Pedicle morphology of the first sacral vertebra

Received 4 April 2003; accepted 24 April 2003 ABSTRACT Posterior transpedicular screw fixation has been widely used for the management of unstable lumbosacral spine caused by trauma, degenerative conditions, congenital defects and neoplasms. Knowledge of the pedicle diameters of the first sacral vertebra is crucial for safe placement of the screws. Thirty dry sacral specimens (18 male, 12 female) were used for study of the first sacral pedicles. Cephalad-caudad height, anterior-posterior width, transverse and sagittal angles, and depth of S1 pedicle were presented. The mean width of the pedicles were estimated as 22.5±2.6 mm and 22.2±2.8 mm; the heights were 13.6±2.3 mm and 13.6±2.7 mm; the depths were 50.7±3.7 mm and 51.8±3.5 mm for female and male, respectively. The mean transverse angles were 43°±2.3 and 41°±2.2; the sagittal angles were 19°±2.9 and 19°±3.7 for female and male, respectively. The depth and the angle of screw trajectory is as important as entrance point for pedicular screw placement to the S1 to avoid injury to the vascular structures anteriorly and nerve roots medially.