a sternum retractor device is disclosed suitable for temporarily maintaining a selected gap between two sternal stumps during cardiac surgical procedures . the device comprises a pair of jaws configured so as to be inserted between the stumps and shaped for firmly engaging the stumps , an actuator connected to the jaws for controlling their mutual closing and opening movements , and a member for controlled feed or withdrawal of a selected biocompatible actuator fluid in / from the actuator , thereby enabling the achievement and maintenance of the gap required between the stumps as well as the progressive reduction of the gap as a function of a patient &# 39 ; s condition .