Keywords
microvascular anastomosis - simple interrupted - microvascular anastomosis technique
- microsurgery
Successful performance of a microsurgical anastomosis is imperative in free tissue
transfer and limb/digit replantation. It is a delicate and highly nuanced procedure
that can be done in several ways. There is a wide range of microvascular anastomosis
techniques described in the literature with the optimal technique being a topic of
debate. Some of the options for performing a microsurgical anastomosis include simple
interrupted, continuous, locking continuous, interrupted horizontal mattress, sleeve
anastomosis, fibrin glue, couplers, and microclips.[1] The ideal microvascular anastomosis technique would be easy to perform, minimize
ischemia time, avoid vessel wall trauma, and lead to both short- and long-term patencies.
It is widely understood that the simple interrupted suture technique is the most standard
and easily conceptualized approach to microvascular anastomosis.[1]
[2]
[3]
[4] It is less widely understood, however, that there are many different sequences by
which simple interrupted sutures can be placed.
There are certain clinical variables that influence whether one sequence is more or
less preferable (these include length of vessel, surgical skill level, room for microvascular
clamps, and availability of an assistant).[4]
[5]
[6]
[7] Such nuances of each sequence have been largely ignored in the literature, as descriptions
of the suture sequence is often ignored all together, and there is varied nomenclature.
The purpose of this study is to identify every distinct suture placement sequence
for microvascular anastomosis published in the literature, describe them using standardized
nomenclature, and discuss the clinical scenarios in which each technique is the most
appropriate.
Methods
A PubMed search was performed in October 2019 using the keywords “microvascular anastomosis,”
“microvascular anastomosis technique,” “simple interrupted,” and “microsurgery” to
identify the types of simple interrupted microvascular anastomoses described in the
literature.
Additionally, we created a standardized nomenclature by demonstrating the orientation
of the blood vessel in a patient with surgical clamps and assigning clock face values
to a transected blood vessel ([Fig. 1]). We define 9 o'clock as the most anterior part of the blood vessel and 3 o'clock
as the most posterior (“deepest”) part of the blood vessel. Based on this, we define
12 o'clock as the midpoint of the segment farther from the surgeon between 9 o'clock
and 3 o'clock, and 6 o'clock as the midpoint of the segment closer to the surgeon
between 3 o'clock and 9 o'clock. The anterior wall is the 180 degrees of the vessel
that runs from 6 o'clock to 9 o'clock to 12 o'clock, and the posterior wall is the
180 degrees of the vessel that runs from 6 o'clock to 3 o'clock to 12 o'clock. The
sidewalls of the vessel run between 9 o'clock and 3 o'clock, with the near sidewall
as the one closer to the surgeon, and the far sidewall as the one farther from the
surgeon ([Fig. 2]).
Fig. 1 Orientation of transected blood vessel in relation to the patient and operating clamps.
Fig. 2 Standardized nomenclature of a transected blood vessel.
By this nomenclature, anterior wall, posterior wall, and the two sidewalls are each
180 degrees of the vessel circumference. Therefore, the logic must follow that anterior/posterior
walls and sidewalls cannot coexist in the same scheme. When the first sutures are
placed, they define whether the vessel circumference will be conceptualized as either
anterior/posterior walls or sidewalls, and this will remain constant for the entirety
of the suture sequence.
Results
Four distinct simple interrupted microsurgical anastomosis techniques were identified:
triangulation, 12 o'clock to 6 o'clock, posterior-wall-first, and 3 o'clock to 9 o'clock.
Triangulation
First described by Alexis Carrel in 1902, the triangulation technique was one of the
first methods to be used in microvascular repair of small vessels, and was the basis
for his being awarded the Nobel Prize in 1912.[4] The triangulation technique is still referred to in some articles as the “classical”
microanastomosis,[8] but the term triangulation is inconsistently used.[9]
In the triangulation technique, three stay sutures are placed 120 degrees apart, at
the 11 o'clock, 3 o'clock, and 7 o'clock positions ([Fig. 2]). Tension is applied to two of the sutures, lifting the wall being sutured away
from the underlying wall.[4] Two additional sutures are placed between each pair of stay sutures.[10] Approximating double-opposing microvascular clamps are usually used.
The key advantage of the triangulation technique is that the asymmetrical placement
of the stay sutures minimizes the risk of inadvertently incorporating the intima of
the back wall, since tension on the two stay sutures raises the segment of wall being
sutured up from the longer underlying wall, thereby opening the lumen. Triangulation
technique is technically more challenging when compared with anterior wall first techniques.
Theoretically, vessel wall mismatch may occur when attempting to gauge 120 degrees.
