Abstract:
A method of manufacturing a surgical apparatus may include fabricating an anvil that includes an insert composed of a first material, the insert located within a cavity in a body composed of a second material, where the first material and the second material have different properties.

Description:
[0001]    This application is a divisional of U.S. patent application Ser. No. 12/489,355, filed on Jun. 22, 2009, which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention generally relates to surgical staplers and stapling. 
       BACKGROUND 
       [0003]    Referring to  FIG. 1 , a surgical stapler  2  typically includes a staple holder  4  and an anvil  6 . The staple holder  4  and anvil  6  are configured to close together and clamp tissue therebetween. After clamping, the staple holder  4  deploys a plurality of staples into that tissue. A challenge faced by most surgical staplers  2  is beam deflection. When the surgical stapler  2  clamps tissue that is sufficiently thick and/or tough, the distal end of the anvil  6  may not close completely relative to the staple holder  4 . Instead, the distal end of the anvil  6  may bend away from the staple holder  4 , because more force is required to compress the tissue than to cause the distal end of the anvil  6  to bend. Many attempts have been made to solve this problem. Some surgical staplers  2  utilize an “I-beam” mechanism, where the upper and lower portions of the I-beam each slide in a corresponding channel in the staple holder  4  and anvil  6 . However, the I-beam takes up space in the surgical stapler  2 , limits cutting and stapling operations to being performed by motion in the distal direction, and adds to the part count. Other surgical staplers  2  have been proposed that utilize exotic, highly-stiff materials to reduce or eliminate beam deflection. Stiffness is the force required to produce a unit deflection of a structure, and is related to the elastic modulus of the material from which the structure is fabricated. Strength is the ability of a structure to resist loads. However, it is a truism of material science that stiff, high-modulus materials are not high-strength materials, with the result that such materials are not practical for fabrication of an anvil  6 . 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a side view of a surgical stapler. 
           [0005]      FIG. 2  is a cross-section side view of an exemplary anvil. 
           [0006]      FIG. 3  is a cross-section end view of the anvil of  FIG. 2 . 
           [0007]      FIG. 4  is a cross-section end view of another exemplary anvil. 
           [0008]      FIG. 5  is a cross-section end view of another exemplary anvil. 
       
    
    
