Abstract:
An internal saw for osteotomy of tubular bones, comprising a base body, provided with a saw blade, which is moved radially out of the base body, whereby the base body, in particular the saw blade may be driven to oscillate radially.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to an internal saw for osteotomy of tubular bones, comprising a base body provided with a saw blade which can be moved radially out of the base body.  
         [0002]     An internal saw of this kind for tubular bones is known from German utility model G 92 17 188.5, for example. With an internal saw of this kind, a tubular bone can be cut through with a saw and a saw unit. The saw emerges radially from the base body and cuts through the bone as the base body is turned. Particularly in surgery, bones have to be cut through radially, for example, if bone or bone fractures do not fuse correctly or if it is necessary to correct malformed or curved bones or extremities which are too long or too short. Internal saws of this kind are usually guided into the tubular bone from the end in order to cut through the bone from the inside outward. Particularly in distraction of bones, a medullary nail, a distraction device or the like is inserted into the axial bore or into an axial access after the tubular bone has been cut through.  
         [0003]     A disadvantage of the conventional known internal saw is that it is awkward to operate and difficult to insert and control. In particular, when the above-described internal saws are used, the periosteum and surrounding tissue are often damaged when cutting through the tubular bone, which is undesirable. This slows down the course of healing.  
         [0004]     U.S. Pat. No. 5,591,107 describes an oscillating internal saw for osteotomy of tubular bones, where a manually operated lever is used to influence an advance movement of the radial saw, which emerges radially from a base body. In addition, this manually operated lever can be used to effect a rotation movement.  
         [0005]     WO 01/34040 A1 discloses an internal saw for cutting through tubular bones, where two tools mounted like scissors are moved apart from one another by means of centrifugal force during rotation, these tools bearing internally on the tubular bone and thus cutting through the tubular bone upon rotation. A disadvantage here is that this device can only be used to cut through bones of large internal diameter.  
         [0006]     It is an object of the present invention to make available an internal saw of the type mentioned at the outset which eliminates the above-mentioned disadvantages and with which it is also possible to exert an influence on different bone cross sections, so that these are cut though uniformly. Such an internal saw should also be easy to operate and inexpensive to produce.  
       SUMMARY OF THE INVENTION  
       [0007]     The foregoing object is achieved by the present invention wherein a saw blade can be very easily exchanged and advanced. For example, an operating element can be assigned to a jacket surface of the base body, which operating element can be operated by means of a finger of a human hand and can be axially displaced. The saw blade, which directly adjoins the operating element, can be pushed radially out from one end of the base body in a graduated manner, using the fingers of a human hand, in order to advance or orient the saw blade. At the same time, the base body can be turned radially about a center axis in order to perform a sawing operation. It is important, however, that, during the radial turning of the base body, the latter, and thus also the saw blade, performs an oscillating movement by way of a drive device. This oscillating movement improves the cutting action and at the same time ensures that saw blades can be used which in principle do not damage the periosteum or the bone itself. The saw blade obtains its cutting and separating action through the oscillating movement alone, but only for hard objects, such as for example the tubular bone. When cutting through the tubular bone, by radial advance of the saw blade and simultaneous oscillation, the saw blade abuts the periosteum but does not damage it in the process.  
         [0008]     A further advantage of the present invention is that the advance of the saw blade can be graduated manually, with or without locking, so that the surgeon can read off how deep he has cut through the tubular bone. This advance movement can also be prestressed by means of a spring element which engages on the operating element or directly on the saw blade. The invention is not intended to be limited to this.  
         [0009]     In a further illustrative embodiment of the present invention, it has proven particularly advantageous to operate the saw blade, in particular the operating element, by means of an actuator, if appropriate of a control means attached to it, a force sensor being provided between actuator and saw blade or between actuator and operating device. The control means is able to provide the actuator, for example, with an input corresponding exactly to CAD/CT cross-sectional data of the bone, which then correspondingly controls the depth of advance or a return movement of the saw blade depending on the radial angular position with respect to the bone.  
