Since Dotter first reported a new approach to endoprosthesis for the treatment of vasoembolic diseases, various stent research, development and clinical use have been widely advanced and developed in the last decade. In the treatment of vascular disorders, the structural and physical properties of various endostents are directly related to the success or failure of treatment. For example, poor ring tension of endovascular stents will lead to incomplete expansion and complication of restenosis or even occlusion, requiring further balloon expansion or superimposed stenting and surgical treatment, and even occlusion after treatment with ultra-hard Palmaz stents when the balloon is not fully expanded or the external pressure is too high has been reported. It has been demonstrated that the stability of stent is inversely correlated with low flexibility, with less morphological changes, less epithelial value added by high annular tension and less chance of stenosis occlusion. Li Maoquan, Department of Interventional Medicine, Shanghai Tenth People’s Hospital At this stage, most of the time the clinical stent release relies on the personal experience of the surgeon, and few scholars have systematically studied the influence of the underlying mechanical and physical properties of the endovascular stent on the treatment. These specific parameters include: the annular tension of the stent, i.e. the parameter that evaluates the ability of the stent to withstand the applied pressure, the flexibility and pushing force, important indicators for evaluating the stent system through the twisted intravascular, and the X-ray permeability, a key indicator for evaluating the positioning of the stent and supervising the whole release process. Currently, common domestic stents can be divided into stainless steel and nickel-titanium alloy by their materials. Stainless steel spring-ring stents include: Palmaz stents (Cordis; Johnson and Johnson Warren, NT), Perflex stents (Cordis; Johnson and Johnson), and AVE bridge stent types (Arterial Vascular Engineering. Richmond, BC, Ganada), Nitinol stents including: Memotherm stents (Angiomed/Bard, Karlsruhe, Germany), Symphony stents (Boston Scientific Vascular, Natick, MA), and S.M.A.R. T stent (Cordis; Johnson and Johnson). Also Wallstent (Schneider, Zurich, Switzerland and Boston Scientific Vascular). The author synthesizes the domestic and foreign literature and describes in detail the following three basic physical properties of the commonly used stent of 4 cm in length: the bearing force or bracing force of the stent ring, ii flexibility, and iii opacity, for the reference of domestic colleagues in clinical treatment, and also discusses the disposal of stent misplacement and displacement based on the physical properties and the author’s meager experience. I. Bracing force of the stent The bracing force of the stent ring of the current common balloon self-expanding stent is shown in Table 1, where the bracing force of the AVE Bridge X stent is the strongest among all stents, with an average value of 28.9 N/cm until collapse. It was 54% stronger than the Palmaz stent. However, Stephen reported that three of the ten AVE Bridge X brackets collapsed in half when testing the bracket’s bracing strength, and the fracture was at the midpoint of the weld, while similar severe damage was not found in any of the other types. The difference was not statistically significant. However, when comparing the brace strength per unit length, the Palmaz brace (125 N/cm*g) was superior to the conventional AVE Bridge X brace (87 N/cm*g) in comparison, and similar to the super stiff AVE Bridge X (131 N/cm*g) brace. The other stents in the group had unit values of bracing between 75 and 99 N/cm*g. The stability and bracing of the stents depended on the following factors: 1 the way the stent was designed; 2 the material of the stent; 3 the weight of the stent; 4 the length of the stent; and 5 the diameter of the stent. Since all balloon self-expanding stent sets were composed of stainless steel material, we studied the bracing force of different stents expanded to the same diameter (8 mm), and by measuring the bracing force of the stent in relation to the length and weight of the stent, we concluded that the way the stent was designed was the only factor causing the different bracing force of the stent. The results of various statistical tests given in Table 2 showed a P level of stent force at balloon self-expansion of .05. The Palmaz large stent showed a significant difference in force compared to the Palmaz medium size stent and the Perflex stent. II. Annular tolerance/chronic dilatation force Among the self-expanding stents, the annular tolerance of Wallstent was 0.39 N/cm. the annular tolerance of Memotherm stent and Symphony stent were basically the same, 1.27 N/cm and 1.36 N/cm, respectively. the chronic dilatation force of S.M.A.R.T stent was 1.7 N/cm. the chronic dilatation force should be consistent with the annular tolerance. The chronic dilatation force of Wallstent was 0.16 N/cm, which was the lowest of all stents. The highest chronic expansion force was 0.31 N/cm for the S.M.A.R.T stent. Statistically, all the self-expanding stents showed different radiation tolerance and chronic expansion force. III. system propulsion force All stent pushing systems passed through the bifurcation of the vessel in the cargo stent state without lubricant. the stent release system of Perflex used the highest propulsion force and the AVE Bridge stent had relative propulsion force for the criterion of flexibility. With the exception of the S.M.A.R.T stent, the self-expanding stent required a higher propulsive force through the bifurcation than the Perflex stent and the AVE Bridge stent, which may require a more flexible vascular release sheath. the Palmaz-Schatz medium-length stent propulsive force was very similar to that of the self-expanding stent system. Table 3 summarizes the results of multiple stents statistically tested for propulsion force at a P level of 0.05, with the exception of the S.M.A.R.T and Perflex stent pushing systems, which had comparable propulsion force across different types of stent pushing systems IV. Impermeability Stents with good impermeability, in Stenphen’s experiments with impermeability, were the lowest in the wire material group with the Palmaz In another group of NiTi alloy, consisting