Abstract:
The invention relates to a trajectory guidance instrument that is securable to a surgical tool for use in conjunction with X-ray machines. More particularly, the device includes a radiolucent outrigger having radiodense indicia disposed on the outrigger so that the radiodense indicia is visible via an X-ray machine to provide an angular trajectory for the instrument. The outrigger is securable to various surgical tools for the purpose of providing real time trajectory guidance to surgeons during a procedure. In general, the precision trajectory guidance instrument comprises a substantially rigid outrigger device which it securable to a portion of the surgical tool for trajectory guidance. The trajectory guidance instrument may be attached with clips, fasteners, adhesives, hook and loop or the like.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a trajectory guidance instrument that is securable to a surgical tool for use in conjunction with X-ray machines. In particular, the device includes a radiolucent outrigger having radiodense indicia disposed on the outrigger that is visible via the X-ray machine to provide an angular trajectory for the instrument. 
       BACKGROUND 
       [0002]    Medical procedures involving the vertebrae are normally complicated because of the preciseness and accuracy required to avoid both neural damage and injury to major blood vessels. Precision depth guided instruments are required to perform percutaneous spinal surgery. These surgeries sometimes require penetration of the hard cortical bone of the vertebra and traversal of the softer cancellous bone lying thereunder. A large force is normally required by the surgeon to penetrate the cortical bone. Once the cortical bone is penetrated, extreme care must then be taken to avoid rapidly penetrating through all of the cancellous bone. There is also the danger of rapidly passing through the cancellous bone and then through the cortical bone on the other side of the vertebra. This can result in injury or damage to the spinal cord and/or other organs or blood vessels located adjacent the spine. In some instances, the force required to penetrate the cortical bone is greater than a surgeon can apply by hand. In these instances, a hammer or other similar instrument is required to force the instrument through the cortical bone. When a hammer or similar instrument is used, there is a greater danger of the instrument passing rapidly through the cancellous bone and out the other side of the vertebra. 
       SUMMARY 
       [0003]    Briefly, the invention relates to a trajectory guidance instrument that is securable to a surgical tool for use in conjunction with X-ray machines. More particularly, the device includes a radiolucent outrigger having radiodense indicia disposed on the outrigger so that the radiodense indicia is visible via a radiography, e.g. X-ray, machine to provide an angular trajectory for the instrument. The outrigger is securable to various surgical tools for the purpose of providing real time trajectory guidance to surgeons during a procedure. In general, the precision trajectory guidance instrument comprises a substantially rigid outrigger device which is securable to a portion of the surgical tool for trajectory guidance. The trajectory guidance instrument may be attached with clips, fasteners, adhesives, hook and loop or the like. Alternatively, the trajectory guidance instrument may be permanently affixed or integrally formed to the surgical tool. More than one trajectory guidance instrument may be secured to the same surgical tool, or the trajectory guidance instrument may be rotatable about the surgical tool to provide a compound angle of trajectory. Accordingly, it is an objective of the present invention to provide a trajectory guidance instrument which can be utilized to provide a precise trajectory for a surgical tool. 
         [0004]    It is another objective of the present invention to provide a trajectory guidance instrument which can be secured to a surgical tool to provide a precise trajectory for the tool for insertion into a patient. 
         [0005]    It is yet another objective of the present invention to provide a trajectory guidance instrument that can be secured to a pre-existing surgical tool for providing a precise trajectory for the surgical tool. 
         [0006]    Still yet another objective of the present invention is to provide a trajectory guidance instrument that can be integrally formed as a portion of a surgical tool for providing trajectory guidance to the surgical tool. 
         [0007]    A further objective of the present invention is to provide a trajectory guidance instrument that can be rotated with respect to the surgical tool to provide a compound angle trajectory for the surgical tool. 
         [0008]    An even further objective of the present invention is to provide a trajectory guidance instrument particularly suited for use in spinal surgery to provide a trajectory into a vertebra with a measured angle, the measured angle and distance having been predetermined by radiography. 
