The role of stability measurements of the Baha® system in children

Percutaneous bone conduction hearing aids are an established treatment for selected children unable to use conventional hearing aids. Currently in children, loading the implant is delayed for 3-6 months following fixture placement, due to concerns regarding bone quality, bone thickness and subsequent implant stability. Traditionally, such concerns led to children undergoing 2-stage Baha(®) surgery, with a second operation to attach the abutment after 3-6 months. Bone conduction implant stability can be objectively measured using resonance-frequency analysis (RFA) to generate Implant Stability Quotients (ISQs). We aimed to assess implant stability in children undergoing 1-stage surgery using RFA measurements and investigate the possible implications for earlier loading following surgery.

We report a case series of consecutive children undergoing Baha(®) at our tertiary paediatric hospital. The interval to implant loading remained 3-6 months for the duration of this study. RFA measurements were taken peri-operatively, 1 week post-surgery, within 3 months of surgery and then subsequently at follow up appointments. RFA measurements were also measured at loading of the hearing processor and at follow up appointments after loading.

Nine children received 10 Cochlear™ Baha(®) BI300 implants (8 unilateral and 1 bilateral) with a mean age of 9 years 4 months (4 years 9 months to 13 years 5 months). The mean time to loading of the hearing processor was 3.3 months (3 to 5 months, n=9) and mean follow up was 9 months (12 weeks to 23 months). Eight children had ISQs that were potentially sufficient to have loaded the implant earlier than 3 months. Implant stability was maintained after loading with the hearing processor.

This study supports the potential use of RFA measurements to either, guide implant loading following 1-stage surgery in children, or to enable a larger prospective study of early loading (4-6 weeks) in children.