Abstract:
A dual-bladed surgical saw and methods of use are described. A preferred embodiment of the dual-bladed surgical saw include a saw body having a blade assembly attached thereto, the blade assembly being positioned about a rotational axis. A first blade is radially spaced about the rotational axis, extending outwardly from the blade assembly substantially parallel to the rotational axis, and terminating at a first cutting surface. A second blade is radially spaced about the rotational axis, extending outwardly from the blade assembly parallel to the rotational axis, and terminating at a second cutting surface. An oscillator mechanism is coupled to the first and second blades for simultaneously reciprocating the first and second blades. The first blade is independently rotatable relative to the second blade about the rotational axis for defining a predetermined cutting angle between the first blade and second blade.

Description:
This is a continuation-in-part of application Ser. No. 13/597,851, filed Aug. 29, 2012 and titled “Dual Bladed Surgical Saw and Methods of Use,” which is incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to the field of surgical saws and, more particularly, to dual-bladed surgical saws for shaping bone. 
     BACKGROUND 
     Certain surgical procedures require bones to be cut at precise angles. For example, the Austin, or Chevron, bunionectomy requires the medical professional to make a precise sixty degree angled cut into the first metatarsal head so that the two resulting metatarsal sections can be translated sideways and affixed together. Likewise, in knee replacement surgery, the lower end of the femur must be cut to match the shape of the particular knee replacement implant that will be used. 
     In a typical knee replacement procedure, the femur is shaped by making a series of cuts with a single-bladed surgical saw. A cutting guide is used to help the surgeon make the appropriately angled cuts. The cutting guide is pinned in place on the femur and the saw is used to make the first cut. The cutting guide is then repositioned on the femur and the saw is used to make the second cut. These repositioning and cutting steps are performed sequentially until all of the necessary cuts are complete. 
     Although the conventional knee replacement procedure works well, it is inefficient and more complicated than it needs to be. 
     SUMMARY 
     The various aspects of the invention solve this problem by providing a dual-bladed surgical saw, including a pair of blades that can be set at a desired angle relative to one another for simultaneously making a pair of cuts that are angled relative to one another at the desired angle. 
     In a preferred embodiment, the dual-bladed surgical saw includes a saw body having a blade assembly attached thereto, the blade assembly being positioned about a rotational axis. A first blade is radially spaced about the rotational axis, extending outwardly from the blade assembly substantially parallel to the rotational axis, and terminating at a first cutting surface. A second blade is radially spaced about the rotational axis, extending outwardly from the blade assembly parallel to the rotational axis, and terminating at a second cutting surface. An oscillator mechanism is coupled to the first and second blades for simultaneously reciprocating the first and second blades. The first blade is independently rotatable relative to the second blade about the rotational axis for defining a predetermined cutting angle between the first blade and second blade. 
     In another preferred embodiment, a dual-bladed surgical saw includes a saw body having a first blade assembly and a second blade assembly attached thereto. The first blade assembly includes a first oscillator for reciprocating a first blade having a cutting surface at an end of the first blade opposite the first oscillator. The second blade assembly includes a second oscillator for reciprocating a second blade having a cutting surface at an end of the second blade opposite the second oscillator. The first blade is independently rotatable relative to the second blade about a rotational axis passing through the first and second blade assemblies for defining a predetermined cutting angle between the first blade and second blade. 
     In a method aspect of the invention, a method of shaping bone for mating the bone with an implant having an implant surface adapted to abut the shaped bone when installed involves positioning the blades of a dual-bladed surgical saw to a predetermined cutting angle and simultaneously making first and second adjacent cuts separated by the cutting angle by contacting the bone with the first and second blades. A third cut adjacent to the second cut and separated from the second cut by the same or a different cutting angle is formed in the bone by passing the first blade across the second cut while the second blade makes the third cut. 
