Abstract:
For performing an osteotomy operation at a selected location on a patient&#39;s bone, a cutting apparatus comprising a screw device having a tubular shell with at least one longitudinal slot through said shell. A knife holder is slidable longitudinally in the bore to pivotally support at least one knife for displacement between a closed position and an opened position. In its closed position the knife is contained within the bore, and is pivotable to said opened position to project outwardly through the slot to perform the cutting operation, The knife is displaced longitudinally in the bore by an applicator operable to be telescopically displaced in the bore and operable upon its longitudinal displacement to contact an extended end of said knife and pivot the knife into its opened position through the slot, and thereafter to displace said knife holder toward the opposite end of said tubular shell. A spring is positioned between the knife holder and the opposite end of the bore to provide a bias resisting the longitudinal displacement of said knife holder, and upon retraction of said applicator, to return the knife to its closed position.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates to a cutting apparatus for performing osteotomy that introduces essential characteristics of novelty and significant advantages compared to the currently known and used practices. 
         [0002]    Specifically, the invention proposes the development of a cutting apparatus for performing osteotomy using a cannulated screw device that enables the performance of straight, parallel, cuts in different planes and at the angles specified. This guarantees faster and more complete healing of the bone in which the operation is performed. Subsequent removal of the cannulated screw enables more complete return of blood supply to the affected zone. 
         [0003]    The invention&#39;s field of application is the industrial design and manufacture of medical equipment and devices in general, and of the performance of osteotomies in particular. 
       BACKGROUND OF THE INVENTION 
       [0004]    The term osteotomy is used by persons skilled in the art to describe an operation in which the surgeon performs one or more cuts in a patient&#39;s bone in order to achieve changes in its position. Osteotomy operations can, therefore, be carried out, for example to lengthen or shorten a leg bone, correct curvature or angulations, to correctly place the fragments of a broken bone or even sometimes in hip operations to alter the position of the femur. 
         [0005]    Currently, two basic cutting apparatuses are known for performing osteotomies: a first apparatus that uses cutting saws and a second apparatus that uses milling cutters. In the first case, the use of a cutting saw requires open surgery, with the drawback that osteotomies are performed by the effort of the surgeon leading to characteristics of precision that are sometimes less than desired; there is also the drawback that the saw vibrates and heats up and the equipment cost is fairly high. 
         [0006]    In the second case, that is osteotomy performed with milling cutter, the operation is often usually made through a small incision, this technique being known as minimally invasive surgery (MIS) or laparoscopic surgery. Logically, this can also be performed using open surgery. Similarly to the first case, the surgery is performed by the effort of the surgeon, with the drawbacks of lack of precision and difficulty in controlling the cutter, together with the unwanted heating in the equipment. This equipment is also expensive. 
         [0007]    When an osteotomy operation is performed, the surgeon requires the cutting planes to be very parallel so that the healing takes place as quickly as possible. Also, the surgeon must prevent bone fragments from breaking, both to achieve fast healing and to ensure effective surgical correction. It is also necessary to guarantee a good blood supply to the area of the operation because the arteries feeding the bone are destroyed during surgery. Also, to guarantee the maintenance of the correction desired in the operation, effective fixing with the help of pins or screws is required. 
       SUMMARY OF THE INVENTION 
       [0008]    Taking into consideration the currently existing requirements in the state of the art and the drawbacks associated with the known apparatus and equipment, the current invention&#39;s main purpose is to provide an apparatus through which effective solutions could be provided to overcome such drawbacks. This objective has been fully achieved by the apparatus to be described below, whose main characteristics are set down in the claims. 
         [0009]    In essence, the apparatus of the invention can be used in both types of osteotomy described above: open surgery or keyhole surgery. The apparatus of the invention implements the embodiment of a cannulated screw device, i.e. internally hollow, prepared to be introduced into the patient&#39;s bone in the position in which the osteotomy is to be performed. Once the screw has been installed in the correct position, a knife holder with a cutting knife is positioned in the the hollow bore of the screw in such as way that on displacing it along the bore inside the screw, the knife is opened, performing the osteotomy precisely in the chosen location. An appropriate selection of various cutting tools with different cutting angles enables the surgeon to select the type of osteotomy that is performed. Also, depending on the position of the knives, the osteotomy operation can be performed in different planes and angles. Additionally, there is a spring device fitted inside the cannulated screw that enables the retraction of the cutting tool once the osteotomy has been performed. 
         [0010]    As will be understood, an apparatus made in the way proposed by the invention is a much simpler and more efficient apparatus than those known up to now for this type of operation, enables the surgeon to obtain substantially better results in terms of precision and speed compared to the previous technique and the method is much cheaper than the known apparatus briefly described above. 