of S.M.A.R.T stent, Perflex stent and Wallstent stent, the opacity coefficients ranged from 99.7 to 102.7. The last group consisting of Palmaz medium-length stents, AVE Bridge X stents and Memotherm stents has a coefficient between 108.3 and 114.7. However, stents with high opacity (Palmaz large stents) were only higher than 24% for AVE Bridge stents at low x-ray doses. V. Clinical implications of studying the physical properties of stents Endovascular stent release is becoming increasingly widespread, with significant irregular stenosis due to arterial entrapment or intra-arterial plaque and acute or imminent revascularization being the main indications for endovascular stent release. The same applies to restenosis and to improving patency after vascular balloon angioplasty. The physical properties of stents are closely related to their efficacy, but the biological evaluation of stents is difficult and the majority of stents used in interventions have not been completed. In 1993, studies on the stability of metallic stents were not able to concisely count the tolerance of the Palmaz stent and had dealt with stents that could no longer be used intravascularly, such as the Strecker stent. 1994, Flueckier reported additional information on the properties of metallic stents. values. However, at that time the authors only considered it to be related to stent design. The design of the model stainless steel stent is beneficial for both the bearing capacity and flexibility of the stent’s ring. Because of the model bracket release, excellent flexibility, shapeability and moderate price, it is widely used in Europe. The purpose of this study was to demonstrate about the selection of stents with different characteristics to help in specific clinical situations. The total stent weight, flexibility, and opacity of the different stents were used as metal indications. The tolerance in the balloon-expandable stent ring is considered to play an important role, and the radiological tolerance is as important as the chronic expansion force to test the self-expandable stent. Because of the different expansion behavior at release, balloon-expandable and self-expandable stents should be separated when estimating the underlying physical properties of endovascular stents. Balloon-expandable stents will deform irregularly if the applied force exceeds the maximum bracing force of the stent. Self-expanding stents may also collapse when the applied force exceeds the annular tension. However, when the external guiding force is lower than the annular tension of the self-expanding stent, the stent will return to its original shape again. Because of the tendency of balloon-expandable stents to collapse, this type is not suitable for use in the neck of carotid arteries and progressively larger abdominal aortic aneurysms. This is the reason why we estimate balloon-expandable stents and self-expandable stents separately. The typical balloon-expandable stent is the Palmaz stent, which has a higher force of 12.8 N/cm to 18.8 N/cm. 17.9 N/cm for the Palmaz large stent and 18.8 N/cm for the Palmaz small stent, with no significant difference between the two, because the angle of the attachment point of the conventional Palmaz stent (4-9 mm ) is wider than the diameter of the bracket itself (8 mm), while it is larger than the diameter of the large Palmaz bracket. Such results were reported by Lossef and his colleagues in 1994. Regarding the release position of the Palmaz stent in the subclavian artery. The “nutcracker” position, between the first rib and the clavicle, may cause the balloon stent to be exposed to external pressure that collapses it. However, self-expanding stents have the same disadvantage in this position, when the fully expanded diameter is slightly larger than the diameter of the externally pressurized vessel. There have been reports of ineffectiveness of the Wallstent stent in superior vena cava syndrome, as well as collapse of the Palmaz stent in the bronchial system during folding and collapse of the Cimino shunt. The recently introduced AVE Bridge X, also a balloon-expandable stent, exceeds the support of the Palmaz by 54% (28.9 N/cm vs. 18.8 N/cm), but the high support of this stent decreases significantly on both sides. The higher the stiffness of the endovascular stent material, the more difficult it is to change its morphology during stent insertion, the longer the procedure and thus the greater the chance of thrombosis. The concept of mismatch compliance is applicable to intra-arterial stent placement. It can be speculated that the proposed mismatch compliance may increase the stiffness between the stent and the artery. 3 out of 10 AVE Bridge X stents tested for stiffness were broken in half due to their high stiffness and the high pressure acting right at the weld point, which may be the reason for the cutting inside the stainless steel stent. When the bracket expansion is incomplete or bounces, a coaxial stacked bracket should be used to increase the bracing force of the bracket. The optimal bracing force remains unclear and varies considerably from stent to stent. Tantalum stent endoplasia is dependent on stent stiffness. However, Wallstent endoplasia is independent of the annular bracing force of the stent. Another important property is the propulsive force. Flexible stents are better able to pass through twisted vessels. palmaz type stents shorten and are stiffer when expanding, so they are more difficult to cross vessels and may damage large vessels. However, in clinical applications, the appropriate stent selection is based on its own flexibility and the propulsive force of the release system. Both the flexible stent and the release system need to be quite reliable during the span release process, and the Perflex stent is most flexible at its propulsion force of 15.8 N/cm. Surprisingly, the Perflex stent is more flexible than the Nitinol stent when spanning through the vessel. With regard to stent support, the AVE Bridge was more flexible than the Perflex stent by 4.3 N/cm, but the AVE Bridge was 28% heavier than the elongated Perflex stent, while the propulsion force was almost identical (0.20/N vs. 0.19/N). Because it is not welded together, the AVE Bridge stent is susceptible to bending in both directions. Only the S.M.A.R.T outperforms the AVE Bridge stent in self-expanding stents across the vessel