Abstract:
The present invention relates to a system and method to aid the placement of surgical devices under radiographic image guidance. More particularly, embodiments of the invention relate to a system utilizing radiopaque markers, an external light source projected onto the skin or surgical site in conjunction with a target guide holder. Using a radiographic image to identify landmarks for skin entry and bone entry points to facilitate the accurate placement of surgical devices. An exemplary system utilizes a radiopaque marker, target guide holder and external laser markers to determine intra-operative angles, trajectories and positioning coordinates to facilitate placement of needles, guide wires, surgical hardware, trocars and cannulae for the surgical placement of orthopedic implantation devices.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Provisional Application Ser. No. 61/954,250, filed on Mar. 17, 2014. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Field of the Invention 
         [0003]    The present invention relates to a system and method to aid the placement of surgical devices under radiographic image guidance. More particularly, embodiments of the invention relate to a system utilizing radiopaque markers, an external light source and targets. Light is projected onto the skin or surgical site over a target in conjunction with a radiographic line marker superimposed on a fluoroscopic image to identify bone landmarks and angles so that skin entry points can be identified. This can be augmented by the use of a target system that is held in place by a bedside rail mounted mechanical arm that can hold any position desired. This allows rigid guidance of guide wire to facilitate the accurate placement of surgical implant or devices. An exemplary system utilizes a radiopaque marker, external laser markers and a target to determine intra-operative angles, trajectories and positioning coordinates to facilitate placement of needles, guide wires, trocars and cannulae for the surgical placement of orthopedic implantation devices. 
         [0004]    Description of the Related Art 
         [0005]    Many fluoroscopy systems on the market possess a laser “aimer” or pointer that is used in conjunction with the imaging source. One example is the Smart Laser Aimer from GE OEC (GE Healthcare, Salt Lake City, Utah). The laser pointer is mounted on the Image Intensifier of the C-arm and is used as a line of sight pointer. The laser light illuminates the center point on the surgical site where the x-ray beam will image if activated, giving the user a more accurate location of the image. It does not accurately place the image in global 3-dimensional space, nor does it provide an accurate location with respect to anatomical landmarks. The user must rely on more complex image guidance systems intra-operatively, or 3-D image reconstruction software pre-operatively in order to obtain more accurate information for precise instrument placement. One example of intra-operative guidance systems is the Stealth Station from Medtronic. Such systems require a dedicated piece of equipment to transmit and receive signals and markers on the surgical instruments to track the position and orientation of each instrument. Dedicated software and image storage are also required to incorporate guidance system information into preoperative or intraoperative images. Such systems do not have the benefit of the present invention of being compatible with any commercially available imaging equipment and surgical instruments. 
         [0006]    There are many targeting or aiming apparatus for making bores in bones in register with bores has been disclosed in the targeting system previously disclosed in U.S. Pat. No. 5,031,2013 that utilized a laser and a fixed target in combination with x-rays. More recently, there have been articles focusing on targeting with a complex computer aided such as, “Percutaneous Lumbar Pedicle Screw Placement Aided by Computer-Assisted Fluoroscopy-based Navigation” by Benson P. Yang, MD, Melvin Wahl, MD, CARY S. Idler MD, Spine:37(24):2055-2060. There has also been other publications such as, “Accuracy of Fluoroscopically assisted laser targeting of the cadaveric thoracic and lumbar spine to place transpedicular screws” by Schwend, R M, Dewire P J, Kowalski T M; J Spinal Disord. 2000 October; 13 (5): 412-8; “Pedicle Guide for Thoracic Pedicle Screw Placement” by Kingsley O. Abode-Iyamah MD; Luke Stemper BS; Shane Rachman BS; Kelly Schneider BS; Kathryn Sick BS Patrick W. Hilton MD, University of Iowa Hospitals and Clinics; and the work of C. Grady McBride at the Orlando Orthopaedic Center, where reduction of fluoroscope times resulted in the use of a targeting device in parallel for insertion of a guide wire. In none of these pieces of prior art are there the safety, ease of use, and the efficiency of the instant invention. 
