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Acta Oto-Laryngologica
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Canal wall reconstruction and mastoid obliteration in
canal wall down tympanomastoidectomized patients
Won-Sang Leea, Sung Huhn Kima, Won-Sang Leea, Sung Huhn Kima, In Seok Moona & Hyung
Kwon Byeona
a Department of Otorhinolaryngology – Head & Neck Surgery, Yonsei University College of
Medicine, Seoul, Korea
Published online: 27 Aug 2009.
To cite this article: Won-Sang Lee, Sung Huhn Kim, Won-Sang Lee, Sung Huhn Kim, In Seok Moon & Hyung Kwon Byeon
(2009) Canal wall reconstruction and mastoid obliteration in canal wall down tympanomastoidectomized patients, Acta Oto-
Laryngologica, 129:9, 955-961
To link to this article: http://dx.doi.org/10.1080/00016480802510178
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ORIGINAL ARTICLE
Canal wall reconstruction and mastoid obliteration in canal wall down
tympanomastoidectomized patients
WON-SANG LEE*, SUNG HUHN KIM*, IN SEOK MOON & HYUNG KWON BYEON
Department of Otorhinolaryngology Head & Neck Surgery, Yonsei University College of Medicine, Seoul, Korea
Abstract
Conclusion: Posterior canal reconstruction using autogenous bone pate and mastoid obliteration with allogenous cancellous
bone chips (ACBCs) is a useful method to eliminate cavity problems after canal wall down tympanomastoidectomy
(CWDT). It is also an appropriate method to obtain adequate middle ear space for hearing gain and to apply hearing aids
for patients with poor eustachian tube function after surgery. Objective: This study was performed to suggest a new
technique for posterior canal reconstruction and mastoid obliteration and to evaluate the outcome of the surgery. Patients
and methods: The entire posterior canal was reconstructed with autogenous bone pate, and the new isolated mastoid cavity
was obliterated with ACBCs in patients who had undergone CWDT and suffered from cavity problems. Outcomes were
measured by external auditory canal shape, condition of the neotympanum, hearing outcome, improvement of cavity
problems, and surgical complications. Results: In 90.9%, the reconstructed canal wall maintained a cylindrical shape. The
drum healed without perforation/retraction in 90.9%. The average airbone gap value was 34.5 dB hearing level (HL)
before the staged operation and 17.8 dB HL after the staged operation; 95.5% had no more cavity problems. Minor
postauricular wound infection was the most common complication (13.6%).
Keywords: Bone pate, ear canal, middle ear, hearing
Introduction
Canal wall down tympanomastoidectomy (CWDT)
has been consistently used to completely eradicate
advanced chronic otitis media or cholesteatoma.
Despite meticulous surgical technique, many patients
who undergo CWDT suffer from cavity problems,
such as continuous draining ear, accumulation of
keratin debris, frequent vertigo attacks following
temperature or pressure changes, and difficulty in
fitting a hearing aid [1,2]. In addition, the final
hearing gain after staged ossiculoplasty in patients
who have undergone CWDT is usually 510 dB worse
than those who underwent canal wall up tympano-
mastoidectomy. This is due to the fact that the middle
ear cavity is usually shallower after CWDT and
therefore inadequate for effective sound transmission
[3,4].
To solve these problems, several mastoid oblitera-
tion techniques with or without posterior canal wall
reconstruction using several kinds of muscle flap
[1,5], cortical bone pate [57], allogenous/autoge-
nous bone chips [5,6], cartilage [7,8], and hydro-
xyapatite [7,9] have been suggested. However, these
materials have not proven entirely satisfactory, as they
are occasionally gradually reabsorbed, leading to the
redevelopment of cavities over 35 years [10]. There
have also been reports of extrusion in some cases
necessitating continuous treatment. Furthermore, it
is difficult to secure the middle ear cavity for effective
sound transmission and to apply hearing aids if the
mastoid cavity was only partially obliterated without
reconstruction of the entire posterior canal wall.
