Abstract:
The invention includes a surgical fastener and associated deployment system and method that overcomes the drawbacks of prior art surgical mesh fixation devices. The surgical fastener and deployment system may be used to fixate a surgical mesh material to the abdominal wall for the purpose of hernia repair. In accordance with one embodiment, the fastener may include an anchor head comprising a bi-pyramid framework. The anchor head is preferably made from a highly deformable and biocompatible material that withstands high flexural strain within an oscillatory environment. The anchor head may be provided in an elongate, undeployed configuration, and then expanded during deployment into a second, generally planar configuration. The anchor head may be biased to expand into the generally planar configuration from the undeployed configuration in a variety of manners.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Patent Application Ser. No. 60/959,343, Filed Jul. 13, 2007. This patent application is incorporated by reference herein in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to systems and methods for attaching a prosthetic device to the surface of tissue, and more particularly, to the application of mesh to cover a hernia defect as well as devices for applying such a mesh and holding such mesh in a desired position. 
         [0004]    2. Description of Related Art 
         [0005]    The anterior abdominal wall is comprised of a muscle layer, surrounded by strong connective tissue known as fascia. Adipose tissue (fat) and dermal layers (skin) are located on the outside of the muscle layer. A weakness in the abdominal wall, for example caused by a former surgical incision, may allow the internal organs to pass through, causing a hernia. Hernias are relatively common and may cause pain or strangulation of the bowel, in which blood flow to the tissue is restricted. Such hernias often need to be repaired. 
         [0006]    Many methods of hernia repair are known. Among the most popular is the use of a mesh barrier placed on the inside of the abdominal wall to cover the defect. This procedure can be accomplished through open surgery, however minimally invasive surgery is becoming increasingly popular as a new approach to treat this condition. 
         [0007]    The minimally invasive laparoscopic surgical techniques typically require only a few small incisions (0.5-1.5 centimeters) in the abdomen, instead of a larger incision typical of open surgery. A trocar (i.e., a tube-shaped port which typically has a 5-12 millimeter internal diameter) is inserted into each incision. The abdomen is then inflated with insufflation gas (e.g., carbon dioxide), and then a small camera and surgical tools are advanced through the trocars. The image from the camera is typically projected on a monitor in the operating room, allowing the surgeon to see the inside of the cavity and the extent of the defect in the abdominal wall. Laparoscopic tools are generally designed with a long wand-like distal end that is inserted into the cavity through the trocar. The wand-like distal end is then positioned manually by the surgeon and may be activated, for example, by the squeeze of a trigger or other suitable means. 
         [0008]    For cases of laparoscopic ventral hernia repair, the surgeon first identifies the hernial defect before cutting the mesh to be about 3-5 centimeters longer in diameter than the size of the hole itself. The mesh is then inserted into the abdominal cavity through a trocar, and secured to the anterior abdominal wall in such a fashion that it covers the hernial defect. To provide a secure fixation of the mesh to the anterior abdominal wall, sutures are often used to secure the mesh to the abdominal wall. The sutures are placed on the mesh and then advanced through the abdominal wall until they are visible outside the abdominal wall. The sutures are then tied off against the abdominal wall. Generally, 4 or more sutures are used to fix the mesh to the abdominal wall, depending on the size of defect. Tacks are then typically applied near the perimeter of the mesh to fix the mesh to the abdominal wall. The tacks are placed at close intervals, preventing the bowels (or other organs) from passing between the mesh and the abdominal wall. Such tacks come in several varieties and may be made of metal or absorbable materials; typical examples can be found, for example, in U.S. Pat. No. 6,036,701, U.S. Pat. No. 5,904,696, and U.S. Pat. No. 6,837,893 A1. Each of these patents is incorporated by reference herein in its entirety. 
         [0009]    The laparoscopic method for repairing hernias may cause several problems. For example, transfascial sutures can often cause excessive post-operative pain. Specifically, internal forces exerted on the mesh are typically transferred to the muscle layer through these sutures. The sutures, in turn, concentrate these forces causing pain. Moreover, sutures have relatively low compliance compared to abdominal tissues, and therefore sutures may “pinch” when the muscle tissue contracts, similarly causing irritation to surrounding tissue. Furthermore, metal tacks (as described above) may occasionally dislodge from the abdominal wall, permitting them to irritate other tissue as they move within the body. Without the fasteners to hold the mesh in place, the mesh may come loose. These events may lead to additional complications, and possibly additional surgery. 
