Preliminary Evaluation of Hemodynamic Effects of Fontan Palliation on Renal Artery Using Computational Fluid Dynamics

Background:The assessment of renal function is important to the prognosis of patients needing Fontan palliation due to the reconstructed compromised circulation.To know the relationship between the kidney perfusion and hemodynamic characteristics during surgical design could reduce the risk of acute kidney injury(AKI)and the postoperative complications.However,the issue is still unsolved because the current clinical evaluation methods are unable to predict the hemodynamic changes in renal artery(RA).Methods:We reconstructed a three-dimensional(3D)vascular model of a patient requiring Fontan palliation.The technique of computational fluid dynamics(CFD)was utilized to explore the changes of RA hemodynamics under different possible blood flow rates.The relationship between the kidney perfusion and hemodynamic characteristics was investigated.Results:The calculated results indicated the declined tendency of the pressure and pressure drop as the flow rate decreased.When the flow rate decreased to two-thirds of its baseline,both the pressure of left renal artery(LRA)and the pressure of right renal artery(RRA)dipped below 50%,and the pressure of RRA fell more quickly than that of LRA.Uneven distribution of WSS was observed on the trunk of RA,and the lowest WSS was found at the distal of RA.The average WSS in RA dropped to around 50%as the flow rate reached one-third of its baseline.Conclusions:As a promising approach,CFD can be utilized to quantitatively evaluate the hemodynamic characteristics of RA and contribute to offsetting the drawbacks of clinical assessments of renal function,to help realize better prognosis for the patients with Fontan palliation.

Biomechanical finite element analysis of typical tibiotalar arthrodesis

Tibiotalar arthrodesis(TTA)is a common surgical method for post-traumatic arthrosis and primary osteoarthrosis of ankle.Internal screw fixation exhibits such advantages of higher fusion rate and fewer complications that it has become the mainstream surgical procedure in clinics.However,there are still disputes over the choice of screw type,number and nailing method.In this study,a 3D model of tibiotalar joint was established based on CT data.Two representative types of screws were modeled according to their real objects.Preprocessing was done in Hypermesh 2017,and the finite element simulations of different surgical schemes and postoperative ankle joint movements were performed via Abaqus 2016.The stress distribution in tibiotalar joints and screws,interarticular displacement,and screw deformation were extracted for comparative analyses.The results show that:(1)the three-screw fixation scheme with smaller displacements and higher contact pressure is superior to the two-screw one;(2)the relative displacements of the tibia and talus of full-thread screw under all loads were reduced by approximately 50%compared with those of lag screw,showing better stability;(3)the 60
scheme is more favorable for joint fusion and more stable under vertical load,while the 75
has the best bending resistance;(4)the stress and strain distributions in screws indicate that the screw break is most likely to happen near its contact region with the bone inlet,the maximum stress reaches 212.2 MPa.This study is of great significance for the selection and optimization of the surgical plan.