Analysis of the Optimum Tapering Angle in Microanastomosis Using Computational Fluid Dynamics

Area of Science:

• Microsurgery
• Vascular Surgery
• Biomedical Engineering

Background:

• Vascular size discrepancy in free flap transfer can lead to thrombus formation.
• Tapering larger vessels is common practice, but optimal angles are experience-based.
• Computational fluid dynamics (CFD) can objectively determine ideal tapering angles.

Purpose of the Study:

• To investigate the optimal tapering angle for vascular anastomosis using CFD.
• To analyze the impact of different tapering angles on blood flow dynamics.

Main Methods:

• Simulated vessels (1.5 mm and 3.0 mm) were designed using ANSYS ICEM.
• Four anastomosis models with tapering angles of 15°, 30°, 60°, and 90° were created.
• CFD analysis using OpenFOAM evaluated velocity, wall shear stress (WSS), and oscillatory shear index (OSI) under forward and retrograde flow.

Main Results:

• Wall shear stress (WSS) was higher in the retrograde (R) than forward (F) direction.
• Oscillatory shear index (OSI) was lower at smaller tapering angles in the R direction.
• OSI values for 15° and 30° were nearly identical in the R direction.

Conclusions:

• Tapering for anastomosis reduces thrombus risk, especially with larger-to-smaller vessel flow.
• An approximate 30° tapering angle is suggested as optimal for both flow directions.
• CFD provides valuable insights for optimizing surgical techniques in vascular anastomosis.