Abstract:
The invention relates to an aiming, or targeting, device which is used to guide and place longitudinal bone fixing means in a predetermined direction with respect to a bone fixing device. The aiming device includes securing means, which can be detachably secured to a bone fixing device, a first centering part, which can be placed on the bone fixing device, and a second centering part, which is arranged at a distance from the first centering part. Both of the centering parts include at least one pair of guiding elements which are arranged in a coaxial manner in relation to each other.

Description:
RELATED APPLICATION DATA 
     The present application is a continuation of the U.S. National Stage designation of co-pending International Patent Application No. PCT/CH2003/000467 filed Jul. 14, 2003. the entire content of which is expressly incorporated herein by reference thereto. 
     FIELD OF THE INVENTION 
     The invention relates to a targeting device for use with bone fixation devices. 
     BACKGROUND OF THE INVENTION 
     In the case of bone fixation devices, particularly bone plates, the problem arises of fastening these devices by means of suitable, longitudinal bone fixation means, such as bone screws, bone wires, bone pins or Kirschner wires, to the bone fragments, so that the longitudinal bone fixation means have a particular direction with respect to the bone fixation device, especially, a specific angle to the bone fixation device. This problem arises principally in the case of bone plates, which consist of a plastic and do not yet have any plate boreholes, for example, the bone plate of International patent publication WO 01/012081. 
     A device with a centering sleeve for setting the bone fixation means at a plastic plate is known from the German publication DE-U 200 19 026. This known device comprises a targeting bracket, at which a bone plate can be attached by fastening means, and a guiding part, which can be shifted at the targeting bracket and shifted and rotated relative to the bone plate. The single guiding part is tubular in construction and serves to center and guide surgical instruments and/or implants. The tubular configuration of the guiding part permits only one bone fixation means to be accommodated. In the event that, for example, several Kirschner wires are to be set at one bone plate, the guiding part must be shifted and aligned once again with respect to the targeting bracket for each Kirschner wire, which is to be set. This results in the expenditure of much time for setting, for example, four Kirschner wires. 
     The invention is to provide a remedy here. It is an object of the invention to create a targeting device, which, on the one hand, permits drilling instruments or drill guide sleeves to be positioned in a previously determined direction with respect to the bone and/or, on the other, permits the surgeon to bring longitudinal bone-fixation means (Kirschner wires) into the bone in a previously determined direction, preferably in a direction in which they diverge from one another. 
     SUMMARY OF THE INVENTION 
     Pursuant to the invention, this objective is accomplished by a targeting apparatus for guiding fixation elements relative to a bone fixation device comprising a targeting bracket formed of a connecting portion having a first end and a second end, the first end configured and dimensioned for attachment to the bone fixation device, e.g., bone plate, and a handle portion disposed at the second end of the connecting portion. A first centering part is disposed at the first end of the connecting portion, the first centering part having a first guide for aligning a longitudinal bone fixation element relative to the bone fixation device. A second centering part is disposed on the handle portion, spaced from the first centering part, the second centering part having a second guide for aligning a longitudinal bone fixation element relative to the bone fixation device, and n the first and second guides are coaxial with one another and form a first guide pair. 
     The advantages, achieved by the invention, are to be seen essentially therein that, due to the inventive targeting device:
         the longitudinal bone fixation means can be positioned precisely by the surgeon without previously having to implant a Kirschner wire in the bone;   the position of the Kirschner wires is predetermined clearly by the surgeon without previously having to implant a Kirschner wire in the bone;   the position of the Kirschner wires is predetermined clearly by the anatomy of the humerus and the position selected underneath the axillary nerve and becomes reproducible due to the targeting device (this is not the case with a targeting device, which permits the user to select the positioning freely); and   the bone fixation element can be implanted as well as explanted.       

     In a preferred embodiment, the two centering parts have at least two pairs of mutually coaxial guides. Each pair of guides comprises a guide in the first centering part, which is disposed at the front end of the targeting bracket and can be connected with the bone fixation device, and a guide in the second centering part, which is disposed at the handle of the targeting bracket. Preferably, the pairs of guides are constructed so that the axes of the different pairs of guides diverge. By these means, the advantage can be achieved that several bone fixation means (Kirschner wires) can be implanted without having to adapt and adjust the targeting device once again to the directions of the individual Kirschner wires. Preferably, the bone fixation device is constructed as a bone plate. 
