Download Apr03: FIXATION OF THE ANTERIOR MALLEAR LIGAMENT

Ann Otol Rhinol Laryngol 112:2003
Ann Otol Rhinol Laryngol 112:2003
REPRINTED FROM ANNALS OF OTOLOGY, RHINOLOGY & LARYNGOLOGY
April 2003
Volume 112
Number 4
COPYRIGHT© 2003, ANNALS PUBLISHING COMPANY
FIXATION OF THE ANTERIOR MALLEAR LIGAMENT: DIAGNOSIS
AND CONSEQUENCES FOR HEARING RESULTS IN STAPES SURGERY
ALEXANDER HUBER, MD
ZURICH, SWITZERLAND
TAKUJI KOIKE, PHD
HIROSHI WADA, PHD
SENDAI, JAPAN
SENDAI, JAPAN
VEL NANDAPALAN, MD
UGO FISCH, MD
LIVERPOOL, ENGLAND
ZURICH, SWITZERLAND
In the search for possible causes of unfavorable results after stapes surgery, the study reported here focused on the anterior
mallear ligament, since it has been previously reported that partial mallear fixation (PMF) leads to functional failure in 38% of cases
of stapes revision surgery. The aims of the study were to identify effective methods for the diagnosis of PMF and experimentally
assess the conductive hearing loss that results from PMF. The study included vibration amplitude measurements of the ossicles by
laser Doppler interferometry (LDI) in 19 patients and 5 fresh human temporal bone (TB) specimens. Analysis of their dynamic
behavior was performed by finite element modeling (FEM). Similar, significant changes of manubrium vibration patterns for PMF
were found by FEM calculations, in TB experiments, and in patients. We could identify PMF either before operation, using LDI, or
during operation, by manual palpation. In the TB experiments and FEM calculations, the attenuation of the stapes displacement due
to an isolated PMF was approximately 10 dB and frequency-dependent. Untreated anterior mallear ligament fixation produced a
persistent air-bone gap of approximately 10 dB after stapedioplasty.
KEY WORDS — anterior mallear ligament, conductive hearing loss, laser Doppler interferometry, mallear fixation, malleus,
middle ear mechanics, otosclerosis, stapes surgery.
INTRODUCTION
nosis of AML fixation? and What loss in sound conduction results from isolated fixation of the AML?
Since AML fixation occurs in combination with otosclerosis, these questions cannot be answered directly
by a clinical study. Therefore, a 3-pronged study of
clinical data, human TB experiments, and analyses
of a mathematical middle ear model was conducted
to ensure maximum reliability of the conclusions.
Complete bony fixation of the malleus is a welldocumented disorder that can occur alone or in conjunction with otosclerosis,1-4 and it leads to a conductive hearing loss of 15 to 30 dB.5-7 The fixation
is easily detected during operation by palpation with
a hook. Partial fixation of the malleus, on the other
hand, has been reported only recently in the literature. In a study on revision surgery for otosclerosis,
37.5% of patients exhibited partial fixation of the
malleus caused by calcification of the anterior mallear
ligament (AML) and anterior mallear process (AMP),
which made malleostapedotomy necessary.1 Histopathologic investigation of our temporal bone (TB)
collection has confirmed the presence of severe hyalinization of the AML in 30% of 43 otosclerotic specimens.8 Although attenuation of sound conduction
through the middle ear is expected with partial mallear fixation, no quantitative figures have appeared
in the literature.
MATERIALS AND METHODS
A laser Doppler interferometry (LDI) system was
used to measure the vibration of the middle ear. Preoperative mallear vibration patterns were measured
in the clinical study in patients with otosclerosis, and
were compared with the intraoperative diagnoses of
AML fixation. In the TB experiments, vibration patterns of the malleus and stapes were measured in the
normal situation and after the AML was experimentally fixed. All experimental data were then compared
to the response of a mathematical middle ear model.
Clinical Trial. Nineteen patients with an intraoperatively confirmed diagnosis of otosclerosis and no
The study reported here was designed to answer 2
questions: Are there effective methods for the diag-
From the Department of Otorhinolaryngology–Head and Neck Surgery, University Hospital of Zurich (Huber, Nandapalan), and the Otorhinolaryngology Center, Hirslanden Clinic (Fisch), Zurich, Switzerland, and the Department of Mechanical Engineering, Tohoku University, Sendai,
Japan (Koike, Wada).
