EP2739222A1

EP2739222A1 - Dynamic fixation intervertebral implant

Info

Publication number: EP2739222A1
Application number: EP12758539.6A
Authority: EP
Inventors: Gilles Dubois; Jacques Senegas
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-08-02
Filing date: 2012-07-26
Publication date: 2014-06-11
Also published as: US20140155940A1; FR2978658A1; WO2013017785A1; FR2978658B1

Abstract

The present invention relates to a dynamic fixation intervertebral implant for stabilizing the lumbar spine on one or more intervertebral segments, including: an interspinous wedge (1); a rigid strip (2) covering a portion of the dorsal surface (8) and two side surfaces (7a), (7b) of the interspinous wedge (1), so as to leave a free passageway at the vertical side channels (3); at least one opening (4) extending through the interspinous wedge from one side surface to the other, at the caudal portion of the rigid strip (2); two pedicle screws (14) including a system for tensioning and fastening a braid (13) passing through the free passageways of the side channels (3) of the interspinous wedge (1); and a rod (12) connecting the two pedicle screws (14) while passing through said at least one opening (4) located at the caudal portion of the rigid strip (4).

Description

INTERVERTEBRAL DYNAMIC FASTENING IMPLANT

The present invention relates to the field of intervertebral implants. It relates to an implant for maintaining the vertebral bodies while allowing a degree of freedom sufficient to allow the movements of the spine in the three planes.

In the musculoskeletal system, the spine performs the functions of stabilizing the trunk and supporting the scapular and pelvic belts. These functions can be altered by natural wear, pathological degeneration or traumatic shock, causing discomfort, pain, gene or even severe disability in the subject with these disorders.

The efficiency and the equilibrium in the static distribution of the charges as mobile are determined by the coordination of the different segments constituting the spine and distributed into functional units. Each functional unit is composed of two adjacent vertebrae connected by an intervertebral disc. Stacked on top of each other, they constitute the spinal joint complex.

To treat damage to the spinal joint complex, various surgical techniques have been proposed such as bone fusion (arthrodesis) or instrumented stabilization of vertebral bodies.

Although accompanied by a loss of mobility of the section of the operated column, vertebral body fusion has long been practiced because of its rapid and effective results. However, studies carried out on patients operated five to ten years after surgery have shown that this technique eventually causes overloads at the junction of the operated area with the appearance of herniated discs, bone sclerosis and sensation of persistent pain. To reduce these disadvantages, the use of implants dynamically fixed to the vertebral bodies has been imagined in certain indications. The purpose of these implants is to provide a flexible system to prevent the fusion of vertebral bodies, through connectors or spacers, fixed by screws placed in the vertebral pedicles, allowing dynamic stabilization. These implants are more particularly intended for the treatment of the lumbosacral spine. An example of this type of device is represented by the Dynesys ^® implant (Zimmer). These implants conventionally comprise a cylindrical thermoplastic spacer fixed at both ends to two adjacent vertebral bodies by means of conical transpedicular screws and traversed by a tensioning cord acting as an artificial ligament. The maintenance of a functional unit by this type of device comprises the fitting of two spacers each fixed on either side of the median vertebral axis by two screws, ie four pedicle screws in total.

This system makes it possible to bring to the patient a stabilization of the column with a good maintenance of the vertebral bodies. The immobilization of the functional unit is reduced compared to bone fusion techniques, allowing the patient to perform certain movements, including sagittal bending / extension, which results in better recovery after the operation due to adapted rehabilitation exercises. The patient can perform column movements of greater amplitude compared to arthrodesis, even if in the end, the mobility remains relatively limited, in particular because of the significant anchoring resulting from the fixation of the four pedicle screws per functional unit.

Other instrumental stabilization devices have been devised, allowing to exonerate the implantation of pedicle screws. An example of this type of device is the Wallis ^® implant (Zimmer). Here, a spacer is interposed between two vertebral bodies, held by a flexible band that encircles the two dorsal processes of the adjacent vertebrae and connected to adjusting tips to adapt the length of the flexible band and able to attach to the main body of the spacer by clipping. This system further improves the mobility of the functional unit thus treated compared to the previous techniques. It has the advantage of allowing minimally invasive and reversible surgery, the implant being easily removable without causing bone damage. On the other hand, the system for fixing to the dorsal processes presents a certain laxity, the tension of the flexible band tending to decrease with the movements of the column, which leads to a decrease in the effectiveness of the implant over time.