     In a different embodiment, the two centering parts and the targeting bracket are constructed so that the two centering parts at the targeting device are exchangeable. By these means, the further advantage can be obtained that the guiding pairs or longitudinal bone fixation agents can be set at angles determined in advance, for example, with respect to a bone plate, by one set of centering pairs with different orientations. 
     In yet another embodiment, the guides are fixed with respect to the centering parts, so that undesirable shifting of the guides relative to the centering parts is not possible. 
     In a further embodiment, the centering parts can be connected with the targeting device only in a position defined with respect to the targeting device. On the one hand, errors in the installation of the targeting device can be excluded by this configuration and, on the other, the positions of the two centering parts can be found easily, as a result of which the installation of the targeting device is simplified appreciably. 
     In yet another embodiment, the targeting device comprises a two-part targeting bracket with a sleeve, suitable for accommodating the fastening means between the targeting bracket and the bone fixation means and a handle part disposed transversely to the central axis. Preferably, the first centering part is connected firmly with this sleeve, the sleeve being secured relative to the handle part against twisting about the central axis of the sleeve. 
     In a different embodiment, the guides in the second centering part, disposed at the handle part of the targeting bracket, are constructed as boreholes, so that the drill guide sleeves or bone fixation means, which can be introduced into the boreholes, are enclosed on the whole of the periphery and cannot be shifted laterally. The guides in the first centering part, which can be fastened, for example, to a bone plate, preferably are constructed as centering grooves, which are coaxial with the axes of the boreholes. 
     In yet another embodiment, the targeting device comprises one or more boreholes for accommodating longitudinal targeting aids, which preferably are constructed in the form of aiming stakes and make it easier for the surgeon to align the targeting device at the body of the patient. 
     The bone plates used preferably are made from PEEK, an implantable plastic with very good mechanical properties. The plate is provided with a central borehole, which is used for temporarily fixing the targeting instrument at the plate. However, due to the conical internal thread (which fits the head locking screws) in the borehole, a corresponding bone screw can also be fixed therein after the Kirschner wires have been positively located and the targeting instrument removed, in order to anchor the bone plate additionally with the bones. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in even greater detail in the following by means of the partly diagrammatic representation of an example, in which: 
         FIG. 1  shows longitudinal sections through an embodiment of the inventive targeting device. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An example of the inventive targeting device  1  is shown in  FIG. 1 . It comprises a two-part targeting bracket  2 , a first and a second centering part  13 ,  3  for accommodating and guiding bone fixation elements  4 , such as Kirschner wires and a fastening agent  5 , which can be fastened at a bone plate  6 . 
     The two-part targeting bracket  2  consists of a longitudinal, hollow cylindrical sleeve  8  with a central axis  9  and a handle part  7 , which can be fastened at the rear end  11  of the sleeve  8  by means of a screw  10  and is disposed transversely to the central axis  9 . The first centering part  13  is mounted at the front end  12  of the sleeve  8  and comprises guides  14 , which are disposed skew with respect to the central axis  9  and are in the form of centering grooves for the bone fixation elements  4 , so that the bone fixation elements  4 , before they penetrate into the bone plate  6 , are passed through the guides  14  of the first centering part  13 . The central borehole  15  of the sleeve  8  also passes through the first centering part  13 , so that the fastening agent  5 , which is also cylindrical, can be passed through the central borehole  15  coaxially with the central axis  9 . The sleeve  8  is locked in place at the handle part  7  so that it cannot rotate about the central axis  9 . Security against rotation  34  is realized by the screw  10 , which can be screwed into the handle part  7  and the tip  35  of which can be taken up in a depression  36  at the sleeve  8 , so that, after the screw  10  is locked in place, the sleeve  8 , together with the centering part  13 , is immobilized in the handle part  7 . 
     The tip  16  of the fastening agent  5  is provided with an external conical thread  17 , which can be screwed into a complementary internal thread  18  in the borehole  40  provided in the bone plate  6 . By means of a nut  21 , which can be screwed over an external thread  20  provided at the rear end  19  of the fastening agent  5  and rests on the handle part  7 , the fastening agent  5 , together with the bone plate  6 , is fastened to the targeting bracket  2 . 