Previous reports have mostly described reconstruc-
tion after a first operation, not revised cases. The
problem in revised cases is that it is hard to obtain
sufficient amounts of the autogenous materials for
reconstruction.
Therefore, we designed a technical modification
and used new materials to address cavity problems
Correspondence: Won-Sang Lee, Department of Otorhinolaryngology, Yonsei University College of Medicine, 134 Sinchon-dong, Seodaemun-gu, Seoul
120-752, Korea. Tel: 82 2 2228 3606. Fax: 82 2 393 0580. E-mail: wsleemd@yuhs.ac
*These authors contributed equally to this study.
Acta Oto-Laryngologica, 2009; 129: 955961
(Received 13 August 2008; accepted 28 September 2008)
ISSN 0001-6489 print/ISSN 1651-2251 online #2009 Informa UK Ltd. (Informa Healthcare, Taylor & Francis As)
DOI: 10.1080/00016480802510178
Downloaded by [Yonsei University] at 23:43 04 September 2015
and secure the middle ear space for patients who had
undergone CWDT with subsequent cavity problems,
and we have used it for years. The current report
describes the technique that we have been using and
the anatomic and functional results.
Patients and methods
Selection of cases and outcome measurement
In all, 22 patients who had undergone CWDT and
suffered from cavity problems or residual/recurrent
infections were enrolled in this study. 8 patients
were male and 14 were female, and their average
age was 40 years (range 2957 years). They under-
went posterior canal wall reconstruction at Yonsei
University Severance Hospital between January
2004 and June 2007. The mean interval from
primary CWDT to posterior canal wall reconstruc-
tion was 20 years (range 244 years). The average
postoperative follow-up period was 33 months,
ranging from 12 to 54 months. Anatomic results
were assessed on the basis of the shape and the
volume of the ear canal and condition of the
neotympanum. The external auditory canal and
tympanic membrane were initially examined 2
weeks after the operation using a surgical micro-
scope. The patients had a 1-month interval follow-
up for 2 months, a 6-month interval follow-up for 1
year, and 1-year interval follow-up after that time.
Postoperative ear canal volume was measured at
most recent follow-up date by filling the ear canal
with saline solution. A staged operation for hearing
gain was performed in 18 patients with healthy
drums and well-aerated middle ear cavities around
12 months after the canal reconstruction. Partial
ossicular replacement prostheses were used in 6
cases, and total ossicular replacement prostheses
(TORPs) in the other 12. A Polycel†ossicular
prosthesis (Medtronic Xomed, Jacksonville, FL,
USA) was used in all cases and tragal cartilage
cap (5 mm diameter and 0.5 mm thickness)
was interposed between the drum and the prosthe-
sis. Before the staged operation, high-resolution
computed tomography of temporal bone (TBCT)
was performed to evaluate possible residual disease
and to detect the reconstructed posterior canal wall
and neotympanum. Functional outcomes were
evaluated by comparing preoperative and post-
operative airbone gaps, 12 months after the staged
operation. Audiometric analysis was performed
according to the 1995 American Academy of
Otolaryngology-Head and Neck Surgery (AAO-
HNS) guidelines [11], averaging the hearing thresh-
old at four frequencies (500, 1000, 2000, and
3000 Hz). Functional results were evaluated on
the basis of the airbone gap at four frequencies
(500, 1000, 2000, 3000 Hz), 12 months after the
staged operation. The improvement of cavity pro-
blems and postoperative complications after poster-
ior canal wall reconstruction were investigated at
the most recent follow-up.
