Temporal bone thickness in Japanese pediatric patients: Implications for the timing of bone conduction device surgery.

OBJECTIVE

Western guidelines for bone conduction devices (BCDs) recommend implantation at age ≥5 years, but their applicability to Japanese children remains unclear due to potential racial differences in skeletal development. This study measured temporal bone thickness in Japanese children using computed tomography (CT) to determine the anatomically appropriate surgical age.

METHODS

We analyzed head CT images from 217 Japanese children (0-15 years) without temporal bone abnormalities. Bone thickness was measured 1 cm posterior to the sigmoid sinus at two points: the "upper level" (superior semicircular canal level; Baha® site) and "lower level" (lateral semicircular canal level; Osia® site). We analyzed age-thickness correlations and determined the age at which 3 mm thickness was achieved.

RESULTS

Bone thickness correlated positively with age. While no difference existed between sites at ages 0-2, the upper level developed more rapidly from age 3 onwards. The 3 mm thickness threshold was reached in 50% and 90% of cases at 5.3 and 10.3 years, respectively, for the Baha site, while it was 6.6 and 12.8 years for the Osia site.

CONCLUSION

Anatomically, a conservative surgical indication age of 6-8 years is reasonable for Japanese children, compared with the Western 5-year standard. For children <10 years, a 3 mm fixture is preferred to prevent complications. The Baha site offers advantageous bone thickness in children >3 years. However, due to significant individual variation, preoperative CT assessment is very important.