         [0011]    In a first embodiment of the invention, the knife holder and the hollow bore of the screw both have a circular cross section, and it was found that when the applicator is threaded into the proximal end of the screw, the rotary movement of the applicator tends to cause the knife holder to rotate so that the knife is not precisely registered with the slot in the tubular shell of the screw. In a preferred embodiment, the knife holder and the hollow bore of the screw have complementary non-circular cross sections to prevent rotary movement of the knife holder in the bore, and to maintain the knife in registry with the slot in the tubular shell. 
         [0012]    Preferably the non-circular cross sections of the knife holder and the bore provide guide surfaces which assure smooth displacement of the knife holder as it is displaced by the applicator, so that the knife travels along the length of the slot as it perform the desired cutting operation on the bone. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    These and other characteristics and advantages of the invention will be better understood from a detailed description of the invention, given only for illustration purposes, with reference to the figures that accompany it. 
           [0014]      FIG. 1  is an elevation view partially sectioned of an example of a preferred embodiment of the system for performing osteotomy with a single knife in the knife holder shown in the closed non-operational position; 
           [0015]      FIG. 2  is a similar view to  FIG. 1 , with the knife in a protruding opened position; 
           [0016]      FIG. 3  is a sectional view of the cutting apparatus with the knife in the open operational position taken on the line A-A′ in  FIG. 2 ; 
           [0017]      FIG. 4  is an elevation view of the cutting apparatus shown in  FIGS. 1-3  of the previous figures, showing the slot for the protrusion of the knife; 
           [0018]      FIG. 5  is an exploded elevation view partially sectioned of the cutting apparatus of  FIG. 1 ; 
           [0019]      FIG. 6  is an elevation view, partially sectioned, of one variant of the preferred embodiment of the system, with two parallel knives shown in the open operational position; 
           [0020]      FIG. 7  is an upper plan view of the knife holder of  FIG. 6  with the knives in the open operational position; 
           [0021]      FIG. 8  is a sectional view of the knife holder of  FIGS. 6 and 7 , sectioned vertically by the plane of one of the knives and with the two knives in non-operational closed positions; 
           [0022]      FIGS. 9   a ,  9   b , and  9   c  are completely schematic views of the components making up a first embodiment of the apparatus with a single knife of the invention; 
           [0023]      FIGS. 10   a  and  10   b  are completely schematic views of a cutting apparatus with two knives in positions of action and withdrawal respectively; and 
           [0024]      FIGS. 11   a ,  11   b  and  11   c  are completely schematic views of the possible positions in which the apparatus with multiple knives can work. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0025]    As described above, the detailed description of the embodiments of the apparatus of the invention will follow, with the help of  FIGS. 9   a  through  11   c  showing schematic views of the components comprising the first embodiments of the cutting apparatus and its operational possibilities. The same components are identified using the same numerical references across the various figures. 
         [0026]    Referring in first place to  FIGS. 9   a ,  9   b  and  9   c , the cutting apparatus of the invention comprises a cannulated screw  51  having a tubular shell with external threads (not shown) adapted to be used in an osteotomy operation, with its insertion into the precise point of the patient&#39;s bone where it is desired to make the cut. The screw has a hollow interior  62  to allow the passage of one or more cutting knives  52  pivotally mounted in a knife holder  53  for opening and closing pivotal movement. Hereinafter and to simplify the description, reference will be made to a single cutting knife  52 , although it should be understood that the description is equally applicable without any change to the case where the knife holder  53  holds more than one knife. 
         [0027]    As can be seen in the figures, the tubular shell of the screw  51  has at least one longitudinal slot  63 , of a width sufficient to allow the knife  52  pivotally mounted in the knife holder  53  to be projected outwardly to an opened position and to be displaced along the length of the slot  63  as required. The screw  51  also has a grasping portion  54 , of greater diameter, at the proximal end thereof. The grasping portion has internal; threads  54 - 1  adapted to engage external threads  55 - 1  of an applicator  55 . 
