First clinical application of a navigation-controlled shaver in paranasal sinus surgery

Conventional, pointer-based navigated Functional Endoscopic Sinus Surgery (FESS) has been shown to have certain limitations: necessity of instrument change for navigation, changes in the surgeon's line-of-sight axis, and limited length of use of the navigation information. These limitations result in negative consequences regarding the surgeon's attentiveness in any given situation, as well as in his cognitive work-load. The principle of Navigated Control offers advantages concerning these problems and limitations of the conventionally navigated FESS. This Chapter analyzes the first clinical deployment of a navigation-controlled shaver in FESS on the basis of the following questions: (1) Is clinical deployment of the navigation-controlled shaver possible with the pre-clinic evaluated set-up? (2) What information relevant to the surgery is relayed in an intraoperative setting by the navigation-controlled shaver? (3) How does deployment of the navigation-controlled shaver affect the ergonomics of the surgery? Ten patients with chronic sinusitis ethmoidalis were included in the study (average age: 48 [22-71], m:w=4:6). The preoperative and intraoperative workflow was documented according to the Innovation Center Computer Assisted Surgery (ICCAS) Workflow protocol. Data regarding the surgical validity of the information and ergonomic characteristics were recorded by means of questionnaires. The average time required for segmentation of the workspace was 14.2 minutes. The shaver switched off through Navigated Control an average 16.5 times during an FESS. From this amount, five shutdowns on average were initiative and six were determined to be provoked. The shutdowns were indicated by the operators to be correct in 199 of 220 (90.5%) events and in agreement with the actual position and planned resection borders. The quality of the relayed navigation information was indicated with an average Level of Quality (LOQ) of 56.4 [50-80]. The most favorable evaluation was attained for navigation in the area of the sphenoid sinus with 71 points on average [60-80]. During an FESS, the navigation information led to a change in the planned surgical strategy an average of 0.9 [0-3] times. Throughout all surgical procedures, the situation awareness was assessed an average of 2.7 points better than with the conventionally navigated FESS. This also was the case for the cognitive workload (Workload shift) with 2.8 [1-3.5] points. This Chapter proves the clinical applicability of a navigation-controlled instrument by means of a shaver in Ears, Nose, and Throat (ENT) surgery for the first time. Reproduction of the dental splint registration, manual segmentation of the working space, and attachment of the registration star still prove to be critical aspects. Data regarding quality of the information relayed by the navigation system and resulting change in surgical strategy lead to the conclusion that the authors are dealing with, in the overall evaluation, supplementary and surgically relevant information. This information is more efficiently transferred to the surgeon by means of Navigated Control that allows, according to the following results, both an improved understanding of the information and cognitive easing of stress for the surgeon.