Abstract:
The present application relates to a surgical connecting device for connecting a first and second cutting block which each serve to make an incision on a first and second anatomical structure, comprising: a first attaching section for attaching the surgical connecting device to the first cutting block by a mechanical connection; a second attaching section for attaching the surgical connecting device to the second cutting block by a releasable mechanical connection; and a spacing section which spaces the first attaching section away from the second attaching section.

Description:
RELATED APPLICATION DATA 
       [0001]    This application claims the priority of U.S. Provisional Application No. 61/056,610, filed on May 28, 2008, which is hereby incorporated in its entirety by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present application relates to the connection of cutting blocks. Cutting blocks are used in surgery, in particular for cutting body structures (bones, in particular the femur and tibia). 
       BACKGROUND OF THE INVENTION 
       [0003]    Preferably, the invention is used in image-assisted navigation (image-guided surgery or IGS). Attaching marker devices to a body structure—for example, a reference star to a bone—and attaching a marker device to a cutting block allows a cutting block to be navigated relative to the body structure and thus allows the cutting block to be positioned exactly relative to the body structure, at a planned location. In order to position the cutting block exactly, an adjusting mechanism is used which is likewise fixed to the bone. In accordance with the prior art, one adjusting mechanism for each cutting block is fixed to the body structure. 
       SUMMARY OF THE INVENTION 
       [0004]    It is an object of the invention, when using two or more cutting blocks, to enable the number of fixing processes for fixing the adjusting mechanisms to the body structure and/or the number of adjusting mechanisms used to be reduced. 
         [0005]    In accordance with the invention, damage to the body structure is advantageously avoided to a greater extent than in the prior art, since fewer fixations are performed. The space requirement is advantageously less, since fewer adjusting mechanisms—in particular, only one adjusting mechanism—is needed. The invention can advantageously reduce the operation time and thus reduce the burden on the patient. 
         [0006]    The aforesaid object is solved by the subjects of the independent claims. Advantageous developments follow from the dependent claims. 
         [0007]    Preferably, the invention relates to a surgical connecting device for connecting a first and second cutting block. Preferably, the surgical connecting device is used in the region of a joint, wherein a first incision on a first body part (for example, the tibia) is to be made by the first cutting block, and an incision on a second body part (for example, the femur) is to be made by the second cutting block. The first and second body part are connected by the joint. The incision is in particular made in order to crop an end of the first and second body part which faces the joint, i.e. which is in particular situated in the vicinity of the joint. The cutting blocks serve to guide a cutting knife and to define a plane in which the incision is to be made using the cutting knife. The cutting blocks in particular comprise two cutting guidance planes which are preferably parallel to each other and between which the blade of a cutting knife can be guided. The distance between the cutting guidance planes corresponds at least approximately to the thickness of the blade or is slightly larger. The cutting guidance planes thus determine the position of the cutting plane in which the incision is made by means of the blade. 
         [0008]    The surgical connecting device in accordance with the invention preferably comprises a first and second attaching section. The first attaching section is formed so as to be able to attach the surgical connecting device to the first cutting block. The second attaching section is formed so as to be able to attach the surgical connecting device to the second cutting block. The first and second attaching sections are preferably formed so as to form a mechanical connection between the surgical connecting device and the respective cutting block. The mechanical connection is preferably releasable and preferably ensures a spatially fixed connection. Examples of a mechanical connection are a positive-fit connection, a force-fit connection or a material-fit connection. Preferably, a positive-fit connection and/or force-fit connection is achieved with the aid of the attaching section. To this end, special contact sections can also be provided on the cutting blocks, via which the attaching sections establish a releasable mechanical connection, in particular a releasable force-fit connection and/or positive-fit connection, when they contact the contact sections, in order to attach the surgical connecting device. The connection can for example be an exact fit and/or a locking connection. Apart from special contact sections on the cutting blocks, the attaching sections can also be formed such that they can be introduced into the gap between the cutting guidance planes of the cutting block, in order to establish a force-fit connection and/or positive-fit connection with the cutting guidance planes. 
         [0009]    The surgical connecting device also preferably comprises a spacing section which spaces the first attaching section away from the second attaching section. This results in a defined and fixed positional relationship between the first and second cutting blocks, when both cutting blocks are connected to the surgical connecting device. Preferably, the distance is selected such that the surgical connecting device can be gripped by a surgeon, in particular even with gloves. The spacing section is in particular configured such that the positional relationship (in particular the distance) between the first and second cutting block can be (mechanically) adjusted, such that the surgical connecting device can be adapted to the respective body structure by the surgeon. To this end, it is also possible to select from different surgical connecting devices having different fixed distances (for example, 18 mm, 19 mm and 20 mm) between the first and second attaching section. In particular, the lower limit for the extent of the spacing is around 1 mm, preferably around 1 cm. The upper limit for the spacing is preferably around 20 cm, more preferably around 10 cm, even more preferably around 5 cm or 3 cm. A typical distance between the first and second attaching section is for example around about 19 mm. 
