A suture anchor retaining a suture is fixated in hard tissue, in particular in bone tissue, using any per se known method and is then secured using a securing element including a material having thermoplastic properties, which is liquefied in situ and made to penetrate the hard tissue in which the suture anchor is fixated. The securing element is e.g. a thermoplastic plug or thermoplastic sleeve which is anchored above the suture anchor in a mouth area of the same hard tissue opening. Alternatively the securing element is a thermoplastic pin which is introduced into an inner cavity of the suture anchor, wherein the material having thermoplastic properties is liquefied in this cavity and, in a liquid state is pressed through passages connecting the cavity with outer surfaces of the anchor.