ABSTRACT: Normal pelvis is generally considered symmetric with respect to the sagittal plane. Although a scoliotic spine exhibits curve asymmetry in the coronal plane it is yet to be established whether it is also accompanied by pelvic deformity. Radiographic measurements in the coronal plane are not always aligned. It is therefore difficult to gauge if the apparent pelvic rotation is due to global rotation in the radiographic plane or a true pelvic deformation attributed to the scoliotic deformity. Our objective was therefore to examine pelvic deformity in the transverse plane after eliminating any orientation misalignment due to global rotation in the radiographic plane. 43 AIS patients (26 Lenke-1, 7 Lenke-5), and 29 normal controls, reviewed by the 3D Classification Committee of the SRS, were evaluated using 3D reconstructions of coronal and lateral standing radiographs. This allowed computing 3 vertical axes passing through the center of the pubis (CPVA), the middle of the femoral head axis (CHVA) and the central sacral vertical line (CSVL). Their coplanarity was analyzed with and without mathematically realigning the femoral heads in the coronal plane. If the 3 axes were inside a corridor of +/-2 mm before and after realigning the femoral heads, the pelvis was considered as being 'normal' and symmetric. The pelvis was considered as deformed if the 3 axes were outside the +/-2 mm limits (before and after realigning the femoral heads in the coronal plane). 35% of Lenke-1 patients had a deformed pelvis while it reaches 47% for Lenke-5 cases. Only two Lenke-1 patients were globally rotated with respect to the radiographic plane. No pelvis deformity was observed in 86% of the control group. Deformation of the pelvis is frequent, even in thoracic scoliosis. Asymmetry of the iliac wings in the transverse plane is a true deformity of the pelvis in AIS. The cause of this deformity and its link with the deformation of the scoliotic spine needs to be further investigated.
Studies in health technology and informatics 02/2008; 140:368.