       [0009]    The use of the same reference symbols in different figures indicates similar or identical items. 
       DETAILED DESCRIPTION 
       [0010]    U.S. Patent Application Publication No. 2009/0065552, published on Mar. 12, 2009 (the “Endocutter Document”), is hereby incorporated by reference herein in its entirety. The Endocutter Document describes a surgical stapler  2  having a staple holder  4  and an anvil  6 . The anvil  6  described in this document may be used in place of the anvil  6  described in the Endocutter Document, or in place of a convention anvil in any suitable surgical stapler  2 . 
         [0011]    Referring to  FIGS. 2-3 , an insert  8  is held within the body  10  of the anvil  6 . That is, the body  10  is the part of the anvil  6  that receives the insert  8 . The insert  8  may have any cross-sectional shape, such as circular, oval, rectangular, square, or any other suitable shape. The cross-sectional shape of the insert  8  may be constant, or may vary, along the length of that insert  8 . The insert  8  may extend along part, or all, of the body  10  of the anvil  6 . If the insert  8  extends along only part of the body  10  of the anvil  6 , the insert  8  may be located at any suitable longitudinal position within the body  10  of the anvil  6 . Advantageously, the insert  8  is stiffer than the body  10 , and the body  10  is stronger than the insert  8 . The insert  8  may be any high-modulus material, such as, for example, tungsten carbide. However, the insert  8  may be a different ceramic, metal, or any other suitable high-modulus material. The body  10  may be any high-strength material, such as, for example, 17-4 PH stainless steel. However, the body  10  may be ceramic, a different metal, or any other suitable high-strength material. Numerical analysis indicates that the use of a tungsten carbide insert  8  in conjunction with a 17-4 PH stainless steel body  10  results in an anvil  6  approximately three times stiffer than an anvil  6  composed of 17-4 PH stainless steel alone. The combination of a high-modulus insert  8  and a high-strength body  10  results in an anvil  6  that is stronger than the insert  8  alone could be, and stiffer than the body  10  alone could be. Alternately, the insert  8  may be a high-strength material, and the body  10  may be a high-modulus material. For the purposes of this document, “high-modulus” of the insert  8  or body  10  refers to a material having a higher modulus than the material from which the other is fabricated. Similarly, “high-strength” of the insert  8  or body  10  refers to a material having a higher strength than the material from which the other is fabricated. 
         [0012]    The insert  8  and body  10  may be fabricated in any suitable manner. As one example, the insert  8  and the body  10  may be fabricated separately, and then the insert  8  may be placed into a corresponding cavity  12  within the body  10 . The insert  8  may be held in place by a pressure or interference fit, by adhesive, by welding, by pinning, or by any other method, mechanism and/or structure. As another example, the body  10  may be insert-molded about the insert  8 , or vice versa. Metal injection molding may be used to fabricate the body  10  about the insert  8 , or to fabricate the insert  8  within the cavity  12  defined in the body  10 . As another example, the body  10  may be cast about the insert  8 . As another example, the insert  8  may be cast in place within the cavity  12 . 
         [0013]    Referring also to  FIG. 4 , a different exemplary anvil  6  may include two or more inserts  8   a ,  8   b  held within the cavity in the body  10 . The inserts  8   a ,  8   b  may have any suitable cross-sectional shape. For example, each insert  8   a ,  8   b  may have a generally rectangular cross-sectional shape, where the rectangle is wider than it is tall. The inserts  8   a ,  8   b  may have substantially the same cross-sectional area and shape as one another, or may be shaped and/or sized differently from one another. For example, one of the inserts  8   a ,  8   b  may be thicker than the other. The inserts  8   a ,  8   b  each may extend substantially the same length longitudinally, and/or may be located in substantially the same longitudinal position in the anvil  6 . Alternately, at least one insert  8   a ,  8   b  may be shorter than another, and/or may be located in a different longitudinal position in the anvil  6 . One insert  8   a  may be fabricated from a high-strength material, and another insert  8   b  may be fabricated from a high-modulus material; such inserts  8   a ,  8   b  may be stacked relative to each other in any suitable order. If so, the body  10  may be fabricated from plastic or other material, where the anvil  6  relies on the inserts  8   a ,  8   b  for both strength or stiffness, or may be fabricated from any other material, where the anvil  6  does not rely entirely on the inserts  8   a ,  8   b  to provide both strength and stiffness. Alternately, each insert  8   a ,  8   b  may be fabricated from a high-strength material and the body  10  may be fabricated from a high-modulus material, or vice versa. 
         [0014]    Optionally, an upper insert  8   a  may be fabricated from a material that is stronger in compression than in tension, and a lower insert  8   b  may be fabricated from a material that is stronger in tension than compression. The upper insert  8   a  is further from the staple holder  4  than the lower insert  8   b . The use of terms such as “upper”, “lower” and “upwards” merely refers to the orientation of figures on the page for clarity and brevity, and does not limit the arrangement of the staple holder  4  and anvil  6 , nor the orientation of the anvil  6  in use. In this way, as the anvil  6  and staple holder  4 , the tendency of the distal end of the anvil  6  to bend upward away from the staple holder  4  is resisted both by the tensile strength of the lower insert  8   b  and the ability of the upper insert  8   a  to withstand compression. Typically, high modulus materials are stronger in compression than in tension, so in such a configuration the upper insert  8   a  may be fabricated from a high-modulus material and the lower insert  8   b  may be fabricated from a high-strength material. 
         [0015]    Referring to  FIG. 5 , a different exemplary anvil  6  may be fabricated from two separate, stacked layers  14   a ,  14   b . In such a configuration, an insert  8  may not be utilized. However, an insert  8  may be provided in conjunction with the two layers  14   a ,  14   b  if desired; in such a configuration, the layers  14   a ,  14   b  may form the body  10  of the anvil  6 , and the insert  8  is received into the cavity  12  of the body  10 . The layers  14   a ,  14   b  may be fabricated from different materials and stacked in any order. As one example, an upper layer  14   a  may be fabricated from a high modulus material such as tungsten carbide, and a lower layer  14   b  may be fabricated from a high-strength material such as 17-4 PH stainless steel. As another example, the upper layer  14   a  may be fabricated from a high-strength material and the lower layer  14   b  may be fabricated from a high modulus material. The layers  14   a ,  14   b  may be fixed to one another to form a rigid anvil  6 , and such fixation may be accomplished in any suitable manner, such as by adhesive, by welding, by pinning, by insert molding, or by metal injection molding. Optionally, one layer  14  may include one or more apertures (not shown) defined therein, and the other layer  14  may include one or more projections (not shown) configured to be received in those apertures. Such a configuration may facilitate the connection of the layers  14  to one another. The layers  14   a ,  14   b  each may extend along the entire length and width of the anvil  6 . Alternately, at least one layer  14  may extend along less than the entire length and/or width of the anvil  6 . If so, the other layer  14  may extend upward or downward to fill the remaining space. Alternately, one layer  14  may be composed of two or more separate pieces, each extending along less than all of the entire length and/or width of the anvil  6 . In this way, the material properties of a particular layer  14  may be fine-tuned. The layers  14   a ,  14   b  may each be substantially the same height. Alternately, one layer  14  may be thicker than the other, depending on the desired stiffness and/or strength of the anvil  6  as a whole. As another example, the anvil  6  may be fabricated from three or more layers  14 . 
         [0016]    While the invention has been described in detail, it will be apparent to one skilled in the art that various changes and modifications can be made and equivalents employed, without departing from the present invention. It is to be understood that the invention is not limited to the details of construction, the arrangements of components, and/or the method set forth in the above description or illustrated in the drawings. Statements in the abstract of this document, and any summary statements in this document, are merely exemplary; they are not, and cannot be interpreted as, limiting the scope of the claims. Further, the figures are merely exemplary and not limiting. Topical headings and subheadings are for the convenience of the reader only. They should not and cannot be construed to have any substantive significance, meaning or interpretation, and should not and cannot be deemed to indicate that all of the information relating to any particular topic is to be found under or limited to any particular heading or subheading. Therefore, the invention is not to be restricted or limited except in accordance with the following claims and their legal equivalents.