RU2831669C1 - Interspinous carbon implant - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: interspinous implant for dynamic stabilization of spine is made of bulk carbon nanostructured material without alloying elements or alloyed with boron with ultimate compression strength of not less than 350 MPa.

EFFECT: invention provides higher biocompatibility, biomechanical properties and improved quality of the operation of the interspinous BCN implant.

2 cl, 2 tbl, 2 dwg

Description

The invention relates to medical technology and can be used in spinal surgery to correct damage and instability in the human vertebral bodies in all parts of the spine (cervical, thoracic, lumbar).

In surgical treatment of patients with degenerative diseases of the spine, decompressive operations are the most common. The purpose of the operation is to eliminate instability of the spinal motor segment, restore the musculoskeletal function of the spine, and decompress the structures of the spinal canal. Recently, encouraging data have appeared on the use of dynamic spinal stabilization systems using interspinous implants - devices implanted between the spinous processes of the vertebrae with minimal trauma to soft tissues. The task of such implants is to expand the intervertebral foramen through which the nerve root passes, which increases the space around the nerve root. In addition, the installation of an interspinous fixator increases the stability of the segment, unloads the posterior articular facets and leads to an increase in the size of the foraminal opening, and also allows limiting the extension of the spine during backward extension.

Indications for the use of interspinous implants are the following:

- degenerative lumbar stenosis of the spinal canal with the development of radicular radiculopathy;

- neurogenic intermittent claudication;

- hypertrophy of the yellow and interspinous ligaments;

- instability of the vertebral segment;

- degenerative spondylolisthesis 1st degree;

- Bostrup phenomenon (Bostrup syndrome);

- addition to microdiscectomy.

- foraminal stenosis;

- disc herniation with signs of segmental instability;

- transient pain in the segments adjacent to the spondylodesis zone;

- arthrosis of the facet joints.

The materials from which interspinous implants are made must meet a number of requirements:

• Non-toxic and non-corrosive;

• Durability;

• Technological;

• Wear resistance;

• Physical and mechanical properties close to bone.

Inadequacy of the material in at least one of the parameters reduces the functional value of the implant and its service life. The optimal combination of material characteristics ensures biocompatibility (including biomechanical) of the implant.

The requirements for the interspinous implant are very high. It must withstand all physiological loads. In addition, it must be biologically inert for the body, not lead to the development of an inflammatory process.

Currently, the most well-known implants for dynamic stabilization of the posterior support complex of the spine are COFLEX (Paradigm Spine), DIAM (Medtronic), WALLIS (Abbott Spine) and X-STOP (Kyphon - St. Francis Medical Technologies) (see 1. Schiavone A.M., Pasquale G. The use of disc assistance prostheses (Diam) in degenerative lumbar pathology: Indications, technique, and results // Ital. J. Spinal. Disord. - 2003. - Vol. 3. - P. 213-220.

2. Schnake K.J., Schaeren S., Jeanneret B. Dynamic stabilization in addition to decompression for lumbar spinal stenosis with degenerative spondylolisthesis // Spine. - 2006. - Vol. 31. - P. 442-449.

3. Schwarzenbach O., Berlemann U., Stoll T.M. et al. Posterior dynamic stabilization systems: DYNESYS // Orthop. Clin. North Am. - 2005. - Vol. 36. - P. 363-372.

4. Swanson K.E., Lindsey D.P., Hsu K.Y. et al. The Effects of an Interspinous Implant on Intervertebral Disc Pressures // Spine. - 2003. - Vol. 28. - P. 26-32.

5. Wiseman S.M., Lindsey D.P., Fredrick A.D. et al. The effect of an interspinous process implant on facet loading during extension // Spine. - 2005. - Vol. 30. - P. 903-907.).

The COFLEX implant is made of titanium alloy and is a U-shaped spring with two pairs of fasteners. The action of this implant is that it stretches the intervertebral openings, and its U-shape allows for controlled flexion of the spine.

The DIAM implant is an H-shaped, polyester-coated silicone with a honeycomb core and suture for fixation. This device has been used for several years in Europe. In the United States, this implant was approved in 2006.