Presented in part at the meeting of the Association for Research in Otolaryngology, St Petersburg Beach, Florida, February 4-8, 2001.
CORRESPONDENCE — Alexander Huber, MD, Dept of Otorhinolaryngology–Head and Neck Surgery, University Hospital of Zurich, Frauenklinikstrasse 24, 8091 Zurich, Switzerland.
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Huber et al, Anterior Mallear Ligament
Fig 1. Intraoperative exposure of incudomalleal joint, anterior mallear ligament (AML), and anterior mallear process (AMP) by endaural approach with superior canaloplasty. MA — malleus, IN — incus, LMP — lateral mallear process, CT — chorda tympani, TMF — tympanomeatal flap.
history of previous surgery on the ear of interest were
included in the study. All patients were evaluated before operation by audiometry, tympanometry, and
LDI. The average age of the patients was 41 years
(range, 19 to 67 years), and 13 of them were female.
Preoperative audiometry revealed a conductive hearing loss in all cases. The following tympanograms
were presented: normal (type A) in 6 patients, deep
type (type Ad) in 3 patients, and shallow type (type
As) in 10 patients. The stapedius reflex was absent
in all cases. For further analysis, the patients were
divided into “otosclerosis” and “otosclerosis and
AML fixation” groups, corresponding to the intraoperative findings. Informed consent to participate
in the study was obtained from all patients.
An endaural approach with superior canaloplasty
was performed in all patients to enable an overview
of the anatomic structures that may limit the mobility of the ossicles. Figure 1 shows the view of the
AML, AMP, and incudomalleal joint that is achieved
by this technique.
The mobility of the malleus was assessed by gentle
palpation of the malleus handle with a 1.5-mm, 45°
hook in the horizontal and vertical planes. This maneuver allowed a distinction to be made between normal mobility and total or partial fixation of the malleus. If there was any doubt about this, the maneuver
was repeated after disruption of the incudostapedial
joint. Ears with total fixation of the malleus were
excluded from the study. Intraoperative assessment
of the malleus was considered the gold standard. All
patients with normal mobility of the AML underwent
conventional stapedotomy. If a partial mallear fixa-
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tion was found during operation, a malleostapedotomy was performed. A more detailed description of
the operative technique is available elsewhere.1
Temporal Bone Preparation. Six fresh human TBs
were used for the study. The material was harvested
within 24 hours after death, stored in a 0.1% Cialit
(sodium-2-ethylmercurimercapto-benzoxazol-5-carbonide) solution (ASID Veterinär Vertriebs GmbH,
Unterschleissheim, Germany) at 5°C, and used for
measurements within 5 days. Inspection of the tympanic membrane and middle ear with an operating
microscope revealed that 1 TB exhibited tympanosclerosis, so only the remaining 5 TBs were included
in the study. The anterior wall of the external auditory canal was drilled down to a 1-mm rim, and a
transparent sound chamber (plastic tube, closed by a
cover glass) with a volume of 2 cm3 was placed over
the tympanic membrane. Mastoidectomy, posterior
tympanotomy, and partial removal of the facial nerve
were performed to allow maximum visualization of
the stapes footplate. The AMP and AML were approached through the tegmen tympani, with great care
being taken not to injure the superior mallear ligament. All measurements were conducted with an intact tympanic membrane, ossicular chain, ligaments,
muscles, and inner ear, and the middle ear cavity was
not sealed from ambient air. Baseline LDI measurements of the motion of the manubrium and the stapes
footplate were conducted before changing the properties of the AML and AMP. The mobility of the AML
was reduced by using a needle to apply 1 drop of
Histoacryl (B. Braun Medica AG, Emmenbrücke,
Switzerland) to the AML through the tegmen tympani. This adhesive hardens within a few seconds in
the presence of wet tissues and is therefore able to
induce a partial mallear fixation. The LDI measurements of the motion of the manubrium and the stapes
were then repeated. The difference between the stapes
vibration amplitudes measured with and without isolated AML fixation was calculated as an equivalent
sound conduction loss.