         [0009]    Still yet a further objective of the present invention is to provide a trajectory guidance instrument which can be used to ensure a desired trajectory and/or monitoring the trajectory of surgical instruments and/or implants in any number of surgical procedures, such as bone marrow biopsies, placement of spinal implants, spinal surgery, including ensuring proper placement of pedicle screws during pedicle fixation procedures and ensuring proper trajectory during the establishment of an operative corridor to a target site. 
         [0010]    Other objects and advantages of this invention will become apparent from the following description taken in conjunction with any accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. Any drawings contained herein constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Many advantages of the present invention will be apparent to those skilled in the art with a reading of this specification in conjunction with the attached drawings, wherein like reference numerals are applied to like elements and wherein: 
           [0012]      FIG. 1  is a side view of one embodiment of the instrument, illustrated with a jamshidi needle and partial view of a C-arm type x-ray device; 
           [0013]      FIG. 2  is a top view of one embodiment of the instrument, illustrating the indicia under x-ray or fluoroscopy; 
           [0014]      FIG. 3  is a perspective view of one embodiment of the outrigger; 
           [0015]      FIG. 4  is a perspective view of one embodiment of the outrigger; 
           [0016]      FIG. 5  is a perspective view of one embodiment of the outrigger; 
           [0017]      FIG. 6  is a perspective view of one embodiment of the outrigger; 
           [0018]      FIG. 7  is a side view of one embodiment of the present invention; 
           [0019]      FIG. 8  is a partial view of the embodiment illustrated in  FIG. 7   
           [0020]      FIG. 9  is a partial radiographic view of the embodiment illustrated in  FIG. 7  in operation; 
           [0021]      FIG. 10  is a representative illustration of a portion of the human spine; 
           [0022]      FIG. 11  is a side view illustrating one embodiment of the present invention; 
           [0023]      FIG. 12  is a side view illustrating one embodiment of the present invention; 
           [0024]      FIG. 13  is a side view illustrating one embodiment of the present invention; 
           [0025]      FIG. 14  is a side view illustrating one embodiment of the present invention; 
           [0026]      FIG. 15A  is a radiographic image illustrating operation of the present invention; 
           [0027]      FIG. 15B  is a radiographic image illustrating operation of the present invention; 
           [0028]      FIG. 15C  is a radiographic image illustrating operation of the present invention; 
           [0029]      FIG. 16A  is a radiographic top view image illustrating operation of one embodiment of the present invention; 
           [0030]      FIG. 16B  is a side view illustration of the radiographic image illustrated in  FIG. 16A ; 
           [0031]      FIG. 17A  is an end view illustrating operation of one embodiment of the present invention; 
           [0032]      FIG. 17B  is a perspective view of the embodiment illustrated in  FIG. 17A ; 
           [0033]      FIG. 18  is a partial perspective view of an alternative embodiment of the present invention; and 
           [0034]      FIG. 19  is a side view of one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred, albeit not limiting, embodiment with the understanding that the present disclosure is to be considered an exemplification of the present invention and is not intended to limit the invention to the specific embodiments illustrated. 
         [0036]    Various embodiments and surgical uses of a trajectory monitoring system are described for enhancing the safety and efficiency of surgical procedures. In one example, set forth by way of example only, the present invention may facilitate safe and reproducible pedicle screw placement by monitoring the axial trajectory of various surgical instruments used during pilot hole formation and/or screw insertion. In another example, set forth by way of example only, intraoperative imaging performance may be improved and radiation exposure minimized by monitoring the precise orientation of the imaging device. In yet another example, monitoring the orientation of surgical access instruments can aid in both the insertion and positioning of the access instruments themselves, as well as aiding in the later insertion of instruments and/or implants through or with the surgical access instruments. It is expressly noted that these examples are set forth by way of example; and that the present invention may be suitable for use in any number of additional surgical actions where the angular orientation or trajectory or depth (linear distance traveled) of instrumentation and/or implants is important. By way of example only, the present invention may be useful in directing, among other things, the formation of tunnels for ligament or tendon repair and the placement of facet screws. Other uses may include orientation of drills, saws, cutters or other hand operated tools used in the performance of surgery where specific fiducial markers may be useful. 
