A cannula (1) comprising A) a central axis (2), a front end (3), a rear end (4) and a channel (5) coaxial or parallel to said central axis (2) and defining a peripheral wall (12) of said cannula (1); B) referencing means (15) at said rear end (4), so that said cannula (1) can be brought in a desired position relative to a cavity (120) in a bone; wherein C) said cannula (1) further comprises at least two perforations (8) penetrating said peripheral wall (12) transversely to said central axis (2); and D) said at least two perforations (8) are arranged in a portion (16) of said peripheral wall (12) which extends over an arc (18) orthogonal to said central axis (2) with a central angle α