Sacrum and coccyxOnline version anterior and lateral aspects labeled by Michon Perre 1 (A) Sacral promontory 2 (A) Pelvic sacral foramina 3 (A) Apex 4 (A) Base 5 (A) Apex 6 (A) Coccyx 7 (A) Sacrum 8 (A) 1st 9 (A) 2nd 10 (A) 3rd 11 (A) 4th 12 (A) 5th 13 (A) 1st 14 (B) Superior articular process 15 (B) Base 16 (B) Promontory 17 (B) Articular surface 18 (B) Sacrum 19 (B) Coccygeal cornu 20 (B) Coccyx 21 (B) Sacral cornu