Evolving Acoustic Characteristics of the Canal Wall Down Cavities Due to Neo-Osteogenesis by Periosteal Flap

Objective To determine whether the acoustic properties of the canal wall down cavity would come closer to those of the normal ear canal as the cavity is lined with periosteal flap. Study Design Prospective study. Setting Tertiary referral center. Patients Twenty one subjects who underwent canal wall down mastoidectomy and total ossicular replacement prosthesis tympanoplasty were selected. Interventions Canal wall down cavities were lined with postauricular periosteal flap. The acoustic properties of 21 canal wall down cavities (mastoidectomy ears) and 16 contralateral normal ears (control ears) were measured with a hearing aid fitting system. Main Outcome Measures Frequency, amplitude, bandwidth, and Q factor of the resonance curve along with the loss in amplitude below 1 kHz were compared in a paired-wise manner between the first and third months and the third and sixth months postoperatively in mastoidectomy ears, and also between mastoidectomy and control ears. Results In the mastoidectomy ears, the peak resonance frequency and bandwidth significantly increased at the end of the third and six months as the volume of the cavity decreased (p < 0.05). However, the amplitude and Q factor of the resonance curve remained stable. At the end of the first month, all parameters were different in both groups (p < 0.05). At the end of the sixth month, the frequency and bandwidth of the resonance curve in both groups were not different. The mastoidectomy ears had some decibel-amplitude loss below 1 kHz. Only its frequency changed as the cavity became smaller (p < 0.05). Conclusions New bone formation facilitated by a periosteal flap in the posterior part of the CWD cavity behind the facial ridge may provide acoustic properties similar to those of the normal ear canal.