RU2746825C1 - Sternum fixation system after median sternotomy surgery - Google Patents

Abstract

FIELD: medical equipment.

SUBSTANCE: invention relates to medical equipment. The system for fixing the sternum after the surgical operation of the median sternotomy includes at least one clamp consisting of a bioresorbable polymer plate with fixing teeth and a fastener with fixators, as well as a tubular removable clamp tip made of metal or polymer having a hardness exceeding the hardness of a bioresorbable polymer plate. At the end of the tip, a needle is installed or formed from a metal or polymer material having strength sufficient to pierce the tissues of the sternum. The removable tip is made with possibility of fixing the installed clamp. The clamp is reinforced with at least one bioresorbable polyfilament or monofilament thread made of a material that has a higher tensile strength than the material of the clamp itself. The period of bioresorption and preservation of the strength characteristics of the clamp material exceeds the period of healing of the patient's sternum. The bioresorption period of the material of the reinforcing threads is less or does not exceed the bioresorption period of the clamp material.

EFFECT: invention provides an increase in the tensile strength of a device made of a bioresorbable material having a tensile strength of no more than 100 MPa and low rigidity, while increasing the strength of fixation of the patient's sternum and maintaining the strength characteristics of the implant and its bioresorption for a period not less than the healing period of the patient's sternum.

7 cl, 5 dwg

Description

The invention relates to medical equipment and can be used in surgery for tightening the sternum after a surgical operation of a median sternotomy, in which the sternum is dissected to access the heart and coronary vessels.

The products used to close the sternum after sternotomy have a different design and are made of various materials - stainless steel, titanium and titanium alloys, polymers.

It is known, for example, a fixing device made of plastic according to EP 2677951 or a fixing device for closing the sternum made of elastic plastic material according to the application WO 2010004602.

From RU 2520864 the use of a wire suture material is known. However, stainless steel wires, despite improvements, are capable of cutting through the sternum in osteoporosis and severe stress (for example, a strong cough). In addition, stainless steel wires defragment in the body for a long time after installation, which can cause discomfort to the patient.

Known staple from document RU 115645 and a device in the form of an open ring with shoulders and fixing legs from RU 2199288, which are made of an alloy with thermomechanical shape memory (titanium nickelide). The disadvantage of these devices is that for their use it is necessary to sizing directly during the operation, which requires an excessive number of products of various standard sizes.

Known metal clamps, similar to that described in patent RU 2391934 and clamps type "claw" (for example, US patent 8936628). The device according to RU 2391934 for fixing the sternum contains the first and second plates, and the second plate is made with one end curved in the form of a hook for insertion into the intervals between the ribs, and the other is curved in the opposite direction and with a transverse groove, and the first plate is made on the lateral sides with oblique teeth, one end curved in the form of a hook for insertion into the spaces between the ribs and with a longitudinal groove between the toothed sides, and both toothed sides of the plate can be brought together, inside the transverse groove, and these teeth have the ability to disengage with the transverse groove, the distance between the depressions of the teeth on opposite sides of the first plate is equal to the width of the transverse groove made on the second plate (patent RU 2391934, IPC А61В 17/80, publ. 20.06.2010).

The known fixators are massive and do not always allow, if necessary, to get quick access to the heart, which is especially necessary on the first day after the operation. The same disadvantage applies to various plates and staples with screw fastening to the sternum.

In addition, rigid metal implants cannot be placed in children and adolescents, as their presence will adversely affect the growth of the chest. Magnetic metal and alloy implants make it impossible to perform some diagnostic procedures, such as magnetic resonance imaging.

Of the non-metallic implants used to fix the sternum after longitudinal sternotomy, for example, the Sternal ZIPFIX® system from DePuy Synthes is known (for example, at https://www.jnjmedicaldevices.com/en-US/product/sternal-zipfixr-system) , also described in patent EP 0238219. The system consists of PEEK (polyetheretherketone) implants and an application instrument. The implant allows you to quickly close the chest with sequential tightening of the sternum along the incision line.

The disadvantage is the insufficient strength of the implant fixation, its massiveness (relative to the stainless steel wire) and the impossibility of installation for children and adolescents. The polymer material PEEK (polyetheretherketone) does not have the property of bioresorption, is strong enough to break, but has insufficient hardness, which forced the developers to equip the implant with a metal needle, which is removed after piercing the tissues and wrapping the sternum before tightening the sternum and fixing it.

All known systems remain in the patient's body for life, their removal is not provided. In some patients, especially asthenic physique, retainers can be noticeable even after complete healing of the suture, which leads to a decrease in the quality of life.

