Full text of DOI:10.1097/00005537-200202000-00029

The Laryngoscope
Lippincott Williams & Wilkins, Inc., Philadelphia
© 2002 The American Laryngological,
Rhinological and Otological Society, Inc.
The Mechanical Stability Under Load of
Tracheal Anastomoses After Various Phases
In Vivo
Matthias Behrend, MD; Eva Kluge; Wolfgang Schu¨ttler, DiplIng; Ju¨rgen Klempnauer, MD, PhD
Objective: The objective of our study was to post-
operatively examine the mechanical stability under
load of tracheal anastomoses over different periods in
time and to compare these with native tracheae.
Study Design: A randomized experimental study on
animals. Method: We performed tracheal anastomoses
on sheep with three different suturing techniques
and different resection lengths (3, 6, and 9 cm): These
anastomoses were subjected to a breaking test at dif-
ferent intervals in vivo (1, 2, 4, 8, and 24 wk) and
compared with the tracheae of healthy sheep. Results:
After 1 week in vivo, the anastomosis itself tore off
from the remaining trachea under tension, regardless
of the suturing technique used and the length of re-
section. With all animals that survived for a longer
period, the trachea broke a greater distance away
from the anastomosis. The necessary breaking forces
were only minimally lower than those required for
breaking healthy tracheae and the difference is sta-
tistically insignificant. When all operated tracheae
are combined and the forces compared with native
tracheae, this reveals that the operated tracheae are
significantly more stable (P ؍ .015) and present a
lower longitudinal elasticity (P ؍ .004). Conclusion:
During the first postoperative days, the stability un-
der load of tracheal anastomoses is slightly lower
than that of healthy trachea. This difference is, how-
ever, far from those values that can be measured in-
traoperatively on tracheal anastomoses. Thus, sup-
plementary measures for the mechanical protection
against suture line separation do not seem necessary.
Key Words: Surgical procedures, operative, anasto-
sutures,1 prolonged intubation with or without inflated
cuffs,2 traction sutures,3 and mini tracheotomy.4 A num-
ber of these measures burden the patient heavily or even
constitute additional risks. Thus, it is even more surpris-
ing to learn that scarcely any studies exist concerning the
mechanical stability under load of tracheal anastomoses.
We have recently presented a method of examining the
breaking strength of tracheal anastomoses5 and analyzed
various suturing techniques in vitro and in vivo.6 During
the course of these studies, it became apparent that in
vitro continuous sutures possess superior mechanical
characteristics. These results were, however, not con-
firmed in vivo. We now report on the comparison of the
breaking strength of healthy tracheae with anastomosed
tracheae. The anastomoses were performed with different
operative techniques and partially constructed under ten-
sion after long-sectioned resections.
MATERIALS AND METHODS
Preparation of Native Tracheae
Twenty-four tracheae from freshly slaughtered German
sheep weighing 50 to 70 kg were collected from the local slaugh-
terhouse within 1 hour of slaughter. The tracheae were removed
from the larynx to the tracheal bifurcation and stored until fur-
ther use in a humid environment using a Ringer’s lactate solu-
tion. They were carefully freed of remaining tissue and the center
portion shortened to a standard length of 120 mm. The transverse
and longitudinal diameters were caudally and cranially mea-
sured with a slide gauge.
moses,
trachea,
suture
techniques,
suture
Animal Preparation
breakdown.
All operations were performed on 9-month-old female sheep
weighing 40 to 50 kg. The study was approved by the Animal Care
and Use Committee at the Medical School Hannover and the local
district government (Ts-No. 509i-42502–00/288). The sheep were
absolutely healthy, as a physical examination confirmed. Food
was withheld for 24 hours.
Laryngoscope, 112:364–369, 2002
INTRODUCTION
Tracheal anastomoses are often protected with the
aid of additional measures. These include chest-to-chin
From Klinik fu¨r Viszeral- und Transplantationschirurgie, Han-
nover, Germany.
Editor’s Note: This Manuscript was accepted for publication October
9, 2001.
