A clip for a generally U-shaped osteosynthesis, comprising: - at least two anchoring bars (2, 3) corresponding to the two vertical bars of the U-shape, each anchoring bar comprising a distal end (2a, 3a), intended to be inserted into a bone element (30, 40), and a proximal end (2c, 3c), and - at least one linking bar, corresponding to the horizontal bar of the U-shape, linking together the respective proximal ends of both anchoring bars, said linking bar comprising at least a longitudinal opening dividing it into two opposite side walls (6, 7) linked together at their ends, deformable in the plane P containing the linking bar and perpendicular to the plane containing the U-shaped clip, so that the opening is able to adopt a closed configuration, wherein both anchoring bars are substantially parallel to each other and said two side walls are moved closer to each other so that the distance between both proximal ends of both anchoring bars has a value L1, and at least an open configuration, wherein the central zones of said two side walls are moved away from each other on either side of said opening, and the distance between both proximal ends of both anchoring bars has a value L2 strictly lower than L1, characterized in that said clip further comprises a compression member having at least a portion called active portion (21 a, 21 b), whose section in a plane A of said member has a generally oval shape, said member being housed into said opening with its plane A coincident with said plane P and at least part of the outer face of its active portion in contact with at least part of the inner faces of said two side walls of the linking bar, said member being able to be rotated around an axis B passing through the center of said oval shape of said active portion and perpendicular to said plane P, causing thus the passage of said opening from its closed configuration to at least one said open configuration, and vice versa. - at least two anchoring bars (2, 3) corresponding to the two vertical bars of the U-shape, each anchoring bar comprising a distal end (2a, 3a), intended to be inserted into a bone element (30, 40), and a proximal end (2c, 3c), and - at least one linking bar, corresponding to the horizontal bar of the U-shape, linking together the respective proximal ends of both anchoring bars, said linking bar comprising at least a longitudinal opening dividing it into two opposite side walls (6, 7) linked together at their ends, deformable in the plane P containing the linking bar and perpendicular to the plane containing the U-shaped clip, so that the opening is able to adopt a closed configuration, wherein both anchoring bars are substantially parallel to each other and said two side walls are moved closer to each other so that the distance between both proximal ends of both anchoring bars has a value L1, and at least an open configuration, wherein the central zones of said two side walls are moved away from each other on either side of said opening, and the distance between both proximal ends of both anchoring bars has a value L2 strictly lower than L1, characterized in that said clip further comprises a compression member having at least a portion called active portion (21 a, 21 b), whose section in a plane A of said member has a generally oval shape, said member being housed into said opening with its plane A coincident with said plane P and at least part of the outer face of its active portion in contact with at least part of the inner faces of said two side walls of the linking bar, said member being able to be rotated around an axis B passing through the center of said oval shape of said active portion and perpendicular to said plane P, causing thus the passage of said opening from its closed configuration to at least one said open configuration, and vice versa.