Patent ID: 8523865

Claim:
An instrument comprising: a shaft; an actuator connected to the shaft; a blade connected to the distal end of the actuator; wherein the actuator is configured to extend and retract the blade with respect to the shaft; and wherein the shaft is configured to be insertable into a cannula having a longitudinal axis and connectable to the cannula such that the blade is capable of longitudinal movement with respect to the cannula; a locking collar connected to the shaft such that the shaft is capable of longitudinal movement with respect to the locking collar; the locking collar being configured to connect to the cannula such that the instrument is inhibited from removal from the cannula; an adjustment collar connected to the shaft; the adjustment collar being longitudinally movable with respect to the shaft, wherein the longitudinal movement of the blade with respect to the cannula is limited by a plurality of predetermined stops defined by the adjustment collar.