Abstract:
A staple is provided having a backspan and a first and second legs extending distally from the backspan. Each of the first and second legs includes a bend dividing each leg into a traversing leg portion and a substantially linear clenching leg portion. A staple plate is positionable over the first and second legs between the backspan and the first and second clenching leg portions. An anvil assembly has first and second movable members which move toward to one another to engage outer surfaces of the first and second clenching leg portions. There is further disclosed a method of forming the staple through tissue.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a divisional application of and claims the benefit of and priority to U.S. patent application Ser. No. 12/486,819, filed on Jun. 18, 2009, the entire contents of which are incorporated herein by reference. 
     
    
       [0002]    BACKGROUND 
         [0003]    1. Technical Field 
         [0004]    The present disclosure relates to a surgical staple for use in surgical procedures. More particularly, the present disclosure relates to a surgical staple and a staple assembly configured to accommodate various thicknesses of tissue by assuming a box configuration upon formation through tissue. The present disclosure also relates to a method of stapling tissues of various thicknesses with a single, uniform size staple. 
         [0005]    2. Background Of Related Art 
         [0006]    During various surgical procedures it is often necessary to secure one or more tissue sections together or to secure auxiliary structures such as, for example, mesh, buttress material, etc. to tissue. This is typically accomplished by driving a conventional staple, having a backspan and a pair of legs extending from the backspan, through the tissue and/or through the auxiliary structure. Once the conventional staple has been driven through the tissue, the ends of the legs are engaged with an anvil of the type typically having a pair of arcuate anvil pockets. This engagement causes the ends of the legs to be bent or recurved back towards the tissue to secure the tissue sections together and/or to secure the auxiliary material to the tissue. These bent or recurved portions of the staple legs are the tissue clenching portions of the legs. 
         [0007]    When attempting to secure relatively thick sections of tissue together or auxiliary material to a relatively thick tissue section, the sizing of the conventional staple is critical to ensure sufficient leg lengths to traverse the tissue. Insufficient leg lengths will result in incomplete stapling of the tissue. 
         [0008]    Further, when attempting to secure relatively thin sections of tissue together, or auxiliary material to the relatively thin tissue section, the sizing of the conventional staple is selected to ensure that there is not an excess of leg length. Excess leg length may result in the clenching portions of the legs projecting substantially away from the tissue as well as causing the ends of the leg to recurve back into and penetrate the tissue. 
         [0009]    Therefore, it is desirable to provide a staple having a leg length sufficient for various tissue thicknesses expected to be encountered. It is further desirable to provide a box shaped staple capable of being formed such that the clenching portions of the legs lie parallel to and flush against the tissue to be secured. It is still further desirable to provide a box staple assembly incorporating a staple plate to increase the bearing area of the staple against the tissue and shield the tissue from the ends of the staple legs. 
       SUMMARY 
       [0010]    There is disclosed a box staple including a backspan and a first leg extending from the backspan. The first leg is divided into a first traversing leg portion and a first linear clenching leg portion by a first bend. A second leg also extends from the backspan and is divided into a second traversing leg portion and a second linear clenching leg portion by a second bend. At least one of the first and second linear clenching leg portions is oriented parallel to the backspan. In one embodiment, both the first and second linear clenching leg portions are oriented parallel to the backspan. 
         [0011]    At least one of the first and second traversing leg portions is oriented perpendicular to the backspan. In a specific embodiment, both the first and second traversing leg portions are oriented perpendicular to the backspan. 
         [0012]    In one embodiment, a combined length of the first and second clenching leg portions is less than an overall length of the backspan. In an alternative embodiment, the combined length of the first and second clenching leg portions is equal to an overall length of the backspan. In a specific embodiment, the combined length of the first and second clenching leg portions is greater than an overall length of the backspan. 
         [0013]    There is also disclosed a box staple assembly for use in tissue which generally includes a backspan and first and second legs extending from the backspan. The first leg is divided into a first traversing leg portion and a first linear clenching leg portion by a first bend. The second leg is also divided into a second traversing leg portion and a second linear clenching leg portion by a second bend. A staple plate is positioned on the first and second legs between the backspan and the first and second linear clenching leg portions. At least one of the first and second linear clenching leg portions is oriented parallel to the staple plate. 