         [0028]    If we observe  FIG. 1   c , the form of application and action of the apparatus of the invention can be deduced clearly and simply. With the screw  51  positioned in the place where the osteotomy is to be performed, the knife holder  53  with the knife  52  is introduced into the hollow interior bore  62  of the screw. Then the applicator  55  is telescopically introduced into the screw  51 , by threaded engagement of its external threads  55 - 1  with the internal threads  54 - 4 . The applicator  55  advances longitudinally along the hollow interior bore  62  as it rotates, When the front part  55 - 2  of the applicator reaches the position of the proximal end  72  of the knife  52 , its causes the knife to pivot to the opened position, with the consequent emergence of the knife&#39;s cutting zone through the longitudinal slot  63 . From this time, the cutting apparatus is ready to perform a perfectly straight and guided cut, in the place selected, with absolute precision given the immobility of the screw  51  screwed into the bone. The position of the cut with the knife elevated is shown in broken lines in  FIG. 9   c  with the numerical reference  52 ′ 
         [0029]      FIGS. 9   a  and  9   b  are completely equivalent, with the only difference that they are rotated by 90° with respect to the longitudinal axis. In the same way, complementarily with the position of the screw  51 , the knife holder  53  appears equally in both figures rotated by the same angle. This form of representation graphically illustrates the description just made in the sense that the knife  52  is introduced into the internal space  62  of the screw  51 , orientated in such a way that when it pivots, it emerges without difficulty through the slot  63  as has been explained with reference to  FIG. 9   c.    
         [0030]    As was previously described, the screw  51  includes therein a spring  56  positioned between the knife holder  53  and the extreme distal end of the hollow interior  62 . This situation is clearly visible in  FIG. 10   a , where the spring  56  presses against the knife holder  53 , opposing the displacement of the knife  52  in the longitudinal direction of the screw and helping, therefore, the opening or pivoting of the knife  52  towards its operational position (position of the cut). In the case of  FIGS. 10   a  and  10   b , there is a second knife  52 - 1  shown, associated with the same knife holder  53 , in opposition to the first knife  52 , and illustrating an alternative embodiment of the invention. 
         [0031]    When the cut has been made in the position selected, the spring  66  is an essential element to help extract the knife holder  53  with the knife/knives ( 52  and  52 - 1 ) because the bias of the spring  66  when the surgeon retracts the applicator  55  generates a force on said knife holder  53  in the direction towards the proximal end of the screw, i.e. towards the open end of the screw through which the knife holder  53  was initially introduced. This action is essential for extraction and recovery of the knife holder  53  and of the associated cutting knife/knives  52  and  52 - 1 . The retraction of the applicator permits the knife/knives to assume to the closed position shown in  FIG. 10   b.    
         [0032]    As a complement to what has been described above,  FIGS. 11   a ,  11   b  and  11   c  illustrate cutting options that can be achieved with the apparatus of the invention. In  FIG. 11   a , the knife holder  53 - 1  includes two knives  52 - 1  and  52 - 2  that are fitted in such as way, for example being spaced apart longitudinally of the screw  51 , so that they form an angle of 90° to each other. The cut that can be made with the apparatus comprising the knife holder  53 .- 2  in  FIG. 11   b  is a double cut made by two knives  52 - 1  and  52 - 3  at an acute angle to each other, which logically could vary in a wide range of angular magnitudes as required, although in the case illustrated in the example in  FIG. 11   b  is an angle of around  450 . In the option illustrated in  FIG. 11   c , the cut made by the knives  52  and  52 - 1  in the knife holder  53  are in opposing directions, parallel to each other but in different planes. It is understood that there are many other options that are equally applicable to the apparatus of the invention and are all considered to be included in the invention although they have not been expressly described. 
         [0033]    It is not considered necessary to further extend the present description for a person skilled in the art to understand the scope and the advantages derived from it, as well as to carry out a practical embodiment of the object described. 
         [0034]    Notwithstanding the above, and given that the description only corresponds to a first embodiment of the invention, it is clear that in essence many variations of detail can be made, all of them protected, that may affect the characteristics of the invention such as the form, size or manufacturing materials of the whole device or of its parts or any other changes that do not alter the essence of the invention. 
         [0035]    Additional embodiments of the invention are illustrated in  FIGS. 1-5  and  FIGS. 6-8  respectively. In the above-described embodiment of the invention, the knife holder and the hollow bore of the screw both have a circular cross section, and it was found that when the applicator is threaded into the proximal end of the screw, the rotary movement of the applicator  55  tends to cause the knife holder  53  to rotate so that the knife is not precisely registered with the slot  63  in the tubular shell of the screw. To minimize this effect, the front part  55 - 2  of the applicator was designed to minimize the transfer of rotary motion to the knife holder  53 . In the preferred embodiments illustrated in  FIGS. 1-8 , the knife holder and the hollow bore of the screw have complementary non-circular cross sections to prevent rotary movement of the knife holder in the bore. It is noted that in  FIG. 9   a , the proximal end of the slot  63  is positioned adjacent the grasping portion  54 , however the end may be spaced from the grasping portion  54  at the proximal end of the apparatus to provide a closed housing for the knife holder  53  which will maintain the knife it its retracted closed position during the insertion of the cutting apparatus into the selected location on a patient&#39;s bone. 
