A fixation device at least partially implantable into tissue has a shaft having an outer face and a threaded portion wound around the outer face and forming a helical groove. At least a part of the threaded portion is implantable into tissue. The threaded portion includes a first face, a second face and a third face. The first face has a first end portion in curved contact with the outer face and a second end portion opposite the first end portion. The second face has a third end portion in curved contact with the outer face and a fourth end portion opposite the third end portion. The third face is coupled to the second end portion and the fourth end portion and is substantially parallel with the outer face.