In order to overcome the drawbacks of the prior art, the present invention proposes a new implant allowing a dynamic fixation of the vertebral bodies, without bone fusion, having a good vertebral anchorage, so as to offer an effective and durable stabilization over time. one or more functional units, while allowing increased mobility of the spine. One of the objectives of the vertebral implant according to the present invention is to limit the traumatic shock associated with the operation, in particular by reducing the number of pedicle screws used during the surgical procedure. Another objective of the vertebral implant according to the present invention is to provide an intimate and robust fixation system with the vertebral bodies, capable of being easily adjustable to the anatomy of the patient during the operation.

Another objective of the vertebral implant according to the present invention is to allow the stabilization of the vertebral bodies with good rigidity, while allowing the mobility of the column in the three planes of space: the frontal plane for the movements lateral inclination, the sagittal plane for the flexion / extension movements and the transverse plane for the rotational movements of the vertebrae relative to each other. These objectives are achieved by the present invention which relates more specifically to an intervertebral dynamic fixation implant for stabilizing the lumbar spine on one or more intervertebral segments comprising:

an interspinous wedge extending along a vertical axis, comprising two caudal-caudal notches intended to receive the dorsal processes of two lumbar vertebrae Ln and Ln + 1, a vertical channel being formed on the two lateral faces of said interspinous wedge,

a rigid band covering a part of the dorsal surface and of the two lateral faces of the inter-spinous wedge, so as to leave a free passage at the level of the lateral vertical channels,

at least one orifice passing through the inter-spinous wedge from one side face to the other, in part caudal of the rigid band,

two pedicular screws fixed on the lumbar vertebra Ln + 1, comprising a system for tensioning and fixing a Tn braid from enclosing the dorsal process of the lumbar vertebra Ln and passing through the free passages of the lateral channels of the intrathinous wedge,

a rod perpendicular to the vertical axis of the interspinous wedge, connecting the two pedicle screws passing through said at least one orifice located in part caudal of the rigid band.

The interspinous wedge according to the invention has a configuration adapted to allow its perfect insertion between the two vertebral bodies to be treated. For this purpose, the cranio-caudal notches complement the anatomy of the dorsal processes of the vertebrae between which the inter-spinous wedge is placed. A certain degree of freedom exists however between the two dorsal processes because of the dynamic properties inter-spinous wedge, composed of a material having a certain elasticity. The flexion / extension movements of the column on the sagittal plane are thus possible, resulting in a separation or approximation of the two dorsal processes of the same functional unit. Of varying size according to the anatomy of the patient, the length of the interspinous wedge according to the invention is determined by the surgeon according to the operation. As an indication, the interspinous wedge may have a length of between about ten and thirty millimeters, over a width of about ten millimeters. Several compounds can be chosen to achieve the interspinous wedge according to the invention. The selected material must have a certain elasticity, so as to allow the interspinous wedge slight deformations during the movements of the column, including flexion / extension. Those skilled in the art will be able to select the appropriate materials depending on the case to be operated and the greater or lesser rigidity that it wishes to obtain. Plastics and associated polycarbonate urethane or silicone type can be selected. Preferably, the interspinous wedge is advantageously composed of PEEK (polyether-ether-ketone).

The lateral faces of the interspinous wedge according to the invention are hollowed out by a slight unevenness, forming a channel extending on a vertical cranio-caudal axis on either side of said two lateral faces. Measuring approximately one to two millimeters in height, this difference in height makes it possible to receive the braid coming into contact with the lateral faces of the interspinous wedge so that it can be guided by the channel thus formed. The rigid band according to the invention covers a portion of the dorsal surface of the interspinous wedge and the two lateral faces thereof so that it passes above the vertical channel formed in the lateral faces, leaving a free passage in which the braid can pass. In a particular embodiment of the invention, the rigid strip has a U-shape, measuring approximately between forty and sixty millimeters of total length over ten to twelve millimeters in width and 0.8 to one millimeter in thickness.

