Abstract:
Two spaced bodily tissues are approximated with a surgical tensioning device comprising a resilient member and a pressure locking device. The method comprises a step of routing one end of a length of suture through both spaced bodily tissues and inserting the suture end into and through the pressure locking device. The suture is then tensioned by pulling on the suture end passing through the pressure locking device. Responsive to tension changes in the suture, the pressure locking device is actuated by moving at least one surface in the pressure locking device to clamp the suture in position.

Description:
This application claims the benefit under 35 U.S.C. 119(e) of the filing date of Provisional U.S. Application Ser. No. 61/037,582, entitled Dynamic Ring Compression Device, filed on Mar. 18, 2008, and expressly incorporated herein by reference, in its entirety. This application is also related to co-pending U.S. patent application Ser. No. 12/347,821, entitled Dynamic Suture Tensioning Device and filed on Dec. 31, 2008, and to U.S. patent application Ser. No. 12/406,904, entitled Load Shaping for Dynamic Tensioning Mechanisms and Methods, and Ser. No. 12/406,909, entitled Dynamic Tissue Holding Device with Low Profile Spring, both filed on even date herewith, all of which are commonly assigned and expressly incorporated herein, by reference, in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is related to the general surgical repair of separated body tissues, and more particularly to internally fixating and stabilizing such body tissues, specifically bones. 
     In the present state of the art, there are a number of systems available to repair biological tissues separated in surgery or by injury. These products serve to approximate and stabilize the tissues so that healing may commence and provide compression in the interface to promote healing. Compression and stability are critical for proper anatomical healing of tissue. With the correct amount of compression applied to the interface of the tissue portions to be joined, signals are sent to the tissue, thus allowing the tissue to remodel in proper anatomical position. The amount of compression applied to the tissue interface needs to be appropriate to the type of tissue that is being healed. 
     A common problem in using suture is the variable nature of the residual tension realized after the knot is tied. Hand tied knots usually supply only a fraction of the residual tension for which the suture is capable. There are various procedures where the residual tension in a hand tied knot is insufficient to approximate and generate the compression needed for healing between tissues. Moreover, knot stacks can interfere with the natural movement of surrounding tissues. 
     There are times when high tension may cause suture to cut into tissue at points of stress concentration. This suture cutting may not happen immediately. It can take place as the tissue degrades or relaxes, or sometimes there are external forces that cause the suture to cut into the tissue. This cutting action releases tension in the suture and adversely affects the quality and durability of the repair. 
     Additionally, the use of wires can cause damage to adjunctive tissues because of penetration by the sharp ends of the wires. 
     What is needed, therefore, are devices and techniques for holding two tissue portions in a state of compression and tension beyond that which is commonly achieved using hand-tied sutures. 
     SUMMARY OF THE INVENTION 
     The present invention solves the problems outlined above by providing a means to approximate two tissue portions together so that there is compression in the tissue interface. The invention provides a means to hold two tissues in a state of compression beyond that which is commonly achieved with the hand tying of sutures. The invention may also be used to lengthen retracted tendons or ligaments. This is done by anchoring one end of the suture on bone and the other end on tendon or a ligament. The dynamic tensioning element in the invention serves to stretch and optionally attach the tendon or ligament to the bone. 
     Attached to one end of the suture is a resilient mechanism designed to keep tension in the suture, as tissues will shrink during healing. This resilient mechanism lies on top of the tissues to be approximated. The free end of the suture is brought to the resilient mechanism and routed into an integral receptacle such that pulling on the suture end will bring the tissues together. As the tissues come together and tension is brought to the suture, the resilient mechanism will activate and start to store the energy needed to activate the resilient mechanism, in order to keep tension on the suture when the tissues shrink during healing. 
     When the desired suture tension has brought the tissues to their desired position for healing, a surface or surfaces within the suture receiving receptacle acts to put pressure on the suture. The pressure applied is sufficient to bind the suture end with the resilient mechanism. This surface, or these surfaces, within the suture receiving receptacle provide(s) latent pressure on the suture during the suture tensioning process. The latent pressure is then converted to a binding pressure, once the suture has approximated the tissues. This pressure conversion happens as a result of the change in tension on the suture as it is released from the practitioner&#39;s grasp. 
