Abstract: The invention relates to an intervertebral fusion implant for fusing two adjacent vertebrae (9, 9?), comprising a base piece (2) and a top piece (3) which in each case are designed to come to rest against a facing end plate (92) of one of the adjacent vertebrae (9, 9?), wherein the top piece (3) is vertically adjustable relative to the base piece (2), wherein a ratchet device (4), which effects a vertical adjustment in steps and secures a set height against reversion, is provided between the base piece (2) and the top piece (3). Thus a defined expansion can be achieved which is dependent upon the number of actuations. Precise control over the state of expansion is enabled in a purely haptic manner. Furthermore, implantation instruments are provided which are configured as parallel spreaders and have a stop as spreading path limiter or co-operating force and path measuring device.