as required , detailed embodiments of the present invention are disclosed herein ; however , it is to be understood that the disclosed embodiments are merely exemplary of the invention , which may be embodied in various forms . therefore , specific structural and functional details disclosed herein are not to be interpreted as limiting , but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure . referring to the drawings in more detail , the reference numeral 1 generally designates an embodiment of a flexible forceps apparatus with improved torsional rigidity according to the present invention . the apparatus 1 is inserted through a flexible endoscope instrument 3 ( fig4 ) for grasping structures within an endoscopic , arthroscopic , laparoscopic , or similar type of surgical site . the forceps apparatus 1 generally includes a proximal handle section 8 , an elongated cable assembly 10 , and a distal tip section 12 including a pair of opposed forceps jaw members 14 . referring to fig1 , the illustrated handle section 8 includes an elongated rod shaped handle frame 18 terminating proximately in a thumb ring 20 . an operating spool 22 is slidably mounted on the frame 18 and has an attachment post assembly 24 including a set screw extending through an elongated slot 26 formed through a section of the frame 18 . a proximal end of a jaws operating cable 30 is attached to the post 24 by means of the set screw . a proximal end of a tubular cable sheath 32 of the cable assembly 10 is secured to a distal end of the handle frame 18 . although not illustrated , the sheath 32 can be formed by a wire of round or flattened cross section which helically wound or wrapped about the cable 30 . in one embodiment , the spool 22 may include a concave parabolic surface for operative gripping . in another embodiment , the cable assembly 10 is removably attached to the proximal handle section 8 for distal receipt by the endoscopic instrument 3 and reconnection to the proximal handle section 8 at an instrument port 56 associated with the endoscopic instrument 3 . referring to fig2 and 3 , the tip section 12 includes a pair of forceps jaws mounting yoke 36 which is secured to a distal end of the cable sheath 32 . the yoke 36 has the forceps jaw members 14 pivotally connected between legs thereof . each jaw member 14 is formed by a proximal jaw lever 38 and a distal jaw 40 . although not illustrated , the jaws 40 can be provided with serrated or toothed gripping surfaces . each jaw lever 38 is pivotally connected to a respective scissors link 42 , and ends of the links 42 are pivotally connected together and secured to a distal end of the operating cable 30 . retraction of the cable 30 into the sheath 32 pulls the scissors links 42 in a proximal direction and thereby pivots the jaws 40 toward closed positions . conversely , extension of the cable 30 in a direction out of the sheath 32 pushes the scissors links 42 in a distal direction and pivots the jaws 40 toward open positions . in operation of the forceps apparatus 1 , the surgeon holds the handle section 8 with a thumb extended through the thumb ring 20 and with the operating spool 22 held between the forefinger and middle finger or , alternatively , between the middle finger and ring finger . movement of the spool 22 toward the thumb ring 20 pulls the cable 30 in a retraction direction , thereby closing the forceps jaws 40 . conversely , movement of the spool 22 away from the thumb ring 20 extends the cable 30 , thereby opening the forceps jaws 40 . referring to fig4 , the illustrated flexible endoscope apparatus 3 includes a handle section 48 to which is attached an elongated composite scope assembly 50 which is inserted through an incision or through a patient &# 39 ; s body orifice by a surgeon . the scope assembly 50 typically includes ( not shown ) one or two fiberoptic bundles carrying light from a remote light source , a coherent fiberoptic bundle carrying an image viewed within the surgical site , one or more fluid carrying lumens , and an instrument lumen for the insertion of endoscopic surgical instruments , such as the forceps apparatus 1 . the image carried by the coherent fiberoptic bundle illuminates an image array within the handle section 48 , and a video signal is communicated to a remote video monitor by a video cable 52 for direct viewing by the surgeon and possible recording . the handle section 48 is provided with one or more fluid controls 54 , for controlling the injection of fluids into the surgical site or suction , and the instrument or forceps port 56 , through which a surgical instrument such as the forceps apparatus 1 can be inserted . the illustrated scope assembly 50 has a bendable or steerable tip 58 which is selectively controlled by the surgeon by rotation of a steering control 60 mounted on the handle section 48 . when use of the forceps apparatus 1 with the endoscope instrument 3 is needed , the surgeon grasps the handle section 8 and pulls the spool 22 toward the thumb ring 20 to close the jaws 40 and to increase the axial rigidity of the cable assembly 10 . the tip section 12 is inserted into the forceps port 56 of the instrument 3 , followed by the cable assembly 10 . insertion is continued until the tip section 12 reaches the surgical site . the tip section 12 and cable assembly 10 must pass through any curves in the composite scope 50 . once the tip section 12 is at the surgical site , the surgeon must carefully position and orient the jaws 40 for use in grasping