Send Correspondence to Matthias Behrend, MD, Klinik fu¨r Viszeral-
und Transplantationschirurgie, Carl-Neuberg-Str. 1, 30623 Hannover,
Germany. E-mail: Behrend.Matthias@MH-Hannover.de
Anesthesia and Surgical Procedure
Anesthesia was induced with 0.2 mg/kg midazolam intrave-
nously (IV) and 7 to 8 mg/kg propofol IV. The sheep were intu-
bated with a cuffed endotracheal tube (Bivona Medical Technol-
ogies, Gary, IN; ID 9.0 mm, L 55 cm) and a stomach tube was
inserted into the rumen. Anesthesia was maintained with isoflu-
Laryngoscope 112: February 2002
364
Behrend et al.: Breaking Strength of Tracheal Anastomosis

rane at 2 to 2.5% end-tidal concentration in oxygen (2 L/min).
Ventilation was controlled to assure normocapnia. For perioper-
ative analgesia, 4 mg/kg carprofen IV and 0.6 mg buprenorphine
0.6 mg intramuscularly (IM) were administered. In addition, the
surgical area was injected with 20 mL lidocaine HCl. Antibiotic
therapy was started preoperatively using depot-penicillin. The
skin and subcutaneous tissues were incised median from 3 cm
below the larynx to a length of 15 cm. The cervical trachea was
exposed by a midline separation of the paired strap muscles and
mobilized circumferentially for 6 to 12 cm according to the
planned resection. In the first group of 15 sheep, 3 cm of trachea
was resected. In the second and third groups, 6 and 9 cm of
trachea, respectively, were resected (see Table I). The distance
between the tracheal ends was measured in millimeters. The
necessary force for approximation was measured three times in
each case and expressed in Newtons (N): A 2.0 polypropylene
suture was placed through both ends of the trachea in a U-shaped
fashion and placed on a standard spring balance. Nothing was
undertaken to reduce tension; no release maneuvers or stay su-
tures were used.
Ringer’s lactate solution during transport to the material testing
machine.
Material Mounting
A special device was constructed for mounting and affixing
the tracheae on a material testing machine. Details of the con-
struction have been previously reported.5 The inner diameters of
the tracheae were measured and a suitable hollow cylinder and
the matching tapered nut were chosen. After the tracheae were
affixed to the hollow cylinders, they were fastened with a wide
hose clamp and thereafter submitted to pressure by tightening
the screw of the hollow cylinder. Because of the expansion of the
hollow cylinders inside the tracheae and the external affixation
with the hose clamps, the tracheae were tightly fastened without
being damaged themselves. Because the tracheae themselves
stretched during the tension test and their diameters correspond-
ingly reduced, they were automatically increasingly tightened
onto the holder.
In the first group of 15 animals, three different suture
materials were used: single interrupted sutures with 4.0 polygla-
ctin 910 (Vicryl, Ethicon, Norderstedt, Germany), single inter-
rupted sutures with 4.0 polydioxanone (PDS, Ethicon), and a
running 4.0 polypropylene (Prolene, Ethicon). Sutures were
placed every 5 mm, initially on the membranous part of the
trachea. Both the continuous and interrupted techniques used
full-thickness bites of all layers, usually around the adjacent
cartilaginous rings with sutures spaced 5 mm apart. Because of
fear of a suture breakdown, we decided to use single interrupted
sutures in long-segment resections (6 and 9 cm). By using a
continuous suture, the breaking of the thread would have re-
sulted in a complete disruption of the anastomosis. To ensure a
satisfactory gliding of the thread during knotting under tension,
we used polydioxanone, a monofilament, smooth suturing mate-
rial (see Table I). After completion of each anastomosis, tracheal
apposition was evaluated as good (rings accurately aligned
around more than 180° of the circumference), fair (accurate align-
ment of 120–180°), or poor (accurate alignment of less than
120°).7
Tension Tests
The tension tests were carried out with a Zwick material
testing machine (Zwick GmbH & Co., Ulm, Germany), version
1445 (software 7047.5a). The tracheae were mounted onto the
machines as described above. The tensile load was initiated and
the holders moved apart from each other with a speed of 1 mm per
second. The force between the machine’s holders was measured in
Newtons. From a force of 2 N onward (preliminary force), cali-
bration was reset to zero and the actual measurement began.
