Congenital vertebral anomalies in ischiopagus and pyopagus conjoined twins

A review of clinical records and radiographs revealed that five of 10 patie nts with conjoined twinning (three of six ischiopagus and two of two pyopag us twins) had congenital vertebral anomalies including hemivertebrae (3), m ultiple thoracic anomalies (1), right hemisacral agenesis (1), and three lu mbar vertebra (1), No mirror image anomalies were identified, and different regions of the spine were involved in the two cases in which both twins ha d anomalies. Coexisting visceral and musculoskeletal anomalies included dex trocardia (3), atrial septal defect (1), congenital vertical talus (2), Spr engel's deformity (1), and multiple unilateral foot anomalies (1), Hip subl uxation or dislocation was seen in five of eight ischiopagus or pyopagus tw ins after separation and required femoral and pelvic osteotomies. Lumbar sc oliosis not associated with congenital vertebral anomalies was seen in two ischiopagus twins. These observations suggest an association between ischio pagus and pyopagus conjoined twins and congenital vertebral anomalies, and their coexistence is explained best by a nonspecific teratogenic insult dur ing early embryogenesis.