         [0037]      FIGS. 1-2 , which are now referenced, illustrate one embodiment of the present invention and one manner in which it may be assembled. Like reference numerals refer to like components in the various figures.  FIG. 1  is a schematic representation showing an embodiment of a precision trajectory guidance instrument  100  illustrated herein as an outrigger  10  secured to a jamshidi needle  40 . The instrument  10  comprises a radiolucent body portion  14  having radiopaque indicia  18  forming a front sight  30  and a rear sight  32  which can be aligned under radiography for the purpose of preventing unintended injury to surrounding tissues, nerves, blood vessels, cartilage or bone. The visibility of the indicia  18  under radiography ensures a precise trajectory and/or monitoring of the trajectory of surgical instruments and/or implants in any number of surgical procedures, such as bone marrow biopsies, placement of spinal implants, spinal surgery, including ensuring proper placement of pedicle screws during pedicle fixation procedures, and ensuring proper trajectory during the establishment of an operative corridor to a spinal target site. A trajectory indicium  19 , e.g. rear sight  32 , which is also radiopaque is provided for determining an angular relationship and is aligned in a horizontal or vertical plane between the front sights  30 . The indicia  18  can also include at least one reference trajectory sight  34  which indicates various degree graduations between the front sights  30 . In some embodiments, the indicia  18  may be embossed, printed, painted, embedded or otherwise imprinted on a sticker, clip or outrigger. The radiopaque materials utilized for the indicia may include one of several metals known to be radiopaque such as, but not limited to, lead, tantalum, tungsten, gold, stainless steel or the like. Alternatively, the indicia may be a radiopaque polymer; such polymers are available under the trade name LATIGRAY from LATI Industries Thermoplasici S.p.A. of Italy, and may be directly adhered or molded into the outrigger. 
         [0038]    By way of example only, while placing bone screws through a pedicle  42  (which is a small generally tubular structure connecting posterior elements of a vertebra  44  to the vertebral body), it is critical to ensure the screw is contained within the pedicle and does not breach the outer pedicle wall. Since the pedicle  42  is surrounded by delicate nervous tissue, a breach can have serious consequences for the patient, ranging from mild pain to paralysis. One way to mitigate the risk of a pedicle breach during screw placement (including preparation for screw placement, such as pilot hole formation and tapping) is to determine the angular orientation of the pedicle, and thereafter advance the necessary instruments and screws along the determined trajectory. By orienting the surgical access components along the pedicle trajectory, the surgical instruments and pedicle screws may be simply and efficiently advanced along the same trajectory, and thus avoid a breach by “eyeballing” alignment with the access components. 
         [0039]    Thus, in spinal surgery, before the pilot hole is formed with the jamshidi  40 , the desired angular trajectory must first be determined. Preoperative superior view utilizing AP fluoroscopy, MRI or CAT scan imaging device(s)  20  are used to determine the trajectory once the Jamshidi  40 , in combination with the outrigger  10 , has been placed at the anatomical site for which the surgery is to be conducted. C-arm fluoroscopes are used extensively during many surgical procedures. During spinal surgery for example, the C-arm is used frequently to help locate specific structures of the spine, to direct the positioning of surgical instruments and/or instrumentation, and to verify the proper alignment and height of vertebra, among other uses. Imaging devices, such as the C-arm, are typically provided with a scale (not shown) indicating the orientation of the radiography beam  24  with respect to the patient and thus, in this example, the Jamshidi  40  in combination with the outrigger  10 . In this manner, the imaging device  20  can direct a radiography beam  24  across the outrigger  10  at a known angle, causing the indicia  18  to become visible in the resulting image  20  ( FIG. 2 ). As shown in  FIG. 2 , the indicia  18 , e.g. front sight  30  can be viewed in combination with the rear sight  32  to define the outer boundaries of the desired angle which is visible between the front sights  30 . Spacing between the front sights  30  can be altered to provide any desired range of angle indication. It should also be noted that while only two front sights  30  are illustrated, any number of reference trajectory sights  34  may be provided to indicate angles or portions of angles without departing from the scope of the invention. See  FIGS. 13, 15, 16 and 17  which illustrate embodiments having at least three different angular indicators. In this manner, for surgical procedures such as those to the spine wherein the coronal (medial) angle  26  increases approximately 5 degrees per level, with respect to centerline  28  from L1 to the sacrum ( FIG. 10 ), a plurality of front sights  30  or reference trajectory sights  34  may be provided, whereby the surgeon can utilize a different front sight  30  or reference trajectory sight  34  for each level of the spine. In some embodiments, the front sights  30 , rear sight(s)  32  and reference trajectory sights  34  may include different shapes including, but not limited to, numbers, letters, 2D and 3D geometric shapes and the like to indicate different angles, sights or reference sights. The indicia  18  may or may not be visible to the naked eye as the outrigger  10  is viewed. It should also be noted that while the present disclosure depicts a jamshidi needle, the teachings of the present disclosure may be applied to other types of surgical tools without departing from the scope of the invention. For example, drills, saws, reamers, shapers and other hand operated tools used for surgical operations may benefit from the teachings of the present invention. In addition, the teachings of the present invention may be utilized for the implantation of various implants, catheters, scopes and the like without departing from the scope of the invention. It should be further noted that while the outrigger  10  of the present embodiment is illustrated as being attached to the surgical tool, the teachings of the present device may also be utilized as a permanently secured or integrally formed portion of a surgical tool without departing from the scope of the invention. 
