Patent Publication Number: US-2011054524-A1

Title: Implantable prosthetic cord

Description:
The present invention relates to a surgical cord configured to secure a first biological tissue site to a second biological tissue site and a method of surgical repair. 
     Soft tissue (tendon and ligament) ruptures are common amongst sports professionals and the elderly for example. A number of different procedures have been developed to repair soft tissue tears being specific to the damaged, anatomical region. 
     In particular, a number of different connecting devices have been proposed to reconnect the torn tissue to its original anchor point which may typically comprise a bone site. Important considerations for these connecting devices such as sutures and surgical tapes include strength and ease of manipulation by the surgeon during repair surgery. Surgical tapes in particular comprise bioabsorbable or non-bioabsorbable materials from natural or artificial sources including for example gut, silk, cotton, polyester and specific ultra high molecular weight polyethylene (UHMWPE). A further important characteristic of the cord is its resistance to ‘tissue pull-through’ when under load. Tissue pull-through refers to the process of the cord or tape pulling or cutting through the tissue under tensile load when the joint is manipulated post surgery. Cords having small diameters or widths and sharp edges are disadvantageous as they are more susceptible to tissue pull-through. Cords having a greater width are however often difficult to manipulate by a surgeon who is typically required to thread the ends of the cord through narrow apertures and form knotted attachments. 
     US-2005/0192631 discloses a suture tape construct comprising a braided high strength surgical suture material. A tubular braided suture extends along the length of the tape to provide a backbone to the construct. The tape comprises an additional flat braided middle portion through which the tubular braided suture is threaded. Transition sections at each end of the flat braid are tapered to allow the suture tape to pass through apertures during surgical procedures and provide a means of anchoring the central tubular suture to the flat tape. The construct comprises UHMWPE fibre blended with one or more long chain synthetic polymers such as polyester to provide the desired strength. 
     US 2004/0078089 discloses a textile prostheses for use as a surgical implant in which a main portion comprises at least one anchorage body portion designed to accommodate tensile loadings and being resistant to stretch when placed under load. The anchoring portions may comprise tapers or a width being less than the main body. 
     There is therefore a need for surgical cord or tape that is both easy to manipulate by a surgeon during surgical procedures whilst exhibiting the required strength and tissue pull through resistance. 
     The present invention provides a surgical cord prostheses exhibiting strength characteristics suitable for use as a means of connection between two biological tissue sites. In particular, the present surgical cord is ideally suited to reconnect soft tissue in the form of tendons, ligaments and the like, to a bone site. The tape comprises a wide flat main body that exhibits tissue pull through resistance and has adjacent thin end regions to allow the cord to be manipulated during surgical procedures. 
     According to a first aspect of the present invention there is provided a surgical cord comprising: a plurality of interwoven yarn strands comprising warps and wefts extending over a woven main length of the cord, the main length having a width; two end regions formed by said yarn strands, a width of said end regions being less than the width of the main length wherein said warps extend from said main length in to each end region; and wherein the main length of the cord comprises a flat, substantially planar profile. 
     Preferably, the yarn strands comprise twisted polyester fibres such that the surgical cord may comprise exclusively polyester yarn strands. Due to the cord construction, the requirement for UHMWPE which is commonly incorporated within surgical tape to provide tensile strength, is avoided. The present cord is therefore easy to manufacture, comprising a single material. 
     The main length of the cord is woven however the end regions may be interlaced, woven, knitted or braided. The yarn strands of the main length are interwoven and comprise warps (aligned with the longitudinal axis of the cord) and wefts (aligned transverse to the longitudinal axis of the cord), both warps and wefts extending along the cord main length. According to specific implementations, the cord comprises a plurality of groups of three wefts interwoven with perpendicular aligned groups of three wefts to form a woven mesh-like structure. This open weave structure provides a scaffold promoting tissue ingrowth and post surgical repair. 
     The warps, and optionally the wefts, extend from the main length into each end region. The end regions may be braided and in particular the warps in the end region, extending from the main length, may be braided. 
     The number of warps in the end regions may be equal to the number of warps in the main length or the number of warps may decrease along the end regions in a direction away from the main length. Preferably, the spacing of the yarn strands in each end region is less than the spacing between the yarn strands in the main length so as to provide a more dense cord at the main length. 
     The wefts may extend from the main length into each end region. The spacing between wefts within each end region may be greater or equal to the spacing of the wefts in the main length. Optionally, the wefts may terminate at the transition between the main length and end regions. Optionally, the wefts extending into each end region may be braided. 