         [0007]    The fluoroscopy systems operate on either a continuous or pulsing system for x-rays to permit continuous or near continuous monitoring of the medical procedure involved. In either situation there is still a need to reduce or limit the exposure of patients to the exposure of the x-ray radiation. Timing is critical, but in the surgeries utilizing today&#39;s fluoroscopy systems there is somewhat a hit and miss approach to finding the landmarks need for the attachment of screws for spinal surgery, as the procedure follows a general methodology of measurement and a grid pattern that often does not consider the thickness of a patient&#39;s soft tissue and muscle from the area of attachment such as the pedicles of the spine. The use of Jamshidi needles, trocars and cannulae for certain surgeries help limit wound size and openings, but the degree of precision desired is still not met using the current methods, even with complex software and robotics. The degree of precision has greatly improved, but the accuracy of the puncture for attaching screws in the body still relies on an estimate of the location of the incision without an exemplar or marker to follow or a more accurate place in which to make the incision. For example, in spine surgery the standardized methodology will be to measure from the midline to a fixed distance to make an incision with limited regard to the angle of entry and if the landmark is not hit on the first attempt there are continued attempts and the need for dealing with tissue and muscle as the trocar or cannula is being positioned to find the pedicle landmark. This increases unnecessary exposure to x-rays and the increased chance of injury to tissue and muscle. 
         [0008]    Also, the focus is minimally invasive surgery is to limit the need for opening the body and increase the risk of infection and healing. In the use of robotics, for instance, section of the spine still need to be exposed to attach the rail for the robotic system to be used during spine surgery. While this may be an improvement over opening the entire area of the spine, it still creates issues around infection and healing of the wounds. While the methodologies used to get towards minimally invasive surgery have improved there is significant opportunity for an increase in accuracy to go along with the increase in precision. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention is a system and method used in conjunction with fluoroscopic imaging systems to identify bone landmarks and angles, skin entry points and trajectories and a target guide holder in order to aid the placement of surgical instruments, such as guide pins, needles, trocars, fixation hardware and cannulae. The system&#39;s utility is not limited to a particular anatomical location, and thus can be used in a wide range of variety of surgical applications. In addition to the spine surgery application detailed below, it can be used in human, veterinary, or training models for cranial, hip, knee, and wrist surgery, for example. 
         [0010]    The system comprises of an adjustable radiopaque bar marker mounted below external light sources, such as visible light sources or lasers, the associated mounting hardware on the imaging system and a separate targeting guide holder. The mounting hardware allows the radiopaque marker to translate around and across the circumference and face 360° around the image intensifier. Limiting the radiopaque bar/visible light marker to pivot on its axis to −+5° insures projected lines under fluoroscopy stay within the limits of beam divergence parameters for accuracy of visible light on patients skin. The system is used in conjunction with commonly available pre-operative images and commercially available intra-operative radiography equipment. A pre-operative image of the intended surgical site is taken using computed tomography (CT) or magnetic resonance Imaging (MRI). On this image, the anatomy of the intended surgical site is seen and used to pre-operatively plan the angles, trajectories and positioning of the surgical instruments by superimposing points and lines on the pre-operative image. From this pre-operative plan, the intended entry point on the skin and angulation of each instrument is planned. Once skin entry point is established the Target guide holder is placed in the surgical field. Using a 2-axis inclometer the AP angle can be applied in the x plane. While in the lateral plane, the target guide holder is aligned with the light line and the y angle can be read off the inclometer. The pre-operative planning step may be performed manually on a printed image or electronically using commercially available software and a digital image. Additional lines are constructed on the pre-operative image by projecting the position of the intended entry points on the skin in the orthogonal planes to be used for intra-operative imaging at the time of surgery. The intersection of the orthogonal projection lines with anatomical landmarks indicates which anatomical landmark to use in intra-operative imaging to align the system. Intra-operative planning may also be performed in the same manner using intra-operative images. 
         [0011]    Intra-operatively, the light source is mounted to a commercially available radiographic imaging system, such as a fluoroscope or portable x-ray. The light beams are projected as a line onto the skin at the surgical site. The radiopaque bar markers and light sources are located in known positions with respect to the imaging system. The radiopaque bar markers are imaged with the anatomical location of interest, and the light sources are projected onto the skin in the plane of the intended entry point determined in pre- or intra-operative planning. The intersection of two linear light beams in orthogonal planes, typically but not necessarily the anterior/posterior (AP) and medial/lateral (ML) planes, clearly mark the entry point of the surgical instruments on the skin of the patient. The orientation of the surgical instruments at the entry point is set using the target guide holder, an angularly adjustable, bi-planar, mechanical guide to set the angle of the instruments in both orthogonal planes per the pre- or intra-operative plan. In some instances a phenomenon known as beam divergence becomes a factor as the area of interest moves away from the center of the image. The nature of the design in the adjustable bar marker allows for visual conformation on the intra-operative radiograph that the bar is in alignment with the divergence. Therefore the light beam on the skin is in true alignment. The system thereby provides accurate both the positioning coordinates and the orientation of the surgical instrument to the surgeon, such that if the resulting trajectory is followed, the instrument will reach the intended internal surgical site without direct visualization by dissection or repeated radiographic exposures. 