         [0010]    Given the problems that are associated with current techniques of securing meshes, it is desirable to have a fastener and associated delivery system capable of penetrating all fascial layers of the abdominal wall, securing the mesh, and withstanding the internal forces of the body without patient discomfort and without the risks of fastener disengagement. It is also desirable that the fastener be delivered by way of laparoscopic techniques with minimal damage to surrounding tissues. It would also be advantageous to have a fastener that complies with surrounding bodily tissues. The present invention provides a solution for these problems. 
       SUMMARY OF THE INVENTION 
       [0011]    Advantages of the present invention will be set forth in and become apparent from the description that follows. Additional advantages of the invention will be realized and attained by the methods and systems particularly pointed out in the written description and claims hereof, as well as from the appended drawings. 
         [0012]    To achieve these and other advantages and in accordance with the purpose of the invention, as embodied herein, the invention includes a surgical fastener and associated deployment system and method that overcomes the drawbacks of prior art surgical mesh fixation devices. The surgical fastener and deployment system may be used to fixate a surgical mesh material to the abdominal wall for the purpose of hernia repair. 
         [0013]    In accordance with one embodiment, the fastener may include an anchor head comprising a bi-pyramid framework. The anchor head is preferably made from a highly deformable and biocompatible material that withstands high flexural strain within an oscillatory environment. The anchor head may be provided in an elongate, undeployed configuration, and then expanded during deployment into a second, generally planar configuration. The anchor head may be biased to expand into the generally planar configuration from the undeployed configuration in a variety of manners. 
         [0014]    In accordance with an embodiment of a method of the invention, a fastener as embodied herein may be deployed using a delivery system as described herein. A distal end of a delivery device containing a fastener disposed in an undeployed state may be advanced to a location proximate the interior surface of the abdominal wall of a patient. The fastener may be deployed by advancing the fastener distally with respect to the delivery system, permitting the fastener to expand to a neutral, deployed state upon release from said introducer. 
         [0015]    In accordance with a further aspect, the fastener may be disposed in an undeployed state within an introducer portion of the delivery system. In accordance with one embodiment, the introducer portion may be movably disposed within a main body portion of the delivery system. The distal end of the main body portion of the delivery system may be blunt to prevent damage to tissue, and the introducer portion may have a sharpened distal tip that may be advanced out of the distal end of the main body portion of the delivery system and advanced through fascia to permit transfascial fixation. 
         [0016]    In accordance with a preferred embodiment, a sensing mechanism may be located proximate the distal end of the delivery system (e.g., at the distal end of the introducer portion) to detect the difference between muscle, fascial, and adipose tissues, to facilitate accurate transfascial placement of the surgical fastener. Once the fastener is deployed from the introducer, in accordance with one embodiment, a portion of the fastener may be collapsed (e.g., the anchor head portion) by application of a force to the fastener (e.g, applied by way of a suture or other filament embedded in the anchor head). When the fastener is approximately flush with the fascia in a generally planar state, a suture clip or other fastener may then be applied (e.g., to the filament on the interior surface of the abdominal wall) thus keeping the mesh against the interior surface of the abdominal wall. Surgical fastener systems made in accordance with the present disclosure are preferably compatible with commercial suture clip appliers. As will be understood by those of skill in the art, the fastener and the delivery device may be take on a variety of configurations within the spirit and scope of the present disclosure. 
         [0017]    It is to be understood that the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention claimed. 
         [0018]    The accompanying drawings, which are incorporated in and constitute part of this specification, are included to illustrate and provide a further understanding of the method and system of the invention. Together with the description, the drawings serve to explain principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is an illustration of an exemplary coordinate system {X, Y, Z} defined with respect to the body of a patient during an exemplary laparoscopic procedure. 
           [0020]      FIG. 2(   a ) is an elevation view of a first representative embodiment of a fastener made in accordance with the invention in an elastically relaxed state. 
           [0021]      FIGS. 2(   b )- 2 ( c ) illustrate an exemplary method for manufacturing the fastener of  FIG. 2(   a ). 
           [0022]      FIG. 3  is a top view of the fastener of  FIG. 2(   a ) in an elastically relaxed state. 
           [0023]      FIG. 4  is a perspective view of the fastener of  FIG. 2(   a ) in an elastically relaxed state. 