     The suture interacts with the binding surfaces by means of friction. Friction always acts in the opposite direction of motion. As the suture is drawn to tighten tissue, the frictional interaction opposes this motion. Consequently, more force is needed to achieve the same effect on the tissue. Once the practitioner releases the suture, the motion of the suture changes direction, and so does the frictional forces. Now, the friction forces act to bind the suture to the resilient mechanism by means of the surface or surfaces. 
     This invention takes advantage of this change in frictional force direction to bind the suture to the resilient means. This is managed by having more than one surface interacting with suture within the receiving receptacle. These surfaces can move relative to one another. The suture, in being tensioned, moves a surface relative to another surface so that less pressure is put on the suture and the suture is free to move. Then, the tension is released from the suture and the suture changes direction, pulling the surfaces in the opposite direction relative to one another. This changes in direction moves the surfaces to put more pressure on the suture, thus binding it in the suture receiving receptacle. 
     Other embodiments of the invention use mechanical means to draw the surface together, so that sufficient pressure is put on the suture to bind it in the suture receiving receptacle. 
     The tissue portions comprise biological tissue in the body, including, but not limited to, skin, tendon, bone, ligaments, blood vessels, and organs. The suture may comprise woven, braided, or knitted fibers or metals, or a monofilament, and can be made of any known suture material. The suture may be of any shape, including, but not limited to, round, square, oval, flat (like a strap), or tubular. The shape of the suture for particular embodiments will be discussed more fully hereinbelow. 
     More particularly, there is provided a surgical tensioning device for dynamically holding two tissue portions in contact with one another. The inventive device comprises a resilient member and a pressure locking mechanism engaging the resilient member. The pressure locking mechanism has a surface for engaging and clamping a length of suture passing therethrough, which is responsive to tension changes applied to the suture to secure the suture in place without a need for knotting the suture. In some embodiments, the resilient member comprises a spring having a base portion and a plurality of extending portions extending from the base portion. An attachment point is disposed on each of the plurality of extending portions. The plurality of extending portions may comprise legs spaced from one another and upstanding from the base portion. The legs each have distal ends, and one of the attachment points is disposed on each of the leg distal ends. The pressure locking mechanism comprises one of the attachment points. 
     A second one of the attachment points, on a second one of the legs, is adapted to be connected to a first end of a length of suture, and a second end of the length of suture is adapted to be secured within the pressure locking mechanism. 
     In one particular embodiment, the pressure locking mechanism comprises a tube having an internal cylindrical wall which comprises the aforementioned single surface, with the suture being adapted to pass through a lumen in the tube defined by the internal cylindrical wall. The internal cylindrical wall is adapted to collapse about the suture responsive to tension placed on the suture. 
     In certain preferred embodiments, the resilient member is fabricated from one of spring tempered stainless steel or titanium, as is the pressure locking mechanism. However, the pressure locking mechanism is fabricated from one of fully annealed spring tempered stainless steel or fully annealed titanium. 
     In another embodiment of the invention, the pressure locking mechanism comprises a plurality of the aforementioned clamping surfaces. In this embodiment, the pressure locking mechanism comprises a loop having an internal surface defining a channel through which the suture may pass, and an inserting plug which is insertable into the channel. The inserting plug has an external surface, wherein the suture is clamped between the internal surface of the loop and the external surface of the inserting plug. Preferably, one of the internal surface of the loop and the external surface of the inserting plug is textured. 
     In yet another embodiment of the inventive device, the suture preferably comprises flat or tape suture. The resilient member comprises a spring loop and a plurality of attachment points for securing the suture to the resilient member, and the pressure locking mechanism is disposed at one of the attachment points. The pressure locking mechanism comprises a pin and a pair of flexible arms for supporting the pin, a gap being formed between the pin and a surface of the spring loop for receiving the suture, wherein when tension in the suture changes, the spring loop moves to clamp the suture between the spring loop surface and the pin. 