         [0010]    If the spacing section is configured such that the distance can be adjusted by means of an adjusting mechanism, then the spacing section preferably comprises two parts which are movable relative to each other, the relative position of which can be mechanically determined by a fastening means (for example a setting screw which passes through slits in the movable parts) or a locking connection. In this way, the distance between the attaching sections can then be altered, at least to a predetermined extent, to the desired distance. The locking mechanism and/or the aforementioned fastening means, for example in conjunction with the slits, form examples of an adjusting mechanism using which the distance between the first and second attaching section can be adjusted. 
         [0011]    The spacing section is in particular preferably formed to be large enough to be able to attach a handle to it. 
         [0012]    An intermediate space in which space is provided for the cutting guidance planes of the cutting blocks and/or for contact sections of the cutting blocks is preferably provided between the first and second attaching section. The intermediate space between the first and second attaching section is therefore preferably not completely filled. In particular, the first attaching section is preferably not connected to the second attaching section over the shortest distance by the spacing section. Preferably, the spacing section runs at least partially and preferably at least predominantly outside the intermediate space between the first attaching section and the second attaching section. The intermediate space between the first and second attaching section is in particular the space given by directly and linearly connecting the boundaries of the first attaching section to the boundaries of the second attaching section. 
         [0013]    The boundaries of the attaching sections comprise boundary sections, such as a front end and a rear end of the attaching sections. The front end is characterized in that it precedes during the process of attaching the connecting section to the cutting block, i.e. it has the shortest distance from the cutting block as compared to the other parts of the surgical connecting device, wherein this distance is reduced further and further as the surgical connecting device is moved nearer and nearer to the cutting block, in order to connect the surgical connecting device to the cutting block. The rear end is situated opposite the front end. The rear end is characterized in that it is connected to the spacing section. The front end of the attaching section is in particular formed as an edge of the surgical connecting device, which in particular forms an end of a planar section of the attaching device. This arrangement of the spacing section relative to the attaching sections enables a defined spacing of the cutting blocks. It also prevents parts of the cutting block from obstructing or blocking the connecting device from being attached to the cutting blocks. 
         [0014]    In accordance with another embodiment of the present invention, the attaching sections comprise movable parts and contact parts. The contact parts are preferably spatially fixed relative to the spacing section. The movable parts are preferably movable, in particular elastically movable, relative to the contact parts and in particular also relative to the spacing section. The movable parts can for example comprise elastic elements such as springs or rubber. However, they can also be elastically connected to a part of the attaching section, in particular to the contact parts. The movable parts can for example be elements (for example, metallic or plastic elements) which are only connected in sections, in particular only one section, to other parts of the attaching section, in particular to the contact parts. This connection in sections can in particular be formed to be elastic. In particular, the movable parts can be bent out of a plane relative to the other parts, in particular relative to the contact parts. If a force is exerted on the movable parts, in order to move them towards the contact parts, then an elastic force counteracts this due to the elastic formation of the movable parts. The movable parts are in particular elastically movable relative to a plane which virtually or actually connects the front end and the rear end of the attaching sections and/or in which the contact parts lie. In particular, the movement is performed out of the plane, i.e. in particular transverse to the plane. The contact parts are preferably formed to be planar and preferably lie in the aforesaid plane, or the surfaces of the contact parts define the aforesaid plane. In particular, the contact parts do not comprise any extensions protruding transverse to the plane. Forming the contact parts to be planar allows them to be inserted into the contact sections of the cutting blocks and in particular between the cutting guidance planes. They can in particular be formed such that they can be inserted in an exact fit. 
         [0015]    The movable parts are preferably formed such that the edges of the movable parts which protrude out of the aforesaid plane between the front end and the rear end draw nearer and nearer to said plane in the direction of the front end of the attaching sections, i.e. they are preferably chamfered in the direction of the front end. This has the advantage that as the attaching sections are introduced, the movable parts are pressed ever-increasingly in the direction of the plane, if the attaching section is inserted into a gap—for example, cutting guidance surfaces—or into a groove-shaped contact section. 
