A surgical instrument comprising: a first cutting blade having a tubular body with a proximal end and a distal end, a cutting window disposed at a first side of the first cutting blade near the distal end, a suction aperture disposed at a second side of the first cutting blade near the distal end; a second cutting blade having a tubular body with a proximal end and a distal end, a cutting window disposed at a side of the second cutting blade near the distal end, the second cutting blade rotatably disposed inside of the first cutting blade such that the surgical instrument cuts tissue by rotating the second cutting blade within the first cutting blade while a vacuum is applied through an internal bore of the second cutting blade to draw the tissue into the cutting windows of the first and second cutting blades and sever the tissue by rotation of the second cutting blade; characterised in that the surgical instrument further comprises: a suction passage forming member (50, 80) disposed over the suction aperture of the first cutting blade, the suction passage forming member including an inlet (52, 82), an outlet (56, 86) and a passage (54, 84) between the inlet and the outlet, the outlet communicating with the suction aperture, the inlet facing distally, wherein the surgical instrument can be used as a suction tool by applying the vacuum through the internal bore of the second cutting blade while the second cutting blade is stopped from rotating with the cutting windows of the first and second cutting blades misaligned with each other so that the vacuum is applied through the suction aperture and the suction passage forming member. a first cutting blade having a tubular body with a proximal end and a distal end, a cutting window disposed at a first side of the first cutting blade near the distal end, a suction aperture disposed at a second side of the first cutting blade near the distal end; a second cutting blade having a tubular body with a proximal end and a distal end, a cutting window disposed at a side of the second cutting blade near the distal end, the second cutting blade rotatably disposed inside of the first cutting blade such that the surgical instrument cuts tissue by rotating the second cutting blade within the first cutting blade while a vacuum is applied through an internal bore of the second cutting blade to draw the tissue into the cutting windows of the first and second cutting blades and sever the tissue by rotation of the second cutting blade; characterised in that the surgical instrument further comprises: a suction passage forming member (50, 80) disposed over the suction aperture of the first cutting blade, the suction passage forming member including an inlet (52, 82), an outlet (56, 86) and a passage (54, 84) between the inlet and the outlet, the outlet communicating with the suction aperture, the inlet facing distally, wherein the surgical instrument can be used as a suction tool by applying the vacuum through the internal bore of the second cutting blade while the second cutting blade is stopped from rotating with the cutting windows of the first and second cutting blades misaligned with each other so that the vacuum is applied through the suction aperture and the suction passage forming member. a suction passage forming member (50, 80) disposed over the suction aperture of the first cutting blade, the suction passage forming member including an inlet (52, 82), an outlet (56, 86) and a passage (54, 84) between the inlet and the outlet, the outlet communicating with the suction aperture, the inlet facing distally, wherein the surgical instrument can be used as a suction tool by applying the vacuum through the internal bore of the second cutting blade while the second cutting blade is stopped from rotating with the cutting windows of the first and second cutting blades misaligned with each other so that the vacuum is applied through the suction aperture and the suction passage forming member.