Research On Mechanism Designs And Experiments Of Puborectalis-Like Artificial Anal Sphincter

Continence refers to the ability to maintain solid or liquid stools and flatus not only in various positions but also during physical exercise,whereas fecal incontinence(FI)is the loss of this ability.FI is a symptom,and it is characterized by multiple etiologies and variety severity.Because FI is such a disease which is hard to cure and inconvenient to care,the negative psychological effects,social stigma and reduced quality of life can be devastating for patients who suffer from it.The prevalence of FI is distributed in all age groups.Usually,the older the human is,the higher the prevalence is.In addition,the incidence of FI in the general population is showing an increasing trend in recent years.The available treatments for FI including both conservative and surgical procedures,but neither of them is ideal for severe FI.The appearnce of artificial anal sphincter(AAS)provides a new solution for the cure of severe FI.However,the existing AASs used in clinical practice have showed high failure rate of equipment and serious complications,which suggest that it's necessary to make further improvement to AAS.Based on the bionics design method,the thesis developed the Puborectalis-like Artificial Anal Sphincter System.The main work and achievement of this thesis can be summarized as follows:1.Two generations of sphincter prosthesis based on three-ring structure are designed by imitating the structure and function of the Puborectalis.The stable transmission mechanism driven by motor can provide sufficient torque as much as 2N·m in 10s to maintain continence;the sealing solution has a good waterproof performance in 80cm deep water;and the volume and weight of all implants are reduced to 127cm~3 and 88g,respectively.2.The flexible intestinal pressure sensor is designed.The pressure sensor can not only detect the closing pressure of the intestine applied by the prosthesis and the expanding pressure of the rectum,but also work as a part of sealing solution to prevent leakage.3.The triple limit mechanisms including the Hall switch,motor over-current protection and gear with limited teeth are designed to ensure the safety of intestinal blood supply.4.The hardware and software design of the system are improved.The use of the gating switch instead of the instrument op amp simplifies the circuit structure and reduces the system power consumption.The remote controller can remind the patient to defecate voluntarily.5.The in-vitro and in-vivo experimental studies are performed.Through calibration experiment,it is obtained that there a linear relationship between input and output of pressure sensors,and the mechanism transmission efficiency of prosthesis is 49~59%.The in-vitro experiments show that there there is also a linear relationship between the rotation angle of prosthesis and the effect of maintaining contenience.When the rotation angle is 56°,the appropriate threshold for maintaining contenience is 3.9 kPa and that is suitable for stimulating bowel movement is 2.8 kPa.Finally, the in-vivo experiment based on miniature pig model helps to verify the feasibility and biosafety of the system.