Table
3 depicts the study design as well as outcome measures and outcomes per study. Baker et al. (2015) [
23], in their study performed pre-operative audiometry using inset of supra-aural headphones and compared with soundfield post-operatively. Masking was applied to the non-test ear. In average PTA thresholds were improved by 41 dBHL and speech reception thresholds by 56 dBHL. However, measuring hearing thresholds by different means (inset or supra aural headphones vs. soundfield) can affect accuracy of statistical analysis. Post-implantation audiometric data were missing from one child as the magnet was not strong enough to hold the sound processor. Gawecki et al. (2016) [
19] reported on their series of 20 adult patients who underwent BAHA Attract implantation. They divided their patients in two groups, namely Group A: 11 patients with bilateral mixed or CHL and Group B: nine patients with unilateral deafness. The postoperative audiometric evaluation that was performed in 17 (85 %) patients, included speech in noise only and revealed a mean gain of 32.9 %. Iseri et al. (2015) [
9] presented the results of a multi-centre study that aimed to compare BAHA Attract with percutaneous bone conduction implants. The BAHA Attract group consisted of 16 patients. Some preliminary results on 12 of them were already published in 2014 [
24]. During surgery, bone polishing was required in 5 patients and soft tissue reduction in 4 patients. Post-operatively, the hearing thresholds and SRT were significantly improved (P < 0.05) when the bone conduction implant was on than without it. A between group comparison revealed a significant difference in the SRT results in favour of the percutaneous BCI group. Marsella et al. (2015) [
25] reported on their experience of 3 patients implanted with BAHA Attract. The mean gain on PTA was 25 dB. A better gain was seen in the central frequencies and lower gain in the lower (250Hz) and higher frequencies (4 kHz). The SRT post-operatively was 100 % for each patient, with a mean gain of 63 %. Clamp and Briggs (2015) [
2] presented some initial results from 8 patients implanted in Melbourne, Australia. This was part of a multicenter study; the other centres were in Santiago, Chile; Haifa, Israel and Hong Kong, China. A subsequent study was published later in 2015 [
22] that included another 19 patients. Free field hearing testing showed a mean gain of 18.4 dB HL over the 4 central frequencies. Mean improvement in SRT in quiet was 50 % at 50 dB SPL, 46.4 % at 65 dB SPL and 24.2 % at 80 dB SPL. There was statistically significant improvement in Speech in noise Ratio of 15 dB (SD: 12.8 dB) compared to unaided hearing and 3.8 dB (SD: 7 dB) compared to soft band. For the Australian arm: Mean speech discrimination (monosyllabic words in quiet) score gain with BAHA Attract was 40.7 dB. Speech discrimination in noise was also improved (mean signal to noise difference gain of 10.6 dB). Pure Tone Audiometry results were not available and masking was applied to the contralateral ear at all conditions. Powell et al. (2015) [
26] published their results on a study that compared outcomes between 6 patients with BAHA Attract and 6 that were implanted 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. Mean unaided PTA was 60.8 dB HL and mean aided PTA 30.6 dB HL. Most gain was noticed at the lower and mid frequencies. At 55 dB, unaided SRT were around 18.5 %, but when aided, they improved to around 87 %. Mean speech perception score gain at 55 dB was 70 %. Carr et al. (2015) [
27] reported on 10 patients who were implanted the BAHA Attract device. They performed word discrimination scores (WDS) in 3 of the patients with CHL using Boothroyd sentences. When aided, there was an increase in WDS of 50 % at 30dBA (from 0 % to 50 %), and 56 % at 50 dBA (32 % to 88 %), which was not statistically significant. Finally, Deveze et al. (2015) [
6] reported on one case where a percutaneous bone conduction implant was changed to a BAHA Attract due to recurrent episodes of skin reactions around the abutment (Holgers Grade 3) that failed to improve despite having a longer abutment fitted and local treatment. The initial procedure involved soft tissue reduction. Upon removal of the abutment an interval of 2 months was kept for the skin to heal before re-operating. The authors, concerned about the skin quality and further pressure to skin by the magnet, used a superficial fascia temporalis flap that was stitched around and sheltered the magnet. Audiological results were not presented however the patient reported a decrease in the output compared to the previous percutaneous device. It is commonly accepted that the hearing gain with BAHA Attract is lower than the percutaneous BAHA, therefore they are best used in patients with normal or mildly affected cochlear function. If the hearing deteriorates (e.g. due to aging) conversion to a percutaneous BAHA device should be considered and is a straightforward procedure since there is no need to replace the fixture [
2].
Table 3
Study design, Outcome measures and results
| Retrospective case series | Soundfield testing: PTA and SRT | PTA: 41 dB HL SRT: 56 dB HL |
| Prospective cohort study | QoL questionnaires: GBI, APHAB, BAHU Free field speech in noise audiometry | APHAB: 23.5 % improvement GBI: 29.6 % improvement BAHU: “Good” or “very good” by 85 % of patients Speech in noise: 32.9 % |
| Case report | N/A | N/A |
Iseri 2014 [ 24], Iseri 2015 [ 9] | Multicentre retrospective cohort study | Free field PTA and SRT QoL questionnaires: GBI | PTA: 27.3 dB HL SRT: 24 dB HL GBI: 40.5 |
| Prospective case series | Free field PTA and SRT | PTA: 25 dB HL SRT: 63 % |
| Multicentre prospective cohort study | Free field PTA and SRT Speech in noise audiometry QoL questionnaire: APHAB | PTA: 18.4 dB HL SRT: 50 dB HL at 50 dB SPL Speech in noise: 15 dB HL APHAB: significant improvement p < 0.05 |
| Cross-sectional cohort study | Free field PTA and SRT QoL questionnaires: Bone Anchored Hearing Devices questionnaire | PTA: 30.2 SRT: 72.5 Bone Anchored Hearing Devices Questionnaire: mean score 9.7/10 |
| Retrospective cohort study | Free field speech discrimination QoL questionnaires: GBI, COSI | Speech discrimination: 56 % at 50 dBA GBI:82 % and 91 % (for previously aided vs not-previously aided patients) COSI: 86 % of patients could hear in background noise 95 % of the time |
The studies from Baker et al. (2015) [
23] and Powel et al. (2015) [
26] studied predominantly paediatric population and both observed greater improvement in mean aided thresholds (41 dB HL and 30.6 dB HL respectively) compared to other studies with predominantly adult population, such as the one from Briggs et al. (2015) [
22] who found improvements of 18.4 dB HL. Similarly, SRT appeared to be better in the paediatric population. This can be explained by the thinner soft tissue and less attenuation of vibration in children.