To improve the quality of life of patients after the operations, it is desirable that no foreign products remain on the sternum after its healing (on average, 4-6 months). In this regard, of particular interest are products made from bioresorbable materials - materials that decompose in the body into safe components. However, many bioresorbable materials, which are suitable for use as implants in their chemical composition, have low tensile strength and insufficient hardness with satisfactory values of other physical and technical characteristics.

The technical problem solved by the invention is the creation of a device for closing the sternum after a surgical operation of a median sternotomy, which does not have the drawbacks of known analogues, namely, a device made of bioresorbable materials, which allows reliable connection of the edges of the sternum, subject to the condition that the period of preservation of the strength characteristics of the implant and bioresorption material exceeds the healing time of the patient's sternum.

The technical result achieved by the invention is an increase in the tensile strength of a device for closing the sternum after a surgical operation of a median sternotomy made of a bioresorbable material having a tensile strength of not more than 100 MPa and low rigidity, while increasing the fixation strength of the patient's sternum and maintaining the strength characteristics of the implant and its bioresorption within a period not less than the healing period of the patient's sternum.

The problem is solved, and the technical result is achieved by a system for fixing the sternum after a surgical operation of a median sternotomy, which includes at least one clamp, consisting of a bioresorbable polymer plate with fixing teeth and a fastener with fixators, as well as a tubular removable clamp tip made of metal or polymer having hardness, exceeding the hardness of the bioresorbable polymer plate, while at the end of the tip a needle is installed or formed from a metal or polymer material having a strength sufficient to puncture the tissues of the sternum, and the removable tip is designed to fix the installed clamp, and the clamp is reinforced with one or more bioresorbable polyfilament or monofilament threads made of a material that has a higher tensile strength than the material of the clamp itself, while the period of bioresorption and preservation of the strength characteristics of the clamp material exceeds the healing period of the patient's sternum, and the period of bior The adsorption of the material of the reinforcing threads is less or does not exceed the bioresorption period of the clamp material.

According to the invention, in particular cases of execution:

- fixing toothed hooks are located on one side of the clamp, and the fastener is made with a one-sided arrangement of the latches;

- fixing toothed hooks are located on both sides of the clamp symmetrically or with a shift, and the fastener is made with a two-sided arrangement of latches;

- the removable tip is fixed on the clamp using a thread, or a latch, or another elastic or rigid fixation method, or fitted in the clamp with an interference fit and fixed by friction;

- the polymer plate of the clamp is made flat;

- the polymer plate of the clamp contains along the plate on one of its side or on both sides of the sides, allowing to increase the cross-section of the clamp;

- in case of insufficient strength of the material of the clamp for fixing under load, the system on the sternum is additionally fixed by welding at the location of the fastener.

The technical result is achieved as follows.

Initially, an insufficiently tear-resistant clamp can be reinforced with one or more bioresorbable multifilament or monofilament threads made of a material that has a higher tensile strength than the material from which the clamp is made, even if their bioresorption period is less than that of the clamp. For example, a clamp made of polymer with a bioresorption period of several tens of months and a tensile strength of 15 MPa is reinforced with one or more bioresorbable polyfilament or monofilament threads of glycolide and L-lactide with a strength of 70 MPa, the bioresorption of which occurs within several days or tens of days. This provides an increase in tensile strength compared to clamps made without reinforcement.

The tubular removable tip of the clamp made of metal or polymer has a hardness exceeding the hardness of a bioresorbable polymer plate, while at the end of the tip a needle is installed or formed from a metal or polymer material having a strength sufficient to pierce the tissues of the sternum. Insufficient hardness of the bioresorbable material, which does not allow for the passage of the clamp through the intercostal spaces and bypassing the clamp around the halves of the dissected sternum without an additional tool, is compensated by the use of a guide conductor made in the form of a tip on the clamp. Due to the use of a removable tip made of a harder material, which makes it possible to create through channels in the tissues of the intercostal spaces and ensure the passage of the implant in the retrosternal space, it is possible to use a soft polymer (for example, E-polycaprolactone (PCL)).

The tensile strength of the clamp is increased due to the presence of fixing gears, which are located on one or both sides of the clamp symmetrically or with a shift, and the fastener is made with a single or double-sided arrangement of latches, which increases the engagement. In order to increase the average thickness of the clamp and, as a consequence, the tensile strength of the clamp, the teeth on one side of the clamp can be disposed asymmetrically to the teeth on the other side.

