Indications and limitations of three-dimensional models in cranio-maxillofacial surgery.

Anatomical, life-like, three-dimensional (3D) models have a definite place in cranio-maxillofacial surgery. Our experience with 541 computer tomography (CT)-based 3D models employed in aiding corrective surgery of tumours, dysgnathia, traumatology, alveolar atrophy, congenital malformation and asymmetrical malformations in our department is discussed. From July 1988 to February 1997, 3D models of 346 patients were used. Most of these were produced at our clinic. The indications, advantages and limitations of 3D-models were analysed retrospectively. In the case of congenital malformations (n = 60), models facilitated precise diagnosis of the skeletal deformity. Simulation surgery allowed prediction and solution of intraoperative problems prior to the actual patient operation. Size, shape and localization of defects caused by trauma (n = 64), osteoradionecrosis (n = 17) or osteomyelitis (n = 2) determined the choice of transplant donor site. In patients suffering from dysgnathia (n = 144), 3D models enabled exact positioning of the jaws. Precise planning could only be accomplished with the help of 3D models, especially for asymmetrical malformations (n = 12). In cases of severe atrophy of the alveolar crest (n = 45), exact measurement of the bone was possible and facilitated the decision as to whether dental implants, bone transplants or a combination of these were indicated. The positioning of transplants and implants was carried out in the ideal relation to the opposite jaw. In tumour patients (n = 186), it is not always possible to identify the tumour borders precisely on the CT scan or 3D model. Therefore, the defect was assumed to be bigger, a longer bridging plate constructed and this measurement corrected according to the intraoperative situation. The advantage of the 3D models consisted of an accurate representation of anatomical structures, bone or soft tissue. This allows precise preoperative diagnosis, operation planning and model operations. Due to this, the correct approach as well as operation technique could be chosen, outcomes of constant high quality were achieved, and there was a reduction in operation time.