Three-Dimensional Displacement of the Endoscope

Abstract

Endoscopic ear surgery (EES) has, in recent years, become more widely adopted by ear surgeons. Important benefits of an endoscope over a microscope include the wide field of view of the middle ear afforded by the light source located at the tip of the instrument and the availability of angled lenses. Furthermore, middle ear procedures using an endoscope can reduce the need for drilling in the operative field [1]. During EES, the operator holds the endoscope with one hand and manipulates the instruments with the other. However, maintaining endoscope stability can be difficult, particularly for operators with insufficient experience in endoscopic surgeries. Such instability of the endoscope can cause surgical difficulties, and increase the risk of complications resulting from contact with important surrounding structures. In other fields where access to the surgical field is relatively wide, an assistant surgeon often holds the endoscope with both hands to maintain a good view. In contrast, using an assistant to keep the endoscope stable in EES is very difficult, because the endoscope and instruments pass through the same hole, the external auditory canal (EAC). As the intraoperative monitor only provides a 2-dimensional image, the operator cannot judge how far the endoscope is displaced parallel to the visual axis. Few reports have examined the impact of hand tremor during surgery, and none appear to have investigated endoscope displacement during EES. This study established a method to measure 3-dimensional displacement of the endoscope in an objective manner and then measured endoscope displacement under different conditions of endoscope fixation to analyze appropriate fixation during EES.