         [0014]    The staple plate has first and second holes to receive the first and second traversing leg portions respectively. An overall length of the staple plate is greater than an overall length of the backspan and the distance between the first and second holes is substantially equal to the overall length of the backspan. 
         [0015]    There is also disclosed a method of forming a box staple through tissue including the step of providing a box staple of having a backspan, a first leg extending from the backspan and including a first bend zone located between the backspan and a first end of the first leg, and a second the leg extending from the backspan and including a second bend zone located between the backspan and a second end of the second leg. The first and second ends of the first and second legs are driven through a tissue section. The first leg is impacted in the first bend zone with a first angled portion of a first anvil to form a first bend within the first bend zone and dividing in the first bend zone into a first traversing leg portion and a first linear clenching leg portion. 
         [0016]    The method further includes the step of impacting the first linear clenching leg portion with a first finishing surface of the first anvil to orient the first linear clenching leg portion parallel to the backspan. 
         [0017]    The method further includes the step of impacting the second leg in the second bend zone with a second angled portion of a second anvil to form a second bend within the second bend zone and dividing the second bend zone into a second traversing leg portion and a second linear clenching leg portion. 
         [0018]    The second linear clenching leg portion is impacted with a second finishing surface of the second anvil to orient the second linear clenching leg portion parallel to the backspan. 
         [0019]    In one embodiment of the disclosed method, the first and second ends are driven through tissue such that the backspan engages an upper surface of the tissue. 
         [0020]    In a further embodiment of the disclosed method, a staple plate is positioned over the first and second legs and engages an underside of the tissue prior to the step of impacting the first leg in the first bend zone. 
         [0021]    In a particular embodiment, the first linear clenching leg portion is oriented parallel to the staple plate. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0022]    Embodiments of the presently disclosed box staple and box staple assembly are disclosed herein with reference to the drawings, wherein: 
           [0023]      FIG. 1  is a side view, partially shown in section, of one embodiment of a disclosed box staple formed through a pair of tissue sections; 
           [0024]      FIG. 2  is an end view taken along line  2 - 2  of  FIG. 1 ; 
           [0025]      FIG. 3  is a top view taken along line  3 - 3  of  FIG. 1 ; 
           [0026]      FIG. 4  is a bottom view taken along line  4 - 4  of  FIG. 1 ; 
           [0027]      FIG. 5  is a side view, partially shown in section, of the box staple of  FIG. 1 , inserted through the pair of relatively thick tissue sections, immediately prior to formation; 
           [0028]      FIG. 6  is a side view similar to  FIG. 5  during formation of the box staple through the pair of relatively thick tissue sections; 
           [0029]      FIG. 7  is a side view similar to  FIG. 6  after formation of the box staple through the pair of relatively thick tissue sections; 
           [0030]      FIG. 8  is perspective view of the fully formed box staple; 
           [0031]      FIG. 9  is a side view, partially shown in section, of the box staple formed through a pair of relatively thin tissue sections; 
           [0032]      FIG. 10  is a top view taken along line  10 - 10  of  FIG. 9 ; 
           [0033]      FIG. 11  is an end view taken along line  11 - 11  of  FIG. 9 ; 
           [0034]      FIG. 12  is a bottom view taken along line  12 - 12  of  FIG. 9 ; 
           [0035]      FIG. 13  is a side view, partially shown in section, of the box staple immediately prior to formation through the pair of relatively thin tissue sections; 
           [0036]      FIG. 14  is a side view similar to  FIG. 13  during formation of the box staple through the pair of relatively thin tissue sections; 
           [0037]      FIG. 15  is similar to  FIG. 14  after formation of the box staple through the pair of relatively thin tissue sections; 
           [0038]      FIG. 16  is a perspective view of a box staple assembly including a box staple and a staple plate; 
