Abstract:
The present invention relates to a device for fixation of bone fragments at bone fractures. The device comprises at least two fixation means ( 5, 6 ) and a securing plate ( 4 ). With the object of preventing or counteracting re-dislocation, the respective fixation means ( 5, 6 ) each have a first fixing portion ( 19 ) for fixing the fixation gleans in an inner bone fragment ( 3 ), a second fixing portion ( 21 ) for locking the fixation means to the securing plate ( 4 ) which is disposed on the outside of an outer bone fragment ( 2 ) and allows movement of the outer bone fragment relative to it, so that the fixation means are prevented from changing their angular position relative to the securing plate and relative to one another, and a middle portion ( 22 ) which is situated between the fixing portions and runs through the outer bone fragment, along which middle portion the outer bone fragment can slide inwards towards the inner bone fragment in which the fixation means is fixed.

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. Ser. No. 12/670,156, flied May 5, 2010, which corresponds to PCT/SE2008/050848, filed Jul. 8, 2008, which claims the benefit of Swedish Application No. 0701776-7 filed Jul. 24, 2007, the subject matter, of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND TO THE INVENTION 
     The present invention relates to a device for fixation of bone fragments at bone fractures. The device comprises at least two fixation means and a securing plate. 
     After a bone fracture such as a femur neck fracture, the bone fragments at the fracture need fixing. This is currently done by using suitable fixation means, e.g. bone nails or bone screws. 
     After the completion of surgery, even as early as when the effects of the anaesthesia have passed and the patient is still confined to bed, but above all when the patient is beginning to be up and walk and stand on the leg, the fixed bone fragments and the fixation means are subject to large forces, particularly to rotational forces downwards and rearwards. 
     The fixation means alone are often insufficient to counteract these rotational forces and the bone fragments have to be used to help to lock the fracture. If this is not done and the bone fragments are caused to rotate relative to one another by said forces, the result rill be shifting of the angular positions of the fixation means to such an extent that they risk substantially crossing one another, thereby keeping the fracture parted and preventing healing. 
     The object of the present invention is accordingly to prevent ear counteract this and therefore configure the device in such a way that the fixation means are not allowed to rotate and cross one another. 
     To this end, with the device according to the invention, each fixation means has a first fixing portion for fixing the fixation means in an inner bone fragment, a second fixing portion for locking the fixation means to the securing plate disposed on the outside of an outer bone fragment and allowing movement if the outer bone fragment relative to it, so that the fixation means are prevented from changing their angular position relative to the securing plate and relative to one another, and a middle portion which is situated between the fixing portions and runs through the outer bone fragment, along which middle portion the outer bone fragment can slide inwards towards the inner bone fragment in which the fixation means is fixed. 
     The result of the fixation means being thus fixed to the inner bone fragment and to the securing plate while the outer bone fragment can move towards the inner bone fragment and, in so doing, be guided by the fixation means is that the bone fragments are kept fixed but compression of the bone fragments is nevertheless allowed, the device and the bone fragments thus being able to absorb the aforesaid rotational forces and control them so that no re-dislocation occurs. The fixing of the fixation means in the inner bone fragment and the locking of the fixation means to the securing plate also reduce the risk of screws loosening in cases where the fixation means take the form of bone screws.) 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects and advantages of the invention will be apparent to one skilled in the art who examines the attached drawings and the following detailed description of preferred embodiments of and method for fitting the device according to the invention. 
