Restoration of High-Frequency Middle Ear Function in Partial Ossicular Discontinuity: A Basic Science and Clinical Correlation

Hypothesis: Repairing partial ossicular discontinuity in cadaveric human temporal bones (TB) with bone cement will restore stapes velocity to baseline. Clinically, we expect improvement in high-frequency (HF, ≥4 kHz) hearing loss after surgical repair of partial ossicular discontinuity. Background: Partial ossicular discontinuity in cadaveric TBs reduces stapes velocity at HFs. Clinically, this manifests as a HF conductive hearing loss (HFCHL). The effects of joint reestablishment on HF hearing has not been widely studied. Methods: Six, unfixed, previously frozen human TBs from donors without known ear disease were used to study the mechanical effects of partial ossicular discontinuity before and after repair. Dual laser Doppler vibrometers measured sound-induced stapes and umbo velocity. Results were correlated with preoperative and postoperative audiometric thresholds from 2 patients who underwent endoscopic bone-cement repair of surgically confirmed partial ossicular discontinuity. Results: Partial joint discontinuity decreased stapes velocity by 20 dB from 2 to 14 kHz, and increased umbo velocity by 5 to 8 dB below 1 kHz. Repair with bone cement restored umbo and stapes velocity to baseline across frequencies. Clinically, 2 patients presented with HFCHL with air-bone gaps (ABG) ≥60 dB for patient 1 and ≥25 dB for patient 2, and hypercompliant middle ears on tympanometry. Postoperatively the 4 kHz ABG closed by ≥40 dB for patient 1 and completely closed for patient 2. Air conduction thresholds improved between 6 and 8 kHz, and tympanometry normalized. Conclusions: Bone cement repair of partial ossicular discontinuity restores middle ear HF sound transmission in temporal bones and improves HF air conduction hearing thresholds in patients, suggesting some HF hearing losses are conductive and are surgically correctable.