RECONSTRUCTION OF CRANIOFACIAL BONE DEFECTS WITH INDIVIDUAL ALLOPLASTIC IMPLANTS BASED ON CAD CAM-MANIPULATED CT-DATA/

Reconstruction of craniofacial bone defects by intraoperative modellin g of autogenous or alloplastic materials may cause undesirable results concerning the implant shape or the long-term maintenance of this sha pe, Furthermore, the use of alloplastic materials to be modelled intra operatively may result in an inflammatory tissue response. Therefore t he question is raised whether CAD/CAM-techniques may be used for the p re-operative geometric modelling of the implant based on helical compu ted tomography data. A numerically based 3-dimensional model of the sk ull defect serves as the basis for a freeform-surfaces design of the i mplant shape, position and thickness, using modelling tools and progra mmes developed for industrial CAD/CAM. The precise and individual fit of the implant results from generating its margins by the borders of t he defect, whereas the implant surface is generated by the geometry of the non-affected neighbouring bone contours. The implant data run a n umerically controlled milling machine to fabricate the individual impl ant. The reconstruction of post-traumatic defects of the forehead, of post-surgical temporal defects after intracranial haemorrhage, and of a parieto-occipital defect due to ablative tumour surgery are presente d as the first clinical experiences of this new method.