formed with a polygonal cross-section that is complementary to that of the shoulder and that opens into two lateral radial slots (22) on both sides, the receptacle and the slots being designed in such a way that they can receive the shoulder and the wings and the insertion of the shoulder into the receptacle of the head of the screw via a press fit ensures that the screw is held by the screwdriver, the shoulder (12) and the wings (15) being in a piece with the rest of the shaft (3). 2. Arrangement according to claim 1, characterized in that the conical part (14) of the attachment (12) passes over rounded grooves (18) into the shaft (3) of the screwdriver (1). 3. Arrangement according to claim 2, characterized in that the shaft (3) has a strength of approximately 51/53 HRC, which corresponds to a breaking strength of approximately 200 kg/mm ² . 4. Arrangement according to claim 3, characterized in that the cross section (13) of the projection (12) and the receptacle (21) of the head (19) of the screw is hexagonal. * ', I.« * &Sgr; *«* ♦ * ♦♦♦ Landanger-L'andos et al GP8770DE - 11 - 5. Arrangement according to one of claims 1 to 4, characterized in that the screwdriver (1) has an ergonomic handle consisting of two complementary longitudinal elements, and in that one of the elements (4) forms the handle proper, is mounted so as to rotate freely with respect to the second element (5) and is intended to be held in the palm of an operator, while the other element is an intermediate insert (5) forming the active part fixed to the shaft (3) of the screwdriver, which insert is longer than the first-mentioned element (4) forming the handle and can be gripped by the operator's fingers in order to rotate the shaft (3) for screwing. 6. Arrangement according to claim 5, characterized in that the insert (5) is fastened with an axial screw (6) which sits in a sleeve (7) inside the handle and is freely rotatable therein and that abutment devices are provided to hold the screw axially in the sleeve. 7. Arrangement according to claim 6, characterized in that the abutment means consist of a radial inner projection (9) provided on the inner wall of the sleeve (7) between the head (6a) of the screw (6) and the end of the insert (5), the sleeve being fixed in the handle (4) for example by means of a transverse pin (11). 8. Arrangement according to one of the preceding claims, characterized in that the conical longitudinal section (14) has an apex angle of between approximately 3 and 6°, in particular of 5°.