Medical applications of nickel-titanium memory alloys

Esophageal stricture. The main symptom of benign and malignant esophageal strictures is dysphagia. In severe cases, it can cause malnutrition or reflux and aspiration pneumonia. Previous treatment methods include surgery, stricture dilation, endoscopic treatment (laser, microwave and high-frequency electrosurgical surgery) and metal stent placement. These treatments all have certain advantages and disadvantages. Compared with other surgical, endoscopic and metal stent treatments, NT-SMA is corrosion-resistant, wear-resistant and biocompatible. It also has a unique shape memory function; no open surgery is required; no excessive expansion is required. , the risk of perforation is small; the restoring force of nickel-titanium memory alloy can produce continuous and gentle expansion of the esophageal tissue; and NT-SMA is easier to remove when drinking ice water.
In 1993, Dong Zongjun et al first reported the use of nickel-titanium alloy esophageal supports to treat 8 cases of benign esophageal stricture. Except for 3 cases of long-segment esophageal scar stenosis caused by chemical burns, the treatment effect was not good, and the symptoms of the other 5 cases were relieved. The longest observation period was 11 months without adverse reactions. Wu Xiong et al. used a nickel-titanium memory alloy double bell-mouthed coiled tube stent to treat 9 cases of esophagogastric anastomotic stenosis after esophageal cancer resection. Postoperative barium swallow examination showed that the barium could pass through the stent smoothly, and there was no obstruction when eating rice or soft food. Except for one case where the anastomosis was loose and the stent slipped into the stomach and was removed through gastroscopy, the other eight cases were followed up for 5 to 7 months. They could eat chewed food smoothly without obvious discomfort, and their physical fitness was significantly improved. He found that patients who used larger-diameter stents had better patency than patients who used smaller-diameter stents for eating.
Indications for placement of nickel-titanium memory alloy:
① Esophageal stricture and obstruction caused by esophageal cancer, and stricture after radiotherapy for esophageal cancer;
② Esophageal stricture caused by physical or chemical burns;
③ Esophageal airway fistula, esophageal mediastinal fistula (use membrane-coated NT-SMA stent). Contraindications:
①Severe cardiac and pulmonary insufficiency;
②Patients who cannot swallow on their own;
③The stenosis site is higher than the seventh cervical vertebra level.
Tracheal stenosis caused by advanced tumors; the stenosis segment is long or has multiple stenosis; patients who are older or in poor health are not suitable for surgery. The main disadvantages of placing a T-tube are that the stent cannot deform and is difficult to place; it is prone to displacement and local damage; secretion blockage often occurs; the T-tube has poor flexibility and is not suitable for lower tracheal stenosis. NT-SMA better solves the above problems. After deformation, it can be placed in narrow areas through a small cavity; after reshaping, it is closely attached to the tracheal wall and fixed well; it has good biocompatibility and is good for tracheal mucosa. There is no obvious damage and can be placed for a long time; the high resilience allows it to adapt to the bends of the trachea and can be placed in various sections of the trachea. In 1993, Liu Yang et al. placed NT-SMA stents in 7 dogs after causing tracheal stenosis and observed them for 2 to 6 months. The results show that the stent can be placed in granulated and scarred tracheal stenosis areas without causing severe inflammatory reactions or irritation symptoms, and without obstruction caused by secretion attachment or granulation tissue proliferation. The surface of the stent is smooth and clean, with no displacement or deformation, showing good biocompatibility. On the basis of animal experiments, one case each of severe tracheal stenosis and tracheal anastomotic stenosis caused by advanced tracheal tumors was treated, and satisfactory therapeutic effects were obtained. In animal experiments by Pei Shigeng and others, NT-SMA stents were inserted into the trachea and myocutaneous flaps were used to repair tracheal defects. Experiments show that the NT-SMA stent has good support effect on the trachea.
Indications for placement of nickel-titanium memory alloy:
① Tracheal stenosis caused by advanced tracheal, bronchial, thyroid, esophageal or mediastinal tumors, inoperable and requiring life extension;
②Tracheal wall collapse after laryngeal and tracheal reconstruction; ③Tracheal and bronchomalacia;
④Those whose physical condition cannot tolerate surgery.
Vascular embolism. In 1974, Sokoloff et al. first reported the successful treatment of 2 cases of epistaxis with percutaneous intra-arterial gelfoam embolization, creating a new world of treating epistaxis with angiography technology. After extensive clinical practice, conventional angiography has been developed into DSA, which is used by many scholars for preoperative embolization of epistaxis and head and neck vascular tumors. Commonly used embolization materials include gelatin sponge, polyethylene sponge, stainless steel balls, and silica gel particles. First, these materials are limited by the caliber of the catheter and are difficult to release; second, they are difficult to embolize larger blood vessels. In 1977, Simon et al. used NT-SMA to make a thrombus filter and implant it into the inferior vena cava of dogs, and found that it had no toxic or side effects on the animals. In 1992, Zhang Chuncai and others used NT-SMA to make a vascular embolization device. After experimental research on embolization of 39 target arteries in 20 dogs, they found that the sponge plug made of NT-SMA has:
①Release is simple and safe;
②The embolization effect is rapid and reliable;
③Suitable for embolization of larger diameter blood vessels;
④ Experiments have proven that the organizational compatibility of NT-SMA is better than that of stainless steel. NT-SMA can be used as a better embolization material for clinical embolization treatment. Ma Genshan et al also reported that the NT-SMA endovascular stent has good biocompatibility and no obvious toxic or side effects.