     These aspects of the invention, along with other additional aspects, embodiments, and features will be better understood by referring to the accompanying drawings and the Detailed Description of Preferred Embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a right side perspective view of a dual-bladed surgical saw, according to a first apparatus aspect of the invention; 
         FIG. 2  is a front elevation view of the blade assembly of the dual-bladed surgical saw of  FIG. 1 ; 
         FIG. 3  is an exploded side cross-sectional view of the blade assembly of  FIG. 3 ; 
         FIGS. 4   a - c  are right side elevation views of various saw blade shapes that may be used with the dual-bladed surgical saw; 
         FIG. 5  is a right side perspective view of a dual-bladed surgical saw, according to a second apparatus aspect of the invention; 
         FIG. 6  is a side cross-sectional view of a fastener, goniometer, and second blade assembly arm taken at section IV-IV of  FIG. 5 ; 
         FIG. 7  is a right side perspective view of a dual-bladed surgical saw, according to a third apparatus aspect of the invention; 
         FIG. 8  is a right side perspective view of a dual-bladed surgical saw, according to a fourth apparatus aspect of the invention, with one of the blades removed; 
         FIG. 9  is a top plan view of an alternate form of the cutting head, according to a fifth apparatus aspect of the invention; 
         FIG. 10  is a partial front view of the cutting head shown in  FIG. 9 ; 
         FIG. 11  is a rear isometric view of a dual-bladed surgical saw, according to a sixth apparatus aspect of the invention; 
         FIGS. 12-14  illustrate a method of use for a dual-bladed surgical saw, according to a first method aspect of the invention; 
         FIG. 15  is a schematic illustration of a lower portion of a femur and a knee replacement implant that is to be affixed thereto; and 
         FIGS. 16   a - d  illustrate a method of use for a dual-bladed surgical saw, according to a second method aspect of the invention; 
         FIG. 17  illustrates the implant being placed onto the shaped femur; 
         FIGS. 18   a  and  b  illustrates the use of a template as a cutting guide; 
         FIG. 19  is a right side perspective view of a sagittal-type dual-bladed surgical saw with a fixed cutting angle, according to a seventh apparatus aspect of the invention; and 
         FIG. 20  is a rear isometric view of an oscillator-type dual-bladed surgical saw with a fixed cutting angle, according to a seventh apparatus aspect of the invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In the Summary above and in the Detailed Description of Preferred Embodiments, reference is made to particular features (including method steps) of the invention. Where a particular feature is disclosed in the context of a particular aspect or embodiment of the invention, that feature can also be used, to the extent possible, in combination with and/or in the context of other particular aspects and embodiments of the invention, and in the invention generally. 
     The term “comprises” is used herein to mean that other ingredients, features, steps, etc. are optionally present. When reference is made herein to a method comprising two or more defined steps, the steps can be carried in any order or simultaneously (except where the context excludes that possibility), and the method can include one or more steps which are carried out before any of the defined steps, between two of the defined steps, or after all of the defined steps (except where the context excludes that possibility). 
     In this section, the invention will be described more fully with reference to certain preferred embodiments. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will convey preferred embodiments of the invention to those skilled in the art. 
     Referring initially to  FIGS. 1 and 2  a dual-bladed surgical saw  10 , according to a first apparatus aspect of the invention includes a saw body  12 , a cutting head  14 , and a switch  16  for turning the motion of a pair of saw blades  16 ,  18  on and off. An angle A 1  between the saw blades  16 ,  18  is adjustable by manipulating an adjustment pin  20 . 
     The cutting head  14  includes a first blade assembly  22  and a second blade assembly  24 . The first blade assembly  22  includes the first blade  17 , whereas the second blade assembly  24  includes the second blade  18 . Each blade  17 ,  18  is attached to an oscillator  26 ,  28  at one end and includes a cutting surface  30  at the opposite end. In the preferred embodiment shown, the cutting surface is in the form of saw teeth, but any other conventional cutting surface may be used. 
     The body  12  houses electrical components used to operate the saw  10  via the switch  16 . In this particular embodiment, a battery  32  provides power to the cutting head  14  to oscillate the blades  17 ,  18 . When the switch  16  is in the on position, the first and second oscillators  26 ,  28  oscillate, causing the first and second blades  17 ,  18  to reciprocate as indicated by the arrows. Other types of power sources such as other electric or even pneumatic power sources can be used to drive the oscillators  26 ,  28  without departing from the scope of the invention. 
