The anchor member (1) comprises an anchoring base (2) including a peripheral proximal wall (5) that inwardly delimits a proximal cavity, and a proximal stud (3) including a distal articulation portion (7) received in said proximal cavity, said proximal wall (5) including a peripheral proximal rim (6) ensuring retention of said distal articulation portion (7) in that proximal cavity. According to the invention, -the distal articulation portion (7) has a peripheral edge dimensioned to come into the immediate vicinity of the inner surface of said proximal wall (5), and has a convex distal surface (9) whereof the apex is situated substantially at the axis of the proximal stud (3)； and -the anchor member (1) comprises an elastically deformable element (10) placed in the bottom of said proximal cavity, having a curved shape whereof the apex is situated substantially at the axis of said proximal cavity, the surface (9) bearing against this element (10), and the latter being permanently elastically deformed such that it continuously presses said portion (7) against said rim (6)