         FIG. 1  illustrates in side view upper portions of a femur with a femur neck fracture and a device according to the present invention, showing a securing plate and a first guide sleeve usable in conjunction with said plate for guiding a guide wire drilled into gene fragments which are to be fixed on their respective sides of the fracture; 
         FIG. 2  illustrates in side view the removal of the guide sleeve for the guide wire; 
         FIG. 3  illustrates in side view a second guide sleeve for guiding a drill, and a gauge rod for determining how long the fixation means should be; 
         FIG. 4  depicts in side view the second guide sleeve after the removal of the gauge rod; 
         FIG. 5  illustrates in side view the insertion in the second guide sleeve of a drill, provided with a duct, for drilling a hole for a fixation means in the form of a bone screw and for drilling the hole for said bone screw in the bone fragments; 
         FIG. 6  depicts in side view the application of a further second guide sleeve for guiding a drill in the securing plate; 
         FIG. 7  illustrates in side view the further second guide sleeve after the application of a drill with a conical tip therein and the drilling of a second hole for a bone screw in the bone fragments; 
         FIG. 8  illustrates in side view the removal of the further second guide sleeve and the respective drill; 
         FIG. 9  depicts in side view the application of a fixation means in the form of a bone screw in the securing plate for further screwing of the bone screw into the second hole in the one fragments; 
         FIG. 10  illustrates in side view the bone screw when it has been screwed into the bone fragments; 
         FIG. 11  depicts in side view a second bone screw screwed into the first hole in the bone fragments after the guide wire, drill and guide sleeve have been removed; 
         FIG. 12  illustrates the securing plate with bone screws screwed firmly into the plate at an alternative five position; and 
       lastly  FIGS. 13 and 14  depict front views of two different alternative versions of the securing plate. 
     
    
    
     DESCRIPTION 
     The drawings illustrate one of several different methods for fixation of a fracture at the neck of a femur by means of a device according to the present invention. As previously indicated,  FIG. 1  depicts upper portions of a femur with a femur neck fracture  1 , and an outer bone fragment  2  and an inner bone fragment  3  on their respective sides of the fracture. A securing date  4  which forms part of the device according to the present invention for fixation means in the form of bone screws or bone nails, in the version depicted two substantially parallel bone screws  5 ,  6  (see  FIGS. 9-11 ) for fixing the bone fragments  4 ,  3 , is disposed on the outside of the outer bone fragment  2 . The respective bone screws  5 ,  6  are preferably integral. The securing plate  4  is so arranged that it allows movement of the outer bone fragment  2  relative to it, i.e. it is not connected to the outer bone fragment nor arranged in some other way whereby it would have moved with the latter upon compression of the bone fragments  2 ,  3 . In the femur, a guide wire  7  with a diameter of preferably about 2.4 mm has been drilled through the outer bone fragment  2  and into the inner bone fragment  3  under radioscopy and with guidance by a guide sleeve  8  with an inside diameter of preferably about 2.5 mm. The guide wire  7  is intended to guide a drill for drilling a hole for the bone screw  5  in the bore fragments  2 ,  3 . According to the invention, the guide sleeve  8  for the guide wire  7  is applied in the securing plate  4 , by preferably being screwed firmly in a threaded hole  9  running through the plate, and having for the purpose an externally threaded forward end portion  10  (see  FIG. 2  depicting the guide sleeve  8  when it has been unscrewed from the plate  4 ). This externally threaded forward end portion  10  does of course have an outside diameter corresponding to the diameter of the threaded hole  9  in the securing plate  4 , i.e. preferably about 9-10 mm. 
     After the removal of the guide sleeve  8  for the guide wire  7 , a second wide sleeve  11 , with an inside diameter of preferably about 6.5 mm and an externally threaded forward portion with the same outside diameter as the first guide sleeve, is applied in, i.e. screwed into, the threaded hole  9  in the securing plate  4  ( FIG. 3 ). This guide sleeve  11  is intended to guide a drill  13 , which has running through it a duct  12  for the wire guide  7  (see  FIGS. 5-10 ), for drilling the hole for the bone screw  5  in the bone fragments  2 ,  3 . When the second guide sleeve  11  has been attached to the securing plate  4 , a gauge rod  14  is inserted at the rear of this guide sleeve and through the sleeve towards the bone  2 ,  3 . The gauge rod  14  can be used in a conventional manner to indicate how far the drilling should go or how long the bone screw  5  should be for optimum function. In  FIG. 4  the gauge rod  14  has been removed. 