Fixing the rigid band on the interspinous wedge can be carried out in different ways, for example by clipping or gluing. Advantageously, the rigid band is fixed on the dorsal surface of the interspinous wedge by a screw. The composition of the rigid band may also be variable, insofar as it may play its role of covering the interspinous wedge and in particular the vertical channels present on the lateral faces. Preferably, the rigid band is metal. The lateral faces of the inter-spinous wedge according to the invention have at least one orifice located on each of said faces in caudal part with respect to the rigid band covering the channel of these faces. Preferably, this orifice is located in the vertical channel of the lateral faces on an axis perpendicular to the median axis of the implant according to the invention. Said at least one orifice may have a variable number of shapes. Its function is, in the first place, to allow the passage of the rod perpendicular to the vertical axis of the interspinous wedge.

In a particular embodiment of the invention, said at least one orifice also allows the passage of a Tn + 1 braid enclosing the dorsal process of a lumbar vertebra Ln + 1 connected to another intervertebral dynamic fixation implant also in contact with a lumbar vertebra Ln + 2.

Alternatively, said at least one orifice according to the invention allows the passage of the braid and the rod independently, that is to say through two compartments located in said at least one orifice and separated by a partition.

One of the decisive advantages of the implant according to the present invention is that it allows the stabilization of a functional unit by the fixation of only two pedicle screws each distributed on one and the other of the vertebral pedicles of the same vertebrate. Indeed, unlike the prior art, the two vertebrae Ln and Ln + 1 belonging to the same functional unit are maintained by the implant according to the invention by fixing two screws on the vertebral pedicles of the vertebra Ln + 1 instead of four screws distributed on the vertebral pedicles of the vertebrae Ln and Ln + 1 with the known devices.

The pedicular screws used according to the invention have a system for tensioning and fixing a braid Tn enclosing the dorsal process of the vertebra Ln. In a particular embodiment of the invention, the heads of the pedicle screws have a space capable of receiving a portion of the braid, and by a clamping mechanism well known to those skilled in the art, allow fixing by immobilization of said braid after the surgeon has determined the length of braid necessary for the proper fixation of the implant according to the invention.

The braid according to the invention is thus fixed by its two ends to the two pedicle screws. The body of the braid passes the periphery of the implant according to the invention in contact with the side faces, inside the vertical channels formed thereon and covered by the rigid band. The braid makes it possible to fix the cranial cut in an intimate way to the dorsal process of the vertebra Ln by the tensioning performed by the surgeon during the operation when adjusting the clamping mechanism of the two pedicle screws.

The nature and shape of the braid according to the invention may vary in the limit where it has a flexibility and sufficient strength to ensure its function. It can be in plastic derivatives such as polyethylene terephthalate. Preferably, the braid according to the invention is made of polyester with a flattened shape which favors its grip on the implant and the dorsal process. The attachment of the implant according to the invention is completed by the rod perpendicular to the vertical axis of the interspinous wedge connecting the two pedicle screws to one another by passing through said at least one orifice through the inter-spinous wedge from one lateral face to the other in caudal part of the rigid band. This fixation strengthens the implant grip on the vertebra Ln + 1 and thus consolidates the stability of the functional unit. This original fixation system ensures a complete maintenance of the interspinous wedge, already docked to the dorsal process of the vertebra Ln through the braid Tn. It also limits the lateral bending phenomena associated with vertebral instabilities in the rotation movements of the vertebrae. The rod used to perform this fastening role must be sufficiently strong. It can be made of plastic derived materials such as PEEK or other sufficiently resistant compounds. Advantageously, the rod according to the invention is made of metal such as titanium.

EXAMPLES

The examples and figures which follow illustrate the invention in order to make it more apparent the characteristics and advantages, without however reducing in any way the scope.

FIG. 1: schematic representation of the dorsal surface of an interspinous wedge according to the invention,

FIG. 2: schematic representation of the dorsal surface of a rigid strip according to the invention,

FIG. 3: schematic representation of the dorsal surface of an interspinous wedge covered by a rigid band according to the invention,

FIG. 4: schematic representation seen in profile of an interspinous wedge covered by a rigid band according to the invention, FIG. 5: schematic representation of the dorsal surface of two implants according to the invention fixed on two functional units comprising three vertebrae Ln, Ln + 1 and Ln + 2,

6: schematic view in side view of two implants according to the invention fixed on two functional units comprising three vertebrae Ln, Ln + 1 and Ln + 2.

