Claus Nielsen

Research Audiologist

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Knowing the position of the Cartilage-Bone Junction (CBJ) in the ear canal is crucial when making a deep-fitting hearing aid. The CBJ should either be avoided for reasons of wearing comfort, or a bony seal should be created to combat the occlusion effect.

Data collection and registration

915 impressions from an Oticon production site were inspected. The ear canal typically has two bends, and all impressions extending beyond the second bend were singled out, as these are most likely to include the CBJ. 84 impressions met this criterion and were subsequently laser scanned. The CBJ was then manually identified and marked on each scanned impression.


Observations on the position of the CBJ

Examination of the individual ear scans showed that the average distance from the second bend of the ear canal to the CBJ is 1.8 mm, i.e. the CBJ is usually found beyond the second bend. The position of the CBJ ranged from -1 mm to 4 mm relative to the second bend. This implies that ear impressions must be taken well beyond the second bend to include the CBJ with certainty, while considerable individual variation must be expected.

Further reading

Nielsen C, Darkner S (2011). The cartilage bone junction and its implication for deep canal hearing instrument fittings. Hearing journal, 64(3), pp. 35,36,40,42.