Laser Doppler Vibrometry Interferometry Measurement Setup. A measurement system based on a
scanning helium-neon laser Doppler interferometer
(PSV200; Polytec GmbH, Waldbronn, Germany) was
used for the measurements. The sensor head and the
scanning unit were suspended from a balanced operating microscope stand (Contraves, Zurich, Switzerland). A built-in camera and a computer-driven mirror system controlled the position of the laser spot
(diameter, 10 µm) on the object with a spatial resolution of 5 µm. A multisinusoidal signal tone containing 31 frequencies between 500 and 8,000 Hz
was applied to a sound chamber positioned over the
tympanic membranes of the patients and the TB prep-
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100 picometers over all frequencies. All amplitudes
are given in terms of the peak displacement, and no
angle correction was performed. A more detailed description of the system has been published elsewhere.9
In the human subjects, a silicone tube probe microphone and a loudspeaker were placed in the ear
canal through a custom-made ear speculum, so that
the tip of the tube microphone was a distance of less
than 3 mm from the center of the eardrum. The ear
speculum was held in place by means of earmold
material (Otoform-A/Flex; Dreve Otoplastik GmbH,
Unna, Germany), and the head of the subject was
held steady by a vacuum pillow. Scanning LDI was
typically recorded from 100 points on the tympanic
membrane; however, only the movement patterns of
the umbo and the short process of the malleus were
analyzed for this study.
In the TB preparations, the acoustic stimulation
was applied to a transparent sound chamber and controlled by a tube probe microphone placed 1 to 2
mm from the tympanic membrane. The manubrium
vibrations were recorded in a way similar to that used
for the human subject measurements and were followed by assessment of the stapes footplate vibration amplitude. Stapes vibrations were recorded
through the enlarged facial recess, which yielded
visualization of the stapes footplate at an angle of
30° to its major displacement axis.
Finite Element Model. Finite element modeling
(FEM) is a mathematical method that allows the dynamic behavior of mechanical systems to be modeled with a high degree of spatial resolution. This
method has been applied widely in studies of the mid-
Fig 2. Finite element model of middle ear. Properties of
AML (a) and annular ligament (b) were modified in this
study.
arations. The sound produced by a loudspeaker (ER2; Etymotic Research, Elk Grove, Illinois) was monitored by a probe microphone (ER-7; Etymotic Research). The sound pressure level was calibrated to
be 80 dB SPL for each tone in the stimulation signal, resulting in a total sound pressure of the stimulus of 94 dB. For the analysis, only results with a
coherence of 90% or better were used, which corresponds to signal-to-noise ratios of 10 to 25 dB. The
threshold sensitivity of the LDI used is 300 nm/s,
which equals displacement amplitudes of less than
A
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B
Fig 3. Mean and standard deviation of preoperative pure tone audiograms of 14 patients with otosclerosis and 5 patients with
otosclerosis and partial mallear fixation. A) Air conduction thresholds. B) Bone conduction thresholds.
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Huber et al, Anterior Mallear Ligament
A
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B
Fig 4. Average displacement amplitudes of malleus in response to acoustic stimulation at 80 dB sound pressure level (SPL) in
14 patients with otosclerosis, and in 5 patients with otosclerosis and fixation of AML and normal displacement range. A)
Umbo. B) Short process (SP) of malleus.
dle ear.10-14 It is particularly effective in assessing
disorders that are difficult to evaluate in experimental or clinical studies. The model used in this study
has been extensively tested, and a full description of
it is available elsewhere.10 Figure 2 shows the components of the model. To simulate partial mallear fixation with a calcified AML, the Young’s modulus of
the normal AML (EAML normal = 2.1 × 107 N/m2)
was increased by a factor of 1,000. Thereby, mechanical properties similar to those of human bone are obtained (Young’s modulus of human humerus = 1.2 ×
1010 N/m2).15
To simulate otosclerosis, we increased the Young’s
modulus of the annular ligament of the stapes until
an attenuation of sound conduction of approximately 30 dB, mainly at low frequencies, was achieved.
An increase in Young’s modulus of 100 times was
required. The results of all calculations performed
are given in terms of the peak displacement amplitudes in response to an 80 dB SPL sound stimulus at
the tympanic membrane.
RESULTS
Clinical Trial. The means of preoperative air con-
A
duction and bone conduction thresholds and the standard deviations are given in Fig 3. The patients are
divided into “otosclerosis” and “otosclerosis and
AML fixation” groups, corresponding to the intraoperative mallear mobility assessment (normal vibration versus partially fixed malleus, respectively).