Surgical technique
All cases were revision surgery. First, we elevated
the conventional postauricular skin flap and mus-
culoperiosteal flap. Musculoperiosteal flap was
usually thickened with soft tissues in the mastoid
bowl. Soft tissue was trimmed off from the flap and
the remaining musculoperiosteal flap was used to
cover the bone chips after surgery. Then, we very
carefully elevated the posterior meatal skin flap,
which covers the mastoid bowl, because it is prone
to tear. We made an incision posterior to the facial
ridge to expose the tympanic membrane, and
elevated it to enter the middle ear space. Healthy
cortical bone pate was collected using a separate
suction line and glass bottle. It was filtered, mixed,
and soaked with a povidone-iodine solution for an
hour and then dried. We performed revision
complete mastoidectomy and removed all patholo-
gic lesions within the mastoid and middle ear cavity
(Figure 1A). In nearly all cases (95%), meatoplasty
had been performed previously; therefore, we
trimmed the elevated skin flap and designed it to
cover the reconstructed canal wall. The pre-col-
lected autogenous bone pate was applied to the
epitympanic space posterior to the cochleariform
process and superior to the tympanic segment of
the facial nerve (Figure 1B). Next, we made an
entire posterior canal wall with pre-collected auto-
genous bone pate above the facial ridge, maintain-
ing the height at the level of the mastoid bone outer
cortex (Figure 1C, Figure 2A). The bone pate was
applied in a broad-based, narrow top fashion above
the facial ridge for stability. We inserted a thin
silastic sheet into the middle ear space and per-
formed tympanoplasty with temporalis fascia,
which entirely covered the new canal wall (Figure
2B). The isolated mastoid cavity was obliterated
with 35 mm sized allogenous cancellous bone
chips (ACBCs; ReadiGRAFT†, Lifenet, Virginia
Beach, VA, USA) (Figure 2C). For the last step, we
repositioned the appropriately designed healthy skin
flap and finished by packing the external auditory
canal with Gelfoam (Upjohn Co., Kalamazoo, MI,
USA).
956 W.-S. Lee et al.
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Results
Anatomic results
In a total of 20 of 22 patients (90.9%), the external
auditory canal wall healed well and maintained its
cylindrical shape (Figure 3). Of the two remaining
patients, in one case, the reconstructed posterior
canal wall totally collapsed due to ACBC infection
and the resultant autogenous bone pate infection,
and revision CWDT was consequently performed
(Table I). In the other case, the reconstructed
posterior wall was exposed and partially reabsorbed,
which eventually resulted in posterior wall hollow-
ing. The mean volume of external auditory canal of
20 patients whose canals were cylindrical was 0.879
0.05 ml (mean9SE). Among them, 18 patients
(90%) showed a volume of B0.9 ml but for two
(10%) who showed 1.1 ml and 1.2 ml, respectively.
The tympanic membrane showed good healing in 20
cases (90.9%) (Figure 3). Tympanic membrane
adhesion developed in two cases. The average time
required for complete epithelialization of the fascial
surface and external auditory canal wall was 30.7
days (range 784 days).
At the time of the staged operation, most patients
(n15 of 18, 83.3%) showed normalized middle ear
mucosa and adequate middle ear space. Three cases,
however, showed edematous and hypertrophic
changes in the middle ear mucosa with a shallow
cavity at the time of the staged operation. All 18
cases who underwent staged operation showed a
firm posterior canal wall, and new bone formation in
the posterior canal area.
Functional results
Of the 18 cases that underwent staged operation and
follow-up pure tone audiometry, 13 (72.2%) showed
an improved airbone gap value of10 dB hearing
level (HL) (Figure 4). Stratified hearing results are
as follows (Table II); seven patients had a post-
operative airbone gap value ofB10 dB HL, and five
patients had a postoperative airbone gap value that
fell between 10 and 20 dB HL. A postoperative air
bone gap value20 dB HL was reported in the
remaining six patients. The average airbone gap
value before the staged operation was 35.4 dB HL
(range 2048.8) and 17.8 dB HL (range 1.541.5)
after the staged operation.
Improvement of cavity problems
Before the posterior canal wall reconstruction sur-
gery, the most common cavity problem was contin-
uous ear drainage (n13), followed by
accumulation of keratin debris (n9), and dizziness
with pressure or temperature changes (n2).
Twenty patients (90.9%) did not complain of any
problems after the reconstruction. One patient,
whose canal was totally collapsed, required regular
ear canal maintenance cleaning.