         [0016]    Preferably, the surgical connecting device comprises abutment sections which serve to exactly position the surgical connecting device relative to the cutting blocks. To this end, the abutment sections preferably protrude out of the aforesaid plane between the front end and rear end, such that when the attaching section is inserted into a gap, the gap boundaries abut the abutment sections. The gap is for example formed between the cutting guidance planes or by the contact section of the cutting block. Preferably, an abutment section is provided between the spacing section and each of the connecting sections. 
         [0017]    Preferably, the surgical connecting device comprises a marker device. The exact position of the surgical connecting device can be detected by means of the marker device. Since the relative position of the surgical connecting device relative to the cutting blocks is known, in particular due to the cutting blocks abutting the abutment sections, the position of the cutting blocks can also be determined by detecting the marker device which is attached to the surgical connecting device. 
         [0018]    Preferably, other surgical instruments or surgical devices can be attached to the surgical connecting device. In particular, a patella cutting apparatus can be attached to the surgical connecting device, in order to be able to crop the patella. The patella is situated between the femur and the tibia. Since the surgical connecting device is situated between the two cutting blocks, which serve to cut the tibia and femur, respectively, it is situated at a suitable location for cutting the patella. If the surgical connecting device in accordance with the invention comprises the patella cutting apparatus or a way of attaching a patella cutting apparatus, then this automatically results in a suitable position of the patella cutting apparatus during the operation. 
         [0019]    The invention is also directed to a surgical system which comprises both the surgical connecting device and two cutting blocks which are formed for being connected to the surgical connecting device. Preferably, the system also comprises an adjusting mechanism which can be or is connected to a cutting block. The adjusting mechanism is preferably attached to a bone, for example the tibia. Adjusting operational parts are preferably attached to the adjusting mechanism, such as for example wheels, using which it is possible to change the position of the cutting block which is connected to the adjusting mechanism, relative to the part or parts of the adjusting mechanism which are fixedly connected to the bone. The advantages which this has in conjunction with the surgical connecting device in accordance with the invention are described in the following on the basis of a method in accordance with the invention. 
         [0020]    As mentioned, the adjusting mechanism is preferably first fastened to a first body structure (for example, the tibia) using fastening means (for example, pins or nails). In a following step, the adjusting mechanism is connected to the first cutting block, or is already connected to the first cutting block when it is fastened to the first body structure. A marker device is preferably attached to a component of the system, such that changes in position caused by the adjusting mechanism can be detected by detecting the marker device. The marker device can for example be attached to the part of the adjusting mechanism which is or can be connected, spatially fixed, to the first cutting device and which changes its position relative to the first body structure by actuating the adjusting mechanism. It can be attached to the first cutting block or it can be attached to the surgical connecting device in accordance with the invention, if the latter is already connected to the first cutting block. If the second cutting block is also already connected to the surgical connecting device, then the marker device can also be attached to the second cutting block. In this state, a spatially fixed connection between the first and second cutting block is in particular provided by means of the connecting device. 
         [0021]    It is then possible to determine the position of the second cutting block by detecting the marker device. This position can be changed by actuating adjusting means on the adjusting mechanism. The marker device is thus spatially fixed relative to the parts of the adjusting mechanism for which a change in position relative to the bone is possible. It is in particular not spatially fixed relative to the parts of the adjusting mechanism which are fixed (spatially fixed) relative to the first body structure. It is in particular spatially fixed relative to the part of the adjusting mechanism which is formed for and in particular establishes a spatially fixed connection to the first cutting block. 
         [0022]    If the situation just described is given, then the position of the second cutting block is preferably adjusted relative to the second body part (for example, the femur), wherein the adjustment is monitored by means of the marker device and detecting the same. For example, the position of both the first body structure and the cutting block is displayed, by means of a navigation system, on a monitor of the navigation system. The navigation system in particular comprises a data processing device which processes the detection signals which are input into the data processing device from a camera. The camera detects said marker device. 
         [0023]    Preferably, the initial state is one in which the connecting device connects the first and second cutting block. The marker device is also preferably attached, spatially fixed, relative to the first cutting block. Since a connection between the first and second cutting block is provided by the surgical connecting device, a spatially fixed connection of the marker device relative to the second cutting block is also given in the state specified. Alternatively or additionally, a separate marker device can also be attached to the second cutting block. 
         [0024]    In the following, a first approach for fixing the two cutting blocks is described. A second, alternative approach is illustrated in conjunction with  FIG. 7 . 
