FR2861581A1 - Total intervertebral disc prosthesis has one plate with curved inner surface guide for sliding intermediate element - Google Patents

Abstract

The prosthesis, consisting of upper (1) and lower (2) plates, e.g. of titanium or chrome/cobalt alloy, and an intermediate element (3), has at least one of the plates made with a guide groove or rib (9) on its inner surface along which the intermediate element can slide in a curved trajectory to permit natural rotation of the vertebral joint about its vertical axis. The outer surface (4, 10) of at least one of the plates has a projection that matches the shape of the vertebra in contact with it.

Description

The present invention relates to an intervertebral disc prosthesis for

  replace the natural disk connecting the two vertebrae of the spine.

  The intervertebral discs of the spine consist of: a central element called nucleus pulposus enclosed in a fiber coil called annulus. The disk connects two vertebral bodies and controls the flexion, tilt and rotation movements of the spine. This disc is degraded by time, effort or certain degenerative diseases. This results in a settlement and / or a malfunction thereof. This can lead to different types of pathology causing multiple more or less intense pain as well as more or less significant handicaps.

  The treatment of this type of pathology has long been limited to the removal of the diseased disc with or without fixation of the joint concerned. Today it seems that the replacement of the disc by a mobile element brings a more therapeutic to the operated patient.

  Several types of prostheses have been proposed to replace the intervertebral disk, we can distinguish four families of disc prosthesis: 1 / Prothesis based on elastomeric materials intended to reproduce the movements of the disc but also its damping functions (Patent: WO / 03/003952 ), 2 / prosthesis consisting of two plates (lower and upper) the lower receiving a spherical dome intermediate element fixed thereto and articulating on the upper plates which has a spherical concave shape for receiving 1 o so congruent intermediate element (patent: 2,659,226), 3 / prosthesis consisting of two trays (lower and upper) the lower having a planar upper face on which can slide an intermediate element whose lower face is flat and the upper face is spherical dome to articulate on the lower spherical concave part of the upper plate (patent: W0 / 00/53127), 4 / Prosthesis consists of two concave elements and facing between which is disposed a biconvex lens ensuring the articulation of the two elements (patent DE 30 23 353).

  Elastomer-based prostheses have quickly shown the limits of this type of material in terms of longevity. Indeed, the various tests showed premature deterioration of the elastic elements in the presence. The technique seems to be oriented towards systems using conventional materials in orthopedic surgery (Chrome-Cobalt, high-density polyethylene, titanium).

  The prosthesis (described in the patent 2659226) perfectly allows the flexion and inclination movements of the spine, however it does not allow rotation along a vertical axis (called vertical rotation in the remainder of the document) because the natural axis this rotation is not at all confused with that of the prosthesis. This results in abnormal forces on the elements surrounding the joint (facet joints, ligaments) may cause pain and premature wear of these elements, it also results in a blockage of the vertical rotation of the joint. The adjacent joints must therefore compensate for this lack of rotation by working much more, this is even more true in the case of implantation of prostheses on several disks. Adjacent discs may therefore deteriorate faster resulting in the corresponding pathologies.

  The prosthesis (described in WO000 / 53127) will easily allow the vertical rotation movement of the column through its horizontal plane contact. However, it is easy to understand that this plane contact does not guide the vertical rotation and that it allows translational movements (sliding towards the front of the upper plate) in the horizontal plane generating shear forces on the posterior elements of the plane. the spine (facet joints) The facet joints being particularly hyperalgic element it will result in significant posterior pain.

  The prosthesis (patent: DE 30 23 353) has the advantage of having two moving surfaces improving the qualities of resistance to wear, however its concept presents risks of loosening by the movement of the spacing of the plates during the movements of the 1 o prosthesis.

  Furthermore known prostheses have substantially planar elements in contact with the vertebrae which have no truly flat surfaces. This results in stress concentrations on small surfaces that sometimes cause impaction of the elements in the bodies of the vertebrae in contact.

  The present invention overcomes these disadvantages by providing a solution allowing and guiding the vertical axis rotation of the vertebral joint. This while avoiding pure forward translation movements of the superior vertebra with respect to the lower vertebra, which would induce harmful shear stresses to the posterior articular facets of the vertebral column.

  The present invention is an intervertebral disc prosthesis consisting of three elements, an upper plate, a lower plate and an intermediate element, which according to a first feature has at least one plate which has on its inner surface at least one guide to make slide the intermediate element in a substantially circular arc to allow natural rotation relative to the vertical axis of the vertebral joint, the guidance may be complete or unilateral, that is to say allow a coaptation in one direction only. Furthermore, the guide may have on its ends a flange for preventing the end of travel of the intermediate element. One of the plates has on its inner face a spherical cap in congruent contact with the spherical dome of the intermediate element to prevent translational movements.

