A first arched slot or slit connection element (15) and a second linear slot or slit connection element (19, 21) are provided for cursors (13, 30) which can slide and be locked along said slots or slits the connection element engaged with the humeral stem is self-centring and is provided with a hinge (32, 34) defining the articulation axis of the elbow, when—after repeated flexion-extension—said cursor is no longer subject to significant movements.
