Abstract:
In order to improve a surgical positioning and holding device for positioning and holding a guide for a surgical machining tool, with at least one fastening element for fixation to a bone to be machined and with a platform held on the at least one fastening element so as to hold the guide, so that anchoring surfaces may be prepared in a simple manner and with a high degree of precision on a bone to be machined, it is proposed that the guide be mounted for rotation about a first axis of rotation and be designed such that at least one surface concentric with the first axis of rotation may be prepared with the machining tool guided in or held on the guide.

Description:
[0001]     This application is a continuation of international application number PCT/EP2004/001347 filed on Feb. 13, 2004.  
         [0002]     The present disclosure relates to the subject matter disclosed in international application number PCT/EP2004/001347 of Feb. 13, 2004 and German application number 103 09 987.5 of Feb. 28, 2003, which are incorporated herein by reference in their entirety and for all purposes. 
     
    
     BACKGROUND OF THE INVENTION  
       [0003]     The present invention relates to a surgical positioning and holding device for positioning and holding a guide for a surgical machining tool, with at least one fastening element for fixation to a bone to be machined and with a platform held on the at least one fastening element so as to hold the guide mounted for rotation about a first axis of rotation.  
         [0004]     Such devices are used, for example, in operations on joints, in which parts of a damaged joint are replaced by artificial joint components. For this purpose, the device is fixed with the at least one fastening element on the bone to be machined, and an anchoring surface for the artificial joint component is prepared using a machining tool guided in the guide. Herein, in particular, flat anchoring surfaces are formed on bones by partial resection. An example of preparation of a spherical anchoring surface is described in U.S. Pat. No. 5,314,482. Herein it is disadvantageous that the machining tool has to be advanced towards the bone to be machined from the front because this makes complete opening of the damaged joint necessary.  
         [0005]     The object underlying the present invention is, therefore, to so improve a surgical positioning and holding device of the kind described at the outset that anchoring surfaces may be prepared in a simple manner and with a high degree of precision on a bone to be machined.  
       SUMMARY OF THE INVENTION  
       [0006]     This object is accomplished in accordance with the invention in a surgical positioning and holding device of the kind described at the outset in that the guide is mounted for rotation about a first axis of rotation and is designed such that at least one surface concentric with the first axis of rotation may be prepared with the machining tool guided in or held on the guide.  
         [0007]     Cylindrical surfaces may be prepared on a bone in an extremely simple way with such a device. Owing to the special orientation of the axis of rotation, it is, for example, possible to work on a condyle on a femur from a lateral or medial direction. Therefore, complete opening of the joint to be worked on is not necessary, but rather such surgery may also be performed by a minimally invasive technique or by a miniarthrotomy.  
         [0008]     To ensure a particularly secure hold of the device on the bone to be worked on, it is advantageous for a second fastening element to be provided for fixation to the bone to be worked on and for the second fastening element to be guided and/or held on the platform.  
         [0009]     To join the platform in a simple way to the at least one fastening element, the platform may comprise at least one fastening element receptacle for receiving the at least one fastening element. The fastening element may be inserted into the fastening element receptacle and optionally additionally secured therein against relative movement.  
         [0010]     A particularly simple configuration of the device is obtained when the at least one fastening element receptacle comprises a bore. In particular, this may be a blind hole bore.  
         [0011]     To join the platform in a simple way to several fastening elements, it is advantageous for longitudinal axes of at least two fastening element receptacles to be aligned parallel to each other. The platform may then be guided onto fastening elements fixed in the bone to be machined in the direction of the longitudinal axes into or onto the fastening element receptacles.  
         [0012]     In accordance with a preferred embodiment of the invention, provision may be made for the longitudinal axes of the at least two fastening element receptacles to extend parallel or almost parallel to the first axis of rotation. If, for example, the at least one fastening element is anchored in a navigationally assisted manner in the bone to be machined, a direction of the first axis of rotation can then be precisely or roughly specified.  
         [0013]     It is advantageous for a bearing shaft to be provided on the platform and for the bearing shaft to define the first axis of rotation. In this way, the first axis of rotation is optically immediately recognizable. The bearing shaft may be arranged movably relative to the platform or stationarily thereon.  
