Abstract:
An embroidery process allowing for a three-dimensional shape to be embroidered in two dimensions, allowing for the cost effective and repeatable manufacturing required for use in surgically implanted medical devices.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The present application is a nonprovisional patent application claiming benefit under 35 U.S.C. §119(e) from U.S. Provisional Application Ser. No. 60/881,684, filed on Jan. 22, 2007, the entire contents of which are hereby expressly incorporated by reference into this disclosure as if set forth fully herein. 
    
    
     BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates to medical devices and methods generally aimed at surgical implants. In particular, the disclosed system and associated methods are related to a manner of creating surgical implants via embroidery. 
     II. Discussion of the Prior Art 
     Embroidered structures are created on substrates. Some substrates are designed to stay in place with the embroidered structure while other substrates are removed at the end of the embroidery process. All of the embroidered structures discussed below are created on removable substrates, specifically ones removed through processes of dissolution. 
     On a dissolvable substrate, a plurality of parallel, stationary backing threads are placed and secured on one surface of a dissolvable substrate, called the backing surface. On the opposing surface of the substrate, called the stitching surface, is a plurality of stitching threads with one-to-one correspondence to the backing threads. Stitching may be done between one pair of threads at a time or in simultaneous multiplicity, as is described below. 
     The plurality of stitching threads from the stitching surface are passed through openings created in the dissolvable substrate by the passing of each individual thread to the backing surface. Each stitching thread is then looped over its corresponding backing thread, in essence picking up the backing thread, forming a lock stitch. Once each stitching thread has picked up its corresponding backing thread, the plurality of stitching threads are passed from the backing surface to the stitching surface through the openings in the dissolvable substrate created during the passage to the backing surface. The lock stitches prevent the stitching threads from completely pulling back out of the openings created in the dissolvable substrate. The plurality of stitching threads is then moved to a new stitching site and the process repeats until all the backing threads are joined by lock stitches to the corresponding stitching threads, creating a plurality of thread pairs. 
     A plurality of thread pairs may be enclosed by one or more pluralities of enclosing thread pairs. To enclose a plurality of thread pairs, a plurality of enclosing backing threads are placed and secured on the backing surface of a dissolvable substrate already holding at least one plurality of thread pairs, such that the plurality of enclosing backing threads covers the previously stitched plurality of backing threads. A plurality of enclosing backing threads is usually not parallel with the previous plurality of backing and stitching threads. A plurality of enclosing stitching threads, with one-to-one correspondence to the plurality of enclosing backing threads, are then stitched to the plurality of enclosing backing threads by the stitching process described above. 
     When the enclosing backing threads are all joined to the enclosing stitching threads by lock stitches, a plurality of enclosing thread pairs has been formed. This process may be repeated by stitching even more pluralities of enclosing thread pairs over all the previously stitched thread pairs, such that the first plurality is enclosed by the second plurality, which is enclosed by a third plurality, which is enclosed by a fourth plurality, etc. This process produces stable embroidered structures which do not unstitch into a pile of threads when the dissolvable substrate is removed. 
     The process of dissolvable substrate removal is dependent upon the composition of the dissolvable substrate material. Substrate materials are chosen such that the dissolution process which removes the dissolvable substrate will minimally, if at all, affect the physical properties of the remaining embroidered structure. The embroidered structure remains intact despite the removal of the dissolvable substrate because each stitching thread is stitched to its corresponding backing thread and vice versa. The backing thread is enclosed in one or more pluralities of enclosing thread pairs, which provides structural support. The result of the stitching is the creation of a generally two dimensional embroidered structure. There are, however, applications where it would be advantageous to have a generally three-dimensional embroidered structure rather than a generally two-dimensional embroidered structure, but the processes by which three-dimensional embroidered structures may be formed have been complicated and not conducive to cost effective and repeatable mass production. 
