Abstract:
A surgical instrument ( 10 ) is adapted to contact tissue of a patient, and to provide traction with the tissue in order to inhibit migration of the instrument relative to the tissue. The instrument may include a pair of opposing jaws ( 16, 18 ) with at least one of the jaws ( 16, 18 ) comprising a substrate having a particular surface facing the tissue, and a plurality of discrete elements ( 26, 28 ) disposed on the particular surface for increasing the traction of the instrument relative to the tissue. These discrete elements ( 26, 28 ) may include a multiplicity of granules, bristles, or projections, and may be formed of materials having various properties such as hydrophilic characteristics. The discrete elements in the form of bristles can be oriented too so that the column strength of each bristle provides increased traction in a predetermined direction.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates generally to surgical instruments, and more specifically to surgical instruments which contact tissue and require traction with the tissue to inhibit migration of the instrument.  
           [0003]    2. Discussion of the Prior Art  
           [0004]    Most surgical instruments are intended to contact tissue, but for some instruments the traction developed between the instrument and the tissue is of particular importance. Instruments such as clips, clamps, retractors, stabilizers, and spreaders, for example, are intended to contact tissue and perform some mechanical function on the tissue. In these cases, the ability of the instrument to grip the tissue contacted is of concern. For example, when a clip is applied to a blood vessel with the intent of occluding that vessel, the occlusion is intended to occur at a predetermined location along the vessel. Although little force may be required to pinch and occlude the vessel, there may be a tendency for the clip to slide either axially or laterally along the vessel. Often this results from the back pressure of the blood in the vessel. If the clip slides radially of the vessel, it may fall off the vessel, leading to unintended blood flow. If the clip slides axially along the vessel, it will leave the predetermined location where the occlusion was intended.  
           [0005]    The sliding of instruments relative to tissue is complicated by the fact that the tissue is typically covered with a body fluid, such as blood. As a consequence, the coefficient of friction between the tissue and the instrument tends to be relatively low.  
           [0006]    In the past, clips and clamps have been provided with soft jaw inserts in order to reduce trauma to the conduit being occluded. For the most part, these inserts have been formed of a compliant material such as foam, and provided with a generally flat surface. The traction tending to hold the clip or clamp in place has been dictated by the well known formula for friction: F=μN, where F is the friction force resisting lateral movement, N is the normal force applied perpendicular to the friction force, and μ is the coefficient of friction between the two-surfaces.  
           [0007]    In accordance with this formula, attempts have been made to increase the factor μ by providing inserts which have higher coefficients of friction with tissue. In spite of these efforts, traction has still been a problem since these coefficients cannot be increased significantly without damaging the vessel or other conduit being occluded.  
           [0008]    Individual fibers in the form of loops have been applied to the inserts to improve traction. The traction in this case has relied, at least in part, on a mechanical interlock with the surface of the tissue, or other cohesive/adhesive phenomena.  
           [0009]    As a practical consequence of this concern for traction, clamps have been applied to conduits such as vessels, and closed with a force sufficient to occlude the vessel. Where slippage has occurred, the tendency has been to increase the clamping force. With reference to the foregoing formula for friction, this increases the normal force N thereby increasing the friction or traction force F. Unfortunately, increases in the normal force N are not required for occlusion, which is the primary purpose of the clamp. Furthermore, high normal forces can create damage to a vessel, particularly the fragile endothelial lining of the vessel. What has been required for these surgical instruments is a structure which can provide a significant traction force without damage to the conduit or vessel.  
         SUMMARY OF THE INVENTION  
         [0010]    In accordance with the present invention, various structures are proposed for increasing the traction force without significantly changing the normal or occlusive force. In some cases, the traction force will be greater than the occlusive force, a condition that will be particularly appreciated for some instruments.  
           [0011]    The surfaces providing increased traction will be advantageous in clips and clamps where there are opposing jaws which develop the normal force. Whether the improved traction is provided along one or both of the jaws can be a matter of choice.  
