Blades with functional balance asymmetries for use with ultrasonic surgical instruments

Abstract

Disclosed is an ultrasonic surgical instrument that combines end-effector geometry to best affect the multiple functions of a shears-type configuration. The shape of the blade is characterized by a radiused cut offset by some distance to form a curved geometry. The cut creates a curved surface with multiple asymmetries causing multiple imbalances within the blade. Inbalance due to the curve of the instrument is corrected by a non-functional asymmetry proximal to the functional asymmetry. Imbalance due to the asymmetric cross-section of the blade is corrected by the appropriate selection of the volume and location of material removed from a functional asymmetry. The shape of the blade in one embodiment of the present invention is characterized by two radiused cuts offset by some distance to form a curved and potentially tapered geometry. These two cuts create curved surfaces including a concave surface and a convex surface. The length of the radiused cuts affects, in part, the acoustic balancing of the transverse motion induced by the curved shape.

What is claimed is:  
     
         1 . An ultrasonic clamp coagulator apparatus comprising: 
 a housing, said housing comprising an actuator;    an outer tube having a proximal end joined to said housing, and a distal end, said outer tube defining a longitudinal axis;    an actuating element reciprocably positioned within said outer tube, said actuating element operatively connected to said actuator;    an ultrasonic waveguide positioned within said outer tube, said ultrasonic waveguide having an end-effector extending distally from said distal end of said outer tube, 
 wherein said end-effector comprises a broad edge and a narrow edge, wherein said narrow edge is defined by the intersection of a first surface and a second surface, wherein said first surface extends proximally into said end-effector defining a length of said first surface; and  
   a clamp arm pivotally mounted on said distal end of said outer tube for pivotal movement with respect to said end-effector for clamping tissue between said clamp arm and said end-effector, said pivotal movement occurring about a horizontal axis, the arc of said pivotal movement of said clamp arm defining a vertical plane, said vertical plane having a vertical axis orthogonal to both said longitudinal axis and said horizontal axis, said clamp arm operatively connected to said actuating element so that reciprocal movement of said actuating element pivots said clamp arm along said vertical plane;    wherein said length of said first surface balances said waveguide such that excursion of said waveguide is minimized in said vertical plane.    
     
     
         2 . An ultrasonic clamp coagulator apparatus according to  claim 1 , wherein excursion of said end-effector along said vertical axis is limited to less than 15%.  
     
     
         3 . An ultrasonic clamp coagulator apparatus according to  claim 1 , wherein excursion of said end-effector along said vertical axis is limited to less than 10%.  
     
     
         4 . An ultrasonic clamp coagulator apparatus according to  claim 1 , wherein excursion of said end-effector along said vertical axis is limited to less than 5%.  
     
     
         5 . A blade for an ultrasonic surgical instrument comprising: 
 a proximal end;    a distal end;    a broad edge; and    a narrow edge, wherein said narrow edge is defined by the intersection of a first surface and a second surface, wherein said first surface extends proximally into said blade from said distal end toward said proximal end, defining a length of said first surface; 
 wherein said length of said first surface balances said blade such that a secondary tip excursion of said blade is less than 15% of the primary tip excursion of said blade.  
   
     
     
         6 . An ultrasonic surgical instrument according to  claim 5 , wherein a secondary tip excursion of said blade is less than 10% of the primary tip excursion of said blade.  
     
     
         7 . An ultrasonic surgical instrument according to  claim 5 , wherein a secondary tip excursion of said blade is less than 5% of the primary tip excursion of said blade.  
     
     
         8 . An ultrasonic surgical instrument according to  claim 5 , wherein said first surface is concave.  
     
     
         9 . An ultrasonic surgical instrument according to  claim 6 , wherein said first surface is concave.  
     
     
         10 . An ultrasonic surgical instrument according to  claim 7 , wherein said first surface is concave.  
     
     
         11 . An ultrasonic surgical instrument according to  claim 8 , wherein said second surface is convex.  
     
     
         12 . An ultrasonic surgical instrument according to  claim 9 , wherein said second surface is convex.  
     
     
         13 . An ultrasonic surgical instrument according to  claim 10 , wherein said second surface is convex.  
     
     
         14 . A method of balancing an ultrasonic blade comprising the steps of: 
 A) selecting a maximum acceptable level of undesirable blade excursion;    B) adding a functional asymmetry to said blade by removing an amount of material from a portion of said blade along a length of said blade, wherein said length of said functional asymmetry satisfies said acceptable level of undesirable excursion identified in step A.    
     
     
         15 . A method of balancing an ultrasonic blade according to  claim 14 , wherein said maximum acceptable level of undesirable blade excursion in step A is 15% normalized excursion.  
     
     
         16 . A method of balancing an ultrasonic blade according to  claim 14 , wherein said maximum acceptable level of undesirable blade excursion in step A is 10% normalized excursion.  
     
     
         17 . A method of balancing an ultrasonic blade according to  claim 14 , wherein said maximum acceptable level of undesirable blade excursion in step A is 5% normalized excursion.  
     
     
         18 . A method of balancing an ultrasonic blade according to  claim 14 , wherein in step B, said functional asymmetry is a narrow edge, wherein said narrow edge is defined by the intersection of a first surface and a second surface, wherein said first surface extends proximally into said blade from a distal end of said blade toward a proximal end of said blade, defining said length of said functional asymmetry; 
 wherein said length of said functional asymmetry balances said blade such that a secondary tip excursion of said blade is less than 15% of the primary tip excursion of said blade.