         [0014]     To allow fine adjustment of the first axis of rotation relative to the at least one fastening element, the bearing shaft is mounted on the platform so as to be displaceable in a first direction of displacement relative to the at least one fastening element. The first direction of displacement may be optionally selected, in particular, parallel or transversely to the first axis of rotation.  
         [0015]     For fine adjustment of the first axis of rotation relative to the at least one fastening element, the bearing shaft may be mounted on the platform so as to be displaceable in a second direction of displacement relative to the at least one fastening element. In particular, the first and second directions of displacement may be oriented at right angles to each other.  
         [0016]     A position of the first axis of rotation relative to the at least one fastening element is adjustable for a third degree of freedom when the bearing shaft is mounted on the platform so as to be displaceable about a second axis of rotation relative to the at least one fastening element. An angle of inclination of the first axis of rotation relative to a longitudinal axis of the at least one fastening element is thereby adjustable.  
         [0017]     The first and second axes of rotation are preferably oriented at right angles to each other. The first axis of rotation can thus be inclined relative to the at least one fastening element, so that the surface to be prepared on the bone to be machined can be at an incline relative to a longitudinal axis of the at least one fastening element.  
         [0018]     A particularly simple design is obtained for the device when it comprises an articulated arm mounted for rotation about the first axis of rotation, when one end of the articulated arm is mounted on the bearing shaft so as to be rotatable about the first axis of rotation and when another end of the articulated arm carries the guide. A compass-type construction of the device may be realized in a particularly simple way with such an articulated arm.  
         [0019]     A particularly good hold and a particularly good guidance of the machining tool on the device are obtained by the guide comprising a sleeve for receiving the machining tool. For example, a machining tool in the form of a milling cutter or a drill may be guided almost without any play in the sleeve, so that cylindrical surfaces may be prepared with a high degree of precision on the bone.  
         [0020]     It is advantageous for the sleeve to be rotatably mounted on the articulated arm. This results in a decrease in wear of the device. The sleeve is advantageously mounted by means of ball bearings on the articulated arm.  
         [0021]     The first axis of rotation may be altered in its position relative to the at least one fastening element in a simple way when a first linear drive is provided on the platform in order to displace the bearing shaft in the first direction of displacement relative to the at least one fastening element.  
         [0022]     A particularly simple design is obtained for the device when the first linear drive is a spindle drive with a first threaded spindle and a first drive knob and when a longitudinal axis of the first threaded spindle defines the first direction of displacement. Only a minimum number of components is required for a spindle drive, which simplifies the construction of the device.  
         [0023]     It is advantageous for a second linear drive to be provided on the platform in order to displace the bearing shaft in the second direction of displacement relative to the at least one fastening element. A position of the first axis of rotation relative to the at least one fastening element may be adjusted in a simple way with the second linear drive.  
         [0024]     To simplify a construction of the device it is advantageous for the second linear drive to be a second spindle drive with a second threaded spindle and a second drive knob and for a longitudinal axis of the second threaded spindle to define the second direction of displacement.  
         [0025]     For the device to be of particularly compact design, the longitudinal axis of the second threaded spindle may define the second axis of rotation. For example, the threaded spindle could serve as bearing shaft for a pivotal movement about the second axis of rotation.  
         [0026]     To realize a pivotal movement of the first axis of rotation relative to the at least one fastening element in a simple way, an eccentric drive may be provided on the platform in order to pivot the bearing shaft about the second axis of rotation relative to the at least one fastening element.  
         [0027]     A particularly simple construction is obtained when the eccentric drive comprises a rotational member mounted eccentrically about a third axis of rotation and when the third axis of rotation extends parallel to the second axis of rotation.  
         [0028]     In operations on knee joints, for example, the problem may arise that the first axis of rotation has to be positioned so as to intersect an area of attachment of collateral ligaments, muscles, tendons or these themselves. Therefore, if the first axis of rotation were defined by the at least one fastening element, this would result in damage to the collateral ligaments. It is, therefore, advantageous for the at least one fastening element to be spaced from the axis of rotation. In particular, the device may be so designed that the fastening elements are arranged in an area of the bone to be machined that is remote from the area of attachment of the collateral ligaments, so that no tendons, muscles or ligaments are damaged. With this construction, the first axis of rotation may nevertheless intersect ligaments or the like.  
