Minimizing Insertion Trauma with a Novel Shape Memory Polymer Cochlear Implant Array

HYPOTHESIS: Novel self-coiling electrode arrays made of shape memory polymer allow for atraumatic implantation of cochlear implants, minimizing loss of residual hearing and maximizing hearing outcomes for cochlear implant patients. BACKGROUND: Cochlear implants are effective devices in improving the hearing experiences of patients with severe to profound hearing loss. However, current cochlear implants are linear and collide with cochlear walls upon implantation into the cochlear spiral. This traumatic contact results in destruction of inner ear structures and a subsequent inflammatory response, leading to loss of residual hearing and submaximal patient outcomes post-implantation. Shape memory polymers (SMP), which can store a metastable shape and return to it in response to a stimulus, can be customized to fit perfectly into a patient's cochlea. Thus, an SMP cochlear implant electrode array can be straight and stiff enough to facilitate implant manufacturing, yet soften upon warming to body temperature and self-navigate through the cochlear spiral without contacting cochlear walls for totally atraumatic implantation. RESULTS: We have created a novel shape memory polymer cochlear implant electrode array that self-navigates through the cochlear spirals to allow for full and completely atraumatic insertion. We have also constructed a robotic linear actuator to provide consistent and controllable insertion of our SMP implants. Histological studies performed on implanted rat cochlea show lack of trauma to inner ear structures in cochlea implanted with SMP implants, indicating the superiority of our SMP implants over more traumatic conventional linear implants. CONCLUSIONS: We have demonstrated that shape memory polymers can be used in a novel way to make self-coiling cochlear implants that offer full yet atraumatic insertion, minimizing the adverse side effects usually experienced with implantation of more traumatic conventional linear implants.