     Optionally, the warps are bound within the end regions by twisting or plying. Alternatively, the warps extending from the woven tape section into the end regions may be bound by knitting or braiding. Alternatively the warps may be bound together by additional embroidery. Alternatively the warps may be bound together by wrapping, the warps acting as a core. The wrapping may be provided by the warps extending from the woven tape main body or additional yarn may be used. The features in the end regions in each of the embodiments described above may be formed from the wefts alone, or the warps alone, or a combination of the wefts plus the warps or by using an additional material. In each case all or a proportion of the wefts or warps may be used. 
     Alternatively, the main body of the cord may incorporate twisted, plyed, braided or plaited yarns as warps which extend from the woven main body section into the end region. The yarn in the end regions may be bound together by further twisting or plying or by additional braiding, plaiting, knit braiding, linking, knotting and/or wrapping. Other wraps running parallel can be incorporated into this twist, ply and/or braid etc. or removed at the end of the main body section. 
     Optionally, additional braided, plaited, twisted, plyed, or woven yarns may be embroidered or sewn onto the either or both of the upper or lower face of the flat substantially planar cord. These additional yarns may then extend beyond the main body into the end regions and run substantially parallel with the warps of the main body. Optionally, warps extending from the main body into the end sections may be removed to reduce the bulk of material at these end sections. 
     Alternatively, braided, plaited, twisted, plyed or woven yarns may be threaded amongst the woven warps and wefts extending within the main body. These additional yarns may extend into the end regions. Some or all of the warps extending within the main body may not extend into each end region. 
     The cord main length is flat having a substantially wide planar tape like structure. This configuration resists cutting through the soft tissue under load. The end regions may also be flat and comprise a substantially uniform width and thickness over the respective length of each end region. Reference within this specification to a ‘substantially planar profile’ includes a cord that is many orders of magnitude wider that it is thick. For example, the cord, at the main length, may be formed from a single layer of interwoven strands or a plurality of layers that are overlaid or flattened again one another so as to provide a tape like profile. In particular the main length may be formed from a tubular woven textile that has been flattened with the walls of the tube in contact such that there is no internal hollow cavity between the otherwise tubular cord. Where the cord is multilayered (initially tubular), it is configured to maintain its resulting planar profile via initial processing such as pressing or ironing flat optionally involving heat treatment. Optionally, the layers may be attached together via embroidery, stitching and the like 
     According to a second aspect of the present invention there is provided a method of surgical repair comprising: securing a cord to a first biological tissue site, said cord comprising: a plurality of interwoven yarn strands comprising warps and wefts extending over a woven main length of the cord, the main length having a width; two end regions formed by said yarn strands, a width of said end regions being less than the width of the main length wherein said warps extend from said main length in to each end region; and wherein the main length of the cord comprises a flat, substantially planar profile; securing said cord at a second biological tissue site; wherein said cord extends between said first and second tissue sites. 
     The present method is advantageous for the reconstruction and attachment of soft tissue to a bone site as part of a surgical repair procedure. 
     The method preferably comprising forming at least one hole at the first tissue site and threading the cord through the hole to form a loop. The method may further comprise drilling at least one hole or through-bore at the bone site and threading the cord through the bone tunnel. The ends of the cord may then be secured in position at the bone site by knotting the ends of the cord together to prevent retraction as the joint is manipulated and the cord placed under tensile load. 
     According to a third aspect of the present invention there is provided a method of connecting a first biological tissue site to a second biological tissue site comprising: securing a cord to a first tissue site by threading said cord through at least one hole formed in said first tissue site, said cord comprising a plurality of interwoven yarn strands comprising warps and wefts extending over a woven main length of the cord, the main length having a width; two end regions formed by said yarn strands, a width of said end regions being less than the width of the main length wherein said warps extend from said main length in to each end region; and wherein the main length of the cord comprises a flat, substantially planar profile; securing said cord to a second tissue site; wherein said cord extends between said first and second tissue sites. 
     The present invention is particularly suitable to reconstruct a torn rotator cuff by reconnecting the rotator cuff with the humeral head via the present surgical tape. 
     Preferably, the method comprises forming at least two holes in the cuff tissue and looping the cord through the holes such that the cord extends from the tissue as two strands positioned side by side. This would involve threading the cord through the cuff tissue to form an n-shaped loop. This has the advantage of forming a strong couple between the prosthetic and the biological tissue and obviates the use of additional securing sutures according to prior art methods of attachment. The method further comprises securing the cord to the humeral head by first drilling holes through a region of the humeral head, threading the end regions of cord through the bone tunnels, and knotting the cord ends together to provide fixation. 
