HSC Section 8_April 2017

direct contact between the FMT and RWM could be attained, the

‘‘direct coupling with no fascia interposed’’ technique as per

Rajan et al. (8) was utilized.

Vibroplasty Coupling Measurements

The measurement of the vibroplasty thresholds is similar to

pure-tone audiometry with the stimulus being presented via the

FMT. All vibroplasty measurements were implemented using a

spare clinic Amade´ low processor and the ‘‘vibrogram’’ function

available in the manufacturer’s software. The vibrogram is a pure-

tone audiogrammeasured through the VSB processor and implant.

Behavioral vibroplasty thresholds are determined by applying the

modified Hughson-Westlake method (15). It is now common pro-

cedure and recommended by the manufacturers to use the thresholds

attained via the vibrogram, to set the processor’s initial fitting levels.

Results are reported on a decibel scale, which is normalized to

the maximum transducer excitation voltage of the FMT (dB re.

4.47

V). To find a relationship between vibroplasty thresholds

and traditional bone conduction thresholds, the vibroplasty thresholds

are entered into a scatter plot versus corresponding bone conduction

thresholds. In addition, a linear trend is calculated for each test fre-

quency. The orthogonal distance between the trend line and data

points of one individual subject, measured in decibels and averaged

across all test frequencies, is used to calculate the relative coupling

efficiency. The underlying assumption is that data points below the

regression line are indicative for ‘‘good’’ coupling, which means

‘‘better than the average within the study’’. Please see Supplementary

Digital Content 1

(http://links.lww.com/MAO/A316

) for an example

of how coupling efficiency is calculated.

Audiologic Testing

Speech in Quiet

Standard audiologic measures included air and bone con-

duction testing, and monosyllabic speech perception testing

using AB (Arthur Bootroyd) Words (16). These were conducted

preoperatively and at 1, 3, 6, and 12 months postoperatively and

annually thereafter.

The free field speech testing in quiet consisted of recorded

Consonant Nucleus Consonant (17) (CNC) monosyllabic words

presented at 65 dB SPL through a speaker located 1 m directly in

front of the patient in the following conditions:

1. implanted ear unaided, and

2. implanted ear wearing the VSB.

The contralateral ear was effectively masked.

Quality of Life Measure

The Tinnitus Reaction Questionnaire (TRQ; 19) was used to

assess the impact of tinnitus on well-being, emotions, and lifestyle.

The TRQ was completed before and 3, 6, and 12 months post-

surgery after to compare the postoperative outcomes. A maximum

score of 104 and a minimum score of 0 can be attained on the TRQ.

A score of 17 and above denotes clinically significant tinnitus

disturbance.

Surgical Technique

A diagrammatic representation of the FMT positions employed

can be seen in Figure 1. When coupling the FMT to the stapes or

incus, it was critical to confirm transmission through the chain or

remnant via the presence of the round window reflex. This in-

volved palpation of the stapes which induces a movement of the

RWM. The FMT is then crimped onto the long process of the incus

or the posterior crus of the stapes superstructure. When the FMT is

placed against the round window, the FMT titanium attachment

clip is removed. The FMT conductor link cable is then preshaped

to allow placement of the FMT against the RWM. This is after

reduction of the superior and anterior lip of the round window

niche to facilitate the FMT contact with the RWM. In cases of a

funnel-shaped or a deep, narrow round window niche, only a

limited degree of lip reduction is possible as the risk of an injury to

the cochlear endosteum or RWM is high.

Statistical Analysis

A Mann-Whitney

test was used to compare coupling effi-

ciency of the FMT in various placements: (a) fascia between FMT

and RW, (b) direct FMT contact, (c) FMT crimped to incus (long

process), and (d) FMT crimped to stapes (on the posterior crus).

The Wilcoxon signed-rank test was used to determine if there was

a significant change in results of speech recognition in quiet.

To detect differences between the preoperative TRQ test

results, a difference of 40% was deemed to be significant as per

the recommended analysis (18). A nonparametric Wilcoxon

signed-rank test was also applied.

RESULTS

Surgical Outcomes

Of the 16 patients, three required FMT re-positioning

within the first 6 months after implantation as per the results

FIG. 2.

Summary of coupling efficiency for individual patients. The smaller value is consistent with better coupling efficiency.

R. MARINO ET AL.

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