           [0024]      FIG. 5  is an elevation view of the fastener of  FIG. 2(   a ) in an elastically deformed state prior to deployment. 
           [0025]      FIG. 6  is a top view of the fastener of  FIG. 2(   a ) in an elastically deformed state prior to deployment. 
           [0026]      FIG. 7  is an elevation view of the fastener of  FIG. 2(   a ) in a deployed state. 
           [0027]      FIG. 8  is a top view of the fastener of  FIG. 2(   a ) in a deployed state. 
           [0028]      FIG. 9  is an elevation view illustrating a filament (e.g. a suture) incorporated into an exemplary embodiment of a fastener made in accordance with the invention. 
           [0029]      FIG. 10  is a top view illustrating a filament (e.g. a suture) incorporated into an exemplary embodiment of a fastener made in accordance with the invention. 
           [0030]      FIG. 11  is an illustration of an exemplary embodiment of a delivery system made in accordance with the invention. 
           [0031]      FIG. 12  is an illustration of a distal portion of an exemplary embodiment of a delivery system made in accordance with the invention. 
           [0032]      FIG. 13  depicts schematic views illustrating exemplary wiring layouts for an electrical impedance sensor for the delivery system made in accordance with the invention. 
           [0033]      FIG. 14  depicts schematic views illustrating exemplary optical fiber layouts for an optical sensor for the delivery system made in accordance with the invention. 
           [0034]      FIG. 15  is an illustration of a distal portion of a delivery system made in accordance with the invention that depicts an exemplary arrangement of electrical impedance contacts. 
           [0035]      FIG. 16  is an illustration of a distal portion of a delivery system made in accordance with the invention depicting an exemplary arrangement of optical fibers 
           [0036]      FIG. 17  is an illustration of an exemplary sensor readout for a tissue depth gauge made in accordance with the invention. 
           [0037]      FIG. 18  is an illustration of another exemplary sensor readout for a tissue depth gauge made in accordance with the invention. 
           [0038]      FIGS. 19(   a )- 19 ( f ) are schematic views illustrating the insertion and the locking of an exemplary fastener made in accordance with the invention between fascial and adipose tissues. 
           [0039]      FIG. 20  is a schematic view of a deployed fastener in accordance with the invention. 
           [0040]      FIG. 21  is an elevation view of a second representative embodiment of a fastener made in accordance with the invention in an elastically relaxed state. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0041]    Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. The method and corresponding steps of the invention will be described in conjunction with the detailed description of the system. 
         [0042]    Devices and methods provided in accordance with the invention may be used generally in surgical procedures. Such devices and methods are particularly advantageous in affixing mesh to tissue in the course of surgery to repair a hernia defect. 
         [0043]    For purposes of illustration, and not limitation, exemplary embodiments of devices and methods provided by the invention are illustrated in  FIGS. 2-21  herein. In accordance with a first embodiment, an improved fastener is provided that may be delivered using a delivery system. 
         [0044]    As embodied herein and as depicted in  FIG. 2(   a ), the fastener includes an anchor head portion  29 . Various views of the fastener of  FIG. 2(   a ) are provided in  FIGS. 3-12  and  19 - 20 . A second representative embodiment of an anchor head  129  is depicted in  FIG. 21  and described in detail below. In these drawings, an anchor head is depicted with three legs although it could include any suitable number of legs or struts (e.g., 2, 4, 5, 6, etc.). In accordance with the present disclosure, three struts are preferred. 
         [0045]    As depicted, the anchor head  29  includes three equally-spaced legs  3   a - f  whose ends are connected to form the framework of a deformable bi-pyramid, as shown, for example, in  FIG. 2(   a ). The bi-pyramid comprises a polyhedron that is formed by joining a pyramid and its mirror image in a base-to-base arrangement. While it is shown in  FIG. 6  that each leg (also referred to herein as a “strut”)  3   a - f  has a generally rectangular cross-sectional profile, other cross-sectional profiles may be employed (e.g., circular, triangular, elliptical, etc.) to modify the anchor for specific uses. 
         [0046]    In accordance with a preferred embodiment, anchor head  29  is made from a durable and deformable biocompatible material, such as medical grade polyethylene or polypropylene. Examples of other materials that may be used to construct the anchor head  29  include, but are not limited to, nickel-titanium alloys (e.g., NITINOL®), other shape memory materials, silicone, polyurethane, polyethylene terephthalate (PET), and/or any other biocompatible absorbable materials as well as other metals besides nickel-titanium alloys, particularly metals having a high strength-to-elastic modulus ratio. The anchor head  29  may be coated, or partially coated, with a biocompatible lubricant that facilitates an easier insertion of the fastener into the body tissue, or prolongs anti-irritant characteristics. 