whatever structure requires manipulation . correction of the axial position of the tip section 12 is a simple matter of extending or retracting the apparatus 1 with respect to the endoscope instrument 3 . however , angular correction of the orientation of the jaws 40 is sometimes resisted by frictional contact of the cable sheath 32 with inner walls of the lumen ( not shown ) through which the cable assembly 10 extends , particularly at locations of bends in the composite scope 50 . torsional resistance to rotation of the cable assembly 10 is resisted until overcome , at which point , the tip assembly 12 suddenly jumps . thus , angular correction of the jaws 40 sometimes overshoots the desired orientation . in order to overcome orientation problems with the forceps jaws 40 , improvements are made in the cable assembly 10 to increase its rotational rigidity without affecting the overall flexibility of the cable assembly 10 . the length of the cable assembly 10 from a distal end of the handle frame 18 to the tip assembly 12 is limited to control the torsional resilience of the cable assembly 10 . in the illustrated apparatus 1 , the length is limited to about 14 inches ( 35 . 5 cm ). the illustrated cable sheath 32 is formed by a stainless steel wire wrapped helically about the operating cable 30 . the desirable length of the cable assembly 10 may be different for other materials and types of construction of the cable sheath 32 . additionally , the outer diameter of the cable sheath 32 must have a desired clearance within the instrument / forceps lumen within the composite scope 50 . finally , the relative coefficient of friction between the material forming the cable sheath 32 and the forceps lumen must be low to further reduce frictional binding between the cable sheath 32 and the forceps lumen . to improve the torsional rigidity region 16 associated with the apparatus 1 , it is desirable to decrease the accumulation of stress leading to the torsional deformation of the cable assembly 10 and decrease the frictional resistance generated between the cable assembly 10 and the flexible endoscope 3 , improving the transmission of the flexible forceps 1 to the surgical site . stated differently , the torsional rigidity region 16 can be improved by increasing the torsional rigidity and decreasing the flexural rigidity . in one embodiment the improved torsional rigidity region 16 , defined by a junction between the cable assembly 10 including the sheath 32 and cable 30 and a lumen 50 a associated with the elongated composite scope assembly 50 , may be provided , the sheath 32 having an outer sidewall with a reduced frictional surface for being received by the lumen 50 a wherein the lumen 50 a and the sheath 32 have complementary properties for increasing the deflectional resistance of the distal tip section 12 while preventing the cable assembly 10 from binding within the composite scope assembly 50 . generally , the distal end of the composite scope assembly 50 is separated a distance from the distal tip section 12 , which itself is further separated from the surgical site . depending upon the characteristics and configuration of the received flexible forceps 1 , the separation distance is between x and y millimeters , where a distance less than x or greater than y would provide non - optimal insertional rigidity for the flexible forceps 1 . the change between x and y is represented by δx and the moment of inertia corresponding to the composite scope assembly outer surface 50 corresponds to mr 2 where m is the mass of the composite scope assembly 50 and r is the corresponding radius . the moment of inertia related to the flexible forceps 1 therefore corresponds to ( ml 2 )/ 3 where l is the length , δx , and m is the mass of the flexible forceps 1 . in this case , the flexible forceps 1 has an exponentially greater moment of inertia based upon δx , however , as δx increases the moment decreases resulting in a corresponding loss of rigidity of the flexible forceps 1 . stated another way , as the distal tip section 12 extends farther out of the distal end of the composite scope assembly 50 , the flexible forceps 1 become less torsionally rigid . in addition , by decreasing δx , cartilage or other tissue associated with the surgical site may be damaged by a corresponding increased rigidity associated with the flexible forceps 1 extending past the composite scope assembly distal end 50 . it is to be understood that while certain forms of the present invention have been illustrated and described herein , it is not to be limited to the specific forms or arrangement of parts described and shown .
an improved medical transmission apparatus for transmitting a flexible forceps through one of a plurality of lumens associated with an elongated composite scope assembly towards a surgical site presenting an increased torsional rigidity region for increased deflectional resistance of the forceps and being defined by a junction between a sheath associated with the forceps and a lumen extending cylindrically along the elongated composite scope assembly ; a portal entry associated with the elongated composite scope assembly having a diameter sized for receiving and transmitting a distal tip section associated with said forceps therethrough and a cylindrical clearance positioned between an outer sidewall associated with said sheath and an inner surface associated with said lumen , the cylindrical clearance directing said forceps towards the surgical site .