FIG. 1 shows an example of interspinous wedge 1 according to the invention, seen on its dorsal surface 8. In the shape of a slightly conical X with a cranial width substantially smaller than its caudal width, it has two indentations 5a and 5b respectively partly cranial and caudal. An orifice 10 is provided in the center of the shim to allow the fixing of the rigid strip 2. The material chosen in this example is PEEK.

FIG. 2 represents an example of a rigid strip 2 according to the invention, seen on its dorsal surface 9. Of complementary shape to the interspinous wedge 1, it partly covers the dorsal face 8 of the latter and a part of the two lateral faces 7a and 7b. It also has an orifice 11, located so as to be superimposed on the orifice 10 present on the inter-spinous wedge 1 in order to allow the fixing of the rigid band 2 by screwing. The material chosen in this example is a biocompatible metal. FIG. 3 represents the interspinous wedge 1 covered by the rigid band 2 according to the invention. Note that the rigid band 2 covers the dorsal surface 8 of the interspinous wedge 1 without overflowing on the indentations 5a and 5b, so as not to interfere with their perfect insertion with the dorsal processes of the vertebrae Ln and Ln + 1 to which they must be attached.

FIG. 4 is a profile view of the inter-spinous wedge 1 covered by the rigid band 2 such as in FIG. 3. In this example, the profile of the interspinous wedge 1 is slightly rounded at its ends in order to to better marry the anatomy of the dorsal processes. The left dorsal surface 7a appears, suggesting the vertical channel 3 present on this face, extending from the caudal end to the cranial end on the vertical axis of the interspinous wedge 1. The orifice 4a located in caudal part of the rigid band 2, inside the vertical channel 3, is also visible in this representation. It is in alignment with the orifice 4b located on the right lateral part of the interspinous wedge 1, so as to receive the rod 12.

FIG. 5 represents two implants according to the invention, seen on their dorsal faces, fixed on two functional units comprising three lumbar vertebrae designated Ln, Ln + 1 and Ln + 2. A first implant is fixed between the dorsal processes of the vertebrae Ln and Ln + 1 and a second implant is fixed between the dorsal processes of the vertebrae Ln + 1 and Ln + 2.

The cranial indentations 5a and caudal 5b of the first implant are well inserted respectively in the dorsal processes of the vertebrae Ln and Ln + 1. A braid 13 Tn polyester keeps the notch 5a intimately in contact with the dorsal process of the vertebra Ln passing around it. It then runs along the lateral faces 7a and 7b of the interspinous wedge 1 of the first implant via the vertical channel 3, covered by the rigid band 2 which keeps the braid 13 Tn inside the channel 3. two ends of the braid 13 Tn are attached to the pedicular screws 14 implanted on the pedicles of the vertebra Ln + 1. The fixation of the braid 13 Tn to the pedicular screws is performed by the surgeon during the operation, by a clamping system present on the heads of the pedicle screws 14, so as to tension the braid 13 Tn so that it It tightly encloses the dorsal process of the vertebra Ln to which the interspinous wedge 1 is moored.

The perpendicular rod 12 is also fixed by its two ends to the heads of the pedicle screws 14. Thus, FIG. 5 shows that the first implant makes it possible to stabilize a first functional unit comprising the vertebrae Ln and Ln + 1 by attaching only two pedicle screws resting on the vertebra Ln + 1. The vertebra Ln is intimately linked to the interspinous wedge 1 thanks to the braid 13 Tn, solidarisant the cranial cranial 5a to the dorsal process of this vertebra. Fixing the interspinous wedge 1 of the first implant is completed by immobilizing the ends of the braid 13 Tn pedicle screws 14 implanted on the vertebra Ln + 1. This fixation is further reinforced by the perpendicular rod 12 also immobilized by the pedicle screws 14, passing through the orifices 4a and 4b located on the lateral faces 7a and 7b of the interspinous wedge 1.