           [0012]    The structures providing increased traction will also be applicable to spreaders where traction is appreciated on outwardly facing surfaces of opposing jaw members. Increased traction can be provided in the form of inserts for the jaws of clips, clamps, and retractors, or may take the form of webs providing a significant area of contact for the stabilization of organs. In the latter device, the normal force would be developed not between opposing jaws but relative to some other stationary structure. For example, a stabilizer might be clamped to the sternum of the patient, or some other skeletal element, in order to provide a traction force against a beating heart in a bypass surgery. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0013]    A vascular clip is illustrated in FIG. 1 and designated by the reference numeral  10 . The clip  10  is merely representative of many surgical instruments that contact tissue, instruments which can benefit from increased traction with the tissue. In addition to the clip  10 , other instruments might include occlusion devices, such as clamps, as well as retractors, stabilizers, and spreaders. In each of these cases, it is desirable to maintain the instrument and the tissue in a generally fixed relationship without damaging the tissue. Thus, traction is of particular importance.  
         [0014]    The clip  10  includes telescoping barrel portions  12  and  14 , each of which is associated with one of a pair of opposing jaws  16  and  18 . These jaws  16 ,  18  are biased into a proximal relationship so that a vessel  20  disposed between the jaws  16  and  18  is occluded. In the case of the clip  10 , the jaws  16  and  18  have opposing surfaces  22  and  24 , respectively, which face each other. Since these surfaces  22 ,  24  will typically be formed of a hard plastic material, it is common to cover the surfaces  22  and  24  with a soft, compliant material or pad  26  and  28  having a tissue-contacting surface  30  and  32 , respectively.  
         [0015]    In the past, these pads  26 ,  28  have reduced trauma to the vessel  20  but due to their smooth tissue-contacting surfaces  30 ,  32  have commonly provided little traction to resist migration of the clip  10 . The present invention appreciates the need to reduce trauma to the vessel  20 , but also, importantly, to resist migration of the tissue-contacting instrument. The concept is well-suited to instruments that have opposing jaws such as clips, clamps, and retractors. In those instruments, the concept is advantageous whether the tissue-contacting surfaces face each other as is the case with clips, clamps, and retractors, or whether the tissue-contacting surfaces face away from each other as is the case with spreaders. The concept is also advantageous whether both or only one of the opposing surfaces provides the increased traction. In some instruments, such as stabilizers, a single web providing a wide area of contact can benefit from the improved traction.  
         [0016]    One embodiment of a tissue-contacting instrument with improved traction is illustrated in FIG. 2 where the jaw  18  is provided with the pad  28  having the tissue-contacting surface  32 . In this embodiment, a multiplicity of granules  34  are disposed on the surface  32  in order to provide an irregular surface with increased traction. These granules  34  may be formed of sand or silica, or any other material providing an abrasive surface. These granules  34  are disposed to extend at least partially above the surface  32  in order to increase the coefficient of friction between the pad  28  and the tissue. It is believed that these granules  34  provide a mechanical interlock with the tissue thereby increasing the traction force and decreasing the possibility of migration.  
         [0017]    The granules  32  will typically be formed of a relatively hard material , such as plastic or metal, and can be either applied by adhesive or otherwise molded into the surface  32 . The granules  34  could similarly be applied directly to the jaw surface  24  in the absence of the pad  28 . Thus, the irregular surface formed by the granules  34  provides a traction force which inhibits slippage of the clamping device, such as the clip  10 , relative to the tissue, such as the vessel  20 . The granules  34  may be provided with a coating which is hydrophilic. An anticoagulant, such as Heparin, may also be used as a coating.  
