BONEBRIDGE bone conduction implant via middle fossa approach in patients with conductive or mixed hearing loss

BackgroundThe BONEBRIDGE bone conduction implant (BB-BCI) (MED-EL GmbH, Innsbruck, Austria) is an active transcutaneous system indicated for patients with conductive or mixed hearing loss, or single-sided deafness. It was first launched in 2012 as the BCI 601, with a second-generation implant (BCI 602) released in 2019. The BCI 602 features a thinner implantable portion, which expanded selection criteria to include patients who previously could not receive the implant. The middle fossa surgical approach offers a viable alternative for patients with mastoid anatomy which precludes implantation in the traditional transmastoid position, including patients with sclerotic mastoids, mastoid cavities, and histories of recurrent mastoiditis.MethodsAn institutional review was conducted of patients who underwent unilateral BB-BCI implantation with either implant generation via the middle fossa approach between April 2013 and March 2025. Preoperative air conduction (AC) and bone conduction (BC) pure-tone averages (PTAs) measured at 0.5–3.0 kHz, postoperative aided thresholds, and speech perception scores (CNC words and AzBio sentences) at an average of 6.5 months post-implantation were recorded. Surgical outcomes and complications were also reviewed.ResultsSeventy-two patients were included in the review (30 male, 42 female; mean age at implantation 43.9 years; 48 with conductive hearing loss, 24 with mixed hearing loss; 39 implanted on the right side). For the BCI 601 group (n =44), AC and BC PTAs were 64.3 ± 14.7 dB (mean ± standard deviation) and 24.1 ± 12.6 dB, respectively; for the BCI 602 group (n = 28), they were 64.5 ± 14.8 dB and 23.4 ± 13.2 dB, respectively. The mean ABG was 41.1 dB across the cohort. Mean functional gain was 38.7 ± 15.0 dB, with no significant difference between groups (601: 38.5 ± 15.0 dB; 602: 39.1 ± 15.2 dB; p = 0.85). Speech perception improved for all patients postoperatively. No intraoperative complications or revision surgeries were reported.ConclusionThe middle fossa approach for BONEBRIDGE implantation demonstrates favorable audiological benefit and an excellent safety profile. This study reports on a 12-year institutional experience using the middle fossa technique, comparing audiological and surgical outcomes between the first- and second-generation implants. No statistically significant difference was observed between device generations, supporting the ongoing use of this technique for appropriately selected patients.