Measurement of Incus and Stapes Velocity Following Sound Stimulus in the Setting of Incudostapedial Joint Separation and Reconstruction.

OBJECTIVE: Understand the biophysical property changes of incudostapedial joint (ISJ) separation and ossicular hydroxyapatite application on middle ear function. STUDY DESIGN: Basic science. SETTING: Cadaveric temporal bone research laboratory. SUBJECTS AND METHODS: A complete mastoidectomy was performed on five human temporal bones. A Laser Doppler Vibrometer was utilized to obtain velocity transfer function measurements of the incus and stapes across a range of frequencies in response to an acoustic stimulus. Under binocular microscopy the ISJ was separated and subsequently repaired with bone cement. Measurements were taken prior to ISJ separation, following joint separation, 30 to 60 min postrepair of the joint, and again 24 to 48 h postrepair of the joint. RESULTS: The stapes measurements taken from the intact ossicular chain and from the chains repaired with bone cement demonstrated a similar distribution of measurements. The ISJ separation showed dramatically reduced velocity transfer function stapes measurements but increased incus velocity transfer function measurements. In the early and delayed repaired chains, the mean velocity of the incus and stapes velocity peaked between 1.5 and 2 kHz, matching intact maximal velocity. Pure tone average at 0.5, 1, 2, and 3 kHz demonstrated no change in reconstructed stapes velocity at 24 to 48 h. CONCLUSIONS: Isolated ISJ separation in fresh frozen and thawed temporal bones produces stapes velocity transfer function changes that corresponds with the clinically experienced conductive hearing loss. Repair with bone cement produced similar velocity curves to the intact ISJ curve with excellent recovery across mid-frequencies. This model would be useful for future ossicular mechanical studies.