         [0047]    The anchor head  29  may be manufactured using a variety of techniques, including several mass production techniques. For example, stamping techniques, laser cutting techniques and waterjet cutters may be used, among others. In accordance with one illustrative example, the anchor head ( 29 ,  129 ) may be made in two pieces as depicted in  FIGS. 2(   b )- 2 ( c ). Specifically,  FIG. 2(   b ) depicts a top view of an anchor after it is stamped in a manufacturing process, while  FIG. 2(   c ) depicts a schematic elevation cross sectional view of such a process. First, two layers of material  301 ,  302  (e.g., polymeric sheet material) are disposed on top of each other. Next, a die  310  may cut out a pattern, wherein each of the upper and lower halves of the anchor head are formed from the top and bottom sheets  301 ,  302 , respectively. For example, the upper sheet layer  301  may include legs/struts  3 ( a, b, c ) while the lower sheet layer  302  may include legs/struts  3 ( d, e, f ). The free ends  3 ′ of each strut may then be attached to each other, such as by welding or other desired attachment technique, for example, by incorporating heating elements  320  into the periphery of the die  310 , or by other suitable technique. A mandrel  330  may be disposed between the two layers during the manufacturing operation to impart a curved shape to the anchor such that it maintains that shape in an elastically relaxed state. The mandrel may be removed, for example, when the manufacturing process is complete. 
         [0048]    As depicted in  FIG. 12 , the anchor head  29  is adapted and configured to fit inside an introducer portion  2  of a delivery system with the anchor head  29  in an elongate condition (designated as  8 ). In a relaxed state, each leg  3   a - 3   f  of each anchor head  29  is oriented at an angle  12  with respect to the centerline of the anchor head  29 . The orientation of the anchor head  29  is such that the plane of the anchor head base  50  is substantially perpendicular to the longitudinal direction of the introducer  2  of the delivery system.  FIGS. 9 and 10  illustrate a filament  14  (e.g., suture thread) that can be embedded in the top section  10  of the anchor head  29  to later facilitate deployment of anchor head  29 . Filament  14  serves to connect anchor head  29  to a retainer, such as a suture clip  15 , through an opening  51  created by deployment of the suture through inner abdominal fascia  49 . Filament  14  may move with the adjacent muscle  30  so as not to tear the muscle  30 . While a variety of materials may be used for filament  14 , it is preferred to us a standard, non-absorbable suture thread; such as 0 or 2-0 polyethylene or polypropylene suture material. Once the anchor head  29  is deployed and collapsed, as shown in  FIG. 7 , each leg  3   a - f  of the anchor head  29  is disposed at an angle  13  with respect to the base plane of the bi-pyramid, such that once fastened to the inner abdominal fascia  49 , the bottom section  11  of the anchor head  29  is nearly flush with the anterior fascia  31 , as depicted in  FIG. 19 . The top section  10  of the anchor head  29  preferably possesses a thicker cross-section than the bottom section  11  for the purpose of increased strength and structural stiffness. As further depicted, for example, in  FIG. 4 , anchor head  29  includes nine living hinges  20   a - 20   i  to help maintain compliance between the anchor head base  50  and the muscle layer  30  of patient. The top section  10  of the three legs  3   a - c  disposes itself in a downward curved position when in the collapsed state  9  as depicted in  FIGS. 19(   e )-( f ) and  FIG. 20 . This concavity advantageously provides added structural support in the direction of the filament tensile force by making the anchor head  29  more resistant to inversion. Inversion represents a failure mode, wherein the hinges of the legs  3   a - f  bend such that the angle  13  is negative. The optimized contact geometry is due to the difference in the leg lengths of legs  3   a - c  with respect to legs  3   d - f . During deployment, the living hinges preferably plastically deform to facilitate holding mesh  21  in place. 