Surgical complications
Minor postauricular wound infection (n3, 13.6%)
was the most common surgical complication.
ACBCs were infected in two patients and conse-
quently mastoidskin fistulas formed. In one case,
only careful dressing with administration of anti-
biotics was necessary, and while postauricular skin
depression was seen, the posterior canal wall re-
mained intact. The other had a bone pate infection
and resulted in a total loss of the new canal wall and
mastoid cavity. There was no external auditory canal
wall stenosis (Table III).
Discussion
Usually, the posterior canal wall is reconstructed by
obliterating the mastoid cavity with various materials
Figure 1. Schematic drawings of the procedure for posterior canal wall reconstruction using autogenous bone pate. Complete revision
mastoidectomy is performed (A). Autogenous bone pate is applied to the epitympanic space posterior to the cochleariform process and
superior to the tympanic segment of the facial nerve (B). Next, the bone pate is applied in a broad-based, narrow top fashion above the facial
ridge for stability, maintaining the height at the level of the mastoid bone outer cortex (C).
Posterior canal wall reconstruction and mastoid obliteration 957
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after CWDT as a one-stage procedure. However,
there have been few reports [6,12,13] about
restoring the ear canal during revision surgery in
patients who previously underwent CWDT. Restora-
tion of the ear canal in revision surgery is more
difficult because it is hard to obtain sufficient
amounts of autogenous materials for reconstruction
and obliteration.
In CWDT, bone pate was used for canal wall
reconstruction in some studies [12,13]. Grafted
autogenous bone pate was reported to form new
bone over time, thus maintaining its shape [13]. We
have also used autogenous bone pate for epitympa-
nic obliteration to prevent retraction pocket for years
and found that it was firm and well maintained [14].
In addition, autogenous bone pate is more biocom-
patible than artificial materials [10] and it is not so
difficult to get a sufficient amount of autogenous
bone pate from the cortical bones around the
mastoid bowl even in the revision case if we use it
only for canal wall reconstruction, not for mastoid
obliteration. Thus, we chose autogenous bone pate
as a material for posterior canal wall reconstruction
and have used it for years.
To prevent the recurrence of infection or choles-
teatoma, bone pate used for canal wall reconstruc-
tion should be obtained only from normal cortical
bone and pathologic lesions such as diseased mu-
cosa, granulation or cholesteatoma in the mastoid
bowl and the middle ear must be completely
removed before reconstruction and obliteration.
We have carefully followed up the patients after the
surgery to detect possible residual disease or recur-
rence and, so far, after an average of 33 months, no
residual disease or cholesteatoma was found on
postoperative follow-up TBCT or surgical examina-
tions during the staged operation.
The reconstructed canal wall should be comple-
tely covered by healthy meatal skin flap to vitalize
and protect the new posterior wall from infection
and reabsorption [13]. We trimmed away undesired
skin flaps and preserved only healthy skin, which
could completely cover the reconstructed wall. In
most of our cases, the posterior wall bone pate was
not reabsorbed and was well vitalized, possibly
owing to adequate coverage of the reconstructed
posterior wall with healthy skin. As a result, the
restored ear canal remained cylindrical in most cases
(90.9%) and most patients (90.9%) did not
complain of any cavity problems after the surgery.
In contrast, hollowing of the posterior wall devel-
oped in one patient whose canal wall had not been
completely covered with the skin flap, which re-
inforces the importance of complete coverage of the
reconstructed posterior canal wall with the skin flap.
To prevent the development of postauricular skin
depression and to prevent the collapse of recon-
structed posterior canal wall after surgery the new
mastoid cavity should be obliterated. In some
Figure 2. Intraoperative view of the entire posterior canal wall
reconstruction procedure with autogenous bone pate and mastoid
obliteration with allogenous cancellous bone chips (AC). The
entire posterior canal wall is reconstructed with autogenous bone
pate above the facial canal to the posterior part of the epitympa-
num (A). The ear drum is reconstructed with temporalis fascia in
the usual manner, covering the new posterior canal wall completely
(B). The newly formed mastoid cavity is obliterated with allogen-
ous cancellous bone chips (C). *Reconstructed posterior wall;
arrow, grafted temporalis fascia; arrowhead, allogenous cancellous
bone chips; S, sigmoid sinus; DP, middle fossa dural plate.