         [0025]    In a first step, the position of the second cutting block relative to the second body structure is then preferably adjusted by means of the adjusting mechanism, by means of a marker device which is connected, spatially fixed, to the second cutting block. Once the desired position has been reached, the second cutting block is fixed to the second body structure. Once it has been fixed, the surgical connecting device is removed, such that the second cutting block is movable relative to the first cutting block. In a second step, the first cutting block is then moved relative to the first body structure, into the desired position, by means of the adjusting mechanism. A marker device which is connected, spatially fixed, to the first cutting block is used for this. The first cutting block is then fixed to the first body structure. Thus, both the first and second cutting block are attached to the first and second body structure, respectively, and exactly positioned. In the position then given, the incision is made on the respective body structure with the aid of the fixed cutting blocks. Optionally, the adjusting mechanism can be removed from the first body structure before the incision is made. Before the surgical connecting device is removed, a patella cutting device can also be attached to it. Alternatively, the surgical connecting device can already comprise the patella cutting device. The patella is then preferably cut before the surgical connecting device is removed. 
         [0026]    The invention also relates to: a surgical system comprising the surgical connecting device in accordance with the invention; a navigation system comprising the surgical system; and the use of the surgical connecting device, the surgical system and/or the navigation system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    Other advantages and features of the invention are disclosed in the following detailed description. Different features and different embodiments can be combined with each other. 
           [0028]      FIG. 1  shows a navigation system of the present invention, comprising a navigation device and a surgical system in accordance with the present invention; 
           [0029]      FIG. 2  shows a surgical system in accordance with the present invention, wherein the connecting device in accordance with the invention is just being removed; 
           [0030]      FIG. 3  shows two cutting blocks which are not connected and are fixed to the bone; 
           [0031]      FIG. 4  shows an embodiment of the surgical connecting device in accordance with the invention; 
           [0032]      FIG. 5  shows another embodiment of the surgical connecting device in accordance with the invention; 
           [0033]      FIG. 6  shows a surgical connecting device in accordance with the invention, comprising a marker device; 
           [0034]      FIG. 7  shows a surgical system in accordance with the invention, comprising a patella cutting device in accordance with a first embodiment; 
           [0035]      FIGS. 8 to 12  show a patella cutting device in accordance with a second embodiment, which is connected to the surgical connecting device by way of example. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]      FIG. 1  shows a surgical system in accordance with the present invention, comprising the components  100 ,  200 ,  300 ,  400  and  500 , which are illustrated in more detail in the following. The system comprises the surgical connecting device  100  in accordance with the invention.  FIG. 1  also shows a femur  10  and a tibia  20  and a navigation device  600 . Preferably, only one adjusting mechanism  400  is provided in accordance with the invention and attached to the tibia  20  via pins  410  and  412 . This one adjusting mechanism is sufficient, due to the use of the surgical connecting device  100  which connects a tibial cutting block  300  (the first cutting block) to a femoral cutting block  200  (the second cutting block) for adjusting the fixed position of the two cutting blocks. A reference star  500  is connected, spatially fixed, to the femoral cutting block  200 . In the embodiment shown, the reference star  500  is releasably connected via a snap-on connection  510  to a platform  520  which is in turn connected to the second cutting block  200 . The platform  520  can for example be inserted between the cutting guidance surfaces of the cutting block. In particular, it comprises abutment points in order to have a defined position of the reference star  500  relative to the cutting block  200 , in particular relative to the cutting guidance planes, and/or a defined relative position of the cutting plane relative to the reference star. In order to determine the relative position as exactly as possible, abutment points or locking elements are preferably provided on the platform  520  and can be moved to abut or engage with the cutting block. The platform  520  can also be formed such that it can be inserted between the cutting guidance planes into the cutting block ( 200  or  300 ) in as exact a fit as possible. A defined relative position between the cutting guidance planes and the reference star is thus given. The relative position is known to and stored in the navigation device  600 . 