  This feature can be broken down according to four non-limiting embodiments: (a) Prosthesis characterized in that the guide is a groove in which is housed a portion of the intermediate element.

  (b) Prosthesis characterized in that the guide is a rail which is housed in a part of the intermediate element.

  (d) Prosthesis characterized in that the guide is a rail of dimension slightly smaller than the groove of the intermediate element in which it is housed, so as to allow a coaptation of the elements.

  In addition, the elements are made of materials already proven in orthopedic surgery to prevent premature deterioration of the elements.

  According to another particular feature, the invention is characterized in that at least one plate has on its external surface a prominent shape (a dome for example) which matches the shape of the vertebral body plate of the vertebra on contact, this is intended to avoid loosening and sinking of the prosthesis.

  According to another feature, the invention is characterized in that at least one plate has on the geometric center of its external face a preferably triangular mark intended to locate the position of the prosthesis in front view and in profile view by ray imaging. X to control the positioning of the prosthesis.

  According to another feature, the invention is characterized in that the lateral wall or walls of the guide have an inclination towards the inside or the outside in order to avoid the expulsion of the intermediate element.

  According to another feature, the invention is characterized in that the upper plate and the lower plate can be reversed.

  According to another feature, the invention is characterized in that the intermediate element can be made in several parts, each having specific qualities: wear resistance, damping for example.

  The elements are made in the materials conventionally used in orthopedic surgery. The trays are made of alloy titanium, stainless steel, chrome-cobalt alloy or ceramic. The intermediate elements are polyethylene, ceramic, or any other material known for its qualities of resistance to wear and damping.

  According to a preferred embodiment, the prosthesis consists of three elements (two plates and an intermediate element); the lower plate has on its upper face an arcuate groove receiving an intermediate polyethylene element which can slide freely along the groove, the upper face of the intermediate element has a convex shape in contact with the lower concave face of the upper shelf. The upper plate has on its upper face a dome positioned substantially in the middle of the surface. Each plate has at the geometric center of its external surface a small flat triangle. In addition, the trays have on their periphery, holes, notches or special shapes for receiving instruments for placing the prosthesis. The materials used for the fabrication of the prosthesis are those generally used in orthopedic surgery, the trays are in titanium alloy or in a chromium-cobalt alloy, the intermediate element is in high density polyethylene or in any other known material for its In terms of wear resistance, the trays will be coated on their outer surface with porous titanium and / or hydroxyapatite.

  The description made with respect to the attached drawings will give a clearer view of the invention and its advantages.

  Figure 1 (case of the solution (a)) represents the prosthesis with a groove (9) in the lower plate (2) in which is housed an intermediate element (3). This is a profile view in section. The vertebrae (101) and (102) in contact are also shown in profile view.

  FIG. 2 (case of the solution (a)) represents the intermediate element (3) and the lower plate (2) with its groove (9) in plan view with the adjacent vertebrae (101) and (102) modeled in order to to define the position of the natural center of rotation of vertical axis (100).

  Figure 3 (case of the solution (a)) represents the prosthesis with the groove (9) in the lower plate (2) in section AA.

  FIG. 4 (case of solution (b)) represents the prosthesis with a rail (9) in the lower plate (2) on which part of the intermediate element (3) is housed in profile view (BB section) implanted between two vertebrae (101) and (102).

  Figure 5 (case of solution (b)) represents the prosthesis lo in section AA.

  Figure 6 (case of solution (b)) represents the intermediate element (3) and the lower plate (2) with its rail (9) in plan view with the adjacent vertebrae (101) and (102) modeled so to define the position of the natural center of rotation of vertical axis (100).

  Figure 7 (case of the solution (c)) represents the prosthesis with the shoulder (9) acting as a guide in the bottom plate (2) in section BB, in profile.

  FIG. 8 (case of the solution (c)) represents the lower plate (2) with its shoulder (9) and the intermediate element (3) in plan view, in addition to the vertical axis of rotation (100) vertebrae is represented.

  Figure 9 (case of solution (d)) shows the prosthesis with the rail (9) in the lower plate (2) and the groove (13) in the intermediate element (3) in section BB, in profile.

  Figure 10 (case of the solution (d)) represents the lower plate (2) with its rail (9) and the intermediate element (3) with its groove (13) oversized, seen from above.

  Figure 11 shows a section of the assembly consisting of the plate (1,2), the guide (9) and the intermediate element (3).

