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thermography compared to 1% (95%CI 0%-2%) for those monitored with oximetry. Furthermore, the results of
this study showed that thermography prompted a return to the operating room (OR) in 1% (95%CI 0%-73%) of
the patients compared to 5% (95%CI 3%-9%) for oximetry. Lastly, the overall complication rate was 12% (95%CI
1%-54%) for patients monitored with thermography compared to 10% (95%CI 4%-21%) for those monitored with
oximetry.

Conclusion: Ultimately, this meta-analysis concludes that while oximetry monitoring currently has strong evidence
for improving flap outcomes, trends in the current data indicate that further studies may demonstrate that
thermography may be comparable to oximetry in achieving similar patient outcomes.

Keywords: Microsurgical breast reconstruction, oximetry, thermography, flap monitoring, flap take back, flap
outcomes

INTRODUCTION
Flap failure is a devastating complication after microvascular free tissue transfer for breast reconstruction.
Despite advancements in microvascular techniques, rates of take-backs to the operating room for
complications leading to flap compromise have been reported at around 0%-10% for microsurgical breast
reconstruction [1-10] . Historically, surgeons have relied on physical examination to assess flap viability by
[11]
assessing color, warmth, capillary refill, and turgor . Physical examination is also often used in conjunction
[11]
with a handheld Doppler ultrasound . Evidence has shown that early detection of vascular compromise in
[1-8]
a threatened flap is essential for increasing rates of flap survival . Given the need for timely diagnosis,
several noninvasive methods of flap monitoring have emerged as useful adjuncts to conventional methods
of evaluation of flap compromise.

In the past, authors described the ideal characteristics of a monitoring technique that is benign to both the
patient and the free flap . They determined that the ideal monitoring method would be rapid, repeatable,
[12]
reliable, recordable, rapidly responsive, accurate, inexpensive, objective, and applicable to all kinds of
[12]
flaps . They also felt it should be equipped with a simple display that could alert relatively inexperienced
[12]
personnel to the development of circulatory impairment . Despite this thorough postulation of an ideal
system, there is no standard of care for flap monitoring devices and no high-impact evidence that favors one
technique over another.

Two technologies commonly mentioned in the literature for flap monitoring post-microsurgical breast
reconstruction are oximetry and thermography. One available device utilizing oximetric monitoring is the
ViOptix T.Ox Tissue Oximeter (ViOptix, Inc., Fremont, Calif.); this device is a noninvasive monitor of real-
time flap perfusion that uses the emission of near-infrared light to measure local tissue oxygen
saturation [13,14] . This technology has been shown to provide an increase in flap salvage rate and early
detection of flap compromise. Another monitoring method is thermal imaging or dynamic infrared
[14]
thermography (DIRT) . Thermal imaging detects infrared radiation from an object and produces an image
based on the local temperature, which can be used as a surrogate marker for cutaneous blood flow. Several
studies have shown thermography’s efficacy in preoperative planning to identify perforating vessels, but
until more recently, technological impediments limited its use . Handheld thermal imaging devices are
[14]
now commercially available (FLIRONE, Flir Systems, Inc., Wilsonville, OR) and are becoming more
affordable . Further, they can be paired with most smartphones, making this technique very appealing for
[14]
convenient postoperative monitoring . However, despite its high potential, no studies have shown DIRT
[14]
technology to be superior or comparable to other flap monitoring methods. The purpose of this systematic
review was to clarify the existing evidence regarding oximetry and thermography by comparing