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A. Beech and J. Moe
a b
Fig. 9.3 (a) Cutaneous perforator of the peroneal artery identied on CTA for bula free ap
harvest. (b) Cutaneous perforator of the descending branch of lateral circumex femoral artery on
computed tomography angiography (CTA) for anterolateral thigh free ap harvest
CTA data can be used to map cutaneous perforators for a multitude of ap
types (Fig.9.3) [10, 11]. A prospective study of 60 patients undergoing bula
free ap reconstruction described a technique of cutaneous perforator mapping
on CTA and integration with computer-assisted surgical design, in which the
position of the patient-specic cutting guide was based on the localization of the
cutaneous perforator and planned skin paddle [12]. In comparison to perforators
identied intraoperatively, CTA perforator identication had a 96.2% accuracy
with a median precision of localization of 0.3mm, a positive predictive value
(PPV) of 99.29%, and a negative predictive value of 90.00% [12]. In the preoperative planning of deep inferior epigastric perforator (DIEP) aps, perforator
localization on CTA as compared to Doppler ultrasound was associated with
decreased surgical times, decreased complications including ap partial or total
failure, and led to a cost savings of $3000 USD per patient [13]. Limitations to
use of CTA include the need for IV contrast and ionizing radiation and the lack
of vessel ow dynamics.
Magnetic Resonance Angiography (MRA)
Gadolinium contrast-enhanced MRA imaging has been employed for preoperative
donor site evaluation and precludes the need for ionizing radiation and produces
detailed 3D images for assessment of vessel course, size, and branching pattern
[14]. MRA has a 100% specicity but decreased sensitivity (91%) in perforator
detection, providing detailed visualization of septocutaneous perforators greater
than 1mm in diameter but less accurate when evaluating perforators less than 1mm
as compared to CTA [15]. An additional limitation to the utility of MRA is the
length of time required for image acquisition, which may be anxiety-provoking in
patients who suffer from claustrophobia and can result in poor-quality images in
patients who are unable lie still.
Lower Exrtemity Arterial Duplex
Histo
Today’s ABI results: Right ABI: 1.17 Left ABI: 1.19; Right TBI: 0.91 Left TBI: 0.84.
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Color Duplex Ultrasound (CDU)
CDU is a noninvasive and portable imaging modality for evaluation of pedicle vascular anatomy, perforator size and course, and vessel ow dynamics (Fig. 9.4).
CDU combines Brightness-mode ultrasound and Doppler signal measurements to
provide real time a visualization of vessels and quantication of the blood ow
velocity. This can be done using either a 5 or 13MHz linear array Doppler probe. In
addition to providing an assessment of vascular anatomy and perforator localization, a quantitative assessment of peripheral arterial disease can be given through
ankle brachial indices (ABI), toe brachial indices (TBI), and arterial duplex measurements (Fig.9.5).
A prospective CDU exam of 38 patients prior to bula free ap detected vascular
anomalies in 2.6% and severe peripheral arterial disease in 7.9% of patients, leading
to an altered ap selection [16]. Additionally, cutaneous perforator mapping was
found to be 100% sensitive and specic in correlation to peroneal perforators identied intraoperatively [16]. The efcacy of CDU has been described in the localization of perforators for the anterolateral thigh (ALT) free ap, allowing selection of
the thigh with the largest vessels and shortest intramuscular course in order to
reduce the difculty of dissection [17].
Fig. 9.4 Right peroneal artery identication, ow, and perforator identied on color duplex ultrasound (CDU)
R PSV (cm/s)
EIA Dst
CFA prx
CFA dist
Profunda
SAF prx
SFA mid
SFA dst
Pop prx
Pop dst
Post Tib Prx
PTA Dst
Peroneal
Pero A Dst
Ant Tib
ATA Dst
ry/Presentation
The patient presents today for pre-op evaluation.
The patient has had a previous DVU study of the same type on 12/7/2017.
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Fig. 9.5 Assessment of peripheral arterial disease on color duplex ultrasound (CDU) using arterial
duplex measurements, ankle brachial indices, and toe brachial indices
R EDV (cm/s)
EIA Dst
CFA prx
CFA dst
Profunda
SFA prx
SFA mid
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Pop prx
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Post Tib Prx
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L PSV (cm/s)
EIA Dst
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Ant Tib
ATA Dst
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L EDV (cm/s)
EIA Dst
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SFA prx
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SFA dst
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Post Tib Prx
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Although CDU is most commonly used preoperatively, CDU also has applicability in the intraoperative and postoperative settings. Intraoperatively, CDU can be
utilized for perforator mapping of propeller aps and by utilizing ow velocity to
determine the optimal side of rotation [18]. Postoperatively, CDU can also be used
to assess perforator patency, to identify the presence of a thrombosis, and to trend
ow velocity in a ap with a questionable status [18]. Limitations of CDU include
a signicant inter-provider variability depending on the experience level of the
examiner.
