Smaller-diameter Anastomotic Coupling Devices Have Higher Rates of Venous Thrombosis in Microvascular Free Tissue Transfer
Summer E. Hanson, MD, PhD, Patrick B. Garvey, MD, Nihanth Palivela, none, Charles E. Butler, MD.
The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
Purpose: Free tissue transfer requires microsurgical anastomosis of an artery and vein between the donor and recipient vessels. While the standard technique is to hand sew the arterial anastomosis, anastomotic coupling devices have become popular for venous anastomosis. Coupling devices range in diameter from 1.5 mm to 4.0 mm in 0.5-mm increments. It has been suggested that smaller coupling devices increase the risk of anastomotic thrombosis; however, the relationship between coupler size and venous thrombosis rates has not been adequately evaluated. We hypothesized that smaller-diameter coupling devices are associated with higher rates of venous thrombosis in free tissue transfer.
Methods: We retrospectively reviewed data prospectively entered into a central departmental database for consecutive patients who underwent microsurgical free tissue transfer at a single center between 2001 and 2011. The primary outcome measured was the relationship between venous coupler diameter and the rate of venous thrombosis. The secondary outcome was the venous anastomotic thrombosis rates for anastomotic couplers versus hand-sewn venous anastomoses.
Results: A total of 5,634 consecutive free flap reconstructions were evaluated, with 3,292 coupled venous anastomoses (57.9%). Flap types included abdominal-based free flaps, anterolateral thigh flaps, free fibula flaps with or without a cutaneous paddle, radial or ulnar artery forearm flaps, latissimus dorsi flaps with or without a cutaneous paddle, and other, rarely used, flaps (e.g., jejunum, serratus anterior, and gracilis flaps). Flaps were grouped according to the six different venous coupler sizes used (1.5, 2.0, 2.5, 3.0, 3.5, and 4.0 mm). The overall venous thrombosis rate in the study was 1.3%, and there was no difference in the thrombosis rate between coupled and hand-sewn venous anastomoses (1.4% versus 1.1%, respectively, p=0.53). Total flap loss due to venous thrombosis was 0.3%, representing an 87% salvage rate. The 1.5-mm-diameter coupler thrombosis rate of 4.76% was significantly higher than that of the 2.5 mm (1.34%, p=0.02), 3.0 mm (1.15%, p=0.01) couplers and the hand-sewn anastomoses (1.1%, p=0.01) and higher than the 2.0 mm (1.52%, p = 0.07), 3.5 mm (1.85%, p=0.08) and the 4.0 mm (1.57%, p = 0.1) although these differences did not reach statistical significance.
Conclusions: This study is the largest to date that specifically compares diameter size of venous anastomotic coupling devices in all types of microvascular free tissue transfer. Due to our retrospective study design, we were unable to control for the diameter of the vein, but our surgeons’ typical practice was to select the maximum coupler diameter that would fit the smaller of the two veins being anastomosed, whereas the majority of the hand-sewn anastomoses were performed prior to the
venous coupler being available at our institution. We found a more than three-fold higher rate of venous thrombosis with the 1.5-mm-diameter coupler compared to the larger-diameter devices and to hand-sewn venous anastomoses. This evidence suggests that surgeons should choose an outflow vessel that does not require a coupler diameter smaller than 2.0 mm or perform a hand-sewn anastomosis in situations where this is not possible.
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