The anchor member (1) includes an anchoring base (2) having a peripheral proximal wall (5) that inwardly delimits a proximal cavity, and a proximal stud (3) including a distal articulation portion (7) received in the proximal cavity, the proximal wall (5) including a peripheral proximal rim (6) ensuring retention of the 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 the 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) includes 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 the proximal cavity, the surface (9) bearing against this element (10), and the latter being permanently elastically deformed such that it continuously presses the portion (7) against the rim (6)