         [0037]    The reference star  500  for example comprises marker elements  502 ,  504 ,  506  and  508  which can in particular be formed to be spherical. The marker elements can be formed to be active or passive. Active marker elements actively emit radiation or waves. Passive marker elements reflect radiation or waves. The radiation can in particular be electromagnetic radiation such as UV light, visible light or infrared light. The waves can in particular be ultrasound waves. The marker elements preferably have a pre-defined position relative to each other which is typical of the reference star  500 , such that the reference star  500  can be identified by a navigation device  600 . The navigation device  600  in particular comprises a detection device  610  consisting for example of two camera elements. It also preferably comprises a data processing device  620  which processes the detection signals of the detection device  610 , in particular in order to ascertain position data of the reference star  500  from them. Due to the known relative position between the reference star  500  and the cutting plane, this allows the position of the cutting plane to be calculated in a reference frame which is used by the navigation device. Reference stars are preferably likewise provided in the relevant body parts, i.e. for example a reference star  520  in the femur  10  and a reference star  530  in the tibia. Preferably, the relative position of a three-dimensional model of the body part (the femur or tibia) relative to the reference star ( 520  or  530 ) fixed to the body part is known to and in particular stored in the navigation device. It is therefore possible to determine the position of the cutting plane relative to the respective body part, i.e. for example relative to the femur  10  or tibia  20 , by means of the data processing device  620 . The data processing device  620  can then display the calculated result, in particular the relative positional relationship between a model of the body part (the femur and/or tibia) and the cutting plane, on a monitor  630 , and/or can transmit a signal to the monitor  630 , upon which said relative positional relationship is displayed on the monitor  630 . In this way, a surgeon can change the position of the cutting plane by adjusting the adjusting mechanism  400 , and check the position of the cutting plane on the monitor  620 . If the surgeon considers the position of the cutting plane relative to the femur  10 , in particular as displayed on the monitor  630 , to be a match or in accordance with the plan, the cutting block  200  can then be fastened to the femur  10  by means of pins (not visible in  FIG. 1 ).  FIG. 2  shows how this would then look after the reference star  500  and the surgical connecting device  100  have been removed. In  FIG. 2 , pins  210  and  212  are shown which are inserted into the femur  10  in order to fasten the cutting block  200  to the femur in the desired position. The connecting device  100  is just being removed. 
         [0038]    Once the connecting device  100  has been removed, the position of the first cutting block  300  is preferably then adjusted. A reference star is preferably again used for this, for example the reference star  500  which is shown in  FIG. 1 . The reference star, which is preferably fastened to a platform (for example, the platform  520 ), is connected to the cutting device  300  such that a defined position (which is known to the navigation device  600 ) of the cutting plane of the cutting block  300  relative to the reference star  500  is obtained. To this end, said platform  520  can for example be inserted into the gap  320  between the cutting guidance planes  322  and  324 . The platform is preferably formed to be an exact fit in the gap  320 , such that this cannot result in any tilting of the platform relative to the cutting plane. Alternatively, other connecting options for connecting the reference star to one of the cutting blocks  200 ,  300  can of course also be used, as has also been stated above. Locking connections can in particular be provided on the cutting block  200 ,  300 , in particular such that inserting the platform  520  into the gap  320  is not necessary, but rather a connection between the reference star  500  and the cutting block  200 ,  300  is established outside the gap  320 . 
         [0039]    The cutting block  300  is connected, preferably mechanically and preferably releasably, to the adjusting mechanism  400 . In particular, fastening means  420  and  422  are preferably provided on the adjusting mechanism  400 . By releasing these fastening means  420 ,  422  (for example, screws), it is then possible to remove the adjusting mechanism  400  from the cutting block  300 , if this is desired. A plurality of adjusting screws  430 ,  432 ,  434 , etc. are provided on the adjusting mechanism  400 , in order to be able to change the position of the cutting block  300  relative to the pins  412  and  410  via which the adjusting mechanism  400  is fastened to the tibia  20 . The position is also changed in this case until the desired position of the cutting block  300 , i.e. the desired position of the cutting plane of the cutting block  300 , relative to the tibia  20  has been achieved. 
         [0040]    By way of the surgical connecting device  100 , the adjusting mechanism  400  can accordingly be used twice. On the one hand, it can be used to adjust the position of the cutting block  200 , and can then also be used to adjust the position of the cutting block  300 . In this way, only one adjusting mechanism  400  has to be fastened to the bone, and damage to the bone is thus reduced. 
         [0041]      FIG. 3  shows the situation after the surgical connecting device  100 , the adjusting mechanism  400  and the reference star  500  (not shown in  FIG. 2 ) have been removed. Identical reference signs designate identical parts. This also applies to the other figures. 
         [0042]    In the state shown in  FIG. 3 , the tibial cutting block  300  is fastened to the tibia  20  at the desired position by pins  310 ,  312 . 
