In craniofacial surgery bone fractures and repositioned bone segments often have to be fixed by titanium miniplates. In clinical routines the surgeon has to fit each miniplate to be used to the individual bone structure of the patient: bending and fitting of a miniplate must frequently be repeated several times. Often up to twenty minutes are required to achieve the best fit of a single osteosynthesis plate. As a patient usually receivd several miniplates for bone fixture, he will be exposed to long anaesthesia.

In co-operation with the surgeons of the Clinic of Maxillofacial surgery at the University of Heidelberg we have conceived a planning system for the preoperative positioning of miniplates on a model of the patient's skull. The appropriate bending is computed and the bending data are stored for later use by a bending device and an intraoperative positioning aid. The principles of our computer-aided tool are presented in this paper.