The present invention relates to an implantable device (40), in particular to correct at least one vertebral level, comprising a rod having an outer radius (Rt) and a circumference determined at an area on a length (Lt); an elongate flat ligament; and a securing devices (50) of said elongate element in a partial encasing position of said area comprising first (51) and second (52) forks first general partly annular shape of inner radius, respectively, and comprising partly annular lower bearing surfaces respectively delimiting first (51b) and second (52b) circumference portions greater than half the circumference. Said securing devices (50) further comprises a shoulder part arranged relative to said lower bearing surfaces (51a, 52a) of the first and second forks (51, 52) so as to form a passage for said elongate element in said encasing position between said forks (51, 52) and said shoulder part (60).