Abstract:
A bone cutter is provided for creating cylindrical bone plugs for patella-patellar tendon-tibia grafts and comprises a support having a pair of bone cutting wheels mounted thereon about a vertical axis. Each of the cutting wheels have an hourglass shape to define a circular opening therebetween. An adjustable plug guide is provided forwardly of the cutting wheels for guiding the harvested bone plug into proper engagement and alignment with the rotating cutting wheels.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a bone cutting device and more particularly to a bone cutting device for creating cylindrical bone plugs for patella-patellar tendon-tibia grafts from bone plugs having other than a cylindrical shape. 
     2. Description of the Related Art 
     It has become standard procedure to use autologous patella-patellar tendon-tibia graft originating from the central one-third of the patellar tendon for anterior cruciate ligament (ACL) repair. The bone plugs of this autograft provide efficient healing with the osseous tunnels. Several studies have shown the cylindrical bone plug configuration to be superior to other geometric configurations. A cylindrical configuration provides a tighter fit in the tunnel and increases pull out strength. 
     As with any surgical procedure, ACL repair faces the concern of operation and anesthesia time. Increased length of operation has been associated with increased bacterial contamination of surgical wound, increased in-hospital mortality, increased post-op observation time, increased risk of hypothermia, short-term decline in Activities of Daily Living, post-op pulmonary complication, increased pain and fatigue, and increased risk for cardiovascular complications. Thus, a decrease in operative time would lead to less complications for the patient. A decrease in operative time would also decrease surgeon fatigue, which would directly increase the concentration of the surgeon towards the procedure. 
     Two methods have been previously demonstrated as ways to create cylindrical bone plugs on patellar tendon grafts. One of these methods involves the use of a circular oscillating saw to procure cylindrical bone plugs directly from the patient&#39;s knee. This technique provides reproducible plugs that are sized and shaped appropriately for the corresponding osseous tunnels. However, this particular saw has been described as cumbersome in the operating room, and there is a risk, although small, of thermal injury to the patient&#39;s skin from the heat produced by the body of the saw. Currently, this saw is not used in many institutions due to those reasons. In at least some institutions, grafts are harvested via a pneumatic saw, oscillating bone saw, or an osteotome and mallet. The harvested square grafts are then fashioned into cylindrical bone plugs with a Ronguer. The use of a Ronguer to shape a cylindrical bone plug from a square plug consumes considerable operative time and the plugs are not a standard, reproducible shape; however, this has become the commonly accepted method of shaping previously harvested patella-patellar tendon-tibia autograft bone plugs. 
     SUMMARY OF THE INVENTION 
     A device is described for creating cylindrical bone plugs for patella tendon-tibia grafts comprising a support having a bone cutting mechanism positioned thereon for grinding bone plugs, having other than a cylindrical shape, to create cylindrical bone plugs. The bone cutting mechanism comprises a pair of horizontally spaced, vertically disposed rotatable cutting wheels or cylinders which are rotated about a vertical axis. Each of the cutting wheels or cylinders have an hourglass configuration to define a substantially cylindrical space therebetween. A guide apparatus is provided on the support for guiding the bone plugs into the rotating cutting wheels or cylinders. The guide means is adjustable to accommodate various sizes of bone plugs. One of the cutting wheels is power driven with the other cutting wheel being driven by the power driven wheel through the use of meshing gears operatively connected to each of the cutting wheels. 
     It is therefore a principal object of the invention to provide an improved device for creating cylindrical bone plugs for patella tendon-tibia grafts. 
     Yet another object of the invention is to provide a device of the type described which provides reproducible shapes. 
     Still another object of the invention is to provide a device of the type described above including an adjustable bone plug guiding means so that the bone plugs are properly guided into contact with the rotating cutting wheels. 
     Yet another object of the invention is to provide a device of the type described above wherein the components thereof may be replaced as necessary. 
     Still another object of the invention is to provide a device of the type described above which is economical of manufacture and convenient to use. 
     These and other objects of the invention will be apparent to those skilled in the art. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the bone cutting device of this invention; 
     FIG. 2A is a perspective view of the bone plugs prior to being ground; 
     FIG. 2B is a perspective view illustrating the bone plugs after they have been cut into a cylindrical shape; 
     FIG. 3 is an exploded perspective view of the bone cutting device of this invention; 
     FIG. 4 is a top elevational view of the device of this invention; 
     FIG. 5 is a view similar to FIG. 4, but which illustrates the bone plug guidance means having been adjusted from that of FIG. 4; 
     FIG. 6 is a front elevational view of the invention; and 
     FIG. 7 is a side elevational view of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The bone cutting device of this invention is referred to generally by the reference numeral  10  and includes a support plate  12 . Although support plate  12  is shown to be a component of the invention, it is possible that the remaining components of the invention could be installed on a table top, counter top, or other suitable support. For purposes of description, support  12  will be described as having a forward end  14 , rearward end  16 , and opposite sides  18  and  20 . 
     An elongated block member  22  is secured to the forward end of support  12  on the upper surface thereof by means of screws  24 . As seen in FIG. 1, the rearward end of block member  22  is provided with a recessed area  26  formed in the lower end thereof. 
