Abstract:
A device is presented for temporarily mounting an image tracker to a patient during surgery. The device preferably includes a first aperture and a axially-align second aperture. The apertures are sized to receive a securing mechanism, such as a bone screw that is temporarily inserted into a patient&#39;s bone for holding the image tracker near the vicinity of a surgical site. The device further preferably includes at least one projection such as a pin to stabilize the device from rotating.

Description:
FIELD OF THE INVENTION 
   The present invention is a device and method of use for an apparatus used to mount an image tracker to a patient. 
   BACKGROUND AND SUMMARY OF THE INVENTION 
   Due to the frequently limited amount of exposure of the spine or interior surgical area, spinal implant procedures lend themselves to use of image guidance for surgery. Examples of such image guidance systems include the BrainLAB. System and the Stealth System. The image guidance systems use data from standard CT or MRI scans to build a three dimensional image of the patient&#39;s spine. This model is then electronically matched to the patient&#39;s anatomy during surgery, allowing the surgeon, in effect, to see through tissue in order to accurately determine the placement of instruments or devices. During the operation, sensitive structures such as blood vessels and nerves, which the surgeon wants to avoid on the way to the anatomical target, can be visualized. In addition, during the operation the surgeon can follow the movements of his or her instruments on the computer screen in real time. 
   As understood by those skilled in the art, these image guidance systems utilize a computer system with a monitor and two cameras that emit infrared signals, thereby determining the patient&#39;s position in the operating room as well as the position of the surgical instruments in relation to the patient&#39;s spine. The infrared signals are continuously monitored during surgery using an image tracker receiver that is located in the vicinity of the surgical site. 
   The present invention comprises a mounting base for mounting an image tracker into a bone of a patient. The mounting base includes a securing mechanism, such as a bone screw, that is inserted through the base and then into the bone. The mounting base also includes at least one projection to further stabilize the mounting base and assist in preventing rotation of the mounting base after attaching the mounting base to the patient. The image tracker array is interconnected to the secured mounting base, thereby providing a secure mounting apparatus that can be used in the immediate vicinity of the patient&#39;s surgical site. Thus, in one aspect of the present invention, a device for stabilizing an image tracker in a patient&#39;s bone is provided, where the device comprises a securing mechanism and a body, where the body has a first aperture and a second aperture both sized to receive the securing mechanism. In use, the securing mechanism is inserted through the first aperture and the second aperture and inserted into the patient&#39;s bone for temporarily stabilizing the image tracker to a patient. 
   A projection is also preferably used to prevent the device from rotating after inserting the securing mechanism into the patient&#39;s bone. Thus, it is a separate aspect of the present invention to provide a mounting base for stabilizing an image tracker in a patient&#39;s bone, wherein the device comprises a body having an entrance aperture and an exit aperture and a passageway therebetween. In addition, the device includes means for securing the base to the patient&#39;s bone, and wherein the means for securing is sized to be received in the passageway. The device further includes a means for stabilizing the body from rotating. In use, the means for securing is inserted through the entrance aperture, the passageway, and the exit aperture and inserted into the patient&#39;s bone for temporarily stabilizing the image tracker to a patient. 
   A method of using the device is also provided. Thus, it is a separate aspect of the present invention to provide a method of attaching an image tracker to a patient, wherein the method comprises a) inserting a bone screw through a body of a mounting base, the body having an entrance aperture, an exit aperture, and at least one stabilizing projection; b) advancing the bone screw into a bone of the patient; and c) tightening the bone screw into the bone. 
   Further and more specific advantages and features of the invention will become apparent to those skilled in the art from the following detailed description, taken in conjunction with the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a first embodiment of the present invention wherein the securing mechanism passes through a side and bottom surface of the body of the mounting base; 
       FIG. 2  is a second perspective view of the device shown in  FIG. 1 ; 
       FIG. 3  is a third perspective view of the device shown in  FIG. 1 ; 
       FIG. 4  is a fourth perspective view of the device shown in  FIG. 1 ; 
       FIG. 5  is a side elevation view of a modification of the first embodiment wherein the mounting base includes a projection mounted on a side of the body of the mounting base; 
       FIG. 6  is a side elevation view of another modification of the first embodiment wherein the mounting base includes a plurality of projections and a securing mechanism that passes through the sides of the body of the mounting base; 
       FIG. 7  is a side elevation view of another modification of the first embodiment wherein the mounting base includes a retractable and detachable projection, and a securing mechanism that passes through the top and bottom surfaces of the mounting base; 
       FIGS. 8   a  and  8   b  are side elevation views of modifications of the first embodiment wherein the mounting base includes a securing mechanism that passes through the top and through a side of the body of the mounting base; 
       FIG. 9  is an exploded side elevation view of another modification of the first embodiment wherein the mounting base includes an inner flange and a side mounted connector for the tracker array; 
       FIG. 10  is a plan view of the top of the device shown in  FIG. 9 ; 
       FIG. 11  is an elevation view looking at the bottom of the device shown in  FIG. 9 ; 
       FIG. 12  is a cross-sectional view of the device shown in  FIG. 9  taken along line  12 - 12 ; 
       FIGS. 13   a - f  are elevation views of the bottom surfaces of different shaped and differently configured mounting bases. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 1-4 , a first embodiment of the mounting base  10  comprising the present invention is shown. The mounting base  10  includes a body  12  having a first or entrance aperture  14  for receiving a securing mechanism  16 . Mounting base  10  further includes a second or exit aperture  18  axially aligned with the entrance aperture  14  also for receiving securing mechanism  16 . A securing mechanism passageway  20  extends through body  12  between entrance aperture  14  and exit aperture  18  for allowing securing mechanism  16  to be extended through body  12  of base  10 . 