Solitary otosclerotic stapes fixation was found in 14
patients; in 5 patients, this occurred in combination
with AML fixation. There is no statistically significant difference between these 2 groups according to
the Mann-Whitney rank sum test. In the “otosclerosis and AML fixation” group, 3 patients presented
with normal tympanograms (type A), and 2 patients
with shallow tympanograms (type As). In the “otosclerosis” group, 3 patients presented with normal
tympanograms (type A), 8 patients with shallow
tympanograms (type As), and 3 patients with deep
tympanograms (type Ad). Again, no statistically significant difference was found according to a χ2 test.
The results of the LDI evaluation of the otosclerotic patients is given in Fig 4, which shows the average displacement amplitudes of the umbo and the
short process of the malleus. The normal ranges of
displacements for both the umbo and the short pro-
B
Fig 5. Individual displacement amplitudes of short process of malleus in response to 80 dB SPL acoustic stimulation at
tympanic membrane. A) In 14 patients with otosclerosis. B) In 5 patients with otosclerosis and fixation of AML.
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Huber et al, Anterior Mallear Ligament
352
Fig 6. Average displacement amplitudes of A) umbo, B) short
process (SP) of malleus, and C) stapes in 5 temporal bone
preparations in response to 80 dB SPL acoustic stimulation at
tympanic membrane. Baseline results (Normal) and results after
experimental AML fixation are given.
A
B
C
cess are also included.9 Figure 4A shows that there
is only a small difference in the umbo vibration amplitudes between the 2 groups, with the maximum
1.7-fold difference (4.5 dB) occurring at 2,200 Hz.
The differences are not statistically significant (p >
.05) as assessed by the Mann-Whitney rank sum test.
The displacements of the short process, however,
were significantly different between the 2 groups (p
< .05) at frequencies between 1,500 and 2,200 Hz,
with a maximum 3.5-fold difference (10 dB) at 2,000
Hz. Figure 5 gives the individual displacement amplitudes of the short process of the malleus for all
patients in the “otosclerosis” and “otosclerosis in
combination with AML fixation” groups. All patients
with AML fixation showed a significant notch in the
range 1,300 to 3,000 Hz. In the patients with otosclerosis, on the other hand, the displacement of the short
process increased up to a maximum at approximately
3,000 Hz, and decreased beyond this frequency. One
patient, however, showed a notch between 2,000 and
3,000 Hz (Fig 5A).
Temporal Bone Preparations. The average umbo
displacements in normal TBs and in TBs in which
the AML was fixed with Histoacryl glue are given in
Fig 6A. Fixing the AML had a noticeable effect only
at frequencies below 1,000 Hz, with a maximum 2fold difference (6 dB) at 700 Hz. The graph also shows
the range of displacements in 129 normal ears of live
human subjects.9 The average vibration displacement
of the short process is given in Fig 6B. Similar displacement amplitudes are present in normal TBs and
in TBs with a fixed AML, except for a notch at 1,600
Hz in which there is a 1.6-fold difference (4 dB). At
frequencies up to 2,400 Hz, differences in the stapes
displacement are in the range of 1.8-fold to 4-fold,
corresponding to an attenuation of the middle ear
transfer function of 5 to 12 dB (Fig 6C).
Finite Element Model. The calculated displacement amplitudes for the umbo, the short process of
the malleus, and the stapes for normal, otosclerotic,
and AML and AMP fixation models are shown in
Fig 7. Figure 7A includes the umbo displacements
for the normal, otosclerotic, and partially fixed mallei in combination with otosclerosis. Virtually no differences are present between the normal and otosclerotic models. In the case of the partially fixed malleus,
the displacement at low frequencies shows a frequency dependence that is similar to that in the normal model (approximately constant at 2.5-fold, or
8 dB). Local maxima are present in the range 1,000
to 2,000 Hz and increase with the stiffness of the
middle ear. At frequencies higher than 3,000 Hz, no
differences are evident.
Figure 7B shows the corresponding results for the
displacement of the short process. Again, only minor
differences are present between the normal and otosclerotic models. However, for otosclerosis in com-
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Huber et al, Anterior Mallear Ligament
353
Fig 7. Results of finite element model calculations for displacement amplitudes of A) umbo, B) short process of malleus,
and C) stapes in response to 80 dB SPL acoustic stimulation.
