|Title of Invention
|The invention relates to a clamping device for clamping a longitudinal fixing element (2), in particular a Kirschner wire. Said device consists of a screw (3) of height H, at least partially configured from a truncated cone and comprising a cone axis (4) and a conical outer surface (5) with a thread (6), a continuous bore (7) that is coaxial with the cone axis (4) and that houses the longitudinal fixing element (2), a rear end (8) containing means (9) for turning the screw (3) and a front end (1). The front end (1) of the screw (3) is provided with at least one longitudinal slot (10) of length L, which extends radially into the continuous bore (7) in such a way that the screw (3) can be at least partially compressed in a radial direction.
The invention concerns a clamping device according to the preamble of patent claim
There is a need in paediatrics to treat fractures in the vicinity of the growth joint, without injuring the growth joint at the same time; otherwise the bone cannot keep growing. 10 Therefore instead of bone screws usually used in osteosynthesis so called Kirschner wires are used for this purpose. They have a very small diameter and therefore result only in marginal damages, if an injury of the growth joint occurs at all. The disadvantage of this surgical technique is, however, that using a Kirschner wires on its own the bone fracture cannot be compressed. For this reason implants have been constructed, in 15 which by means of a grubscrew a small ball is fastened on the implanted Kirschner wire at right angle to it, so that the final position of the Kirschner wire will be secured. The grubscrew, situated in the ball, is tightened by means of a tool that is firmly joined with the grubscrew via a predetermined breaking position. After the fixing has been carried out, the tool breaks off as determined, so that the fi xing and positioning of the ball no longer can be reversed .
This is where the invention wants to provide remedy. The object of the invention is to produce a clamping device for the reversible clamping of a longitudinal fixing element, in particular of a Kirschner wire.
This invention achieves this objective by a clamping device having the features of claim 1.
The advantages achieved by the invention are that the clamping device together with the clamping ring is able to accommodate a Kirschner wire in its passing-through bores in an axially displaceable manner. In this case the Kirschner wire can be positioned in any desired position and secured in the clamping ring by screwing in the clamping device that can be compressed in its front region . In contrast to devices according to the state-of-the-art, this can be repeated many times if the position of the Kirschner wire is not satisfactory. Consequently the advantage is that no lateral clamping is carried out with a separate tiny grubscrew, but a direct axial clamping without additional components and, in addition, it is reversible.
When compared with the state-of-the-art, an additional advantage is that the clamping can be carried out along the axis of the Kirschner wire. According to the state-of-the-art the grubscrew has to be screwed in at right angle to the Kirschner wire, thus complicating the surgical technique and the manipulation.
The field of application of the clamping device is, however, not restricted to paediatrics, but is universal, it can also be used for the proximal end of the humerus.
In the case of a special embodiment the thread of the screw has two starts. This facilitates the screwing in of the screw because it engages the tapered bore and its matching internal thread faster than a screw with a single-start thread would.
In the case of another embodiment the front end of the screw is provided with three or for longitudinal slots, which are preferably equidistant from one another.
In the case of a further embodiment the clamping device comprises a clamping ring that comprises a central axis and a tapered bore extending coaxially with the central axis; the clamping ring is intended to accommodate the screw and radially compress it at least in the region of the front end.
In the case of a special embodiment the length L of the longitudinal slot is smaller than the overall height // of the screw and preferably L In the case of a further embodiment the inside wall of the passing-through bore of the screw is roughened or has a macroscopic structure. A better clamping effect is achieved by this.
The clamping device can also be used together with a bone plate having a plurality of holes in the plate, while at
least one of the holes in the plate has a tapered shape, suitable to accommodate the screw of the clamping
device and to radially compress it at least in the region of the front end. Thus instead of a bone screw a
kirschner wire is passed through the hole in the plate and fixed therein.
The invention and developments of the invention are explained in detail below, based on partly schematic illustrations of a plurality of embodiments.
They show in:
Fig.1 - a perspective view of the clamping device with a clamping ring, prior to clamping,
Fig.2- a longitudinal section through the clamping device with a clamping ring according to Fig. 1,
Fig.3- a longitudinal section through the clamping device with a Kirschner wire inserted therein after being clamped in the clamping ring, and
Fig.4- a longitudinal section through the clamping device with a bone plate and a Kirschner wire.
Fig.1 and 2 illustrate and embodiment of the clamping device, that comprises a screw 3 with a partly truncated cone shape having a taper axis 4 and a clamping ring 11 with a central axis 12. On the jacket surface 5 the screw 3 is provided with a tapered thread 6, has a passing-through bore 7, that is coaxial with the taper axis 4 and is radially flexible on a front segment by virtue of four longitudinal slots 10 with the length L, which extend essentially parallel with the taper axis 4. Measured from the front end 1 of the screw 3 the length of the longitudinal slots 10 is L, they are open at the front end 1 of the screw 3 and penetrate radially inward from the jacket surface 5 into the passing -through bore 7. Viewed in across-sectional plane of the screw 3, that is perpendicular to the taper axis 4, the, longitudinal slots 10 are symmetrically distributed on the circular wall of the screw 3.