     The width of cord along the main length is configured such that when arranged in this side-by-side configuration the thickness of the prosthetic rotator cuff is approximately equal to the width of the cuff tissue to which it is attached. 
     Both ends of the cord are tapered and sealed allowing the cord to be easily manipulated and pulled through the soft tissue and bone tunnels. The cord ends provide ease of knotting and the reduced bulk of material at the ends allows for the creation of smaller knots. The thickness of the cord, particularly when arranging in the side-by-side configuration and looped through the tissue via two holes, acts as an extension to the torn rotated cuff and provides excellent intrinsic strength and allows early mobilisation. The combined dual cord width, in the side-by-side arrangement, also serves to inhibit joint dislocation by effectively restricting the joint/bone movement due to the increased cord-bone contact surface area. 
    
    
     
       Other features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings in which: 
         FIG. 1   a  is a schematic illustration of the surgical cord according to one specific implementation; 
         FIG. 1   b  is a schematic illustration of a further specific implementation of the medical cord; 
         FIG. 2  is a schematic illustration of a further specific implementation of the medical cord; 
         FIG. 3   a  is a schematic illustration of a further specific implementation of the medical cord; 
         FIG. 3   b  is a schematic illustration of a further specific implementation of the medical cord; 
         FIG. 4   a  is a schematic illustration of a further specific implementation of the medical cord; 
         FIG. 4   b  is a schematic illustration of a further specific implementation of the medical cord; 
         FIG. 4   c  is a schematic illustration of a further specific implementation of the medical cord; 
         FIG. 4   d  is a schematic illustration of a further specific implementation of the medical cord; 
         FIG. 4   e  is a schematic illustration of a further specific implementation of the medical cord; 
         FIG. 4   f  is a schematic illustration of a further specific implementation of the medical cord; 
         FIG. 4   g  is a schematic illustration of a further specific implementation of the medical cord; 
         FIG. 4   h  is a schematic illustration of a further specific implementation of the medical cord; 
         FIG. 4   i  is a schematic illustration of a further specific implementation of the medical cord; 
         FIG. 4   j  is a schematic illustration of a further specific implementation of the medical cord; 
         FIG. 5   a  is a cross sectional side elevation view through the shoulder joint of a human having torn rotary cuff tissue; 
         FIG. 5   b  is a perspective view of the shoulder joint of  FIG. 5   a;    
         FIG. 6  illustrates the shoulder joint of  FIG. 5   b  during a second stage of the surgical procedure; 
         FIG. 7  illustrates the shoulder joint of  FIG. 6  during a third stage of the surgical procedure; 
         FIG. 8  illustrates the shoulder joint of  FIG. 7  during a fourth stage of the surgical procedure; 
         FIG. 9  illustrates the shoulder joint of  FIG. 8  during a fifth stage of the surgical procedure; 
         FIG. 10  illustrates the shoulder joint of  FIG. 9  during a sixth stage of the surgical procedure; 
         FIG. 11  illustrates a cross section through the shoulder joint according to  FIG. 5   a  during a seventh stage of the surgical procedure; 
         FIG. 12   a  illustrates the shoulder joint of  FIG. 11  at the end of the surgical procedure; and 
         FIG. 12   b  illustrates the perspective illustration of the shoulder joint of  FIG. 10  at the end of the surgical procedure. 
         FIG. 13  illustrates alternative positions of the medical cord in the cuff tissue. 
     
    
    
     Referring to  FIG. 1   a  the surgical cord comprises an interwoven mesh like structure having a plurality of overlapping yarn strands. Each yarn strand comprises a plurality of polyester fibres that are bundled together by twisting or other conventional methods common to the textile industry. The yarn strands are arranged as a plurality of warps  103 ,  104  aligned substantially parallel with the longitudinal axis of the cord. The strands are also arranged as wefts  105  that overlap and intersect each warp at an angle of 90°. The warps and wefts may be formed by a single piece of yarn or separate yarn pieces, interwoven to create yarn strands, according to conventional textile weaving processes. 
     The cord comprises outermost warps  103  forming edge regions of the cord and innermost warps  104  forming the inner body of the cord aligned parallel with the outermost warps  103 . 
     The cord comprises a main length  100  and two end regions  102  separated from the main length by tapered regions  101 . The main length  100  comprises a width (a) which is greater than a width (b) of end regions  102 . The cord width decreases from width (a) to width (b) within tapered region  101 . 
