In Vitro Study of the Ilial Anatomic Landmarks for Safe Implant Insertion in the First Sacral Vertebra of the Intact Canine Sacroiliac Joint

Abstract

To define landmarks on the canine ilial wing for accurate, consistent insertion of implants into the 1st sacral (S1) vertebral body when the sacroiliac joint is intact. Anatomic study. Intact, cadaveric canine pelves and sacra (n=25). Median sections (5 specimens) were drilled from the center of S1 in a lateral direction, exiting on the ilial wing. Landmarks on the ilial wing and shaft used to define this exit point were then used to locate this point on both wings of 20 articulated specimens, positioned and rigidly held so that the dorsal plane of the pelvis was aligned with a plumb line and the median plane of the pelvis was horizontal. A 2 mm hole was drilled from the marked point, parallel to the plumb line, until it exited the contralateral ilial wing. Distance of drill hole position from the geometric center (GC) of S1 was located on median and paramedian plane images derived from plane, computed tomographic (CT) scans. The entire drill hole was located within S1 in 18 specimens. Mean deviation of the hole from GC (ratio of the distance of GC from the closest S1 body border) in median section was 0.40 +/- 0.29 (craniocaudal direction) and 0.29 +/- 0.23 (dorsoventral). Use of ilial wing landmarks and drilling perpendicular to the median plane will improve accuracy for insertion of implants into S1 when the sacroiliac joint is intact. Ilial wing landmarks should be used to improve accuracy of implant insertion into S1.