However, Kim et al actually showed more regular suture placement when comparing the
triangulation technique with the 12 o'clock to 6 o'clock technique in a small randomized
controlled trial, likely secondary to more sutures being placed in the triangulation
technique reducing interstitch distance and thus variability in placement.[4] That being said, typically, the more sutures that need to be placed are considered
a risk for stenosis and/or thrombosis.[1] Clinically, the triangulation technique may be useful for trainees as one of the
biggest advantages and reduces the chance of including the back wall.
12 o'Clock to 6 o'Clock
Jacobson and Suarez[11] are largely credited for the development of microvascular surgery in 1960 when they
successfully began to anastomose vessels less than 1 mm in diameter.[12] The operating microscope, in addition to new suture and instruments, allowed for
precision and new techniques in manual suture.[13] The first description of the 12 o'clock to 6 o'clock microvascular surgery technique
is difficult to find in the literature but is presumed to have originated during this
time period. This technique is considered the most basic and is most often referred
to as the conventional method to perform a simple interrupted microvascular anastomosis.[2]
[4]
In this method, the first suture is placed at 12 o'clock (also sometimes referred
to as 0 degree), and the second stitch is placed at 6 o'clock (or 180 degrees). The
third and fourth sutures are placed at 2 o'clock and 4 o'clock completing the anterior
wall. The vessel is then turned over 180 degrees with a clamp, and the fifth and sixth
sutures are placed at 8 o'clock and 10 o'clock ([Fig. 3]).[6] Cobbett revised the standard 12 o'clock to 6 o'clock technique with the “eccentric
biangulation” method where the first two sutures are placed slightly more anterior
to the 12 o'clock and 6 o'clock positions. Double-opposing microvascular clamps are
necessary to rotate the vessel.
Fig. 3 Triangulation microvascular anastomosis technique.
The major disadvantage of this technique is the need to rotate the vessel 180 degrees
to suture the posterior wall. This requires enough length on the vessel and room for
the clamps, and introduces the potential vessel damage during the rotation. This technique
may also be beneficial for trainees learning microsurgery as it is technically most
simple as long as space for the clamps and rotation can be obtained.
Posterior Wall First
The technique, advantages, and outcomes of the posterior-wall-first technique were
first described by Harris et al in 1981.[5] This method is also sometimes referred to as the “back-up” technique.
The first suture is placed in the middle of the posterior wall with the second and
third sutures placed on either side of the first ([Fig. 4]). The fourth and fifth sutures are placed adjacent to the second and third advancing
anteriorly on either side, leaving a long tail to facilitate placement of the sixth
and seventh sutures. In a similar fashion, both the sixth and seventh sutures are
left long to aid placement of the last suture, which is placed equidistant from the
sixth and the seventh. Double-opposing microvascular clamps are not required for this
anastomosis as there is no rotation of the vessels.
Fig. 4 The 12 o'clock to 6 o'clock microvascular anastomosis technique.
Harris et al listed many advantages and declared there are no disadvantages to the
posterior-wall-first technique. Advantages include constant visualization of the back
wall decreasing the chance of accidentally catching the back wall, particularly useful
for microsurgeons in training. There is no need to rotate clamps, allowing placement
of sutures in spaces where maneuvering clamps is difficult or impossible. The authors
also consider the technique mentally less stressful as the surgeon does not lose concentration
to reposition, and they know each subsequent stitch is easier than the one prior.
Ultimately, the authors conclude the posterior-wall-first technique is less complicated,
more rapid, and easier to perform compared with anterior-wall techniques.[5]
Although Harris et al do not report any disadvantages, other authors have noted that
operating on the back wall may be technically more challenging and time consuming.[8] Clinically, this technique is advantageous in scenarios where maneuvering clamps
is difficult or impossible, for instance, a venous anastomosis during digital replantation,
a short recipient vessel leash, or friable/radiated vessels. Additionally, it may
be useful when there is a size mismatch between the vessels being anastomosed.
3 o'Clock to 9 o'Clock-Side-Side
Yu et al published, in 1986, a description of a simplified technique for end-to-end
microanastomosis that involved placing the first suture through the posterior wall,
second suture through the anterior wall with 90 degrees of rotation to facilitate
the placement of the remaining sutures.[8]
In the technique, clamps are placed opposite the surgeon and the first suture is placed
in the center of the posterior wall ([Fig. 5]). The second suture is placed in the center of the anterior wall, 180 degrees to
the first suture. Both sutures are left with long tails. A new anterior wall is created
by bringing the tail of the posterior wall superiorly and the tail of the anterior
wall inferiorly, rotating the vessel 90 degrees. The third, fourth, and fifth sutures
are placed along the new anterior wall. The vessel is then rotated back to its original
position and once again traction is placed to rotate another 90 degrees bringing the
unsutured half of the vessel anteriorly and sutures 6, 7, and 8 are placed.[8]
Fig. 5 Posterior-wall-first microvascular anastomosis technique.