     Warps  103 ,  104  are separated by distance (f) aligned perpendicular to the main length of the cord within main length region  100 . Within this main length region  100  warps  103  are separated by distance (c) aligned with the main axis of the cord. Within end region  102 , distance (e) between warps  103 ,  104  is less than distance (f). The distance (d) between adjacent runs of weft  103  within end regions  102  is greater than distance (c) within the main length according to the specific implementation of  FIG. 1   a.    
       FIGS. 1   a  to  4   j  are schematic illustrations of the medical cord. According to the preferred embodiment, each weft and warp illustrated within  FIGS. 1 to 4   j  comprise three individual yarn strands positioned side by side. Such that at any one overlapping junction between warp  103 ,  104  and weft  105 , both outermost strands of the set of three warps pass above or below each corresponding outermost strands of the weft whilst respective innermost strands of each warp and weft triad overlap in the opposite direction. 
       FIG. 1   b  illustrates a further specific implementation of the medical cord in which the distance (c) between each run of weft  105  within main length  100  is equal to the distance (d) between weft runs within end regions  102 . 
     According to a third embodiment, the weft  105  extends over main length  100  and tapered region  101  and past the interface  200  between the tapered region  101  and end region  102 . Weft  105  terminates  201  at end region  102  in close proximity to tapered region  101  such that the majority of the length of each end region  102  is devoid of weft  105 .  FIG. 3   a  illustrates the medical cord of  FIG. 2  in which the warps  103 ,  104  within end region  102  are overlapped  303  to form braided section  302 . Braiding  303  prevents yarn strands  103 ,  104  from separating or splitting during manipulation. According to the embodiment of  FIG. 3   a , a region  301  immediately proximate to tapered region  101  is devoid of braiding  303 . In an alternative embodiment the braided region  302  may extend the entire length of each end region  102  such that there is no area devoid of braiding  301 . In an alternative embodiment the weft  105  is incorporated into the braided region  302 . 
       FIG. 3   b  illustrates a variation of the braided end region embodiment of  FIG. 3   a . According to this embodiment, only the outermost warps  303  are braided together 304 within braided end region  302 . Innermost warps  104  are unbraided and extend substantially parallel with the longitudinal axis of the cord. This configuration provides for a thinner end region than the embodiment of  FIG. 3   a  whilst maintaining structural integrity of the yarn strands within end regions  102 . 
       FIG. 4   a  illustrates a sixth embodiment of the present invention in which the respective length of each warp  103 ,  104 ,  401  within the end region  102  differs. This configuration provides a fully tapered width of cord from main length  100  through tapered region  101  and into end regions  102 . The amount of cord material therefore decreases within end regions  102  in a direction away from main length  100 . Weft  105  is interwoven amongst each warp strand within end region  102  to avoid warps  103  of shorter length from splitting from the main body of cord. The length of the outermost wefts  103  within end region  102  is less than intermediate warps  104  which in turn have a length less than innermost warps  400 . 
       FIGS. 4   b  to  4   j  illustrate various different additional embodiments of the present invention in which the cord main body comprises a woven mesh like structure and is bordered at each end by end portions comprising a width being less than that of the main cord length. 
     The present invention provides a method for the surgical repair of anatomical regions and in particular joints involving cooperation between soft tissue and bone matter. A surgical repair procedure is described with reference to  FIGS. 5   a  to  12   b  by way of example with reference to the human shoulder joint. The procedure involves repair of torn rotator cuff tissue at the region of the humeral head. The surgical cord of  FIGS. 1   a  to  4   j  is particularly suitable to repair massive, chronic, retracted tears of the rotator cuff tissue that cannot be mobilised back onto the bone attachment site or if the cuff tissue has undergone degeneration in the case of older patients. 
       FIGS. 5   a  and  5   b  illustrate a cross sectional and perspective view respectively, through a human shoulder region  500  in which the rotator cuff tissue  503  has been torn and separated from the humerus  501  and in particular the humeral head  502 . The first stage of the surgical procedure of  FIG. 5   a  follows preparatory steps involving dissection of skin and subcutaneous tissue, the application of a haemostasis and appropriate retractors to separate the humerus from the acromion to enable visualisation of cuff tissue  503 . 
     A stab wound is made through a modified Neviaser portal  508 . The cuff tissue  503  is grasped by forceps  504  and pulled  507  to keep it under tension. An artery forceps  505  is passed through the skin, subcutaneous tissue and through the posterior portion of the retracted rotator cuff  503  medial to the tear. The artery forceps  505  is passed through the cuff  503  until the tip of the forceps is visualized through the wound  509 . 
     Referring to  FIG. 6 , medical cord  601  is introduced into wound  509  and the end of cord  602  is grasped by the artery forceps  505 . The artery forceps and the cord end  602  are pulled back through cuff  503  and out of the modified Neviaser portal  508 . 
