PURPOSE Using the computational fluid dynamics to analyse the alteration of flow field of free forearm flap with 4 different venous anastomotic techniques, and to preliminarily explore its clinical significance. METHODS Three dimensional geometric models of radial forearm flap with 4 types of anastomotic techniques between radial vein and recipient vessels were established by Pro/E (Wildfire 4.0) as follow: type I(matched anastomosis), type II(stump anastomosis), type III (angular anastomosis) and type IV(end-to-side anastomosis). Then the established geometric models were transferred to the SC/Tetra 8.0 software for mesh generation and calculation. Porous model was applied to the flap to simulate capillary structure as before, inlet velocity of radial artery was set as 20mm/s and outlet pressure of recipient vein as 0 Pa. By comparing pressure and velocity distribution on different cross sections of blood vessels, hemodynamic feature of the flap with 4 types of anastomotic techniques was studied, focusing on the alternation of flow field of drainage system of the flap, especially at the anastomotic sites. The data was analysed using SAS8.0 software package for ANOVA. RESULTS The pressure on the four sections of the flap circulatory system was significantly higher in type I compared with type II, III and IV (F=40.99,P<0.001). Type II presented with vortex in the anastomotic site, and type III,IV with smooth flow. Type IV had an absorption effect at the anastomotic site. The pressure loss of the flap circulation was maximal in the radial vein of vascular pedicle(F=97.00,P<0.001). CONCLUSIONS Type III and IV are considered appropriate techniques to deal with caliber discrepancy of recipient site. Theoretically, reasonable reduction of the vascular pedicle length and choice of the concomitant radial vein with wider radius for anastomosis can effectively decrease the resistance of circulation in the flap.

中文翻译：

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四种静脉吻合技术对前臂皮瓣流场的计算流体力学分析

目的利用计算流体力学分析4种不同静脉吻合技术对前臂游离皮瓣流场的改变，并初步探讨其临床意义。方法采用Pro / E（Wildfire 4.0）建立radial骨前臂皮瓣的三维几何模型，并在vein静脉和受体血管之间采用四种吻合技术，分别为：I型（吻合吻合），II型（残端吻合），III型（角形吻合）和IV型（端对侧吻合）。然后将建立的几何模型转移到SC / Tetra 8.0软件中，以进行网格生成和计算。皮瓣采用多孔模型模拟毛细管结构，radial动脉入口速度设定为20mm / s，受体静脉出口压力设定为0Pa。通过比较不同血管横截面的压力和速度分布，采用四种吻合技术研究了皮瓣的血流动力学特征，重点研究了皮瓣引流系统的流场变化，特别是在吻合部位。使用用于ANOVA的SAS8.0软件包对数据进行了分析。结果I型皮瓣循环系统四个部分的压力明显高于II，III和IV型（F = 40.99，P <0.001）。II型在吻合部位出现涡旋，III，IV型则流动顺畅。IV型在吻合部位有吸收作用。血管蒂的radial静脉中皮瓣循环的压力损失最大（F = 97.00，P <0.001）。结论III型和IV型被认为是解决接收方口径差异的适当技术。从理论上讲，合理减少血管蒂长度和选择较大半径的伴生radial静脉进行吻合可以有效降低皮瓣的循环阻力。