Assembly for sequentially percutaneously applying an electrode and an anesthetic to tissue

Abstract

An assembly that consist of a cannula; an electrode and a syringe. The cannula has a hub that defines a set of adjacent bores. A first proximal bore receives the head of the electrode. A second bore receives the head of the syringe. The cannula has a stop that limits the extent to which the electrode can be inserted in the proximal bore. When the syringe is inserted in the cannula hub, the syringe is inserted beyond the stop. The syringe presses against an adjacent surface that defines the second bore to form a seal between the cannula and the syringe.

What is claimed is: 
     
         1 . A cannula for performing an electrosurgical procedure with an electrode and a syringe, said cannula comprising:
 a hub, said hub being formed with
 a through path that extends between opposed proximal and distal ends of the hub, the through path being defined by: a first inner surface of said hub that defines a proximal bore that has a constant diameter and that is dimensioned to receive an electrode head; and a second inner surface of said hub that defines a middle bore adjacent the proximal bore, the middle bore having a diameter, that is dimensioned to receive a syringe head and that, extending distally from the proximal bore decreases in diameter so that the middle bore has a taper so that the syringe head will abut the second inner surface of said hub; and 
 a locking feature that extends outwardly from or protrudes into the proximal bore, said locking feature configured to cooperate with a complementary locking feature of the electrode head, so that when the locking features engage, the electrode head is releasably held in the proximal bore of said hub; and 
   a tube that extends forward of the distal end of the hub, said tube having a lumen through which, when the electrode head is seated in the proximal bore of said hub, a shaft of the electrode extends into the lumen of said tube.   
     
     
         2 . The cannula of  claim 1 , wherein the cannula hub locking feature is a rib that extends inwardly from the proximal bore-defining first inner surface of said hub into the proximal bore. 
     
     
         3 . The cannula of  claim 1 , wherein said hub is formed to define a step that extends inwardly from a distal end of the proximal bore so as to function as a transition surface between the proximal bore and the middle bore. 
     
     
         4 . The cannula of  claim 3 , wherein said hub is further formed so that step is: angularly offset from the adjacent first inner surface of said hub and extends radially inwardly from the first inner surface is adjacent proximal surface; and angularly offset from second inner surface of said hub and is located radially outwardly from the second inner surface. 
     
     
         5 . The cannula of  claim 4 , wherein said hub is further formed so that said step is a surface that, relative to a line that is parallel to a longitudinal axis of the cannula and that extends proximally from an outer edge of said step, is at an angle that is a maximum of 90° from the line. 
     
     
         6 . The cannula of  claim 3 , wherein the cannula hub is further formed so that said step is disposed in a plane that is perpendicular to a longitudinal axis of the through path through said hub. 
     
     
         7 . The cannula of  claim 3 , wherein said hub is further shaped so that: the middle bore is defined by a circumferential wall internal to the hub; and at least one notch extends inwardly from bore defining inner wall, the at least one notch intersecting and interrupting said step between the proximal bore and the middle bore. 
     
     
         8 . The cannula of  claim 3 , wherein said hub ( 34 ) is shaped so that difference in diameters between the adjacent portions of the proximal bore and the middle bore that define, respectively, outer and inner perimeters of said step is at least 0.2 mm. 
     
     
         9 . The cannula of  claim 1 , wherein said tube has a maximum outer diameter of 2.0 mm. 
     
     
         10 . The cannula of  claim 1 , wherein said hub is shaped so that the middle bore adjacent the proximal bore and dimensioned to receive the syringe head ( 96 ) is a first middle bore ( 50 ) and distal to and contiguous to the first middle bore said hub is formed to have a second middle bore that is part of the through path through said hub and said hub is shaped so the second middle bore have a taper that, extending distally from the first middle bore ( 50 ), is more pronounced than the taper of the first middle bore ( 50 ). 
     
     
         11 . A cannula for performing an electrosurgical procedure with an electrode and a syringe, said cannula comprising:
 a hub, said hub being formed with a through path that extends between opposed proximal and distal ends of the hub, the through path including a proximal bore that is formed in said hub and that is dimensioned to receive a head of the electrode head), and a middle bore formed in said hub adjacent the proximal bore, the middle bore having a diameter less than the diameter of an adjacent section of the proximal bore so that, internal to the hub, a step ( 46 ) extends inwardly from the inner surface of the hub that defines a distal end of the proximal bore, said step dimensioned to function as a stop that prevents advancement of the electrode head beyond the step; and, distal to the step, the through path through the hub is formed to have a section shaped to receive the syringe head and, said hub is further formed to have a locking feature that is associated with an inner surface of the hub that defines the proximal bore, said locking feature configured to cooperate with a complementary locking feature of the electrode head, so that when the locking features engage, the electrode head is releasably held in the cannula hub; and   a tube that extends forward of the distal end of the hub, said tube having a lumen in which, when the electrode head is seated in said hub, a shaft of the electrode ( 70 ) extends;   
     
     
         12 . The cannula of  claim 11 , wherein said hub is further formed so that said step is: angularly offset from the adjacent proximal surface internal to the hub that defines the adjacent distal end of proximal bore and is located radially inwardly from this adjacent proximal surface; and angularly offset from the adjacent distal surface that defines the adjacent proximal end of middle bore and is located radially outwardly from this surface. 
     
     
         13 . The cannula of  claim 11 , wherein said hub is further formed so that said step is a surface that, relative to a line that is parallel to the longitudinal axis of the cannula and that extends proximally from an outer edge of said step, is at an angle that is a maximum of 90° from this line. 
     
     
         14 . The cannula of  claim 11 , wherein said hub is further formed so that said step ( 46 ) is disposed in a plane that is perpendicular to a longitudinal axis of the through path through said hub. 
     
     
         15 . The cannula of  claim 11 , wherein said hub is further formed so that the middle bore is the portion of the of the though path through the hub that is dimensioned to receive the syringe head. 
     
     
         16 . The cannula of  claim 11 , wherein the cannula hub locking feature is a rib that extends inwardly from the bore-defining inner surface of said hub. 
     
     
         17 . The cannula of  claim 11 , wherein said hub is formed so that the proximal bore has a diameter that is constant along the length of the bore. 
     
     
         18 . The cannula of  claim 11 , wherein said hub is further shaped so that: the middle bore is defined by a circumferential wall internal to the hub; and at least one notch extends inwardly from bore defining inner wall, the at least one notch intersecting and interrupting said step between the bores. 
     
     
         19 . The cannula of  claim 11 , wherein said tube has a maximum outer diameter of 2.0 mm. 
     
     
         20 . The cannula of  claim 11 , wherein said hub is shaped so that difference in diameters between the adjacent portions of the proximal bore and the middle bore that define said step is at least 0.2 mm. 
     
     
         21 . The cannula of  claim 11 , wherein said hub is shaped so that, distal to said step, the middle bore has a diameter that is constant along the bore. 
     
     
         22 . The cannula of  claim 11 , wherein said hub is shaped so that middle bore that defines said step is a first middle bore and distal to and contiguous to the first middle bore, there is a second middle bore, the second middle bore shaped so as to have a taper that extends inwardly and that, extending distally from the first middle bore, is more pronounced than the taper of the first middle bore.