Mechatronical Assistance in Temporal Bone and Lateral Skull Base Surgery with Navigated Control

Introduction: High-resolution CT of the temporal bone is the basis of a 3D representation of the risk structures and preoperative planning stage of surgery. A drill can be registered in the region of interest by 3D camera systems. The force of the drill can be regulated on the basis of this preoperative planning. The goal of this study was the investigation of the feasibility and the minimum accuracy of the overall system. Material and Methods: In our study, 1.0 mm CTs of the temporal bone were visualized in 3D. Risk structures (facial nerve, sigmoid sinus, lateral canal, and middle fossa dura) were defined as safety regions. The regulation of the drill was realized following the intraoperative registration of the 3D camera system. In the cadaver experiment the measurements took place for the efficiency of segmenting, the accuracy of the registration of the overall system, and the intraoperative conversion of planning at a total of five preparations. Results: Segmentation of the examined risk structures succeeds both manually and semiautomatically with a satisfying clinical result. The expenditure of time is from 14 to 68 minutes per case. The registration accuracy of the instrument was found to average 1.3 mm with a maximum deviation of 4.2 mm. Under definition of a safety passage of 3 mm in the altogether represented 3250 mm2 in two cases a microscopic representable injuries of the Safety Regions on a surface of altogether 21 mm of was founded. The postoperational CT evaluation resulted in an effectiveness of the bone erosion of 89%. Conclusions: The principle Navigated Control© permits control of the drill in surgery of the temporal bone. The (thus far) insufficient accuracy of the registration of the instrument is compensated for by a high safety passage. This problem should be solved, however, with technical modifications in the next development steps. The outstanding advantage of the represented principle is that a support of the surgeon can take place intraoperatively without substantial changes of the set-up.