RU2234868C2 - Surgical suture material - Google Patents

Abstract

FIELD: surgical technics.

SUBSTANCE: material is provided in the form of thread and titanium nickelide-based alloy. The latter has equal critical stresses of alternating deformation within a temperature range from +10 to +45^оС and critical stresses are 250 to 400 MPa.

EFFECT: increased elasticity of suture material.

5 dwg, 2 ex

Description

The invention relates to medicine, namely to surgical technique.

To connect the disparate tissues of the body is currently widely used since ancient times, the well-known method of stitching using filament suture. Moreover, the success of the operation largely depends on the quality of the suture material and, specifically, on its technical characteristics such as tensile strength, strength in nodes in the dry and wet state, ductility and elasticity, trauma, hydrophilicity, biochemical and biomechanical compatibility, as well as a number of other characteristics. The abundance and importance of requirements determine the separate and intense interest of users and the urgent task of material researchers and developers.

The level of the specified technique should include the widely used suture surgical material in the form of a thread of collagen fibers of animal origin - catgut [1]. A significant admixture of non-collagenic proteins has an allergenic effect on surrounding tissues, which is a significant disadvantage of catgut. In addition, for all other characteristics, the catgut does not satisfy the necessary requirements. A high Young's modulus indicates its rigidity, low handling characteristics, and the ability to penetrate tissue.

Similar disadvantages are non-absorbable suture material from silk fibers [1]. A fibroblastic reaction develops around the silk thread, an area of extensive fibrosis and inflammation is formed. The material is difficult to disinfect.

Known more advanced suture materials obtained on the basis of the synthesis of polymers [1], as well as methods of metallurgical technology. The latter area was a significant progress in this field of technology in connection with the development of medical alloys based on titanium nickelide, differentiated for various surgical needs.

Known surgical suture material in the form of a thread [2] from an alloy based on titanium nickelide, adopted as a prototype. It used technological measures to realize critical stress values of alternating bending deformation of 50 ÷ 150 MPa in the range of operating temperatures + 10 ÷ + 45 ° С. In the language of graphical representations of the deformation properties of the material, this means the symmetry of the upper and lower branches of the hysteresis stress-strain diagram under alternating stress conditions in a martensitic alloy at temperatures below the phase transition (Fig. 1, curve 2). If this condition is not met, the diagram is asymmetric (Fig. 1, curve 1), which means in practice the relative stiffness of the material (inconvenience for surgical procedures) and low deformation cycle resistance. Thus, the advantages of the suture material [2] are the same stiffness in both directions of deformation and low stiffness (the feeling of softness of the thread when it is felt), as well as high resistance to 10 ⁶ cycles - cycle resistance, i.e. the ability to repeatedly deform without destruction.

The disadvantage of this analogue is low, in some cases, elasticity relative to practical needs. This characteristic is essential for the quality of the suture, especially for large wounds, the speedy healing of the wound. The elastic thread allows you to optimize the compression of the contracted edges of the wound and, thereby, facilitate the results of surgeon errors, leading to ischemic consequences (with excessive constriction) or failure of the suture (with a lack of effort). It is also unfavorable for the healing process to weaken the thread tension while reducing tissue swelling. Elastic suture material is designed to compensate for these shortcomings of a subjective and objective nature.

The technical result of the invention is to increase the elasticity of suture material.

The specified technical result is achieved by the fact that in the surgical suture material in the form of a filament of an alloy based on titanium nickelide with equal critical stresses of alternating deformation in the range of operating temperatures + 10 ÷ + 45 ° C, critical stresses of alternating deformation of 250 ÷ 400 MPa are selected.

The picture of the transformation of the crystal lattice in the process of martensitic transformations was determined by the authors of the proposal as a result of scientific research, it is rather complicated and does not seem obvious to prove the cause-effect relationship “sign - technical result”. A lightweight alternative to it can be a qualitative interpretation of the process based on a comparative analysis of stress-strain diagrams of known and proposed materials.

. Определение “критическое” означает предел обратимой деформации (дальше т.А. на графике пунктирная линия), за которой следует пластическая необратимая деформация, переходящая в разрушение материала. При снятии нагрузки возврат к исходной форме идет с меньшими напряжениями, реализуя в виде гистерезиса Δσ широко свойственный природе в целом закон запаздывания [3]. Обратимая ветвь АВО (фиг.2) диаграммы, которая является рабочим участком ВО для использованного (установленного в ране) шовного материала может иметь вид фиг.2. Отсутствие остаточной деформации на диаграмме фиг.2 свидетельствует о наличии эластичности в совершенном виде, тогда как материал-прототип мартенситно пластичен (величина остаточной деформации составляет существенную долю от общей деформации).The elastic (in life, “rubber-like”) behavior of materials based on titanium nickelide alloy during deformation is characterized by a non-linear, practically zero, dependence of deformation c on load stresses (Fig. 2, section OA), in contrast to the linear dependence of elastic deformation obeying Hooke’s law . As follows from the graph, the increase in stress σ decreases with increasing strain, asymptotically approaches a critical value

. The definition of “critical” means the limit of reversible deformation (hereinafter referred to as A.A. on the graph a dashed line), followed by plastic irreversible deformation, which transforms into fracture of the material. When the load is removed, the return to the initial form occurs with lower voltages, realizing in the form of a hysteresis Δσ the law of delay, which is widely characteristic of nature as a whole [3]. The reversible branch ABO (figure 2) of the diagram, which is the working area BO for the used (installed in the wound) suture material can be in the form of figure 2. The absence of permanent deformation in the diagram of figure 2 indicates the presence of elasticity in perfect form, while the prototype material is martensitic plastic (the value of permanent deformation is a significant fraction of the total deformation).

