Characterization of patient head motion in otologic surgery: Implications for TEES

Purpose: Middle ear disease is increasingly being managed via transcanal endoscopic ear surgery (TEES). A limitation of TEES is that it restricts the surgeon to single-handed dissection. One solution to this would be an endoscope holder to facilitate two-handed dissection. Current endoscope holders are stationary, and can cause potential damage from endoscope contact with the ossicles or ear canal if unintended head motion occurs from inadequate anesthetic. A dynamic device that could detect and react to patient motion would mitigate these concerns, but currently there is little formal characterization of the frequency, velocity and acceleration of unintended patient head motion during otologic procedures performed under general anesthesia. The present study aims to characterize intraoperative patient head motion kinematics during cases utilizing TEES. Materials and methods: This is a prospective study of adults undergoing otologic procedures performed with general anesthesia and without paralysis. Head motion was characterized using a nine-axis inertial measurement unit (IMU), (LPMS-B2, Life Performance Research) mounted to each patient's forehead for the procedure duration. Results: Data was collected across 10 cases; 50% of patients were female and mean age was 50 +/- 14 years. There was observed patient head motion in 40% of cases with maximum linear acceleration of 0.75 m/s(2) and angular velocity of 12.50 degrees/s. Conclusions: Patient movement during otologic procedures was commonly observed, demonstrating the need for a dynamic holder to allow two-handed TEES. Results from this study are the first objective characterization of patient head motion kinematics during otologic procedures performed under general anesthesia.