the inserts of this invention may be mounted onto various surgical instruments to minimize trauma to tissues or organs that are manipulated , e . g ., grasped , clamped , retracted , retained or immobilized by the instrument . examples of surgical instruments include , but are not limited to , clamps , clips , forceps , graspers , retractors and stabilizers , as well as other instruments generally designed to grasp , retain , immobilize , contact or otherwise engage tissue or bodily organs . instruments equipped with these inserts provide atraumatic traction on tissues or organs without having to increase the clamping or resistive force on the tissue or organ . hooked traction elements employed on inserts according to the invention differ in many ways from traditional woven , cut loop hook fasteners sold , for example , under the brand names velcro ™ ( part nos . hook # 65 and hook # 88 , velcro usa , inc ., manchester , n . h .) and scotchmate ™ ( part no . sj - 3401 , minnesota mining and manufacturing co ., st . paul , minn .). for example , in certain variations of the invention , the hooked traction elements are molded , rather than woven . the traction elements may be fabricated by known techniques , such as injection molding and compression molding , and as specifically described in u . s . pat . nos . 3 , 594 , 865 and 3 , 594 , 863 to erb ; u . s . pat . no . 4 , 794 , 028 to fischer ; u . s . pat . no . 5 , 260 , 015 and 5 , 518 , 795 to kennedy et al . ; and u . s . pat . no . 6 , 187 , 247 to buzzell et al . also , the hooked traction elements of the invention and are also relatively smaller in height and can be arrayed at much higher densities on surface regions of the inserts , as compared to conventional woven , cut loop hook fasteners . the hooked traction elements are formed to have at least one stem extending from the insert tissue contacting surface , and at least one head or lateral extension extending from the stem . as described above , the hooked traction elements are typically configured as hooks , with the term “ hooks ” encompassing a variety of shapes known in the art , including but not limited to , e . g ., hooks with a single crook , twin crooks , a flat top , a mushroom - type shape , and the like . suitable hook shapes are described in u . s . pat . no . 3 , 192 , 589 to pearson ; u . s . pat . no . 3 , 408 , 705 to kayser et al . ; u . s . pat . no . 4 , 290 , 174 to kalleberg ; u . s . pat . nos . 4 , 984 , 339 and 6 , 526 , 633 to provost et al . ; u . s . pat . no . 5 , 315 , 740 to provost ; u . s . pat . no . 5 , 339 , 499 to kennedy et al . ; u . s . pat . no . 5 , 664 , 301 to akeno ; u . s . pat . no . 5 , 679 , 302 to miller et al ; and u . s . pat . no . 5 , 845 , 375 to miller et al . commercially available fastening materials can provide a source of traction elements . fastener materials found on disposable absorbent articles such as described in u . s . pat . nos . 4 , 846 , 815 and 5 , 019 , 065 to scripps ; u . s . pat . no . 4 , 963 , 140 to robertson et al . ; and u . s . pat . no . 5 , 318 , 555 to siebers et al . may also provide sources of traction elements . traction element dimensions may vary , but usually the height of each traction element will be chosen to be about 1 mm ( about 0 . 04 inches ) or less . in certain variations , the height can be about 0 . 8 mm ( about 0 . 03 inches ) or less , or about 0 . 5 mm ( about 0 . 02 inches ) or less , or about 0 . 4 mm ( about 0 . 015 inches ) or less , or about 0 . 3 mm ( about 0 . 01 inches ) or less . as a comparison , fibra ™ clamp inserts ( applied medical , rancho santa margarita , calif .) are covered with a woven layer of flexible , soft , finger - like nylon fibers that closely resembles traditional woven , cut loop hook fasteners ; the hook shaped fibers are approximately 1 . 5 mm ( about 0 . 060 inches ). the density of the traction elements per unit area of the contact surface region or regions on the insert containing the traction elements will also vary with such factors as the overall configuration of the element , the particular shape , orientation , and width or diameter of element stems or heads , and the distance between elements . in general , traction element dimensions and densities will also vary by the manufacturing parameters and processes employed . however , a density of at least about 100 elements per square centimeter is desirable . in certain variations , densities of at least about 130 elements , or at least about 160 elements , or at least about 200 elements , or at least about 230 elements , or at least about 260 elements , or at least about 300 elements per square centimeter is desirable . again as a comparison , fibra ™ clamp inserts ( applied medical , rancho santa margarita , calif .) are covered with a woven layer of flexible , soft , finger - like nylon fibers that closely resembles traditional woven , cut loop hook fasteners , and that are arranged at a density of about 62 hook shaped fibers per square centimeter . fig1 a - 1c show traction elements according to one aspect of the present invention . in fig1 a , traction element 100 has a head 102 and stem 104 . the height ( h ) of each traction element 100 is about 0 . 