An outer tube and an inner tube rotatably disposed within the outer tube, the inner tube comprising an opening having a leading edge and a trailing edge, the outer tube comprising a window having a leading edge and a trailing edge, At least one of the leading edge of the opening, the trailing edge of the opening, the leading edge of the window, and the trailing edge of the window comprises a beveled edge and the window of the outer tube, during the rotation of the inner tube in the outer tube, A cutting instrument adapted to be completely blocked by an inner tube.外管と、外管内で回転可能に配設された内管と、を備え、内管が前縁および後縁を有する開口部を備え、外管が前縁および後縁を有する窓を備え、開口部の前縁、開口部の後縁、窓の前縁、および窓の後縁の少なくとも1つが傾斜縁部を備え、外管の窓が、外管内で内管が回転する段階の間、内管によって完全に遮断されるように適合された、切断器具。
