The invention provides an intervertebral implant for the lumbo-sacral joint, the implant comprising a spacer suitable for being disposed between the fifth lumbar vertebra L5 and the vertebra S1 of the sacrum that is articulated to the vertebra L5. The implant comprises a flexible tie having end portions suitable for being fastened to the sacrum with the help of fasteners such as pedicular screws. The flexible tie has an intermediate portion suitable for co-operating with a connection system such as a hook provided on the spacer so that the flexible tie connects the spacer to the sacrum. The flexible tie is put under tension in such a manner as to exert a return force on the spacer towards the vertebra S1.