     The hole for the bone screw  5  can now be drilled. Accordingly, as illustrated in  FIG. 5 , the drill  13  provided with the duct  12  is introduced through the guide sleeve  11  towards the bone fragment  2  and the drilling of the hole for the bone screw  5  is commenced, using a suitable drive device  15 . The drill  13  has an outside diameter of preferably about 6.5 mm and fits exactly in the guide sleeve  11 . The drill  13  is guided by the guide sleeve  11  to a correct position against the bone fragment  2  and thereafter by the guide wire  7  through the bone fragment  2  and past the fracture  1  into the bone fragment  3 . Monitoring that the hole for the bone screw  5  is of a correct length is carried out with advantage at the rear of the guide sleeve  1  where the drill  13  or the drive device  15  bears suitable markings  16 . This entails the drill  13  being halted about 2 cm from the tip of the guide wire  7 , i.e. about 2 cm before reaching the point to which the bon screw  5  is intended to be screwed in. 
     After any necessary adjustment of the securing plate  4  sideways, a further second guide sleeve  11  is now applied as per  FIG. 6  in a second threaded hole  9  running through the plate. Alternatively, a guide sleeve  8  for a guide wire  7  may be applied first and the same procedure as before, with the same parts as above, may be carried out. With advantage, although not depicted in the drawings, guide sleeves of desired kinds  8 ,  11  may already from the outset be applied in the respective threaded holes  9  in the securing plate  4  to give the surgeon a better grasp for correct control of the guide wire  7  and the respective drills  13 ,  17 . The guide sleeve  11  in the version depicted is intended to guide a drill  17  without a duct for the guide wire but with a conical tip (see  FIG. 7 ). This solid drill  17  is driven in to a desired position for the bone screw  6  by means of the drive device  15 . The correct length is read with advantage at the rear of the guide sleeve  11 , where the drill  17  or the drive device  15  bears suitable markings  16  ( FIG. 7 ). The drill  17  and the guide sleeve  11  for it are removed ( FIG. 8 ), leaving a hole  18  for the one screw  6  in the bone fragments  2 ,  3 , which hole is shorter than the distance to which the bone screw is intended to be screwed in. 
     The bone screw  6  can now, by means of a first fixing portion in the form of a threaded forward end portion  19 , be screwed in through the free threaded hole  9  in the securing plate  4  (see  FIG. 9 ) and into the hole  18  in the bone fragments  2 ,  3  in order to fix these bone fragments. Alternatively, the threaded forward end portion  19  of the bone screw  6  may be somewhat smaller and only be in contact with, i.e. ride on, the threads in the threaded hole  9  in the plate  4 . For example, the thread on the threaded forward end portion  19  of the bone screw  6  may be about 8 mm, while the thread in the threaded hole  9  in the securing plate  4  may, as previously indicated, be about 9-10 mm. The bone screw  6  is screwed in by using a suitable tool in the version depicted a suitable type of screwdriver  20 . Alternatively it is of course possible to conceive of using for his purpose the same drive device  15  as for the drills  13 ,  17 . The bone screw  6  is screwed in until the second fixing portion in the form of a threaded rear end portion  21  thereof engages in the threaded hole  9  in the securing plate  4  and locks the bone screw to the plate, while at the same time the threaded forward portion  19  of the bone screw is screwed through the outer bone fragment  2  and into the inner bone fragment  3  for engagement therein and locking of the latter bone fragment to the bone screw and the plate, and hence also of the outer bone fragment  2  between the plate and the inner bone fragment. The middle portion  22  of the bone screw  6 , which is preferably unthreaded, has with advantage an outside diameter corresponding to that of the drill  17 , i.e. about 6.5 m. In  FIG. 10  the bone screw  6  is fully screwed in. 