958 W.-S. Lee et al.
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studies, autogenous bone pate [13] and autogenous
cortical bone chips [5] were used for this purpose.
These materials are biocompatible and form new
bone, but are hard to obtain in sufficient amounts
for obliteration in revision surgery. Cartilage or
muscle flaps are not entirely satisfactory, because
they are occasionally reabsorbed, leading to the
redevelopment of cavities [7]. Therefore, the need
for materials that are both durable and easy to obtain
was increasing.
Kuner and Hendrich [15] reported that allogen-
ous cancellous bone grafts in fractures of long
tubular bones and acetabulum defects are effective
and not significantly different to autogenous cancel-
lous bone. Kubler et al. [16] and Endres et al. [17]
also reported favorable results with allogenous
cancellous bone grafts. Therefore, we chose to use
ACBCs to obliterate the mastoid cavity and as a
result, in most cases ACBCs that filled the mastoid
cavity were not reabsorbed and were well vitalized.
The average period for complete epithelial cover-
age of fascial surface, external auditory canal skin
and drum after the surgery was shorter than that for
CWDT. CWDT generally requires 23 months for
complete healing [1], but in our cases, the average
healing period was 30.7 days where most of them
achieved healing in B3 weeks. In a report [13]
describing mastoid obliteration using autogenous
bone pate in patients who had undergone CWDT,
epithelial coverage of the fascial surface occurred
between 3 and 6 weeks after surgery, and solidifica-
tion of bone pate occurred over 34 weeks, which is
consistent with our cases. This report also indicated
that vascularization, osteogenesis, osteoinduction,
and radiographic calcification of the pate occurred
over 39 months. In our series, we found that the
reconstructed posterior wall was calcified on the
TBCT obtained 1218 months after surgery.
The resultant ear canal remained cylindrical in
most cases (90.9%) and in those cases the average
postoperative volume of external auditory canal was
about 0.9 ml, which was a little larger than that of
normal canal volume but much smaller than that of
CWDT [18]. As a result, most patients (90.9%) did
Figure 3. Postoperative findings after posterior wall reconstruction and mastoid obliteration. Photograph of drum and external auditory
taken 18 months after the surgery (A). The external auditor y canal maintained its cylindrical shape. Computed tomographic scan taken 18
months after surgery (B, C). The bone pate and allogenous cancellous bone chips (white arrow) used for the posterior canal wall
reconstruction and obliteration are well maintained without any absorption. *Reconstructed posterior wall.
Table I. Anatomic results after posterior canal wall reconstruction
with autogenous bone pate and mastoid obliteration with
allogenous cancellous bone chips (n22).
Drum and auditory canal No. of cases (%)
Drum Well-healed 20 (90.9)
Perforation 0 (0)
Adhesion 2 (9.1)
EAC Cylindrical 20 (90.9)
Hollowing 1 (4.5)
Total loss 1 (4.5)
EAC, external auditory canal.
Figure 4. Hearing results after staged ossiculoplasty in patients
who underwent posterior canal wall reconstruction and mastoid
obliteration (n18). Improvement in the airbone gap by10 dB
HL was reported postoperatively in a total of 13 of 18 patients.
Posterior canal wall reconstruction and mastoid obliteration 959
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not complain of any cavity problems after the
surgery.
The tympanic membrane was intact and the
middle ear cavity well maintained in most cases
(n20, 90.9%). Tympanic membrane adhesion
developed in two cases where the eustachian tube
failed to ventilate the middle ear cavity; however, the
middle ear cavity was completely separated from the
mastoid cavity, so a retraction pocket did not
develop. In those adhesion cases, hearing gain was
achieved because hearing aids could be applied with
the reconstructed posterior canal wall.
