Utility of a freehand frameless navigation system in computed tomography-assisted ventral bulla osteotomy for otitis media in calves

Ventral bulla osteotomy has not been widely adopted for treating otitis media in calves due to its prolonged surgical duration (>1 h), high surgical invasiveness, and challenges in application for bilateral cases. This study aimed to evaluate the utility of a freehand frameless navigation system for computed tomography-assisted ventral bulla osteotomy in 21 calves diagnosed with otitis media. Preparation times-including computed tomography examination and registration procedures-varied between 18 and 73 min. This technique allows for a minimal skin incision, approximately 1 cm in length, allowing instrument access via a 7-mm-diameter trocar. Surgical times for the 36 affected ears across 21 animals ranged between 7 and 26 min per ear. This technique reduced total procedure time, including preparation and surgical times. The median durations were 49.0 min (range, 41-57 min) for unilateral cases and 66.0 min (range, 47-106 min) for bilateral cases. In 13 of the 21 treated animals, otitis media-associated clinical signs improved or disappeared suddenly or gradually after surgery. Postoperative complications included generalized convulsive seizures and swollen mandibles in one and three animals, respectively. Areas for improvement warranting further development include: (1) prevention of unexpected complications and reduction of time-consuming preparation steps contributing to prolonged preparation time, (2) method for securing the calf's head on a surgical table, and (3) technical transfer from manual operation to utilization of an electric drill device to create a perforation om the affected tympanic bulla.