Fig. 2

a Anterior (ASL) and posterior sacral length (PSL) measurement on the sagittal plane. b Anterior (ASCL) and posterior sacrococcygeal length (PSCL) measurement on the sagittal plane. c Anterior sacral curvature length (ASC) and posterior sacral curvature length (PSC), anterior coccygeal curvature length (ACC), and posterior coccygeal curvature length (PCC) measurement on the sagittal plane. d Sacral (SA) and coccygeal area (CA) measurement on the sagittal plane