         [0040]    Referring to  FIGS. 1 and 3 , one embodiment of an outrigger  10  is illustrated. In this embodiment, the radiolucent body portion  14  of the outrigger is provided with a tube portion  50  for attachment to a surgical tool such as a Jamshidi  40 . The tube portion  50  includes an inner lumen  52  sized to extend around the shaft  46 . Thumb screws  54 , friction or the like may be utilized to hold the outrigger in place on the shaft  46  or any other portion of a surgical tool that is generally round in shape. This construction also permits the outrigger  10  to be rotated as needed about the surgical tool and additional radiography shots taken in different planes whereby compound angles and the like may be indicated by the device. 
         [0041]    Referring to  FIGS. 1, 4 and 5 , one embodiment of an outrigger  10  is illustrated. In this embodiment, the radiolucent body portion  14  of the outrigger is provided with a tab portion  60  or a perpendicular tab portion  70  for attachment to a surgical tool. The tab portion  60 ,  70  includes an adhesive  62  or the like and an adhesive cover  64  for easy attachment to a surface of a surgical tool. This construction also permits the outrigger  10  to be secured as needed to the surgical tool. 
         [0042]    Referring to  FIGS. 1 and 6 , one embodiment of an outrigger  10  is illustrated. In this embodiment, the radiolucent body portion  14  of the outrigger is provided with clips  80  for attachment to a surgical tool. The clips  80  include a spring member  82  or the like and a lever  84  for easy attachment to a surface of a surgical tool. This construction also permits the outrigger  10  to be secured as needed to a portion of the surgical tool in which the clip will expand large enough to fit at least partially around. 
         [0043]      FIGS. 7-9, 11-14  which are now referenced, illustrate one embodiment of the present invention and the manner in which it is constructed.  FIG. 7  is a schematic representation showing an embodiment of a precision depth and trajectory guidance instrument  200 . The instrument  200  comprises a substantially rigid cannula  101  including a first end  102  and a second end  103 , said first end including a fastener means or threaded member  104   a  for securing to a handle  105 , said second end including a sharp tip  106  for penetrating the skin and tissue of a patient. The handle  105  is secured to the first end  102  of the cannula  101 . The handle may be fixed to the cannula by various means, which include overmolding, or can be detachably removable. In embodiments where the handle  105  is detachably removable, as in  FIG. 2 , the handle comprises a lower portion, collar or cylindrical portion  107  including a fastener means which may include, but should not be limited to, bayonet mount, locking taper, adhesive or threaded member  104   b  constructed and arranged to cooperate with the fastener means or threaded member  104   a  of the cannula  101  for removable attachment to the cannula. This lower portion, collar or cylindrical portion  107  is fixedly secured to the cannula  101 . 
