A bone anchor system for anchoring a support member to a bone having a hole formed therein and a cavity formed at a distal end of the hole, the bone anchor system comprising a body (16, 62, 64) having: (i) a shank (22, 66) that has a proximal portion and a distal portion adapted for insertion into the hole; (ii) a head (20, 68) formed on the proximal portion of the shank (22, 66) and having a support engagement portion adapted to secure the support member to the body; and (iii) a passage (24, 70) extending from an entry point formed at the proximal portion to an exit point formed in the distal portion; and an expandable member (18, 72) having a flexible wall at least partially enclosing an anchoring chamber (38, 80), and having an expanded state configured to conform to the cavity, wherein the anchoring chamber (38, 80) is in fluid communication with the exit point, whereby the expandable member (18, 72) is adapted to expand when a filler material is provided into the entry point, passes through the passage (24, 70), passes out of the exit point, and into the anchoring chamber (38, 80), and whereby upon filling the anchoring chamber (38, 80) with the filler material a portion of the expandable member (18, 72) conforms to the cavity and the body (16, 62, 64) and the support member are substantially anchored to the bone, characterized in that the distal portion of the shank comprises the distal end of the shank, the flexible wall is disposed over the distal portion of the shank, the anchoring chamber (38, 80) containing the distal portion of the shank, and in that the distal portion configured such that upon filling the anchoring chamber (38, 80), at least the distal end of the distal portion of the shank (22, 66) is anchored in the filler material. (i) a shank (22, 66) that has a proximal portion and a distal portion adapted for insertion into the hole; (ii) a head (20, 68) formed on the proximal portion of the shank (22, 66) and having a support engagement portion adapted to secure the support member to the body; and (iii) a passage (24, 70) extending from an entry point formed at the proximal portion to an exit point formed in the distal portion; and an expandable member (18, 72) having a flexible wall at least partially enclosing an anchoring chamber (38, 80), and having an expanded state configured to conform to the cavity, wherein the anchoring chamber (38, 80) is in fluid communication with the exit point, whereby the expandable member (18, 72) is adapted to expand when a filler material is provided into the entry point, passes through the passage (24, 70), passes out of the exit point, and into the anchoring chamber (38, 80), and whereby upon filling the anchoring chamber (38, 80) with the filler material a portion of the expandable member (18, 72) conforms to the cavity and the body (16, 62, 64) and the support member are substantially anchored to the bone, characterized in that the distal portion of the shank comprises the distal end of the shank, the flexible wall is disposed over the distal portion of the shank, the anchoring chamber (38, 80) containing the distal portion of the shank, and in that the distal portion configured such that upon filling the anchoring chamber (38, 80), at least the distal end of the distal portion of the shank (22, 66) is anchored in the filler material.