The invention relates to a connecting member for maintaining the spacing between at least two anchor members screwed into vertebrae. It comprises two rigid rod-forming parts (12, 14) made of a first material and each having a fixing, first portion (16, 18) adapted to be fixed into an anchor member and a fastening, second portion (20, 22), said rods (12, 14) being aligned with each other and said fastening portions (20, 22) facing each other, and a connecting body (24) made of a second material which is more elastically deformable than said first material and which interconnects said rigid parts (12, 14) by means of the facing fastening portions (20, 22) so that said connecting body (24) is able to deform elastically, whereby the vertebrae, which are held spaced from each other, are movable relative to each other.