         [0010]     By this means, a bone which does not have a circular cross section can also be sawn through uniformly since the advance of the saw blade takes place according to the cutting data and the cross-sectional profile of the bone. A computer-aided control means can provide for an advance depth of the saw blade according to the cutting data or cross-sectional profile of the tubular bone. This is also intended to lie within the scope of the present invention.  
         [0011]     It has also proven particularly advantageous that a drive device at the same time transmits, via an oscillation gear, a radial oscillating movement to the base body, in particular to the saw blade, and at the same time can perform a radial complete rotation in a selectable direction for radially cutting through the bone. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     Further advantages, features and details of the invention will become clear from the following description of preferred illustrative embodiments and from the drawing, in which:  
         [0013]      FIG. 1   a  shows a diagrammatic partial longitudinal section through an internal saw for osteotomy of tubular bones;  
         [0014]      FIG. 1   b  shows a diagrammatic partial longitudinal section through a further illustrative embodiment of an internal saw according to  FIG. 1   a;    
         [0015]      FIG. 1   c  shows a diagrammatic partial longitudinal section through a further illustrative embodiment of an internal saw according to  FIGS. 1   a  and  1   b;    
         [0016]      FIG. 2  shows a diagrammatic partial longitudinal section through an internal saw in a possible position of use;  
         [0017]      FIG. 3  shows a diagrammatic partial longitudinal section through the internal saw with associated drive device according to  FIG. 1   a;    
         [0018]      FIG. 4  shows a diagrammatic side view of the internal saw, in particular of a base body in a position of use according to  FIG. 1   a;    
         [0019]      FIG. 5  shows a diagrammatic side view of part of the saw blade, particularly in the end area;  
         [0020]      FIG. 6  shows a diagrammatic partial longitudinal section through a tubular bone with inserted internal saw as a further illustrative embodiment. 
     
    
     DETAILED DESCRIPTION  
       [0021]     According to  FIG. 1   a,  an internal saw R 1  according to the invention has a base body  1  in which a saw blade  5 , preferably of rectangular cross section, is guided axially, preferably centrally, in a guide  2 , and emerges radially from an outlet opening  4  in a head area  3  of the base body  1 . At the other end of the head area  3 , near to a grip element  6 , an insertion shaft  8  serving for insertion of the saw blade  5  is formed on an outer jacket surface  7 , preferably opposite to the outlet opening  4 , in the base body  1 . The saw blade  5  can be connected permanently or releasably to an operating element  9  or can be permanently connected, and the saw blade  5  can be moved radially out of the head area  3  of the base body  1  by movement of the operating element  9  along the double arrow direction X shown. At the front end, the saw blade  5  is provided, as can be seen in particular in  FIG. 5 , with a plurality of teeth  10  which are arranged in an arc shape, for example, in the front end area. The saw blade  5  is preferably curved at the front end.  
         [0022]     By movement of the operating element  9  in the double arrow direction X shown, the end area of the saw blade  5  is moved radially into or out of the base body  1  in the double arrow direction Y shown.  
         [0023]     As can further be seen from  FIG. 1   a,  the operating element  9  can be operated, for example, by a finger of a human hand and can be moved along a graduation  11  which corresponds to a depth of advance of the saw blade  5 . In this way, a depth of advance can be exactly set and read off from the outside.  
         [0024]     It is further of advantage that the saw blade  5 , for example in the case of single use, is simply withdrawn from the insertion shaft  8  and can be very easily exchanged. If appropriate, the operating element  9 , with fixed saw blade  5 , can be inserted again into the base body  1  through the insertion shaft  8  for renewed use. The invention is not limited to this.  
