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. Thus it can be implanted more reliably, wherein the risk of overloading or injury to the vertebrae and the nerves and ligaments of the vertebrae is decreased.
