Abstract:
An instrument for use on a body site is provided comprising a bushing having portions, a coolant source, and a bore, wherein the instrument may be used to introduce an implant, instrument, or tool to a body site. After the implant, instrument, or tool is introduced to a body site, at least one portion of the bushing may be removed. A method of use for the instrument is also provided. A kit including the instrument is further provided.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of the U.S. national phase designation of co-pending international application PCT/CH02/00011 to Hontzsch et al., filed Jan. 9, 2002, the entirety of which application is hereby incorporated by reference thereto. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a device for osteosynthetic purposes, especially for drilling, cutting threads or inserting implants in a bone. 
     BACKGROUND OF THE INVENTION 
     A drill guide bushing, which can be used for osteosynthetic purposes and especially for drilling, cutting threads or inserting implants, is known from International Application No. WO 96/20650 to Frigg. This known drill guide bushing includes a bushing, the front end of which can be bought into contact with a bone and through the rear end of which an instrument or implant can be introduced. Furthermore, this known drill guide bushing, in the region of the rear end, includes a coolant connection, through which coolant can be introduced into the drill guide bushing. It is a disadvantage of this known device that, when a bone screw is inserted, it cannot be guided at the screw shaft in the borehole of the drill guide bushing, as otherwise the drill guide bushing can no longer be removed from the bone screw because the head of the bone screw is larger in diameter. 
     SUMMARY OF THE INVENTION 
     The invention provides a remedy to this problem. It is an object of the invention to create a device, with which even a screw with a head having a diameter larger than that of the shaft, can be introduced into the cavity and the device can be removed from the implant after the screw has been screwed in. 
     The inventive device comprises essentially a drill guide bushing, which is divided over the whole of its length L parallel to the longitudinal axis and has a cavity and a coolant connection, which is connected with the cavity. Due to the divided construction of the drill guide bushing, it can be achieved that after a screw is brought through the cavity to the front end of the drill guide bushing and screwed in, the shells of the divided drill guide bushing can be shifted relative to one another transversely to the longitudinal axis. With that, the cavity of the drill guide bushing can be opened and the drill guide bushing can be pulled away over the head of the screw, which is larger in diameter. 
     In a preferred embodiment of the inventive device, the cavity tapers towards the front end of the drill guide bushing, so that the shaft of an inserted screw may be passed through the cavity wall at the front end of the drill guide bushing. The cavity may, for example, be tapered conically. 
     The drill guide bushing can be divided into two half shells, the contacting surfaces of which lie in planes which are parallel to one another and to the longitudinal axis. In an alternative embodiment of the inventive device, the contacting surfaces of the two half shells are tiered, the contacting surfaces of the first-half shell having elevations and the contacting surfaces of the second half shell having depressions, which are complementary to the elevations. Due to the elevations and depressions, which are disposed axially so that they engage one another when the drill guide bushing is closed, the leakproofness of the drill guide bushing can be increased, and the stability, which prevents displacement of the half shells relative to one another and parallel to the contacting surfaces, can also be increased. 
     Furthermore, in another alternative embodiment, the inventive device includes a holding grip, which may be fork-shaped with two rods. At one end of the holding grip, the two rods are connected with one another and, at the other end of the holding grip, each rod is connected with a different half shell of the drill guide bushing. Due to this configuration of the holding grip, the half shells can be moved relative to one another, so that the drill guide bushing can be opened or closed. 
     In another alternative embodiment, the inventive device includes an inner drill guide bushing, which can be introduced into the cavity. The central borehole of the inner drill guide bushing is configured so that a drill can be centered and guided, and after the inner drill guide bushing has been removed, thread-cutting tools can be passed through the cavity. 
     In a further alternative embodiment, the inventive device includes a trocar for centering the drill guide bushing in a plate borehole, for example, at a bone plate. The diameter of the trocar may be such that the trocar, when the inner drill guide bushing is removed, can be passed through the cavity wall of the drill guide bushing. The diameter of the trocar may also be such that the trocar can be introduced directly into the central borehole of the inner drill guide bushing. This particular configuration of the trocar, may eliminate the need to exchange the inserts when, for example, a bone screw is implanted. After the drill guide bushing is centered by means of the trocar, the latter can be pulled out of the central borehole of the inner drill guide bushing and the drill can be introduced into the central borehole. After the drilling process is concluded, the inner drill guide bushing can be removed from the cavity of the drill guide bushing and the thread-cutting tool can be inserted into the cavity of the drill guide bushing. 
     It may be preferable that the front end of the drill guide bushing is configured so that the drill guide bushing is tapered at the front end. This tapering may be configured conically or rounded-off and enables the front end of the drill guide bushing to be centered in a borehole or the screw heads to be countersunk, for example, in a bone plate more easily. 
