THE PROJECTION OF THE LATERAL SACRAL MASS ON THE OUTER TABLE OF THE POSTERIOR ILIUM

Study Design. This study was designed to construct the projection of t he lateral sacral mass on the posterior ilium using cadaveric pelves a nd to measure the dimensions of the projection. Objectives. The presen t study was undertaken to determine quantitatively the location of the lateral sacral mass on the outer table of the ilium. Summary of Backg round Data. Anatomic studies relative to instrumentation of the poster ior iliosacral region are few. No previous anatomic studies with regar d to the projection of the lateral sacral mass have been reported. Met hods. Twelve cadaveric pelves were used for this study. To determine t he projection of the lateral sacral mass on the outer table of the pos terior ilium, several Kirschner wires were drilled along the outermost peripheral edge of the lateral sacral mass from the inner table of th e ilium through the outer table. A triangle projection on the outer ta ble of the posterior ilium was then constructed according to the place d Kirschner wires. The widths and height of the projection, and the di stances from the axis of the projection to posterior superior iliac sp ine and posterior inferior iliac spine were measured bilaterally. Resu lts. The average height of the projection of the lateral sacral mass w as 61.4 mm. The average base width of the projection was 56.8 mm. The average distances from posterior superior iliac spine and posterior in ferior iliac spine to the longitudinal axis of the projection of the l ateral mass were 30 mm and 27.4 mm, respectively. Conclusions. This st udy reported the average location of the lateral sacral mass on the ou ter table of the ilium. The superior area of the projection may be an ideal zone for transiliosacral screw placement.