RADIOGRAPHIC RECOGNITION OF THE SACRAL ALAR SLOPE FOR OPTIMAL PLACEMENT OF ILIOSACRAL SCREWS - A CADAVERIC AND CLINICAL-STUDY

Malpositioning of iliosacral screws happens more often when common var iations in the morphology of the upper sacral segments are unrecognize d. Radiological-anatomic correlations of sacral anatomy were studied i n 10 fresh-frozen cadaveric pelvises without evidence of skeletal dise ase, obtained from six male and four female donors. Eighty consecutive patients with complicated pelvic fractures treated operatively by the same surgeon using percutaneously placed iliosacral screws were evalu ated. Variations in the sacral alar anatomy and slope found in upper s acral segmentation anomalies are common. Surgically important and pred ictable abnormal morphological patterns can be easily identified using pelvic outlet and lateral sacral plain radiographs along with compute d tomographic scans. On the true lateral projections, the iliac cortic al density adjacent to the sacroiliac joint parallels the sacral alar slope and is almost always caudal and posterior to it; it delineates t he anterior extent of the ''safe zone'' for iliosacral screw insertion . Thus, the lateral sacral image provides the surgeon with a better un derstanding of the sacral alar slope and can help prevent iliosacral s crew placement errors. The lateral sacral image should always be used intraoperatively with the inlet and outlet images to guide iliosacral screw placement.