     The inventive device therefore has the following advantages: during the surgical intervention, the drill guide bushing can be centered, for example, in a screw hole of a bone plate, so that it is prevented from slipping to the side during the intervention; a trocar can be introduced into the cavity of the drill guide bushing; a length measurement can be carried out through the drill guide bushing; the inner drill guide bushing or the trocar protrude at the front end of the drill guide bushing, so that a plate hole can be identified by touch; and a screw is trapped in the cavity until the two half shells of the drill guide bushing are opened. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention and further developments of the invention are explained in greater detail in the following by means of partially diagrammatic representations of several examples. In the drawings, 
         FIG. 1  shows a side view of an embodiment of the inventive device; 
         FIG. 2  shows a plan view of the embodiment of  FIG. 1 ; 
         FIG. 3  shows a cross-sectional side view of an alternative embodiment of the inventive device together with an inner drill guide bushing; 
         FIG. 4  shows a cross-sectional side view of an alternative embodiment of the inventive device together with a trocar; 
         FIG. 5  shows the device of  FIG. 3 , into which a trocar has been inserted; and 
         FIG. 6  shows a cross-sectional side view of an alternative embodiment of the inventive device with an insert at the front end. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 and 2  show the inventive device as a drill guide bushing  1 , which is divided over its whole length L, with two half shells  3 ,  4 , the contacting surfaces  12 ,  13  of which, extending parallel to the longitudinal axis  2 , can be inserted in one another. An instrument or an implant can be inserted coaxially with the longitudinal axis  2  into the cavity  11  from the rear end  6  of the drill guide bushing  1 . The cavity  11  is also open at the front end  5  of the drill guide bushing  1 , so that when the front end  5  of the drill guide bushing  1  is placed against a bone or an implant, the drill guide bushing  1  can be used to guide a drill or another instrument axially displaceably in the cavity  11 . A holding grip  9  and a coolant connection  10  are mounted at the rear segment  8 , which adjoins the rear end  6  of the drill guide bushing  1 . A coolant can be passed through the coolant connection  10  directly into the cavity  11  in the drill guide bushing  1 , so that a drill, for example, can be cooled. The contacting surfaces  12  of the first half shell  3  have elevations  14 , which are parallel to the longitudinal axis  2  and can be inserted into the complementary depressions in the contacting surfaces  13  of the second half shell  4 . The fork-shaped holding grip  9  comprises two rods  16 ,  17 , which are connected with one another at the first end  18  of the holding grip  9 , and connected with a half shell  3 ,  4  at the second end  19  of the holding grip  9 . The half shells  3 ,  4  may be removed from one another by pushing the rods  16 ,  17  apart and the drill guide bushing  1  is divided parallel to the longitudinal axis  2 . On the other hand, when the rods  16 ,  17  are pushed together, the half shells  3 ,  4  can be joined together at their contacting surfaces  12 ,  13 , so that the drill guide bushing  1  is closed. In the embodiment shown here, the front end  5  of the drill guide bushing  1  is constructed so that the front end  5  of the drill guide bushing  1  can be inserted into a depression of an implant (not shown), which is used to accommodate the screw head of a bone screw. This can ensure an accurate fit, whereby the centering of the drill guide bushing  1  can be attained via the depression in a bone plate. The cavity  11  is tapered towards the front end  5  by a cone  29  in the front segment  7  of the drill guide bushing  1 . Because the cavity  11  tapers towards the front end  5  of the drill guide bushing  1  and because of the convex configuration of the front end  5  on the outside at the drill guide bushing  1 , the compressed half shells  3 ,  4  are not jammed between the depression in the plate and the bone screw as the latter is screwed in. In the embodiment of the inventive device shown here, three cones are mounted at the front end  5  of the drill guide bushing  1 . They adjoin one another axially, are coaxial with the longitudinal axis  2 , and due to their different conical angles, provide a convex configuration of the front end  5  of the drill guide bushing  1 . These cones are suitable for centering the front end  5  of the drill guide bushing  1  in a depression for accommodating a screw head at a bone plate. Due to this configuration of the front end  5  of the drill guide bushing  1 , the latter does not slip out of the depression for the screw head if, for example, the two half shells  3 ,  4  are separated slightly during the determination of the screw length, so that the centering of the front end  5  is maintained. 
     The drill can be cooled during the drilling process. This is facilitated by a coolant container  22 , the opening  23  of which can be connected to the coolant connection  10  at the drill guide bushing  1 . The length of the bone screw, protruding over the plate, can be determined through the cavity  11 . For screwing the bone screw in completely, the two half shells  3 ,  4  are separated, so that the screw head at the front end  5  of the drill guide bushing  1  fits through the tapered cavity  11 . As long as the screw is not screwed through the opened front end  5  of the drill guide bushing  1 , the latter can be taken out once again with the drill guide bushing  1  closed without the possibility of losing the screw in the soft parts. Two grooves  26  are provided at the front end  5  of the drill guide bushing  1  in the cavity  11  of the drill guide bushing  1 . When viewed parallel to the contacting surfaces  12 ,  13  and perpendicularly to the longitudinal axis  2  of the drill guide bushing  1 , these grooves  26  extend parallel to the contacting surfaces  12 ,  13  and are divided symmetrically in their length by the contacting surfaces  12 ,  13 . Viewed perpendicularly to the contacting surfaces  12 ,  13 , the grooves  26  extend at an angle to the longitudinal axis  2 , this angle being smaller than half the conical angle of the cone  29 , so that the depth of the grooves  26  decreases from the front end  5  in the direction of the rear end  6  of the drill guide bushing  1  and the grooves  26  taper off in the cone  29 . Because of these two grooves  26 , the half shells  3 ,  4  need only be separated slightly for determining, for example, the screw length. For this reason, the front end  5  of the drill guide bushing  1  is less likely to slip out of the depression of the plate hole and that subsequently the depression can be found only with difficulty, if at all, due to the soft parts. 
