3.3 Comparison of audiological performance between the FTTC and
PTTC groups
First, baseline characteristics between the two groups were compared,
and no statistically significant differences were observed (Table 2).
The mean ABG values in the PTTC and FTTC groups were 12.5 (8.75–16.25)
dB and 11.25 (6.25–15) dB, respectively, with no significant difference
between the two groups (Z = -0.958, P = .338, Figure 3B.). At
frequencies 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz, there was no
significant difference in ABG values between the two groups (P> .05) (Table 3). The postoperative ABG in the FTTC group
at 250 Hz was 15 (10–20) dB, which was better than that in the PTTC
group (15 [15–20] dB, Z = -2.277, P = .023).
Discussion
Hearing improvement was achieved irrespective of the preoperative
tympanic perforation size and malleus handle exposure status in the FTTC
group. The postoperative ABG was comparable in the TF and PTTC groups.
Moreover, the audiological improvement at 250 Hz was better in the FTTC
group than in the PTTC group.
Endoscopic myringoplasty has received special attention in recent years.
The grafts used in myringoplasty are diverse, such as temporalis muscle
fascia,6 tragus perichondrium,7,8tragus cartilage and perichondrium complex,9 and
porcine small intestine submucosa.10 Minimal invasion
and easy harvest, less postoperative pain, quicker postoperative
recovery in anatomy and function, and strong ability to resist
inflammation are the requirements of an ideal graft; since it meets the
requirements, tragus cartilage is the material of choice. Moreover, it
does not require an extra incision behind the ear, thereby avoiding
long-term numbness 11 after the operation.
Endoscopic myringoplasty is a flexible and variable procedure as it
facilitates multiple choices of grafts, varied graft placement, and
different surgical approaches; however, on the downside, diversity may
lead to discrepancies in postoperative hearing performance. There are
three main cartilaginous grafts: perichondrium, full-thickness cartilage
with perichondrium complex, and thinned cartilage with perichondrial
complex. The commonly employed surgical approaches include the ”put
through”12 method, which does not involve the
elevation of the tympanomeatal flap, and the method involving the
elevation of the tympanomeatal flap. The location of graft placement
also varies, such as incarceration on the tympanic membrane (”butterfly”
method),13 placed between the tympanic membrane and
the malleus handle, or medial to the malleus handle. In this study, a
broad tympanomeatal flap was lifted, and the FTTC was placed between the
malleus handle and the tympanomeatal flap. In both traditional
microscopic tympanoplasty with the TF and the FTTC surgery, a similar
hearing performance was achieved after the surgery. In a
meta-analysis14 where different research groups
adopted different surgical and graft placement strategies, a
sub-analysis of prospective studies showed a lower mean postoperative
ABG in patients using TF graft. The heterogeneity may have affected the
stability of the results and led to the difference.
For all frequencies except 250 Hz, a similar audiological performance
was observed in the FTTC and PTTC groups; FTTC had a better performance
at 250 Hz. Similar comparisons were drawn in another
study,4 where no significant differences were observed
in hearing improvement between the PTTC and the FTTC groups at 250 Hz,
500–2000 Hz, and 8000 Hz. Overall, our findings were in agreement, but
PTTC had a better performance at 4000 Hz in the other study, whereas
FTTC had a better performance at 250 Hz in our study. In the same study,
the tensor tympani tendon was cut to make space in cases where the
handle was foreshortened or medially displaced. This manipulation may
have led to poor performance in the FTTC group at 250 Hz. The tensor
tympani tendon cut did not affect hearing at 0.5 Hz–4 kHz after
tympanoplasty,15 but tensor tympani tendon contraction
is related to low-frequency hearing loss.16 In
addition, barred cartilage, which might result in decreased tension of
drum, was placed under the malleus, which may be responsible for the
poor performance at 4000 Hz in the FTTC group in their study. In the
future, the effect of tensor tympani tendon cut on low-frequency hearing
can be explored.
Although reports on myringoplasty with FTTC graft have demonstrated good
hearing performance, only a few articles have provided a convincing
theoretical explanation. A study on biomechanical
analysis17 suggested the use of grafts with a
thickness of 0.1–0.2 mm for medium-to-large perforations and
<1.0 mm for small perforations, where the graft is a
substitute for both mechanical stability and audibility. However, in
this study, the thickness of the FTTC was 0.850 ± 0.117 mm, and good
hearing results were obtained at each frequency. The middle ear can only
provide about 20 dB of gain on average18 and most of
the gain comes from the area ratio of the tympanic membrane to the
stapes. The air-containing middle ear cavity can reduce the sound
pressure on the round window membrane.19 Figure 1F
shows that the graft fits well with the malleus handle; the new
cartilage drum could provide a sufficient drum area and an aired cavity,
so the graft would fit well and a good hearing performance with FTTC
graft could be achieved. Moreover, a better hearing performance at 250
Hz was achieved in the FTTC group than that in the PTTC group. The
possible reason for this could be that FTTC changes the stiffness of the
tympanic membrane, which may be beneficial in low-frequency conductions.
However, it does not mean that the FTTC graft can replace the PTTC
graft, which is convenient for postoperative examination and
manipulation.
Postoperative hearing performance in the FTTC group was independent of
the preoperative tympanic perforation size and the exposure status of
the malleus handle. According to our previous research, factors such as
the state of mucosa and location of tympanic perforation do not affect
the trends of ABG.5Another study also reported similar
results.20 In a previous study, a linear correlation
was observed between the preoperative tympanum perforation size and
postoperative ABG (P = .0017) at frequencies of 0.5 to 4 kHz,
indicating an increased postoperative ABG in larger perforations;
however, here, we specified only the P -values and did not provide
the correlation coefficient or other parameters that reflect the
relationship between the perforation size and postoperative ABG.
There are some limitations of this study. First, this was a
retrospective analysis performed at a single center. Second, the sample
size of the TF group was small, and the baseline characteristics between
the TF and FTTC group were imbalanced. However, PSM was performed to
resolve the issue of imbalanced baselines and sample sizes. Third, the
follow-up duration of this study was short. The patients at this center
came from all over the country. Since improvement in hearing and dry ear
was observed in the early days after the surgery and a longer follow-up
meant increased loss to follow-up, we chose 3 months as the endpoint of
follow-up.