         [0043]      FIG. 4  shows the structure of a surgical connecting device  100  in accordance with the invention. The surgical connecting device  100  comprises front ends  111  and  121  which can each be inserted into contact gaps  232  and  332  of contact sections  230  and  330 . The thickness of the front ends and in particular of the contact parts  115  and  125  is preferably smaller than or equal to the gap thickness of the contact gaps  230  and/or  330 . Preferably, the contact parts  115  and  125  are formed to be an exact fit with the contact gaps  230  and  330 . The contact parts are preferably formed to be planar. In the section  112  of the contact part  115  facing away from the front end  111 , the contact part is preferably connected to the spacing section  130 , preferably integrally connected. The contact part  115  can however also be attached to the spacing section  130  in the region  112  using fastening means. In the embodiment shown, the contact part  115  is formed to be planar. Movable parts  113  and  114  are movable relative to the contact part  115 . In the embodiment shown, these movable parts are molded onto the contact part  115 , in particular integrally with it. Due to their material formation (for example, metal or plastic), the movable parts can be moved, in particular elastically, relative to the contact part by the action of a force. This means that after the action of the force ends, they automatically return to an initial position again. This is in particular used for a force-fit connection between the surgical connecting device  100  and the contact section  230  and/or  330 . When the surgical connecting device is inserted, the movable parts  113  and  114  thus press against the boundary of the contact gap  232 . Similarly, movable parts  124  and  123  (not shown) press against a boundary wall of the contact gap  332 , wherein the contact part  125  is inserted into the contact gap  332 . An abutment  116  and  126  is preferably situated at the rear end  112  and  222  of the contact parts  115  and  125 , and forms an edge of the spacing section and is thus arranged between the attaching section and the spacing section. Once the surgical connecting device has been completely inserted into the contact sections  230  and  330 , a front edge  234  and  334  of the contact section  230  and  330 , respectively, abuts the abutment  116  and  126 , respectively. In the embodiment shown in  FIG. 3 , this front edge is in each case in particular a front edge of the cutting plane gap  220  and  320 . 
         [0044]    The surgical connecting device  100  preferably has a U-shaped cross-section, as can be seen from  FIG. 4 . In the embodiment shown, the surgical connecting device has the shape of a three-dimensionally shaped letter U. The free ends of the three-dimensional letter U are inserted into the contact gaps  230  and  330 . An intermediate space  140  is situated between the contact part  115  and the contact part  125 . This intermediate space forms a space for parts  236  and  336  of the contact section  230  and  330 , wherein the parts  236  and  336  opposite each other when the cutting blocks  200  and  300  are connected by the surgical connecting device. 
         [0045]    The spacing section  130  can be divided into three sections  132 ,  134  and  136 , which are preferably integrally connected to each other. The sections  132  and  136  are each components of the arms of the three-dimensional letter U. The section  134  forms the base of the three-dimensional letter U. A handle  136 ′ can for example be attached to the base section  134 . This handle can of course also be attached to the sections  132  and  136 . However, the section  134  is preferred due to its superior accessibility. As also illustrated below, other devices—in particular a reference star (see  FIG. 6 ) or a patella cutting device (see FIG.  7 )—can also be attached to the spacing section  130  and in particular to its base part  134 , which connects the arms of the three-dimensional letter U. 
         [0046]    The movable parts  113 ,  114 ,  123  (not shown) and  124  each comprise an edge  113 ′,  114 ′,  123 ′ (not shown) and  124 ′ which tapers in the direction of the front end. The edge tapers in the direction of the front end and thus draws nearer to the exterior surface of the contact parts  115  and  125 . Due to this taper, the movable parts  113 ,  114 ,  123  (not shown) and  124  are each pressed further and further in the direction of the surface of the contact parts  115  and  125  when the surgical connecting device  100  is inserted into the contact sections  230  and  330  of the cutting blocks  200  and  300 , until the movable parts  113 ,  114 ,  123  (not shown) and  124  are aligned with the surface of the contact parts  115  and  125 . Since they can be elastically moved, the movable parts press against a wall of the cutting gap when connected to the cutting blocks  200 ,  300 , and thus ensure a force-fit connection. The movable parts  113 ,  114 ,  123  (not shown) and  124  can in particular be punched out of a common planar section by a punching process, said section in each case comprising a contact part and the assigned movable parts. The movable parts are then bent out of the plane which the contact parts form, so as to later be able to ensure a force-fit connection. 
         [0047]      FIG. 5  shows another embodiment of a surgical connecting device  100 . Parts with an identical or similar function are indicated by the same reference signs. A spacing section  130  again has a U-shaped configuration. Contact parts  115   a  and  115   b  on one arm of the U-shaped connecting device, and  125   a  and  125   b  on another arm of the U-shaped connecting device, are again spatially fixed relative to the spacing section  130 . Front ends  111   a ,  111   b  and  121   a ,  121   b  of the contact parts are formed so as to be inserted into the contact gaps. A movable part  113  comprises an insertion part  113   a  which can be moved into a plane in which the contact parts  115   a  and  115   b  lie. In the situation shown in  FIG. 5 , the insertion part  113   a  lies in the same plane as the contact parts  115   a  and  115   b . The movable part  113  also comprises a spring  113   b  and an actuating button  113   c  comprising a cylinder  113   d . The spring is supported with respect to the spacing section  130 , more specifically with respect to the part  132  of the spacing section  130 . If the button  113   c  is moved downwards, i.e. in the direction of the spacing section  130 , then it is necessary to work against the force of the spring  113   b  which is supported on the part  132 , wherein the cylinder  113   d  is pressed downwards until it assumes the position which can be seen in  FIG. 5 . When the push-button  113   c  abuts against an abutment  133  of the spacing section, the insertion section  113   a  is then also situated in the same plane as the contact parts  115   a  and  115   b.    
