102 Chapter 4.1 a headband with postoperative results with an implantable bone conduction device. In the preop trial with the Headband they measured an improvement in hearing thresholds from 53±13.8 to 37.4±11.3 on average. Using this data an effect size (dz) of 1.3 is measured. Assuming a significance level (α) of 0.05 and a power of 80% for the same subject group a sample size of 6 subjects was calculated. To allow for possible dropouts (approximately 20%) and to provide additional safety and efficacy information, it is recommended that at least eight subjects should be included from a statistical point of view. To draw more powerful conclusions a sample size of 20 was chosen, above the statistically required number. 3. Results Twenty-four consecutive patients were initially enrolled in the study; three were subsequently excluded; two due to age being outside study criteria at the time of eventual fitting, and one due to the late detection of a mixed hearing loss. Twenty-one subjects with 22 devices completed the study: 20 patients had a unilateral CHL and 1 patient was bilateral. The gender distribution was very similar with 11 females and 10 males. The mean age was 9 ± 3 years. and the meantime using the adhesive system was 7 ± 2.4 years. Fourteen participants had congenital CHL and 7 acquired CHL (Table 1). Standard pure-tone audiometry was done during the first visit to confirm CHL. Mean air conductions PTA4(0.5-4kH.) thresholds of 57 dBHL ±11. Free field pure-tone audiometry using warble tones demonstrated an improvement in thresholds at all frequencies with both the softband aid and the adhesive retained BC aid as compared with unaided. The softband mean PTA 4 was found to be 30 dBHL ±6. The adhesive retained BC system at fitting demonstrated a PTA4 27 ± 6 and at the fourth week 26 ± 3 (Fig. 1). Figure 2 demonstrates the mean sound field thresholds over the frequency range of 500 Hz to 8 kHz in unaided and aided conditions that the first visit (VI) and after a minimum of 4 weeks of continued use (W4). As the graph demonstrated there is an improvement in thresholds above 1 kHz with adhesive retained BC system as compared to softband at both review points.
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