         [0012]    An example of the method using the present invention and a pre-operative plan includes an axial pre-operative image, also known as a “slice”, of the intended surgical site is taken using computed tomography (CT) or magnetic resonance imaging (MRI). On this image, the anatomy of the intended surgical site is seen in cross-sectional axial view (a view not commonly available intra-operatively) and used to pre-operatively plan the angles, trajectories and landmark positioning of the surgical instruments. From this pre-operative plan, the intended skin entry point is defined for the AP plane. An example of the method using the present invention and an intra-operative plan includes a lateral intra-operative image using fluoroscopy or portable x-ray. On this image, the anatomy of the intended surgical site is seen in side elevation and used to plan the angles, trajectories and positioning of the surgical instruments. From this intra-operative plan, the intended skin entry and bone entry point is defined in the ML plane. When the two exemplary methods are used together, for example in spinal surgery, the intersection of the AP and ML planes using the light beam mark the surgical skin entry point. The use of the target guide holder insures no human initiated deviation from plotted trajectory is introduced during insertion. This method and device are ideal for minimally invasive procedures including but not limited to discectomy, pedicle screw placement for fixation, facet fusion, facet joint injection, nerve ablation, vertebroplasty. 
         [0013]    Another example of the method is for training surgeons in using the invention for improved performance and accuracy. The intersection of the AP and ML Planes using the light beam mark the surgical skin entry point and the surgeon get use to understanding the various degrees of entry required, such that in the case of the back surgery of the previous paragraph, the angles become familiar to the surgeon through training and they become more accurate in the surgical entry point and the angles of that entry point. Clearly, the invention is applicable for use with not only spinal surgery but also orthopedic surgeries involving shoulder, hips, joints, wrist, arms, legs, ankles hands and feet. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    In order to better understand the invention and to see how it may be carried out in practice, some preferred embodiments are next described, by way of non-limiting examples only, with reference to the accompanying drawings, in which like reference characters denote corresponding features consistently throughout similar embodiments in the attached drawings. 
           [0015]      FIG. 1  is a translucent illustration of the lateral and posterior views of the surgical patient, with the linear light beam externally positioned in the posterior view and the intended trajectory of a surgical instrument through the body in the lateral view. 
           [0016]      FIG. 2  is an example of the instrument trajectory of  FIG. 1A  as projected on a radiographic image. 
           [0017]      FIG. 3  is an illustration of the determination of the surgical angle and projection of the entry point of the skin on an anatomical landmark on a pre-operative CT image. 
           [0018]      FIG. 4  is an illustration of completing the A/P positioning technique by locating the anatomical landmark. 
           [0019]      FIG. 5  is radiograph example of the technique of  FIG. 5 . 
           [0020]      FIG. 6  is an illustration of the guide pin insertion. 
           [0021]      FIG. 7  is radiograph example of the technique of  FIG. 7   
           [0022]      FIG. 8  is an illustration of final positioning of the guide pin. 
           [0023]      FIG. 9  is an illustration of the lateral and posterior views of the cranium, externally positioned in the posterior view and the intended trajectory of a surgical instrument through the skull in the lateral view. Straight vertical and horizontal lines illustrate radiopaque markers and contoured lines illustrate skin incision trajectories. 
           [0024]      FIG. 10  is an illustration of a Fluoroscopic system in a side view. 
           [0025]      FIG. 11  A is a perspective view of a Fluoroscopic C-Arm System. 
           [0026]      FIG. 11  B is a side view of a GE Fluoroscopic C-Arm System. 
           [0027]      FIG. 12  is a perspective view of the collar for the image intensifier with the light source and the radiopaque marker. 
           [0028]      FIG. 13  is a perspective view of the light source and radiopaque marker and how the light source and holder have movement laterally. 
           [0029]      FIG. 14  is a side view of the collar for the image intensifier with the light source and radiopaque marker. 
           [0030]      FIG. 15  is a front view of the collar for the image intensifier with the light source and radiopaque marker. 
           [0031]      FIG. 16  is a top view of the collar for the image intensifier with the light source and radiopaque marker. 