     Slide member  28  is slidably positioned at the rearward end of block member  22  and has a lip or flange  30  slidably received in the recessed area  26  of block member  22 . Slide member  28  is also provided with a recessed area  32  formed therein at its lower rearward end. Slide member  28  also has an elongated slot  34  extending downwardly therethrough which adjustably receives the stud  36  secured to support  14  and extending upwardly therefrom. The upper end of the stud  36  is threaded and is adapted to receive the wing nut  38  to maintain slide member  28  in various lateral positions with respect to support  14 . As seen in FIG. 3, slide member  28  includes a rearwardly extending portion  40 . Gear rack  42  having rearwardly presented teeth  44  is positioned in recessed area  32  of slide member  28  and is secured thereto by screws or the like. The teeth  44  are adapted to engage the teeth of a gear wheel  46  which is rotatably mounted on stud  48  which extends upwardly from support plate  14 . 
     The numeral  50  refers to a slide member which is substantially the mirror image of slide member  28  and which has a gear rack  52  positioned in recessed area  54  and which includes forwardly presented teeth  56  which mesh with the teeth of gear wheel  46 . Slide member  50  also has a forwardly extending portion  58 , as seen in FIG.  3 . 
     The slide members  28  and  50  serve as the supports for guide members  60  and  62  which are secured to the slide members  28  and  50  at the inner sides of the rearwardly extending portion  40  and the forwardly extending portion  58 , respectively. As seen in FIG. 3, the rearward ends of the guide members  60  and  62  have tapered portions  64  and  66 , respectively, for a purpose to be described hereinafter. 
     A threaded bolt  68  is threadably secured to slide member  50 , as illustrated in FIG. 3, and a threaded bolt identical to bolt  68  is threadably secured to the outer side of slide member  28 . The threaded bolts serve as grips to enable the slide members  28  and  50  to be moved towards one another and moved away from one another. As seen in FIG. 3, the inner surfaces of the guide members  60  and  62  are provided with tapered guide surfaces  70  and  72 , respectively, adapted to receive and position the bone graft having a shape other than a cylindrical shape. 
     The numeral  74  refers to a cutting wheel support which is secured to the support plate  14  rearwardly of the slide members  28  and  50 , as illustrated in the drawings. Support  74  rotatably supports a pair of cylindrical cutting wheels or cylinders  76  and  78  which are horizontally spaced-apart from one another and which are vertically disposed. Gear wheels  79  and  80  are positioned on the upper ends of the cutting wheels  76  and  78  for rotation therewith and are in mesh with one another. The cutting wheels  76  and  78  are rotatably mounted by means of the shafts  82  and  84 , respectively. Cover  86  is secured to the upper end of the support  74  and has a pair of openings  88  and  90  formed therein which receive the upper ends of the shafts  82  and  84 , respectively. As seen in the drawings, the upper end of the shaft  82  extends upwardly from the cover  86 . Shaft  82  is secured to the gear wheel  79  and the cutting wheel  76  so that rotation of the shaft  82  by the power means  92 , which may be an electric drill, will cause the rotation of gear wheel  79  and cutting wheel  76  which in turn causes the rotation of gear wheel  80  and grinding wheel  78 . As seen in the drawings, the cutting wheels  76  and  78  have an hourglass configuration to define a cylindrical opening  94  therebetween. The cutting wheels  76  and  78  are provided with a plurality of radially spaced-apart cutting blades  96  and  98  thereon. As seen in FIG. 3, the lower ends of the cutting wheels  76  and  78  do not have cutting blades thereon, since those lower end portions are received in the recesses  100  and  102  formed in the support  74 . Plate  104  is secured to the forward end of support  74  and extends thereacross, as seen in the drawings. As seen in the drawings, the lower end of plate  104  has an inverted V-shaped opening  106  formed therein which limits the upward movement of the bone as it is passing through the cutting wheels. 
     FIG.  1  and FIG. 2A illustrate the harvested bone plug which is referred to generally by the reference numeral  108 . As seen in the drawings, the harvested bone plug  108  has square or triangular shaped bones  110  and  112  at the opposite ends thereof. An exit support structure  114  is provided rearwardly of the grinding cylinders to maintain the bone plug in a horizontal position. 
     In use, the wing nut  38  is first loosened so that the slide members  28  and  50  may be moved either outwardly or inwardly to provide the proper spacing between the inclined surfaces  70  and  72  of the guide members  60  and  62 , respectively. The movement of the slide members  28  and  50 , with respect to one another, is coordinated by the interaction of the gear wheel  46  in engagement with the gear racks  42  and  52  to ensure that the slide members  28  and  50  will be moved inwardly and outwardly the same amount. 
     Once the guide members  60  and  62  have been properly positioned, the wing nut  38  is tightened to prevent further movement of the slide members  28  and  50 . The power means is then attached to the upper end of the shaft  82  and energized so that the gear wheels  76  and  78  are rotated. Cutting wheel  76  is rotated in a clockwise fashion, as viewed in FIG. 3, and cutting wheel  78  is rotated in a counterclockwise direction, as viewed in FIG.  3 . End  110  of the harvested bone plug  108  is then positioned between the inclined surfaces  70  and  72  of the guide members  60  and  62 , respectively, and is fed rearwardly into engagement with the rotating cutting wheels  76  and  78 . The cutting wheels cut the bone on the harvested bone plug to create a cylindrical shape thereto. Once the end  110  has been cylindrically shaped, the bone plug  108  may be withdrawn from the device and the end  112  inserted thereinto. 
     Thus it can be seen that a novel device has been provided for creating cylindrical bone plugs for patella tendon-tibia grafts which accomplishes at least all of its stated objectives.