gms | German Medical Science

The use of cartilage as a graft material for tympanic membrane (TM) reconstruction has been widely established, with an emphasis on avoiding contact with the bony rim of the ear canal to achieve optimal audiological outcome. However, the influence of cartilage graft position on hearing remains unclear.

This study evaluates whether the contact of the cartilage graft with the bony rim affects the auditory outcome. We used six fresh-frozen temporal bones and created a 2.5 mm perforation in the posterior lower quadrant of the TM. Stapes velocity was measured using single-point Laser-Doppler Vibrometry (LDV) before and after TM reconstruction, with the cartilage graft either in contact with the bony rim (on-bony) or not (off-bony). Additionally, we employed a Scanning-LDV of a 3D-printed ear canal model, with an artificial TM to simulate TM movement due to the beforementioned perforation and reconstruction.

Following TM perforation, the middle ear transfer function (METF) significantly decreased between 500–2,000 Hz. Both on-bony and off-bony reconstruction METFs differed from the intact TM in the 800–1,000 Hz range (on-bony) and 700–1,000 Hz range (off-bony). No significant difference in METFs was observed between the on-bony and off-bony techniques (p>0.1). Scanning-LDV analysis of the 3D-printed TM model showed similar results, where no significant difference in TM peak displacement between the two graft positions were obvious. The off-bony technique, however, resulted in a shift to lower frequencies of the artificial TM best frequency compared to the on-bony technique.

This study demonstrates that the position of the cartilage graft relative to the bony rim of the ear canal does not significantly impact the METF. Positioning the cartilage graft on the bony rim is a viable option in patients with chronic middle ear disease.