A. Beech and J. Moe
Thermography
Infrared thermography (IRT) is a noninvasive imaging modality that has more
recently been investigated as a promising technology for preoperative ap assessment, intraoperative perfusion evaluation, and postoperative ap monitoring,
although this technology is not new. Infrared (IR) radiation was described by Sir
William Herschel in 1800, and the rst IR camera was developed in 1929 by Kalman
Tihanyi [19]. IRT cameras detect emitted IR radiation and provide a heat map.
Cutaneous temperature depends on vascularization with IR radiation skin emission
reecting local vascularity, which can be modulated by changes in cardiac output
[20]. As such, IRT provides a rapid, continuous, and real-time assessment of skin
paddle perfusion through the indirect measurement of the skin temperature. The
ow of blood in a vessel emits an infrared signal, which can be used to localized
perforators that are visualized as “hot spots.” Professional IRT cameras can elucidate temperature differences as subtle as 0.04°C [20].
Handheld IRT devices have been shown to be as effective as the conventional
handheld Doppler ultrasound in the localization of cutaneous perforators of the
abdomen, thigh, and sacrum. A study assessing cutaneous perforators of the abdomen, sacrum, and bilateral anterolateral thighs in 20 volunteers reported that 97% of
“hotspots” identied by IRT were conrmed with handheld Doppler [21]. A smartphone IRT imaging camera has been found to be effective in thermographic identication of cutaneous perforator hot spots, with resolution slightly inferior to the
larger and expensive handheld IRT devices [22]. The smartphone IRT has the potential to serve as a less expensive and more readily accessible alternative, with a cost
of approximately 1% that of a professional IRT camera [22].
Dynamic infrared thermography (DIRT) is a technique in which a cold challenge
is administered to a skin area of interest, and patterns of ow through perforating
vessels and surrounding skin areas are qualitatively assessed during rewarming [20,
23]. DIRT has shown utility in evaluating the speed at which hotspots appear fol-
lowing a cold challenge with ndings correlating to volume changes on CDU when
used in the preoperative planning for deep inferior epigastric perforator (DIEP) and
supercial inferior epigastric artery (SIEA) aps [23]. A study of 25 subjects
planned for DIEP ap found that the location of hotspots using DIRT matched the
position of the dominant perforators identied on handheld Doppler and CTA [24].
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DIRT has been shown to identify perforators larger than 1mm when compared to
CTA [25]. Additionally, DIRT allows for a qualitative assessment of the pattern of
rewarming between interperforator zones to identify the better perfused regions,
allowing for improved skin paddle planning [25]. While IRT obviates the need for
radiation and contrast exposure necessitated with CTA, the use of IRT for perforator
localization has several limitations including the inability to distinguish vessel morphology or perforator caliber, origin, or path after penetrating the deep fascia [20].
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Intraoperative Techniques
Advances inMicrovascular Anastomotic Technique
The success of free tissue transfer is dependent on the patency of the arterial and
venous anastomoses and directly correlates to the quality of the anastomoses. Since
rst described in the early 1900s, the simple interrupted suture technique remains
the primary modality of microvascular anastomosis (Fig.9.6). The evolution of
microsurgical techniques has included renements in microscope systems and in
the microsurgical armamentarium such as ne suture and instrumentation (Fig.9.7).
Currently used innovations including anastomotic coupler systems address the
importance of decreasing operative time while maintaining high anastomotic
patency rates.
Anastomotic Coupler Systems
In 1900, Payr described a nonsuture method of anastomosis utilizing magnesium
tubes to couple vessels; however, success rates were compromised by signicant
tissue necrosis secondary to strong electrochemical forces generated by the
Fig. 9.6 Hand-sewn arterial anastomosis employing the interrupted suture technique
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Fig. 9.7 Amamentariam for microvascular surgery
A. Beech and J. Moe
a
b
c
Fig. 9.8 Venous anastomosis using the coupler system. (a) Eversion of vessel wall onto interlock-
ing pins. (b) Positioning of vessel end on polyethylene ring. (c) Completed venous anastomosis
using the coupler system with the connected implantable Doppler probe
magnesium [26]. In 1986, Ostrup and Berggren introduced the Unilink Microvascular
Anastomotic System, which served as the basis for design for currently used coupler systems (Fig.9.8) [27]. The Unilink system consisted of two rings composed of
high-density polyethylene and six interlocking pins allowing for 90° eversion of the
vessel wall for intima to intima contact without the introduction of foreign material
[27]. Since its introduction, multiple studies have showed venous couplers decrease
operative time while maintaining low rates of venous thrombosis [28–30].