4 mm . as shown more clearly in fig1 b , the traction elements 100 are configured to have twin crooks 106 . fig1 c shows that the traction elements 100 are arranged such that each row is vertically and horizontally offset from one another . the traction elements are arranged at a density of about 130 elements / cm 2 . fig2 a - 2b show traction elements according to another aspect of the invention . as shown in fig2 a , the traction elements 200 also have a head 202 and stem 204 portion . however , instead of a twin crook , the traction elements 200 are configured to have a single crook 205 . in fig2 b and 2c , the horizontal rows of traction elements 200 are shown to be spaced closer than those in fig1 b and 1c . the traction elements are arranged at a density of about 260 elements / cm 2 . fig3 a - 3c show traction elements according to yet another aspect of the invention . in this aspect , the traction elements 300 have a disc - shaped head 302 that is generally flat , but which may also be slightly concave , and a stem 303 . the shape of the heads 302 is more clearly depicted in fig3 b . the height of the traction elements 300 is about 0 . 3 mm ( about 0 . 01 inches ). the diameter of the heads 302 is about 0 . 4 mm ( about 0 . 015 inches ). in fig3 b and 3c , the horizontal rows of traction elements 300 are shown to be uniformly spaced apart . the traction elements are arranged at density of about 300 elements / cm 2 . the traction elements may be made from a variety of thermoplastic or thermosetting polymers such as polyethylene , polypropylene , nylons , melamine , polystyrenes , polycarbonates , various fluorinated polymers , epoxy resin , cellulose acetate , vinyl chloride polymers , and copolymers or blends thereof , such as described in u . s . pat . no . 3 , 408 , 705 to kayser et al . ; u . s . pat . no . 3 , 594 , 865 to erb ; u . s . pat . no . 4 , 963 , 140 to robertson et al . ; and u . s . pat . no . 6 , 526 , 633 to provost et al . inserts according to the invention can be formed of a variety of compliant materials known in the art to minimize tissue trauma . for example , elastomeric materials that are compliant and resiliently deflectable are suitable . such elastomeric materials include , but are not limited to , natural rubber , neoprene , urethane , ethyl vinyl acetate foam , silicone , or silicone foam . it is desirable that the material be a thermoplastic elastomer suitable for injection molding such as styrenic based thermoplastic elastomers or other thermoplastic elastomers and , in particular , those available in the 0 - 95 shore a range . the inserts may be attached or affixed to surgical instruments by mechanical bonding , adhesives , direct injection molding onto the instruments , or by other known means . in the case of surgical clamps , such inserts can be bonded or adhered to , or otherwise overmolded onto known attachment structures , including rigid attachment structures , for securement onto surgical clamps . ( see e . g . fibra ™ surgical clamp inserts , applied medical , rancho santa margarita , calif ., model no . g - 8655 ; engage ™ inserts , novare surgical , cupertino , calif ., model no . n - 10103 ). alternatively , the insert can be secured to a surgical instrument , e . g ., a clamp jaw , by means described in u . s . pat . nos . 6 , 228 , 104 , 6 , 273 , 902 , and 6 , 387 , 112 , each commonly owned by the assignee of the present application and incorporated herein in its entirety . briefly , such means include a flexible elongate attachment member configured to be received in an elongate cavity or channel that extends longitudinally of a clamped jaw . such attachment members can be formed of a plastic that is flexible but generally stiffer and markedly less deflectable than the insert material . suitable materials include nylon or polypropylene . such a design is especially advantageous in that the resulting insert can accommodate a variety of jaw shapes and configurations , including curved jaws . inserts according to the present invention and having such attachment members are depicted in fig4 - 8 . in the case of surgical clips , such inserts can be overmolded directly onto the clip jaw or can otherwise be attached or bonded to the clip jaw through known methods . in some instances , it may be desirable to form the insert overmold from a single elastomer . however , more than one overmold may be made . as depicted in fig9 a - 9d , a second overmold 508 made from an elastomer having a shore durometer rating of about 2 a to about 95 a is molded over a more rigid , but still flexible first overmold 510 made from an elastomer having a shore durometer rating of about 20 a to about 95 a . the inserts may also be formed to have a level surface or one or more wells . furthermore , the inserts may be injection molded directly onto surgical instruments , or may otherwise be affixed to them by mechanical