Objective To evaluate initial experience with shape memory alloy stent as an alterative to colostomy in patients with intestinal obstruction of rectal cancer. Methods Twenty-one patients with acute and chronic rectal obstructions from malignant causes underwent stent placement. After rectal stent was slenderized in ice water, it was inserted into the strictured rectum by hand or sigmoidoscope. Nitinol mesh stent were deployed in hot water. Results Eighteen patients who had underwent rectal stent placement achieved clinical decompression within 5 hours. Colostomy underwent in 3 patients due to stent failure. Eighteen patients with stent were followed-up, 14 cases died in 56-720 days and 4 other cases were still alive without intestinal obstruction in 2-15 months. Conclusion Nitinol mesh stent may be useful in the management of terminal or high-risk surgical patients for palliative purposes shuning colostomy. Palliation of stent combined with chemotherapy and immunotherapy can be performed to improve survival.
【Abstract】Objective To study the advances in clinical application of shape memory alloy (SMA) in general surgery. Methods The literature in the recent years on the advances of SMA was reviewed. Results At present clinical application of SMA have been developed. Different stents could dilate the benign and malignant stricture of blood vessels, biliary ducts, cola, recta and gastric outlet obstruction. The SMA catheter system was effective for peroral cholangiopancreatoscopy. Novel nitinol basket instrument might be useful for percutaneous cholecystolithotomy. Compression anastomoses was safe and sound in gastrointestinal surgery using a device made of SMA. Nitinol stent could be used in transjugular intrahepatic portosystemic stent shunt (TIPSS) with satisfactory results. Nitinol occlusion devices was superior to stainless steel coils. The Simon nitinol filter represented a new generation of venous interruption devices designed to prevent recurrent pulmonary embolism. Conclusion Clinical application of SMA will be increased by the development of endoscope, laparoscope and interventional technique.
The locking mechanism between bracket and shape memory alloy (SMA) archwire in the newly developed domestic orthodontic device is the key to controlling the precise alignment of the teeth. To meet the demand of locking force in clinical treatment, the tightening torque angle of the locking bolt and the required torque magnitude need to be precisely designed. For this purpose, a design study of the locking mechanism is carried out to analyze the correspondence between the tightening torque angle and the locking force and to determine the effective torque value, which involves complex coupling of contact, material and geometric nonlinear characteristics. Firstly, a simulation analysis based on parametric orthogonal experimental design is carried out to determine the SMA hyperelastic material parameters for the experimental data of SMA archwire with three-point bending. Secondly, a two-stage fine finite-element simulation model for bolt tightening and archwire pulling is established, and the nonlinear analysis is converged through the optimization of key contact parameters. Finally, multiple sets of calibration experiments are carried out for three tightening torsion angles. The comparison results between the design analysis and the calibration experiments show that the deviation between the design analysis and the calibration mean value of the locking force in each case is within 10%, and the design analysis method is valid and reliable. The final tightening torque angle for clinical application is determined to be 10° and the rated torque is 2.8 N∙mm. The key data obtained can be used in the design of clinical protocols and subsequent mechanical optimization of novel orthodontic devices, and the research methodology can provide a valuable reference for force analysis of medical devices containing SMA materials.