Hearing improvement is one of the main goals of
this technique. Eighteen patients underwent a staged
operation for hearing gain. Four patients were not
able to undergo staged ossiculoplasty because of
drum adhesion, total loss of restored ear canal, or
severe sensorineural hearing loss. An airbone gap of
20 dB was reported in 67% of patients after staged
ossiculoplasty. The hearing outcomes were favorable
compared with other studies in which mastoid
obliteration and/or posterior wall reconstruction
was performed [9,13,19,20]. The reconstructed
posterior canal wall seemed to provide sufficient
middle ear space in most cases, enabling adequate
sound energy transfer for hearing gain after the
staged operation. Six cases showed an airbone gap
of20 dB, five of which used TORP in the staged
operation. The instability of the prosthesis could
have resulted in a large airbone gap. The surgery
still had benefits for those patients whose post-
operative airbone gap values were20 dB, as they
could use a hearing aid because their ear canal was
restored into a cylindrical shape, which was advan-
tageous for fitting a hearing aid. A restored ear canal
is beneficial not only to the patients with adhered
drums but also to those who did not fully regain
auditory function after staged ossiculoplasty.
The main complication encountered with the
surgery is minor postauricular wound infection
(n3, 13.6%). All the minor infections resolved
with intravenous antibiotics and careful wound
dressings. In two patients, ACBCs were infected
and, consequently, fistulas formed. In one patient,
the fistula was closed and healed with careful
dressing and antibiotics after 1 month. However,
the other patient had a bone pate infection and
suffered a total loss of the reconstructed canal wall.
That patient had previously suffered from recurrent
methicillin-resistant Staphylococcus aureus (MRSA)
infections and had undergone five revision surgeries.
The MRSA infection had been controlled with
vancomycin before canal wall reconstruction sur-
gery, but it seemed to have recurred as the micro-
organism cultured from the discharge of fistula was
also revealed to be MRSA. We had to remove all the
materials used in canal wall reconstruction and
obliteration, and perform revision CWDT.
Conclusions
Posterior canal wall reconstruction using autogenous
bone pate and mastoid obliteration with ACBCs is a
Table II. Hearing results after staged ossiculoplasty in patients who underwent posterior canal wall reconstruction and mastoid obliteration
(n18).
Preoperative Postoperative
Airbone gap (dB HL) No. of cases (%)
Mean air conduction
of eachgroup (dB HL) No. of cases (%)
Mean air conduction
of each group (dB HL)
Group A (010) 0 (0) - 7 (38.9) 22.392.2
Group B (1020) 2 (11) 37.590 5 (27.8) 42.097.8
Group C (20) 16 (89) 59.493.3 6 (33.3) 59.294.0
Mean airbone
gap/mean air
conduction level
(dB HL)
35.492.2/56.993.4 17.892.9/38.794.4
Hearing level is described as mean9SE.
Table III. Surgical complications of the new posterior canal wall
reconstruction and mastoid obliteration technique (n22).
Complications No of cases (%)
Postauricular skin infection 3 (13.6)
ACBC infection* 2 (9.1)
Fistula (mastoid cavityskin) 2
$
(9.1)
Bone pate infection 1
%
(4.5)
Postauricular skin depression 1
§
(4.5)
External auditory wall stenosis 0 (0)
*ACBC, allogenous cancellous bone chips, ACBC infection
caused
$
fistula. One of them developed
%
bone pate infection,
which caused total posterior wall collapse and the other developed
only
§
postauricular skin depression after careful dressing.
960 W.-S. Lee et al.
Downloaded by [Yonsei University] at 23:43 04 September 2015
useful method to eliminate cavity problems that
develop after CWDT. This is also an appropriate
method to obtain sufficient middle ear space for
subsequent staged operations and to apply hearing
aids for patients with poor eustachian tube function
after surgery.
Declaration of interest: The authors report no
conflicts of interest. The authors alone are respon-
sible for the content and writing of the paper.
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