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Cadaveric comparison of canine fossa vs transnasal maxillary sinus access.

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Cadaveric comparison of canine fossa vs transnasal maxillary
sinus access
Brent Alan Feldt, MD1 , Kevin Christopher McMains, MD2 , Erik Kent Weitzel, MD1
Objective: Anatomic limitations complicate complete eradication of debris from the maxillary sinus using an exclusively transnasal (TN) endoscopic technique. Creation of a
canine fossa trephination (CFT) permits a more direct approach than removal via the maxillary ostium.
Methods: Microdebrider eradication of debris completely
filling the maxillary sinus was performed on 5 thawed
fresh-frozen cadaver heads (10 sides) using a TN or CFT
approach. Postdebridement computed tomography (CT)
scanning assessed remaining debris. Additional outcome
measures included time of debris removal, number of different angled blades utilized, and clogging.
Results: A significantly greater amount of debris was le
aer the TN approach compared with CFT (3.88 cm3 vs
2.88 cm3 , p = 0.015). Median blade utilization was significantly higher with the TN approach vs CFT (4 vs 1, p <
0.002). Time for debris eradication with CFT was similar
ndoscopic access to the maxillary sinus through the
nose is a geometric conundrum created by 2 fulcrums,
1 at the nasal vestibule and 1 at the maxillary ostium. These
2 pivot points complicate a surgeon’s attempt to eradicate debris from this sinus by requiring the use of long,
highly-angled instruments. Various pathologies require extensive access to the maxillary antrum. Mycetoma and
chronic rhinosinusitis (CRS) with polyposis have been re-
Department of Otolaryngology Head and Neck Surgery (OtoHNS),
San Antonio Military Medical Center, Lackland AFB, TX; 2 University of
Texas Health Science Center, San Antonio, TX
Correspondence to: Erik K. Weitzel, MD, Dept of OtoHNS, 2200 Bergquist
Drive Ste 1, Lackland AFB, TX 78236; e-mail:
Potential conflict of interest: None provided.
Disclaimer: Images of commercial products in this presentation are not
intended to constitute an endorsement by the U.S. Air Force or any other
Federal Government entity.
This article is a US government work and, as such, is in the public domain in
the United States of America.
Received: 29 July 2010; Revised: 7 September 2010; Accepted: 11 October
DOI: 10.1002/alr.20022
View this article online at
International Forum of Allergy & Rhinology, Vol. 1, No. 3, May/June 2011
regardless of expertise (323.4 vs 272.4 seconds, p = 0.21),
but the TN approach showed a statistical difference in timeto-completion (698.8 vs 438.51 seconds, p = 1.7 × 10−5 ).
Conclusion: Controversy surrounds the appropriate application of CFT due to disease process and approach-related
morbidity. Rhinologists should have numerous well-studied
options at their disposal. This model suggests that maxillary debris removal is accomplished more thoroughly with
fewer microdebrider blades when a CFT approach is emC 2011 ARS-AAOA, LLC.
ployed. Key Words:
endoscopic sinus surgery; canine fossa trephination; debris
removal; microdebrider blades
How to Cite this Article:
Feldt BA, McMains KC, Weitzel EK. Cadaveric comparison
of canine fossa vs transnasal maxillary sinus access. Int Forum Allergy Rhinol, 2011; 1:183–186
peatedly studied, and numerous transnasal (TN) techniques
have been shown to effectively manage this pathology.1–6
However, other pathologies, including allergic fungal sinusitis and tumors, may require extensive exposure and
more thorough mucosal treatment.6–8 It is therefore reasonable for surgeons to have at their disposal a number
of well-studied approaches to maxillary pathology. The
canine fossa trephination (CFT) technique was developed
based on historical experience with the Caldwell Luc approach to create a direct route through the anterior face of
the maxilla while minimizing postoperative morbidity.9–12
Singhal et al.9 document that 40% of patients undergoing CFT develop postoperative symptoms including facial
tingling/numbness/pain, cheek pain/swelling, teeth numbness, and gingival problems. The immediate severity of
these complaints can be quite high, but resolve quickly
and do not require treatment. By 3 months after surgery,
only 5% of patients have ongoing minimal symptoms,
which in this large series included 2 patients with very mild
Complete clearance of maxillary sinus pathology using a
fully TN approach has several drawbacks. Primarily, this
includes the potential for inadequate pathology removal
Feldt et al.
due to areas unreachable with a microdebrider, but may
also include the added expense of multiple microdebrider
blades and increased difficulty of the procedure due to unfavorable ergonomics. It is the goal of this study to determine
if the CFT approach has an advantage with these issues
relative to the TN approach.
Materials and methods
Exempt institutional review board (IRB) status was received
for this cadaveric study from the Wilford Hall Medical Center IRB. Ten sides of 5 thawed fresh-frozen cadaver heads
were repeatedly used to conduct this experiment. The nasal
septum was assessed in all specimens and did not present an
impediment to full endoscopic view of the widened maxillary ostium in any specimen. Crush artifact of the soft tissue of the anterior septum (evident in Fig. 1) affected only
the nasal vestibule but did not affect surgical access for
the study. Preparation of cadavers included bilateral wide
maxillary antrostomy (maximal possible anterior-posterior
and superior-inferior dissection) and a 5-mm CFT created
at the intersection of the midpupillary line and the floor of
the nose utilizing a maxillary trephination kit (Medtronic,
Jacksonville, FL).7 The time for this preparatory work was
not included in the time outcome measure.