During measurement, the traversing forward feed (the movement
of both holding devices away from each other) was continuously
recorded in exact steps of 0.1 mm, the force in 0.1 N. Measure-
ment was concluded when the force fell below the maximum value
by over 20 N. It was recorded in which area and which manner
the tracheae broke. Distinctions were made between breakage in
the proximity of the carrier, in the free portion, between the
sutured ends, or whether tearing of the tracheal ring occurred
cranially or caudally at the suture.
The readings were recorded and processed in the Excel
spreadsheet program (Microsoft Corp., Redmond, WA). The max-
imum force reached up to the breaking of the tracheae was
ascertained. The increase in the linear part of the curves was
determined as the base value for the elasticity module through a
linear regression. Trend degrees were accepted from an identity
measurement of R2 Ͼ0.995 onward.
Necropsy
All sheep were killed with an overdose of sodium pentobar-
bital (Eutha77, Hoechst, Germany) in accordance with the
planned survival period. An animal from each group was killed
postoperatively after 1, 2, 4, and 8 weeks, and 6 months. Autopsy
was performed immediately after killing. Abnormal necropsy
findings were recorded. The entire trachea was removed, together
with the larynx and proximal of the main bronchi. The tracheae
were carefully freed of remaining tissue and the center portion,
with the anastomoses situated in the center, was shortened to a
standard length of 120 mm. The transverse and longitudinal
diameters were caudally and cranially measured with a slide
gauge. The tracheae were stored in a humid environment using a
Statistics
The values for the maximum force, increase, and tracheal
diameter were entered in an SPSS program (SPSS for Windows,
release 10.0.7, SPSS Inc., Chicago, IL). The descriptive analysis
(mean value, standard deviation, minimum, maximum) was fol-
lowed by a mean value comparison with the t test for independent
random samples.
TABLE I.
Experimental Structure.
Group
I
No.
15
Tracheal Resection
3 cm
Suturing Technique
Single interrupted sutures with polyglactin 910 (n ϭ 5),
polydioxanone (n ϭ 5), running suture with
polypropylene (n ϭ 5)
II
5
5
6 cm
9 cm
Single interrupted sutures with polydioxanone
Single interrupted sutures with polydioxanone
III
Laryngoscope 112: February 2002
Behrend et al.: Breaking Strength of Tracheal Anastomosis
365

Specimen Preparation, Planimetry, and
and 22 shortly above the material holding device. In all
cases, the tracheae broke between two adjacent tracheal
rings. The results are recorded in Table III.
Histology
For those tracheal specimens that did not tear at the anas-
tomoses, the cross-sectional areas of the anastomoses were deter-
mined planimetrically with a scanner as described earlier.8 Three
measurements were taken for each section and the mean cross-
sectional area (CSA) calculated.3 The grade of stenosis was clas-
sified according to a system proposed by Hsieh,9 the results of
which have been published earlier.10 Specimens for histology
were taken longitudinally through the anastomosis whenever
possible. The specimens were examined under a light-optical
microscope and evaluated for acute and chronic inflammation.
All operative specimens were cut to size in the afore-
mentioned manner and mounted on the material testing
machine. The details of the maximum tension force and
the rate of rise are summarized in Table III. With all
animals that were killed after 1 week, the trachea broke in
the proximity of the anastomosis. However, the sutured
area itself did not tear, but one of the two tracheal rings
included in the suture tore away from the remainder of
the specimen. In the case of the remaining 20 specimens
after 2, 4, 8, and 24 weeks, the trachea broke further from
the anastomosis. The anastomotic site was more stable
than the remainder of the trachea. In the group of 25
operated tracheae, the suture stability increased with
time. The mean values in the first week were, with 177 N,
considerably lower than the following intervals.
