Embodiments of the invention relate to an intervertebral cage for enclosing a bone graft for the fusion of two adjacent vertebrae, comprising a base element (1) made up of a posterior wall (2) and two lateral walls (3, 4) connected to it, and a closure element initially separated from the base element (1). Some embodiments include several intervertebral cages of the preceding type that all incorporate a single closure element made up of a plate extending over all vertebrae to be fused.