Hearing preservation in cochlear implantation: a comprehensive review with emphasis on atraumatic and robot-assisted electrode insertion

Background Preservation of residual hearing has become a central objective in modern cochlear implantation (CI), enabling electro-acoustic stimulation and improved speech, music, and noise perception. Achieving this goal depends critically on minimizing intracochlear trauma during electrode insertion. Despite atraumatic surgical techniques, a substantial proportion of recipients lose part or all of their residual hearing over time, and manual insertion remains constrained by human motor variability. Purpose This review synthesizes current evidence on the mechanisms of insertion-related cochlear trauma and evaluates surgical, pharmacological and technological strategies for hearing preservation, with particular attention to the role of robot-assisted cochlear implantation surgery (RACIS). Methods A narrative synthesis of experimental, histopathological, and clinical literature addressing atraumatic electrode insertion principles, electrode design, insertion kinematics, perioperative corticosteroids, and robotic insertion systems (including RobOtol, OTODRIVE, and iotaSOFT). PubMed/MEDLINE, Embase and Web of Science were searched from January 1980 to May 2026, with Google Scholar and the reference lists of key articles as supplementary sources. Preclinical data are reported separately from clinical data. Results Insertion-related trauma, including scalar translocation, electrode tip fold-over, and basilar membrane rupture, triggers inflammation, fibrosis, and neo-osteogenesis, compromising both residual hearing and long-term neural survival. Insertion speed and trajectory stability are identified as key modulators of intracochlear force and pressure generation. In cadaveric and in vitro models, robotic systems achieve significantly lower and more reproducible insertion angular errors and force profiles than manual insertion, with higher rates of full scala tympani placement and lower trauma scores. Clinical studies suggest improved hearing preservation (up to 85% vs. 71% following manual insertion in a non-randomized comparative study). Meta-analytic data report an overall RACIS procedural success rate of 97.2% and a complication profile comparable to conventional surgery. Postoperative impedance trends are also more stable, suggesting attenuated fibro-inflammatory remodeling. Pooled hearing preservation estimates, however, show very high statistical heterogeneity (I2 = 98.41%). Conclusions RACIS represents a maturing, reproducible approach to atraumatic cochlear implantation that reduces inter-operator variability and improves the consistency of electrode placement. Integration with real-time intraoperative monitoring, such as electrocochleography, offers further potential for adaptive, personalized insertion strategies. At present, the technical superiority of robotic insertion is better established than its long-term functional benefit. Future randomized controlled studies incorporating long-term functional outcomes, cost-effectiveness and anatomical imaging are required to establish the true clinical benefit of RACIS.