bonding , adhesives , or other known means . for example , fig1 a and 10b depict stabilizer 910 with insert 902 affixed to stabilizing arm 906 of the stabilizer . as shown , insert 902 includes traction elements 900 similar to those depicted in fig1 a - 1c . the traction elements may be integrally molded with the insert or if provided on sheets or strips of a polymer material , placed onto the inserts by methods including , but not limited to , e . g ., ultrasonic welding , heat bonding , or bonding with a number of available adhesives such as urethanes , epoxies , cyanoacrylates and pressure - sensitive adhesives . when supplied on sheets or strips , the traction elements will usually be cut out into various strips or patterns and then placed on the inserts . if the insert has been provided with a recessed region or regions , the cut out patterns may be laid in such region ( s ). in addition , the traction elements may be patterned on the inserts in repeating or non - repeating shapes , such as rectangles , circles , ovals , diamonds , and the like . connecting arms or spines of narrower width may or may not be included to connect the individual shapes . the shapes may also be placed upon the inserts such that they are touching one another or spaced apart from one another . for example , in one aspect , as illustrated in fig4 a , continuous strip 402 of uniform width with traction elements 400 has been cut out and placed on insert 404 . as further depicted in fig4 b , strip 402 may lie in recessed region 406 formed in insert 404 . fig5 a and 5b show another variation of the traction element pattern . in this variation , the sheet or strip of traction elements has been cut to form rectangles 500 . the rectangles 500 are connected to each other by spines 502 of narrower width . these spines of narrower width improve the lateral flexibility of the insert . rectangles 500 and spines 502 are cut as a unit from the sheet or strip of traction elements , i . e ., they are not separate pieces applied to the insert . fig6 a - 6d show traction elements 600 placed in a circular pattern on insert 602 . the diameter of each circle 604 is about 2 to about 2 . 5 mm . in fig6 a - 6b , circles 604 are spaced about 3 to about 4 mm apart . in fig6 c - 6d , circles 604 are spaced about 6 to about 10 mm apart . fig7 a - 7b show traction elements 700 placed in repeating oval patterns on insert 702 . ovals 704 are about 5 mm long and about 2 . 5 mm wide . each oval 704 is spaced about 2 to about 3 mm apart . fig8 a - 8b show traction elements 800 placed in a touching diamond pattern on the insert 802 . diamonds 804 are about 2 . 5 to about 3 mm in length and about 2 . 5 to about 3 mm in width . the traction elements may also lie at varying positions relative to the level surface of the insert . for example , as mentioned , sheets , strips , or other patterned regions can be applied to insert contact surfaces , either into a flat contact surface of the insert , or into preformed , recessed regions of the insert that lie below the surface level of the insert . examples of the latter scenario are depicted in fig9 a - 9d . a cross - sectional view of the insert taken at line 5 - 5 ( fig5 a ) shows traction elements 504 extending partially above the surface level of insert 506 ( fig9 a ). the traction elements 504 may also further extend from surface level 506 ( fig9 b ), or lie level with the surface level of insert 506 ( fig9 c ), or lie below level surface 506 ( fig9 d ). the invention will be better understood by reference to the following examples , which are offered by way of illustration only and not by way of limitation . surgical clamps containing jaw inserts according to the present invention were tested against known surgical clamps and jaw insert systems , and respective traction capabilities were measured . the surgical clamps clips were applied to porcine aortas that were pressurized to a blood pressure between 100 mmhg to 155 mmhg . the vessels were coated with whole milk at room temperature to lubricate the vessels , in order to simulate the condition of the vessels in the surgical field ( in which blood vessels are typically covered on their outer surfaces by blood ). previous studies indicate that porcine vessels lubricated with whole milk closely match the physical properties of human cadaver vessels lubricated with actual blood . this system is thus a close approximation of actual surgical conditions . the various inserts tested varied in their attachment mechanisms , and therefore different styles of surgical clamps that accommodated the various inserts were used accordingly . in each case , however , the clamping force applied to the vessel was between 5 - 6 lbf . more particularly , the applied force was measured with a force gauge and a fixture that kept the jaws maintained at a jaw spacing of 4 mm , which closely mimics conditions for clamping an aorta ( average aorta wall thickness approximately 2 mm ). therefore the same clamping force was consistently applied across all the insert systems . to