Advanced bionics thin lateral and helix II electrodes: A temporal bone study

OBJECTIVE: This study was performed to evaluate the insertional properties of two cochlear implant electrodes recently developed by Advanced Bionics Corporation. STUDY DESIGN: Anatomic study using human cadaveric temporal bones. METHODS: The electrode prototypes we tested are the Thin Lateral and Helix II arrays, which incorporate features designed to minimize insertional trauma. A total of eight electrodes (4 of each prototype) were evaluated after insertion into freshly fixed temporal bones. The electrodes were inserted by way of standard cochleostomies, and the specimens were subsequently dissected to assess electrode position, insertion depth, and intracochlear trauma. RESULTS: Quantitative data regarding insertion depths and contact distances from the modiolus are presented for all electrodes tested. The mean insertion depths were 368° for the Thin Lateral electrodes, which are designed to approximate the lateral cochlear wall, and 436° for the Helix II electrodes, which occupy a more medial position in the scala tympani. No evidence of insertional trauma was observed with either electrode. The ease of insertion and absence of trauma were confirmed during additional trials in which electrode behavior was directly observed during insertion into previously opened cochleas. CONCLUSION: Both electrodes performed favorably in our human temporal bone trials, and both arrays appear promising for clinical use, especially in patients with residual hearing in whom atraumatic insertion is an important objective.