A new tool for testing ossicular mobility during middle ear surgery: preliminary report of four cases.

Objective: We developed an ossicular vibration tester for the objective and quantitative assessment of ossicular mobility, which is one of the most critical factors affecting postoperative hearing after tympanoplasty.
Methods: Our device consists of three components: a probe shaft with a curved tip to be attached to the target ossicle, a vibration exciter to activate the probe, and a piezoelectric sensor to detect vibrations of the probe. These components are encased in a stainless steel holder, allowing easy hand manipulation during ear surgery. The probe is activated with an electric signal at around 1,600 Hz. The system is controlled with a laptop computer, and the results are presented as the ratio of the ossicular resistance (ROR) to a reference value as a percentage. One measurement takes 10 ms. The device was applied in four selected patients during ear surgery.
Results: Several measurements in two of the cochlear implantees showed a greater difference in the RORs of the stapes (15-20% in Case 1 and 35-45% in Case 2), whereas the RORs of the malleus and incus were within the same range. This was thought to correspond to the partial cochlear calcification noted in Case 2. In Case 3, who underwent surgery because of otosclerosis, the ROR of the stapes was high, ranging from 70 to 80%. When measured for the malleus-incus fixation anomaly (Case 4), the ROR of the malleus and incus was in the range of 60 to 70%. Owing to the limited surgical view, the ROR of the stapes could not be measured. No problems related to the measurements with this device were noted.
Conclusion: The design, principles, measuring procedures, and preliminary results of our new tool for testing ossicular mobility are reported. Measuring the ossicular mobility during surgery may provide important information for deciding the surgical procedures.