Assessment of Temporal Bone Thickness for Implantation of a New Active Bone-Conduction Transducer.

OBJECTIVE: To investigate the minimum bone thickness in adults and children in the area of the skull affected by implantation of a new bone conduction device in patients without known medical history that indicates anatomical malformations. STUDY DESIGN: Retrospective, non-interventional study on computer tomography (CT) scans on file at a university medical center. STUDY METHODS: A digital model of the new bone conduction implant was virtually implanted in 3D reconstructions of temporal bones based on 197 CT scans, 132 from adults and 65 from children (evenly distributed in five different age groups). The bone thickness was measured in a total of 11 designated positions; five measurement points for the transducer (recess area), and six for the fixation screws, corresponding to three different positions for the fixation band holding the implant in place (screw area). RESULTS: The minimum bone thickness in the combined recess and screw area for adults was 5.55 ±â€Š1.46 mm, with a 95% CI of 5.30 to 5.80 mm. For children, the thickness was 4.34 ±â€Š2.29 mm (95% CI: 3.77-4.91 mm), increasing from 1.92 mm (0-4 yr) to 6.41 mm (12-14 yr). For all ages, the bone in the recess area was generally thicker compared with the screw area.With an implantation depth of 3 mm the transducer fitted in all of the adult temporal bones (100%) and 99.2% (131/132) of the adults had a bone thickness of at least 2.7 mm in all six measured screw positions. In all children from the age of 5 the transducer fitted at an implantation depth of 3 mm, and in all children from the age of 9, the fixation screws fitted at a depth of 2.7 mm. In all CT scans except for a 6-month-old child the new bone conduction device could be implanted in at least one of the fixation band positions analyzed. CONCLUSIONS: In adults and many children without known medical history that indicates anatomical malformations, the average minimum bone thickness was thicker than both the maximum transducer depth of 3 mm and the 2.7 mm bone involvement of the osseointegrating fixation screws. The results indicate implant fit of the new bone conduction implant in all adult patients. The risks of compromising the sigmoid sinus and the dura as considered with larger implants are thus significantly reduced. Preoperative planning with CT would still be recommended for children below 9 years old.

Ten years of experience with the Ponto bone-anchored hearing system-A systematic literature review.

BACKGROUND: Bone-anchored hearing systems (BAHSs) are widely used for hearing rehabilitation and are indicated in cases of conductive and mixed hearing loss and in single-sided deafness. The Ponto system, that is one available option, has been on the market since 2009. OBJECTIVE OF REVIEW: The aim of this study is to systematically review the literature reporting on the Ponto system, with regard to audiological and surgical outcomes and patient's quality-of-life scores. TYPE OF REVIEW: A systematic literature search was performed in the PubMed database 2009-July 2019. SEARCH STRATEGY: Search term: ((osseointegrated hearing aid) OR (bone conduction implant) OR (bone anchored hearing) OR BAHA OR BAHS OR BAHI). Pre-defined inclusion and exclusion criteria were applied. EVALUATION METHOD: English-language articles reporting original clinical data (audiological, surgical or quality-of-life outcomes) on the Ponto system were included. Articles reporting on Ponto and another BAHS system where the results on Ponto constituted less than 50% of the patient population or including only results on testband or softband devices were excluded. RESULTS: Audiological outcomes were discussed in 20 publications. Improvement against the unaided thresholds was demonstrated. The functional improvement was on average 33.9 dB. The effective gain or remaining air-bone gap was on average 6.7 dB. All evaluated data showed aided speech reception thresholds significantly below normal speech level. Twenty-seven publications reported surgical and follow-up data for the Ponto system. Implant survival was 97.7%, adverse skin reactions (Holgers ≥ 2) were 5% across visits and 15% across patients. No complications were life-threatening, causing permanent disability/damage or requiring a hospitalisation. Five studies reported quality of life using the Glasgow benefit inventory, 98% reported an improvement when analysing the score on an individual level. CONCLUSIONS: The outcomes of this systematic review confirm that percutaneous systems provide consistent audiological benefits and improved quality of life for patients. Further, the review demonstrates that the percutaneous systems are safe, with relatively low complication rates. Skin-related complications are the most common complication type and are experienced by approximately one patient out of seven, or in less than one of 20 follow-up visits.