           [0039]      FIG. 17  is a side view, partially shown in section, of the box staple assembly formed through a pair of relatively thick tissue sections; 
           [0040]      FIG. 18  is an end view taken along line  18 - 18  of  FIG. 17 ; 
           [0041]      FIG. 19  is a top view taken along line  19 - 19  of  FIG. 17 ; 
           [0042]      FIG. 20  is a bottom view taken along line  20 - 20  of  FIG. 17 ; 
           [0043]      FIG. 21  is a side view, partially shown in section, of the box staple assembly immediately prior to formation through the pair of relatively thick tissue sections; 
           [0044]      FIG. 22  is a side view, similar to  FIG. 21 , during formation of the box staple assembly through the pair of relatively thick tissue sections; 
           [0045]      FIG. 23  is a side view, similar to  FIG. 22 , after formation of the box staple assembly through the pair of relatively thick tissue sections; 
           [0046]      FIG. 24  is side view, partially shown in section, of the box staple assembly formed through a pair of relatively thin tissue sections; 
           [0047]      FIG. 25  is a top view taken along line  25 - 25  of  FIG. 24 ; 
           [0048]      FIG. 26  is a bottom view taken along line  26 - 26  of  FIG. 24 ; 
           [0049]      FIG. 27  is an end view taken along line  27 - 27  of  FIG. 24 ; 
           [0050]      FIG. 28  is a side view, partially shown in section, of an alternate embodiment of a staple assembly including a staple and an arcuate staple plate formed through a pair of relatively thick tissue sections; and 
           [0051]      FIG. 29  is a side view, partially shown in section, of the staple assembly of  FIG. 28  formed through a pair of relatively thin tissue sections. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0052]    Embodiments of the presently disclosed box staple and box staple assembly will now be described in detail with reference to the drawings wherein like numerals designate identical or corresponding elements in each of the several views. As is common in the art, the term “proximal” refers to that part or component closer to the user or operator, i.e. surgeon or physician, while the term “distal” refers to that part or component further away from the user. 
         [0053]    Referring to  FIG. 1-4 , and initially to  FIG. 1 , there is disclosed an embodiment of a universal or box staple  10  for use in various thickness of tissues. Box staple  10  has the further advantage of providing uniform pressure against the underside of the tissues stapled as described in more detail hereinbelow. Box staple  10  generally includes a backspan  12  and first and second legs  14  and  16 , respectively, extending distally from backspan  12 . Specifically, a proximal end  18  of first leg  14  extends distally from a first end  20  of backspan  12  and a proximal end  22  of second leg  16  extends distally from a second end  24  of backspan  12 . First leg  14  terminates in a tissue penetrating distal tip  26  and second leg  16  terminates in a tissue penetrating distal tip  28 . 
         [0054]    Box staple  10  is formed from a length of material having a generally rectangular cross-section. Box staple  10  can be formed from any number of biocompatible materials such as, for example, stainless steel, titanium, various malleable plastic materials, various bio-absorbable materials etc. When formed from metallic materials such as stainless steel or titanium, box staple  10  can be formed by drawing and cutting a length of metallic wire, stamping box staple  10  from a sheet of metallic material, etc. Likewise, when box staple  10  is formed from a plastic or bio-absorbable material, box staple  10  can be formed by injection molding, carving box staple  10  from a block of plastic material, etc. 
         [0055]    As noted above, box staple  10  is designed for use in tissues of various thicknesses, such as, for example, relatively thick tissues A and B. In order to accommodate the various thickness tissues without excessive or insufficient compression of tissues A and B, first leg  14  has a first bend zone  30  which extends substantially between proximal end  18  and tissue penetrating distal tip  26  of first leg  14 . Depending upon the thickness of the tissues encountered, first leg  14  can be bent at any location within bend zone  30  to accommodate those tissues. This is facilitated by the use of a pair of driven anvils as described in more detail herein below. Second leg  16  also includes a second bend zone  32  which extends substantially between proximal end  22  and tissue penetrating distal tip  28  of second leg  16 . 
