gms | German Medical Science

76th Annual Meeting of the German Society of Oto-Rhino-Laryngology, Head and Neck Surgery

German Society of Oto-Rhino-Laryngology, Head and Neck Surgery

04.05. - 08.05.2005, Erfurt

Application of a portable navigation system in head and neck surgery

Meeting Abstract

Deutsche Gesellschaft für Hals-Nasen-Ohren-Heilkunde, Kopf- und Hals-Chirurgie. 76. Jahresversammlung der Deutschen Gesellschaft für Hals-Nasen-Ohren-Heilkunde, Kopf- und Hals-Chirurgie e.V.. Erfurt, 04.-08.05.2005. Düsseldorf, Köln: German Medical Science; 2005. Doc05hno416

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Published: September 22, 2005

© 2005 Majdani et al.
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Navigation systems are often applied in head and neck surgery. In particular, the use of these intraoperative assistance systems is favoured in frequent operations at the frontal skull base because of a limited overview of the surgical site. Apart from prolonged preparation time at the beginning of each operation and financial costs, size and complexity of these systems often prevent the utilisation of navigation systems. Since the first systems were established at the beginning of the 90's, workflow was substantially simplified. Standard program parameters for skull base surgery and essential features have been defined in the past. Actually, manufacturers work on the miniaturisation of the navigation devices for a better integration into the clinical routine and for making this technology affordable.

We used the iNAV navigation system of the Medtronic® company in 15 cases of endonasal surgical procedures. All patients suffered from therapy-resistant chronic sinusitis. The electrooptically passive navigation system is realized as a laptop and a camera system, which is mounted onto a tripod to survey the surgical site. Download of CT imaging data can be performed via intranet or CD-ROM. Headsets or markers during the image acquisition are not necessary, registration is performed by skin surface matching. Approximately 150 to 200 points of the skin surface are acquired by a rigid pointer. For referencing both a headband and a skull-mounted reference star can be used. The iNAV is operated by use of a touch screen. Intraoperatively acquired screenshots can be stored and transferred on CD-ROM later on. The workflow of the system, the necessary installation time, the precision of navigation as well as the ease of integration into the clinical routine was evaluated.

The installation time, i.e. times for data downloading on the navigation computer, attachment of the reference adapter and registration, took between 5 and 11 minutes. The portable system can be placed on a table closed by the operation field. The graphic representation is optimized for endonasal surgery purposes. An integration of video pictures from endoscope or microscope is not implemented so far. The menu navigation is self-explanatory. After sterile positioning of the reference headband the use of the system does not require the help of assistance personnel. A straight suction is available. The estimation of navigation precision took place by means of anatomical landmarks (glabella, medial and lateral border of the orbit, head of the middle turbinate, ostium of the maxillary sinus and front and back plate of the sphenoidal sinus). We measured the inaccuracy of 1 to 2 mm. In order to shorten the installation time, we reduced the number of matching points for registration to 150 points in 7 patients. This did not lead to any noticeable decrease of the precision.

The handling of the portable system is intuitively to understand and realizable within only a few steps. Due to its compactness the system can be transferred easily into several operating theatres. The navigation accuracy meets the needs of frontal skull base surgery. For a better constancy of the navigation precision over the entire operation duration modifications of the headband will be preferable in order to avoid intraoperative shifts of the reference adapter. An integration of the microscope’s view has been favored by some surgeons.