a sternal retractor for use in internal mammary artery dissection comprises a rack bar having fixed and movable spreader arms , the blade - carrying parts of which are rotatable to , and lockable in , several discrete positions . the blades are carried by slides on the spreader arms , and are pivotable about two mutually perpendicular axes which are also perpendicular to the arms , but restrained against rotation about axes extending lengthwise of the arms . one of the slides disclosed is provided with an undercut slot to receive a post for mounting auxiliary retractors . this makes the retractor especially useful for various operation in addition to internal mammary artery dissection .