According to the authors, the benefits of this technique is that it allows the surgeon
to place only one suture in the posterior wall, while all other sutures are placed
in the wall facing the surgeon. The angle of rotation is less than the conventional
180 degrees, decreasing possible damage to the endothelium and decreasing the need
to dissect the vessels proximal and distal to the clamps. Additionally, the authors
propose this method is technically easier to perform than posterior-wall-first technique.[8]
Nevertheless, one suture is still placed in the posterior wall, which is more challenging
than placing all sutures on the wall facing the surgeon. This technique is particularly
useful in settings with short vessel segments, when one may not want to ligate branching
vessels to increase vessel length or rotating the vessel is difficult due to space
constraints ([Fig. 6]).
Fig. 6 The 3 o'clock to 9 o'clock-side-side microvascular anastomosis technique.
Discussion
The birth of microsurgery dates back to 1906 when Alexis Carrel first described a
small vessel anastomosis.[12]
[14] The next major advance was not until 1960 when Jacobson and Suarez anastomosed 1 mm
vessels and the microscope was utilized in the operating room.[15]
Descriptions of how simple interrupted microsuture anastomoses are performed are often
vague in research articles. Firsching et al[16] compared continuous to simple microsuture technique and described continuous methods
in detail but did not describe the simple anastomosis method at all. Alghoul et al
and Turan et al both reported the simple interrupted microvascular suture is the conventional
technique and “gold standard,” but Turan et al described the conventional technique
as the triangulation method, while Alghoul et al considered the conventional technique
to encompass both the 12 o'clock to 6 o'clock and the triangulation methods.[1]
[17] There were also clear discrepancies in the literature when authors apply clock face
values to the vessel walls. Most frequently, 9 o'clock is used to denote the most
anterior aspect of the transected blood vessel, but one article assigned 12 o'clock
as the most anterior aspect of the vessel.[18] Yet another author used degrees to describe location around the vessel, 0 and 180
degrees representing the most anterior and posterior points, respectively.[19]
Upon reviewing each simple interrupted microvascular suture technique, it is apparent
that each has advantages and disadvantages ([Table 1]). Surgeons may find themselves in clinical scenarios where some techniques may be
favorable over others. In summary, the most commonly performed is the 12 o'clock to
6 o'clock, especially for beginners who are just beginning to visualize the three-dimensional
structure of the vessel. Posterior-wall-first and triangulation techniques may lead
to lower risk of catching the back wall in difficult cases or time-sensitive situations.
If presented with a short vessel leash, limited operative space, or injured/friable
vessels, one may consider the posterior-wall-first or the 3 o'clock to 9 o'clock-side-side
techniques to avoid the use of Acland clamps or excessive torsion on the vessels.
It would be beneficial for the experienced microsurgeon to become familiar with all
available techniques to optimize their operative field based on each unique case.
Table 1
Advantages and disadvantages of each simple interrupted microvascular suture technique
|
Triangulation
|
12 o'clock–6 o'clock
|
Posterior-wall-first
|
3 o'clock–9 o'clock
|
|
Required instruments
|
Double-opposing microvascular clamp
|
Double-opposing microvascular clamp
|
None
|
Double-opposing microvascular clamp or assistant
|
|
Degrees of rotation
|
120
|
180
|
0
|
90
|
|
Advantages
|
Reduces chance of posterior wall injury
|
Technically simpler
|
Optimal when there are space limitations (minimal vessel length needed)
|
No extensive dissection of vessel required proximal or distal to clamps
|
|
Most commonly performed
|
Reduces chance of posterior wall injury (direct visualization)
|
Less rotation can cause less intimal damage
|
|
|
Avoids vessel torsion
|
|
|
Disadvantages
|
Technically more challenging
|
Requires greater length of vessel exposure (to allow for 180 deg rotation)
|
Technically more challenging (posterior wall visualization)
|
Requires assistant
|
|
Challenge to match vessel edges
|
|
More time consuming
|
|
Research is lacking comparing the simple interrupted techniques. There is one randomized
controlled study that compares the advantages and disadvantages of the triangulation
technique to the “biangulation” technique, or as we refer to it the 12 o'clock to
6 o'clock, to find quantitative evidence for which technique should be advocated to
incorporate in microsurgery training.[4] In the study, medical students and surgical trainees underwent a 5-day microsurgery
course. Their ability to perform a biangulation and triangulation anastomoses was
evaluated on days 3 and 5 with the order of technique performed randomized. The outcomes
of the two techniques in terms of vessel structural patency and quality of anastomosis
were not significantly different, thus the authors concluded that both techniques
are equally appropriate for surgical training.[4]
Additional studies that further compare the four techniques in the clinical setting
are currently underway at our institution and will be reported in future publications.
Conclusion
This study identified four distinct sequences for the placement of simple interrupted
sutures for microsurgical anastomosis, and for the first time described them in a
standardized nomenclature.