The interspinous wedge 1 of the first implant is firmly tied to the vertebrae Ln and Ln + 1 thanks to several attachment points, allowing it to fully perform its role of stabilizing the functional unit. This stabilization is further ensured by the installation of only two pedicle screws, which reduces the traumatic shock associated with this operation and also frees the surrounding space vertebrae thus treated, promoting movement in the three planes of this vertebral joint . A second implant according to the invention is also shown in Figure 5, fixed between the vertebrae Ln + 1 and Ln + 2 of a second functional unit adjacent to the first. In this example, the notch 5a of the second implant is intimately brought into contact with the dorsal process of the vertebra Ln + 1 by means of the braid 13 Tn + 1. This braid could directly embrace the dorsal process of the vertebra Ln + 1 in the same way that the braid Tn of the first implant embraces the dorsal process of the vertebra Ln. FIG. 5, however, illustrates another mode of connection, making it possible to connect the second implant to the first implant by passing the braid 13 Tn + 1 not directly around the dorsal process of the vertebra Ln + 1, but indirectly through the orifices 4a and 4b of the first implant. In this way, a synergy of action of the two implants can occur, contributing to a better stabilization of the two functional units thus treated, by strengthening the docking of the first implant to the dorsal process of the vertebra Ln + 1, and by integral connection between the first implant and the second implant.

FIG. 6 makes it possible to better distinguish the connection of the two implants according to the invention in a profile view. In this example, the braid 13 Tn + 1 passes through the same orifice 4a as the perpendicular rod 12 of the first implant even if, according to the invention, it could pass into an independent compartment situated in the same zone as the orifice 4a. .

It can be seen that the stabilization of the two functional units comprising three vertebrae Ln, Ln + 1 and Ln + 2 by two implants according to the invention only requires the installation of two pedicle screws on the distributed vertebras Ln + 1 and Ln + 2 of each sides of these, four screws in total. This economy does not weaken the fixation of the implants to the vertebrae nor the stabilizing effect thereof, it promotes the mobility of the two functional units thus treated.

Claims

Intervertebral dynamic fixation implant intended for the stabilization of the lumbar spine on one or more intervertebral segments, characterized in that it comprises:

an interspinous wedge (1) extending along a vertical axis, comprising two cranio-caudal notches (5a), (5b) intended to receive the dorsal processes of two lumbar vertebrae Ln and Ln + 1, a vertical channel ( 3) being formed on the two lateral faces (7a), (7b) of said interspinous wedge (1),

a rigid band (2) covering a part of the dorsal surface (8) and of the two lateral faces (7a), (7b) of the interspinous wedge (1), so as to leave a free passage at the level of the channels lateral verticals (3),

at least one orifice (4) passing through the inter-spinous wedge from one side face to the other, in a caudal part of the rigid band (2),

two pedicular screws (14) fixed on the lumbar vertebra Ln + 1, comprising a system for tensioning and fixing a braid (13) Tn,

a braid (13) Tn enclosing the dorsal process of the lumbar vertebra Ln and passing through the free passages of the lateral channels (3) of the interspinous wedge (1), a rod (12) perpendicular to the vertical axis of the interspinous wedge (1), connecting the two pedicle screws (14) passing through said at least one orifice (4) located caudal part of the rigid band (2).

2- intervertebral dynamic fixation implant according to claim 1, characterized in that said at least one orifice (4) comprises two compartments separated by a partition, allowing the passage of a braid (13) Tn + 1 enclosing the dorsal process a lumbar vertebra Ln + 1 connected to another intervertebral dynamic fixation implant also in contact with a lumbar vertebra Ln + 2 and the rod (12) independently.

3- Intervertebral dynamic fixation implant according to claim 1 or 2, characterized in that the wedge-interspinous (1) is made of PEEK.

4- intervertebral dynamic fixation implant according to any one of claims 1 to 3, characterized in that the rigid band (2) is fixed on the dorsal face (8) of the interspinous wedge (1) by a screw.

5- intervertebral dynamic fixation implant according to any one of claims 1 to 6, characterized in that the rigid band (2) is metal. 6- intervertebral dynamic fixation implant according to any one of claims 1 to 5, characterized in that the braid 13 is polyester with a flattened shape.

7- intervertebral dynamic fixation implant according to any one of claims 1 to 6, characterized in that the rod (12) is metal.