     The second centering part  3  is constructed as a rectangular block and provided at its side surfaces  22 , which are directed toward the targeting bracket  2 , with three spherical depressions  23 , whereas the targeting bracket  2 , at its side surface  24  directed against the second centering part  3 , has three spherical elevations  25 , which are complementary to the depressions  23 . The second centering part  3  is secured against twisting relative to the targeting bracket  2  by the elevations  25 , which engaged the depressions  23 . The second centering part  3  is fastened by means of a screw  26 , which can be screwed into a corresponding borehole  27  in the second centering part  3  having an internal thread and the screw head  28  of which lies in contact with the handle part  7 . Furthermore, the second centering part  3  comprises four guides  29  in the form of boreholes, which pass through the second centering part  3  transversely to the central axis  9  and the axes  30  of which extend transversely to the central axis  9  and are skew relative to one another. The guides  29  are disposed so that their axes  30  are aligned with the guides  14  in the first centering part  13 , which are constructed as centering grooves, so that the bone fixation elements  4 , when pushed through the guides  29 , are guided in the guides  29 , which are disposed remote from the bone plate  6 , as well as in the guides  14 , which are located close to the bone plate  6 . 
     Furthermore, boreholes  31  for accommodating targeting aids  32 ,  33  in the form of aiming stakes are mounted at the centering part  3  as well as at the handle part  7 . The boreholes  31  are aligned so that the first targeting aid  32 , which can be mounted at the handle part  7 , is perpendicular to the central axis  9 , while the second targeting aid  33 , which can be mounted at the centering part  3 , is aligned in the direction of the line connecting the centering part  3  and the centering part  13 . The targeting aids  32 ,  33  enable the surgeon to align the targeting device  1  with respect to the bone that is to be treated. 
     The use and function of the inventive targeting device is described in greater detail below by means of the surgical method for the proximal humerus: 
     A) Implantation: 
     To begin with, the fractured, proximal humerus is repositioned roughly over the soft parts. 
     2-3 cm skin incision underneath the axillary nerve at the proximal humerus; 
     Prepare the way bluntly with the index finger up to the shaft. 
     Guide the targeting device with the mounted plate up to the shaft and position it appropriately with the help of the external targeting wires. 
     Anchor the targeting device in the specified position at the shaft of the humerus with a 2.5 mm K wire. 
     Introduce the drill guide bushing into the marked borehole in the targeting instrument and advance up to the plate with a movement, oscillating circularly about the longitudinal axis. 
     Introduce 2.0 mm spiral drill. Before the drilling process, check once more the alignment of the targeting instrument along the longitudinal axis and, if necessary, correct. If the position along the longitudinal axis and the height are correct, the cortex in the shaft region is bored. 
     Remove 2.0 mm drill and introduce first 2.5 mm K wire up to the fracture line. Leave drill guide sleeve in the targeting instrument and use the second drill guide sleeve for the next Kirschner wire. 
     Use same procedure (pre-bore and introduce the K wire up to the fracture line) for the remaining three K wires. 
     Definitive reposition of the fracture and subsequent threading of Kirschner wires into the end position selected by the surgeon. 
     Remove targeting device from the plate. 
     Sever the protruding ends of the Kirschner wires with the trimming device as close as possible to the plate surface. 
     The ends of the Kirschner wires now protrude approximately 8-10 mm from the plate surface. 
     End of osteosynthesis. 
     B) Explantation: 
     2-3 cm skin incision below the axillary nerve at the proximal humerus. 
     Prepare the way bluntly with the index finger up to the shaft. 
     Guide the targeting device up to the plate and fix once more to the plate with the fastening screw. 
     Introduce the extraction bolt into the targeting device up to the end of the Kirschner wire. 
     Rotate extraction bolt counterclockwise and remove the Kirschner wire manually. Follow same procedure for the remaining Kirschner wires. 
     Remove the targeting device. 
     End of the explantation. 
     While the present invention has been described with reference to the preferred embodiments, those skilled in the art will recognize that numerous variations and modifications may be made without departing from the scope of the present invention. Accordingly, it should be clearly understood that the embodiments of the invention described above are not intended as limitations on the scope of the invention, which is defined only by the following claims.