RESULTS
Anesthesia and Surgical Procedure, Clinical
Evaluation, and Planimetry
All sheep survived the operation and the subsequent
period up to their planned euthanasia. No abnormalities,
such as shortness of breath or stridor, could be observed at
any time before death, with the exception of one animal
that showed a severe shortness of breath immediately
before euthanasia. All animals coughed occasionally. Dys-
pnea and subcutaneous emphysema were not observed.
Details have been reported earlier10 and are summarized
in Table II. The planimetric determination of the CSA
resulted in stenosis rates of 0% to 94% (details shown in
Table II).
Statistics
Mean values, standard deviation, and minimum/
maximum for the maximum force required up to the point
of breaking and for the increase in the linear portion are
mentioned in Table III and Figure 1. First, it was calcu-
lated whether the tracheal diameter influenced the max-
imum force required for breakage. The correlation accord-
ing to Pearson produced a value of r ϭ 0.329. Thus, the
influence of the diameter on the maximum breaking force
was not sustained and the diameter was not taken into
consideration in the subsequent statistical studies.
Breaking Tests
Twenty-four untreated sheep tracheae were cut to
requirement and mounted on the material testing ma-
chine. Of the 24 tracheae, 2 broke in the middle portion
TABLE II.
Distances, Tension, and Cross-sectional Area of Tracheal Anastomosis After Resections of Different Length as Published Earlier.10
Force for
Approximation
(no.)
CSA
Anastomosis‡
(cm2)
Scheduled
Survival
Distance*
(mm)
Distance†
(mm)
Luminal
Stenosis§
Classification
According9
Resection Length
3 cm resection
No.
3
3
3
3
3
1
1
1
1
1
1
1
1
1
1
1 wk
2 wk
4 wk
8 wk࿣
6 mo
1 wk
2 wk
4 wk
8 wk
6 mo
1 wk
2 wk
4 wk
8 wk
6 mo
54 (Ϯ 19)
84 (Ϯ 19)
117 (Ϯ 8)
145 (Ϯ13)
7.2 (Ϯ 0.8)
13.6 (Ϯ 5.1)
21.4 (Ϯ4.7)
2.55
2.17
1.80
1.00
1.25
1.88
1.54
0.99
0.35
1.65
3.00
0.90
1.94
0.46
0.84
8%
8%
Excellent
Excellent
27%
58%
49%
0%
Mild stenosis
Moderate stenosis
Mild stenosis
Excellent
6 cm resection
9 cm resection
57 (Ϯ 8)
9%
Excellent
61%
83%
23%
16%
40%
42%
75%
59%
Moderate stenosis
Severe stenosis
Mild stenosis
Good
55 (Ϯ 13)
Mild stenosis
Mild stenosis
Severe stenosis
Moderate stenosis
*Distance between tracheal stumps after distal tracheal transsection, before tracheal resection.
†Distance between tracheal stumps after second tracheal transsection, after tracheal resection.
‡Cross-sectional area at the anastomosis.
§Luminal stenosis determined by the following formula: 100 Ϫ (CSAanastomosis/(CSAcranial ϩ CSAcaudal/2)*100).
࿣One animal of this group had a disorder (probably an infection) at the anastomosis. Without this animal, the stenosis rate would be 42%—mild stenosis in
this group.
Laryngoscope 112: February 2002
Behrend et al.: Breaking Strength of Tracheal Anastomosis
366

TABLE III.
Measuring Results of Tracheal Anastomosis and Breaking Strength.
Increase
(N/mm)
Survival
No.