         [0029]     In accordance with a preferred embodiment of the invention it may be advantageous for the guide to be securable in a rotational position relative to the platform. Depending on its design, the guide may then itself define an axis of rotation for a machining tool, for example, a cylindrically curved saw blade, with which a likewise cylindrical surface may be prepared on a bone to be machined.  
         [0030]     In particular, it is advantageous for the guide to define a fourth axis of rotation. In this way, surfaces concentric with the fourth axis of rotation may be prepared on a bone to be machined with corresponding machining tools, for example, with cylindrically curved saw blades.  
         [0031]     A particularly compact design is obtained when a width of the platform in the second direction of displacement is 30 mm at most. The device is then also suitable for minimally invasive operations.  
         [0032]     It is advantageous for a spacing of the guide from the first axis of rotation to lie in a range of from 15 mm to 50 mm. Radii of curvature of the surface to be machined can thus be realized in the given range or even smaller ones given a corresponding diameter of the machining tool. In addition, an overall height of the device is thus reduced.  
         [0033]     To be able to use the device particularly universally, a set of articulated arms of different lengths may be provided, in accordance with a preferred embodiment of the invention, and each articulated arm may have a different spacing between the axis of rotation and the guide. Depending on the size of the bone to be machined, an articulated arm of optimum length may be selected and joined to the platform for guiding the machining tool.  
         [0034]     It is advantageous for a reference element for navigation control to be provided on the device. Surfaces may thus be prepared in a navigationally assisted manner on the bone to be machined. In particular, when the at least one fastening element has already been anchored in a navigationally assisted manner on the bone to be machined, a fine adjustment of the first axis of rotation relative to the at least one fastening element may be carried out under navigational control.  
         [0035]     It is advantageous for the guide to be displaceable in a direction parallel to the first axis of rotation relative to the platform. Such an arrangement enables a further possibility for adjusting the guide relative to the fastening elements. In particular, whenever adjustability of the bearing shaft relative to the securing pins is not possible or only possible with difficulty, the guide may be brought in this way into a desired position.  
         [0036]     It is advantageous for the fourth axis of rotation defined by the guide to extend at right angles to the first axis of rotation. This arrangement makes it possible to work on a bone with a machining tool from the front, for example, with a face milling cutter. In this way, a surface concentric with the first axis of rotation may be made.  
         [0037]     The fourth and first axes of rotation preferably intersect each other. A path concentric with the first axis of rotation may thereby be directly described with an end of a machining tool.  
         [0038]     The following description of preferred embodiments of the present invention serves in conjunction with the drawings for further explanation. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0039]      FIG. 1  is a perspective view of an aligning instrument according to the invention secured on a bone to be worked on;  
         [0040]      FIG. 2  is a lateral view of the aligning instrument secured on the bone to be worked on;  
         [0041]      FIG. 3  is a sectional view of the aligning instrument;  
         [0042]      FIG. 4  is a sectional view of the aligning instrument along line  4 - 4  in  FIG. 3 ;  
         [0043]      FIG. 5  is a sectional view of the aligning instrument along line  5 - 5  in  FIG. 3 ;  
         [0044]      FIG. 6  is a sectional view similar to  FIG. 3  with the aligning instrument in a pivoted position;  
         [0045]      FIG. 7  is a perspective view of a second embodiment of an aligning instrument;  
         [0046]      FIG. 8  is a further perspective view of the second embodiment of an aligning instrument; and  
         [0047]      FIG. 9  is a cross-sectional view of the second embodiment of an aligning instrument. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0048]      FIG. 1  shows a surgical positioning and holding device according to the invention, which comprises an aligning instrument generally designated by reference numeral  10  and two bone pins  12 .  
         [0049]     The aligning instrument  10  comprises two frame parts mounted for pivotal movement relative to each other, namely a holding frame  14  connected to the bone pins  12  and a bearing frame  16 . The holding frame  14  comprises two flat, L-shaped side walls  18  which are arranged parallel to each other and are connected to each other by a connecting plate  20 . The substantially L-shaped bearing frame  16  is mounted between the side walls  18  so as to be pivotable about a pivot axis  22  relative to the holding frame  14 .  