A jelly-like material (holds structure after partial removal) was required for this study that could be injected
into the maxillary sinus through the CFT to analyze the
extent of maxillary debridement. Ideally, we desired this
substance to have basic material properties similar to typical allergic fungal sinusitis (AFS) debris, including heterogeneity of particle size, density, stickiness, viscoelasticity,
and shear strength. Since no peer-reviewed literature exists
identifying a sinus mucin or allergic fungal sinusitis analog, 10 materials were created using various combinations
of smooth and crunchy peanut butter, cooking oil, lard,
minced cat food, and minced dog food. Ten staff otolaryngologists familiar with sinus mucin were then asked to rank
each material regarding its similarity to sinus mucin. The
most similar material was rated as Science Diet C Adult
Gourmet Beef Entrée minced cat food.
Each maxillary sinus then was completely filled with cat
food from a 60-cc Tumi syringe through the CFT. Under
endoscopic guidance, the maxillary sinus was filled to overflowing (approximately 15–20 mL, depending on the individual sinus). The maxillary sinus debris was then removed
as extensively as possible with a series of microdebrider
blades, progressively utilizing the 0-degree then 40-degree,
90-degree, and 120-degree blades. The surgeon stopped
the procedure when no more sinus debris could be removed using any available blade. Each maxillary sinus underwent both a TN and trans-CFT microdebridement by
the same surgeon to permit paired analysis. Surgical outcomes recorded included the type and number of blades
required to get the most complete debris removal, time to
completion, and residual volume of debris in the sinus at
termination. The study was repeated for a resident and a
FIGURE 1. CT scans were performed after debris removal via (A) transnasal
and (B) CFT approaches. Note that residual debris is always located in an
anterior position and TN removal left more debris (dashed arrow) than the
CFT approach (solid arrow).
staff rhinologist to note the effects of expertise on the outcome measures. Clogging of blades was recorded during
the staff rhinologist trials.
Cadavers underwent computed tomography (CT) scans
at 2 different time points (after preparatory dissection and
after endoscopic debridement by the trainee surgeon). The
amount of debris left after microdebridement was calculated with numerical integration from postdissection multiplanar reconstructions. Area of debris was measured on
coronal CT scans and then multiplied by slice thickness
(2.5 mm). This process was repeated on a slice-by-slice basis until all debris had been identified. The resulting sum
is a reasonable approximation of total volume. Paired Student t test was used to compare time and volume outcomes,
and the Mann-Whitney U test was used to compare blade
International Forum of Allergy & Rhinology, Vol. 1, No. 3, May/June 2011
CFT vs transnasal approach
Amount of debris removed
On average, 3.88 cm3 of cat food was left in a superior/
anterior location in the sinus after a purely TN attempt
at removal utilizing a full range of microdebrider blades
(Fig. 1). When the CFT approach was performed, 2.88
cm3 of cat food remained. This represents a significant
reduction in retained debris at the end of surgery (p =
0.015). Representative CT scans performed after removal
emphasize the improved outcome with the CFT approach
(Fig. 1).
Number of blades used
The surgeon’s best attempt at complete eradication of debris from the sinus using a TN approach required all
4 blades, as opposed to the CFT approach, which only
required the 0-degree blade in all cases (p < 0.002).
Operative time for maximal removal of debris
There was no statistical difference between times for the
trainee and staff surgeon for the CFT approach (323.4 vs
272.4, p = 0.21), but the TN approach showed a statistical
difference in time to completion (698.8 vs 438.51, p =
1.7 × 10−5 ) (Fig. 2).
Clogging of microdebrider blades
It is not possible to adequately compare clogging rates of
the different angled blades relative to each other since the
volume removed was not standardized nor was the time
of blade utilization standardized for each procedure. The
blade used to remove the most debris was the straight microdebrider blade for both approaches. The straight microdebrider blade clogged 23 times during 20 maxillary sinus surgeries (1.15 clogs/case). The blade clogged 10 times
on the TN approach vs 13 times on the canine fossa ap-
FIGURE 2. Time comparison for as-complete-as-possible debris eradication relative to surgeon experience. Time difference was significantly faster
for expert rhinologist only with transnasal removal, suggesting a faster learning curve with the canine fossa approach.
International Forum of Allergy & Rhinology, Vol. 1, No. 3, May/June 2011
proach (p = 0.63). For angled blades, the 40-degree blade
clogged once in 10 uses, the 90-degree blade clogged twice,
and the 120-degree blade did not clog in 10 uses.