       FIG. 3  shows the device of  FIG. 1  with a hollow cylindrical inner drill guide bushing  20 . The inner drill guide bushing  20  can be inserted coaxially with the longitudinal axis  2  from the rear end  6  of the drill guide bushing  1  into the cavity  11 . In the inserted state, the inner drill bushing  20  protrudes beyond the front end  5  of the drill guide bushing  1 . During the drilling process, the inner drill guide bushing  20  is inserted into the two-part drill guide bushing  1 . While drilling, coolant can be injected from the coolant container  22  into the drill guide bushing  1 . The coolant is pressed through an annular groove  30 , which is mounted level with the coolant connection  10  at the outside of the inner drill guide bushing  20 , and enters the inner drill guide bushing  20  through boreholes  31 , which are disposed radially with respect to the longitudinal axis  2  in the annular groove  30  and extend into the central boreholes  32  of the inner drill guide bushing  20 . The coolant passes through the central boreholes  32  along the drill to the front end  5  of the drill guide bushing  1  and to the tip of the drill, 
       FIG. 4  shows the inventive device with a drill guide bushing  1 , as shown in  FIG. 1 , together with a trocar  25 . The trocar  25  includes a cylindrical shaft  27  with a tip  24  at its front end and a holding grip  28  at its rear end. For centering the drill guide bushing  1 , the trocar  25  is introduced from the rear end  6  of the drill guide bushing  1  into the cavity  11  until the tip  24  of the trocar  25  protrudes beyond the front end  5  of the drill guide bushing  1 . 
     During the surgical procedure, the drill guide bushing  1  is guided by a stab incision through the soft parts onto the plate (not shown), which has been pushed underneath. The drill guide bushing  1  and the trocar  25  can be guided selectively to the plate hole with the tip  24  of the trocar  25 , which protrudes over the front end of the drill guide bushing  1 . After the plate hole has been found, the drill guide bushing  1  is introduced with its front end  5  into the depression at the plate hole and is centered by the latter. For the embodiment of the drill guide bushing  1  and the trocar  25  shown here, the trocar  25  is removed from the drill guide bushing  1  after the latter is centered in the depression at the plate hole and the inner drill guide bushing  20  is introduced, so that the drill can be introduced into the central borehole  32  of the inner drill guide bushing  20  and the hole can be drilled. Subsequently, the inner drill guide bushing  20  is removed from the cavity  11  in the drill guide bushing  1  and the thread is cut through the cavity  11  in the drill guide bushing  1 . 
     A different embodiment of the inventive device is shown in  FIG. 5 . The possibility exists here of introducing the trocar  25  into the central borehole  32  of the inner drill guide bushing  20 , so that the tip  24  of the trocar  25  protrudes from the central borehole  32  at the front end  5  of the drill guide bushing  1  and protrudes beyond the front end  5 . It can therefore be achieved that after the device is centered, only the trocar  25  has to be pulled out of the central borehole  32  of the inner drill guide bushing  20 , after which the drill can be introduced into the central borehole  32  and the hole can be drilled. Subsequently, the inner drill guide bushing  20  is removed from the cavity  11  of the drill guide bushing  1  and the thread is cut. 
     A further embodiment is shown in  FIG. 6 . An insert  33 , which can be shifted coaxially to the longitudinal axis  2 , is disposed at the front end  5  of the 2-part drill guide bushing  1 . The insert  33  is in the form of a sleeve and includes a concentric collar  34 . The axial displaceability of the insert  33  is limited owing to the fact that the collar  34  can be moved axially in the drill guide bushing  1  only between a rear stop  37  and a front stop  38 . Springs  35 , by means of which the insert  33  is pressed against the front end  5  of the drill guide bushing  1 , are disposed between the rear stop  37  and the collar  34  parallel to the longitudinal axis  2 . Furthermore, the front end  36  of the insert  33  is serrated. 
     While the invention has been shown and described herein with reference to particular embodiments, it is to be understood that the various additions, substitutions, or modifications of form, structure, arrangement, proportions, materials, and components and otherwise, used in the practice and which are particularly adapted to specific environments and operative requirements, may be made to the described embodiments without departing from the spirit and scope of the present invention. Accordingly, it should be understood that the embodiments disclosed herein are merely illustrative of the principles of the invention. Various other modifications may be made by those skilled in the art which will embody the principles of the invention and fall within the spirit and the scope thereof.