measure the tractive force imparted by each respective insert , each clamp was pulled radially ( i . e ., perpendicular to the axis of the vessel ) off the clamped vessel a total of four times at a constant speed of 4 inches / minute , and the maximum tractive force exerted on the clamp to accomplish such radial movement during the process was recorded . the maximum force exerted was considered indicative of the tractive force applied by the inserts to the engaged vessel . insert type 1 . inserts of foam overlaid with a woven layer of finger - like nylon projections available under tradename fibra ™ surgical clamp inserts ( applied medical , rancho santa margarita , calif ., model no . g - 8655 ). these inserts were attached to an applied medical 86 mm - 0 ° surgical clamp ( applied medical , rancho santa margarita , ca , model no . a3312 ). insert type 2 . inserts of a compliant , elastomeric pad molded onto a semi - rigid plastic base available under tradename intrack ™ double traction inserts ( novare surgical , cupertino , calif ., model no . n - 10146 ), secured to an intrack ™ clamp ( novare surgical , cupertino , calif ., model no . n - 10136 ). the inserts have a surface with repeating pyramid shapes . insert type 3 . steel - jawed clamp without any insert , aesculap ™ clamp ( aesculap ag , center valley , pa ., model no . fb532r - 2007 ). insert type 4 . inserts formed of an elastomer and including molded , hooked traction elements according to the invention . the inserts include a continuous strip of uniform width of molded , hooked traction elements ( velcro 830 / 833 , velcro usa inc ., manchester , n . h .) secured to the insert surface , as depicted in the embodiment of fig4 a - 4b . the molded , hooked traction elements have the general shape and orientation , and are generally arrayed , as shown fig2 a - 2c . the inserts were secured to an intrack ™ clamp ( novare surgical , cupertino , calif ., model no . n - 10136 ). insert type 5 . inserts formed of an elastomer and including molded , hooked traction elements according to the invention . the inserts include a series of circle patterns of molded , hooked traction elements ( ripngrip 2002 hm , ripngrip industries inc ., palmdale , calif .) secured to the insert surface , as depicted in the embodiment of fig6 a - 6b . the molded , hooked traction elements have the general shape and orientation , and are generally arrayed , as shown fig1 a - 1c . the inserts were secured to an intrack ™ clamp ( novare surgical , cupertino , calif ., model no . n - 10136 ) insert type 6 . inserts similar to those of insert type 5 formed of an elastomer and including molded , hooked traction elements according to the invention . the inserts include a series of circle patterns of molded , hooked traction elements ( ripngrip 2002 hm , ripngrip industries inc ., palmdale , calif .) secured to the insert surface , as depicted in the embodiment of fig6 c - 6d ( the circles are spaced further apart than those of insert type 5 ). the molded , hooked traction elements have the general shape and orientation , and are generally arrayed , as shown fig1 a - 1c . the inserts were secured to an intrack ™ clamp ( novare surgical , cupertino , calif ., model no . n - 10136 ). insert type 7 . inserts formed of an elastomer and including molded , hooked traction elements according to the invention . the inserts include a series of oval patterns of molded , hooked traction elements ( velcro 830 / 833 , velcro usa inc ., manchester , n . h .) secured to the insert surface , as depicted in the embodiment of fig7 a - 7b . the molded , hooked traction elements have the general shape and orientation , and are generally arrayed , as shown fig2 a - 2c . the inserts were secured to an intrack ™ clamp ( novare surgical , cupertino , calif ., model no . n - 10136 ). insert type 8 . inserts formed of an elastomer and including molded , hooked traction elements according to the invention . the inserts include a continuous strip of with alternating segments of narrow and corresponding wider widths of molded , hooked traction elements ( ripngrip 2002 hm , ripngrip industries inc ., palmdale , calif .) secured to the insert surface , as depicted in the embodiment of fig5 a - 5b . the molded , hooked traction elements have the general shape and orientation , and are generally arrayed , as shown fig1 a - 1c . the inserts were secured to an intrack ™ clamp ( novare surgical , cupertino , calif ., model no . n - 10136 ). insert type 9 . inserts formed of an elastomer and including molded , hooked traction elements according to the invention . the inserts include a series of diamond - shaped patterns of molded , hooked traction elements ( velcro 830 / 833 , velcro usa inc ., manchester , n . h .) secured to the insert surface , as depicted in the embodiment of fig8 a - 8b . the molded , hooked traction elements have the general shape and orientation , and are generally arrayed , as shown fig2 a - 2c . the inserts were secured to an intrack ™ clamp ( novare surgical , cupertino , calif ., model