## 4 Discussion  
This research reports the reliability and surgical and medical complication rates for the BB and VSB devices from eleven United Kingdom hearing implant centers. A survival analysis was conducted based on surgical and medical questionnaires and records. From these data, we mapped out complications arising, their associated time course, and frequency of occurrence, and have associated these with patient etiologies. The BB had a high survival rate of 93.3% at the 5-year post-implant measurement point. This finding is in line with [PERSON] et al. [7], who followed patients with either BAHA, Ponto, or BB devices and reported a 95.7% survival rate (1 out of 23 explanted) for BB. The mean follow-up in [PERSON] et al. 's study was 36 months, compared to 48 months in this study. Our case series is four times as large with a similar survival rate. The two cases of explantation in our series were due to one case of pain and one case of device failure due to wire breakage. In [PERSON] et al. [7], the single explantation case was due to infection at the wound site. There wasn't a clear pattern of causes that led to device failure; however, the number of device failure cases was too small to observe any patterns. There were three cases of wound infection in our series, but they did not require explantation. One was resolved with oral antibiotics, and two required intravenous antibiotics. Although not requiring explantation, the latter two did necessitate an overnight hospital stay. [PERSON] et al. [8] in a systematic review looked at outcomes for BB patients by conducting a meta-analysis of the findings from 49 papers of cohort or case-control studies. The individual articles reported results for between 2 and 38 cases, with a total of 286 ears being evaluated. The average follow-up was 11.7 months (standard deviation \(+/-\) 4.5). They reported a lower explantation rate, with a survival rate of 98.3%, but this was over a significantly shorter time scale than reviewed in our data. They reported a 7.7% minor event rate; for similar events, our equivalent number is eleven cases, a 10% rate, or a similar incidence. In our dataset, there were three BB cases where the skin flap was too thick. One case was unresolved, and two cases required additional surgery to reduce the flap thickness. Figure 5: Survival plot for the Soundbridge (VSB) device. The number of cases with data at the recorded timepoints is shown below the figure. These problems can be reduced if a skin flap gauge is used during the surgery to identify a skin flap that needs to be thinned [9]. For the BB in our dataset, there were twelve events that did not require a return to the surgical theater. Seven cases required magnet strength reduction due to pain following the use of a higher magnet strength at the initial fitting to ensure a secure fit, but after some time this strength was too high. Initial post-operative swelling at the first fitting of the sound processor required a stronger magnet than was later necessary as swelling reduced. This resulted in unwanted pressure and pain. Another explanation is that although there may not have been a change over time in the wound region, the clinician and patient opted for a slightly stronger magnet than necessary to be confident of good retention. Nevertheless, the findings have highlighted the need to be mindful when setting the magnet strength for the BB and that clinicians should monitor this closely over time. The remaining minor events showed no pattern of occurrence. The survival rate for the VSB was 87.0% at the 5-year post-implant follow-up, lower than for the BB (93.3%). The lower rate for the VSB may reflect the more complex surgical procedure and the patient characteristics of those receiving a VSB, who tended to have a more complicated hearing health history. Many patients had previously experienced unsuccessful attempts at using other hearing devices. [PERSON] et al.