The invention concerns an intervertebral implant that includes a spacer designed firstly to assume an implantation shape in which the spacer has two opposed channels (3, 4) bordered by retaining wings (3a, 3b, 4a, 4b), intended to receive the two spinous processes of two vertebrae, and secondly an insertion shape in which the parts of the implant forming the channels (3, 4) are separated by a value (d), and on at least one of their sides are lacking the retaining wings (3a, 3b, 4a, 4b), characterized in that the implant (1) is made from a shape-memory material, so that the implant changes to its implantation shape when it is subjected to heat, and so that, in this implantation shape, the parts of the implant forming the channels (3, 4) are separated by a value (D) that is greater than the value(d) of the insertion shape, in order to ensure the separation of the spinous processes.