Degradable vascular stent with tension-compression expansion uniformityTechnical Field
The invention relates to the technical field of medical appliances, in particular to a degradable vascular stent with tension-compression expansion uniformity.
Background
In recent years, along with the acceleration of the modern life rhythm and the transformation of dietary structures, the prevalence of vascular obstructive diseases presents a continuously growing situation, and has become an important hidden danger threatening public health. In the field of vascular disease treatment, stent interventional therapy is one of the mainstream means of clinical treatment by virtue of its advantages of minimally invasive and immediate curative effects. However, the existing stent plays a mechanical supporting role, and simultaneously, mechanical damage to the vessel wall can be caused in the expanding process, so that local inflammatory reaction and intimal hyperplasia are caused, and finally, clinical complications of restenosis in the stent are caused. Studies have shown that such restenosis is closely related to imbalances in stress distribution after stent implantation. Therefore, inhibiting the restenosis phenomenon in the stent has become a core subject for the development of vascular stent technology, and optimizing the geometric configuration and mechanical property distribution of the stent has become an important breakthrough direction for improving the long-term curative effect of the stent.
Vascular stents serve as a precision medical device that plays an important role in the medical field, but at the same time present challenges. Its function is to dilate a stenosed or occluded vessel by mechanically supporting, restore blood flow, provide sustained radial support, inhibit elastic recoil of the vessel, and simultaneously inhibit intimal hyperplasia and restenosis. However, due to its structural limitations, localized overstresses can occur during expansion, which can lead to stent fracture or vascular injury.
The tension-compression uniform expansion structure is a positive-negative poisson ratio switchable structure. The structure expands in the transverse direction when subjected to uniaxial stretching or compression, i.e. exhibits a negative poisson's ratio effect when stretched and a positive poisson's ratio effect when compressed. The traditional vascular stent can deviate from the expected actual position of the stent due to axial contraction during radial expansion in implantation operation, a doctor needs to repeatedly adjust the stent during operation, the length of the stent after expansion is basically unchanged by eliminating the axial contraction, the doctor can accurately position the stent once, the operation risk is reduced, and the traditional vascular stent can be radially contracted when being compressed after being implanted into a human body, which possibly leads to restenosis of the blood vessel. Unlike conventional stents, the tension-compression-homogenizing structure can expand in the radial direction when being stretched or compressed, which is more beneficial to better positioning of the stent during implantation and plays a role in fixing and supporting after implantation. The positive and negative poisson ratio switchable effect of the pull-press homogeneous expansion material is derived from the special internal structure, namely the concave structure and the hexagonal honeycomb structure. Because the tension-compression average expansion structure is complex, the additive manufacturing technology has the characteristics of high design freedom degree, capability of precisely controlling the microstructure of the material and the like, and therefore, the additive manufacturing technology is very suitable for preparing the tension-compression average expansion structure.
Disclosure of Invention
The invention solves the technical problems that the traditional blood vessel stent with the pull-push structure is not easy to position when being implanted and can not provide good supporting force when being subjected to vasoconstrictive stress after being implanted, and reduces the probability of restenosis in the stent by providing the degradable blood vessel stent with the pull-push average expansion performance. The degradable vascular stent with the tension-compression expansion performance can be uniformly expanded under the action of tensile and compressive stress, the fitting property, expansion consistency and long-term service stability of the stent and a vascular intima are obviously improved, and the degradable vascular stent is suitable for treating vascular stenosis or occlusive diseases.
In order to achieve the aim, the invention adopts the following technical scheme that a degradable vascular stent with the tension-compression average expansion performance is formed by arranging a plurality of tension-compression average expansion basic structural units along the circumferential direction and the axial direction of the vascular stent to form a tension-compression average expansion vascular stent structure;
The stretching and pressing expansion-homogenizing basic structure unit is formed by combining a concave structure and a hexagonal honeycomb structure, wherein the hexagonal honeycomb structure is an outer layer, and the upper end and the lower end of the hexagonal honeycomb structure are provided with gaps;
the pulling-pressing and expanding vascular stent structure is made of degradable materials, and has the pulling-pressing and expanding effect and can be degraded in vivo.
The concave structure comprises a T-shaped rod and inclined rods, wherein the horizontal part of the T-shaped rod is positioned at the outer side of the hexagonal honeycomb structure, and the top points of the T-shaped rod are respectively connected with the side surfaces of the hexagonal honeycomb structure through the two inclined rods after the vertical part of the T-shaped rod is inserted from the gap.
The number of the pulling-pressing uniform expansion basic structural units is 4-8 along the circumferential direction of the vascular stent.