   Preferably, securing mechanism  16  is a 4 to 8 mm diameter bone screw having a plurality of threads  22  along at least the lower portion of its exterior. When a bone screw is used as securing mechanism  16 , it serves to anchor the base  10  to a bone, such as the iliac crest of the pelvis. The threads  22  of securing mechanism  16  allow securing mechanism  16  to be inserted into a bone and rotated until a relatively tight insertion is achieved. 
   Mounting base  10  preferably includes at least one projection  24  to provide stability to base  10  during use. Projection  24  preferably takes the form of a small rod, a point, a pin, or other structure that serves to prevent rotational movement of base  10  while base  10  is anchored to an object, such as a patient&#39;s hip bone. To prevent rotational movement, projection  24  is preferably laterally offset from securing mechanism  16  and/or exit aperture  18 , thereby providing rotational stability to base  10  upon tightening securing mechanism  16  into bone. As shown in  FIGS. 1-4 , the projection  24  is preferably located on the bottom surface  26  of base  10 . However, as shown in  FIG. 5 , projection  24  could be located to a side  28  of the body  12  of base  10  where it extends generally in the direction of the bottom surface  26  of base  10 . In this arrangement, the length of projection  24  preferably is such that it extends beyond the bottom surface  26  of base  10  if mounted into a relatively flat bone, or otherwise extends a sufficient distance to intercept a bodily structure that rotationally stabilizes the base  10 . 
   Referring now to  FIG. 6 , a plurality of projections  24  may be used. Furthermore, projection  24  may be of various lengths as also shown  FIG. 6 . The projection  24  can be permanently fixed to body  12  of base  10 . Alternatively, as shown in  FIG. 7 , projection  24  may be detachable and adjustable. For example,  FIG. 7  illustrates a mounting base  10  where the securing mechanism  16  is located offset from the longitudinal center axis A-A of the body  12 , and where a projection  24  in the form of a small rod or pin that extends through the: body  12  is illustrated. Here, the projection  24  can be inserted separately from the securing mechanism  16  and the projection  24  can be optionally secured with a set screw  30 , and then removed upon completion of using the mounting base  10 . Thus, the projection  24  can be retractable within and/or removeable from the body  12 . 
   Still referring to  FIG. 7 , in a separate aspect of the invention, a set screw  30  may also be used for temporarily securing the securing mechanism  16  in the body  12  of mounting base  10 . More particularly, for all embodiments and their modifications described herein, the securing mechanism  16  may be optionally secured within the body  12  using a set screw  30 . 
   In a separate aspect of the invention, entrance aperture  14  and exit aperture  18  can be positioned along different surfaces of base  10 . More particularly, for the mounting base  10  shown in  FIGS. 1-5 , the first or entrance aperture  14  is situated along a side face  28  of the body  12  of base  10 , and the second or exit aperture  18  is located along the bottom surface  26  of the base  10 . Alternatively, as shown in  FIG. 6 , the entrance aperture  14  may be located along a lateral side  28 , and the exit aperture  18  may also be located on a lateral side  28 . In yet another alternative arrangement, as shown in  FIG. 7 , the entrance aperture  14  may be located along the top surface  32  of base  10 , while the exit aperture  18  is located along the bottom surface  26 . In yet another alternative arrangement, as shown in  FIGS. 8   a  and  8   b,  the entrance aperture  14  may be located along the top surface  32 , while the exit aperture  18  is located along a lateral side  28  of body  12 . Thus, during manufacture of base  10 , the orientation if passageway  20  can be modified to provide different orientations for the securing mechanism  16  relative to body  12 , thereby allowing bases  10  to be used for different body locations and different body positions that may be desirable during a given surgical procedure. 