The essence of the invention is illustrated by drawings, which show the claimed system for fixing the sternum after a surgical operation of a median sternotomy.

FIG. 1 - disassembled system:

a) a removable tip of the clamp with a needle;

b) a clamp with a fastener.

FIG. 2 - cross-section of the clamp plate without toothed hooks:

a) without sides with reinforcing threads;

b) with one-sided arrangement of sides with reinforcing threads;

c) with a two-sided arrangement of sides with reinforcing threads.

FIG. 3 - longitudinal median section of the clamp plate with toothed hooks:

a) with toothed hooks located on one side without intervals;

b) with spaced toothed hooks on one side.

c) with toothed hooks located symmetrically on both sides, without intervals;

d) with toothed hooks located asymmetrically on both sides, at intervals.

FIG. 4 - longitudinal median section of the clamp fastener:

a) with one-sided arrangement of clamps;

b) with double-sided symmetrical arrangement of latches.

FIG. 5 - sternum with a longitudinal dissection line, pulled together by five clamps, the fasteners of which are on the left side.

The figures indicate:

1 - bioresorbable polymer clamp plate with fixing toothed hooks and fastener;

2 - removable clamp tip;

3 - the needle of the clamp tip;

4 - clamp fastener;

5 - reinforcing threads;

6 - sternum (chest);

7 - sternum dissection line.

The inventive system is used as follows.

After the surgical operation of the median sternotomy, when the sternum 6 is closed (Fig. 5), the use of a clamp with a tip on it is required (Fig. 1). The bioresorbable polymer plate 1 is made of a polymer that has the mechanical characteristics necessary for installation and is able to maintain the required tensile strength during the healing period of the sternum (at least 4 months). The amount of required strength depends on the number of clamps installed to fix the sternum. The length of the tip 2 can be so long that it fits the entire clamp up to the clasp 4. In this case, the tip acts as a guide-guide for gripping the sternum. This is necessary when a soft material clamp is difficult to pass behind the breastbone. If the material from which the clamp is made is sufficiently hard, the tip may be shorter.

Needle 3 tip 2 (Fig. 1) is used to create channels symmetrically on the left and right sides of the sternum in 2-6 intercostal spaces. Usually 4-5 clamps are installed on the sternum. The sternocostal frame is tightly compressed until the right and left halves of the sternum are completely closed 6. After grasping the sternum 6 (Fig. 5), the tip 2 is removed from the clamp, the free tip of the clamp is inserted into fastener 4 and tightened until the required force is achieved while ensuring the immobility of the connection of the halves of the sternum along the cutting line 7, as shown in FIG. 5. After fixing, the excess part of the clamp is cut flush with the fastener 4.

For materials with low hardness, the mechanical fastener may not provide a secure hold. In this case, since bioresorbable polymers usually have a low melting point (usually in the range of 325 ... 370 K), welding by thermal, thermomechanical or any other method can be used to strengthen the joint. In this case, the thermoelement can be built into a special tool used to tighten the clamp or be used separately.

To ensure sufficient tensile strength, the clamp made of bioresorbable material contains reinforcing threads 5 (Fig. 2) also made of bioresorbable material, for example, suture, even with a short bioresorption period (several days or weeks). In a shell made of a bioresorbable polymer with a low bioresorption rate, the reinforcing material will retain its properties until it begins to directly interact with biological tissues, i.e. as long as its coverage will exist.

The clamp plate 1 can be flat (Fig. 2a). To provide the required tensile strength, the cross-sectional area can be increased by creating beads along the plate (Fig. 2b). With a two-sided arrangement of the teeth on the plate, the sides can also be located on both sides, as shown in Fig. 2c).

Depending on the physical and mechanical characteristics of the material from which the clamp is made, fixing the toothed hooks (teeth) engaging with the latches in the fastener can be located both on one side of the clamp (the longitudinal section is shown in Fig.3a), b), so and on both sides of the plate symmetrically or offset to increase the cross-sectional area of the yoke for increased tensile strength. The nature of the arrangement of the toothed hooks on the plate determines the design of the fastener 4 - with a one-sided (Fig. 4a) or two-sided arrangement of the latches (Fig. 4b).