  Referring to Figures 1, 2 and 3 the device relates to the first embodiment (a), it comprises a lower plate (2) in which is cut a groove (9) of shape 1 o curved (in a circular arc for example ), an intermediate element (3) is placed in this groove so that it can slide therein according to the rotational movement (200) axis (100). This intermediate element (3) has on its upper part a convex spherical surface (8) which comes into contact with the upper plate (1) on its inner surface (7) concave spherical. The lower plate (2) has in the middle of its outer surface (10) a projection (5) (triangular for example) intended to be identified by X-ray face control and profile. The upper plate (1) has on its outer surface (4) a domed shape to conform to the shape of the overlying vertebrae plate (101). The upper plate (1) has in the middle of its outer surface (4) a protrusion (5) preferably triangular designed to be identified by a control of the face and X-ray profile. Note in Figure 1 that the upper plate (1) has a rotational movement (300) relative to the lower plate (2) corresponding substantially to the sliding of the articular facets (103) of the vertebrae (101) and (102), it is the bending movement of the column spinal. FIG. 2 shows that the intermediate element (3) describes a rotational movement (200) of axis (100) on the lower plate (2) substantially corresponding to the sliding of the articular facets (103) of the vertebrae (101) and (102). The dome shape (8) of the intermediate element (3) drives in its rotational movement (200) the upper plate (1), it is the rotational movement of the spine. In Figure 3 it is noted that the upper plate (1) describes a rotational movement (400) relative to the lower plate (2). This is the lateral tilt movement of the spine.

  With reference to the drawings in FIG. 4, FIGS. 5 and 6, the device relates to the second embodiment (b). Its characteristics and operation are identical or similar to the first embodiment (a) except that the male and female parts of the guide system between the lower plate and the intermediate element are reversed. Indeed, the lower plate has a rail (9) on which is guided the intermediate element (3).

  Referring to Figs. 7 and 8, the device 25 relates to the third embodiment (c). In this case, the device allows the intermediate element (3) to be guided in rotation of vertical axis (100) relative to the lower plate (2), but moreover, it can slide backwards on the inner surface (15) of the lower plate (2). In these movements it drives the upper plate (1) through the contact between its spherical dome (8) and the inner surface (7) concave spherical upper plate (1). This spherical contact serves as in the previous cases to reproduce the flexion and lateral inclination of the spine.

  Referring to Figs. 9 and 10, the device relates to the fourth embodiment (d). In this case, the device allows the intermediate element (3) to be guided in rotation of vertical axis (100) relative to the lower plate (2), but moreover, it can slide backwards on the inner surface (15) of the lower plate (2). In these movements it drives the upper plate (1) through the contact between its spherical dome (8) and the inner surface (7) concave spherical upper plate (1). This spherical contact serves as in the previous cases to reproduce the flexion and lateral inclination of the spine.

  Referring to Figure (11), the guide (9) preferably has one or side walls having an inclination inwardly or outwardly to prevent expulsion of the intermediate member (3).

  By way of nonlimiting example, the device may have dimensions of 28 mm in length and 35 mm in width with an average height of 10 mm and an angle in profile of 7.

  The invention described above is intended for surgery of the spine.

Claims (9)

  Intervertebral disc prosthesis consisting of three elements, an upper plate (1), a lower plate (2) and an intermediate element (3), characterized in that at least one of the plates (1,2) has on its surface internal (7, 15) at least one guide (9) for sliding the intermediate element (3) in a substantially circular arc to allow natural rotation relative to the vertical axis (100) of the vertebral joint.   2. Prosthesis according to claim 1, characterized in that the outer surface (4,10) of at least one plate has a prominent shape that matches the shape of the vertebra in contact.   3. Prosthesis according to claim 1 or 2 characterized in that the guide is a groove (9, fig 1 to 3) in which is housed a portion of the intermediate member (3).   4. Prosthesis according to claim 1 or 2 characterized in that the guide is a rail (9, fig 4 to 6) which is housed in a portion of the intermediate member (3).   5. Prosthesis according to claim 1 or 2 characterized in that the guide is a shoulder (9, fig 7, 8) allowing the possibility of coaptation of the intermediate element (3).   6. Prosthesis according to claim 1 or 2 characterized in that the guide is a rail (9, fig 9,10) of dimension slightly smaller than the groove (13) of the intermediate element (3) in which it is housed , so as to allow a coaptation of the elements.   7. Prosthesis according to any one of the preceding claims, characterized in that the side wall or walls (11) of the guide (9) have an inclination towards the inside or the outside to prevent the expulsion of the intermediate element (3).   8. Prosthesis according to any one of the preceding claims characterized in that at least one of the trays has substantially at the geometric center of its outer surface a projection (5) for locating and controlling the position of the prosthesis in front view. and in profile view.   9. Prosthesis according to claim 7 characterized in that the projection (5) is a triangular parallelepiped of small thickness.