The Impact of Location and Device Coupling on the Performance of the Osia System Actuator

Abstract

Active transcutaneous bone conduction (BC) devices offer the benefit of improved power output compared to passive transcutaneous devices and remove the risk of skin infections that are more common in traditional percutaneous BC devices. Despite these advantages, more research is needed on implant location, device coupling, and their influence on device performance. This study is aimed at quantifying the extent to which certain parameters affect device output when using the Osia® system actuator. Parameters under study are (1) implant location, (2) comparison with the actuator of a state-of-the-art BC device, (3) bone undergrowth simulation, and (4) skull fixation. Five human cadaveric heads were implanted with the actuator at three different implant locations: (1) recommended, (2) posterior Osia® positions, and (3) standard Baha® position. At each location, the cochlear promontory velocity and the intracochlear pressure difference were measured. A percutaneous bone conduction actuator was used as a reference for the obtained measurements. Stimulation levels corresponded to a hearing level of 60 dB HL for frequencies between 250 and 6000 Hz. In addition, bone cement was used as a simulation for reactive bone growth. Results obtained in four heads indicate an improved power transmission of the transcutaneous actuator when implanted at the recommended position compared to the actuator of the percutaneous device on its respective recommended location when stimulating at an identical force level. A correlation was found between the promontory vibration and the actuator position, indicating that the same level of stimulation leads to higher promontory vibrations when the device is implanted closer to the ear canal. This is mainly reflected at frequencies higher than 1 kHz, where an increase was observed in both measurement modalities. At lower frequencies (<1 kHz), the power transmission is less influenced by the implant position and differences between the acquired responses are limited. In addition, when no rigid coupling to the skull is provided, power transfer losses of up to 30 dB can be expected.

Objective preclinical measures for bone conduction implants

“…The measurements of intracochlear pressure normalized to ear canal pressure for air conduction and promontory velocity for bone conduction align with the ranges reported in the literature (Nakajima et al, 2009;Grossöhmichen et al, 2016;Greene et al, 2017;Stieger et al, 2018;Mattingly et al, 2020;Fierens et al, 2022;Putzeys et al, 2022). This alignment validates the intracochlear measurement technique employed in this study.…”

“…The measurement of promontory velocity consistently identifies the standard Osia position as generating the highest amplitude. It is therefore the most efficient stimulation position according to this measure, which aligns with the findings of Fierens et al (2022). This consistent observation provides further evidence for the precision of this measurement technique (Rosowski et al, 2007;Koch et al, 2022).…”

“…At the same time, Figure 2D also shows the differential pressure during bone conduction stimulation normalized to the promontory velocity for specimen 1L, while Supplementary Figure S4 shows the same pressure for all specimens. Both figures also show the ranges of similar measurements published in the literature (Nakajima et al, 2009;Grossöhmichen et al, 2016;Stieger et al, 2018;Mattingly et al, 2020;Fierens et al, 2022;Putzeys et al, 2022).…”

“…Four fresh-frozen human cadaveric specimens were provided by the Vesalius Institute (Anatomy and Pathology, University of Leuven - KU Leuven, Belgium) following the ethical approval of the same institute (S65502) and following the Helsinki declaration. Similar procedures regarding harvesting and preparation of specimens were used in our previous studies ( Borgers et al, 2019 ; Fierens et al, 2022 ; Putzeys et al, 2022 ) and inspired by previous intracochlear pressure measurements ( Nakajima et al, 2009 ; Greene et al, 2015 ; Grossöhmichen et al, 2016 ; Stieger et al, 2018 ; Mattingly et al, 2020 ).…”

“…In contrast with live patients who can provide subjective feedback to evaluate the hearing sensation, tests in cadaveric specimens require objective measures. Currently, three measures are commonly employed: intracochlear pressure ( Greene et al, 2015 ; Borgers et al, 2019 ; Mattingly et al, 2020 ; Fierens et al, 2022 ; Putzeys et al, 2022 ), promontory velocity ( Stenfelt and Goode, 2005 ; Rosowski et al, 2007 ; Dobrev et al, 2016 , 2020 , 2023 ; Roosli et al, 2016 ; Rigato et al, 2019 ; Ghoncheh et al, 2021 ; Prodanovic and Stenfelt, 2021 ), and ear canal pressure ( Mertens et al, 2014 ; Nie et al, 2022 ).…”