         [0048]    The lower part of  FIG. 5  shows an actuating button  123   c  when it is not being pressed. The insertion section  123   a  is therefore also not in the same plane as the contact parts  125   a  and  125   b . The spring  123   b  is relaxed. Therefore, as opposed to the cylinder  113   d , the cylinder  123   d  does not protrude into the intermediate space surrounded by the U-shaped spacing section  130 . Pressing the button  123   c  until the surface of the button  123   c  abuts against an abutment  137  of the spacing section  130  causes the insertion section  123   a  to lie in the same plane as the contact parts  125   a  and  125   b.    
         [0049]    Thus, once the buttons  113   c  and  123   c  have been pressed up to the abutments, the surgical connecting device can be inserted into the contact gaps of two cutting blocks. When the buttons  113   c  and  123   c  are released after the surgical connecting device has been inserted, a force-fit connection is thus obtained. The two cutting blocks  200 ,  300  are thus connected and thus spatially fixed relative to each other. The latter is a prerequisite for being able to adjust the desired position of two cutting blocks  200 ,  300  using one adjusting mechanism  400 . 
         [0050]      FIG. 6  shows a surgical connecting device  100  comprising a reference star  700  attached to it which comprises marker elements  702 ,  704  and  706 . The reference star  700  is attached to the base part  134  of the U-shaped surgical connecting device  100 . With the aid of the reference star  700 , it is possible to enable the surgeon to connect the surgical connecting device  100  to the contact sections  230 ,  330  of the cutting blocks  200 ,  300 , even when visibility is poor. The reference star  700  can also be used in addition to this purpose (or exclusively) as a navigation aid for positioning the second cutting block  200 , since a spatially fixed connection between the cutting block (in particular, the second cutting block  200 ) and the reference star  700  is given. 
         [0051]      FIG. 7  shows the situation when the femoral cutting block  200  is fixed. The cutting block  300  is likewise fixed using pins.  FIG. 7  relates to a second, alternative approach to the approach already described above. Accordingly, the position of the tibial cutting block  300  is adjusted first, with the aid of the adjusting mechanism  400 . Then, the tibial cutting block  300  is fixed. The position of the femoral cutting block  200  relative to the femur is then adjusted by shifting the tibia and the femur, and the femoral cutting block  200  is then fixed. While the femoral cutting block is being fixed, it is in particular connected, spatially fixed, to the tibial cutting block  300  via the connecting device  100 . In the alternative approach in accordance with  FIG. 7 , the adjusting mechanism  400  is accordingly only used to adjust the position of the tibial cutting block  300 . The distance between the tibial cutting block  300  and the femoral cutting block  200  is determined by selecting a suitable connecting device or by adjusting the distance between the cutting blocks by means of the adjusting mechanism described above. The femoral cutting block  200  can then be positioned relative to the femur by shifting the femur and/or tibia. Adjusting the position of the femoral cutting block  200  relative to the femur by moving the tibia  20  and the femur  10  can also be used in the first approach already described above, in particular in order to make a rough adjustment. A fine adjustment can then be made in the first approach by means of the adjusting mechanism. 
         [0052]    The adjusting mechanism  400  is also fastened to the tibia  20 . A patella cutting device  800  is connected to the connecting device  100 . In the scenario shown, the patella cutting device  800  is integrally connected to the surgical connecting device  100 . The patella cutting device  800  comprises an adjustable cutting slit part  810  and two dorsal processes  820 ,  822  for fixing the patella. The cutting slit  810  can be adjusted by a screw  812  in the directions indicated by A. The distance from a rear abutment surface  826  can likewise be adjusted relative to the front abutment surface  828  by a screw  824 . The front abutment surface  828  is connected, spatially fixed, to the connecting device  100 . The patella can be clamped between the front abutment surface  828  and the rear abutment surface  826  by adjusting the rear abutment surface  826 . 
