Electrode-Modiolar Distance as a Determinant of Cochlear Implant Performance: A Systematic Review and Meta-Analysis

To quantify the relationship between electrode-modiolar distance (EMD) and cochlear implant (CI) performance across speech/perceptual, electrophysiological and programming outcomes and to characterize the dose-response effect of EMD.

A systematic search of PubMed/MEDLINE, Embase, Scopus, Web of Science and Cochrane CENTRAL was conducted in accordance with PRISMA guidelines. Human studies reporting CT- or CBCT-derived EMD and CI outcomes were included. Effect sizes were transformed to odds ratios (ORs) and pooled using random-effects models. Subgroup, sensitivity and dose-response analyses were performed. Heterogeneity was assessed using I², and publication bias was evaluated using funnel plots and Egger's test.

Twenty-one studies comprising approximately 1181 implanted ears were included. Reduced EMD was associated with significantly higher odds of favourable CI outcomes (pooled OR = 2.16, 95% CI: 1.89-2.45; p < 0.001; I² = 0%). Consistent effects were observed for speech/perceptual outcomes (OR = 2.23), electrophysiological measures (OR = 2.80 after sensitivity adjustment) and programming parameters (OR = 1.72). Dose-response modelling demonstrated a monotonic gradient, with each 1 mm increase in EMD associated with a 20%-30% reduction in the odds of favourable outcomes (OR per mm ≈0.72; p < 0.001). No significant publication bias was detected (Egger's p = 0.056).

Electrode-modiolar proximity is a strong and consistent determinant of CI performance with a clear dose-response relationship, supporting its role as a clinically actionable imaging biomarker for optimizing electrode selection, surgical strategy and individualized programming.

PROSPERO: CRD420261380236.