         [0044]    The handle  105  may be permanently or removably attached to the cannula  101 , and may be shaped and dimensioned in any of a number of suitable variations. In some embodiments, wherein the cannula  101  is a Jamshidi-type needle, the handle  105  preferably has an ergonomic shape that can comfortably fit into a surgeon&#39;s or medical technician&#39;s hand. The handle can be shaped to include an upper curved portion  109  which is shaped to conform to an individual&#39;s palm. The lower portion of the handle  110  is also curved. The curve of the lower portion of the handle is designed to be grasped by the fingers of an individual to assist in the control of the cannula  101 . The handle  105  is used to drive the cannula into, and sometimes through bones of a vertebra. Sometimes the cannula  101  can be driven through the bone only by using pressure exerted by an individual&#39;s hand. Other times a hammer or other instrument must be employed to drive the cannula  101  through a bone. There is a risk that, when a hammer or similar instrument is utilized, the Jamshidi-type cannula  101  will pass too far into a vertebra. This can cause damage to nerves located nearby. Sometimes the needle passes completely through the vertebra and injures an adjacent blood vessel or internal organ. 
         [0045]    For the purpose of preventing unintended injury to surrounding tissues, nerves, blood vessels, cartilage or bone, indicia  108  are disposed on the handle  105 . The indicia  108  ensure a precise trajectory and/or monitoring of the trajectory and/or depth of surgical instruments and/or implants in any number of surgical procedures, such as, bone marrow biopsies, placement of spinal implants, spinal surgery, including ensuring proper placement of pedicle screws during pedicle fixation procedures, and ensuring proper trajectory during the establishment of an operative corridor to a spinal target site. A trajectory indicium for determining an angular relationship is aligned in a horizontal or vertical plane between the trajectory indicium and the sharp tip of the cannula. The indicia  108  can also include at least one reference trajectory indicium  120  ( FIG. 14 ). The reference indicium provides a reference point or area that indicates where the tip of the tool will be if driven a predetermined distance further into the target site. In some embodiments, the indicia  108  may be embossed, printed, embedded or otherwise imprinted on a sticker or a clip. In other embodiments, the indicia are etched or electro-plated into the handle. In some embodiments, the handle includes a cutout region for accommodating attachment of a universal clip comprising indicia for trajectory and depth. It should be noted that while the present disclosure depicts a jamshidi needle, the teachings of the present disclosure may be applied to other types of surgical tools without departing from the scope of the invention. For example, drills, saws, reamers, shapers and other hand operated tools used for surgical operations may benefit from the teachings of the present invention. 
         [0046]    Referring to  FIGS. 11-14 , in some embodiments the trajectory indicia comprise a 30 degree indicium, a 15 degree indicium, or combinations therebetween. In the case of a jamshidi needle, the positioning of the trajectory indicia on the surgical tool will vary according to the size of the cannula. For example, an indicium indicating a 30 degree angle  122  will be marked at 8.66 cm from the opposing end  124  of the handle of a 15 cm long cannula  101 . When viewed from the top, the indicium marking the 30 degree angle  122  is aligned with the tip  106  of the cannula  101  to provide a trajectory for the surgical instrument. For a cannula having a length of 10 cm, the 30 degree indicium will be deposed at 5.77 cm from the center of the handle. Similarly, the indicia marking distance traveled are disposed on the collar and/or the cannula. 
         [0047]    Accordingly, before the pilot hole is formed, the desired angular trajectory must first be determined. Preoperative superior view AP fluoroscopy, MRI or CAT scan images are used to determine the trajectory once the instrument has been placed at the anatomical site for which the surgery is to be conducted. A trajectory line  21  is drawn from the tip of the instrument to the appropriate indicium. The reference line is the cannula. The resulting angle between the trajectory line and the reference line is the desired angle to be used in forming the pilot hole. Alternate and/or additional methods for predetermining the pedicle angles are also contemplated and may be used without deviating from the scope of the present invention. As used herein, pilot hole formation is meant to encompass any of, or any combination of, creating a hole in a skin, tissues, bone etc. (such as, for example only, by awling, boring, drilling, etc. . . . ) and preparing a previously formed hole (such as, for example only, by tapping the hole). 
