The invention relates to an implant device comprising: a sensor module (10) having one or a plurality of first fastening devices; an implant module (20) having one or a plurality of second fastening devices (21, 22, 23); a connecting module by means of which the sensor module is connected to the implant module via the one or the first fastening devices and via the one or the second fastening devices; and a folding axis, along which the implant device can be folded up.