         [0025]     It is important, however, that at one end of the base body  1  the grip eIement  6  is radically and rotationally uncoupled with respect to the base body  1  so that the grip element  6  can, for example, be held by fingers of a human hand, so that the base body  1  can be driven manually and/or automatically about a center axis M. At the other end of the grip element  6 , an attachment  12  is provided, preferably as an AO attachment, for receiving a drive device  13 , as is shown, for example, in a simplified form in  FIG. 3 .  
         [0026]     The drive device  13  can also simply be a manual grip with which the base body  1  can be moved in a rotation movement about the center axis M, the grip element  6  being uncoupled from the rotation movement about the center axis M.  
         [0027]     In the area of the outlet opening  4 , the saw blade  5  lies on an axis A which, in the present case, encloses an angle W, preferably of 90°, between the center axis M.  
         [0028]     The outlet opening  4  is oriented in the base body  1  at an angle W of 90° with respect to the center axis M. It has proven advantageous to provide the outlet opening  4  in the base body  1  at a smaller angle of between 40° and 90°, for example. In this way, the bones can be cut through in inclined cutting surfaces, which results in an enlargement of the cutting surfaces. Thus, in the case of quite large cutting surfaces, it is also of advantage here that more rapid healing is provided and, in particular, greater stability upon fusion of a large cutting surface.  
         [0029]     The outlet opening  4  can be oriented at an angle W of, for example, 40° to 140° between axis A and center axis M. Changing the angle W even during operation, for example by means of a device not shown here, is also intended to lie within the scope of the present invention.  
         [0030]     It has also proven advantageous to have a flushing channel  23  which opens into the insertion shaft  8  and which can serve for flushing and/or aspiration. The base body  1  can also be cooled at the interface via the flushing channel  23 .  
         [0031]     It is also conceivable for the operating element  9  and also the graduation  11  to be provided all round the base body  1 , so that the operating element  9  can be gripped in any desired position and the graduation  11  can be read off in any desired position. In this case, the graduation  11  is arranged all the way round the jacket surface  7  and can, if appropriate, include a plurality of different graduations  11 . The operating element  9  would then also be designed as an annular sleeve or the like which engages completely or at least partially around the jacket surface  7  of the base body  1 .  
         [0032]     In a further illustrative embodiment of the present invention according to  FIG. 1   b,  a further internal saw R 2  is shown which corresponds substantially to the type described above.  
         [0033]     The difference is that the guide  2  forms a greater radius for leading the saw blade  5  from the outlet opening  4  to the insertion shaft  8 . If appropriate, a groove can be formed in the base body  1  in the area of the insertion shaft  8  in the jacket surface  7 , in order to guide or accommodate the saw blade therein.  
         [0034]     In the manner described above, the saw blade  5  can be moved to and fro via the operating element  9  along the graduation  11  in the direction shown by the double arrow X, in order to move the saw blade  5 , in particular its saw teeth  10 , out of the outlet opening  4 .  
         [0035]     It is also conceivable, here, to move the operating element  9  with locking relative to the graduation  11 .  
         [0036]     The scope of the present invention is also intended to include the operating element  9  being adjoined by a spring element  14 , which is designed as a compression and/or tension spring, in order to prestress the operating element  9  toward the head area  3 . It is also conceivable to alter the spring constantly and to vary the prestressing force of the spring element  14 .  
         [0037]     In a further illustrative embodiment of the present invention according to  FIG. 1   c,  an internal saw R 3  is shown which corresponds substantially to the internal saw R 1  according to  FIG. 1 . The difference is that the saw blade  5  and/or the operating element  9  can be moved to and fro by means of an actuator  15  in the direction shown by the double arrow X. The actuator  15  is controlled via a control means  16 .  
         [0038]     A force sensor  17  can be provided between actuator  15  and operating device  9  and/or between actuator  15  and saw blade  5 , in order to exactly measure a permanent force, in particular an advance force. This is important, for example, if the saw teeth  10  cut completely through a tubular bone  18 , see  FIG. 2 , so that periosteum  19  lying thereon is not damaged.  
