Surgical instrument (1, 200) for performing an incision at a free edge of a portion of tissue, comprising first and second pivoting legs (2, 6) movable towards each other with respect to a fixed end, and defining a receiving space between the legs configured to receive the free edge of the portion of tissue, the surgical instrument having an initial position with relatively opened legs and a closed position, where no further closing movement of the pivoting legs towards each other is possible, a tissue perforating member located at a free end of the first leg and extending into the receiving space at a distance from the fixed end, such that when the legs are in the closed position, the tissue can be perforated at a perforation location separated from the free edge of the tissue, while an uncut tissue band remains between the perforation location and the free edge, wherein the perforating member comprises a cutting edge facing the fixed end, such that movement of the surgical instrument in the direction of the free edge will cause incision of the tissue band, wherein the perforator is a blade, preferably having two opposed cutting edges, the surgical instrument further comprising an intermediate third leg in between the first and second legs (2, 6) and fixed with respect to the second leg, the receiving space being defined by the space between the second and third legs and wherein the third leg comprises a slit at its free end for accommodating movement of the perforating member between the initial position and the closed position, wherein the third leg comprises a pivot groove for accommodating a protruding member of the first leg to form a hinge such that the first leg can pivot in relation to the third leg, and the surgical instrument further comprising a safety mechanism at the free end of the third leg arranged to selectively retain the first leg in the initial position, such that the perforating member does not enter the receiving space, the safety mechanism being releasable to allow movement of the first leg to the closed position, and wherein the safety mechanism comprises an elongated member configured such that when the surgical instrument is in the initial position it covers the perforating member, closing a space between the free ends of the first and third legs. first and second pivoting legs (2, 6) movable towards each other with respect to a fixed end, and defining a receiving space between the legs configured to receive the free edge of the portion of tissue, the surgical instrument having an initial position with relatively opened legs and a closed position, where no further closing movement of the pivoting legs towards each other is possible, a tissue perforating member located at a free end of the first leg and extending into the receiving space at a distance from the fixed end, such that when the legs are in the closed position, the tissue can be perforated at a perforation location separated from the free edge of the tissue, while an uncut tissue band remains between the perforation location and the free edge, wherein the perforating member comprises a cutting edge facing the fixed end, such that movement of the surgical instrument in the direction of the free edge will cause incision of the tissue band, wherein the perforator is a blade, preferably having two opposed cutting edges, the surgical instrument further comprising an intermediate third leg in between the first and second legs (2, 6) and fixed with respect to the second leg, the receiving space being defined by the space between the second and third legs and wherein the third leg comprises a slit at its free end for accommodating movement of the perforating member between the initial position and the closed position, wherein the third leg comprises a pivot groove for accommodating a protruding member of the first leg to form a hinge such that the first leg can pivot in relation to the third leg, and the surgical instrument further comprising a safety mechanism at the free end of the third leg arranged to selectively retain the first leg in the initial position, such that the perforating member does not enter the receiving space, the safety mechanism being releasable to allow movement of the first leg to the closed position, and wherein the safety mechanism comprises an elongated member configured such that when the surgical instrument is in the initial position it covers the perforating member, closing a space between the free ends of the first and third legs.