Nmax
In vivo sutures sorted by duration
1 week
5
5
177 (Ϯ 30)
233 (Ϯ 33)
273 (Ϯ 28)
235 (Ϯ 27)
247 (Ϯ 42)
236 (Ϯ 44)
232 (Ϯ 27)
232 (Ϯ 52)
198 (Ϯ 51)
10.7 (Ϯ 1.5)
12.6 (Ϯ 2.6)
15.0 (Ϯ 3.4)
15.7 (Ϯ 2.2)
16.5 (Ϯ 2.9)
15.6 (Ϯ 4.2)
11.6 (Ϯ 2.6)
14.3 (Ϯ 2.8)
11.1 (Ϯ 3.3)
2 weeks
4 weeks
5
8 weeks
5
6 months
polyglactin
polypropylene
polydioxanone
—
5
Sorted by suture
Native
5
5
15
24
In the group of sutured tracheae, we examined
whether a statistical difference existed beyond the post-
operative phase. A significant P value could not be found,
which was probably because of the small number of cases
examined. However, the suturing technique also had no
decisive influence on the maximum breaking force (see
Table III).
A difference becomes apparent when one combines all
25 operated tracheae together and compares them with
healthy tracheae with respect to the maximum breaking
force (t test with independent random samples; P ϭ .015).
The operated tracheae show a significantly higher break-
ing strength (mean value 233 vs. 198 N) than native
tracheae. Also, the maximum rate of rise, being the mea-
sure for the elasticity module, lies significantly higher
(P ϭ .004; mean values 14.0 vs. 11.1). This means the
operated tracheae are more rigid and react to dilation with
a greater increase in strength. The length of resection and
the related tension on the tracheal anastomosis has no
influence on the breaking strength.
DISCUSSION
Most studies of suture tension and the danger of
rupture are of a relatively older nature.2,11,12 The values
ascertained at that time have received general acceptance,
although at least the suture materials have since changed
significantly. Comparative studies of the danger of rup-
ture of healthy tracheae were, until recently, not avail-
able.5 Studies were not available concerning the breaking
strength of tracheal anastomoses in the postoperative
phase, with the exception of a small number of evaluations
made on small animals.13,14 We have recently presented a
method of examining the breaking strength of healthy and
anastomosed tracheae.5
This method is exceptional inasmuch as it enables
the mounting of the complete trachea, i.e., circumferen-
tially intact, on a suitable material testing machine.
With other methods, often only segments were sub-
jected to strain, which, as a result of the elastic distortion
of the trachea, can lead to different results. In vitro, the
continuous suture proved to be superior to the single in-
terrupted suture and attained a breaking strength that
did not differ from that of healthy trachea. An in vivo
study could not confirm these results to such an extent.6
Fig. 1. (A) A box plot of the breaking force postoperatively. The
division of the groups was made in accordance with the postoper-
ative surveillance time. The thick line within the box corresponds
with the median. The box itself presents the first and third quartile
(25th, respectively, the 75th percentile). The lined border represents
the standard deviation. One can clearly see that the values of the
maximum breaking strength between the first and second weeks
rose strongly. Thereafter, great fluctuations did not occur. (B) Box
plot of the comparison between native and anastomosed tracheae.
Despite the superimposure of the boxes, the difference with P ϭ
.015, which is statistically significantly different in favor of the anas-
tomosed tracheae.
Laryngoscope 112: February 2002
Behrend et al.: Breaking Strength of Tracheal Anastomosis
367

glottis. At all events, a mechanical protection of the
anastomosis is not effected by this method. A tracheotomy
beneath the tracheal anastomosis can only be performed
in the case of short segment resections and is, particularly
in this case, unnecessary. In respect to long segment re-
sections, the trachea can usually not be mobilized to such
an extent that a tracheotomy would be useful. Over and
above this, the perfusion of the trachea is compromised
and the danger of infection increased. Having performed
mini tracheotomies ourselves on a number of patients,4 a
retrospective evaluation leads us to advise against such a
method. The percutaneous mini tracheotomy bears a con-
siderable danger of infection for the cervical wound,
especially the tracheal anastomoses. With a closed mini
tracheotomy, an obstruction in flow caudal of the anasto-
mosis occurs and is therefore extremely disadvantageous
to the respiratory physiology. In addition, manipulations
on the mini tracheotomy trigger an urge to cough, which is
also unwelcome. The air passage is protected in the case of
an insufficiency of the anastomosis, but whether this
would still be valid for a complete rupture of the anasto-
mosis must be regarded as doubtful. It can be expected
that in such a case, the distal trachea is pulled toward the
caudal and that the distal portion of the mini tracheotomy
no longer fits securely in the trachea.
