87 3.2 Clinical evaluation and resonance frequency analysis in Down Syndrome with an identical geographical catchment area, audiological and support team. The current study shows that the new wider implant system demonstrates a significant improvement in a syndrome matched cohort with regards to both soft tissue reactions and revision surgery rates. In addition, there is a significant improvement when compared to outcomes reported in 2005 by Sheehan et al. in which they evaluated BAHI surgery in children with DS. A 49% soft tissue complication and 9% implant failure rate was reported. In this study 43 individuals had been implanted in 18 centres across the UK and Ireland and included a cohort of 24 cases in patients under the age of 16 [18]. Paediatric patient groups pose a unique challenge. The characteristics of the temporal bone undergo change and development in early childhood. Osseointegration is influenced by bone density and trabecular-cortical bone ratios and, as skeletal bone shows dynamic changes in morphometric and compositional characteristics with age [41] this may influence both implant stability and ISQ results. Unlike the otic capsule, which is mature at birth, bone mineral density increases with age and occurs at different rates depending on the anatomical position within the cranial bones [42]. Takahashi et al. have demonstrated that the lateral surface of the mastoid (on which a BAHI is placed) is fully matured by 1.7 years of age, in comparison to the posterior cranial fossa and middle cranial fossa regions of the temporal bone which matures by the ages of 3.9 and 10.8 years respectively [41]. As the youngest participant included in our study was 4 years old, maturation of the lateral temporal bone should have occurred, however there is no published data on the maturation of the temporal bone in children with significant other medical comorbidities such as DS. Structural analysis of the temporal bone in DS patients has demonstrated mean volume changes of the epitympanum and mesotympanum which was significantly smaller than that of a control group [43] as well as hypoplasia and sclerosis of the mastoid bone [44]. It could be hypothesised that these bony changes may impact ISQ reading and osseointegration creating an artificially elevated recording. Therefore, as ISQ comparison is largely dependent on 2 assumptions: The resonance of the smart peg is uniform across all individuals. The absence of data confirming this in those patients with known variability in mastoid structure. This raises questions regarding the validity for direct comparison between groups especially in our current DS cohort as no previous ISQ data has been studied or published in patients
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