Patent Publication Number: US-2013231699-A1

Title: Locking suture

Description:
CROSS REFERENCE TO RELATED U.S. APPLICATION 
     This application claims priority to U.S. Provisional Application No. 61/600,734, filed on Feb. 20, 2012, the teachings and entire disclosure of which are fully incorporated herein by reference. 
    
    
     BACKGROUND 
     Endoscopic surgery refers to surgical procedures performed through small incisions, or natural body openings. Various forms of endoscopic surgery include arthroscopy, laparoscopy, thoracoscopy, cystoscopy rhinoscopy, otoscopy, and microsurgery. Incisions associated with endoscopic surgery are generally small, and puncture-like. In some cases, one or more puncture wounds are made through skin and subcutaneous tissues using a trocar, which has a shaft with at least one pointed end and may be surrounded by a sleeve-like cannula. A surgeon then withdraws the trocar and inserts medical instruments through the cannula to conduct the surgery. The puncture-like incision(s) thus serve as an entry point to the surgical site. The size of the incision depends on the nature of the surgery, but may typically range from about 3 mm (millimeters) to about 10 mm. 
     Arthroscopy is one type of endoscopic surgery. In some kinds of arthroscopy, surgeons repair damaged or torn connective tissue (e.g., ligaments) by sewing one piece of tissue to another with sutures, allowing the tissue to heal without pulling apart. In other kinds, surgeons reattach tissue to surrounding bone using sutures, and, if indicated, additional devices, such as implantable anchors or other fixation members. 
     In some kinds of arthroscopy, one end of a suture is securely attached, or mounted, to a conventional surgical needle having a shank-like body member, which is formed from conventional materials, such as a metal or a metal alloy. A surgical needle typically contains a sharp point at one end for advancing into and through tissue, and a mounting apparatus at the opposite end. Various techniques for mounting a suture to a surgical needle are known and conventionally used, e.g., use of adhesives, heat shrinking, or simply threading a suture through an eyelet of the needle. For some uses, a suture and a surgical needle are combined as an unitary product. 
     Generally, sutures are formed from various materials as are known to persons of ordinary skill in the art, e.g., polyethylene, silk, catgut, chromic catgut, polyglycolic acid (PGA), polylactic acid (PLA), and polydioxanone (PDS), nylon, and polypropylene, which are mentioned here as non-limiting examples. Suture material sometimes is a monofilament material, while some sutures are formed from multi-stranded materials woven together, or braided. The core of a suture can be either hollow or solid. Some sutures are formed from bioabsorbable material, which is broken down over time and eventually eliminated from the body or absorbed by the tissues. Some sutures are formed from biocompatible material, meaning that a patient&#39;s body will generally tolerate the presence of the suture indefinitely. For some uses, a suture is coated with conventional materials to improve functional properties, such as durability, and the ease with which a suture passes through tissue as a function of reducing the friction at the tissue-suture interface. 
     In use, sufficient force is applied to a surgical needle to cause the sharp point to move through or around bodily tissue in a particular direction chosen by a surgeon, i.e., “antegrade” movement. The shank-like body member and attached suture follow the needle, which threads the suture through bodily tissue in a pattern determined by the surgeon. Once the pattern is complete, it is desirable for the suture to hold its position. This can be accomplished by establishing a friction force that resists or limits suture movement relative to tissue, thereby creating tension to hold the tissue in the desired position. 
     Forming knots in a suture or series of sutures is a traditional method for creating the friction force. However, for arthroscopy and other forms of endoscopic surgery performed through tiny openings, often the surgeon cannot visualize the tissue at the surgical site without the aid of cameras and similar viewing devices. Even if visualization is achieved, forming knots in such confined spaces is difficult, if not impractical. 
     Therefore, various knotless suturing techniques already exist. Some involve forming a slipknot or other closed loop at the trailing end of a suture, and then passing a portion (leading end) of the suture body through that loop. However, such techniques present various challenges and disadvantages, most notably the propensity of the suture body to undergo retrograde movement (i.e., in the opposite direction of antegrade) over time, causing it to loosen. This tends to reduce tension in the suture, allowing repaired tissue to pull apart over time. Therefore, it is desirable to limit such retrograde movement. 