The screw 3 further comprises at the rear end 8 a cylindrical segment, where the means 9 for screw 3 are accommodated, this means penetrating from the rear end 8 of the screw 3 coaxially with the taper axis 4. The means 9 for screwing in the screw 3 coaxially with the taper axis 4. The means 9 for screwing in the screw 3 are executed in this case as an internal hexagon, but it may have any shape.
As it is illustrated in Fig.1, the clamping ring 11, used in conjunction with the screw 3, is externally cylindrical and coaxial with its central axis 12 and comprises a tapered bore 13, that has an internal thread 16 matching the thread 6 of the screw 3. When screwing the screw 3 into the clamping ring 11, it will be radially compressed on its radially flexible segments with the length L by virtue of the truncated cone shape of the screw 3 and the matching taper-shaped bore 13, while the cross-section of the passing-through bore 7 at right angle to the taper axis 4 will also be reduced, so that a fixing element 2 (Fig .3), a Kirschner wire for example, clamped into th8 passing-through bore 7, will be fixed in the screw 7.
In Fig. 4 a truncated cone-shaped screw 3 is illustrated together with a bone plate 14 and a fixing
element 2, for example a Kirschner wire. The screw 3 is not different from the embodiments illustrated
in Figs.1 -3. Instead of the clamping ring 11 (Figs.1 -3), the clamping device according to this execution
comprises a bone plate 14, that has a plurality of tapered holes 15 in the plate with tapered internal
threads 20. The tapered internal threads 20 are matching the thread 6 on the jacket surface 5 of the screw 3, so that a screw 3 can be screwed into each of the holes 15 of the plate. Just like in the embodiment of the clamping device illustrated in Figs.1 -3, when screwing a screw 3 into a hole 15 of the plate, the truncated cone-shaped construction of the screw 3, together with the matching truncated cone-shaped hole 15 of the plate, radially compresses the screw 3 along its radially flexible segments having a length L.
Suitable ranges of the dimensions for the screw 3 and the corresponding structures of the clamping ring 11 and of the bone plate 14, respectively, for the various embodiments are listed below:
Height H of the screw: 3-7 mm,
Length of the longitudinal slots: 2.5-4.5 mm
Width the longitudinal 0.3-1 mm
Thickness of the jacket of the screw: conically from 0 to 4.0 mm of the passing-through 1.0-3.0 mm
Clearance between the passing-through bore and the Kirschner wire: 0-0.1 mm
• Taper: per: 15°-25°
Pitch of a two-start thread 0.6-1.1 mm, typically0.8 mm.
1. A clamping device to firmly clamp a longitudinal fixing element (2), in particular a Kirschner
wire, comprising a screw (3) with an at least partly truncated taper shape having an overall
height H with a taper axis (4) and a taper-shaped jacket surface (5) with a thread (6), a
passing-through bore (7) extending coaxially with the taper axis (4) to accommodate the
longitudinal fixing element (2), a rear end (8) with means (9) to screw in the screw (3) and a
front end (1), wherein the front end (1) of the screw (3) is provided with at least one
longitudinal slot (10) with a length L, the slot radially extending up to the passing-through
bore (7), so that the screw (3) can be compressed at least partly in the radial direction,
wherein the clamping device comprises a bone plate (14) with a plurality of holes (15) in the
plate, wherein at least one of the holes (15) in the plate has a tapered shape hole (13),
suitable to accommodate the screw (3) and radially compress it at least in the region of the
front end (1).
2. A clamping device according to claim 1, wherein the thread-has two starts."
3. A clamping device according to claim 1 or 2, wherein the front end (1) of the screw (3) is provided with three or four longitudinal slots (10) that are equidistant from one another.
4. A clamping device according to anyone of claims 1 to 3, wherein it '::w) : comprises a clamping ring (11) that comprises a central axis (12) and a tapered bore(13) extending coaxially with the central axis (12), the bore being suitable to accommodate the screw (3) and to radially compress it in the region of the front end (1 ).
5. A clamping device according to anyone of claims 1 to 4, wherein the length L of the longitudinal slot (10) is smaller than the overall height H of the screw (3) and preferably L
6. A clamping device according to anyone of claims 1 to 5, wherein the inside wall of the passing-through bore (7) of the screw (3) is roughened or has a macroscopic structure.
|Indian Patent Application Number
|PG Journal Number
|Date of Filing
|Name of Patentee
|EIMATTSTRASSE 3, CH-4436 OBERDORF, SWITZERLAND.
|PCT International Classification Number
|PCT International Application Number
|PCT International Filing date