           [0032]      FIG. 17  shows perspective views of an alternative the collar for the image intensifier where the face rotates around the image intensifier. 
           [0033]      FIG. 18  is illustrative of the pre-surgical preparation. 
           [0034]      FIG. 19  illustrates the view from the monitor of the fluoroscope of the of the radiopaque marker. 
           [0035]      FIG. 20  illustrates an alternative collar for the image intensifier. 
           [0036]      FIG. 21  A Illustrates a Jamshidi, a stylet and a target guide holder. 
           [0037]      FIG. 21  B illustrates an inclometer for determine the AP angle and the lateral angle. 
           [0038]      FIG. 22  illustrates a hand and wrist having a plate with screws. 
           [0039]      FIG. 23  illustrates a Humeral Shaft with a plate and screws. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0040]    First, the light source  1  in  FIG. 1A  must be positioned. A collar system  2  will fit the image intensifier  10  incorporating the light source  1  and the radiopaque marker  25 . As shown in  FIG. 1A  and  FIG. 1B , using the radiopaque marker  25  on the face of the laterally positioned image intensifier  10  fluoroscopically the light source trajectory  20  is determined through the spine segment. By superimposing the marker over the anatomy, the system automatically places the laser marker over the skin as shown at  30 . This determines both the angle and latitude position on the skin to start the procedure. 
         [0041]    Next, the A/P position must be determined by looking at the preoperative axial view of the target in question. In  FIG. 2 , the target in question is a vertebral body  35 . The midline  38  is determined, an azimuth through the pedicle or structures desired is positioned, and an angle is determined that would effectively produce the correct trajectory  40  through the anatomy. For example,  FIG. 3  illustrates an angle of 15 degrees at the feature of interest, the end of transverse process. The A/P landmark is determined by using the axial view ( FIG. 4 ) by looking down through the anatomy from the point in which the azimuth exits the body posteriorly  40 .  FIG. 4  illustrates the example of the trajectory overlying the end of the transverse process  50 . The intersection of  50  and  40  is shown at  51 . Finally, using the radiopaque marker on the face of the A/P intensifier, the marker is fluoroscopically superimposed over the landmark previously identified. In the example shown in  FIG. 4 ,  FIG. 5 , and  FIG. 6  this is the end of the transverse process. 
         [0042]    The inclometer guide pin  90  can now be deployed. Using both laser beam  60  and laser beam  70  as reference lines on the skin, the skin port or entry point  80  is established as illustrated in  FIG. 7 . Next, the inclometer guide pin is positioned into the target holder and with the aid of the positioning arm positioned at pre-established angle in AP and target guide holder ML centerline brought into alignment with lateral laser light beam. In the example of  FIG. 8 , the angles are shown as 30 degrees lateral, 15 degrees A/P. Then the inclometer guide pin is replaced with the procedural guide pin then advanced to its fully inserted position as shown in  FIG. 8 . Once the guide pin is successfully inserted, the procedure can begin. 
         [0043]      FIG. 9  is an illustration of the lateral and posterior views of the cranium, externally positioned in the posterior view and the intended trajectory of a surgical instrument through the skull in the lateral view. Straight vertical  95  and horizontal 96 lines illustrate radiopaque markers and contoured lines  97  and  98  illustrate skin incision trajectories. 
         [0044]      FIG. 10  shows a representation of the side of view of a fluoroscope system  100  having an image intensifier  101 , a CCD camera  102 , a monitor  103 , a C-Arm  104 , a collimator  105  and an X-ray tube  106 . The fluoroscope system  100  is known as a C-Arm system. The directed x-ray radiation generated by the X-ray tube  106  passes through the body part at position between the collimator  105  and the image intensifier  101  that is transmitted via the CCD camera  102  to the monitor  103 . The X-rays are either continuous or pulsing so that the surgeon can view the surgery via the monitor  103  in real time. 
         [0045]      FIG. 11  A is a more detailed prospective view of a self-contained C-Arm Fluoroscopic system  200 . The system  200  having an image intensifier  201 , a grid  201 , optics  203 , a CCD camera  2014 , monitors  205 A and  205 B, collimators  206 , filters  207 , X-ray tube  208 , a generator  209  and automatic brightness control  210 . The collar system  2  of  FIG. 1  would fit around the circumference of the image intensifier  201  at  221  or around the Collimators  206  at  221 .  FIG. 11  B is a side view of a version  250  of the Smart Laser Aimer from GE OEC (GE Healthcare, Salt Lake City, Utah) noted earlier is one of the systems to be use with the invention where is shows the position of the collar system  2  in  FIG. 1  can be placed at positions  251  and  252 , depending on the position of the physician and the need entry point for surgery. 