     In another aspect of the invention, there is provided a pressure locking mechanism for securing suture in place at a procedural site. The pressure locking mechanism is adapted for engagement with a resilient member and has a surface for engaging and clamping a length of suture passing therethrough. The surface is responsive to tension changes applied to the suture to secure it in place without a need for knotting the suture. The pressure locking mechanism comprises, in one embodiment, a tube having an internal cylindrical wall which comprises the aforementioned surface, with the suture being adapted to pass through a lumen in the tube defined by the internal cylindrical wall, and the internal cylindrical wall being adapted to collapse about the suture responsive to changes of tension on the suture. In other embodiments, the pressure locking mechanism comprises a plurality of the aforementioned surfaces. In one modified embodiment, the pressure locking mechanism comprises a loop having an internal surface defining a channel through which the suture may pass, and an inserting plug which is insertable into the channel The inserting plug has an external surface, wherein the suture is clamped between the internal surface of the loop and the external surface of the inserting plug. 
     In another modified embodiment, flat suture is utilized, and the pressure locking mechanism comprises a pin and a pair of flexible arms for supporting the pin, a gap being formed adjacent to said pin for receiving the suture. 
     In yet another aspect of the invention, there is disclosed a method for securing together two spaced bodily tissues with a surgical tensioning device comprising a resilient member and a pressure locking device. The method comprises a step of routing one end of a length of suture through both spaced bodily tissues and inserting the suture end into and through the pressure locking device. The suture is then tensioned by pulling on the suture end passing through the pressure locking device. Then the pressure locking device is actuated responsive to changes in tension in the suture by moving at least one surface in the pressure locking device to clamp the suture in position. 
     The invention, together with additional features and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying illustrative drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view illustrates one representative embodiment of the device of the present invention; 
         FIG. 2  is an enlarged view of the locking tension device of the embodiment of  FIG. 1 ; 
         FIG. 3  is a view similar to  FIG. 1 , illustrating a modified embodiment of the present invention, as used to approximate two tissue portions; 
         FIG. 4  is a detail view of portion A of  FIG. 3 ; 
         FIG. 5  is a detail view similar to  FIG. 4 , illustrating the pressure lock of the embodiment of  FIGS. 3-4  in a fully assembled state; 
         FIG. 6  is a cross-sectional view illustrating the pressure locking function achieved by the embodiment of  FIGS. 3-5 ; 
         FIG. 7  is an isometric view of another modified embodiment of the invention; 
         FIG. 8  is a detail view of portion B of  FIG. 7 ; and 
         FIG. 9  is a cross-sectional view detailing the pressure locking function achieved by the embodiment of  FIGS. 7 and 8 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now more particularly to the drawings, there is shown in  FIGS. 1-2  one embodiment of a knotless dynamic suturing device  10  which is constructed in accordance with the principles of the present invention. The device  10  is constructed to utilize a single surface to impart a locking pressure on a length of suture, and comprises a resilient member or spring  12 , which is generally shaped like the letter “U”, with a base portion  14  and upstanding legs  16 ,  18 . Each upstanding leg includes, at its end distal to the base portion  14 , respective attachment points  20  and  22 . Each attachment point  20 ,  22  may comprises a loop, hook or pressure locking mechanism as shown. 
     A length of suture  24  is attached to the attachment point  20  at one end thereof, as shown, to thereby attach the suture  24  to the spring  12 . The suture  24  is first woven or stitched into and through tissue with suture end  26  leading the way. A needle may be used to route the suture through tissue. Then, suture  24  is routed into attachment point  22 , which comprises a pressure locking mechanism, using the suture end  26 . The suture is then brought into tension by pulling on the suture end  26 . As the suture  24  is put into tension, two concurrent movements are realized. First, the tissue portions to be approximated are brought to their desired positions, in approximation to one another, and second, the legs  16  and  18  of the device  10  flex apart to store the energy needed in the spring&#39;s bridge or base  14 , in order to supply continuing tension to the suture, thus keeping the tissue in compression while it heals. 
     The locking pressure device  22  is fabricated of a tubular material. The pressure is derived by collapsing the tubular walls onto suture  24  by means of an external device. Preferably, this external device comprises a crimping tool, but any suitable tool could be used by the practitioner, at a time during the procedure when the practitioner is ready to lock the suture in place. Collapsing the tubular walls permanently distorts the tube at point  28 , such that it permanently locks the suture within a lumen  30  of the tube. Thus, the single surface utilized to pressure lock the suture in place is the internal cylindrical wall of the tube  22 . The material utilized to fabricate the legs  16 ,  18  and the base portion  14  of the spring  12  must be sufficiently resilient to supply the energy storage needed for the inventive device to properly function. The material utilized to fabricate the tube  22  must be sufficiently compliant so as to conform and form around the suture  24 . Should both of these materials (for fabricating the spring  12  and tubular pressure locking mechanism  22 ) be the same, the temper of the material would still be different in order to provide the desired properties. Preferably, the entire device is made of spring tempered stainless steel or titanium, with the locking pressure device  22  being fully annealed to be sufficiently compliant. 
