Posterior iliac osteotomy in ischiopagus tetrapus twins

Eight hemipelvises in ischiopagus tetrapus conjoined twins were assessed retrospectively to determine whether posterior iliac osteotomy is appropriate to reconstruct pelvic symmetry. Although clinical and radiological similarity exists with classic bladder exstrophy, axial and three-dimensional computed tomography showed the pelvic deformity to be very different. In classic bladder exstrophy, the deformity is one of shortening and external rotation of the anterior segment, and external rotation of the posterior segment. The deformity in the ischiopagus tetrapus pelvis is purely one of external rotation of the posterior segment. Posterior iliac osteotomy alone was therefore able to restore pelvic symmetry in seven of the eight hemipelvises, and prevented rediastasis of the symphysis pubis in all patients.