A
B
C
bination with the partially fixed malleus, 5.5-fold differences (15 dB) between the normal and otosclerotic models are present at low frequencies. A maximum 10-fold difference (20 dB) is seen at 1,400 Hz,
where a notch is present. At frequencies higher than
3,000 Hz, only small differences are evident (1.6fold, or 4 dB). The displacement amplitudes are in
general lower than those found at the umbo.
Figure 7C shows the calculated displacements of
the stapes for a fixed sound pressure level at the tympanic membrane. The amplitudes of normal vibration are in good agreement with the results of the TB
study. The differences in stapes vibration between
normal and pathological situations correlate well with
the model simulations in which similar air-bone gaps
are present. Otosclerosis results in attenuation mostly
at low frequencies (30-fold, or 30 dB). Additional
partial fixation of the malleus increases this 3- to 4fold (9 to 12 dB) at frequencies below 1,000 Hz. For
isolated AML fixation, most differences are found at
frequencies below 1,000 Hz and around 1,800 Hz,
ranging from 1.8-fold to 2.5-fold (5 to 8 dB).
tion audiograms.
The results on the motions of the umbo and the
short process from patient measurements, the TB preparations, and the FEM calculations are in good
agreement. No substantial differences are evident in
the displacement of the umbo for the normal, otosclerotic, and partial mallear fixation cases (Figs 4A, 6A,
and 7A). The short process, on the other hand, presents a considerable notch at 1,000 to 2,000 Hz in all
3 measurement methods (Figs 4B, 6B, and 7B). Such
a notch in the vibration amplitude of the short process is therefore a reliable indicator of partial mallear
fixation. Of the 19 patients in the clinical study, 14
presented with normal mallear mobility and 5 with
partial mallear fixation. The notch described was
found in all 5 patients with AML fixation and in 1 of
the 14 patients with normal mallear mobility. The LDI
analysis was therefore in agreement with the observations of the surgeon in 95% (18 of 19) of cases.
Whether partial mallear fixation was wrongly suspected on the basis of LDI in this 1 remaining patient, or whether the mallear fixation was too weak
to be identified by palpation, cannot be answered by
this study. The patient, however, underwent stapedotomy and has a good functional result with an air-bone
gap pure tone average of 10 dB (at 0.5, 1, and 2 kHz).
Although the surgeon sometimes knew of the LDI
results, this is not believed to introduce any bias into
the results, since the clinical assessment was per-
DISCUSSION
By conventional preoperative audiological diagnostics, the difference between isolated stapes fixation and otosclerosis and AML fixation could not be
distinguished, since there was no particular pattern
of tympanograms or preoperative air or bone conduc-
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Huber et al, Anterior Mallear Ligament
Fig 8. Vibration patterns of ossicles in normal ear and in
case of isolated AML fixation.
formed before the TB and FEM investigations, and
the specific LDI patterns for AML fixation were therefore not known at the time of the clinical study. Thus,
there was no preoperative diagnosis by LDI at that
time.
Generally, the results of the 3 methods used in this
study are in good agreement. However, technical differences between the methods lead to some of the
variance seen in the data: 1) the small sample sizes
of 5 and 19 for the TB and clinical studies, respectively; 2) the individual variance in vibration amplitudes; 3) the use of non–angle-corrected displacement data; 4) the use of cadaver TB preparations in
which autolytic tissue changes cannot be excluded;
5) the use of different age groups; 6) the use of an
open (TB and FEM) or closed (clinical study) middle
ear cavity; and 7) the technical difficulty of applying the glue to the AML. (Although microscopic inspection revealed firm fixation in all cases, a fluid
film was found underneath the glue in some preparations at the end of the experiment. Such a fluid film,
even if it is very thin, may allow relative motions in
the nanometer range, and so the results of the TB study
may underestimate the transmission loss.)
It is still unclear why hyalinization and calcification of the AML occur in certain patients with otosclerosis. The notch in vibration amplitude occurring at 1,000 to 2,000 Hz on the short process but
not at the umbo, on the other hand, can be explained
by the 3-dimensional movement patterns of the ossicles. From FEM calculations, it can be seen that in
the normal ear, at frequencies in the range of 1,000
Hz, the mostly rotatory movement of the malleus
changes to a complex movement pattern with a significant translation of the AMP, which moves in a
lateral-medial direction. The short process has thereby a relatively large vibration amplitude. By contrast, in the case of AML fixation, the translational
movement of the malleus is reduced. Since the mal-
354
Fig 9. Stapes displacement amplitude differences in temporal bone preparations and in finite element model calculation.
leus rotates around the classic rotation axis that goes
through the short process of the incus and the AMP,
the lateral mallear process, which is close to the center of the rotation, has a smaller amplitude than in
the normal ear, whereas the umbo motion is virtually unchanged (Fig 8). In cases of additional stapes
fixation, these vibration patterns were not changed;
only the amplitudes were decreased collectively.