         [0053]      FIG. 8  shows an alternative embodiment of the patella cutting device  800 . The distance between a rear abutment surface  826  and a front abutment surface  828  (see  FIG. 9 ) can be adjusted by a screw  830 . If the patella is clamped between the front and rear abutment surface, the patella height can be measured by means of a scale  833  and a scale mark  832 . The rear abutment surface  826  is movable relative to the front abutment surface and relative to a frame  870 . In accordance with one embodiment, a reference star  840  is attached to the rear abutment surface  826  or to a part which is spatially connected to it, for example the scale  833 . The patella height can thus be automatically determined by a navigation system (which for example comprises the navigation device  600 ) by reading off the position of the reference star  840 , without it being necessary to read off the scale  833  using the scale mark  832 . Preferably, though not compulsorily, the patella cutting device comprises the connecting device  100  in accordance with the invention. The patella cutting device  800  can thus also be used without the connecting device  100  in accordance with the invention. In particular, the patella cutting device  800  without the connecting device  100  relates to another invention. This patella cutting device thus comprises an adjusting means  830  (for example, a turning knob  830 ) in order to adjust the distance between the front and rear abutment surface. It also preferably comprises an adjusting means (for example, an adjusting wheel  850 ) in order to adjust the cutting height. The adjusting wheel  850  is mechanically connected to a cutting slit part  810  which comprises a cutting slit  812  for inserting a blade for cutting the patella. A reference star  815  can likewise be attached, spatially fixed, to the cutting slit part  810 . The adjusted cutting height can be determined by detecting the reference star  815  by means of the navigation device  600 . Alternatively, the cutting height can be read off by reading off the scale  817  and the scale mark  818  (see  FIG. 12 ). 
         [0054]    An adjusting part  860  allows patella abutment surfaces to be adapted to the diameter of the patella, as shown in  FIGS. 10 and 11 . An upper frame  870  can be lowered in the direction indicated by B. The lowered situation is shown in  FIG. 11 . In this situation, the frame  870  can then be fixed using the turning knob  860 .  FIG. 12  shows another view of the patella cutting device  800 . The frame  870  is situated in its lowered position. This means that the full diameter of the patella  900  lies between a part  872  of the frame  870  and a bearing surface  874  which is preferably provided with nubs. The bearing surface  874  is preferably connected, spatially fixed, to a stand  862 . The bar  874  of the frame  870  is in particular movable in the direction B (see  FIG. 10 ). The bar  874  is fixed relative to the stand  862  by the adjusting wheel  860 . In the embodiment shown in  FIG. 11 , the stand  862  is spatially fixed to the connecting device  100 . As shown in  FIG. 12 , the patella diameter can be read off from a scale  876 , when the part  872  of the frame  870  and the bearing surface  874  are each in contact with the boundary of the patella  900 , in particular at opposite locations. The boundary of the patella  900  is typically oval or circular and runs along the exterior surface of the patella  900 , where it has the largest circumference. 
         [0055]    Computer program elements of the invention may be embodied in hardware and/or software (including firmware, resident software, micro-code, etc.). The computer program elements of the invention may take the form of a computer program product which may be embodied by a computer-usable or computer-readable storage medium comprising computer-usable or computer-readable program instructions, “code” or a “computer program” embodied in said medium for use by or in connection with the instruction executing system. Within the context of this application, a computer-usable or computer-readable medium may be any medium which can contain, store, communicate, propagate or transport the program for use by or in connection with the instruction executing system, apparatus or device. The computer-usable or computer-readable medium may for example be, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared or semiconductor system, apparatus, device or medium of propagation such as for example the Internet. The computer-usable or computer-readable medium could even for example be paper or another suitable medium on which the program is printed, since the program could be electronically captured, for example by optically scanning the paper or other suitable medium, and then compiled, interpreted or otherwise processed in a suitable manner. The computer program product and any software and/or hardware described here form the various means for performing the functions of the invention in the example embodiments. 
         [0056]    Although the invention has been shown and described with respect to one or more particular preferred embodiments, it is clear that equivalent amendments or modifications will occur to the person skilled in the art when reading and interpreting the text and enclosed drawings of this specification. In particular with regard to the various functions performed by the elements (components, assemblies, devices, compositions, etc.) described above, the terms used to describe such elements (including any reference to a “means”) are intended, unless expressly indicated otherwise, to correspond to any element which performs the specified function of the element described, i.e. which is functionally equivalent to it, even if it is not structurally equivalent to the disclosed structure which performs the function in the example embodiment or embodiments illustrated here. Moreover, while a particular feature of the invention may have been described above with respect to only one or some of the embodiments illustrated, such a feature may also be combined with one or more other features of the other embodiments, in any way such as may be desirable or advantageous for any given application of the invention.