     The first type of process for creating three-dimensional embroidered structures has been to build up the structural shape of the embroidered structure with layer upon layer of embroidered thread. The drawbacks to this technique are that it makes the embroidered structure thicker where the building up had been done. The building up only yields block-type structures and does not allow for the embroidering of curvatures. 
     A second process of manufacturing three-dimensional embroidered structures takes two or more generally flat embroidered structures and stitches them together such that they form a three-dimensional structure. While preserving the uniform thickness of the embroidered structures lost by the layering technique above and allowing for the simplicity of embroidering each flat section in two-dimensions, this process requires several stitching steps, that would typically be performed manually, which must be done three-dimensionally after the embroidering of the sections is completed. This process is costly, with repeatability concerns where the final results and dimensions will be subject to the skill and dexterity of the individual who performs the stitching. 
     A third known process creates a single, generally two-dimensional embroidered structure which may be folded such that the edge or edges of the structure meet and may be stitched together, again typically by a manual process, to form a three-dimensional structure. However, this process suffers from the same post-embroidering stitching steps in three-dimensions as the second process, and thus suffers from the same drawbacks. 
     The present invention is intended to deal with these and other limitations of creating three-dimensional embroidered structures cost effectively and repeatably. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a manufacturing process performed on a two-dimensional substrate which produces three-dimensional embroidered structures which may be produced in a cost effective, repeatable manner. 
     The two-dimensional substrate upon which the embroidery is to be manufactured is tensioned throughout the manufacturing process. Load bearing threads are laid down under tension on the substrate, further tensioning the substrate such that tension gradients are present and different positions on the substrate will be under different amounts of tension. A backing mesh in the general shape of a hexagon or other generally polygonal or non-polygonal shape is then manufactured over the load bearing threads on the substrate. The backing mesh may be manufactured using customary techniques of embroidery, or any other process which results in the backing mesh having qualities similar to those of normally embroidered structures. The effect of the load bearing threads and backing mesh being embroidered on the substrate, and the different tensions at different points on the substrate, cause the load bearing threads to be relationally shorter than the threads forming the backing mesh. When the substrate upon which the embroidered structure was manufactured is removed from the embroidered structure, the load bearing threads and backing mesh are no longer being externally tensioned, allowing the load bearing threads and backing mesh to relax. The relationally shorter load bearing threads relax more than the relationally longer backing mesh, and this difference in magnitude of relaxation results in the load bearing threads drawing the backing mesh inward, forcing the backing mesh into a three-dimensional shape having varying three-dimensional properties. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is a plan view of the load bearing threads and backing mesh of the embroidered structure on the tensioned substrate; 
         FIG. 2  is a cross-sectional view of the load bearing threads and backing mesh of the embroidered structure of  FIG. 1  after removal of the tensioned substrate; 
         FIG. 3   a  is a plan view of the load bearing threads and backing mesh of the embroidered structure according to an alternative embodiment of the present invention for single level application; 
         FIG. 3   b  is a plan view of the load bearing threads and backing mesh of the embroidered structure according to an alternative embodiment of the present invention for a multi-level application; 
         FIG. 4  is a cross-sectional view of the load bearing threads and backing mesh of the embroidered structure of  FIGS. 3   a - b;    
         FIG. 5   a  is a plan view of the load bearing threads and backing mesh of the embroidered structure according to an alternative embodiment of the present invention for a single level application; 
         FIG. 5   b  is a plan view of the load bearing threads and backing mesh of the embroidered structure according to an alternative embodiment of the present invention for a multi-level application; 
         FIG. 6  is a cross-sectional view of the load bearing threads and backing mesh of the embroidered structure of  FIGS. 5   a - b;    
         FIG. 7   a  is a plan view of the load bearing threads and backing mesh of the embroidered structure according to an alternative embodiment of the present invention for a single level application; 
         FIG. 7   b  is a plan view of the load bearing threads and backing mesh of the embroidered structure according to an alternative embodiment of the present invention for a multi-level application; and 
         FIG. 8  is a cross-sectional view of the load bearing threads and backing mesh of the embroidered structure of  FIGS. 7   a - b.    