     The first and second blades  17 , 18  are positioned at an angle A 1  relative to one another. The angle may be predetermined depending on the type of surgery to be performed and is adjustable so that multiple angled cuts can be made using the same saw in the same surgical procedure. 
     As best shown in  FIGS. 2 and 3 , the adjustment pin  20  is adapted to allow the angle between the blades  17 , 18  to be adjusted by loosening and tightening the first and second blade assemblies  22 ,  24  against a blade assembly mounting member  36 . In the embodiment shown, the adjustment pin  20  is a threaded fastener, which passes through an elongated slot  38  formed through the first blade assembly  22  and second blade assembly  24  and fits into a threaded bore  40  in the blade assembly mounting member  36 . By loosening the adjustment pin  20 , the force holding the pieces together is reduced, allowing the first and second blade assemblies  22 , 24  to be rotated to the desired angle A 1 . If desired, the radial distance between each blade  17 , 18  can be increased or decreased by sliding the respective blade assembly  22 , 24  along its respective slot  38  in the direction shown by the arrows  42 . 
     Referring to  FIGS. 4   a - c , the different shaped blades  44 ,  44 ′,  44 ″ can be mounted on the blade assembly  22 , 24  to provide additional adaptability to various surgical procedures. The blades  44 , 44 ′, 44 ″ include an indented attachment member  45  for attachment to the saw  10 . The blades  44 ,  44 ′,  44 ″ can have varying widths so that the saw  10  can be adapted to different sizes of bone or different osteotomies. 
     Referring to  FIGS. 5 and 6 , a dual-bladed surgical saw  50 , according to a second apparatus aspect of the invention, includes a goniometer  52  for setting the blade angle A 1  between the first and second blades  17 ,  18 . In this embodiment, the first blade assembly  22  includes a first blade assembly arm  54  attached to and extending therefrom. The second blade assembly includes a second blade assembly arm  56  attached to and extending therefrom. The goniometer  52  is arcuate shaped and is attached at one end to the first blade assembly arm  54  and at the other end to the second blade assembly arm  56 . A goniometer slot  58  is formed through the goniometer  52  for allowing a goniometer fastener  60  to slide therethrough as the angle A 1  is adjusted. Angular markings  62  are positioned along the goniometer slot  58  to indicate the angle A 1 . 
     As best shown in  FIG. 6 , the goniometer fastener  60  includes a threaded end the feeds through a threaded bore  62  in the second blade assembly  24  for releasably fix the position of the goniometer  52 . The goniometer fastener  60  slides through the goniometer slot  58  as shown. The angle A 1  is defined by the position of the goniometer fastener  60  along the goniometer slot  58  as indicated by the angular markings  62 . 
     In use, the goniometer fastener  60  is inserted through the goniometer slot  58  and threaded loosely into the threaded bore  62  in the second blade assembly arm  56 . The blade angle A 1  is set as desired by rotating the second blade assembly arm  56  until the desired angle A 1  is obtained. The goniometer fastener is then tightened into the threaded bore  60 , pressing the goniometer  52  between the second blade assembly arm  56  and the head of the goniometer fastener  60  to fix the blade angle A 1  in position. 
     Referring to  FIG. 7 , a dual-bladed surgical saw  70 , according to a third apparatus aspect of the invention, includes a pair of shims  72  that are used to set the blade angle A 1 . The shims  72  are inserted between the first and second blade assembly arms  54 , 56  as appropriate for obtaining the desired blade angle A 1 . The use of shims  72  is especially useful where a pre-determined blade angle A 1 , such as sixty degrees is desired. The blade angle can quickly be obtained by inserting the appropriately sized shims  72 . 
     Referring to  FIG. 8 , a modified dual-bladed surgical saw  80 , according to a fourth apparatus aspect of the invention, is modified by having the first blade assembly (not shown removed so that the cutting head  14  only includes the second blade assembly  22  with the second blade  18  attached thereto. In this embodiment, the saw  80  may be used as a conventional, single bladed surgical saw. 
