A 3-D System for Planning and Simulating Minimally-Invasive Distraction Osteogenesis of the Facial Skeleton

Three-dimensional planning tools will enable the use of minimally-invasive distraction osteogenesis for the correction of craniomaxillofacial deformities by simulating treatment, precisely quantifying movement vectors, and aiding pre and post-treatment evaluation. Current techniques extrapolate 3D surgical movements and outcomes based on standard 2D radiographs. Surgical planning and outcome evaluation would be greatly improved by an accurate, reproducible and reliable 3D treatment planning system. Building upon a software foundation that includes the 3D Slicer of the Brigham & Women’s Hospital, and the Visualization Toolkit (VTK) of Schroeder, Martin & Lorensen, we add algorithms that support interactive cutting of large triangulated surface models, collision detection, landmark-based registration, and cephalometric analysis. The oriented bounding-box tree (OBB tree) structure is used throughout to enhance the interactivity of selection, collision detection, and cutting. The cutting tool is notable for its generality and preservation of topological closure in the resultant models. In a retrospective case study, the collision of the proximal fragment of the distracted mandible with the skull base is detected and the resulting 3D bone movements are quantified. The distracted bone volume is computed. In prospective cases, this system will be used to compute the placement and configuration of appropriate buried distractor(s).