[Third dimension and craniofacial plastic surgery].

Via an inverse approach to that of the Renaissance painter's treatment of perspective, the third dimension must be obtained from flat radiological information in order to reconstitute (virtually and materially) the volumes which it analyses. These images are analysed mathematically by computer. The applications are and will be numerous, especially in cranio-maxillo-facial surgery. Surgical simulation, without claiming to assess their soft tissue repercussions, section and virtually reposition bone segments: symmetrization and correction of hypotrophy are easy to visualize; computer-assisted surgical teaching applications (endoscopic surgery) are discussed. Multimodal images superimpose information from various sources: operative views and pre-recorded images are available to the surgeon and guide him in his "surgical navigation". Prototyping of skeletal anatomical specimens (prior to tumour or soft tissue specimens) provides the therapist with a precise preoperative spatial configuration of the abnormalities to be corrected, and the reconstructions to be performed. These developments, and others to come, are the sole objective of 3D imaging, beautiful in itself, but ineffective alone.