Ultrasonic surgical instrument blades

1. A method of balancing an ultrasonic instrument having an ultrasonically actuated blade, wherein the blade comprises a body portion and a step portion extending from the body portion, wherein the body portion comprises a first side, a second side, a width defined between the first and second sides, a center of gravity, and a centerline extending through said center of gravity, wherein the step portion includes a first surface, a second surface, and a cutting edge situated intermediate the first and second surfaces, wherein said first surface faces away from said centerline, wherein the second surface extends at an angle through said centerline between a first plane including the cutting edge and a second plane which is parallel to the first plane, wherein the first and second surfaces are not parallel and are oriented such that there is an angle defined therebetween, the method comprising the steps of:

configuring at least a portion of the blade such that the relationship of:

x

2

2

*

(

tan

⁢

α

)

-

1

+

(

w

-

x

)

2

⁢

(

x

*

(

tan

⁢

⁢

α

)

-

1

-

s

)

-

(

w

2

)

2

⁢

(

tan

⁢

α

)

-

1

is substantially equal to zero;

wherein w is said width of the body portion;

wherein s is the distance between the first plane and the second plane;

wherein α is said angle defined between the first and second surfaces of the step portion; and

wherein x is the distance between the second side of the body portion and the cutting edge.

2. The method of claim 1 , wherein said configuring step comprises the steps of:

selecting values for w, s, and α such that the blade is configured to transect tissue; and

solving said relationship for x.

3. The method of claim 1 , wherein said configuring step comprises the steps of:

selecting values for w, x, and a such that the blade is configured to transect tissue; and

solving said relationship for s.

4. The method of claim 1 , wherein said relationship is equal to zero.

5. A method of balancing an ultrasonic instrument comprising a surgical blade, wherein the surgical blade comprises a first portion and a second portion extending from the first portion, wherein the first portion comprises a first surface, a second surface, a width defined by the first surface and the second surface, a center of gravity, and a centerline extending through the center of gravity, wherein the second portion includes a third surface, a fourth surface, and a cutting edge defined by an intersection of the third surface and the fourth surface, wherein the third surface faces away from the centerline, wherein the fourth surface extends through the centerline between a first plane including the cutting edge and a second plane which is parallel to the first plane, wherein the third surface and the fourth surface are not parallel and are oriented such that an angle is defined therebetween, the method comprising:

configuring at least a portion of the surgical blade such that the relationship of:

x

2

2

*

(

tan

⁢

α

)

-

1

+

(

w

-

x

)

2

⁢

(

x

*

(

tan

⁢

⁢

α

)

-

1

-

s

)

-

(

w

2

)

2

⁢

(

tan

⁢

α

)

-

1

is substantially equal to zero;

wherein w is the width of the first portion;

wherein s is the distance between the first plane and the second plane;

wherein α is the angle defined between the third surface and the fourth surface; and

wherein x is the distance between the second surface and the cutting edge.

6. The method of claim 5 , wherein configuring at least the portion of the surgical blade comprises:

selecting values for w, s, and α such that the surgical blade is configured to transect tissue; and

solving the relationship for x.

7. The method of claim 5 , wherein configuring at least the portion of the surgical blade comprises:

selecting values for w, x, and α such that the surgical blade is configured to transect tissue; and

solving the relationship for s.

8. The method of claim 5 , wherein the relationship is equal to zero.

9. A method of balancing an ultrasonic instrument comprising a surgical blade, wherein the surgical blade comprises a first portion and a second portion extending from the first portion, wherein the first portion comprises a first surface, a second surface, a width defined by the first surface and the second surface, a center of gravity, and a centerline extending through the center of gravity, wherein the second portion includes a third surface, a fourth surface, and a cutting edge defined by an intersection of the third surface and the fourth surface, wherein the third surface does not transect the centerline, wherein the fourth surface transects the centerline and extends between a first plane including the cutting edge and a second plane which is parallel to the first plane, wherein the third surface and the fourth surface are not parallel and are oriented such that an angle is defined therebetween, the method comprising:

configuring at least a portion of the surgical blade such that the relationship of:

x

2

2

*

(

tan

⁢

α

)

-

1

+

(

w

-

x

)

2

⁢

(

x

*

(

tan

⁢

⁢

α

)

-

1

-

s

)

-

(

w

2

)

2

⁢

(

tan

⁢

α

)

-

1

is substantially equal to zero;

wherein w is the width of the first portion;

wherein s is the distance between the first plane and the second plane;

wherein α is the angle defined between the third surface and the fourth surface; and

wherein x is the distance between the second surface and the cutting edge.

10. The method of claim 9 , wherein configuring at least the portion of the surgical blade comprises:

selecting values for w, s, and α such that the surgical blade is configured to transect tissue; and

solving the relationship for x.

11. The method of claim 9 , wherein configuring at least the portion of the surgical blade comprises:

selecting values for w, x, and α such that the surgical blade is configured to transect tissue; and

solving the relationship for s.

12. The method of claim 9 , wherein the relationship is equal to zero.