RU2680917C2 - Membrane-torsion intervertebral disc endoprosthesis - Google Patents

Abstract

FIELD: medicine.SUBSTANCE: membrane-torsion intervertebral disc endoprothesis contains upper and lower opposite supporting plates arranged on one axis with serrated fixation elements in the bodies of the vertebrae and elastic supporting-centering elements installed between them. On the inner surfaces of the supporting plates, central round recesses are made to house the bottom parts of the opposite and coaxial supporting-centering elements represented by poppet corrugated membranes which are attached with their curved edges to the plates, forming a hermetically sealed cavity therewith, and are interconnected by elastic elements in the form of flat springs attached to their surfaces, located at equal distances from the membranes axis with the same circular pitch. The cavities formed by the membranes and plates are filled with a viscous-flowing substance.EFFECT: increased period of revision surgery and quality of life.3 dwg

Description

The invention relates to medical equipment and can be used in vertebrology and neurosurgery in the treatment of injuries, diseases and injuries of the spine.

In medical technology, implant designs in the form of cages used in the surgical treatment of spinal diseases are known, which are box-shaped metal inserts with holes and cavities of various configurations, fixation elements in the form of teeth on supporting surfaces intended for insertion into the vertebral bodies between which they are placed instead of a remote intervertebral disk (Patent of Ukraine No. 41079 A dated 10.15.2001, Bull. No. 9; export @ gmreis.com.br - Posterior Lumbar Spacer).

The main distinguishing feature of such implants is that they rigidly connect two neighboring vertebrae, depriving them of relative mobility in all directions, thereby limiting the flexibility and functionality of the human spinal column.

The restoration of the mobility of the spinal elements is ensured by endoprostheses of the intervertebral discs, consisting of two opposite and coaxially arranged support plates of a permeable porous superelastic material, between which there is a support-centering element made of fluoroplastic, connected to the plates using a buffer layer (Patent RU No. 2140229 from 10.27.1999 )

Also known is the design of an endoprosthesis (implant) of the intervertebral disc, containing two support plates with fixation elements and a support-centering element located between the plates in the form of a disk made of alloplastic material having elastic properties. The fixation elements are made of a material with a memory effect, which allows them to rotate the latches around the axis and fix the plates in the vertebral bodies (Patent RU No. 2080841, IPC A61F 2/44, 1997).

The design flaws include: installation complexity; the need for heating the clamps during installation, which adversely affects the bone tissue of the vertebrae; the occurrence of electrocorrosion due to various materials of the parts of the endoprosthesis, which reduces the reliability of fixation and causes its increased wear; low bioinertness due to the presence of nickel in the material of fixatives, causing a toxic effect on bone tissue and the human body as a whole; a short period of time before conducting revision operations associated with the replacement of a worn endoprosthesis.

The design of the endoprosthesis (implant) of the intervertebral disc (Patent RU No. 2200510 C1, IPC 7 A61F 2/44, 2003), containing two axisymmetric plates and a support-centering element between them in the form of a disk made of alloplastic material with elastic properties, was taken as a prototype ( silicone rubber). The inner opposing surfaces of the support plates have a concavity in the center and a fixing annular protrusion, providing lateral fixation of the disk and the possibility of rotation around the axis. The mechanical properties of the material of the disk provide the possibility of angular displacements and shock absorption of the plates. The elements of fixation of the plates relative to the vertebrae are spear-shaped and placed on their outer side.

The main disadvantages of this design of the endoprosthesis (implant) are:

- instability of the relative spatial arrangement and mobility of the elements of the endoprosthesis due to the significant elasticity of the silicone disk and low wear resistance;

- short service life due to the possibility of ingress of wear products between the movable elements, which leads to their closure between themselves, i.e. to deprivation of their relative mobility;

- the complexity of the installation associated with ensuring the alignment of all parts of the endoprosthesis in the inaccessible space between the vertebral bodies;

- the duration of surgery.

The expected technical results from the invention are:

- an increase in the life of the endoprosthesis due to the exclusion of mobile joints with external friction, subject to dimensional mechanical wear, from the composition of the supporting centering element;

- ensuring the stability of the mutual arrangement of the elements of the endoprosthesis;

- the absence of wear products that enter the tissues of the human body, and therefore, the need to remove them during audit operations;

- simplification of manipulations on its installation;

- reducing the duration of surgery.

The achievement of these results is due to the fact that in the membrane-torsion endoprosthesis of the intervertebral disc containing the upper and lower opposed support plates located on the same axis with sawtooth fixation elements in the vertebral bodies and elastic support-centering elements installed between them, on the inner surfaces of the support plates central circular recesses are made in which the bottom parts of the opposite and coaxially located supporting-centering elements in the form of dish-shaped corrugations are placed membranes, which are attached with their curved edges to the plates, forming hermetic cavities with them, and are interconnected by elastic elements attached to their inner surfaces in the form of flat springs located at equal distances from the axis of the membranes and with the same circumferential pitch, and formed by membranes and the cavity plates are filled with a viscous fluid.