         [0046]    The collar system  2  discussed in  FIG. 1  would fit around the circumference image intensifier  101  in  FIG. 10  or the Collimator  110 .  FIG. 12  shows in a perspective cut away the collar system  300  with light source  301 , which in this instance is a laser light source, a radiopaque marker  302  that is held in housing  303  and secured in the housing by fitting  305 . The housing  303  is part of an assembly  320 , shown more clearly in  FIG. 13 .  FIG. 13  illustrates that the housing  303  has pivoting movement  304  in an arc of no more than plus or minus 5 degrees. Limiting the radiopaque bar/visible light marker to pivot on its axis to −+5° insures projected lines under fluoroscopy stay within the limits of beam divergence parameters for accuracy of visible light on patients skin. The radiopaque markers are always facing the center of the collar to minimize beam divergence. The entire assembly  320  fits into the circumferential channel  310  in  FIG. 12 . The entire assembly rotates around the circumference of the image intensifier of  FIGS. 10 and 11  in the channel  310 . The assembly has three wheels  333  and  334  in  FIGS. 13 and 335  in  FIG. 12  that permit circumferential movement around channel  310 . When the proper location is found by viewing the radiopaque marker  302  as it appears on monitor  103  in  FIG. 10  or Monitor  205  A. 
         [0047]    The assembly  320  has a locking lever  321  that locks the assembly  320  in the desired circumferential position in channel  310  around the circumference of the image intensifier  101  in  FIG. 10 . The collar system  300  also fits around the circumference of the grid  202  and the assembly  320  would move around the circumference of the image intensifier  201  and the grid  201 . 
         [0048]      FIG. 14  a partial side view of the collar system with assembly  320  in channel  310  with the assembly having light source  310  and radiopaque  302  held in housing  303 .  FIG. 15  shows a partial front view of the collar system  300  showing channel  310 , lock lever  321 , housing  303  light source  301 , and radiopaque marker  302 .  FIG. 16  shows a partial top view of collar system  300  and the assembly  320  with housing  303 , fitting  305  and locking lever  321 . 
         [0049]      FIG. 17  illustrates a perspective view of collar system  400  having collar  401  that fits around the circumference of the image intensifier  101  or the Collimator  110  in  FIG. 10  and around the circumference  202  at  220  or the Collimators  206  at  221  of  FIG. 11 . There is outer rim  402  where the assemblies  440 ,  450 , and  460  rotate circumferentially around the grid  202  or the image intensifier  101  or the Collimator  110 . There are also assemblies  450 ,  460 , and  470  that have radiopaque markers  405 ,  406 , and  407 , as well as lights sources  411 ,  412 , and  413 , which illustrates that there can be alternative collar systems with multiple light sources and multiple radiopaque markers. Limiting the radiopaque bar/visible light marker to pivot on its axis to −+5° insures projected lines under fluoroscopy stay within the limits of beam divergence parameters for accuracy of visible light on patients skin. Also, the radiopaque markers are always facing the center of the collar to minimize beam divergence. With the introduction of square faces for the image intensifier or the collimator, the collar here can be easily constructed so that it was square to match up and have a circular channel and face to permitted the assemblies including the radiopaque markers and the light sources to travel around the circumference as shown. Further, with two assemblies on the collar system, the light sources can be arranged to create a target “x” by the intersection of the two light sources to create an entry point for medical instruments. Also, the two radiopaque marker may also be positioned to also permit a target “x” on that can be followed by the surgeon. 
         [0050]      FIG. 18  illustrates the use of pre-surgical preparation where starting with a CT or MRI axial slice of the effected area, you can plot your angles such as the 15 degree angle  501  and identify landmarks such as  502  and  503  and where the skin port  504  for entry of the guide pin that will mimic the radiopaque position  505 . This will normally be accomplished pre-operatively, but can also be accomplished intra-operatively as needed. 
         [0051]      FIG. 19  shows a lateral image  600  having a radiopaque marker  601 . The added accuracy is to have the guide pin insertion (not shown) to mimic or be position the same as the radiopaque marker  601  to provide a more accurate and quicker insertion by also using the AP angle or azimuth angle of 15 degrees. The radiopaque marker provides the surgeon with an insertion to replicate here for use in spine surgery or in any other type of surgery where precision and accuracy are required and the desire is to accomplish the same as minimally invasive. 
