instrument handles isolate the functions of supporting the instrument and actuating controls on the instrument . an instrument handle may be grasped and supported by the less dexterous digits and palm of a human hand , and controls mounted on the instrument handle may be actuated by the more dexterous digits . the instrument handle may couple to an end effector so that the hand , wrist , elbow , and shoulder remain in a comfortable position when the end effector is positioned to act effectively on a selected portion of a workpiece , such as a surgical site .