Iterative Virtual and Physical Simulation for Staged Separation of Total Vertical Craniopagus: The Avatar Patient Approach to Conjoined Twins

BACKGROUND AND OBJECTIVES: Total vertical craniopagus represent one of the most complex craniofacial malformations and a demanding surgical challenge. Traditional imaging remains static and insufficient to fully anticipate dynamic venous redistribution during staged separation. We implemented an integrated virtual and physical simulation framework in the multistep separation of total vertical craniopagus twins, within an Avatar Patient Approach as an evolution of the Digital Twin Medicine approach focused on controlled physiological decoupling and operative risk reduction. METHODS: Multimodal imaging Data sets were coregistered into a unified 3-dimensional anatomic space. These Data sets generated a dual avatar system: (1) immersive, multiuser virtual reality models within a collaborative metaverse; and (2) operable, multimaterial physical simulators enabling layered manual rehearsal. Both virtual and physical avatars were iteratively updated after each surgical stage, transforming simulation from a single preoperative event into a longitudinal adaptive workflow. RESULTS: The integrated simulation reshaped the multistep approach, allowing venous partition strategies and refined cranial reconstruction planning to be discussed, replicated, and enhanced multidisciplinarily. Iterative model updating allowed anticipation of anatomic evolution between steps and facilitated scenario testing under alternative surgical hypotheses. Mental training was intended to support the development of 3-dimensional anatomic imagination, cognitive automatism, and surgical strategy definition. The platform helped reduce procedural uncertainty during planning and supported strategic decision-making. CONCLUSION: Twin Medicine through dynamic virtual and physical avatars, redefines craniopagus separation surgery as a continuously adapting digital-physical continuum rather than a sequence of isolated operations. This paradigm establishes an iterative framework for managing extreme surgical complexity in pediatric neurosurgery.