Reducing Fat Necrosis in Free Flap Breast Reconstruction with the SPY System

Purpose: This study aims to determine if the intraoperative use of laser-assisted indocyanine green (ICG) fluorescence angiography affects postoperative fat necrosis through a multivariable analysis of 409 DIEP free flaps for breast reconstruction.

Methods: A retrospective review was performed on free flaps for breast reconstruction at a single center from 2010-2016. Inclusion criteria ensured that only single pedicle deep inferior epigastric artery perforator flaps with a single artery and venous anastomosis to the cranial internal mammary vessels for both unilateral or bilateral breast reconstruction were analyzed. ICG was used after the flap had been anastomosed on the chest to subjectively assess for areas of hypoperfusion if there was clinical concern. Less commonly, it was utilized to subjectively assess perforator quality on the abdomen if there was a discrepancy with clinical findings versus the preoperative CT angiography.

 A univariable logistical regression analysis was first conducted on the use of ICG angiography along with 27 other patient demographic and surgical factors including row of perforator, perforator diameter, perforator number, flap weight, and the year the surgery. From this, an odds ratio (OR) with 95% confidence intervals of the effect on DIEP flap fat necrosis was derived for each variable. All variables with a p< .15 for the calculated OR in univariable analysis were then entered in a backward selection algorithm to yield the parsimonious multivariable logistic regression model. This subsequent multivariable analysis was done to determine if ICG angiography had an independently significant effect on fat necrosis when other conceivable confounding factors, which were significant in the univariable analysis, were included.

Results: 409 total DIEP flaps were included in both univariable and multivariable statistical analyses. The average age of the patients was 50.5 years old. The average BMI of the patients was 30.7. The average follow up for these patients was 18.5 months, with a median of 15.75 months. 14.4% of flaps had fat necrosis in total.

Intraoperative ICG angiography was used for 130 flaps (31.8%) and was independently associated with a decrease in the odds of fat necrosis (OR .46, p-value= .04). ICG angiography directly guided excision of hypoperfused areas in 50 flaps (38.5%), ensured the presence of adequate perfusion in 78 flaps (60%), and identified a pedicle kink after anastomosis in 2 flaps (1.5%)

Prophylactic excisions of the flap without using ICG angiography were done in 107 flaps (26%) and did not affect fat necrosis rates (OR 1.74, p-value = .1). The average weight of the resected portion of flaps without ICG angiography was 250.8 grams, whereas the average weight of the resected portion of flaps with ICG angiography was 152.3 grams. This 98.5-gram per flap difference was statistically significant (p-value= .01). 

Conclusions: Our results indicate that intraoperative laser-assisted ICG fluorescence angiography decreases the odds of fat necrosis in DIEP flap breast reconstruction by guiding a more accurate flap debulking at inset. This can save an average of 98.5 grams of tissue per flap when compared to excising areas of hypoperfusion by just clinical signs alone.