If the clamp is made, for example, of ε-polycaprolactone with a tensile strength σ = 16 MPa, then when installing 5 clamps for an adult, it is required to ensure the strength of one clamp in a fixed (connected) state of at least 340 MPa, which without reinforcement will be provided when the clamp is sectioned not less than 21.25 mm ² . With a clamp width of 7 mm, its thickness should be more than 3 mm, excluding the teeth, which is quite a lot for people with an asthenic constitution. The reduction in thickness is achieved by using reinforcement. If for reinforcement we use suture threads based on polyglactin with a diameter of 0.15-0.2 mm (for example, Vicryl 4/0 by Ethicon Inc., part of the Johnson & Johnson group), then the presence of 4 reinforcing threads in the clamp will reduce cross-sectional area of the clamp up to 11.25 mm ² , which will make the clamp thickness less than 2 mm with a width of 7 mm.

In cases where the design of the fastener, with acceptable dimensions, does not provide the required strength, it is recommended to use welding. The need for a welded joint may be due to the choice of material, the height and width of the teeth of the clamp and fastener clips, as well as the number of clips in the fastener. For example, when creating a clamp from ε-polycaprolactone with a clamp width of 6 mm, with one-sided arrangement of toothed hooks 1 mm high and with 2 clamps in the clasp (as shown in Fig.4a), the holding force will be no more than 150 N, which is not enough for the load at 350 N, acting on 1 clamp, with a strong cough of the patient, if the patient has 5 clamps installed. In this case, additional fixation of the joint by welding is required, namely, heating of the contact point to 340-345 K, which will lead to local melting of ε-polycaprolactone and, after solidification (at room temperature for no more than 2-3 minutes), will create a joint of the required strength.

Examples of specific implementation of the claimed system.

Clamp 1: material - polycaprolactone; made by 3D printing (additive technology); length 300 mm, width 7 mm with one-sided arrangement of teeth 1 mm high. The clamp is reinforced with 5 strands of 90% glycolide and 10% L-lactide (Vicryl 4/0 suture). Bumpers on one side of the clamp, 1 mm high and wide. Clasp with two pins.

Clamp 2: material - polycaprolactone, reinforced with 5 threads of 90% glycolide and 10% L-lactide (Vicryl 4/0 suture material); production method - injection molding; length 300 mm, width 7 mm with two-sided asymmetric arrangement of teeth 1 mm high. Bumpers on both sides of the clamp, 1 mm high and wide. The clasp is double-sided, with 4 latches.

Tips: material - polylactide; made by 3D printing (additive technology); length 250 mm; a needle made of the same material.

For the manufacture of clamps, polylactide-coglycolide (PLGA) can also be used in a composition with polyhydroxybutyrate / oxyvalerate (PGBV) and with PLA and other bioresorbable materials.

Thus, the application of the invention achieves an increase in the tensile strength of a device for closing the sternum after a surgical operation of a median sternotomy made of a bioresorbable material having a tensile strength of not more than 100 MPa and low rigidity, while increasing the fixation strength of the patient's sternum and maintaining the strength characteristics of the implant and its bioresorption within a period not less than the healing period of the patient's sternum.

Claims (7)

1. A system for fixing the sternum after a surgical operation of a median sternotomy, including at least one clamp consisting of a bioresorbable polymer plate with fixing teeth and a fastener with fixators, as well as a tubular removable clamp tip made of metal or polymer having a hardness exceeding the hardness of a bioresorbable polymer plate , at the same time, at the end of the tip, a needle is installed or formed from a metal or polymer material having a strength sufficient to puncture the tissues of the sternum, and the removable tip is made with the possibility of fixing the installed clamp, and the clamp is reinforced with at least one bioresorbable polyfilament or monofilament thread made of a material having a large tensile strength than the material of the clamp itself, while the period of bioresorption and preservation of the strength characteristics of the clamp material exceeds the healing period of the patient's sternum, and the period of bioresorption of the material of the reinforcing threads is less or does not exceed the period bioresorption of the clamp material. 2. The system of claim. 1, characterized in that the locking gears are located on one side of the clamp, and the fastener is made with a one-sided arrangement of the latches. 3. The system of claim. 1, characterized in that the fixing gears are located on both sides of the clamp symmetrically or with a shift, and the fastener is made with a two-sided arrangement of the latches. 4. The system of claim. 1, characterized in that the removable tip is fixed to the clamp by means of a thread or a latch, or is fitted in the clamp with an interference fit and fixed by friction. 5. The system of claim. 1, characterized in that the polymer plate of the clamp is made flat. 6. The system according to claim. 1, characterized in that the polymer plate of the clamp contains along the plate on one of its sides or on both sides of the sides, allowing to increase the cross-section of the clamp. 7. The system of claim. 1, characterized in that in case of insufficient strength of the material of the clamp for fixation under load, the system on the sternum is additionally fixed by welding at the location of the fastener.

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