no . n - 10136 ). insert type 10 . inserts formed of an elastomer and including molded , hooked traction elements according to the invention . the inserts include a continuous strip , hooked traction elements ( obtained from fastener materials on disposable absorbent articles sold under the brand name ultra comfort ™, kroger co ., cincinnati , ohio ) secured to the insert surface . the molded , hooked traction elements have the general shape and orientation , and are generally arrayed , as shown fig3 a - 3c . the inserts were secured to an intrack ™ clamp ( novare surgical , cupertino , calif ., model no . n - 10136 ). the results of the radial pull tests are indicated in table i below , including individual recorded pull off forces , and average pull - off force , for each insert type . * maximum load on the measuring force gauge was 10 lbf , and a result of 10 + indicates that the test was stopped when 10 lbf was reached . therefore , for inserts giving a trial result of 10 +, the average pull - off force could be higher than that calculated . the results of the clamp pull - off tests indicate that the inserts according to embodiments of the present invention , i . e ., insert types 4 - 10 , provide more traction than known insert types 1 and 2 , specifically , over 2 - 3 times more tractive force , depending on the insert . furthermore , many of these inserts provided for a tractive force that met or exceeded that supplied by a conventional steel jawed clamp ( average 7 . 7 lbf ). it was previously unexpected that atraumatic inserts could achieve the degree of traction found with conventional steel jaw clamps . surgical clips containing jaw inserts according to the present invention were tested against known surgical clips , and respective traction capabilities were measured , according to the methods described above in example 1 . the surgical clips tested were of the parallel - jaw , spring clip variety . the clamping force exerted by each tested clip ranged from 0 . 85 - 1 . 00 lbs . ( full force ). again , the attached clips were radially pulled off the vessel at a constant speed and the maximum force exerted on the clamp during the process was recorded . the maximum force exerted is considered indicative of the tractive force applied by the inserts to the engaged vessel . insert type a . soft jaw inserts of foam overlaid with a woven layer of finger - like nylon projections ( fibra ™ surgical clip , applied medical , rancho santa margarita , calif ., model no . g - 6050 ). insert type b . elastomeric soft jaw inserts having integrally formed repeating ridges extending across the width of the insert surface , with the ridges being approximately 0 . 007 inches high and 0 . 010 inches wide , as further described in u . s . application ser . no . 10 / 349 , 871 , filed jan . 22 , 2003 , and incorporated herein in its entirety . ( greyhound , novare surgical , cupertino , calif ., model no . n - 10157 ) insert type c . inserts formed of an elastomer and including molded , hooked traction elements according to the invention . the inserts include a continuous strip of uniform width of molded , hooked traction elements ( velcro 830 / 833 , velcro usa inc ., manchester , n . h .) secured to the insert surface . the molded , hooked traction elements have the general shape and orientation , and are generally arrayed , as shown fig2 a - 2c . the inserts were secured to a greyhound style surgical clip , in substitution of the conventional insert surface ( greyhound , novare surgical , cupertino , calif ., model no . n - 10157 ) insert type d . soft jaw inserts of natural sponge rubber with smooth surface , and an interior cavity running the length of the insert ( fogarty softjaw ™ spring clip , edwards life sciences , irvine , calif ., model no . csoft6 ) the results of the radial pull tests are indicated in table ii below , including individual recorded pull off forces , and average pull - off force , for each insert type . the results of the clip pull - off tests indicate that the surgical clips with type c inserts provide 9 times more traction than type a inserts , 3 times more traction than type b inserts , and approximately 4 . 5 times more traction than type d inserts . all publications , patents , and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes to the same extent as if each individual publication , patent , or patent application were specifically and individually indicated to be so incorporated by reference . although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding , it will be readily apparent to those of ordinary skill in the art in light of the teachings of this invention that certain changes and modifications may be made thereto without departing from the spirit and scope of the appended claims .
compliant inserts for surgical instruments having improved traction are provided . the clamping surface of the inserts includes a plurality of short and densely arranged traction elements . the tractive force supplied by the traction elements approaches that of steel jawed clamps .