[TA] the mostly sharp edge of the orbital opening that is the peripheral border of the base of the pyramidal orbit. The superior half of the orbital rim is the supraorbital margin; the inferior half is the infraorbital margin. The frontal, maxillary, and zygomatic bones contribute to the orbital rim, which is generally strong so as to protect the orbital contents. Weak potential fracture sites of the rim coincide with the sutures between the participating bones. SYN: margo orbitalis [TA], margin of orbit, orbital rim.