         [0049]    A variety of delivery systems may be used to deliver fasteners in accordance with the present invention. While the delivery system may be reusable, it is preferably a disposable device that may be discarded after a surgical procedure. In order to secure a fastening system including anchor head  29 , filament  14  and retainer  15  as embodied herein, as depicted in  FIG. 19 , it is preferred to insert the anchor head  29  from inside the abdominal cavity through the muscle tissue of the abdominal wall, and then to deploy the anchor in the adipose tissue. Each anchor head  29  is inserted by bringing the distal end of barrel  1  of the delivery system to a desired location on the inside of the abdominal wall of the patient as depicted in  FIG. 19(   a ). This motion also forces the mesh  21  against the interior surface of the abdominal wall. The introducer portion  2  is then extended from the barrel  1  and so as to pierce through the mesh  21  and into the muscle layer  30  as depicted in  FIG. 19(   b ). A sensor  22  is preferably used to detect when the introducer has passed through the muscle and fascia to a location within the adipose tissue  37  below the skin  48  as depicted in  FIG. 19(   c ). During assembly, anchor heads  29  are preferably deformed into the extended state (designated as  8 ), and then disposed along the length of the barrel  1 . The anchor heads  29  are preferably adapted and configured to fit inside an introducer having an inner diameter of about 2-3 millimeters. The introducer preferably has an outer diameter between about 3-4 mm. As depicted in  FIG. 11 , an actuator  17  may use a mechanical, electromechanical or hydraulic drive, such as a mechanical transmission, such as gears and/or levers (or other means), to actuate a lead screw (not depicted). The lead screw, in turn, is disposed proximally to the anchor heads along the longitudinal axis of the device and advances the anchor heads  29  through the barrel  1  and into the introducer  2  as the actuator  17  is actuated. As the lead screw rotates, the anchor head  29  is pushed out of the tip of the introducer  2 . As will be appreciated, the lead screw may be advanced by a totally mechanical means, or the actuator may activate an electrical circuit that drives an electric motor that advances the lead screw. 
         [0050]    Once the anchor head  29  has been advanced from the introducer  2  beyond its horizontal mid-plane  16 , a ratcheting device inside the delivery device housing  7  can be used to apply tension to the filament  14 . The opposite forces applied to the anchor head  29  by the filament  14  (tensile force) and by the other anchors in their extended states  8  while inside the introducer  2  (compressive force) act to compress the anchor head  29  into its collapsed state  9  as depicted in  FIG. 19(   d ). An indicator  18  on the housing  7  (if desired) shows the user when the anchor head  29  is fully deployed. 
         [0051]    When the anchor head  29  has been fully deployed against the fascial tissue, the introducer  2  may be extracted from the muscle layer as depicted in  FIG. 19(   e ), as the deployment device maintains the desired tensile force on the filament or suture  14 . Retracting the introducer  2  from the inside of the abdominal wall leaves the tail end of the filament  14  visible in the abdomen as depicted in  FIG. 19(   f ). The end of the filament  14  must then be secured with a retainer, such as a suture clip  15  to secure the mesh  21 . In accordance with a preferred embodiment, the deployment device is provided with a means for determining, with a high degree of certainty, when the introducer  2  has penetrated the fascial layer  31 . This can be accomplished in a variety of manners. For example, electrical impedance measurement, mechanical impedance measurement and optical detection may be used for accomplishing this task. Either way, the sensing means preferably includes a sensor  22  that is located on or next to the introducer cutting surface  5 . Differences in the physical (e.g., optical and/or electrical) properties of muscle and adipose tissue may be used to sense the transition from one tissue to the other while the introducer  2  penetrates the fascia between these two tissue layers. Impedance measurement is believed to be a simple and effective method of distinguishing muscle tissue from adipose tissue in vivo. Optical detection may also be used in lieu of or as a compliment to the electrical impedance measurement. 
         [0052]    For purposes of illustration and not limitation, as embodied herein, the electrical impedance sensor system can be comprised of two or more electrical contacts that are biocompatible and made of an electrically conductive material. As depicted in  FIG. 15 , these contacts  23  are preferably positioned proximate the distal end of the introducer  2 . Even more preferably, these contacts are flush with the outer curved surface of the introducer  2 . As depicted, each contact  23  is electrically insulated from the other when the introducer is outside of the body. The contacts  23  become electrically connected, however, when the introducer is immersed in a conductive substance, such as living tissue rich with fluid. As is further depicted, a wire or other conductor  24  for each contact is embedded within the introducer  2 , and runs through the introducer  2  along the length of the barrel  1 . As depicted, the wires  24  operably electrically connect the contacts  23  to an impedance measurement circuit  25  in the delivery device housing  7 . For example, a Wheatstone bridge or other resistance-measurement circuit may be employed for circuit  25 . Circuit  25  is preferably connected to a display device that clearly shows the user either a direct view of the measured impedance or, for clarity, the result of a mapping from said impedance to another scale. 
