INTRAOPERATIVE GUIDANCE IN MAXILLOFACIAL AND CRANIOFACIAL SURGERY

The authors' experiences with intraoperative computer assisted guidanc e in interventions in oromaxillofacial and craniofacial surgery are re ported. The guidance system SPOCS(R) (Surgical Planning and Orientatio n Computer Systems, Aesculap, Germany) consists of an infrared light e mitting system of diodes and camera, an imaging workstation and assort ed freehand instruments. The software is an updated version of the wel l-known Viewing Wand(R) software (ISG Technologies, Canada). In tests on phantoms, the system proved a mean accuracy of less than 1.5 mm. Wi thin the last 15 clinical tests, the system has achieved an accuracy b etter than 3 mm which, at the moment, the authors estimate to be suffi cient to proceed with its clinical evaluation. Using bone screws to re gister the patient's position, an accuracy in the range of less than 2 mm in relation to bony reference points has been achieved. By visuali zing the tip of the instrument in real time, this technique allows sur gical interventions, even in anatomically complicated situations, with out endangering vital neighbouring structures. The 'offset' function o f the software, by which the surgeon can elongate the tip of the instr ument virtually, allows the surgeon to analyse structures before they are penetrated by the instrument as in a 'look ahead' operation. The a uthors expect computer assisted simulation and guidance systems to imp rove surgical quality and reduce the risks associated with surgical in terventions.