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Ali et al. Plast Aesthet Res 2021;8:35 https://dx.doi.org/10.20517/2347-9264.2021.29 Page 5 of 15

[20]
A recent study by González Martínez et al. compared handheld Doppler, CTA, and color duplex
ultrasound (CDU). CDU and CTA had a 100% positive predictive value (PPV) for perforator identification
compared to 88.6% for the handheld Doppler. The negative predictive value for CDU, CTA and Doppler
was 100%, 94.3% and 90.56%, respectively. The majority of flaps in this study were ALT but other extremity
flaps were included. A systematic review by Cheng et al. has pooled data which included 54 ALT flaps
[21]
showing a 94.3% PPV. Another study by Thomas et al. compared CDU with Doppler in ALT flap harvest.
[3]
They showed a significant increase in septocutaneous perforator dissection which translated to nearly a
90 min reduction in harvest time.

While CDU has the steepest learning curve of the techniques discussed, it is noninvasive, inexpensive, has
no contraindications, provides detailed anatomic information, and can be adopted in any type of flap
harvest.

INTRAOPERATIVE
Contributors to successful FTT include precise surgical dissection and assessment of the harvested flap for
viability. Although experience and clinical judgement are irreplaceable tenets in microvascular surgery,
there are numerous technologies that can be applied intraoperatively for increased success and efficiency.
These technologies include the use of microvascular couplers in anastomoses, alternative and improved
microscopic and operative visualization, and technology to assess flap perfusion.

Microvascular couplers
Failure of the microvascular anastomosis is one of the primary reasons for FTT loss. Therefore, any
technology to improve this process is valuable. The ideal technique would minimize ischemia time, avoid
vessel trauma, maintain vessel patency, and be easy to perform. Historically, arterial and venous
anastomoses were performed via hand-suturing. Suturing technique certainly requires training due to the
potential for back-wall placement of sutures and poor suture placement leading to thrombosis, stenosis, or
anastomotic leaks. The conceptual design of the microvascular coupler was first described in 1962 by
[22]
[23]
Nakayama et al. and was introduced into use in 1986 by Ostrup and Berggren . The coupler design
consists of two rings with interlocking pins and corresponding holes. Each end of the vessel is passed
through the ring, pinned, and anastomosed together. Available couplers range from a size of 1.0 to 4.0 mm
(Synovis Micro Companies Alliance, Birmingham, AL).

Since the introduction of this technology, venous couplers have become widely accepted and utilized in
FTT. In a recent meta-analysis comparing outcomes for microvascular couplers to hand-sutured venous
anastomosis, microvascular couplers were found to be safe and effective. This study was not specific to head
and neck reconstruction, which represented 19% of the cases. The meta-analysis of 12,304 patients showed a
thrombosis rate of 1.47% with couplers, which was not significantly different in risk of venous thrombosis
compared to hand-sutured anastomosis. There was also a significant decreased anastomotic time and
postoperative flap failure risk . Multiple other studies have also reported consistent positive outcomes with
[24]
the use of venous couplers, including those specific to head and neck reconstruction [25-28] . In a manuscript
focusing on the time saved with use of microvascular couplers, Rozen et al. concluded a significant
[29]
reduction in venous anastomotic time when coupling (4 min) compared to suturing (22 min) without an
increase in complications. In situations where end-to-side coupling is required (typically to the internal
jugular vein stump or vein proper), DeLacure et al. found that they were able to successfully complete the
[30]
venous anastomosis via the coupler in 33 of 37 (89%) attempted cases. While the authors did find additional
challenges in coupling to a previously radiated or dissected vessel, with technical modifications they were
able to largely avoid having to convert to suture technique.