         [0053]    This display may be implemented as a dial indicator, as depicted in  FIG. 17 , with a gradient and/or threshold sensing level  34 , a light or series of lights, as seen in  FIG. 18 , or other similar graphical user interface. The gauge implementation depicted in  FIG. 17  includes a gauge pointer  43  and a gauge face  41 . As depicted, the gauge face is divided into at least three sections, including: the indication range for muscle tissue  42   a , the indication range for the transition zone  42   b , and the indication range for adipose tissue  42   c . The threshold sensing level  34  displays the point at which the device senses that the cutting surface  5  is at the desired point of deployment, immediately outside the facial tissue layer  31 . The light indicator depicted in  FIG. 18  may include an indicator face  44 , an adipose tissue indicator light  45 , a transition indicator light  46 , and a muscle indicator light  47 . When the sensor  22  detects the presence of a tissue, the result of this detection is displayed by either lighting the corresponding light on the indicator, in the case of the light indicator of  FIG. 18 , or moving the gauge pointer  43  to the corresponding indication range, in the case of the gauge display of  FIG. 17 . The impedance may be measured at any frequency, but certain frequencies may be selected as they are more sensitive to a change from muscle to adipose tissue and vice versa. 
         [0054]    For purposes of further illustration, the optical sensor may include one or more light sources  35  as depicted in  FIG. 14 . The light source or sources may be located, for example, inside the housing  7 , immediately proximal to the base of the barrel  6 . The light source optical fiber  26  is preferably a thin optical fiber disposed along (or inside of) the wall of the introducer  2  in the axial direction of the barrel  1 . The source fiber  26  preferably originates at the base of the barrel  6  and terminates in the source fiber terminator  39  located at the introducer&#39;s cutting surface  5 , as depicted in  FIG. 16 . A second optical fiber used for detection  27  is preferably disposed parallel to the source fiber  26 , along the curvature of the cross-section of the barrel  1 , as depicted in  FIG. 14 . The detector fiber  27  also spans the distance from the base of the barrel  6  to the cutting surface  5 . The distal end of the detector fiber  27  also terminates at the cutting surface  5  of the introducer  2 . The source fiber terminator  39  and the detector fiber  40  may include small pieces of plastic, glass, or other translucent, biocompatible material that provides a clear optical interface. The end of the detector fiber  27  within base of the barrel  6  preferably feeds into a photoresistor  28 . The photoresistor  28  is positioned next to the light source  35  at the base of the barrel  6 . In this embodiment, light from the source must be transmitted through source fiber  26 , where it is scattered and filtered by the tissue at  5 , before being transmitted back through the detector fiber  27  to the photoresistor  28 . Circuit  36  may be used to measure the output of the photoresistor  28  at a given frequency. An indicator on the surgeon-interface casing  7  may directly display the apparent color of the tissue at the cutting surface  5 . Alternatively, the circuit  25  may include a mapping or conversion from the apparent tissue color to the probable tissue type at the cutting surface  5 . The result of this mapping may be displayed on an indication mechanism, as shown in  FIGS. 17 and 18 . An analog display, such as seen in  FIG. 17 , may include a threshold value  34 , which indicates the apparent transition from muscle tissue to adipose tissue. 
         [0055]    For purposes of further illustration, and not limitation, a second representative embodiment of an anchoring head  129  is depicted in  FIG. 21 . The embodiment of anchoring head  129  of  FIG. 21  is essentially identical to that of  FIG. 2(   a ), with one important difference. Specifically, the legs of top section  10  include extended portions  103  that provide the legs with a longer effective length to help orient the legs during deployment, and to prevent them from moving toward or away from each other when viewed from above. Specifically, the extended portions  103  tend to interact with tissue, making it more difficult for the legs to rotate about the longitudinal axis Y. As is evident, the legs associated with the top section  10  are longer than the legs of the bottom section  11 , which is also generally preferred to maintain desirable operation of the anchor head. 
         [0056]    The methods and systems of the present invention, as described above and shown in the drawings, provide for a surgical fastener and associated delivery system with superior properties. It will be apparent to those skilled in the art that various modifications and variations can be made in the device and method of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention include modifications and variations that are within the scope of the appended claims and their equivalents.