         [0056]    When box staple  10  is fully formed through relatively thick tissues A and B, backspan  12  provides uniform compression on an upper surface C of relatively thick tissue section A ( FIGS. 1 and 3 ). First leg  14  is formed with a first bend  34  in first transition zone  30  such that first leg  14  is divided into a first, substantially linear traversing leg portion  36  extending through relatively thick tissues A and B ( FIG. 1 ) and a first substantially linear clenching leg portion  38  lying flush with an underside D of relatively thick tissue section B ( FIGS. 1 and 4 ). It should be noted that, first bend  34  formed between first traversing leg portion  36  and first clenching leg portion  38  is a substantially sharp or abrupt 90° bend in contrast to the relatively gradually curving bends typically associated with prior art staples. Likewise, second leg  16  is formed with a second bend  40  in second bend zone  32  which divides second leg  16  into a second substantially linear traversing leg portion  42  extending through relatively thick tissue sections A and B ( FIGS. 1 and 2 ) and a second substantially linear clenching leg portion  44  lying flush with underside D of relatively thick tissue section B. ( FIGS. 1 and 4 ). Second bend  40  also forms a relatively sharp or abrupt 90° transition between second traversing leg portion  42  and second clenching like portion  44 . By maintaining first and second clenching leg portions  38  and  44  in a relatively linear or straight configuration against underside D of relatively thick tissue section B, first clenching leg portion  38  and second clenching leg portion  44  maintain a uniform compression against underside D without the associated pinching or tip penetration of underside D as is common with the use of conventional staples whose leg distal ends are typically formed into a recurved shape penetrating back into the tissue. 
         [0057]    As best shown in  FIG. 1 , when box staple  10  is formed through of relatively thick tissue sections A and B, the length L 1  of backspan  12  is greater than or equal to the combined lengths L 2  and L 3  of first and second linear clenching leg portions  38  and  44 , respectively. 
         [0058]    Referring now to  FIGS. 5-7 , and initially with respect to  FIG. 5 , the use and formation of box staple  10  with relatively thick tissue sections A and B will now be described. Initially, the dimensions of box staple  10  are chosen such that legs  14  and  16  have overall lengths L 4  and L 5  which are substantially greater than the anticipated combine thicknesses of any tissues to be encountered. Furthermore, each of the overall lengths L 4  and L 5  of first and second legs  14  and  16 , respectively, is greater than half the overall length L 1  of backspan  12 . This ensures sufficient leg length to traverse and secure both relatively thick and thin tissue sections. Box staple  10  is initially driven through relatively thick tissue sections A and B by engaging backspan  12  with a staple driver (not shown) thereby driving first and second tissue penetrating distal tips  26  and  28 , respectively, through tissue sections A and B. 
         [0059]    Referring to  FIG. 6 , thereafter, a pair of anvils, such as, for example, first and second driven anvils  50  and  52 , are driven laterally against first and second staple legs  14  and  16  to form box staple  10  through relatively thick tissue sections A and B. First and second driven anvils  50  and  52  generally include respective first and second angled surfaces  54  and  56  and respective first and second finishing surfaces  58  and  60 . First and second angled surfaces  54  and  56  are provided to initially impact or impinge against first and second legs  14  and  16  within the respective first and second bend zones  30  and  32  to initially create first and second bends  34  and  40 . This divides first bend zone  30  of first leg  14  into first traversing leg portion  36  and first linear clenching leg portion  38 . Similarly, this divides second bend zone  32  into second traversing leg portion  42  and second linear clenching leg portion  44 . 
         [0060]    Referring to  FIG. 7 , as first and second anvils  50  and  52  are driven to the final position, first and second linear clenching leg portions  38  and  44  engaged by relatively linear finishing surfaces  58  and  60  of driven anvils  50  and  52 , respectively such that first and second linear clenching leg portions  38  and  44  are brought flush into engagement with underside D of relatively thick tissue section B. As noted here in above, when box staple  10  is used in relatively thin tissue sections, the combined lengths L 2  and L 3  of first and second clenching leg portions  38  and  44 , respectively, are substantially less than or equal to the overall length L 1  of backspan  12 . 
         [0061]    Referring now to  FIGS. 8-12 , and initially with regard to  FIG. 8 , box staple  10  is illustrated in the configuration it assumes when used through a pair of relatively thin tissue sections. Specifically, when box staple  10  is formed through relatively thin tissue sections, each of the lengths L 2  and L 3  of respective first and second linear clenching leg portions  38  and  44  are greater than the overall length L 1  of backspan  12 . 
         [0062]    As shown in  FIG. 9 , first and second traversing leg portions  36  and  42  pass through thin tissue sections E and F. First and second the linear clenching leg portions  38  and  44  lie parallel to tissue section F. As best shown in  FIG. 10 , backspan  12  engages an upper surface G of tissue section E while first and second linear clenching leg portions  38  and  44  engaged an underside surface H of tissue G. 