         [0036]    The embodiments of the system for performing osteotomy shown in  FIGS. 1-8  comprise a cannulated screw device  1 , a knife holder  3 , carrying a single knife  2  in  FIGS. 1 and 5  and two parallel opposed knives  2 ,  2 ′ in  FIGS. 6 to 8 , an applicator or actuator  5  and a spring  6 . The screw device  1  has a tubular shell with an external screw thread  11  for its insertion into the bone to be treated, a hollow interior bore  12  for mounting the spring  6  and the knife holder  3  that can move longitudinally, a longitudinal slot  13 ,  13 ′ for each of an the knives  2 ,  2 ′ of the knife holder  3  and a rear opening  14  on which an annular detachable collar  4  is mounted, which has a threaded orifice  41  of smaller diameter than the hollow interior  12  of the tubular shell. The applicator  5  is threaded as indicated at  5 - 1  so that, by threading it into the orifice  41 , the applicator may be advanced to greater or lesser extent into the hollow interior of the cannulated screw device  1 . 
         [0037]    As can be seen clearly in  FIG. 3 , the knife holder  3  and the hollow bore  12  have a non-circular cross-sections and have complementary longitudinal guides  31 ,  15  on the lateral opposing surfaces. The guides are shown on both surfaces, flat and parallel, mutually opposed and longitudinally orientated, enabling the longitudinal movement of the knife holder along the hollow bore  12  but prevent its rotation inside said hollow bore  12 . 
         [0038]    The flat surfaces  31 ,  15  referred to above are orientated in such as way that the knife holder  3  can only be mounted in a specific angular orientation, in which each knife  2 ,  2 ′ registers with the respective longitudinal slot  13 ,  13 ′. 
         [0039]    Each knife  2 ,  2 ′ is mounted in the knife holder on a pivotal axis of folding  21 ,  21 ″ that enables its rotation between a non-operational closed position, shown in  FIGS. 1 and 7 , and an operational opened position, shown in  FIGS. 2 and 6  in which it protrudes laterally from the screw device  1  through the corresponding slot  13 ,  13 ′. 
         [0040]    The proximal end of each knife  2 ,  2 ′ has a heel  22 ,  22 ′ that emerges from the rear end of the knife carrier  3  with a specific inclination when the knife  2 ,  2 ′ is in the non-operational closed position, 
         [0041]    The applicator  5 , externally threaded as indicated at  5 ′, is mounted in the threaded orifice ( 41 ) of the annular component ( 4 ) and can be introduced to greater or lesser extent into the hollow interior bore  12  of the screw device  1 . As can be seen in  FIGS. 1 and 2 , when the applicator starts to be introduced, by threading, into the hollow interior  12  of the screw device  1 , it initially acts against the heel  22  of the knife  2  causing it to pivot around the axis  21  towards an operational opened position, shown in  FIGS. 2 and 3 , in which the knife protrudes through the slot  13 . As the applicator  5  is introduced further into the hollow interior bore  12 , it causes a longitudinal advance of the knife holder  3 , maintaining the knife in an operational position, to perform a straight cut in the patient&#39;s bone. This operation occurs in the same way when the knife holder  3  has two knives  2 ,  2 ′ and the screw device has two slots  13 ,  13 ′, as can be seen in  FIG. 6 . 
         [0042]    The spring  6  which is mounted in the hollow interior bore, in front of the knife holder  3 , causes the withdrawal of said knife holder  3  as the applicator  5  is removed from the hollow interior of the screw device. As with the embodiment shown in  FIG. 9   a , the proximal ends of the slot  13  or slots  13 ,  13 ′ may be spaced from the proximal end of the tubular shell to provide a closed housing for the knife holder  3 ,  3 ′ when the knives  2 , 2 ′ are in their closed positions. 
         [0043]    It should be noted that when the knife holder  3 ′ pivotally mounts two knives  2 ,  2 ′, as shown in  FIGS. 6-8 , each knife has its own pivotal axis  21 ,  21 ′, as deter mined by the two pivot pins in the holder  3 . As shown in  FIG. 8 , the proximal ends  22 ,  22 ′ of each knife has a cut out  23 , 23 ′ adapted to surround the pivot pin of the other knife when the knives are retracted into their closed positions. 
         [0044]    Having sufficiently described the nature of the invention and an example of the preferred embodiments, it is hereby declared that the materials, form, size and arrangement of the components described can all be modified, provided that this does not change the essential characteristics of the invention that are claimed below.