The WALLIS implant consists of a titanium block between two separate parts connected by a Dacron cord or tape. The second generation of these implants were made of polyether ether ketone, which is a polymer similar to plastic, so they are less rigid and more flexible.

The X-STOP implant is made of two parts made of titanium. One part of the device is implanted near and under the spinous process, and the second part of the implant in the form of a plate is installed on the other side of the spinous process and then attached to the first part of the implant.

Interspinous implants made of titanium alloys and plastic materials have the following disadvantages.

The use of metal implants is always complicated by galvanoelectric phenomena, leading to metallosis of surrounding tissues and corrosion of parts. Metals tend to cause bone resorption.

Plastic implants can wear out over time and exhibit the "cold flow" and aging typical of plastic, which leads to deformation and destruction of the implant. In addition, wear products of polymeric materials often cause malignant degeneration of surrounding tissues.

The objective of the invention is to create an interspinous implant from a bulk carbon nanostructured material (hereinafter referred to as BCM).

The technical result is an increase in biocompatibility, biomechanical properties and an improvement in the quality of the operation of installing an interspinous implant made of OUN.

The technical result is achieved by the fact that:

- the interspinous implant is made of OUN, without alloying elements or alloyed with boron with a compressive strength of at least 350 MPa.

- the interspinous implant has radiopaque titanium markers.

The development of technology for obtaining numerous types of carbon materials along with the identified compatibility with living tissue has led to the intensification of research, the development of new and composite materials based on carbon for medicine. By now, it has been reliably established that carbon materials have no competitors in terms of the degree of satisfaction of biochemical and physical-mechanical requirements imposed on medical products.

These requirements include:

- absence of toxicity and carcinogenicity;

- invariability of arbitrary activity under the influence of biological environments;

- absence of corrosion phenomena upon contact with living tissues;

- closeness of physical and mechanical properties;

- absence of fatigue stress and, as a consequence, durability of the implant;

- the presence of osteogenic activity on the implant surface;

- low wear under friction conditions and indifference to wear products accumulating in the lymph nodes;

- the ability to stimulate tissue growth or regeneration of the underlying tissue;

- electrical conductivity close to that of tissue, without releasing ions into the environment;

- the ability to obtain a surface of virtually any purity class and simple production of a porous structure;

- unconditional and rapid sterilization of any kind.

None of the metals or plastics currently used for endoprostheses and implants are capable of meeting all these requirements.

The affinity of carbon materials with biological tissues is determined not only by low chemical activity, but also by the manifestation of bioactivity, as a result of which the surface of carbon materials is covered with an oriented and organized film of protein origin, similar to the tissue being replaced.

The speed and orientation of the deposited protein film depends on the surface properties of the carbon material. For example, the surface energy of isotropic pyrolytic carbon is 50 erg/ ^cm2 , but in contact with blood plasma or lymph it drops sharply to 20-30 erg/ ^cm2 . This value of free surface energy is most advantageous for long-term contact with biological environments.

Materials used for the manufacture of endoprostheses and implants can be arranged in the following order according to the value of normal electrochemical potential in blood plasma: glassy carbon (+0.329 mV), platinum (+0.332 mV), gold (+0.334 mV), pyrographite (+0.344 mV). It is known that glassy carbon has an amorphous structure, and pyrographite is close to a single crystal. It can be said that thus all carbon materials with different structures have a normal electrochemical potential within the range from +0.329 mV to +0.344 mV, i.e. comparable with these indicators of the most passive of all elements gold and platinum. Carbon materials are closest in electrochemical potential to the biological environment of a living organism.

As shown by morphological studies conducted on rabbits at the Hemholtz Moscow Research Institute of Eye Diseases using durable finely dispersed graphite MPG-6, syntactic carbon foam, carbon felt Karbotekstim-M and carbon fabric TGN-2M, all carbon materials were not rejected for a year, did not change their shape and were covered with a connective film of protein origin.

Therefore, in terms of biocompatibility, toxicity and corrosion, carbon materials are the best for use as implants.

