Fig. 2. Representative case involving a 17-year-old female with atlanto-axial subluxation due to Down's syndrome. Preoperative X-ray shows irreducible atlanto-axial subluxation (A). After O–C2 fusion surgery, increase of O–C2 angle and decrease of subaxial lordosis was observed (B). O–C2 angle was –13° preoperatively and –2° postoperatively. C2–7 angle was 9° preoperatively and –11° postoperatively. O–C2, occiput–C2; Pre–OP, preoperative; Post–OP, postoperative.
