[Computer assisted methods in reconstructive and function-preserving orbital surgery. New capabilities of computer assisted preoperative surgical planning (CAPP) and computer assisted surgery (CAS)].

BACKGROUND: Orbital reconstruction after tumor or trauma makes high demands on the surgeon when restoring the optic axis and cosmetic features. Computer-assisted preoperative planning surgery (CAPP) and computer-assisted surgery (CAS) allow calculation of the form of the orbital cavity to be reconstructed preoperatively as well as the process of its realization intraoperatively. METHODS: We developed new planning software methods for this surgical procedure. For validation the deviation of accuracy was assessed between the virtual and the real model in eight patients with surgical reconstruction of the orbit. RESULTS: The check of accuracy of the reconstructions compared to the planning of the surgery by fusion of preoperative and postoperative data resulted in a mean deviation of 1.74 mm. The volumetric measurements presented a mean deviation of 0.2 cm(3) with an accuracy of >99%. The accuracy of linear measurements with the techniques of image fusion of the "feature-based" method was 0.38 mm and thus close to the technical threshold of effective data accuracy of 0.35 mm. The enophthalmus could be assessed more objectively with this method compared to using the Hertel index. CONCLUSIONS: CAPP and CAS are helpful in reconstructive orbital surgery to verify the position of the optic axis and the cosmetic result intraoperatively.