     Whether securing ligament to bone or approximating two ends of a torn ligament, as well as other forms of tissue repair, as a surgical needle is advanced through the tissue, the mounted suture follows. In this way, both enter and exit tissue in alternating fashion according to the desired pattern. Either while the pattern is progressing, or once completed, the term “approximation” refers to the act of bringing and maintaining a section of tissue in close proximity to something else, usually either another section of tissue or a piece of bone. Once approximated, it is desirable to hold that position. 
     This is particularly true given the forces at work on the tissues of a person&#39;s body, including repaired tissue. In a soft tissue repair, the ends that are approximated and then securely attached will tend to be pulled away from each other, through physical motion (e.g., throwing a ball in a person who has undergone shoulder arthroscopy), gravity (e.g., a Bankart lesion that involves the inferior glenohumeral ligament), and blunt impact (e.g., falling and landing on the surgical site). Thus, it is desirable for a suture to be strong enough, and also held in place securely enough, that it will remain in a substantially static position as the suture counteracts such forces over time. 
     The use of bone anchors is also part of conventional practice in arthroscopy. These are used to help securely hold tissue to bone. A surgeon bores a small hole into a bone and threads an anchor into the hole. With the anchor serving as a secure fixation point, the surgeon then threads a suture through an aperture on the anchor. 
     SUMMARY 
     A locking suture, as described and claimed herein, comprises at least a main branch, a leading end of which is of suitable size and dimension for passing through tissue when appropriate force in a desired direction is placed on the main branch, for example by attachment to a surgical needle that itself is passing through tissue; at least one suture locking braid fixably attached to the main branch, for resisting movement of the main branch in at least one direction; and an opening, positioned at or near a trailing end of the main branch, which may be formed integral to the main branch, for accommodating passage of a portion of the main branch and the at least one locking braid during antegrade movement of the main branch, but resisting retrograde passage of the at least one locking braid back through the suture opening. In some embodiments, the mechanical impediment is established by a physical constraint due to the size and dimension of suture eyelet  16  compared to the dimensions, size, length, and angle orientation of suture locking braid  18 , wherein the mechanical stress associated with the impediment causes locking braid  18  to deform. 
     The main branch has a leading end and a trailing end. In use, e.g., during an endoscopic surgical procedure, the leading end is the end that passes through tissue before the trailing end does. The leading end also passes through the opening, which is a suture eyelet in some embodiments. The suture eyelet is of suitable size and dimension to receive the leading end and a first segment of the main branch, as well as at least one of the suture locking braids. The number of locking braids that pass through the suture eyelet influences the amount of tension applied to the suture and the surrounding tissue being repaired. This allows the suture to be securely used for repairing and reattaching tissue in various kinds of procedures, e.g., endoscopy, without having to manually tie knots. In general, tension is proportional to the number of suture locking braids that pass through the eyelet during antegrade movement. In some alternative embodiments, a plurality of outer members spaced along the main suture branch pass through the suture eyelet during antegrade movement, but limit retrograde passage back through the suture eyelet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings and embodiments described herein are illustrative of multiple alternative structures, aspects, and features of the present embodiments, and they are not to be understood as limiting the scope of present embodiments. It will be further understood that the drawing figures described and provided herein are not to scale, and that the embodiments are not limited to the precise arrangements and instrumentalities shown. 
         FIG. 1  is a plan view of a locking suture, according to multiple embodiments and alternatives. 
         FIG. 2  is a plan view of a locking suture, according to multiple embodiments and alternatives, with a region (depicted by circle A) illustrated in more detail in  FIG. 3A . 
         FIG. 3A  is a perspective view of the region of  FIG. 2  indicated by the dotted circle, according to multiple embodiments and alternatives. 
         FIG. 3B  is a perspective view of a locking suture, according to multiple embodiments and alternatives. 
         FIG. 4  depicts tissue repair using a locking suture, according to multiple embodiments and alternatives. 
         FIG. 5  depicts a surgical repair, according to multiple embodiments and alternatives, also utilizing a suture anchor (not claimed). 