Between the totality of the claimed features of the invention and the expected technical results provided by the proposed invention, there is a causal relationship, which consists in the following.

Firstly, the exclusion from the proposed design of support-centering elements forming kinematic pairs with external friction helps to simplify and stabilize the dimensional parameters of the endoprosthesis, since there is no wear factor, and therefore, its service life and the period of repeated surgery are increased.

Secondly, the absence of wear products that enter the human body eliminates the need for their removal from body tissues during revision operations.

Thirdly, support-centering elements - membranes and flat springs connecting the support plates to each other, ensure the integrity of the structure, which simplifies the installation of the endoprosthesis in the intervertebral space, reduces the operation time and does not require complicated expensive auxiliary tools.

In FIG. 1 shows a sectional design of a membrane-torsion endoprosthesis of an intervertebral disc; in FIG. 2 is a view along arrow A in FIG. one; in FIG. 3 is a view along arrow B in FIG. 2.

The endoprosthesis (Fig. 1) includes two coaxially and oppositely located supporting plates 1 and 2, on the inner facing one another, the surfaces of which are made of the central recesses of round shape 3, and the supporting-centering element, consisting of two dish-shaped corrugated membranes 4 and 5 with the edges 6 bent parallel to the axis, fastened together by torsion flat springs 7 located at equal angular distances ϕ from each other and on the same circle of radius R (Fig. 2). The membranes are attached (by welding, soldering or rolling) with their curved edges to the support plates and form sealed cavities with them, which are filled with a viscous-flowing bioinert substance, for example, medical gel, which increases the damping abilities of the support-centering element.

The outer surfaces of the support plates are equipped with sawtooth fixation elements 8, designed to prevent their movement (shift) relative to the vertebrae after installing the endoprosthesis in the intervertebral space. The teeth are made of different heights and inclined to the side opposite to the installation direction of the endoprosthesis (Fig. 3).

Flat springs forming a torsion-working cylindrical plate torsion having high rigidity in the axial and radial directions provide angular (rotational) relative movement of the plates α _z (Fig. 1), i.e. rotation around Ζ axis through internal elastic torsional deformation, a membrane having high stiffness in the radial direction, provide angular displacement α _x, α _y around respectively X and Y axes (Fig. 2), a well as linear δ _z along the axis Ζ (Fig. 1) - due to elastic bending deformations (deflections), i.e., without external friction, and therefore, without dimensional wear.

The presence in the design of the endoprosthesis of two separately located membranes contributes to the distribution between them of elastic deformations arising in them when working out the required angular displacements α _z , α _y , which reduces the likelihood of fatigue failure and, consequently, increases their service life.

All structural elements of the endoprosthesis are made of bioinert titanium alloys having high elastic properties.

The installation of the endoprosthesis is as follows.

First, the failed disc is removed (osteochondrosis, trauma, hernia). Then, using a sliding device, the necessary intervertebral space is created and deaf paired grooves are used in the vertebral closure plates, which are guides for the fixing elements, open in the direction of the endoprosthesis insertion direction, the endoprosthesis is inserted to the length of the blind grooves (to the stop), which ensures its location in the center vertebrae, and then the fixing elements are inserted into the bone tissue until the supporting plates contact the vertebral body using the previously used device.

Subsequent osteogenesis, i.e. sprouting of bone structures into openings and external open cavities of fixing elements (Fig. 3), reliably fixes an endoprosthesis in vertebral bodies.

The proposed design ensures the reliability of the installation, four degrees of relative mobility (freedom) of the support plates, namely, the angular displacements α _x , α _y , α _z around the Χ, Υ, ос axes, and the linear displacement δ _z along the оси axis, which coincides with the axis of symmetry of the endoprosthesis while blocking their radial (linear) displacements along the X and ос axes.

Claims (1)

A membrane-torsion endoprosthesis of the intervertebral disc, containing the upper and lower support plates opposite on the same axis, sawtooth fixation elements in the vertebral bodies and elastic support-centering elements installed between them, characterized in that central circular recesses are made on the inner surfaces of the support plates, in which placed the bottom of the opposite and coaxially located supporting-centering elements in the form of dish-shaped corrugated membranes, which are attached by their bending edges to the plates, forming sealed cavities with them, and interconnected by elastic elements attached to their internal surfaces in the form of flat springs located at equal distances from the axis of the membranes and with the same circumferential pitch, the cavities formed by the membranes and plates are filled with a viscous fluid.

Images