Ultrasonic energy device which varies pressure applied by clamp arm to provide threshold control pressure at a cut progression location
Surgical instruments and system and methods for using surgical instruments are disclosed. A surgical instrument comprises an end effector comprising an ultrasonic blade and clamp arm, an ultrasonic transducer, and a control circuit. The ultrasonic transducer ultrasonically oscillates the ultrasonic blade in response to a drive signal from a generator. The end effector receives electrosurgical energy to weld tissue. The control circuit determines a resonant frequency measure indicative of a thermally induced change in resonant frequency and a electrical continuity measure; calculates a weld focal point based on the determined measures, controls closure of the clamp arm to vary a pressure applied by the clamp arm to provide a threshold control pressure to the tissue loaded into the end effector, and maintains a gap between the ultrasonic blade and clamp arm at a point proximal to the proximal end of the tissue. Pressure is varied based on corresponding weld focal point.
1 . A surgical hub, comprising:
a control circuit, configured to:
transmit a first control signal to a surgical instrument to cause a force to be applied to a tissue by a clamp arm of the surgical instrument;
determine a focal point between the clamp arm and the tissue based on an electrical continuity feedback measurement obtained from the surgical instrument, wherein the focal point is defined as a point of contact between the clamp arm and the tissue;
detect a shift in the focal point; and
transmit a second control signal to the surgical instrument to vary the force applied by the clamp arm according to the detected shift in the focal point.
2 . The surgical hub of claim 1 , wherein the control circuit is configured to determine the focal point based on a resonant frequency of an ultrasonic blade of the surgical instrument.
3 . The surgical hub of claim 1 , wherein the control circuit is further configured to detect a proximal to distal shift in the focal point relative to the clamp arm.
4 . The surgical hub of claim 1 , wherein the control circuit is further configured to detect a distal to proximal shift in the focal point relative to the clamp arm.
5 . A surgical system, comprising:
a surgical instrument comprising a clamp arm and an electrode, the electrode configured to apply energy to a tissue; and
a control circuit, configured to:
transmit a first control signal to the surgical instrument to cause the clamp arm to apply a force to the tissue;
determine a focal point between the clamp arm and the tissue based on an electrical continuity feedback measurement obtained from the electrode, wherein the focal point is defined as a point of contact between the clamp arm and the tissue;
monitor movement of the focal point; and
transmit a second control signal to the surgical instrument to vary the force applied by the clamp arm according to the monitored movement of the focal point.
6 . The surgical system of claim 5 , wherein the clamp arm comprises a tissue pad, and wherein the focal point is defined as a point of contact between the tissue pad and the tissue.
7 . The surgical system of claim 6 , wherein the tissue pad comprises axially spaced, proximally extending gripping teeth.
8 . The surgical system of claim 5 , wherein the surgical instrument comprises an ultrasonic blade, and wherein the focal point is determined based on a resonant frequency of the ultrasonic blade.
9 . The surgical system of claim 5 , wherein the control circuit is further configured to detect a proximal to distal shift in the focal point relative to the clamp arm.
10 . The surgical system of claim 5 , wherein the control circuit is further configured to detect a distal to proximal shift in the focal point relative to the clamp arm.