         FIG. 6  is a perspective view of a locking suture, according to multiple embodiments and alternatives. 
         FIG. 7  is a cross-sectional view of an outer member around a locking suture main branch, along the section I-I from  FIG. 6 , according to multiple embodiments and alternatives. 
         FIG. 8  is perspective view of a locking suture, according to multiple embodiments and alternatives. 
     
    
    
     MULTIPLE EMBODIMENTS AND ALTERNATIVES 
     Multiple embodiments and alternatives of a locking suture are described and taught herein. As illustrated in  FIG. 1 , a locking suture  5  comprises a main branch  10  of suture strand  8 , the suture strand and its main branch generally being formed from suture materials discussed above and through methods and techniques as are generally known in the art. In some embodiments, main branch  10  comprises an inner hollow core suture. Alternatively, main branch  10  has a solid core. 
     A first end of main branch  10  comprises leading end  12 . An opposite end of main branch  10  comprises trailing end  14 . In some embodiments, trailing end  14  includes suture eyelet  16 , having an opening through which a first segment of suture strand  8  is passed, beginning with leading end  12 . In  FIG. 2 , first segment is the main branch  10  and locking braids  18  (including  18   a ) shown between eyelet  16  and leading end  12 . In some embodiments, suture eyelet  16  is formed from plastic or other solid materials. 
     As also illustrated in  FIGS. 1-5 , in some embodiments, at least one suture locking braid  18  is attached to main branch  10 . In some embodiments, each of a plurality of suture locking braids  18  is fixably attached to main branch  10  by securely joining a main branch connecting end  27  (see  FIG. 3 ) of each suture locking braid  18  into the fibers of main branch  10 . In some embodiments, this is accomplished by weaving main branch connecting end  27  of a suture locking braid  18  into the inner hollow core of main branch  10 , through methods that are known to persons having ordinary skill in the art, sufficiently to prevent detachment of suture locking braid  18  from main branch  10  as both pass through suture eyelet  16  during antegrade movement. Alternatively, suture locking braid  18  is fixably attached to main branch  10  by other means, e.g., by thermally deforming (i.e., melting) or gluing end  27  of suture locking braid  18  to main branch  10 , again which means are known to persons having ordinary skill in the art. 
     As illustrated in  FIG. 3 , in some embodiments, each suture locking braid  18  is securely joined to main branch  10  at an acute angle. This biases each suture locking braid  18  to pass through suture eyelet  16  during antegrade movement  15 . It will be appreciated that, during retrograde movement, the acute angle formed by suture locking braid  18  and main branch  10  biases against passage through suture eyelet  16 . Preferably, suture locking braid  18  and main branch  10  form an angle of about 30° to about 45°. 
     Thus, during retrograde movement i.e., movement in a second direction—depicted by arrow  17 , when a suture locking braid  18  contacts suture eyelet  16  (i.e., a solid perimeter rim  19  at the outer edge of suture eyelet  16 ), braid  18  is mechanically impeded from passing through eyelet  16 . The mechanical impediment is established by a physical constraint due to the size and dimension of suture eyelet  16  compared to the size, length, and angle orientation of suture locking braid  18 . Upon sustained contact with the perimeter rim  19  of suture eyelet  16 , suture locking braid  18  experiences a mechanical impediment such that, through sustained contact with rim  19 , the suture locking braid becomes structurally deformed as seen in  FIG. 3B . This structural deformation effectively increases the breadth of suture locking braid  18 , including near its free end  29  (i.e., the end opposite main branch connecting end  27 ), and generally increases the surface area of suture locking braid  18  that contacts suture eyelet  16 . The mechanical impediment described here thus limits (i.e., substantially prevents) retrograde passage of suture locking braid  18  back through the suture eyelet. 
