Biomechanical Study Of Male Lower Urinary Tract Under Synergistic Action Of Internal And External Sphincter

The incidence of urinary incontinence in men is extremely high and can occur at any age.Urinary incontinence is caused by sphincter injury or nerve dysfunction.Incontinence causes the patient to lose the ability to urinate uncontrollably,resulting in the involuntary discharge of urine.Urinary incontinence not only makes patients uncomfortable,but also easily causes complications such as pressure sores.The incidence of urinary incontinence is high,but the rate of visits is low.Many patients do not have a strong sense of treatment,or shame and talk about it or think it is irrelevant,and even some patients think it is a natural phenomenon,so they cannot get timely and correct treatment.Urinary incontinence is one of the five main topics of the 22nd international congress of urology.The biomechanical study of urinary incontinence in China needs to be strengthened and deepened.The function of urinary control in the male lower urinary tract is realized by the internal and external sphincter.The normal urinary control function of the male lower urinary tract is coordinated by multiple mechanisms and cannot be achieved by the internal sphincter or the external sphincter alone.The biomechanical study of male lower urinary tract under the synergistic effect of internal and external sphincters is obviously necessary.The internal and external sphincter to achieve urinary control is mainly by the muscle to achieve the main dynamic.However,muscle has highly nonlinear viscoelastic characteristics,that is,the stress and strain change with the change of strain rate,so the validity verification should be carried out before using the muscle constitutive model.Muscle soft tissue has highly nonlinear viscoelastic characteristics,that is to say,the stress and strain change with the change of strain rate,so the validity of the musculature dynamic model needs to be verified before it is used.In this paper,a three-dimensional finite element model of rabbit tibialis anterior muscle was reconstructed to verify the model.Twelve groups of active and inactive muscle models were simulated under three different strain rates.The two models are nonlinear viscoelastic QLV and super-elastic rubber Ogden coupled with the classical Hill truss element joint respectively.By comparing the finite element simulation results in this paper with the experimental measurement results of Myers,it can be concluded that the passive part-of the muscle adopts the nonlinear viscoelastic QLV material,and the active part is the classical Hill truss element with higher biological fidelity,and the model of the muscle has strong usability.The geometric model of the lower urinary tract was reconstructed by 3d reverse software from colloidal tissue images of middle-aged men.In order to study the distribution of lower urethral pressure under the active force of internal and external sphincter,a biomechanical simulation model of the lower urinary tract including the active force of internal and external sphincter muscle was established based on the geometric model of the lower urinary tract.The sphincter model is coupled by the passive nonlinear viscoelastic QLV material and the Hill truss active element.The sphincter model was simulated under the action of the main force.The simulation results show that the maximum pressure of internal and external sphincter on urethra is within the range of clinical measurement.The maximum pressure curve of the internal sphincter and external sphincter on the urethra was then extracted.Then the pressure curve was loaded into the fluid-solid coupling analysis of the lower urinary tract.The relevant literature was reviewed and the bladder pressure of 25ms at the end of urination was determined.The pressure curve was taken as the fluid-solid coupling inlet pressure.Finally,the new model was simulated and calculated.After the simulation,the equivalent stress on the front and rear walls of the lower urinary tract urethra and the urine flow rate were extracted for analysis.The internal and external sphincter model can also be directly used to analyze the response mechanism of urodynamics such as bladder pressure and urine flow rate by fluid-solid coupling in the lower urinary tract,providing a theoretical basis for the cause of urinary incontinence.