[Computer-assisted video-endoscopic endonasal surgery].

UNLABELLED

To make the surgical procedure safer and more precise in FESS, a non-invasive markerless computer-assisted system (CAS) is described for intra-operative navigation whenever the critical regions may be affected by surgical manipulation.

PATIENTS AND METHODS

Twenty patients with benign diseases of the paranasal sinuses were treated by Computer Assisted Video-endoscopic surgery, between December 1997 and March 1998. For the determination of accuracy and reproducibility of the system, ten anatomical landmarks on each side of the paranasal sinuses were chosen and measured. All of these points were identified on the direct live video-endoscopy image and compared to those obtained with the Optical Digitizing System (Flashpoint 5000(R)), on axial, coronal and sagittal view. The Optical Localizer we used detects the position of the relative coordinates of two rigid bodies made of IR-LED's each, one rigid body is secured to the head' of the patient with a headset, so that patient motion can be tracked, and the second rigid body attached to the operating instrument, leading to direct localization of the tip of the instrument. We use a markerless, skin surface-based registration method, which has the advantage to avoid doing a second CT scan examination usually performed to process the position of the fiducial markers. We register the data from the patient's usual paranasal CT scan.

RESULTS

Computer-assisted surgery does not increase significantly the duration of the operation. Our markerless skin surface points registration method is reliable enabling of the movements patient's head during the procedure. Computer assistance can be used in almost any type of endoscopic sinonasal procedure. We obtained a registration and calibration accuracy of less than 1.5 mm in 89.2% of cases.

CONCLUSION

CAS enables the surgeon to have a more thorough understanding of the complicated anatomy of paranasal sinuses, and may be especially helpful in revision surgery when normal anatomic landmarks are lacking. Due to the passive optical technology (Passive Polaris(R)), we are continuing clinical studies in ENT surgery in order do improve the system and to simplify its current management.