Flexible instrument with nested conduits

Abstract

A medical instrument comprises an elongate flexible body including a proximal section and a steerable distal section. The instrument also comprises a control tendon extending within the elongate flexible body. The instrument also comprises an axially variable stiffening mechanism including a first conduit extending through a second conduit. The axially variable stiffening mechanism is adjustable between a first state in which an actuation of the control tendon produces a first bend radius in the steerable distal section and a second state in which the actuation of the control tendon produces a second bend radius in the steerable distal section. The second bend radius is different than the first bend radius.

1 . A medical instrument comprising:
 an elongate flexible body including a proximal section and a steerable distal section;   a control tendon extending within the elongate flexible body; and   an axially variable stiffening mechanism adjustable between a first state in which applying an actuation force to the control tendon produces a first bend radius in the steerable distal section and a second state in which applying the actuation force to the control tendon produces a second bend radius in the steerable distal section, the second bend radius being different than the first bend radius.   
     
     
         2 . The instrument of  claim 1 , wherein the control tendon extends within the axially variable stiffening mechanism. 
     
     
         3 - 8 . (canceled) 
     
     
         9 . The instrument of  claim 1 , further comprising a control element configured to engage the axially variable stiffening mechanism to selectively adjust the axially variable stiffening mechanism between the first state and the second state. 
     
     
         10 - 21 . (canceled) 
     
     
         22 . The instrument of  claim 1 , wherein the axially variable stiffening mechanism comprises a first conduit extending through a second conduit. 
     
     
         23 . The instrument of  claim 22 , further comprising a first grip element secured to a proximal portion of the first conduit and a second grip element secured to a proximal portion of the second conduit. 
     
     
         24 . The instrument of  claim 22 , wherein the control tendon extends through the first conduit and terminates within the steerable distal section. 
     
     
         25 . The instrument of  claim 24 , further comprising a proximal transition section between the proximal section and the steerable distal section. 
     
     
         26 . The instrument of  claim 25 , wherein the second conduit terminates at the proximal transition section. 
     
     
         27 . The instrument of  claim 25 , further comprising a distal transition section between a proximal steerable portion and a distal steerable portion of the distal steerable section. 
     
     
         28 . The instrument of  claim 27 , wherein the first conduit terminates at the distal transition section. 
     
     
         29 . The instrument of  claim 27 , wherein the second conduit terminates at the distal transition section, and the first conduit terminates distal to the distal transition section within the steerable distal section. 
     
     
         30 . The instrument of  claim 22 , wherein the first conduit and the second conduit comprise coil pipes. 
     
     
         31 . The instrument of  claim 22 , further comprising a first control element configured to selectively adjust the axial stiffness of the first conduit, and a second control element configured to selectively adjust the axial stiffness of the second conduit. 
     
     
         32 . The instrument of  claim 31 , further comprising a controller, wherein each of the first control element and the second control element comprises at least one screw that is selectively adjustable by the controller. 
     
     
         33 . A medical instrument comprising:
 an elongate flexible body including a proximal section, a steerable distal section, and a steerable proximal section disposed between the proximal section and the steerable distal section;   a control tendon extending within the elongate flexible body; and   an axially variable stiffening mechanism being adjustable between a first state in which applying an actuation force to the control tendon produces a first bend radius in the steerable proximal section and a second state in which applying the actuation force to the control tendon produces a second bend radius in the steerable proximal section, the second bend radius being different than the first bend radius.   
     
     
         34 . The instrument of  claim 33 , wherein the control tendon extends within the axially variable stiffening mechanism. 
     
     
         35 . The instrument of  claim 34 , wherein the axially variable stiffening mechanism comprises a first conduit extending through a second conduit. 
     
     
         36 . The instrument of  claim 35 , wherein the control tendon extends through the first conduit and terminates within the steerable distal section. 
     
     
         37 . The instrument of  claim 36 , wherein the second conduit terminates at a proximal end of the steerable proximal section. 
     
     
         38 . The instrument of  claim 37 , wherein the first conduit terminates at a proximal end of the steerable distal section.