Sudden Expansion Promotes Flow Stagnation in Microvascular Anastomosis: Is it Time to Rethink the Venous Coupler?

Document Type

Conference Proceeding

Publication Date

9-2026

Publication Title

Plastic and Reconstructive Surgery. Global Open

Abstract

Objective: Microvascular anastomoses are particularly sensitive to alterations in flow dynamics as evidenced by decreased flap success rates in end to side and disturbed vessel lumen architectures. Fluid flows are significantly affected by rapid changes in lumen diameter such as those seen with venous coupler applications in size mismatched vessels. The aim of this study is to identify the relationship between vessel size mismatch ratios and flow stagnation and propose alternative flow coupler designs for optimization of flows in scenarios of mismatch.

Methods: Computational fluid dynamic (Ansys, Fluent R1 2024) models were created to simulate sudden expansion of end-to-end microvascular anastomoses. Model assumptions included blood as a Carreau Newtonian fluid under laminar flow. Five models were created representative of anastomoses with the following vessel size mismatches (VSM): 1mm to 2mm, 1mm to 3mm, 1mm to 4mm, 2mm to 3mm, and 3mm to 4mm. An additional model was utilized to assess the effect of venous coupler modification on fluid dynamics. Specifically, the use of intraluminal projections for the purposes of turbulence and boundary layer prevention. Post-processing analysis was completed using visualizations of fluid flows and line integral convolution plots.

Results: The cross-sectional areas of blood stagnation increased with the ratio of sudden expansion in a logarithmic relationship (R^2 = 0.989). The area of stagnated flow for a VSM ratio of 4 was 81.84% compared to 26.59% for a VSM ratio of 1.33. Qualitative assessment of reversed flow shows significant increases with VSM ratio. Alteration of the anastomotic lumen for VSM ratio of 4 with a modified venous coupler device decreased stagnation from 81.84% to 56.21%.

Conclusion: Sudden expansion in microvascular anastomoses promotes blood stagnation and reversal. Strategies to mitigate this phenomenon, such as additions to the venous coupler device, are an important area of future investigation.

Volume

14

Issue

Suppl 4

First Page

25

Last Page

26

Comments

Michigan Academy of Plastic Surgeons 34th Biennial Scientific Meeting, July 12-15, 2026, Mackinac Island, MI

DOI

10.1097/01.GOX.0001276816.71317.b2

ISSN

2169-7574

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