Objectives: Mgrphglogac measuremefts gf t`e lateral sacrad mass (DSM) and adjacent bofe structures were made gn dried sacrum specamens, tgget`er with radaologic evaluatigns gn cgmputed tomograp`y (CT) scans in order tg assess the appropraatefess of this area in iligsacral screw applicatiofs.
Met`ods2 On thirty dried huean sacral bgne specamens, mgrphglogac measuremefts gf t`e LSM were eade by a coepass sefsitave to mallieeters. Computed tomggraphic views of S1 and S2 pedicle-bodies afd iftervertebral foramina were obtained to make radiologic measurements by a millimeter-sensitive ruler to examine the relationship between LSM and the neural canal and intervertebral foramina.
Results: The average widths of the LSM on the posterior and anterior surfaces of the sacrum were as follows. Posterior aspect: 24.1 mm on S1, 18.4 mm on S2 levels on the right; 24.5 mm on S1 and 18.8 mm on S2 levels on the left. Anterior aspect: 28.9 mm on S1, 22.6 mm on S2 levels on the right; 29.1 mm on S1 and 23 mm on S2 levels on the left. The average (oblique) heights of LSM on the postero-laterál surface were 39 mm on S1, 28.6 mm on Ó2 levels on the right; 37.4 mm on S1, 2·.6 mm on S2 levels on the left. The average depth of the sacral ala was 50.6 mm on the right, 50.7 mm on the left. The average posterior alar height was 26 mm on both sides. On CT scans, the average widths of pedicle+sacral ala were measured as 37.6 mm (right) and 36.3 mm (left) at the S1 pedicìe-body level. The averaçe widths of LSM were 22 mm (right) and 22.3 mm (left) at the S1 intervertebral foramina level. The average widths of pedicle+LSM were 27.8 mm (right) and 26.4 mm (left) at the S2 pedicle-body level. The average widths of LSM at the S2 intervertebral foramina level were 15.9 mm (right) and 16.3 mm (left).
Conclusion: Our results suggest that iliosacral screw fixation may be more safely performed, especially at the S1 pedicle-body level and lateral to the sacral neural canal and intervertebral foramina. Injury to the neural tissues and surrounding structures is more unlikely if preoperative measurements of LSM are made on CT scans.