This study is the first to attempt a statistically paired comparison quantifying microdebrider access to the maxillary
sinus for the TN and CFT approaches. Our findings suggest that access is improved with a CFT. Although both
approaches appear to leave a small amount of material
after attempted eradication, the CFT approach averaged
1 cm3 greater debris removal than the TN approach. There
is also a clear advantage of the CFT approach for decreasing blade utilization. The CFT approach utilizes only the
straight microdebrider blade, while a series of 4 blades of
varying angles were unable to accomplish the same amount
of debris removal transnasally. Fewer blades can be utilized
with the TN approach by selectively utilizing only those required for specific locations of debris, but this number will
inevitably be greater than the 1 required for the CFT approach. These data also suggest that TN debris removal
is significantly faster in expert hands relative to a trainee
but this statistical difference is eliminated with a CFT approach. The lack of a significant difference with CFT operative times over a combined 10 surgeries suggests that
proficiency is achieved within a few cases.
Arguably, most rhinologists employ other techniques in
the removal of maxillary sinus debris than just microdebriders, which may call the relevance of our findings into
question. Numerous publications describe successful management of mycetoma with a gauze-assisted technique
or thorough irrigation and tout excellent mucosal
preservation.2,3 However, current research suggests that
in the setting of eosinophilic mucus chronic rhinosinusitis
(EMCRS), the mucosa itself is part of the pathophysiology
and may also require partial removal with a microdebrider
for optimal outcomes. This becomes evident when examining studies that have specifically looked at CFT in the setting
of AFS. Sathananthar et al.7 provides the best published
quantification of this effect when reporting a retrospective comparison of a diverse group of patients with severe
maxillary disease including a large proportion with AFS,
and found that trans-CFT microdebridement improved 20month magnetic resonance imaging (MRI)-defined maxillary opacification (62% vs 12% clear, p < 0.001) and
chronic sinusitis symptom scores. Unfortunately, this study
includes mismatched control-to-study pathology (controls
were predominantly CRS vs the study group which included
mostly EMCRS subgroups). However, the mismatch should
favor the TN approach group, which clearly performed
worse than the CFT group. A well-performed study commonly referenced to dispute Sathananthar et al.’s7 findings
showed similar long-term outcomes in patients randomized
to treatment by either CFT or TN approach. Unfortunately,
the study’s methods specifically exclude patients with
Feldt et al.
fungal pathology, thus their results are then only applicable
to patients with CRS + polyps, but not AFS,6 which creates
confusion in its overall relevance to the poor-prognostic
EMCRS subtypes.
When trying to explain why partial thickness polypoid
mucosa removal down to bleeding basement membrane (a
typical adjunct to the CFT microdebrider approach) might
improve the surgical outcomes of EMCRS, we have to reflect on our knowledge of AFS. Kupferberg et al.’s13 seminal
presentation of poor operative outcomes initially relegated
sinus surgery to a temporizing measure with AFS. However,
this dogma was recently contested with the report of improved outcomes with aggressive surgical management of
the mucosa.8 Kupferberg’s et al.’s13 original work showed
recurrence in 11 of 12 AFS patients by 14.5 months when
not maintained on oral steroids, whereas Seiberling et al.’s8
more aggressive partial thickness mucosa removal through
a CFT led to only 9 of 19 AFS recurrences without the need
for long-term oral glucocorticoids.
The rationale for these improved outcomes with more
radical surgery is likely related to more aggressive management of the mucosa itself rather than relying on the tenets of
routine functional endoscopic sinus surgery (FESS), which
include ostial enlargement, mucosal preservation, and complete debris removal. Extrapolating upon Pant et al.’s14
findings, recurrence of polyposis after FESS in EMCRS is
likely partially due to the incomplete removal of nests of
submucosal primed CD8 + T cells. These retained follicles
of lymphocytes, once re-exposed to fungal antigens, reignite
the whole inflammatory cascade, leading to a rapid return
of disease. Thus, partial thickness mucosal excision utilizing a microdebrider may be a beneficial adjunct to FESS
in EMCRS polypoid tissue. Our study shows that the CFT
aids in a more complete access to the maxillary antrum and
with the aforementioned logic adds explanation as to why
a CFT approach for a dominant microdebrider treatment
of diseased tissue may yield better results with EMCRS.
The similarity of the material we used to fill the maxillary
sinus relative to actual AFS mucin is trivial. Since our main
goal was meant to evaluate the extent of access with microdebriders to the maxillary antrum, the only important
material property required was that the substance maintain
its shape after partial removal so that the substance did not
slide down the sinus after dependent debris was removed.
The minced cat food definitely has this property and was
successful in this regard. As an analog for sinus mucus,
any comparisons at this point are preliminary. Ten staff
otolaryngologists felt that the material had similar properties to AFS based on careful manual inspection, but further
material property laboratory analysis must be performed.
These studies are currently underway.
Microdebrider access to the maxillary antrum is improved
with a CFT approach relative to a purely TN approach.
Fewer microdebrider blades are used when the CFT approach is employed. In a training setting, the CFT approach
appears to have a faster learning curve than TN maxillary
sinus debridement.
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International Forum of Allergy & Rhinology, Vol. 1, No. 3, May/June 2011
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fossa, maxillary, access, comparison, canine, transnasal, sinus, cadaveric
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