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     An illustrative embodiment of the invention is described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. The process of creating three-dimensional embroidered structures through differential tensioning of a two-dimensional substrate upon which the embroidered structure is manufactured disclosed herein boasts a variety of inventive features and components that warrant patent protection, both individually and in combination. 
       FIG. 1  shows an embroidered structure  10  manufactured according to the present invention. A substrate  18  formed from acetate or any other material suitable for use as a dissolvable substrate for embroidery is prepared by being placed under tension from its edges. Load bearing threads  12  are then laid down under tension on the tensioned substrate  18 , further tensioning the substrate  18  such that tension gradients are present and different positions on the substrate will be under different amounts of tension. The load bearing threads  12  may be formed from any suitable material for creating an embroidered structure, including but not limited to polyester, polypropylene, polyethylene, carbon fiber, glass, glass fiber, polyaramide, metal, copolymers, polylactic acid, polyglycolic acid, biodegradable fibers, silk, cellulosic and polycaprolactone, including mixtures of one or more of these materials including fibers made therefrom. Once the load bearing threads  12  are in place, a backing mesh  14  may be embroidered, woven or manufactured by any other customary process which results in the backing mesh having qualities similar to those of normally embroidered structures, around the load bearing threads  12 . The backing mesh  14  maybe be any suitable shape, including by not limited to generally hexagonal, polygonal or non-polygonal. The backing mesh  14  may be formed from the same or different materials as the load bearing threads  12 . The embroidering of load bearing threads  12  and backing mesh  14  on a substrate which is subject to tension in a gradient of positional dependence causes the load bearing threads  12  to be relationally shorter than the threads forming the backing mesh  14 . Surrounding structures may be engineered to form eyelets  16  or other formations to which the load bearing threads  12  may attach. 
     One exemplary embodiment of the present invention as shown in  FIG. 1  includes a backing mesh  14  that is generally hexagonal in shape. According to this embodiment, the backing mesh  14  includes at least one eyelet  16  in each of the six vertices. The load bearing threads  12  are positioned on the backing mesh  14  such that the load bearing threads  12  form at least three thread paths  22 , with each thread path  22  encircling at least two eyelets  16  that are located directly opposite of each other on the backing mesh  14 . Each thread path  22  bisects the hexagonal backing mesh  14  between two vertices. Further, each thread path  22  bisects each of the other two thread paths  22 . The load bearing threads  12  may be positioned along these thread paths  22  at least once and possibly multiple times. Lock stitching and layering will prevent the device from loosening or unraveling. 
       FIG. 2  shows a cross-section of the embroidered structure  10  after removal of the tensioned substrate  18 . When the substrate  18  is dissolved or otherwise removed from the embroidered structure  10 , the substrate tension dissipates. In the absence of the tension provided by the substrate  18 , both the load bearing threads  12  and backing mesh  14  relax. The relationally shorter load bearing threads  12  relax more than the relationally longer backing mesh  14 , and this difference in magnitude of relaxation results in the load bearing threads  12  drawing the backing mesh  14  inward, forcing the backing mesh  14  into a three-dimensional shape. 
       FIGS. 3   a - b  illustrate an alternative embodiment of the present invention which may, by way of example only, be used as an anterior cervical plate to prevent egress of a cervical implant post-implantation. The embroidered structure  10  of the present invention serves as a buttress to keep the cervical implant inside the disc space after the cervical implant has been placed. The embodiment of  FIG. 3   a  includes a backing mesh  14  that is generally rectangular in shape with mild concave curvatures expending along each side between successive eyelets  16 . According to this embodiment, the backing mesh  14  includes a pair of eyelets  16  on each of the upper portion  32  and lower portion  34  of the backing mesh  14 . The load bearing threads  12  are positioned on the backing mesh  14  such that the load bearing threads  12  form at least two thread paths  22 ,  24 , with each path encircling at least two eyelets  16  that are located directly opposite of each other on the backing mesh  14 . Each individual thread path  22 ,  24  bisects the rectangular backing mesh  14  between two vertices. Further, each thread path  22 ,  24  bisects the other thread path  22 . 
