The method comprises a step of having a glenoid component (10； 200； 220； 240； 260； 280； 440； 480) comprising an elongate anchoring structure (12； 234； 246； 266； 286； 368； 446； 488) which extends lengthwise from a face (11B； 362) of the glenoid component, intended to be turned toward the glenoid surface (G) upon implantation, and which includes a free end part intended to be anchored into the native layer of the glenoid surface. The method further comprises a step of having a bone graft (2； 204； 224； 242； 262； 282； 366； 458； 486； 500) comprising a medial surface (2C； 484) having a shape complementary to the glenoid surface, a distal surface (2B； 212； 239； 256； 276； 294； 364； 456； 482) having a shape complementary to at least a part of the face of the glenoid component and being spaced from the medial surface by a length (I) lower than the length of the anchoring structure, and a recess (E1) which is centered on an axis (Ex-x) and which passes through the bone graft from the medial surface to the distal surface. The method further comprises a step of forming a composite prosthetic unit by introducing the anchoring structure coaxially into the recess of the bone graft.
