The invention concerns an implant system for being fastened to the posterior side of the spinal column. The implant system comprises an implant body, for example a plate, and a plurality of fasteners. The implant body comprises a fastening structure for each fastener. Each fastener extends between a proximal end and a distal end and comprises a thermoplastic material in a solid state, the thermoplastic material being liquefiable by energy impinging on the fastener, in an anchoring process, in which the fastener is pressed against bone tissue by a pressing force acting from a proximal side, and in which energy is coupled into the fastener to at least partially liquefy the thermoplastic material, wherein a flow portion of the thermoplastic material is pressed into bone tissue and, after re-solidification, anchors the fastener in the bone tissue.
