A system for the amelioration of a recess, particularly of a recess in a porous, perforate material having cavities freed by the recess, said system comprising an element for generating or coupling in mechanical energy, a guide pin, and a cylindrical collar having a central recess (44,45) for receiving said guide pin, wherein said guide pin, in the area of the end thereof configured to be directed toward the bottom of the recess, is surrounded by an amelioration sleeve made from a material that can be liquefied by mechanical energy, wherein the external circular cylindrical jacket surface of the amelioration sleeve has substantially the same external diameter as the external circular cylindrical jacket surface of the collar, wherein said guide pin is received movably in the central recess (44,45) such that, when mechanical energy is applied, said collar can be moved relative to said guide pin in the direction toward the bottom of the recess while liquefying and laterally and/or longitudinally displacing the material of said amelioration sleeve, wherein said external diameter of the external circular jacket surface of the cylindrical collar and said external diameter of the external circular jacket surface of the amelioration sleeve are substantially the same as the internal diameter of the recess to be ameliorated, and wherein the collar, at its distal end, has a circumferential distal edge tapering toward said distal end, wherein this distal edge is either straight, and therefore conical, or curved, in particular concave or convex, or has a radially stepped design at the distal end, wherein the circumferential distal edge is arranged at the step transition, and wherein the amelioration sleeve is a simple hollow cylinder, characterized in that the guide pin has an axial central through bore in the form of a cannulation, and is provided and configured to be inserted substantially as far as the bottom of the recess under positioning using a wire inserted into said cannulation of the guide pin, before mechanical energy is applied. an element for generating or coupling in mechanical energy, a guide pin, and a cylindrical collar having a central recess (44,45) for receiving said guide pin, wherein said guide pin, in the area of the end thereof configured to be directed toward the bottom of the recess, is surrounded by an amelioration sleeve made from a material that can be liquefied by mechanical energy, wherein the external circular cylindrical jacket surface of the amelioration sleeve has substantially the same external diameter as the external circular cylindrical jacket surface of the collar, wherein said guide pin is received movably in the central recess (44,45) such that, when mechanical energy is applied, said collar can be moved relative to said guide pin in the direction toward the bottom of the recess while liquefying and laterally and/or longitudinally displacing the material of said amelioration sleeve, wherein said external diameter of the external circular jacket surface of the cylindrical collar and said external diameter of the external circular jacket surface of the amelioration sleeve are substantially the same as the internal diameter of the recess to be ameliorated, and wherein the collar, at its distal end, has a circumferential distal edge tapering toward said distal end, wherein this distal edge is either straight, and therefore conical, or curved, in particular concave or convex, or has a radially stepped design at the distal end, wherein the circumferential distal edge is arranged at the step transition, either straight, and therefore conical, or curved, in particular concave or convex, or has a radially stepped design at the distal end, wherein the circumferential distal edge is arranged at the step transition, and wherein the amelioration sleeve is a simple hollow cylinder, characterized in that the guide pin has an axial central through bore in the form of a cannulation, and is provided and configured to be inserted substantially as far as the bottom of the recess under positioning using a wire inserted into said cannulation of the guide pin, before mechanical energy is applied.