       FIG. 3   b  illustrates the embodiment of the present invention as shown in  FIG. 3   a  adapted, by way of example only, for use as a multi-level anterior cervical plate. According to this embodiment, the backing mesh  14  includes a pair of eyelets  16  in each of the upper and lower portions  32 ,  34  and at least one pair of eyelets  16  positioned between the upper and lower portions of the backing mesh  14  with mild concave curvatures expending along each side between successive eyelets  16 . The load bearing threads  12  are positioned on the backing mesh  14  in the same pattern as drawn in  FIG. 3   a , encircling diagonal pairs of eyelets  16  located on the lower portion of the backing mesh  14  and the pair of eyelets  16  located in the middle of the backing mesh  16 . The same pattern is repeated around the middle pair of eyelets  16  and the pair of eyelets  16  located on the upper portion of the backing mesh  14 .  FIG. 4  shows a cross-section of the embroidered structure  10  according to the embodiments drawn in  FIGS. 3   a - b  after removal of the tensioned substrate  18  resulting in a three-dimensional shape. 
       FIGS. 5   a - b  illustrate another alternative embodiment of the present invention which, by way of example only, may be used as an anterior cervical plate to prevent egress of a cervical implant post-implantation. The embodiment drawn in  FIG. 5   a  includes a backing mesh  14  that is generally rectangular in shape with mild concave curvatures expending along each side between successive eyelets  16 . According to this embodiment, the backing mesh  14  includes a pair of eyelets  16  in each of the upper portion  32  and lower portion  34  of the backing mesh  14 . The load bearing threads  12  are positioned on the backing mesh  14  such that the load bearing threads  12  form a thread path  22 . The thread path  22  loops around the medial sides of the upper left eyelet  16  and the lower left eyelet  16 . The thread path  22  then loops around the lateral side of the lower left eyelet  16 , and then extends to and around the lateral side of the upper right eyelet  16 . The thread path  22  then loops around the medial sides of the upper right eyelet  16  and the lower right eyelet  16 . The thread path  22  continues around the lateral side of the lower right eyelet  16  and then extends to and around the lateral side of the upper left eyelet  16 . 
       FIG. 5   b  illustrates the embodiment of the present invention as drawn in  FIG. 5   a  adapted, by way of example only, for use as a multi-level anterior cervical plate. According to this embodiment, the backing mesh  14  includes a pair of eyelets  16  in each of the upper portion  32 , middle portion  36  and lower portion  34  of the backing mesh  14  with mild concave curvatures expending along each side between successive eyelets  16 . The load bearing threads  12  are positioned on the backing mesh  14  such that the load bearing threads  12  form at least two thread paths  22 ,  24 . The first thread path  22  extends around the medial sides of the upper left eyelet  16 , middle left eyelet  16  and the lower left eyelet  16 , and then loops around the lateral side of the lower left eyelet  16 . The thread path  24  then continues to loop around the lateral side of the middle right eyelet  16 , and then extends to and around the lateral side of the upper left eyelet  16 . The second thread path  24  extends along the medial sides of the upper right eyelet  16 , middle right eyelet  16  and lower right eyelet  16 , and loops around the lateral side of the lower right eyelet  16 . The thread path  24  then loops around the lateral side of the middle left eyelet  16  and then extends to and loops around the lateral side of the upper right eyelet  16 .  FIG. 6  shows a cross-section of the embroidered structure  10  according to the embodiments drawn in  FIGS. 5   a - b  after removal of the tensioned substrate  18 . 