         [0018]    In the embodiment of FIG. 3, a mesh  36  is disposed over the tissue-contacting surface  32 . In this case, the soft pad  28  forms a base for the mesh  36 . The filaments forming the mesh  36  provide the tissue-contacting surface  32  with a rough, irregular configuration which varies with the thickness of the filaments. In the interstices of the mesh  36  where there are no filaments, the surface  32  has a thickness of zero. Where one filament overlies the surface, the mesh has the thickness of a single filament. And where the filaments overlap, the mesh  36  provides a thickness equivalent to twice the filament diameter. These variations in thickness enable the mesh  36  to grip the tissue, such as the vessel  20 , to increase the traction force opposing slippage of the instrument. The mesh  36  can be formed of plastic or metal, and the mesh pattern can have any number of elements per square inch. The filaments forming the mesh pattern can be disposed at a right angle to each other, or at any other angles as desired. Typically, the mesh  36  will be attached to the pad  28  by an adhesive or by way of mechanical attachment such as an overmold procedure. The mesh  36  could be similarly attached directly to the jaw  18  and coated in the manner previously discussed.  
         [0019]    The provision of bristles  38  on or in the pad  28  can also improve traction as illustrated in the embodiments of FIGS. 4 and 5. In the embodiment of FIG. 4, the bristles  38  are molded directly into the plastic jaw  18 . In this molding process, the bristles  38  can be individually molded into the jaw  18  or clumped together in groups of bristles  38  in the manner commonly associated with a toothbrush. The bristles can be upstanding in the manner best illustrated in FIG. 5. Where the bristles  38  contact tissue such as the vessel  20 , they tend to axially crumple to develop an occlusive force. Laterally of the vessel  20 , the bristles  38  resist slippage or movement of the vessel  20  relative to the instrument. FIG. 5 also illustrates that the bristles  38  can be molded into the atraumatic pads  26  and  28 . The bristles  38  will commonly be formed from polyethylene or nylon. They may also be provided with bulbs or enlargements  40  on their ends as illustrated in FIG. 6. This configuration will further reduce trauma to the tissue or vessel  20 . The bristles  38  can be coated in the manner previously discussed.  
         [0020]    [0020]FIG. 7 illustrates an embodiment where the bristles  38  are slanted to oppose movement of the jaw  18  along the axis of the conduit of vessel  20 . Thus, the bristles  38  include a group  42  which is slanted to the right in FIG. 7 to oppose movement of the vessel  20  to the left. Similarly, a group  43  of the bristles  38  are slanted to the left to oppose movement of the vessel  20  to the right. Alternatively, the two groups  42  and  43  can be intermingled along the entire surface  32  of the pad  28  as illustrated in FIG. 8.  
         [0021]    In the embodiment of FIG. 9, multiple clumps of the bristles  38 , designated by reference numerals  45 ,  47 , and  49 , can be provided on the jaws  16 ,  18  with or without an opposing group of the bristles  38 .  
         [0022]    [0022]FIGS. 10 and 11 illustrate a further embodiment where the bristles  38  are disposed in individual channels formed in the soft pad  28 . Each of these channels is preferably provided with a diameter greater than that of the associated bristles  38  so that the clamping pressure initially compresses the foam pad  28  in order to contact the bristles  38 . Further compression of the pad  28  will tend to form a mechanical interlock between the bristles  38  and the vessel  20 , as shown in FIG. 11. As was the case with the mesh embodiments, the bristle embodiments can be formed by overmolding the bristles  38  with the pad material.  
         [0023]    [0023]FIG. 12 illustrates a further embodiment where the pad  28  is covered with a non-woven, wool-like material  53  is forming multiple loops. The loops can be continuous rather than discrete as is the case with the hook-and-loop configuration of the past. In such an embodiment, the wool-like material  53  is preferably provided with a soft configuration in order to enable the fiber to contour around the tissue or vessel  20 . The fibers of the wool must nevertheless be sufficiently rigid to resist movement relative to the tissue or vessel  20 . The resulting fibrous material can be bonded to the jaw  18  or pad  28 . Alternatively, the pad  28  can be insert molded against the fibrous surface of the wool-like material  53 . The fibrous material  53  can be coated in the manner previously described.  