         [0050]     The pivot axis  22  is defined by a threaded spindle  24  of a spindle drive generally designated by reference numeral  25 . The threaded spindle  24  is rotationally fixedly connected to the side walls  18  and is provided with an external thread in an area between the two side walls  18 . It also extends through a bore  26  of a leg  28  of the bearing frame  16 , which is held between the side walls  18 . The leg  28  is provided transversely to the bore  26  with an opening  30  of rectangular parallelepiped shape, in which an adjusting wheel  32  provided with an internal thread  34  is arranged. The internal thread  34  corresponds to an external thread  36  of the threaded spindle  24 . A width of the leg  28  in the direction of the pivot axis  22  is smaller than a distance between the side walls  18 , so that a sideways movement of the bearing frame  16  relative to the holding frame  14  is made possible by means of the spindle drive  25 , i.e., by turning the adjusting wheel  32  on the threaded spindle  24 . The threaded spindle  24  thus forms together with the adjusting wheel  32  a linear drive in the form of the spindle drive  25 .  
         [0051]     A hollow-cylindrical bearing sleeve  38  forms a second leg of the bearing frame  16  extending at right angles to the leg  28 . An axis of symmetry  40  of the bearing sleeve  38  is oriented perpendicular to the pivot axis  22 . Parallel to the axis of symmetry  40  the bearing sleeve  38  is provided with a longitudinal slot  42  which extends over almost the entire length of the bearing sleeve  38  and through which a cylindrical bearing bolt  44  projects. It is rotationally fixedly connected to a cylindrical displacement member  46  which is guided in the bearing sleeve  38 . An outer diameter of the displacement member  46  is only insignificantly smaller than an inner diameter of the bearing sleeve  38 , so that the displacement member  46  can only be displaced in the direction of the axis of symmetry  40  in the bearing sleeve  38 . A rotation of the displacement member  46  in the bearing sleeve  38  is prevented by the bearing bolt  44  extending through the longitudinal slot  42 .  
         [0052]     The displacement member  46  is also rotationally fixedly connected to a threaded bolt  48  which projects through a front bore  50  of a front face  52  of the bearing sleeve  38 . Inserted in the front bore  50  with a positive fit is a threaded sleeve  54  which is provided with an internal thread and is rotationally fixedly connected to a knurled head  56  lying on the outside against the front face  52 . The threaded sleeve  54  projects somewhat into the bearing sleeve  38  and is secured with a retaining ring  58  against axial displacement in the direction of the axis of symmetry  40 . The axis of symmetry  40  coincides with an axis of symmetry of the threaded bolt  48 . By turning the knurled head  56  the threaded bolt  48  is moved in the direction of the axis of symmetry  40 , so that the displacement member  46  is displaced linearly in the bearing sleeve  38 . In this way a linear drive  60  in the form of a spindle drive is formed.  
         [0053]     A lever  62  of rectangular parallelepiped shape is provided at one end thereof with a bore  64  in which the bearing bolt  44  is inserted. The lever  62  is thus pivotable about the bearing bolt  44  forming a bearing shaft, namely about an axis of rotation  66  defined by the bearing bolt  44 . At its other end the lever  62  is integrally connected to a guide sleeve  68  whose axis of symmetry defines an axis of rotation  70 . The axis of rotation  70  extends parallel to the axis of rotation  66 . Inserted into the guide sleeve  68  is a further bearing sleeve  72  whose axis of symmetry coincides with the axis of rotation  70 . The bearing sleeve  72  is somewhat more than twice as long as the guide sleeve  68 . It is rotationally fixedly connected to the guide sleeve  68 . It is also conceivable for the bearing sleeve  72  to be mounted on the guide sleeve  68  by means of a ball bearing.  
         [0054]     An eccentric bolt  74  is rotatably held in bores  76  in the side walls  18  parallel to the threaded spindle  24 . Arranged between the side walls  18  is a supporting cylinder  78  which is rotationally fixedly connected to the eccentric bolt  74 . An adjusting wheel  80  is arranged at one end of the eccentric bolt  74 . Another end is provided with a bolt head  82 . A movement in the direction of an eccentric axis  84  defined by a longitudinal axis of the eccentric bolt  74  is prevented by the eccentric bolt  74  being held at both sides at one side wall  18  by the bolt head  82  and the supporting cylinder  78  and at the other side wall  18  by the supporting cylinder  78  and the adjusting wheel  80 . A circumferential wall of the supporting cylinder  78  forms a supporting surface  86  for the bearing sleeve  38 . By turning the adjusting wheel  80  the supporting cylinder  78  is pivoted about the eccentric axis  84 , so that a spacing of the bearing sleeve  38  resting against the supporting cylinder  78  from the eccentric axis  74  is altered and thereby brings about a pivoting movement of the bearing sleeve  38  and thus of the bearing frame  16  about the pivot axis  22 . The axis of rotation  66  is also inclined relative to the pivot axis  22  by this pivoting.  
