This is a system and an assembly for tensioning a flexible strip (3) to hold a bony element on an implant, comprising a shank (15) and means (42) for adjustably immobilizing a component (29) that is capable of translational movement with respect in a portion (25) of the devise. The shank (15) comprises a handle (23) for gripping at its second end (24), the portion (25) of the device (14) making an angle with the shank (15), the flexible strip (3) having two free ends. The component (29) capable of movement comprises a wheel (31) free to rotate with respect to a pivot pin (32) perpendicular to the portion (25), for guiding the strip (3) around its rounded periphery (33) comprising two distinct elements (34, 35) for anchoring the flexible strip (3).