     Referring to  FIGS. 9 and 10 , a dual-bladed surgical saw  90 , according to a fifth apparatus aspect of the invention, includes a different type of cutting head  14 . In this embodiment, the mounting member  36  has a pair of flexible arms  92  extending outwardly therefrom to a goniometer  94 . The blades  17 ,  18  are mounted about blade mounts  96 , 98  at a distal end relative to the flexible arms  92 . A pair of blade mount fasteners  100  fasten the blade mounts  96 , 98  to the flexible arms  92 . The fasteners  100  pass through a goniometer slot  102 . 
     In this embodiment, the blades  17 ,  18  can be rotated 360 degrees about an axis passing through the respective fastener  100  as illustrated by the arrows  104 . The blades  17 , may also be positioned along the slots  102  to the desired blade angle as illustrated by arrows  106 . The flexible arms  92  flex as the blade angle is changed. 
     It should be noted that the apparatus aspects of the invention described above are directed to surgical saws of the sagittal type, but the scope of the invention is not limited only to this type. 
     Referring to  FIG. 11 , an oscillating type surgical saw, according to a sixth apparatus aspect of the invention includes a saw body  212 , an oscillating saw-type cutting head  214 , a first blade  217  and a second blade  218 . The blades  217 ,  218  are coupled, respectively, to first and second blade assemblies  222 ,  224 . A pair of oscillators  226 ,  228  reciprocate the blades  217 ,  218  when activated. In this embodiment the cutting angle A 1  between the blades  217 ,  218  is fixed, but can be adjusted by inserting one or more angled shim blocks  230  between the blades  217 ,  218  and the blade assemblies  224 , 226 . The cutting angle A 1  is then determined from the angle forming the angled shim blocks  230 . This allows the blades  217 , 218  to be adjusted in the direction indicated by the arrows  232 . In an alternate example, the cutting angle A 1  is adjusted by changing the blade width, which may also be done in combination with using one or more shim blocks  230 . 
       FIGS. 12-14  illustrate a first method of use aspect of the invention, in which a dual-bladed surgical saw according to one of the apparatus aspects of the invention is used to perform an Austin bunionectomy on a foot  110 . In this method, the blade angle is set to the desired position and the dual-bladed surgical saw is started. A cut  114  is made in the first metatarsal  112  at the blade angle A 1 . The first metatarsal  112  is then fixed in place using an appropriate fixation device  116  such as a K-wire. The procedure is then concluded in the conventional manner. 
     Referring now to  FIG. 15 , one of the particularly advantageous methods of use of the dual-bladed surgical saws described above is to shape a femur F so that a knee implant I can be installed. Knee implants typically include an implant surface I 1  that is placed in contact with the shaped femur F and affixed thereto. The implant surface I 1  has a very particular shape, including differently angled sections. In order for the knee replacement procedure to be effective, the shape of the femur F should substantially match the shape of the implant surface I 1 . Conventionally, the femur F is shaped using a single bladed surgical saw, which has the drawbacks discussed above. 
     Knee replacement surgery is made more efficient by utilizing a dual-bladed surgical saw because it can make a precisely angled cut in the femur F in one pass. This is illustrated in  FIGS. 16   a - d . In  FIG. 16   a , the blades  17 , 18  are positioned at the desired angle and a first pass is made across the femur F to form a first and second cut  110 ,  112  separated by the blade angle. In  FIG. 16   b , the blades  17 , 18  are repositioned, if necessary, to the desired angle and a second pass is made across the femur F to form a third cut  114  separated from the second cut  112  by the blade angle. Note that in the second pass, the first blade  17  runs back across the second cut  112  to ensure that the third cut  114  is as close as possible to the correct angle. In  FIG. 16   c , the blades  17 , 18  are repositioned, if necessary, to the desired angle and a third pass is made across the femur F to form a fourth cut  116  separated from the third cut  114  by the blade angle. In the third pass, the first blade  17  runs back across the third cut  114  to ensure that the fourth cut  116  is as close as possible to the correct angle. In  FIG. 16   d , the blades  17 , 18  are repositioned, if necessary, to the desired angle and a fourth pass is made across the femur F to form a fifth cut  118  separated from the fourth cut  116  by the blade angle. In the fourth pass, the first blade  17  runs back across the fourth cut  116  to ensure that the fifth cut  118  is as close as possible to the correct angle.  FIG. 17  illustrates how a knee implant I is installed onto the distal femur F once the cuts are made. 
