Surgical instruments employing sensors

1. A method of performing a surgical procedure on tissue comprising the steps of:

providing a surgical instrument including an end effector including a first tissue engaging member and a second tissue engaging member in juxtaposed relation to the first tissue engaging member;

positioning the first and second tissue engaging members on opposite sides of the tissue;

approximating the first and second tissue engaging members until the tissue contact determining element is engaged;

recording an initial distance between the first and second tissue engaging members as an initial tissue thickness;

further approximating the first and second tissue engaging members to compress the tissue therebetween;

monitoring at least one of a compression force and a strain on the tissue; and

terminating the approximation of the first and second tissue engaging members when at least one of the compression force and the strain on the tissue reaches a predetermined level.

2. The method according to claim 1 , wherein the surgical instrument includes:

a gap determination element operatively associated with each of the first tissue engaging member and the second tissue engaging member for measuring a gap distance between the first tissue engaging member and the second tissue engaging member; and

a tissue contact determining element operatively associated with a respective tissue contacting surface of at least one of the first tissue engaging member and the second tissue engaging member.

3. The method according to claim 2 , wherein the surgical instrument further comprises a processor operatively connected to each of the gap determining elements and tissue contact determining elements.

4. The method according to claim 3 , wherein the tissue contact determining elements transmit a signal to the processor when the first and second tissue engaging members are in contact with the tissue.

5. The method according to claim 4 , wherein the gap determining elements transmit signals to the processor regarding a distance between the first and second tissue engaging members.

6. The method according to claim 5 , further comprising the step of determining at least one of the compression force and strain on the tissue as a result of the reduction in distance between the first and second tissue engaging members.

7. The method according to claim 6 , further comprising the step of activating an indicator when at least one of the compression force and strain on the tissue achieves the predetermined level of compression or strain.

8. The method according to claim 7 , further comprising the step of setting the predetermined level of compression or strain for the tissue prior to the compression of the tissue.

9. The method according to claim 8 , wherein the surgical instrument is a stapler.

10. The method according to claim 9 , further comprising the step of firing the surgical stapler when at least one of the compression force and the strain on the tissue is approximately equal to the predetermined level of compression or strain.

11. The method according to claim 10 , wherein the gap determination element is selected from the group consisting of a slide potentiometer, a rotational potentiometer, a linear variable differential transformer, a magneto-resistive element, capacitive elements, electromagnetic induction sensors, Hall effect sensors, and optical based sensors.

12. The method according to claim 11 , wherein the tissue contact determining element is selected from the group consisting of pressure sensors, electrical contacts and sensing circuits, force transducers, piezoelectric elements, piezoresistive elements, metal film strain gauges, semiconductor strain gauges, inductive pressure sensors, capacitive pressure sensors, and potentiometric pressure transducers.

13. The method according to claim 1 , further comprising the step of monitoring a tension force exerted on the tissue.