     Referring to  FIG. 7 , a hook  700  is brought into position behind cord  601  by insertion through wound  509  to bring the superior arm of the ligament into the wound by drawing hook  700  away from the wound  701  to provide the looped arrangement illustrated in  FIG. 8 . A stab wound  801  is made through the antero superior portal and the cuff engaged with a grasper or Kocher forceps  504 , and pulled  802  to maintain tension in cuff tissue  503 . The artery forceps  506  is passed through the skin, subcutaneous tissue and through the retracted anterior portion of the cuff  503 , medial to the tear and through the healthy cuff tissue. Forceps  506  are passed through the cuff until the tip of the forceps is visualized through wound  509 . 
     Referring to  FIG. 9 , the inferior arm cord  601  is passed into the wound and the end of the tape grasped with the artery forceps  506 . The artery forceps together with cord  601  are pulled back through the cuff and out of the antra superior portal  801 . Accordingly, cord  601  forms a loop  900  at cuff tissue  503 , both strands of cord  601  extending from the superior face of cuff tissue  503  as illustrated in  FIG. 9 . Securing the cord to the cuff tissue by threading the cord through two holes in the cuff tissue to create an n-shaped loop, with two strands of cord extending away from the cuff tissue provides a secure connection between the prosthetic and soft tissue. The use of additional sutures to secure the prosthetic to the tissue is negated providing strength advantages. When each end of cord  601  is pulled to create tension in both strands and cuff material  503 , as illustrated in  FIG. 10 , loop  900  sits against the inferior surface of cuff tissue  503 . Cuff  503  is pulled together with prosthetic ligament  601  into the wound using the ends of the ligament  601 . 
     Referring to  FIG. 11 , a suitable anchor region is identified at the greater tuberosity  110  extending at humeral head  502 . In a first stage (not shown) drill  1101  is used to create two parallel aligned boreholes  1102  extending into the greater tuberosity  110 . A bone awl  1103  is then inserted into each bore  1102  and an oblique drill hole  1104  is created at the outer side of the humerus to meet the tip of awl  1103 . The portal is then marked with a diathermy (not shown). This procedure is used to create two bony tunnels parallel to one another extending through the greater tuberosity. 
     Referring to  FIGS. 12   a  and  12   b , each end of cord  601  is then passed through each respective tunnel  1102 ,  1104  maintaining the tension in the rotator cuff  503 . This can be facilitated by using a suitable suture passer, snare or vinyl suture passer (not shown) through the tunnels. The task of threading cord  601  through tunnels  1102 ,  1104  is also facilitated by end regions  102  having a width being less than the cord main length  101 . 
     The final stage of the procedure involves pulling cord  601  to ensure cuff tissue  503  has partially covered humeral head  502  and in particular the upper convexity of head portion  502 . The two ends of cord  601 , emergent from both tunnels  1104  are then tied together in a knot  1200  on the outside of the humerus preferably using a triple knot whilst maintaining the tension in rotator cuff tissue  503 . The procedure is completed with a capsular repair over the knot and the layer wise closure of the wound. 
     Referring to  FIG. 12   b , the first strand  1201  and second strand  1202  of the present medical cord are aligned side-by-side and substantially parallel between soft cuff tissue  513  and the bone anchor site—corresponding to the bone tunnels  1102 ,  1104  formed within the greater tuberosity  1100 . The combined thickness of strands  1201 ,  1202  of cord  601  is approximately equal to the width of the cuff tissue  503 . The interwoven mesh like structure of cord  601  provides a scaffold for the ingrowth of tissue at the repair site and in particular the interface between prosthetic ligament  601  and cuff tissue  503 . The combined thickness of strands  1201 ,  1202  simulates the cuff tissue  503  to restrict the free movement of the humerus  501  and prevent it from over rotation and subsequent dislocation of the joint. 
     The tapered end portions of cord  601  allows for the creation of a small knot  1200  which is advantageous to secure the cord in position at humerus  501 . The use of prosthetic  601  avoids the risks and problems associated with allografts and avoids donor site morbidity as encountered with autografts. 
     Preferably, the cord  601  comprises flat tape 10 mm wide by 500 mm long and comprises an open-weave polyester fabric. The drill holes are approximately 3.2 mm in diameter although variation of these dimensions is within the scope of the present invention. 
     Referring to  FIG. 13 , the flat tape  601  preferably emerges from the cuff tissue  503  on the superior surface (a). This prevents the lip of the cuff tissue  1300  bulging superiorly which would occur if the flat tape  601  emerged from the inferior surface (b).