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The use of arterial coupler systems has not been widely adopted by microvascular surgeons to the same degree as venous couplers. Early reports from the 1990s
reported a high incidence of arterial thrombosis with use of arterial couplers, attributed to the fact that arterial walls are much thicker, less elastic, and more subject to
radiation-induced brosis and atherosclerosis [31–33]. A greater difculty in the
arterial wall eversion is suggested to result in intimal tears or a greater incidence of
obstruction of the arterial lumen with a resultant decrease in laminar blood ow and
predisposing to thrombosis. A recent systematic review found a 92.1% success rate
of arterial couplers as determined by arterial anastomosis patency and ap viability
and up to 3.2% rate of arterial thrombosis [34]. Additionally, a 12.8% (range 0–50%)
rate of troubleshooting was reported secondary to a multitude of reasons including:
traumatic injury or intimal tear during instrumentation, a need to abort the coupler
due to small arterial diameter (<1.5mm), challenges everting thick arterial vessel
walls, and challenges managing vessel wall and coupler luminal diameter discrepancies [34]. Despite the increased risk of signicant complications, arterial couplers
are associated with a reduction in the time for arterial anastomosis and operating
time as compared to the hand-sewn technique; however, technical challenges and
inexperience in arterial coupling can limit the advantage of time gained using the
coupler device [34].
Case selection for applying the arterial coupler is of utmost importance, with its
use only considered for select cases in which: a coupler size of greater than 2.0mm
can be used, vessel size mismatch is limited to 1:1.5, there is a low wall thickness to
lumen ratio, and arteries are devoid of severe brosis or atherosclerotic plaques
[34]. Additional techniques have been described to mitigate complications, including: meticulous adventitiectomy, dilation to upsize vessels 1.5mm in diameter, and
slit arteriotomy when upsizing vessels less than 1.5mm in diameter [34]. While
artery-specic coupler systems are available, coupler systems used for venous anastomosis are FDA-approved for arterial anastomosis as well [35].
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Advances intheOperative Microscope
The evolution of the operative microscope over the past century has revolutionized
operations in head and neck surgery, plastic surgery, ophthalmic, neurosurgery, and
dentistry. The microscope was rst introduced into the operating room in 1921 by
Carl Olof Nylen, an otolaryngologist at the University Clinic of Stockholm [2]. In
1922, Gunnar Holmgren developed the binocular microscope attached with a light
source, which provided the added benet of stereopsis [2]. In 1961, Jacobson developed the rst double binocular microscope, named the diploscope, which allowed
for improved surgical assistance [36].
Contemporary operative microscopes allow for autofocusing with automation,
improved portability, and coaxial designs for improved maneuverability (Fig.9.9).
Optical carriers and binocular tubes allow for positioning of the microscope in orientations which maintains operator efciency and comfort. Modern innovations
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Fig. 9.9 Use of binocular
operative microscope for
microvascular anastomosis
A. Beech and J. Moe
have allowed for additional capabilities including intraoperative uorescence systems and neuronavigation software integration [37]. Despite these innovations, the
operative microscope still holds a relatively large footprint, making it cumbersome
to position intraoperatively. Depending on the unit, the operative eld of view can
be restricting and can place the surgeon in nonergonomic positions, which can contribute to operator fatigue. New technologies including the exoscope and robotic
microscope have been developed to address these challenges.
Exoscope
The exoscope is an extracorporeal video telescope operating system introduced in
the last decade. A three-dimensional (3D) camera held by a supporting arm projects
a magnied, high denition (HD), 4K video of the surgical eld onto an HD monitor, and operators view the monitor using polarized 3D glasses. This “heads up”
display has become increasingly popular as it potentially allows for a more ergonomic position for the surgeon, along with better visualization for team members in
the operatory [38]. The exoscope allows for a magnication power of 8–30 times, a
depth of eld between 7 and 44mm, and a focal distance of 20–50cm. The camera
is controlled with a sterilely draped joystick, allowing for the operator to zoom,
focus, and adjust the position of the camera with minimal change in position.
Several exoscopes are currently on the market [39, 40] and have been shown to
provide equivalent outcomes as compared to a standard operative microscope when
used for microvascular surgery [41, 42]. The rst microvascular free ap anastomo-
sis using the exoscope was described in 2017 using a DIEP ap for breast
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reconstruction [43]. A simulation noninferiority trial reported that the exoscope was
noninferior to the operating microscope with good focusing of the surgical eld
with high image quality and strong luminance but found that the exoscopic microvascular anastomosis was more time consuming [42]. A case-control pilot study of
22 microvascular free aps performed using an exoscope and 27 free aps performed with an operative microscope found no difference in operative time, ischemia time, or microsurgical complications between groups, with operator reported
favorable ergonomics, excellent image quality, and ease of equipment manipulation
using the exoscope [41].
