In a human or animal patient, two bone portions separated by a cut or fracture are stabilized in a desired position relative to each other by bringing the two bone portions into this desired position, by pulling them against each other, by providing an opening having a mouth on a bone surface and reaching across the cut or fracture and walls in both bone portions, by inserting an implant into the opening and anchoring the implant in the walls of the opening with the aid of a material having thermoplastic properties and energy transmitted into the implant for in situ liquefaction of at least part of the material having thermoplastic properties. One exemplary application of the stabilizing procedure concerns the two tibial bone portions separated by tibial plateau leveling osteotomy in a canine patient suffering from cranial cruciate ligament damage or rupture in a stifle joint.