A shoulder assembly is provided which includes a base member including a collar; a helical structure extending from the collar in a distal direction; and a first pathway projecting distally of the collar and through the helical structure adjacent to an inner periphery thereof, the first pathway being generally transverse to the helical structure and extending in a space between successive portions of the helical structure; and a locking device comprising a proximal support and a first arm projecting distally of the proximal support, the first arm configured to be disposed in the first pathway projecting distally of the collar when the proximal support is disposed adjacent to the collar; where the first arm is disposed through bone in the space between successive portions of the helical structure when the shoulder assembly is implanted.