Intervertebral fusion implant for fusing two adjacent vertebrae, comprising a base piece (2) and a top piece (3), both of which are designed to come to rest against a facing end plate of one of the adjacent vertebrae. The top piece is vertically adjustable relative to the base piece, a ratchet device (4) being provided between the base piece (2) and the top piece (3), said ratchet device causing a step-by-step vertical adjustment and preventing a set height from being reduced due to restoring forces. Said implant allows for a defined expansion according to the number of actuations. The state of expansion can be controlled with precision in a purely haptic manner. Furthermore, the ratchet device allows the implant to remain in the set expanded state.