Effect of adhesion on the acoustic functioning of partial ossicular replacement prostheses in the cadaveric human ear

Background: Adhesion formation following ossiculoplasty surgery has been implicated as a cause of the progressive deterioration of an initially good postoperative hearing result. Scar tissue between the partial ossicular reconstruction prosthesis (PORP) and adjacent middle ear structures is a common finding at revision surgery. Objectives: This study aims to investigate the effects of simulated scarring on the microacoustic transmission characteristics of a PORP in the fresh cadaveric human temporal bone. Methods: Cortical mastoidectomy and extended posterior tympanotomy permitted access to reflective markers placed on the stapes footplate. A sound stimulus at 80 to 95 dB was presented to the closed external ear canal and displacements were measured with the laser Doppler vibrometer. PORPs were placed in cadaveric specimens, and the shaft of the prosthesis was cemented to the adjacent promontory using dental cement. Serial measurements were made from the stapes footplate as the adhesive was allowed to harden, a process that we have taken to simulate the gradual fixation of the prosthesis by scarring in the live patient. Results: There was a consistent reduction in stapes footplate displacement as the cement hardened. Conclusion: The gradual adhesion of a PORP to the promontory produces a consistent reduction in microacoustic transfer to the stapes footplate in the fresh human cadaveric model.