Magnetically driven middle ear ossicles with laser vibrometry as a new diagnostic tool to quantify ossicular fixation

Information on the degree of incus fixation can be gathered by measuring the ratio of incus to umbo long process velocity through the ear canal.

To test a new method of quantifying partial ossicular fixation in an ear with an elevated tympanic membrane.

Measurements were made on four fresh-frozen human temporal bones. After elevating the tympanic membrane a small magnet was attached to the manubrium and an electromagnetic excitation coil was used to vibrate the ossicles. The vibration response of the tip of the incus long process and the umbo were measured before and after artificially fixating the incus to the lateral attic wall.

Partial incus fixation resulted in a decrease in both the incus and umbo velocities, with the incus velocity being more severely reduced. The decreased ratio of their vibrations is a clear indicator of the degree of incus fixation.