     In  FIG. 11  the drill  13 , the guide sleeve  11  for the drill, and the guide wire  7  have been removed. The bone screw  5 , preferably similar in form to the bone screw  6 , is screwed into the threaded hole  9  in the plate  4  freed by the removal of said items and into the hole  23  created by the drill  13  ( FIG. 10 ) in the bone fragments  2 ,  3  for fixation of the bone fragments. 
     The result is a stable connection between the securing plate  4  and the bone screws  5 ,  6  which prevents the bone screws from changing their angular position relative to the plate and relative to one another in such a way that the bone screws would have crossed one another. There is also optimum fixation of the bone fragments  2 ,  3  by the bone screws  5 ,  6 . 
     However, the bone screws  5 ,  6  are also configured, as a result of their smooth middle portion  22 , to allow the bone fragments  2 ,  3  to be compressed so that the outer bone fragment  2  slides inwards away from the securing plate  4  towards the inner one fragment  3  into which the bone screws are firmly screwed. On such occasions, the securing plate  4  will, through being locked to the bone s move away from its abutment against the outer bone fragment  2  (this is represented schematically in  FIG. 12  by the intermediate space  24  between the securing plate and the outer hone fragment), but without affecting the strength of the connection and without any impairment of function. 
       FIGS. 13 and 14  depict alternative versions of the securing plate  4 . The securing plate  4  has in these versions three threaded holes  9  for bone screws. 
     In all the versions depicted, the threaded holes  9  for the bone screws run substantially parallel with one another so that the bone screws  5 ,  6  will likewise run substantially parallel with one another. Parallel running of the fixation means facilitates in particular the sliding movement of the outer bone fragment  2  along the fixation means (along the middle portion  22  thereof) for compression of the bone fragments. 
     The securing plate  4  according to the present invention may be used not only for femur neck (collum femoris) fractures but also for, for example, upper arm (humerus) fractures. 
     Since during operations for fixation of bone fragments at bone fractures it is important that the fixation means assume exactly predetermined positions relative to the hone fragments and to one another, it is of advantage that the device according to the invention also allows the application of guide sleeves for guidance of drills for drilling holes for the bone screws in the bone fragments, and/or guide sleeves for guidance of guide wires for said drills, in the same holes in the securing plate as are intended for the fixation means. This means that surgical staff need no longer keep count of an unnecessarily large number of different items for performing an operation, operating time becomes shorter and risks and complications for patients are reduced. It will be obvious to one skilled in the art that the device according to the present invention can be modified and altered within the scope of the claims set out below without departing from the idea and objects of the invention. Thus, as indicated above, the securing plate  4  may be used for guide sleeves  8  for guide wires and thereafter for guide sleeves  11  for drills or, for example, immediately for guide sleeves  11  for drills. The securing plate  4  may of course also be used only for guide sleeves  8  for guide wires, followed by drill guidance solely by guide wire, without special guide sleeves for drills. The securing plate  4  may also be used for bone screws of different kinds from the bone screws  5 ,  6  described above or for other types of fixation means, e.g. bone nails. A bone nail may have a sleeve and, disposed therein, a pin arranged for movement in the sleeve so that at least a forward portion of the pin can be driven outwards through at least one side aperture in the sleeve, in which case this forward portion constitutes a first fixing portion in the form of at least one hook which engages in the inner bone fragment, and the respective bone nail has in addition a second fixing portion of the type described above. As the density in the inner bone fragment is greatest at its centre, it is of advantage if the respective bone nail is applied in such a way that the forward portion of the pin is caused, during the driving, to engage in the central portions of the bone fragment. The respective bone nail may also be so configured as to achieve engagement in the central portions of the inner bone fragment. For example, where there is a threaded second fixing portion, the threads therein may be so disposed and/or configured that said result is achieved. Having the forward portion of the pin in the respective bone nail pointing towards the centre of the inner bone fragment not only means that the bone nails have a better grip in the inner bone fragment but also counteracts the risk of rotation or other movement of the bone nails. Said first and second fixing portions of the fixation means may also be other than threaded portions. The size and choice of material of the constituent items of an operating set may vary as necessary and desired.