         [0063]    As best shown in  FIGS. 8 ,  11  and  12 , the excess lengths of first and second clenching leg portions  38  and  44  are accommodated by allowing them to lie in parallel relation to each other against underside F of tissue H. Thus, box staple  10  functions as a universal staple suitable for use with both thick and thin tissue sections without risk of penetrating the tissue sections with first and second tissue penetrating distal tips  26  and  28  of respective first and second legs  14  and  16 . 
         [0064]    Referring now to  FIGS. 13-15 , in order to form box staple  10  through pair of relatively thin tissue sections E and F, box staple  10  is initially driven through tissue sections E and F. Thereafter, driven anvils  50  and  52  impact staple legs  14  and  16  to initially begin to bend staple legs  14  and  16 . As shown in  FIG. 14 , angled faces  54  and  56  of driven staples  50  and  52  initially form bends  34  and  40  to create respective first and second traversing leg portions  36  and  42  and first and second linear clenching leg portions  38  and  44 . Thereafter, with reference to  FIG. 15 , finishing surfaces  58  and  60  of driven anvils  50  and  52  engage first and second linear clenching leg portions  38  and  44  to form first and second linear clenching leg portions  38  and  44  against underside H of tissue F and, more importantly, parallel to backspan  12 . Thus, box staple  10  is particularly suited to use with relatively thin tissue sections such that first and second linear clenching leg portions  38  and  44  a lie flush against the tissue to be stapled. 
         [0065]    Referring now to  FIGS. 16-20 , and initially with regard to  FIG. 16  there is disclosed a box staple assembly  70  including box staple  10  and a pledget or staple plate  72 . Staple plate  72  increases the surface area engaging a tissue being stapled as well as protecting the tissue from engagement with staple legs  14  and  16  upon crimping of box staple  10  about tissue. Box staple  10  is as described herein above including backspan  12  and legs  14  and  16  extending from backspan  12 . 
         [0066]    Staple plate  72  is substantially rectangular having first and second holes  74  and  76  adjacent first and second ends  78  and  80 , respectively, of staple plate  72 . First and second holes  74  and  76  are configured to receive first and second legs  14  and  16 , of box staple  10 , therethrough. Staple plate  72  has an overall length L 4  which is greater than the length L 1  of backspan  12  ( FIG. 1 ). Additionally, the spacing or length L 5  between holes  74  and  76  is substantially identical to the length L 1  of backspan  12 . 
         [0067]    As best shown in  FIGS. 17 and 18 , box staple assembly  70  is provided to secure a pair of tissue sections, such as, for example, tissue sections I and J. Backspan  12  engages an upper surface K of tissue section I ( FIG. 19 ) while an upper surface  82  of staple plate  72  engages a lower surface L of tissue section J ( FIG. 20 ). 
         [0068]    Referring to  FIG. 20 , as noted herein above, staple plate  72  protects tissue section J from engagement with first and second clenching leg portions  38  and  44  of first and second legs  14  and  16 , respectively. Specifically, upon formation of staple  10  through tissue sections I and J, staple plate  72  is interposed between tissue section J and first and second clenching leg portions  38  and  44 . 
         [0069]    Referring to  FIGS. 21-23 , the use of box staple assembly  70  to secure a pair of relatively thick tissue sections I and J together will now be described. With reference to  FIG. 21 , initially, box staple  10  is driven by a staple driver (not shown) toward tissue sections I and J such that first and second legs  14  and  16  penetrate tissue sections I and J until backspan  12  engages upper surface K of tissue section I. Staple plate  72  is positioned against undersurface K of tissue section J and legs  14  and  16  are extended through holes  74  and  76  a staple plate  72 . This brings upper surface  82  of staple plate  72  into engagement with undersurface K of tissue section J. 
         [0070]    With reference to  FIGS. 21 and 22 , thereafter, first and second driven anvils  50  and  52  are moved inwardly toward first and second legs  14  and  16 . Upon engagement of first and second angled surfaces  54  and  56  with first and second legs  14  and  16 , first and second legs  14  and  16  are initially bent within respective bend zones  30  and  32  to form first and second bends  34  and  40  within first and second legs  14  and  16 . As noted here in above, first bend  34  divides first leg  14  into first traversing leg portion  36  and first linear clenching leg portion  36  while second bend  40  divides second legs  16  into second traversing leg portion  42  and second linear clenching leg portion  44 . Notably, the extension of first and second legs  14  and  16  through first and second holes  74  and  76  in staple plate  72  facilitate forming bends  74  and  76  at substantially right angles relative to first and second traversing leg portions  36  and  38  of first and second legs  14  and  16 , respectively. 