         [0052]      FIG. 20  illustrates another version of a collar system for the fluoroscopic system  700 , where the position of the radiopaque marker  702  is projected on image  600  which would be found on monitor  103  of Fluoroscopic system  100  in  FIG. 10  or on monitor  205  A on fluoroscopic system in  FIG. 11 . The surgeon now has the image that she can precisely follow in inserting a guide pin. 
         [0053]      FIG. 21  A illustrates a Jamshidi  750  with stylet  752  and cannula  751  where the stylet slides into to complete the Jamshidi. Also, illustrated in  FIG. 21  A is target guide holder  755  with an opening that goes completely through the center of  755 . The target guide holder is made of a plastic that cannot be picked up by the X-rays of the fluoroscopic systems. The target guide  755  is held by a standard mechanical arm used in surgery so that it can be properly positioned by the position of the radiopaque marker and the angle in the AP Plane and the Angles in the ML plane for proper insertion of the surgical instruments.  FIG. 21  B illustrates a series of bubble inclomaters  800  in various positions for inclometers  801 ,  802 ,  803 , and  804 . These inclometers will slide into the Jamshidi cannula  805  through opening  806  or the inclometers can slide in to the target guide holder  855  through opening  856  that goes through the entire length of the target guide holder  855  in order to determine the angel for the lateral plane and the AP plane for use correct angle and placement of the instruments such as a Jamshidi to make the initial incision. 
         [0054]      FIG. 21  A illustrates a Jamshidi  750  that can be placed in a target guide holder  755 . The holder would be held by a standard mechanical arm used in surgery (not shown) that would not be picked up on the x-ray of the fluoroscope system, whether they be system illustrated in  FIG. 10, 11  A or  11  B or any other commercial fluoroscopic system.  FIG. 21  B illustrates bubble inclomaters  800  that would be used to provide the correct angle of the Jamshidi. The stylet of Jamshidi  751  would be withdrawn and an inclomater such as  801  can be used by placing in the cannula of the Jamshidi  751  or  806  of  805  in  FIG. 21B  and the angle positioning can be determined for the AP Plane and the ML plane. Finally the position of the Jamshidi  750  in target guide holder  755  would be aligned with a mimic the position of the radiopaque marker  601  in  FIG. 19 . Then the surgeon can position the mechanical arm over the point of intersection of the entry point  51  of  FIG. 4 , which is where the two light sources intersect. Once there is the final position at point  51 , the surgeon can then make the incision using the Jamshidi  750 . The surgeon can also use a trocar, cannula, a drill bit or any surgical device used to make an incision at point  51  in  FIG. 4 . The instant invention and its many uses should not be limited to spine surgery, but can be used in surgery where there are two planes or even where there is a single plane of interest. 
         [0055]      FIG. 22  is an illustration of a wrist  950  having a plate  951  and screws  952  with hand  955  that can benefit from the precision of the instant invention. Horizontal and vertical laser lines can be projected on the plane of the screw holes in the x and y plane and a radiopaque marker can be used to establish the correct position for inserting the screws  952 . 
         [0056]      FIG. 23  is an illustration of a Humeral Shaft  1000  that can benefit from the instant invention as the screw lines  1001  and  1002  can be projected on the skin from the laser light sources, as well as the radiopaque marker, not shown, can illustrate further an exact duplication of the insert points for the screws. 
         [0057]    The method and system here can be used not just for surgery but also for training of surgeons on cadavers or simulated bodies to improve technique and understanding. The training aspect of the instant invention is a key use of the method and system disclosed herein because it will provide a much more precise and accurate surgical technique being developed by surgeons. 
         [0058]    Of course, the foregoing description is that of certain features, aspects and advantages of the present invention, to which various changes and modifications can be made without departing from the spirit and scope of the present invention. 
         [0059]    Moreover, the surgical targeting systems and methods need not feature all of the objects, advantages, features and aspects discussed above. Thus, for example, those skilled in the art will recognize that the invention can be embodied or carried out in a manner that achieves or optimizes one advantage or a group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein. In addition, while a number of variations of the invention have been shown and described in detail, other modifications and methods of use, which are within the scope of this invention, will be readily apparent to those of skill in the art based upon this disclosure. It is contemplated that various combinations or subcombinations of these specific features and aspects of embodiments may be made and still fall within the scope of the invention. Accordingly, it should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the discussed surgical marking systems and methods.