The influence of stapes fixation on manubrium motion is most dominant at low frequencies, but appears
surprisingly small. However, the 2 ossicular joints
involved may yield sufficiently to produce almost
normal movements of the malleus. The findings of
routine tympanometry are similar, indicating a tendency toward type As tympanograms, but they do
not allow reliable identification of otosclerosis.9
Assessment of mallear mobility necessitates a high
degree of surgical experience. A modified operative
approach that allows an extended view over the incudomalleal joint and the AML and AMP, however,
makes identification of partial mallear fixation less
difficult. The FEM calculations in this study revealed
that surgical evaluation by palpation on the malleus
neck, represented by a pinpoint force of 0.1 N, leads
to a displacement of the AMP tip of 0.04 mm and
0.003 mm for the normal AML and fixed AML, respectively. The displacement in the normal ear, though
small, can still be identified by an operating microscope, but the displacement in case of a fixed AML
cannot be detected. At the umbo, the displacement
amplitudes are virtually equal. A view over the AML
and AMP is hence required to reliably identify partial mallear fixation.
The malleus and stapes have entirely different frequency response characteristics, because of the complex 3-dimensional nature of sound conduction by
the middle ear. The similarity between the results from
the experimental work and the model calculations
proves that 3-dimensional FEM is an excellent meth-
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Huber et al, Anterior Mallear Ligament
od for simulating the effects of modifying individual
components of the middle ear.
In the study reported here, stapes vibration was
considered to be the effective stimulus to the cochlea.
Differences between the stapes displacements before
and after AML fixation correspond, therefore, to the
prospective air-bone gap in patients with isolated partial mallear fixation. Such an air-bone gap is expected
after operation in patients with otosclerosis and AML
fixation who undergo stapedioplasty with no correction of the partial mallear fixation. Figure 9 gives
these displacement differences in decibels for the TB
preparations and the FEM calculations. The FEM calculations predicted an attenuation of stapes mobility
of −8 to −7 dB at frequencies up to 1,000 Hz, and
−7 to 0 dB at higher frequencies. From the TB experiments, valid data are available from 500 to 4,000
Hz. The results are 2 to 4 dB lower than those from
the FEM calculations, but with a similar frequency
dependence. These values, however, may deviate by
a few decibels from reality, as AML fixations clinically occur in combination with otosclerosis, and patients therefore have a prosthesis replacing the stapes
rather than a normal middle ear after surgery.
We found AML fixation in 26% of the ears with
otosclerosis in this study. This rate confirms the importance of a thorough intraoperative evaluation of
mallear mobility. This figure is in accordance with a
histopathologic study8 and a clinical study on revision stapes surgery.1
A complete bony fixation of the malleus causes a
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15 to 30 dB conductive hearing loss,5-7 but a partial
mallear fixation results in a milder hearing loss. The
air-bone gap due to a partial mallear fixation is approximately 10 dB and is low-frequency–dominant.
We have started a clinical survey to examine whether
a malleostapedotomy yields better functional results
than does incus stapedotomy in primary otosclerosis
combined with AML fixation.
CONCLUSIONS
1. Partial fixation of the malleus can be identified either before operation with LDI or during operation by palpation with observation of the AML
and AMP.
2. Untreated AML and AMP fixation after stapedioplasty produces a persistent air-bone gap of approximately 10 dB at low and middle frequencies.
The confirmation of its relevance in this study is one
step forward in the process of analyzing the causes
of unfavorable results of stapedioplasty.
3. Laser Doppler interferometry is uncommon in
clinical practice, because it is expensive and timeconsuming. The technique may, however, become
of greater practical importance in the future as its
validity in preoperative, intraoperative, and postoperative diagnostics becomes better documented.
4. The study reported here was an example of
combining experimental research with an existing
mathematical middle ear model to address a question with clinical implications.
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