     In some embodiments, suture locking braids  18  are generally formed from the same or similar materials as main branch  10 . The spacing between suture locking braids  18  is generally variable. Spacing is influenced by various considerations, such as the diameter of main branch  10 , the type of tissue being repaired, and the range of tension (force per unit length) required to retain the position of the suture over time. For example, if the level of tension required varies over a relatively wide range, then more distance in the spacing between suture locking braids  18  will generally be acceptable, assuming all other factors are equal. However, if a more precise amount of tension is needed, then reduced spacing between suture locking braids  18  is desirable. This generally increases the number of suture locking braids  18  along main branch  10 , and increases the number of options for which suture locking braid will be the last one passed through suture eyelet  16 . 
     For example, a #2 suture is used for relatively small tissue repairs. In some embodiments, a locking suture  8  of similar size and dimensions as a standard #2 suture has suture locking braids  18  positioned approximately 2-5 mm apart. By comparison, a #8 suture is meant for larger tissue repairs, and optionally has suture locking braids  18  positioned about 5 mm to about 8 mm apart. It is not necessary, however, that spacing between each of suture locking braids  18  should be must be limited to this range, nor is uniform spacing of them required along main branch  10 . Rather, spacing of suture locking braids  18  is chosen according to multiple alternatives as selectably desired. 
       FIG. 2  illustrates a portion of main branch  10  beginning with leading end  12  having been passed through suture eyelet  16  for tissue (not shown in  FIG. 2 ) repair. Antegrade movement arrow  15  depicts a first direction traveled by leading end  12 , and retrograde movement arrow  17  (dashed arrow) depicts movement in a second direction generally opposite the first. Thus, locking suture  5 , according to multiple embodiments and alternatives as described and taught herein, resists such retrograde movement due to the mechanical impediment created by the engagement of, and sustained contact between, a suture locking braid  18   a  with rim  19  of suture eyelet  16 . The mechanical stress of this engagement causes locking braid  18   a  to deform. The change in shape of locking braid  18   a  through deformation (as shown in  FIG. 3B ) prevents its retrograde passage through eyelet  16 , and this prevents further movement of the main branch  10  in the retrograde direction as well. 
       FIG. 3A  illustrates a region as depicted by the dashed line circle shown in  FIG. 2 . A suture locking braid  18   a  is depicted as being positioned within this region, proximal to suture eyelet  16 . The determination about which suture locking braid  18  is positioned proximal to suture eyelet  16  depends on the length of main branch  10  passed through suture eyelet  16 . Further, while applicant&#39;s drawing figures are not to scale,  FIG. 3A  (among others) indicates the relative dimensions of main branch  10 , suture locking braids  18 , and suture eyelet  16 . In some embodiments, if suture eyelet  16  is circular or substantially circular, then its diameter is slightly greater than the diameter of main branch  10  plus the diameter of each suture locking braid  18 . These diameters are such that main branch  10  passes easily when it is passed through suture eyelet  16  by itself, but passage of main branch  10  combined with suture locking braid  18  makes for tighter passage. 
     As discussed herein, and shown in  FIG. 3 , each of suture locking braids  18  has a main branch connecting end  27  and a free end  29 . In general, connecting end  27  is the part that fixably attaches to main branch  10 , as described above. The dimensions of suture eyelet  16  generally permit main branch  10 , and suture locking braid  18 , to pass through its opening during antegrade movement (arrow  15 ). However, in response to retrograde movement (arrow  17 ) free end  29   a  does not pass retrograde back through suture eyelet  16 , but rather deforms and is constrained against such retrograde movement upon engaging with perimeter  19  of suture eyelet  16 . 
     By way of non-limiting example, the diameter of a #2-sized suture is about 0.5 mm. In some embodiments, a plurality of suture locking braids  18 , each having a diameter of about 0.5 mm, are fixably attached to main branch  10  of a #2-sized suture. Given these dimensions, some embodiments would utilize a suture eyelet  16  having a diameter of about 0.5 mm to about 1.0 mm, and preferably of about 0.7 mm. During antegrade movement (arrow  15 ), dimensions on these orders allow relatively easy passage of main branch  10  by itself through suture eyelet  16 , but passage of main branch  10  combined with a suture locking braid  18  is a tighter passage. In some embodiments, the length of each suture locking braid  18  is determined as a function of the diameter of suture eyelet  16 . For example, in some embodiments, the length of each suture locking braid  18  is equal to or greater than about 2-5 times the difference between the diameter of suture eyelet  16  and main branch  10 . Thus, it will be appreciated that surface area increases as diameter increases. 