Potential benets of the exoscope include versatility of camera positioning to
allow for improved comfort of the operator and assistant, a large working length to
allow for freedom of movement for hands and instrumentation, and the same view
of the operative eld for operators and observers, which allows for a more immersive experience not provided with a typical two-dimensional conventional scope
screen [42]. A potential disadvantage of the exoscope includes a decrease in resolution at higher magnications, which has been variably reported [38, 41].
Robotic Microscope
A robotic operative microscope has only been very recently commercially available
(Fig.9.10) [44]. It consists of a high-resolution 3D camera on a robotic arm articulating along six axes. The 3D HD images are transmitted to a head-mounted display
(HMD) worn by the operator and an HD external display. The HMD has a weight of
approximately 0.5kg and consists of two micro-displays with adjustable interpupillary distance. A foot pedal is used to unlock a control menu with which the operator
interacts through the HMD using motion detection. This allows the surgeon to
change the camera position, angle, magnication, and focus without changing body
position. The currently available system enables a magnication factor ranging
from 2.7 to 30.1 times and a eld of view range from 5.8 by 4.3 mm to 64.5 by
48.4mm with full optical zoom. Additional functionality allows the operator to save
multiple views and camera positions and can return to a previously saved view
Fig. 9.10 The robotic
microscope with headmounted display and HD
external display
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through the control menu display [45]. The utility of this emerging technology for
microvascular surgery remains to be shown through clinical studies.
A. Beech and J. Moe
Intraoperative Flap Assessment
The patency of the arterial and venous anastomoses is vital for ap survival, with
early ap failure commonly related to technical error in performing the vascular
anastomoses. Clinical patency tests including vessel lling, ap color and bleeding,
and the strip or milk test continue to be the traditional method for assessing anastomotic patency. Adjunct tools including implantable Doppler probe systems (discussed in the next section) allow conrmation of vessel patency. Indocyanine green
angiography allows evaluation of ap perfusion and vessel patency.
Indocyanine Green Angiography
Indocyanine green angiography (ICGA) is an imaging technique that allows for
real-time evaluation of blood ow and is an invaluable tool for the microvascular
reconstructive surgeon. First FDA approved for clinical use in 1955, indocyanine
green (ICG) is an amphiphilic contrast agent consisting of a near infrared (NIR)
tricarbocyanine orescent dye [46, 47]. Once administered intravenously, the anions
bind to plasma proteins [47]. Clinically approved ICGA systems operate in the
“NIR-1” window (700–900nm) with an excitation wavelength of 740–800nm and
emission wavelength of 800–860nm [48]. The high contrast, which is the manifestation of a high signal to noise ratio (SNR), allows for detailed visualization of
blood vessels because the high-pass lter removes the light from the light source,
while the low-pass lter allows for emitted light to be received by the sensor [49].
While there is no consensus about the optimal intravenous dose, a systematic review
found the most commonly administered total dose of ICG was 12.5mg, although
maximal doses of 1–3mg/kg have been reported [50]. ICG is hepatically metabolized and excreted through the kidneys with a half-life of 3–5min, allowing for safe
repeat administration. ICGA has been utilized in the evaluation of ap perfusion
and selection of dominant perforators with greater utility in performing perforator
aps (Fig. 9.11). ICGA is also useful in assessing microvascular anastomosis
patency and for postoperative ap monitoring.
ICGA is helpful in the assessment of ap perfusion, particularly in the setting of
questionable physical exam ndings. A study of 88 adipo- or fasciocutaneous free
aps performed with intraoperative ICGA reported a sensitivity of 100% and specicity of 98.8% [51]. Microscope-integrated ICGA can be used for early detection of
anastomotic problems. A prospective study of 50 patients undergoing free microvascular transfer found that delays in transit time through the arterial and venous
anastomoses identied using ICGA correlated with arterial or venous occlusion or
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a b
cd
e
f
g
Fig. 9.11
Ablative defect following mandibulotomy, subtotal glossectomy, resection of left lateral pharyngeal wall, left soft palate and bilateral neck dissection. (c) Tumor and neck dissection specimen.
(d) Harvest of anterolateral thigh (ALT) free ap. (e) Intraoperative indocyanine green angiography demonstrating poor perfusion of the proximal ap. (f) Planned ap modication to excise
poorly perfused portion of skin paddle. (g) Inset of ALT ap. (h) Immediate postoperative reconstruction. (i) Postoperative reconstruction at 3months demonstrating a viable ap
(a) 72year old male with a squamous cell carcinoma of the left ventrolateral tongue. (b)
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