Pelvic CT morphometry in Down syndrome: implications for prenatal US evaluation-preliminary results

PURPOSE: To characterize pelvic morphometric differences in patients with a nd those without Down syndrome by using computed tomography (CT) and to det ermine useful indexes for ultrasonographic (US) evaluation. MATERIALS AND METHODS: Pelvic CT scans in seven patients with Down syndrome and in 27 patients without Down syndrome were reviewed. Iliac angle, iliac length, sacroiliac joint angle, and anterior iliac wing separation were me asured at superior, middle, and inferior transverse sacral levels. The effe cts of chromosomal status and transverse level were evaluated statistically . RESULTS: Significant differences were found for: mean iliac angle (P < .007 ) and length (P <.005) between patients without Down syndrome(angle, 75 deg rees; length, 8.4 cm) and those with Down syndrome (angle, 82 degrees; leng th, 7.5 cm). Depending on the level of measurement, variations in iliac ang le between patients without and those with Down syndrome were as much as 13 degrees and 15 degrees, respectively,and variations in length were as much as 1.6 cm and 0.9 cm, respectively, The greatest differences were at the m iddle sacral level. Sacroiliac joint angle and the anterior iliac wing sepa ration were not different between groups. CONCLUSION: Patients with Down syndrome had a larger mean iliac: angle and a:shorter mean iliac length. The most pronounced differences were at the mi ddle sacral level, which suggests that this may be the optimal level for me asuring these parameters at prenatal US.