         [0055]     A machining tool, for example, a milling cutter  88  or a saw blade  90  may be guided in the bearing sleeve  72 . The saw blade  90  is curved in the shape of a section of a cylinder wall and extends over an angular range  92  of approximately 100°. Arranged concentrically with the saw blade  90  on a cover plate  96  is a holding pin  94 . The holding pin  94  may likewise be guided in the bearing sleeve  72 .  
         [0056]     Use of the aligning instrument  10  is explained hereinbelow in conjunction with FIGS.  1  to  6 , by way of example, in conjunction with preparation of a cylindrical anchoring surface  98  for anchoring an artificial condyle  100 , which is to replace a partially damaged, natural condyle on a femur  102 .  
         [0057]     The aligning instrument  10  is advanced with the two bone pins  12  either laterally or medially, depending on the damaged condyle is to be replaced, towards the femur  102 . This may be done in a navigationally assisted manner. The bone pins  12  are driven into the femur  102  and the aligning instrument is anchored in this way. A machining tool, for example, the milling cutter  88 , is inserted into the bearing sleeve  72  and made to rotate so as to machine the femur  102  and simultaneously pivoted within an angular range  104  of approximately 80 to 90° by pivoting the lever  62  about the axis of rotation  66 , as shown in  FIG. 2 . The femur  102  is thus resected in the desired manner.  
         [0058]     If necessary, a position of the axis of rotation  66  relative to the femur  102  may be readjusted before preparing the anchoring surface  98 . To do so, an adjustment in the direction of the axis of symmetry  40  may be made by means of the linear drive  60 . Furthermore, a linear displacement of the bearing bolt  44  relative to the bone pins  12  may be carried out by turning the adjusting wheel  32  in the direction of the pivot axis  22 .  
         [0059]     In addition, the axis of rotation  66  may be altered in its inclination relative to the bone pins  12  by turning the adjusting wheel  80 , which, as described hereinabove, brings about a pivoting of the bearing frame  16  about the pivot axis  22 .  
         [0060]     For use with the cylindrical saw blade  90  described hereinabove the lever  62  may be fixed in a pivoted position. In the case of differently shaped saw blades  90 , a pin borehole  95  extending through the holding pin  94  in the longitudinal direction thereof may also be provided for receiving the bearing bolt  44 . Instead of the lever  62 , the holding pin  94  can thus be pivotably mounted on the bearing bolt  44 .  
         [0061]     To obtain anchoring surfaces with different radii, several different levers  62  are provided, with the spacing between the axis of rotation  66  and the axis of rotation  70  varying in each case. Depending on the condyle  100  to be implanted, a corresponding lever  62  will be selected for preparation of the anchoring surface  98 .  
         [0062]     A second aligning instrument, generally designated by reference numeral  120 , is shown in FIGS.  7  to  9 . It comprises a platform, generally designated by reference numeral  122 , which may be held on a femur  124  by means of two bone pins  126  and  128  which include approximately an angle of 120° between them. A pivot bracket, generally designated by reference numeral  132 , is mounted on the platform so as to be pivotable about a pivot axis  130 .  
         [0063]     Both the platform  122  and the pivot bracket  132  are substantially symmetrical in relation to a plane of symmetry perpendicular to the pivot axis  130 .  
