Percutaneous Versus Transcutaneous Bone Conduction Implant System

Abstract

Present results support the proposal that a BCI system can be a realistic alternative to a BAHA.

A novel bone conduction implant (BCI): Engineering aspects and pre-clinical studies

“…Moreover, evidence is mounting that, even for the percutaneous BAHA, there is an increased need for more power, not less. However, it has been shown in earlier studies on a dry skull and on cadaver heads that the sensitivity to bone conducted sound would increase if the excitation point approaches cochlea (Stenfelt et al, 2000;Stenfelt et al, 2005;Håkansson et al, 2008;Eeg-Olofsson et al, 2008). This phenomenon seems to be related to the fact that the excitation point moves from the thinner parietal region of the skull bone to the interior portion of the temporal bone and closer to the cochlea.…”

“…When comparing the promontory acceleration levels measured by a laser Doppler vibrometer (LDV) through the ear canal it was found that this first version of the BCI had a similar or even higher Maximum Power Output (MPO) as compared to a Classic Baha ® . This was a positive and partly unexpected result, as previous dry skull measurements had In the paper by Håkansson et al 2008 it was also discussed how the implanted transducer could be installed with a safe and minimally invasive surgery. Obviously, the screw attachment and coupling used in that study on the cadaver head should not be used in live human skulls for several reasons: (1) to drill and install a screw interiorly from a bottom plane in a recess in the lateral portion of the temporal bone is associated with a high risk for facial nerve or vestibular damage, (2) the spongeous quality of the bone might not give a stable and firm attachment, (3) the screw length and snap coupling creates an extra height of 8-10 mm that should be added to the height of the transducer casing resulting in a total distance of 16-20 mm into the temporal bone and (4) would most likely need a two stage surgical procedure.…”

“…Another solution would be to move the transducer to an epicranial position using screw fixation on the side of the transducer casing as suggested by Ball et al, 2007 andWesterkull, 2007. This was not considered as a desired solution as the sensitivity increase by exciting over or interiorly of the temporal bone as shown by Eeg-Olofsson et al (2008) and Håkansson et al (2008) is then reduced and there might also, as mentioned above, be cosmetic-, skin-and feedback problems associated with an epicranial (protruding) casing.…”

“…A new transducer type has been developed for this implantable application which is called the Balanced Electromagnetic Separation Transducer (BEST) which has been described by Håkansson (2003). The topology of the implanted circuits including the transducer is completely passive but has been found to have sufficient power efficiency for ordinary BAHA patients in a feasibility study by Håkansson et al (2008). The demodulator unit is preferably placed inside the transducer casing.…”

“…To verify the C-BEST frequency response function, it was measured using the Skullsimulator (Håkansson, 1989) and compared with the previous naked BEST (used by Håkansson et al, 2008), Baha ® Classic and Intenso transducers (Cochlear Bone Anchored Solutions AB, Göteborg, Sweden), see Figure 5. The C-BEST casing was pressed statically by some 4-5 Newton against the Skullsimulator attachment by use of a special adapter.…”