A functional and anatomical comparison between two passive transcutaneous bone conduction implants in children

Abstract

Objective

To compare anatomical and functional outcomes of two passive transcutaneous bone conduction implant systems: Sophono™ and BAHA Attract™.

Materials and methods

Twenty patients, affected by bilateral conductive hearing loss, underwent unilateral transcutaneous bone conduction implant surgery. Ten children received a Sophono™ implant (6 males, 4 females, mean age 11 years, mean unaided Pure Tone Average (PTA) 0.25-4kHz = 69.70dB HL) and 10 a BAHA Attract™ system (7 males, 3 females, mean age 19 years, mean unaided PTA0.25-4kHz = 66.40dB HL). The following outcomes were considered: incidence of local complications, hearing aid benefit, hearing aid gain and changes in quality of life (QOL), as measured by the Glasgow Children's Benefit Inventory (GCBI).

Results

One patient in the Sophono group experienced magnet-related skin decubitus, while two patients (one per group) had skin hyperemia in the area overlying the magnet. The mean BAHA-aided threshold was 23.70dB, whereas the mean Sophono-aided threshold was 31.60dB. The mean gain was significantly different for lower frequencies, the BAHA having better functional outcomes. All patients reported an improvement in their QOL.

Conclusion

Given the lower thickness of the internal magnet, the Sophono™ system might be more suitable for younger children, whereas BAHA offered better functional results. Both systems can be considered valid and safe options for the functional rehabilitation of conductive hearing loss in children, provided that precautions are observed, such as a gradual use of the device and use of the least powerful magnets in the first months after the activation.

Introduction

Bone conduction implants successfully rehabilitate good quality hearing for people suffering from conductive hearing loss that cannot be either corrected by otomicrosurgery or are not suitable for aiding with conventional air-conduction hearing aids. They provide a direct activation of the cochlea through vibration of the skull. Initially, bone conduction hearing aids are put on a vibrating transducer on a headband, glasses or an elastic arch. After a satisfactory trial period, a titanium screw is implanted on the skull as part of a semi-implantable bone-conduction hearing device, based on the osseointegration concept of Branemark and Harders [1,2]. These first percutaneous bone-anchored hearing solutions provided an uninterrupted coupling of the external and the implanted component, thus allowing an optimal hearing gain for both adult and pediatric subjects [3,4]. However, the high rate of soft tissue complications (local infection or skin overgrowth), the poor cosmetic outcomes, loss or failure of the implant, together with the need for a complete osseointegration of the fixture before loading, have been a strong drive for the development of transcutaneous bone conduction devices. Transcutaneous systems send vibrations to the skull via a “passive” implant which is driven by an external mechanical transducer, however, unlike percutaneous solutions, they are abutment-free, thus stimulating bone vibration through an intact skin due to the magnetic coupling between the external and implantable components. In turn, this allows a better cosmetic result and elimination of the risk of local infection and extrusion, while maintaining good functional gain [[5], [6], [7]]. In 2013, Siegert reported the first series of 20 patients with the Sophono, a transcutaneous bone conduction implant, which uses dual magnets implanted snugly onto the bone with five screws [8]. Shortly after, the BAHA Attract was released, which transmits sound through the same single osseointegrated titanium screw used in their percutaneous device. Both these devices provide a transcutaneous bone-anchored solution, and they are suitable for bilateral conductive hearing loss, bilateral mixed hearing loss with bone-conduction Pure Tone Average (PTA) _{0.5–4 kHz} ≤ 45 dB-HL (up to 55 dB-HL if appropriate sound processor is used) and single-sided sensorineural deafness. Such implants have been approved by the US Food and Drug Administration for use in children aged 5 years and older. To date, there is a lack of reports comparing the anatomical and functional outcomes of the Sophono and BAHA Attract passive transcutaneous bone conduction implants in a sizable pediatric cohort. Powell et al. [9] published their results in a study that compared outcomes between 6 patients with BAHA Attract and 6 that were implanted with the Sophono Alpha 1. They concluded that both systems improved audiological outcomes and there was no statistically significant difference in aided thresholds or speech discrimination scores between the two devices.

The aim of the present study is to compare the audiological, clinical, and Quality of Life (QOL) outcomes of the two types of passive transcutaneous bone conduction implants in pediatric patients: the Sophono Alpha (Sophono Inc., Boulder, CO, U.S.A.) and the Cochlear BAHA Attract (Cochlear Bone-Anchored Solutions AB, Mölnlycke, Sweden).