     Present embodiments are used in multiple ways with various kinds of endoscopic surgeries, including arthroscopy.  FIG. 4  illustrates a soft tissue repair using a suture  8 , according to multiple embodiments and alternatives. Tissue  20  is torn at and along an area represented by tear  21 . In various kinds of surgeries, e.g., arthroscopic, tissue  20  is proximal to bone  22 . In the operation, a segment of main branch  10  is passed through one end of tissue  20  and then through another end of tissue  20 , and this may be repeated multiple times according to a pattern as selectably chosen by a surgeon. When the pattern is complete, a surgeon passes a segment of main brain  10  having at least one suture locking braid  18  through suture eyelet  16 . Direction of initial travel of main branch  10  is denoted by antegrade movement arrow  15 . The length of the first segment of main branch  10  passing through suture eyelet  16  determines how many suture locking braids  18  also pass through. This can be as few as one suture locking braid.  FIG. 4  shows suture locking braids  18   a ,  18   b ,  18   c ,  18   d , and  18   e  as part of the first segment. However, it will be appreciated that the length of the first segment of main branch  10  passing through suture eyelet  16  is selectably chosen by a surgeon as a function of the tension desired to be placed on the tissue ends. Accordingly, retrograde movement depicted by arrow  17  is limited because the last suture locking braid  18   a  to pass through suture eyelet  16  cannot pass back to the other side. This is because, when suture locking braid  18   a  is engaged with sustained contact against suture eyelet  16 , e.g., by manually pulling on the main branch in the retrograde direction, it deforms into a shape having dimensions larger than the dimension of the opening of suture eyelet  16 . 
       FIG. 5  further depicts a repair of tissue  20  that has partially torn away from bone  22 . According to techniques and methods known in the art of surgical repair, suture anchor  24  having an anchor eyelet  26  may also be used as a fixation point for the repair. In this type of repair, main branch  10  is partially passed around a surface of tissue  20 . It is passed through anchor eyelet  26  before completing at least one circuit around tissue  20 . The dashed lines indicate main branch  10  passing “behind” tissue  20  (i.e., to the posterior side if tissue  20  is viewed anteriorly, and vice versa) before being passed through suture eyelet  16 , all in a direction denoted by antegrade movement arrow  15 . A very simple pattern is shown in  FIG. 5 , but it will be appreciated that a locking suture according to multiple embodiments and alternatives is used with many kinds of patterns, according to a surgeon&#39;s preference. Once main branch  10  and at least one suture locking braid  18  pass through suture eyelet  16 , retrograde movement back through the suture eyelet (i.e., in a direction depicted by arrow  17 ) is limited as discussed above. 
     With respect to  FIGS. 4 and 5 , any items denoted by reference numerals  20 - 26  are not part of the claimed invention. 
       FIG. 6  illustrates an alternative embodiment of a locking suture  5 , in which at least one outer member  28  (or a plurality of them, as is illustrated) substantially surrounds a portion of main branch  10 . The purpose of outer members  28  is similar to that of suture locking braids  18 , namely the limitation of and resistance to retrograde movement. Outer members  28  are generally formed from the same or similar materials as suture locking braids  18 . Further, each outer member  28  has a nose  30  and a trailing edge  32 . Generally, nose  30  has a forward-facing surface  34  oriented toward a first direction of travel, as indicated by directional arrow  15 . In some embodiments, nose  30  is fixably attached to main branch  10  through conventional means known in the art, including but not limited to weaving nose  30  into the fibers of main branch  10 , thermal deformation, and gluing nose  30  to main branch  10 . 