In a previous study, we were in a position to illustrate
the high mechanical stability of tracheal anastomoses un-
der load in vitro.5 In this article, we have now established
that this quickly increases so that extra measures do not
seem necessary to mechanically protect tracheal anasto-
moses. Therefore, as a priority, the various methods of
reducing the anastomotic tension should be given prefer-
ence. Because the anastomotic tension undoubtedly influ-
ences the rate of stenosis, tension sutures may possess a
certain legitimacy, although it remains to be considered
that these, on the other hand, reduce the perfusion of the
anastomotic site and thus in turn can promote the devel-
opment of a stenosis. They do not seem necessary solely as
protection against suture line separation. However, as a
reservation, it must be stated that this must not automat-
ically apply to patients. At least with older patients, and
particularly those that have been treated on a long-term
basis with high doses of corticoids, this may not apply.
Additionally, one must consider that during the clinical
routine, other additional problems (sepsis, poor technique,
and so on) should be taken into account. Further experi-
mental studies should include the influence the various
measures of mechanical protection to exert on the anasto-
motic perfusion and, when necessary, consider further
measures for the improvement of the perfusion.
TABLE IV.
Statistical Analysis for Maximum Force and Maximum Increase.
Native versus Operated
(all time periods)
Maximum force
Increase
0.015*
0.004*
*T-test for independent random samples.
In vivo, additional mechanisms influence and affect the
durability of tracheal anastomoses. Therefore, a compari-
son between the breaking strength of tracheal anastomo-
ses and healthy tracheae is of even more interest.
A comparison of different postoperative phases (see
Table III) reveals that the breaking strength increases
with time. This has been previously proven in a similar
fashion, however, within a more limited timeframe.14 In
the first week, the tensile strength is still below that of
healthy tracheae. This difference is, however, not statis-
tically significant. In the case of all further postoperative
phases (2, 4, 8, and 24 wk), the mean values of the break-
ing strength of the operated tracheae is higher than that
of healthy tracheae. When one combines all operated tra-
cheae, including the first postoperative week, this differ-
ence to the healthy tracheae now achieves a statistical
significance (P ϭ .015). The fact that the maximum rate of
rise of the distance/force curve is also higher is explained
by the greater rigidity of the scar tissue of the healed
anastomoses. The separate analysis according to suturing
technique (see Table III) reveals that the suturing tech-
nique itself is irrelevant. According to our studies, even in
the first postoperative days, tracheal anastomoses possess
a scarcely lower tensile strength than healthy trachea.
After no later than 14 days, the breaking strength is
considerably higher than that of healthy trachea. This
also applies to anastomoses that have been performed
with considerable suture tension of up to 20 N after long
segment resection (9 cm).10
When one now analyzes different methods of me-
chanical suture protection from this standpoint, it be-
comes obvious that a number of them are unsuitable and
superfluous. The chin-to-chest suture is designed to pre-
vent excessive extension of the vertebral column. It is
unpleasant for the patient and causes unsightly scars.
