The invention relates to an implantable surgical ring (1) designed to be closed on itself to form a closed loop (2) having an extension medium axis (XX) for tightening a biological organ (3), wherein said ring (1) includes at least a first and a second ring tightening chamber (12, 13) attached to each other designed to contain a filling fluid for tightening said biological organ (3), said first and second tightening chambers being stepped along the extension medium axis (XX), said ring being characterised in that the first and second tightening chambers (12, 13) include between them a material-free clearance area (20), in which the wall of the biological organ (3) may move without contacting the ring (1), in order to tighten said biological organ (3) at the level of at least two axially-separated contact areas (14A, 14B).
