The present invention relates to a system comprising a milling cutter and a guide piece. The milling cutter comprises an elongated shaft extending along a longitudinal axis and a distal end having a milling portion with at least one circumferentially arranged cutting edge for removing bone tissue. The guide piece has a fixing element for releasably fixing the guide piece to the support structure and a longitudinal axis. Here, one of the guide piece and the distal end of the milling cutter comprises a head having a central axis coaxial with the longitudinal axis of one of the guide piece and the distal end of the milling cutter, and the other of the distal end of the guide piece and the milling cutter. Comprises an internal cavity extending along a central axis coaxial with the other of the guide piece and the distal end of the milling cutter. The head comprises a guide part having a bearing surface which is convexly rounded in the axial plane of the head, and the cavity comprises a guide part having an abutment surface which is concave in the axial plane of the cavity. The bearing surface and the abutment surface are circularly symmetric about their central axis, and the cavity is sized and shaped to receive the guide portion of the head, resulting in a convexly rounded bearing surface and a concave contact surface. The abutment surfaces contact each other so as to simultaneously allow a relative rotational movement between the head and the cavity about its central axis and a swiveling of the longitudinal axis of the milling cutter with respect to the longitudinal axis of the guide piece.本発明は、フライス及びガイド片を備えるシステムに関する。このフライスは、長手方向軸線に沿って延びる細長いシャフトと、骨組織を除去するための少なくとも１つの周方向に配置された切れ刃を備えるフライス加工部を有する遠位端部とを備える。このガイド片は、ガイド片を支持構造体に解放可能に固定する固定要素と、長手方向軸線とを有する。ここで、ガイド片及びフライスの遠位端の一方は、ガイド片及びフライスの遠位端の一方の長手方向軸線と同軸の中心軸線を有するヘッドを備え、ガイド片及びフライスの遠位端の他方は、ガイド片及びフライスの遠位端の他方と同軸の中心軸線に沿って延びる内部空洞を備える。このヘッドは、ヘッドの軸平面にて凸状に丸みを帯びた軸受面を有するガイド部分を備え、この空洞は、空洞の軸平面にて凹状である当接面を有する案内部分を備える。この軸受面と当接面はその中心軸線回りに円形対称