         [0071]    Finally, with reference to  FIG. 23 , engagement of first and second finishing surfaces  58  and  60  of the first and second driven anvils  50  and  52  with first and second linear clenching leg portions  38  and  44  serve to secure first and second linear clenching leg portions  38  and  44  against underside  84  of staple plate  72  thereby securing staple plate  84  against underside L of tissue section J. 
         [0072]    Referring now to  FIGS. 24-27 , the use of box staple assembly  70  to secure a pair of relatively thin tissue sections, such as, for example, tissue sections M and N will now be described. The method disclosed herein with respect to relatively thin tissue sections M and N is substantially identical to the method disclosed herein above with respect to relatively thick tissue sections I and J. Initially, with reference to  FIG. 24 , staple  10  is driven by a staple driver (not shown) such that first and second legs  14  and  16  are driven through tissue sections M and N until backspan  12  engages an upper surface O of tissue section M ( FIG. 25 ). First and second legs  14  and  16  are then inserted through holes  74  and  76  of staple plate  72 . Thereafter, first and second driven anvils  50  and  52  ( FIGS. 21-23 ) are moved to form first and second linear clenching leg portions  38  and  44  against underside  84  of staple plate  72  ( FIG. 26 ). 
         [0073]    As best shown in  FIGS. 26 and 27 , similar to that disclosed herein above with respect to box staple  10  in  FIGS. 11 and 12 , first and second linear clenching leg portions  38  and  44  are in a side-by-side and overlapping relation with respect to each other due to the excess lengths of legs  14  and  16  wine used through relatively thin tissue sections M and N. In this manner, the provision of box staple  10  having first and second legs  14  and  16  with overall lengths greater then at least the overall length of backspan  12  allows box staple  10  to function as a universal staple suitable for use with various thicknesses of tissue. As noted herein above, the provision of staple plate  72  provides additional surface bearing area against the tissue section while facilitating forming an abrupt  90 ° bend within first and second legs  14  and  16 . 
         [0074]    Referring now to  FIGS. 28 and 29 , while staple plate  72  has been disclosed for use with box staple  10 , staple plate  72  may be formed of a material which allows staple plate  72  to be used with a staple and  90  similar to box staple  10  in situations wherein staple  90  is formed with conventional anvils. As used herein, the term “conventional anvils” refers to those anvils having arcuate anvil pockets resulting in arcuate rather than linear clenching leg portions in the formed staple. 
         [0075]    For example, with reference to  FIG. 28 , staple  90  includes a backspan  92  having first and second legs  94  and  96  extending from backspan  92 . In use, staple  90  is driven through relatively thick tissue sections Q and R resulting in first and second traversing leg portions  98  and  100  extending through tissue sections Q and R while backspan  92  engages an upper surface S of tissue section Q. First and second legs  94  and  96  are extended through holes  74  and  76  in staple plate  72  and are clenched against staple plate  72  by arcuate anvil pockets formed in an anvil associated with a conventional stapler (not shown). 
         [0076]    Similarly, with reference to  FIG. 29 , when used in conjunction with relatively thin tissue sections U and V, backspan  92  engages an upper surface W of tissue section U while traversing leg portions  98  and  100  extending through tissue sections U and V. Staple plate  72  bears against an undersurface X of tissue section V. First and second linear clenching leg portions  102  and  104  of first and second legs  94  and  96  are formed into a roughly arcuate overlapping relation due to the excess length of legs  94  and  96 . 
         [0077]    It will be understood that various modifications may be made to the embodiments disclosed herein. For example, the legs of the disclosed box staple maybe heat treated at specific points to facilitate the formation of the abrupt 90° bend between the traversing portion of the leg and the linear clenching portion of the leg. Further, alternative embodiments of anvils may be provided to form the substantially right angle within their respective legs. Additionally, the disclosed box staple may be formed from any shape memory alloy such that the right angle between the traversing leg portion and the linear clenching leg portion is formed at a predetermined location along the length of the leg. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.