Study design: This study was designed to construct the projection of the lateral sacral mass on the posterior ilium using cadaveric pelves and to measure the dimensions of the projection.
Objectives: The present study was undertaken to determine quantitatively the location of the lateral sacral mass on the outer table of the ilium.
Summary of background data: Anatomic studies relative to instrumentation of the posterior iliosacral region are few. No previous anatomic studies with regard to the projection of the lateral sacral mass have been reported.
Methods: Twelve cadaveric pelves were used for this study. To determine the projection of the lateral sacral mass on the outer table of the posterior ilium, several Kirschner wires were drilled along the outermost peripheral edge of the lateral sacral mass from the inner table of the ilium through the outer table. A triangle projection on the outer table of the posterior ilium was then constructed according to the placed Kirschner wires. The widths and height of the projection, and the distances from the axis of the projection to posterior superior iliac spine and posterior inferior iliac spine were measured bilaterally.
Results: The average height of the projection of the lateral sacral mass was 61.4 mm. The average base width of the projection was 56.8 mm. The average distances from posterior superior iliac spine and posterior interior iliac spine to the longitudinal axis of the projection of the lateral mass were 30 mm and 27.4 mm, respectively.
Conclusions: This study reported the average location of the lateral sacral mass on the outer table of the ilium. The superior area of the projection may be an ideal zone for transiliosacral screw placement.