         [0048]    Referring to  FIGS. 9, 14-17 , it is also very difficult for a surgeon or medical technician to judge the depth of penetration of a surgical instrument into the vertebra or other anatomical feature. The remedy for this problem lies in the present invention. First, the trajectory and depth instrument is placed at the anatomical site for which the surgical procedure is to occur and a radiography image of the vertebra being operated upon is taken ( FIGS. 9, 16 and 17 ). The trajectory and depth that the surgeon wants the instrument or device to penetrate into the vertebra is thus identified prior to the surgery, allowing for an accurate surgical corridor. Accordingly, in another embodiment, a depth indicium  120  which would indicate the linear distance of the depth of the cannula is disposed into the anatomy. For example, for a projected 20 mm advance point, the depth indicium would be at 9.815 cm from the angular reference mark. ( FIG. 14 ). 
         [0049]    In another embodiment, a method of determining an optimal angular trajectory and linear depth for safely accessing a vertebral pedicle of a patient comprises the steps of positioning a depth and trajectory guidance instrument at a desired penetration site on a skin surface of a patient. For example, in  FIG. 9 , to select a starting point for pedicle  201  penetration, the instrument may be placed in the trajectory lateral position for the pedicle of interest. The instrument comprising the indicia  108  disposed on the handle and/or cannula  101  for trajectory and linear depth guidance allows for orienting the instrument along a desired trajectory by aligning the trajectory indicium with the sharp tip  106  and imaging the positioning of the instrument against the patient&#39;s anatomical image to determine an optimal surgical trajectory and depth corridor ( FIG. 9 ). 
         [0050]    Referring to  FIG. 18 , an alternative embodiment of the present invention is illustrated. In this embodiment, a bubble level configuration  200  of the present device may be provided which may clip onto the handle of the jamshidi, or alternatively is included within the handle, so as to ensure the instrument trajectory does not deviate during surgery and the angle is precise. The bubble level device comprises a handle with a bulls-eye level  202  mounted in it. When the handle is placed on a flat surface, an indicator ring  204  should encircle a bubble  206  captured within the glass  208 . When the bubble is within the first indicator ring  204 , the display should read approximately zero-degrees. Additional rings  210  would indicate the angle. For example, 10, 20 and 30 degree indicator rings  210  should encircle the bubble  206  captured within the glass. A pair of parallel lines  212  may also be provided when the bubble level is round for aligning the tool axially. In an alternative embodiment (not shown), the bubble level could be a bent elongated tube having the degree indicators printed thereon. The indicators and fluid within the level can be constructed for visualization under radiation, whereby the surgeon can read the device through the fluoroscopy or the like. 
         [0051]    Referring to  FIG. 19  an alternative embodiment of the precision guidance instrument  300  is illustrated. The precision guidance instrument  300  is illustrated herein as an outrigger  310  secured to a jamshidi needle  40 . The outrigger  310  comprises a radiopaque body portion  314  having radiopaque indicia  18  forming at least one more preferably a pair of rear sights  32  which can be aligned with a portion of the surgical tool illustrated herein as the point  106  of a jamshidi needle under radiography for the purpose of preventing unintended injury to surrounding tissues, nerves, blood vessels, cartilage or bone. The visibility of the indicia  18  under radiography ensures a precise trajectory and/or monitoring of the trajectory of surgical instruments and/or implants in any number of surgical procedures, such as bone marrow biopsies, placement of spinal implants, spinal surgery, including ensuring proper placement of pedicle screws during pedicle fixation procedures and ensuring proper trajectory during the establishment of an operative corridor to a spinal target site. A trajectory indicium  19 , which is also radiopaque is provided for determining the path of the surgical tool to its intended destination. The indicia  18  can also include at least one reference trajectory sight  34  which indicates various degree graduations between the front sights  30 . In some embodiments, the indicia  18  may be embossed, printed, painted, embedded or otherwise imprinted on a sticker, clip or outrigger. 
         [0052]    All patents and publications mentioned in this specification are indicative of the levels of those skilled in the art to which the invention pertains. All patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference. 
         [0053]    It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention, and the invention is not to be considered limited to what is shown and described in the specification and any drawings/figures included herein. 
         [0054]    One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objectives and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments, methods, procedures and techniques described herein are presently representative of the preferred embodiments, are intended to be exemplary and are not intended as limitations on the scope. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in the art are intended to be within the scope of the following claims.