         [0064]     The platform  122  comprises a half ring-shaped frame  134  defining a frame plane. There are provided parallel to the frame plane a plurality of pin holes  136  through which the bone pins  126  and  128  are insertable, so that these are aligned in a plane at an angle of 120° relative to each other. Ends of the bone pins  126  and  128  projecting from the femur  124  are provided with a screw thread onto which a threaded sleeve  140  provided with a turning knob  138  is screwable and fixes the frame  134  on the two bone pins  126  and  128 . Elongated openings  142  are provided on the frame  134  transversely to longitudinal axes of the bone pins  126  and  128 . Free ends  144  and  146  of the frame  134  have an elongated opening  148  extending away from the ends  144  and  146 . Inserted in each of these openings  148  is a shaft  150  extending away from the ends  144  and  146 . The shaft  150  carries a bearing sleeve  152  displaceable on the shaft and defines a longitudinal axis  151 .  
         [0065]     A bearing bolt  154  is arranged on the bearing sleeve  152  and protrudes at right angles therefrom. The substantially U-shaped pivot bracket  132  is mounted on the bearing bolt  154  so as to be pivotable about the pivot axis  130 . The pivot bracket  132  comprises an elongated plate  156  of rectangular parallelepiped shape, which is provided with two elongated holes  158  arranged symmetrically.  
         [0066]     A cylinder  162  is arranged at free ends  160  of the plate  156  with its longitudinal axis transversely to the longitudinal direction of the plate  156 . It continues into a cylindrical rod  164  of decreased diameter, which carries at its free end a bearing groove  166  which is mounted by means of a joint pin  168  on the bearing bolt  154  so as to be pivotable about the pivot axis  130 .  
         [0067]     A bearing slide  170  of rectangular parallelepiped shape is displaceable parallel to the elongated holes  158  and to the longitudinal direction of the plate  156 . It carries two set screws  172  extending parallel through the elongate holes  158  with a knurled nut  174  screwed onto each one. The bearing slide  170  can be clamped to the plate  156  by means of the knurled nuts  174 . In order to change a position of the bearing slide  170  relative to the plate  156 , the two knurled nuts  174  are unscrewed and the bearing slide  170  displaced relative to the plate  156  until a desired position is reached. The bearing slide  170  can then be clamped on the plate  156  again by means of the knurled nuts  174 .  
         [0068]     Two guide sleeves  176  are arranged laterally on the bearing slide  170  with each facing in the direction towards one of the two cylinders  162 . Longitudinal axes  178  of the guide sleeves  176  extend at right angles to the pivot axis  130 . A machining tool, for example, in the form of the milling cutter  180  shown in  FIGS. 7 and 8 , may be inserted into each of the two guide sleeves  176 .  
         [0069]     To avoid rubbing of the milling cutter  180  on the guide sleeve  176 , the milling cutter  180  is, in turn, arranged on a rotary bearing  182 , preferably by means of ball bearings, and the rotary bearing  182  is supported on a front face of the guide sleeve  176 . The milling cutter  180  has a cylindrical work area  184  at its end, so that it may be used as face milling cutter and as side milling cutter.  
         [0070]     A template  186  facing away from the plate  156  is arranged on the bearing slide  170  and has a guide slot  188  extending through the template parallel to the longitudinal axes  178 . It serves, for example, as saw template for guiding a saw blade which is not shown.  
         [0071]     With the aligning instrument  120 , surfaces concentric with the pivot axis  130  may be prepared on the femur  124  or on any other bone of the human body. For this purpose, the platform  122  is fixed on the bone pins  126  and  128  on the femur  124 , as shown in  FIGS. 7 and 8 . The bone pins  126  and  128  are anchored at locations on the femur  124  at which neither tendons nor muscles have grown. With the aligning instrument  120 , a cylindrical anchoring surface  192  may be prepared on one of the two condyles  190  by the milling cutter  180  being inserted into one of the two guide sleeves  176  and axially immovably fixed there. When the pivot bracket  132  is pivoted about the pivot axis  130 , the condyle  190  is partially resected during rotation of the work area  184  of the milling cutter  180  operating as face milling cutter. There then remains the cylindrical anchoring surface  192  on which an artificial condyle, not shown, may be anchored. If necessary, a flat cut may also be made on the condyle  190  with the aid of the template  186 , whereby a flat cut surface  194  is produced on the condyle  190 . The cut surface  194  extends parallel to the pivot axis  130 .  
         [0072]     For navigationally assisted use of the aligning instruments  10  and  120 , these may be provided with coupling pins  196  for fixing detectable marker elements. Three coupling pins  196  protruding from the cylinders  162  and the frame  134  are arranged on the aligning instrument.