| Lower urinary tract diseases and traumatic urethral injuries are more and more common in life and become one of the important factors that endanger human health.Nowdays,urinary tract obstruction diseases’ check methods are mostly based on urinary flow rate,pressure and other invasive urine dynamics test,can cause psychological and physiological adverse effects on patients,and these methods will be during the detection of patients with cough,sneeze and other violent behavior and the influence of psychological state,so it is necessary for the biomechanical study of the urinary tract,urinary tract under perfect model,provide theoretical guidance for the modern medicine.At present,there are many problems in the lower urinary tract model,such as the simplification of the material model,the inaccuracy of physical model,and most importantly,the imperfection of the urinary control mechanism,without considering the mechanical response of the urinary control process.The objective of this paper is to establish a high fidelity finite element model of the male lower urinary tract with muscular main dynamic response to the lower sphincter,to achieve fluid-solid coupling simulation analysis of the urine and the lower urinary tract under the effect of bladder pressure,and to analyze the biomechanical performance of the lower urinary tract model under the effect of the main dynamic effect of the lower sphincter.In this paper,the mechanical properties of skeletal muscle are studied,the finite element model of skeletal muscle is established,the finite element simulation method,material model and its parameters are determined,and the accuracy of the model is verified.Then,based on the continuous paraffin-embedded biopsy images of the male lower urinary tract,a complete geometric model of the male lower urinary tract was established,including bladder,prostate,sphincter,urethra and urine.By means of kriging interpolation,the finite element model of skeletal muscle is mapped to the lower sphincter,and corresponding material parameters are given to other lower urinary tract organs and tissues except the lower sphincter.The pressure curve is the dynamic pressure curve in the urination period,and the fluid-solid coupling simulation calculation of the finite element model of the lower urinary tract is completed.The parameters of urethra pressure curve and urine flow rate in the phase of micturition were validated and analyzed.Based on the analysis and verification of the results,we find that the finite element model is established by the coupling of beam element and solid element common joint to represent the skeletal muscle’s main power and principal power respectively,which is a feasible and effective simulation method.By using kriging interpolation method to control the material parameters of the finite element model,the finite element model of the lower urinary tract has a certain validity.The analysis of the urine flow rate indicated that the urine flow rate at the sphincter was the highest during the control of urine,reaching 1.262m/s at 2.5s,and the flow rate at the outlet of the bladder neck and urethra was also relatively high,reaching 0.9784m/s at 2.5s.The analysis of urethral displacement shows that the displacement at the lower sphincter is the largest at the lower end of the urethra,and the displacement is 0.764mm when it is close to the 2.5s.The analysis of urethral shear stress showed that the wall shear stress of the sphincter was higher than that of the sphincter,and the value of shear stress was up to 1.8pa.The overall shear stress of the urethra at other locations was uniform,averaging about 0.7pa.Although the model developed in this paper can provide certain basis for the detection of urinary tract diseases and postoperative prediction,there are still some problems in the model,which need further study and discussion. |
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