. до 250÷400 МПа приводит к нужной трансформации указанной зависимости, т.е. к повышению эластичности. Условия реализации указанных признаков разнообразны и сводятся к мероприятиям технологического характера.It was experimentally revealed that an increase in critical stress values

. up to 250 ÷ 400 MPa leads to the desired transformation of this dependence, i.e. to increase elasticity. The conditions for the implementation of these characteristics are varied and are reduced to technological measures.

A decrease in the critical stress below 250 MPa shifts the deformation dependence curve from the region of elastic deformation to the region of plasticity of the transformation. An increase in critical stresses above 400 MPa leads to the active development of plastic deformation associated with dislocation processes in the material.

The essence of the proposal is not published by the authors and is not found in patent information sources, which indicates its compliance with the criterion of “inventive step”.

The illustrations show:

Figure 1. The stress-strain diagram for suture material is a prototype; 1 - asymmetric form, 2 - symmetric form.

Figure 2. Stress-strain diagram for the proposed suture material.

Figure 3. The stress-strain diagram of a particular material.

Figure 4. Injured right hand before surgery.

Figure 5. Injured right hand 4 months after surgery.

Achievability of the technical result is confirmed by comparative tests, as well as clinical examples of the use of the proposed suture material in plastic surgery in the microsurgery department of Omsk.

Specific suture material obtained in the following way.

The composition of the mixture prepared for melting includes the main ingredients of the alloy in the content: titanium - 49 ÷ 50 at.%, Nickel - 50:51 at.%, Molybdenum - 1 ÷ 2 at.%. The melt obtained by induction heating [4] is poured into molds and formed by cooling in the form of cylindrical rods with a diameter of 22 mm

Further machining consisted of reusable stepwise rotational forging and subsequent drawing through spinnerets to a final thread diameter of 0.095 mm. The diagram “stress-bending deformation” taken for the obtained material is presented in FIG. 3. The critical stress (calculated for uniform tensile strain) for it was 280 MPa, the value of elastic deformation was up to 8%, and the average unloading stress was about 70 MPa. No plastic deformation.

In terms of elasticity, the resulting suture material is comparable to the best known in this indicator - “Dexon 5/0” thread, but surpasses it in strength with a thickness of 3-6 times less. This circumstance allows you to create a large concentration of filaments in tissues, the connection of which requires considerable effort (for example, with tendon anastomosis) with a minimum risk of eruption.

Clinical testing of the proposed material was carried out in the most stringent conditions of emergency reconstructive plastic surgery of all the anatomical structures damaged by trauma: bones, tendons, blood vessels, nerves, soft and integumentary tissues.

Example 1

Patient M., delivered to the microsurgery department with injuries of the right hand by a circular saw (Fig. 4) 2 hours after trauma.

Under conduction anesthesia, the initial surgical treatment of the wound was performed, non-viable tissues were excised and capsules of the 2nd and 3rd fingers were sewn atraumatically with the specified thread, two saphenous veins (diameter 0.5 and 0.8 mm) surrounding soft tissues and skin.

Observation 2 months after the operation revealed the restoration of an adequate venous outflow, a good range of movements in the hand, an invisible cosmetic scar (Fig. 5)

Example 2

Patient D., 16 years old, was taken to the department with a cut (glass) wound of the right hand, damage to the tendon of the 1st finger. There is no active extension of the finger. Under conduction anesthesia, primary wound treatment and tendon anastomosis were performed. After a three-week tire immobilization, movements were developed. Condition 2 months after surgery - a complete restoration of range of motion.

The industrial applicability of the proposal is determined by the readiness of the technological base and the positive feedback of clinician surgeons.

Sources of information

1. Bulletin of the Russian Association of Obstetricians and Gynecologists. Scientific and practical journal, No. 1, March, 1966, p.30-39.

2. RF patent No. 2164385 (prototype).

3. Biocompatible materials and shape memory implants. Ed. V.E. Gunther. Tomsk Northampton, MA 2001, pp. 5-8.

4. Medical materials and shape memory implants. V.E. Gyunter, G.Ts. Dambaev et al. TSU, Tomsk, 1998, p. 456.

Claims (1)

Surgical suture material in the form of a filament from an alloy based on titanium nickelide with equal critical stresses of alternating deformation in the range of operating temperatures of 10 ÷ 45 ° C, characterized in that the alloy has critical stresses of 250 ÷ 400 MPa.

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