The number of the pulling-pressing uniform expansion basic structural units arranged along the axial direction of the vascular stent is more than 2.
The degradable material is a metal material, a high polymer material or a metal high polymer composite material, so that the vascular stent can be completely degraded in vivo after the treatment task is completed, and degradation products can be absorbed and metabolized by human bodies.
The metal material is magnesium and its alloy, iron and its alloy, zinc and its alloy, and the polymer material is polylactic acid, polyglycolic acid and polycaprolactone.
Because the degradable material is generally weak in mechanical property, the cross-sectional area of the scaffold structure can be increased by reducing the number of the arranged pulling-pressing average expansion basic structural units, so that the mechanical supporting capability of the degradable scaffold on the vascular wall is enhanced.
The tension-compression uniform expansion degradable vascular stent is formed by axially arranging tension-compression uniform expansion basic structural units, the arrangement number of the tension-compression uniform expansion basic structural units exceeds 2, and the arrangement number of the units directly determines the axial length of the stent, so that the specific axial arrangement number can be determined according to the actual requirement on the axial length of the stent in clinical application.
The degradable vascular stent with the tension-compression expansion performance can adapt to the contraction and relaxation stress of blood vessels, provide uniform and stable mechanical support, reduce restenosis risk, realize a staged function through degradable materials, namely ensuring smooth storage cavity in early stage, gradually transferring load to a new tissue along with material degradation in later stage, promote natural repair of the blood vessels, simultaneously avoid complications such as inflammation, thrombus and the like caused by long-term retention of the metal stent, and provide a safer and more physiological-demand-compliant solution for cardiovascular disease treatment.
Drawings
FIG. 1 is a schematic diagram of a structural unit of a tension-compression average expansion foundation;
FIG. 2 is a graph of a stacked in two dimensions of a structure of a tensile and compressive uniform expansion foundation structure unit;
fig. 3 is a structure formed by the curl thickening of fig. 2.
Fig. 4 is a graph reflecting poisson's ratio effect of the pull-press distention cell.
Detailed Description
The invention will be described in further detail with reference to the drawings and the detailed description.
As shown in fig. 1, when the tensile-compressive uniform expansion basic structural unit is subjected to longitudinal compressive stress, the whole structure is equivalent to a traditional hexagonal honeycomb structure, so that the structure can transversely expand and presents a positive poisson ratio effect. When subjected to longitudinal tensile stress, the structure as a whole can be regarded as a concave honeycomb structure. Thus, the structure will also expand in the transverse direction, exhibiting a negative poisson's ratio effect. The drawing-pressing expansion structure is formed by thickening a plurality of graphs shown in fig. 1 after two-dimensional superposition to form a structure shown in fig. 2, and can be expanded transversely in the plane when being subjected to in-plane tensile or compressive stress in the longitudinal direction, and is curled into a three-dimensional tubular structure shown in fig. 3 from the structure shown in fig. 2, and can be expanded in the radial direction when being subjected to tensile or compressive stress in the axial direction.
The pulling-pressing average expansion structure can be thickened after being overlapped in two-dimensional directions by a graph (or other two-dimensional graphs with the pulling-pressing average expansion effect) shown in the graph 1, and the structure can be bent into a cylinder shape shown in the graph 3 according to actual needs.
The pull-press average expansion structure comprises all positive and negative poisson ratio switchable structures, including but not limited to the structures shown in the drawings.
Referring to fig. 3, fig. 3 is a schematic view of the tension and compression average expansion basic structural unit arranged along the circumferential direction and the axial direction of the bracket. The tension-compression uniform expansion basic structural units are arranged along the circumferential direction of the stent and axially arranged to form a tension-compression uniform expansion degradable stent structure, wherein the number of the axially arranged stent units determines the axial length of the vascular stent. The specific axial arrangement number is determined according to the axial length requirement of the vascular stent in clinical application.
As can be seen from fig. 4, the structure exhibits a negative poisson's ratio under tensile stress (positive strain) and expands in volume, while the structure exhibits a positive poisson's ratio under compressive stress (negative strain) and also expands in volume. Thus, it is verified that the structure can realize expansion effect under tensile or compressive stress.
The tension-compression uniform expansion vascular stent structure provided by the invention is applicable to degradable materials and mainly comprises three major categories of metal materials, high polymer materials and composite materials. The degradable material has good biocompatibility, reduces the risk of complications, and can be degraded and absorbed in vivo. Iron alloy, zinc alloy, magnesium alloy, polylactic acid and the like belong to the degradable materials.
The manufacturing of the pull-press expansion degradable vascular stent structure provided by the invention can be realized by adopting an additive manufacturing method.