       FIGS. 3-6  illustrate a modified embodiment of the present invention, having a pressure locking device which utilizes two surfaces to pressure lock the suture into place. In this embodiment, like elements to those in the  FIGS. 1-2  embodiment are designated by like reference numerals. Thus, in  FIG. 3 , there is shown a device  32  that is designed to utilize two surfaces to generate the locking pressure on the suture  24 . The device  32  comprises a pressure locking mechanism  34 , comprising a loop, and an inserting plug  36 .  FIG. 3  shows tissue  38  with a lesion  40  being approximated by the device  32 . This application is similar for all three illustrated embodiments, though other applications are appropriate as well. Suture  24  has been routed around tissue  38  and inserted with suture end  26  into the pressure locking mechanism  34 . The suture  24  is then brought into tension by pulling on the suture end  26 . As tension is brought onto the suture, two concurrent movements are realized. First, the tissue  38  is brought to its desired position, and second, legs  16  and  18  flex apart to store the energy needed in the spring&#39;s base or bridge  14  to supply continuing tension to the suture, thus keeping the tissue in compression while it heals. The loop  34  includes a channel defined by an inner surface  42 , through which the suture passes. 
     The locking pressure is generated by inserting the plug  36 , which comprises an external surface  44 , into the interior of the pressure locking mechanism  34 , and squeezing the suture  24  between surfaces  42  and  44 .  FIG. 6  illustrates a cross-section of the suture  24  squeezed in the interface between surfaces  42  and  44 . Either of the surfaces  42 ,  44  may be textured in order to increase the friction on the lock. In this embodiment, as illustrated, surface  44  is textured, so that the plug  36  is pulled in to the interior of the pressure locking mechanism  34  by the tension in the suture  24 .  FIG. 5  shows the pressure locking mechanism  34  in a fully assembled state. 
     A third embodiment of the inventive concept is shown in  FIGS. 7-9 . In this embodiment, pressure is again used to lock the suture, but also, significant frictional resistance is employed while tensioning. This knotless dynamic suturing device  50  is represented in  FIG. 7 , with  FIG. 8  detailing the pressure lock and  FIG. 9  showing a cross-section of the detailed interface of  FIG. 8 . While the invention is not constrained to flat suture, the embodiment  50  makes use of flat or tape suture  52 . Flat suture is preferred in situations where the high tensions in the suture require that broad contact is ensured between the suture and the tissue. This broad contact distributes the tension in the suture over a broad area, thus preventing the tension in the suture from damaging tissue. This is an especially important feature when dealing with patients with known poor bone quality, such as diabetic and osteoporotic patients. 
     As in the above described prior embodiments, the suture  52  is connected to a spring  54  at an attachment point or first suture end  56 . A second suture end  58  is routed through the tissue with a needle (not shown), and back to an attachment point  60  where it is routed around a pin  62 . Pin  62  is able to float on a pair of flexible arms  64  to permit suture to pass between the pin  62  and a spring surface  66  ( FIG. 9 ). As tension is applied to the second suture end  58 , and the tissues are brought into compression, spring loops  68  on the spring  54  distend storing energy that will supply substantially constant compression during the tissue healing cycle. Applying tension to the second suture end  58  also pushes the pin  62  away from the spring surface  66 , thereby decreasing the pressure on the suture in that interface. When tension is released on the second suture end  58 , the predominate suture tension shifts to the other side of the pin at point  72 , thus effectively pushing the pin  62  into the spring surface  66 . This action supplies the pressure needed to lock and hold the suture in place. 
     Accordingly, although exemplary embodiments of the invention have been shown and described, it is to be understood that all the terms used herein are descriptive rather than limiting, and that many changes, modifications, and substitutions may be made by one having ordinary skill in the art without departing from the spirit and scope of the invention, which is to be limited only in accordance with the following claims.