From the values obtained from our study, it does not
appear to be necessary to allow such a suture to remain in
place for 10 to 14 days.1 It should, at the outside, be used
for a shorter period or replaced by a suitable cervical collar
with fixation in a flexed position, but generally, a fixation
in the flexed position should not be necessary. The pro-
longed intubation with an inflated cuff should by all
means be avoided. The pressure from the cuff reduces the
perfusion of the mucous membranes and thus prevents
the rapid healing of the anastomosis. In addition, secre-
tion as a rule gathers above the blocked cuff and therefore
in the proximity of the anastomosis. This could possibly
encourage an infection in this area of the mucosal scar,
which is not healed at that time. More useful would pos-
sibly be a non-blocked tube that would protect the respi-
ratory tracts, particularly against a swelling of the sub-
CONCLUSION
Our results reveal the extremely high mechanical
stability of tracheal anastomoses in vivo, regardless of the
suturing technique used and the amount of tension ex-
erted on the tracheal anastomosis. As early as 1 week
after surgery, the values for the breaking strength lie only
slightly under those of healthy tracheae. With increasing
time, the stability even increases to such an extent that
finally, significantly higher values were obtained than
those of healthy tracheae. Supplementary measures for
Laryngoscope 112: February 2002
368
Behrend et al.: Breaking Strength of Tracheal Anastomosis

5. Behrend M, Kluge E, Schuettler W, Klempnauer J. The
breaking strength of native and sutured trachea. An ex-
perimental study on sheep trachea. Eur Surg Res 2001;33:
255–263.
6. Behrend M, Klempnauer J. A comparison of interrupted and
continuous sutures concerning their breaking strength af-
ter tracheal anastomosis in sheep. Eur J Surg (in press).
7. Hedlund CS. Tracheal anastomosis in the dog. Comparison of
two end-to-end techniques. Vet Surg 1983;13:135–142.
8. Behrend M, Klempnauer J. Influence of suture material and
technique on end-to-end reconstruction in tracheal sur-
gery: an experimental study in sheep. Eur Surg Res 2001;
33:210–216.
9. Hsieh CM, Tomita M, Ayabe H, Kawahara K, Hasegawa H,
Yoshida R. Influence of suture on bronchial anastomosis in
growing puppies. J Thorac Cardiovasc Surg 1988;95:
998–1002.
10. Behrend M, Klempnauer J. Tracheal reconstruction with
high tension: an experimental study in sheep. Eur J Surg
Oncol 2001;27:581–588.
the mechanical protection of the tracheal anastomosis
against suture line separation therefore seem unneces-
sary. Measures that involve additional risks, which cer-
tainly applies to the mini tracheotomy, should by all
means be avoided. However, the therapeutic value of other
additional measures, such as the promotion of vascular-
ization, is not affected by our study.
Acknowledgments
The authors thank Dr. Hartmut Hermann from the
Biometry Department of the Hanover Medical School for
the help and support given with the statistical analysis.
BIBLIOGRAPHY
1. Har-El G, Shaha A, Chaudry R, Lucente FE. Resection of
tracheal stenosis with end-to-end anastomosis. Ann Otol
Rhinol Laryngol 1993;102:670–674.
2. Grillo HC. Surgery of the trachea. Curr Probl Surg 1970;7:
3–59.
3. Fingland RB, Layton CI, Kennedy GA, Galland JC. A com-
parison of simple continuous versus simple interrupted
suture patterns for tracheal anastomosis after large-
segment tracheal resection in dogs. Vet Surg 1995;24:
320–330.
11. Cantrell JR, Folse JR. The repair of circumferential defects of
the trachea by direct anastomosis: experimental evalua-
tion. J Thorac Cardiovasc Surg 1961;42:589–598.
12. Maeda M, Grillo HC. Effect of tension on tracheal growth
after resection and anastomosis in puppies. J Thorac Car-
diovasc Surg 1973;65:658–668.
13. Urschel JD. Comparison of anastomotic suturing techniques
in the rat trachea. J Surg Oncol 1996;63:249–250.
14. Hyytinen T, Paavonen T, Inkinen K, Ahonen J, Mattila S.
Airway anastomotic healing in the rat tracheal autograft.
Eur Surg Res 1999;31:155–161.
4. Musholt TJ, Musholt PB, Behrend M, Raab R, Scheumann
GF, Klempnauer J. Invasive differentiated thyroid carci-
noma: tracheal resection and reconstruction procedures in
the hands of the endocrine surgeon. Surgery 1999;126:
1078–1087.
Laryngoscope 112: February 2002
Behrend et al.: Breaking Strength of Tracheal Anastomosis
369