         [0024]    The pads or inserts  26 ,  28  can also be molded to form multiple projections  55  arranged in a waffle pattern, such as that illustrated in FIGS. 13 and 14. Within the pattern, projections  55  can be the same, similar, or widely different. Some projections will have a common, cross-sectional shape throughout their entire length. Other projections may extend to a point or reduced cross-sectional area as would be the case with a pyramid shape. The cross-sectional shape can also vary widely. For example, the projections  55  may have a cross-section that is circular, polygonal, or any irregular shape.  
         [0025]    The projections  55  can also be angled so that in a side view, such as that illustrated in FIG. 14, they have a saw-tooth shape. With this configuration, movement of tissue against the saw teeth would be opposed with a greater force than movement of tissue along the same teeth. In this manner, slippage can be inhibited by high traction in one direction and facilitated by low traction in the opposite direction.  
         [0026]    In FIG. 15, the clip  10  is illustrated with its opposing jaws  16 ,  18  and associated atraumatic pads  26 ,  28 . In this case, the pads  26 ,  28  are formed of a hydrophilic material, such as expanded polyethylene. This material directly contacts the moist tissue, such as the vessel  20 , and withdraws moisture from the tissue, leaving a dryer surface and a resulting higher coefficient of friction between the tissue or vessel  20  and the pads  26 ,  28 . With a higher coefficient of friction, slippage of the clip  10  on the vessel  20  is substantially inhibited without an increase in the occlusive force applied by the jaws  16 ,  18 . These hydrophilic properties can also be achieved by coating the pads  26 ,  28  with a hydrophilic material.  
         [0027]    Although the foregoing embodiments providing increased traction have been disclosed primarily with respect to clips and clamps, it will be apparent that many other embodiments of the invention can be equally advantageous as in the case of a retractor  57 , illustrated in FIG. 16, and a spreader  59  illustrated in FIG. 17. As was the case with the occlusion instruments, such as the clip  10 , the retractor  57  of FIG. 16 includes opposing jaws  16 A and  16 B with jaw surfaces  22 A and  24 A which face each other. These surfaces  22 A,  24 A can be provided with pads  26 A,  28 A, or otherwise coated or structured in accordance with any of the foregoing embodiments.  
         [0028]    Referring now to FIG. 17, it will be noted that the spreader  59  also includes opposing jaws  16 B and  18 B. However, in this embodiment, the jaw surfaces face outwardly rather than toward each other. Thus, in the case of the spreader  59 , the traction-increasing structures, such as pads  26 B and  28 B, face outwardly of the respective jaws  16 B and  18 B.  
         [0029]    A stabilizer is illustrated in FIG. 18 and designated by the reference numeral  61 . This stabilizer  61  includes a web  63  which is stretched between opposing areas of a plastic support  64 . The web  63  can be formed from any of the high-traction materials previously discussed. In operation, this web  63  is held against an organ, such as a beating heart  65 , in order to stabilize or otherwise hold the organ in a generally fixed location during surgery.  
         [0030]    In all of the foregoing embodiments, the surgical instrument, such as the clip  10 , is provided with a structure which increases the coefficient of friction with the tissue, or otherwise develops a mechanical interlock with the tissue so that slippage of the instrument is inhibited. In all cases, the structure can be coated with a thrombogenic, hydrophilic, or similar materials in order to facilitate the objectives of the instrument. Whether the fraction structure is provided on one or both of an opposing pair of jaws, as in the case of the clip  10 , or formed as a single element as in the case of the stabilizer  61 , it will increase traction between the instrument and the tissue in order to inhibit relative movement therebetween.  
         [0031]    It will be understood that many other modifications can be made to the various disclosed embodiments without departing from the spirit and scope of the concept. For example, various sizes of the surgical device are contemplated as well as various types of constructions and materials. It will also be apparent that many modifications can be made to the configuration of parts as well as their interaction. For these reasons, the above description should not be construed as limiting the invention, but should be interpreted as merely exemplary of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the present invention as defined by the following claims.