     The blade angle setting for each pass is set according to the shape of the implant surface I 1 . Because different commercially available implants I have differently shaped implant surfaces I 1 , the dual-bladed surgical saw allows for the blade angle to be adjusted to match a variety of different implants I. Before the procedure begins, it might be advantageous to prepare a separate template for each commercially available implant I and use the template to indicate the cut lines on the femur F itself prior to making any cuts. The template may also be used to precisely set the blade angle for each pass. Prior to making the cuts, it may be beneficial to superimpose the template of the bone implant to be attached to the bone onto the bone to be cut. This way, the superimposed template can be used as a guide or jig for the surgeon when making the cuts. 
     An example of this procedure is illustrated in  FIGS. 18   a  and  18   b . In  FIG. 18   a , a template T is formed using the implant surface I 1  as a guide. The template T is then superimposed and temporarily affixed to the femur F in the proper position. The template defines a cutting line (dashed line) on the femur F that substantially matches the shape of the implant surface I 1 . In this case, the template T may be in the form of a plate, jig, or stencil, depending on its thickness, and the cutting line is defined along it peripheral boundary. If a thicker plate is used, it will act as a jig by keeping the dual saw blades bone cuts in the same plane. If desired, In  FIG. 18   b , the template T is in the form of a stencil that defines the cutting line along its interior boundary, which matches the shape of the implant surface I 1 . The surgeon can simply trace the shape of the template T onto the bone prior to cutting. 
     It should be understood that the actual shape of the template may vary from the two examples depicted here, for example, to better accommodate the multiplanar surface of the side of the femur bone in which the template will be used and/or temporarily affixed thereto. 
     It should be understood that the method illustrated in  FIGS. 16   a - d ,  17 , and  18  is for a particular type of knee implant I. Accordingly, it may be necessary to make more or fewer cuts, depending on the implant surface I 1  shape. In any case, however, it will be advantageous to pass the first blade  17  across the previous cut when making a subsequent cut as described. 
     Referring now to  FIG. 19 , the method just described may alternatively be performed with a dual-bladed surgical saw  300  having a fixed cutting angle A 1  between the blades  17 , 18 . In this example, the cutting angle A 1  between blades  17 , 18  is fixed at an angle that corresponds to an angle between cuts needed to match a particular implant to a bone. The surgeon can use a series of dual-bladed saws fixed to the proper cutting angle A 1  if different cutting angles A 1  are necessary. In the dual-bladed sagittal-type surgical saw  300  shown in  FIG. 19 . The blades  17 ,  18  are affixed to a blade mount shaft  302  such that the proper cutting angle A 1  is obtained. In this example, the fixed cutting angle is about 121 degrees, which is, in no way, a limitation to the scope of the invention. 
     Referring to  FIG. 20 , a series of fixed cutting angle oscillator-type dual-bladed surgical saws, such as the saw  400  may also be used to perform the same method. In this example, the saw  400  is essentially the same as the saw  200  shown in  FIG. 11 , but the cutting angle A 1  is about 121 degrees, which is, in no way, a limitation to the scope of the invention. 
     The invention has been described above with reference to preferred embodiments. Unless otherwise defined, all technical and scientific terms used herein are intended to have the same meaning as commonly understood in the art to which this invention pertains and at the time of its filing. Although various methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described. However, the skilled should understand that the methods and materials used and described are examples and may not be the only ones suitable for use in the invention. 
     The invention has been described in some detail, but it will be apparent that various modifications and changes can be made within the spirit and scope of the invention as described in the foregoing specification and the appended claims.