OUN has a homogeneous, isotropic, fine-crystalline structure. OUN, due to its unique properties (high density, strength, wear resistance, biological compatibility with blood and body tissues), has found application in medicine. It is used to manufacture the main elements of artificial heart valves. To date, hundreds of thousands of artificial heart valves have been manufactured, delivered and are successfully functioning in the world. And this is one of the most important human implants. Work is currently underway to develop dental implants and hip joint elements from this material.

The main physical, mechanical and thermal properties of OUN are given in Table 1.

The lumbar spine, which is the most loaded in humans, is subject to heavy loads. Loads vary from 400 N in a standing position to 7000 N when lifting weights. Biomechanical studies have shown that the vertebral body (without osteoporosis) can normally withstand a load of up to 10,000 N. The physical and mechanical properties of OUN are closest to the properties of bone, as shown in Table 2. At the same time, the load that an OUN implant can withstand is more than 30,000 N, which is more than 3 times higher than the maximum physiological loads. The table shows that the physical and mechanical properties of titanium are an order of magnitude higher than the properties of bone. Therefore, with the same deformations, different stress states will occur in titanium and bone, which is the main reason for the loosening of metal implants.

The use of OUN for the production of implants will significantly improve their biomechanical properties.

Carbon materials are radio-negative. To improve the quality of the operation and the possibility of subsequent control of the implant position after installation, OUN implants have radio-opaque titanium markers in their design.

Another advantage of manufacturing implants from OUN is their manufacturability and relatively low cost. OUN is processed on turning, milling, drilling, grinding and polishing machines using standard cutting tools. The fine-grained structure of the material allows for the production of products with a thickness of 0.8-1 mm with edges of 0.03 mm and obtaining surfaces of 12-13 purity class.

The invention is explained by drawings. Fig. 1 shows a minimally invasive interspinous implant, and Fig. 2 shows an open-access interspinous implant made of OUN. The minimally invasive and open-access interspinous implant has radiopaque markers made of titanium for monitoring the position during and after surgery.

The proposed invention is implemented as follows.

OUN is obtained by pyrolysis of hydrocarbon raw materials by deposition on the inner surface of a cylindrical graphite substrate in special electrovacuum units at a temperature of about 1400°C. After the process of obtaining OUN of the required thickness is completed, the material is cut into blanks by mechanical processing. An interspinous implant with radiopaque titanium markers is made from the blanks using diamond grinding and polishing. The implant is washed in a special solution in an ultrasonic bath at a temperature of about 100°C. Then the implant is packaged and sterilized either in consumer packaging or immediately before the operation by any method.

The implant installation operation is performed as follows.

Minimally invasive interspinous implants can be inserted from the posterior approach with minimal incisions. When installing direct access implants, the posterior approach is used when it is necessary to remove osteophytes or intervertebral disc herniation.

When using a minimally invasive implant, perform the following steps:

- make a small incision and prepare a channel for implant installation;

- insert the implant on the holder into the pre-prepared canal;

- as soon as the end of the implant is between the spinal processes, begin to rotate the implant around its axis clockwise;

- when the saddle-shaped part of the implant is between the spinal processes (the implant should be positioned vertically), rotate the implant clockwise and counterclockwise at a small angle in order to feel the contact of the bone with the ribbed edges of the implant neck (tactile connection);

- remove the holder from the implant and check the quality of the implantation of the product using an electron-optical converter, focusing on the position of the radiopaque marks.

When using an open access implant, follow these steps:

- make the necessary incision and prepare the surgical field for implant installation;

- install a distractor and distract the vertebrae to the required distance for implant installation;

- insert the implant on the holder into a previously prepared location;

- remove distraction;

- remove the holder from the implant and check the quality of the implantation of the product using an electron-optical converter, focusing on the position of the radiopaque marks.

When manufacturing implants from OUN, biocompatibility and biomechanical properties will be increased and the quality of the operation for installing an interspinous implant will be improved.

Claims (2)

1. An interspinous implant for dynamic stabilization of the spine, characterized in that it is made of a bulk carbon nanostructured material without alloying elements or alloyed with boron with a compressive strength of at least 350 MPa. 2. An interspinous implant according to item 1, characterized in that it has radiopaque markers made of titanium.