   Mounting base  10  preferably includes a mechanism for receiving image tracker array T. One preferred arrangement for such a mechanism is a support structure  34  for receiving the image tracker array T. Support structure  34  preferably includes a permanently mounted post  36  that may be used to detachably attach an image tracker array. T using an interconnecting rod  38 . As shown in  FIGS. 1-4 , the interconnecting rod  38  is preferably secured to post  36  using tightening screw  40 . Post  36  can be attached to the top surface  32  of body  12  of mounting base  10 , or the support structure  34 , including post  36 , can be on the side  28  of body  12  of mounting base  10 , as shown in  FIG. 9 . 
   Referring now to  FIGS. 9-12 , yet a alternative modification to the first embodiment of the present invention is shown, wherein mounting base  10  includes a body  12  having a passageway  20  that receives the securing mechanism  16  including its head portion  42 , and wherein the head portion  42  of securing mechanism  16  can extend into the passageway until contacting an inner flange or protrusion  44  within the passageway  20 . Thus, protrusion  44  provides mechanism for limiting the depth with which securing mechanism  16  can be driven into the patient&#39;s bone. More particularly, if a bone screw is used as the securing mechanism  16 , then the bone screw can only be driven until the head portion  42  contacts the protrusion  44 . Thus, this feature acts as a safety device for limiting the penetration depth of the securing mechanism  16 . It is to be understood that the location of the protrusion  44  in the passageway  20  maybe positioned closer to the bottom surface  26  of body  12  than the upper surface  32  of body  12 , as shown in  FIG. 10 , or the position of the protrusion  44  may located equidistant between the bottom surface  26  and upper surface  32 , or closer to the upper surface  32  than the bottom surface  26 . However, it is preferable to maintain a length of the securing mechanism  16  within the body  12  to effectively maintain alignment of the body  12 , with the shaft of securing mechanism  16 . 
   Referring now to  FIGS. 13   a - 13   f , the bottom surface of different possible shapes of mounting bases  10  are depicted, together with a number of different arrangements for the location of the exit aperture  18  and projection(s)  24 . More specifically,  FIG. 13   a  depicts a mounting base having a circular shaped bottom surface, with a centrally located exit aperture  18  and a single projection  24  located near the outer edge of the bottom surface  26 .  FIG. 13   b  depicts an oval shaped mounting base  10 , and  FIG. 13   c  depicts a rectangular shaped mounting base  10 , where both of the bottom surfaces  26  include a single projection  24 .  FIG. 13   d  depicts a triangular shaped bottom surface  26  with three projections  24 , and wherein the exit aperture  18  is situated substantially in the center of the bottom surface  26  with the projections  24  evenly distributed near the corners of the bottom surface  26 .  FIG. 13   e  illustrates a square shaped bottom surface  26 , and  FIG. 13   f  depicts a hexagonally shaped bottom surface  26 , both having a plurality of projections  24 . Thus, a variety of cross sections and configurations are available for the mounting base  10 . 
   In a separate aspect of the invention, a mounting base  10  may have a plurality of securing mechanisms  16  (not shown) that are used to penetrate the bone and anchor the mounting base. 
   In use, a surgeon decides upon a point for locating the base  10 , and thus, the image tracker array T. Image tracker array T is typically located at a position situated near the surgical incision point on the patient, but spaced apart a sufficient distance such that the base  10  is not too close to the incision point so as to interfere with the surgeon&#39;s access and motion during surgery. The position for the image tracker base  10  is then properly prepared, which may typically include sterilization of the point of placement. A securing mechanism  16 , such as a bone screw, is then threaded through both the first or entrance aperture  14  and second or exit aperture  18  of the body  12 . Subsequently, while the securing mechanism  16  is still threaded through body  12 , the securing mechanism  16  is then inserted into the patient&#39;s bone. The securing mechanism  16  preferably includes a tool slot  46  or receptacle along its top surface for receiving a tool, such as a surgical screwdriver. The securing mechanism  16  is tightened into the bone so as to provide a relatively tight fit with the bone within which it is inserted. During the installation of the securing mechanism  16 , if projection  24  is permanently affixed to the mounting base  10 , the projection  24  seats into the patient&#39;s bone or tissue to prevent rotation of the mounting base  10  and assist in stabilizing the mounting base  10 . Alternatively, if the projection  24  is detachably or retractably attached to the mounting base  10 , then an additional step of advancing the projection  24  is performed to seat the projection into the patient&#39;s bone or tissue to prevent rotation of the mounting base. 
   All components of the invention described herein are manufactured of a material appropriate for surgical use. For example, the components can be made of stainless steel. However, it is to be understood that other types of materials may also be used, such as titanium or ceramics. 
   While various embodiments of the present invention have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present invention.