Bilateral active bone conduction implants: systematic review highlighting current evidence gaps

BACKGROUND: Active bone conduction implants (ABCI) are an emerging rehabilitation option for conductive / mixed hearing loss and single-sided deafness in patients unsuitable for conventional aids or middle-ear surgery. Bilateral use might confer binaural advantages, but evidence is limited. The objective of this paper was to systematically review the literature on bilateral implantation of active bone conduction devices, analyzing audiological outcomes, patient-reported benefits, and safety, and to identify evidence gaps.METHODS: Following PRISMA 2020 guidelines, a systematic review was conducted in PubMed, Embase, Scopus and Cochrane. Inclusion criteria were bilateral (simultaneous/sequential) ABCI with extractable outcomes. After screening, extracted data encompassed PTA, speech in quiet/noise, patient-reported outcomes, follow-up, complications. Quality was assessed via ROBINS-I and Joanna Briggs checklists. Heterogeneity precluded meta-analysis, so narrative synthesis (SWiM) was adopted.RESULTS: Seventeen studies covering 112 patients were included. Mean age at implantation: 27.6 years; 84 patients received simultaneous implants. The main indication was congenital bilateral aural atresia/microtia (N.=89). Ten studies evaluated Bonebridge implant, seven Osia implant. Bilateral fitting generally improved audiological outcomes over unilateral use, especially speech-in-noise (mean SNR gain 3-5 dB). Postoperative WRS ranged 80-98%, functional gain 35-47 dB HL. Patient-reported outcomes indicated enhanced spatial hearing and listening comfort. Complications were rare (seroma, magnet-site irritation).CONCLUSIONS: Bilateral active bone conduction implantation is technically feasible and safe, with consistent functional and subjective improvement. However, evidence is limited by observational design and heterogeneity. Prospective, standardized studies are needed to confirm clinical binaural benefit.