       FIGS. 7   a - b  illustrate yet another alternative embodiment of the present invention which, by way of example only, may be used as an anterior cervical plate to prevent egress of a cervical implant post-implantation. The embodiment drawn in  FIG. 7   a  includes a backing mesh  14  that is generally rectangular in shape with mild concave curvatures expending along each side between successive eyelets  16 . According to this embodiment, the backing mesh  14  includes a pair of eyelets  16  in each of the upper portion  32  and lower portion  34  of the backing mesh  14 . The load bearing threads  12  are positioned on the backing mesh  14  such that the load bearing threads  12  form at least three thread paths  22 ,  24 ,  26 . The first thread path  22  extends along the medial sides of the upper left eyelet  16  and the lower left eyelet  16 . The thread  22  then loops around the lateral side of the lower left eyelet  16 , and then extends to and around the lateral side of the lower right eyelet  16 . The thread  22  then loops around the medial sides of the lower right eyelet  16  and the upper right eyelet  16 . The thread path  22  continues around the lateral side of the upper right eyelet  16  and then extends to and around the lateral side of the upper left eyelet  16 . 
     The second and third thread paths  24 ,  26  encircle at least two eyelets  16  that are located diagonally opposite of each other on the backing mesh  14 . Each of the second and third thread paths  24 ,  26  bisects the rectangular backing mesh  14  between two vertices. Further, each of the second and third thread paths  24 ,  26  bisects the other individual thread path  24 ,  26 . 
       FIG. 7   b  illustrates the embodiment of the present invention as drawn in  FIG. 7   a  adapted, by way of example only, for use as a multi-level anterior cervical plate. According to this embodiment, the backing mesh  14  includes a pair of eyelets  16  in each of the upper portion  32 , middle portion  36  and lower portion  34  of the backing mesh  14  with mild concave curvatures expending along each side between successive eyelets  16 . The load bearing threads  12  are positioned on the backing mesh  14  such that the load bearing threads  12  form at least five individual thread paths  22 ,  24 ,  26 ,  28 ,  30 . The first thread path  22  extends around the medial sides of the upper left eyelet  16 , middle left eyelet  16  and the lower left eyelet  16 , and then loops around the lateral side of the lower left eyelet  16 . The thread  22  then extends to and loops around the lateral side of the lower right eyelet  16 , and then extends along the medial sides of the lower right, middle right and upper right eyelets  16 . The thread  22  then loops around the upper right eyelet  16 , and then extends to and loops around the upper left eyelet  16 . 
     The second thread path  24  encircles the lower right and the middle left eyelets  16 . The third thread path  26  encircles the lower left and middle right eyelets  16 . The second and third thread paths  24 ,  26  bisect each other. The fourth thread path  28  encircles the middle right and the upper left eyelets  16 . The fifth thread path  30  encircles the middle left and upper right eyelets  16 . The fourth and fifth thread paths  28 ,  30  bisect each other.  FIG. 8  shows a cross-section of the embroidered structure  10  according to the embodiments drawn in  FIGS. 7   a - b  after removal of the tensioned substrate  18 . 
     The tension shaping of a generally two-dimensional embroidered structure into a three-dimensional structure allows for embroidered structures to be manufactured using automated devices such as commercially available embroidery machines, making the production of such embroidered structures cost effective and repeatable, as the production does not require hand stitching. The tension shaped embroidered structures are pulled into three-dimensional shapes and not built up out of extra material. This allows for the tension shaped embroidered structures to be produced in various three-dimensional shapes instead of only generally block shapes. The tension shaped embroidered structures are comparatively thin, retaining their flexibility compared to embroidered structures produced by the building up of additional material. 
     While the invention is susceptible to various modifications and alternative forms, a specific embodiment thereof has been shown by way of example in the drawings and is herein described in detail. It should be understood, however, that the description herein of a specific embodiment is not intended to limit the invention to the particular form disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined herein.