         [0039]     It has also proven advantageous that, via the control means  16 , the actuator  15  is able to adapt an advance movement of the saw blade, as it is shown in particular in  FIG. 2 , according to the cross-sectional profile of the tubular bone. A corresponding cross section can be determined by ultrasound, for example, and different cutting depths for cutting through the tubular bone  18  can accordingly be input via the control means  16 , so that, depending on the position of the internal saw R 3 , and depending on the position of the internal saw R 3  with respect to the bone, a different depth can be set in accordance with the cross-sectional shape of the tubular bone  18  to be cut through. These data can, for example, also be delivered by wireless transmission to the control means  16  and thus to the actuator  15 .  
         [0040]     In the illustrative embodiment according to  FIG. 2 , the internal saw R 1  is shown in a position of use in which, by radial turning of the base body  1  about the center axis M and simultaneous advance of the saw blade  5 , the tubular bone  18  is cut through.  
         [0041]     An important aspect of the present invention is that the depth of advance of the saw blade  5 , in particular in the area of the outlet opening  4 , is different depending on the position and cross section of the bone, since the tubular bone  18  is thicker or thinner at different angle areas and has different radii with respect to the center axis. In order to compensate for this, a depth of advance can be permanently varied on rotation of the internal saw R 1 . Preferably, the advance of the saw blade  5  is controlled automatically in accordance with the cross section of the tubular bone  18 .  
         [0042]     An important aspect of the present invention is, however, as is shown in particular in  FIG. 3 , that the drive device  13  can be connected to the base body  1 , particularly in the area of the attachment  12 , and an oscillation gear  20  is provided which sets the base body  1  into a radial oscillating vibration movement. At the same time, the drive device  13  can be turned manually and radially about the center axis M in relation to the tubular bone  18  (not shown here) and in relation to the grip element  6 , so that the saw blade  5  cuts through the tubular bone  18  by means of the radial turning. By means of the oscillating movement, i.e. the radial movement to and fro of the base body  1 , and thus also of the saw blade  5 , it is possible to achieve optimized cutting of the tubular bone  18 , without the periosteum  19  being damaged as the saw blade  5  passes through the tubular bone  18 . An oscillating movement of the saw blade  5  does not by itself damage the periosteum  19 . At the same time, a rotation movement about the center axis M can be effected manually and/or automatically via the drive device  13 , this rotation movement being added to or superposed on the oscillating movement, so that the tubular bone  18  is cut through over its complete cross section. If the saw hits the periosteum  19 , the advance is automatically halted and the saw blade  5  drawn back.  
         [0043]      FIG. 4  shows how the saw blade  5  can be moved out of the base body  1  in the Y direction shown, and the base body  1  performs an oscillating movement about the center axis M and can be turned completely about the center axis M in an associated or superposed movement, and the person using the operating element  9  identifies in which radial position the saw blade  5  is located in the tubular bone  18 . This is also intended to lie within the scope of the present invention.  
         [0044]     Another important aspect of the present invention is that the base body  1 , as is shown in particular in  FIG. 6 , is inserted into a bore  21  of a tubular bone  18 . The base body  1  will be inserted with an exact fit into the bore  21  of the tubular bone  18 . Since the base body  1  is turned radially about the center axis M as the saw blade  5  cuts through the bone, it has proven particularly advantageous to provide a plurality of steps  22  in the jacket surface  7  of the base body  1 , their diameter being smaller than the remaining part, for example than a head area  3  of the base body  1 . Thus, the base body  1  bears against the tubular bone  18  only at a few locations, so that the tubular bone  18  is cut through by means of radial turning, with extremely low development of heat in the tubular bone  18 , which fact contributes to the preservation of the tissue and to growth. In this way, vessels of the bone, the periosteum etc., are treated much more gently and exposed to less stress. A rotation movement of the base body  1  has reduced friction and is thus easier.