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R. MARINO ET AL.

congenital aural atresia and conductive or mixed hearing loss, and their results found that fascia overlying the FMT and cartilage packing gave the best ECoG recordings. Rajan et al. (8) investigated the coupling efficiency in seven patients with mixed HL and one with conductive hearing loss. It was demonstrated that all patients had a significant improvement on speech in quiet and in noise scores postoperatively compared with preoperative out- comes. It was also found that coupling efficiency was higher with partial or complete direct contact of the FMT with the RWM and reduced when soft tissue coupling was used. This was one of the first studies that used ob- jective coupling efficiency measurements to demonstrate whether partial or full contact with the RW is essential and whether use of interposed fascia gave better coupling in the RW-FMT application. This study expands the work of Rajan et al. (8) by examining the coupling efficiency when the FMT has been in contact with the RW either directly or with fascial underlay or crimped to the stapes or the incus. Patients Ethics approval was obtained for this prospective study from the local ethics committee and was in accordance with the Helsinki Declaration. Sixteen patients (nine female, seven male) are involved to date. The average age at implantation was 56.3 years (range 19 Y 78). Nine patients presented with a conductive hearing loss, six had a mixed hearing loss, and one patient a sensorineural hearing loss. All subjects could not benefit from conventional hearing aids because of chronic otitis externa (Subjects 9, 12), chronic suppurative otitis media (Subjects 1, 3, 4, 5, 6, 7, 8, 10, 11, 13, 14, 16), severe to profound mixed hearing loss (Subject 2), and a non-healing external auditory canal resulting from carcinoma removal (Subject 15). The co- chlear (bone conduction hearing threshold) of all patients met the manufacturer’s specifications and all patients had speech perception results above 50% in the ear considered for im- plantation. All patients, except Subject 15 who had an open wound in the external auditory canal, trialed a behind-the-ear hearing aid before consideration for the VSB. All surgeries were conducted by an experienced middle ear and implantable device surgeon. See Table 1 for patient demographics and the surgical procedure employed. The mean hearing loss in the implanted ear using the four- frequency average of air conduction thresholds was 60.4 dB HL (SD = 24.3 dB) and the mean bone conduction threshold was 25.9 dB HL (SD = 10.1 dB). In the non-implanted ear, the mean air conduction four-frequency average was 40.7 dBHL (SD = 25.5 dB) and the bone conduction average was 23.0 dB HL (SD = 10.1 dB). Materials All patients received the Vibrant Soundbridge (Vibrant Med-EL, Innsbruck, Austria). Eight patients wore the 404 Audio processor and eight patients wore the Amade´ processor. Patients with bone conduction thresholds less than or equal to 25 dB in one frequency were fitted with the Amade´ Lo external processor and patients with worse bone conduction thresholds were fitted with the Amade´ Hi processor. MATERIALS AND METHODS

ongoing debate among the experts. Different variables such as the type of vibroplasty, the level of FMT-RW contact, and the use of soft tissue or titanium couplers all affect the efficiency and outcomes. It is unclear whether better results are achieved by placing the FMT in direct contact with the RW membrane or using an interposed material such as fascia or Tutoplast. It is also unknown whether stapes or incus vibroplasty is comparable to RW vibroplasty with regard to coupling and outcomes espe- cially in cases such as atresia or chronic ear disease where frequently both vibroplasty options can be implemented. This study aims to provide more insight into these aspects. RW vibroplasty poses surgical challenges that are as- sociated with the anatomy of the round window. There is a clear mismatch between the size of the round window membrane (RWM) with a mean diameter of 0.92 mm (6) and the size of the FMT with a diameter of 1.8 mm and a length of 2.3 mm. Furthermore, the shape of the RW niche and the actual location of the RW membrane present additional challenges. Frequently, the RW niche is funnel-shaped with the RWmembrane sitting at the deep narrow end away from the rim of the niche, thus making direct placement impossible, even with the available cou- plers. Pennings et al. (7) noted that the size of the RW niche and the angle and exposure of the RW membrane were highly variable in 10 cadaveric temporal bones. In addi- tion, many patients who would benefit from the RW ap- plication of the VSB have already undergone multiple middle ear surgeries making placement of the FMT chal- lenging due to fibrosis of the middle ear or fibrous oblit- eration of the RW niche. Rajan et al. (8) demonstrated that whereas the FMT needed to be in contact with the RW to attain good coupling efficiency, the degree of contact re- quired was not a factor in patient outcomes. Therefore, even in cases of partial contact, good hearing outcomes were attained for these subjects. This would potentially be in contrast to patients with a mixed hearing loss who rely on best possible coupling to maximize the amplifying gain and minimize loss of sound transfer energy caused by in- efficient FMT coupling. The role of couplers or soft tissue interposition is controversial. The literature is divided into cadaveric and in vivo patient studies. The latter is more pertinent for making clinical decisions given we are dealing with ‘‘living tissue’’ in which there are healing processes and scar tissue formation. There are human temporal bone studies that demon- strate the improved coupling efficiency of the use of in- terposed fascia between the FMT and the RWM (7,9 Y 11), and in addition, some clinicians recommend the addi- tional use of a cartilage or soft tissue cap behind the FMT to create some pretension on the FMT which improves the coupling to the RW membrane (7,9,10). Colletti et al. (12) recommend the use of interposed fascia with ECoG (electrocochleography) measurements guiding optimal placement of the FMT intraoperatively. Conversely, Skarzynski et al. (13) report better coupling with direct FMT to RW contact. Mandala et al. (14) examined positioning of the FMT in 14 children with

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