Intraoperative monitoring of active middle ear implant function in patients with normal and pathologic middle ears.

OBJECTIVE: To describe a technique enabling the intraoperative assessment of the mechanical coupling of active middle ear implants in patients with normal or dysfunctional middle ears. PATIENTS: Patients with sensorineural or mixed hearing loss subjected to revision surgery of an active middle ear implant. INTERVENTION: Recording of compound action potentials (CAPs) of the auditory nerve in response to stimulation via an active middle ear implant during revision surgery. MAIN OUTCOME MEASURES: CAP thresholds as a measure of mechanical coupling and system integrity. CONCLUSION: Determining CAP thresholds may be suitable for identifying a proper mechanical coupling of active middle ear implants in patients with a dysfunctional middle ear, even if the ossicular chain is disrupted.

Virtual reality: a new paranasal sinus surgery simulator.

OBJECTIVES/HYPOTHESIS: Virtual surgical training systems are of growing value. Current prototypes for endonasal sinus surgery simulation are very expensive or lack running stability. No reliable system is available to a notable number of users yet. The purpose of this work was to develop a dependable simulator running on standard PC hardware including a detailed anatomic model, realistic tools and handling, stereoscopic view, and force feedback. STUDY DESIGN: Descriptive. METHODS: A three-dimensional voxel model was created based on a high-resolution computed tomography study of a human skull, from which the bony structures were segmented. The mucosa and organs at risk were added manually. The model may be manipulated with virtual surgical tools controlled with a low-cost haptic device, which is also used to adjust microscopic or endoscopic views. Visualization, haptic rendering, and tissue removal are represented with subvoxel resolution. RESULTS: The handling of the model is convincing. The haptic device provides a realistic feeling regarding the interaction between tool tip and anatomy. Three-dimensional orientation and the look and feel of virtual surgical interventions get close to reality. CONCLUSIONS: The newly developed system is a stable, fully operational simulator for sinus surgery based on standard PC hardware. Besides the limitations of a low-cost haptic device, the presented system is highly realistic regarding anatomy, visualization, manipulation, and the appearance of the tools. It is mainly intended for gaining surgical anatomy knowledge and for training navigation in a complex anatomical environment. Learning effects, including motor skills, have yet to be quantified.