Kidney stone instrument

Claim 1

An instrument for the removal of kidney stones that includes the combination of (a) a kidney stone grasping means comprising at least one pair of opposed jaw members that are mounted in a support which is mounted for axial movement in a tube, (b) means for alternately moving said jaw members toward each other and away from each other, said means including (1) a first resilient means for urging the toothed sections of said jaw members apart in an "open" position, (2) at least one length of Nitinol having one end attached to said axially movable jaw member support and the other end attached to a spaced apart fixed point on the tube in which said jaw members are mounted, (3) mechanical pressure means for maintaining sufficient pressure on said length of Nitinol when said length is below its critical temperature condition so that said length of Nitinol will be stretched in a lengthwise direction, but said sufficient pressure being inadequate to maintain said length of Nitinol in a stretched position when the Nitinol is heated above its critical temperature, and (4) means to control the temperature of said Nitinol, whereby said jaws will be maintained in an open position to receive kidney stones when said length of Nitinol is below said critical temperature and said jaws will move from an open to a closed position to grasp and/or crush kidney stones when said length of Nitinol is above said critical temperature.