The present invention broadly relates to laparoscopic surgical instruments. More particularly, the invention relates to surgical instruments having end effectors in the form of scissors useful in a laparoscopy procedure which involves the lifting of a structure away from surrounding tissue prior to severing the structure by scissoring action.
The laparoscopy procedure has recently become a widely practiced surgical procedure. A laparoscopy procedure typically involves incising through the naval and through the abdominal wall for viewing and/or operating on the ovaries, uterus, gall bladder, bowels, appendix, although more recently, incisions and insertion of trocar tubes have been made in different areas of the abdomen and even in the chest cavity. Typically, trocars are utilized for creating the incisions. Trocar tubes are left in plane in the abdominal wall so that laparoscopic surgical tools may be inserted through the tube. A camera or magnifying lens is often inserted through the largest diameter trocar tube (e.g. 10 mm diameter) which is generally located at the navel incision, while a cutter, dissector, or other surgical instrument is inserted through a similarly sized or smaller diameter trocar tube (e.g. 5 mm diameter) for purposes of manipulating and/or cutting the internal organ. Sometimes it is desirable to have several trocar tubes in place at once in order to receive several surgical instruments. In this manner, organ or tissue may be grasped with one surgical instrument, and simultaneously may be cut or stitched with another surgical instrument; all under view of the surgeon via the camera in place in the navel trocar tube.
Previous to the present invention, laparoscopic tools have utilized scissor end effectors of the hook type which have hooked (scooped) blades for ensuring that the tips of the cutting blades come together before cutting action starts. The problem with the laparoscopic hooked scissors of the art is that the structure to be cut (e.g., a duct, vein, tendon, etc.) often gets trapped between the blades in such a manner that cutting is difficult and/or that the cut made is jagged (i.e., not clean). The applicants have determined that a primary reason for the difficulty in cutting with the hooked scissors of the art is that clean cutting requires that the cutting blades be forced into contact at preferably a single moving cutting point. Simple scissors are built in such a fashion that the blades are forced into contact at a single point by a torque acting from their pivoting point and arising from elastic deformation of the blades or some other resilient means at or near the pivoting point. The hook scissors of the art have been designed to have two cutting points where the edges of the scooped blades touch. The difficulty with this design is that it is difficult, if not impossible, to fabricate such scissors so that the torque acting from their pivot point causes both desired cutting points to be forced together. Indeed, such scissors are usually hand built with a minimum of resilience in their construction and fitted together with minimum operating clearance at the pivot point so that the two blades, while not being actually forced into contact at either of the intended cutting points, close with very little clearance. Such an arrangement, even when executed with skill, will often fail to cut materials with a fibrous or elastic nature, thereby causing the blades to separate (i.e., a lateral gap will form). Also, the action of the hook scissors of the art is such that the two cutting points start at the inner and outer ends of the blades and move to meet at the middle of the cutting area. This closing action causes fibrous and elastic material to bunch in the scissors, resulting in further force pushing the blades apart and inhibiting their cutting actions.