     Generally, each outer member  28  is positioned such that, during antegrade movement (arrow  15 ), nose  30  travels through suture eyelet  16  before trailing end  32  does. In some embodiments, outer member  28  is an irregular cylinder, the circumference of which tapers from least at its nose  30  to greatest at trailing end  32 . Alternatively, outer member  28  includes a beveled surface  31  such that the circumference at nose  30  is less than the circumference at trailing end  32 . Accordingly, nose  30  passes through more easily than does trailing edge  32 . Optionally, outer member  28  is formed from compressible material in order to facilitate passage through suture eyelet  16  during antegrade movement. In some embodiments, trailing edge  32  is sized, relative to the dimensions (e.g., diameter) of suture eyelet  16 , so that it fits only snugly through suture eyelet  16  during antegrade movement (arrow  15 ), yet passage through suture eyelet  16  during antegrade movement is limited. 
       FIG. 7  is a cross-sectional view of one such outer member  28  surrounding main branch  10 . Outer member  28  has a first region “X” that includes a beveled surface  31  flaring outward from main branch  10 . A second region “Y” comprises a cylinder around main branch  10  terminating at trailing edge  32 . In some embodiments, trailing edge  32  is a circular base, the circumference of which is greater than at any other portion of outer member  28 . 
     In some alternative embodiments, the geometry of cylindrical member is substantially conical, wherein nose  30  is the most narrow portion of outer member  28 , substantially resembling the vertex of a cone or truncated cone with a circular cross-section, the circular base of which is positioned at trailing edge  32 . Optionally, the shape can be that of a partial cone or truncated cone with a semi-circular cross-section. Alternatively, outer member  28  is substantially pyramidal (not shown), wherein nose  30  is the most narrow portion of outer member  28 , substantially resembling the vertex of a pyramid, the base of which is positioned at trailing edge  32 . In some embodiments, the base, and therefore the cross-section of the pyramid, is chosen from the group triangular, square, rectangular, pentagonal, and hexagonal, with the number of lateral faces of the pyramid being equal to the number of sides forming the base. 
       FIG. 8  shows a locking suture in use, with a plurality of outer members  28 , including outer member  28   a  being the last one to pass through suture eyelet  16  in response to antegrade movement (arrow  15 ). Upon reaching that point, retrograde movement (arrow  17 ) of main branch  10  causes outer member  28   a  to contact perimeter  19  of suture eyelet  16 . Upon sustained contact with perimeter  19  of suture eyelet  16 , a mechanical impediment is created by the size and dimension of suture eyelet  16  compared to the size and width of outer member  28   a . The mechanical impediment causes the latter to undergo buckling deformation, which may be marked by longitudinal shortening, as illustrated in  FIG. 8 . Deformation of outer member  28   a  increases its surface area, particularly of trailing edge  32   a , relative to suture eyelet  16 , in order to limit retrograde passage back through the suture eyelet. By limiting retrograde movement of main branch  10 , suture strand  8  maintains a desired tension. 
     In some embodiments, each outer member  28  is fenestrated such that it further comprises at least one slit  35  running longitudinally along at least a portion of the surface of outer member  28 . Slit  35  allows outer member  28  to compress as it passes through suture eyelet  16  during antegrade movement (arrow  15 ), yet the outer member fans out once passage is completed, thus increasing circumference at trailing edge  32 . The increased circumference of trailing edge  32  further limits retrograde passage back through suture eyelet  16 . In some embodiments, there are a plurality of slits  35 . Preferably each outer member  28  has between two and four slits  35 . 
     It will be understood that the embodiments described herein are not limited in their application to the details of the teachings and descriptions set forth, or as illustrated in the accompanying figures. Rather, it will be understood that the present embodiments and alternatives, as described and claimed herein, are capable of being practiced or carried out in various ways. 
     Also, it is to be understood that words and phrases used herein are for the purpose of description and should not be regarded as limiting. The use herein of “including,” “comprising,” “e.g.,” “containing,” or “having” and variations of those words is meant to encompass the items listed thereafter, and equivalents of those, as well as additional items. 
     Accordingly, the foregoing descriptions of several embodiments and alternatives are meant to illustrate, rather than to serve as limits on the scope of what has been disclosed herein. The descriptions herein are not intended to be exhaustive, nor are they meant to limit the understanding of the embodiments to the precise forms disclosed. It will be understood by those having ordinary skill in the art that modifications and variations of these embodiments are reasonably possible in light of the above teachings and descriptions.