WO2009022069A2

WO2009022069A2 - Device for interconnecting at least three vertebrae

Info

Publication number: WO2009022069A2
Application number: PCT/FR2008/000939
Authority: WO
Inventors: Henry Graf
Original assignee: Henry Graf
Priority date: 2007-07-02
Filing date: 2008-07-01
Publication date: 2009-02-19
Also published as: FR2918261A1; FR2918261B1; WO2009022069A3

Abstract

This connecting device comprises two end screws (1) for the pedicles, at least one intermediate screw (11) and at least two connecting elements (21, 21'), the intermediate screw (11) having a head (13) which is received in a seat of a first intermediate element (41) and which has three degrees of freedom in rotation relative to this seat, whereas there is no degree of freedom in translation between this head and this seat. This first intermediate element (41) has a rod (42) which passes through an orifice in a first connecting element (21) and cooperates with an internal thread (46) of a first bolt (45) having a head which can be received in a seat of a second intermediate element (41') and which has three degrees of freedom in rotation relative to this seat, whereas this head and this seat have no degree of freedom in translation, this second intermediate element (41') having a threaded rod (42') that passes through an orifice in a second connecting element (21').

Description

DEVICE FOR CONNECTING AT LEAST THREE VERTEBRATES BETWEEN

THEY

The present invention relates to a stabilization device for connecting at least three vertebrae together.

Such a device is known which comprises at least two pedicle screws, each of which has a first end secured to a corresponding vertebral body, an enlarged intermediate portion, and a second threaded end. Auxiliary members, provided with an arch for fixing a rod extending between the vertebrae, are arranged on each of the aforementioned bulged portions. A bolt, cooperating with the threaded end of each screw, allows the immobilization of each auxiliary member, once the latter set up appropriately.

This known device, however, has certain disadvantages _* in that it involves a relatively delicate mounting process. Moreover, once implanted, it offers no degree of freedom between the various elements that constitute it. Thus, when forces are exerted on the vertebral bodies, this absence of degree of freedom induces a transmission of these forces over the entire device, so that the latter tends to separate from the vertebrae that it connects and also induces malfunctions in the whole vertebral chain.

The Applicant has remedied these drawbacks by proposing a connecting device for connecting several vertebrae, which is described in FR-A-2812535. For this purpose, there are two end pedicle screws, as well as at least one a medial pedicle screw. The latter is provided with an elongate head, in which are formed two housing whose truncated spherical walls extend in an angular sector greater than 180 °.

In addition, movable elements are provided, each of which connects an end screw with the middle screw. For this purpose, each of these elements comprises a body terminated by a head at the periphery of which is formed an equatorial flat, adapted to cooperate with the spherical walls of the aforementioned housing. This last solution proves relatively satisfactory. Nevertheless, the present invention aims to improve it further, in particular with regard to the mechanical strength of the median screw, as well as the ease of implantation of the entire device. To this end, it relates to a connecting device for connecting at least three vertebrae together, comprising two end pedicle screws, at least one intermediate screw, and at least two connecting members, each of which extends between two adjacent vertebrae, characterized in that each intermediate screw cooperates with a first intermediate element, this screw having a head received in a corresponding housing of the first intermediate element by having at least one degree of freedom in rotation, in particular three, by relative to this housing, whereas there is no degree of freedom in translation between this head and this housing, this first intermediate element having a clean rod to penetrate through an orifice of a first connecting element, this rod being adapted to cooperate with a tapping of a first bolt having a head adapted to be received in a housing of a second element intermediate by having at least one degree of freedom in rotation, in particular three, with respect to this housing, whereas this head and this housing have no degree of freedom in translation, this second intermediate element having a threaded rod, adapted to move to through an orifice of a second connecting element, while being adapted to cooperate with an additional bolt.

According to other features: each head is provided with an equatorial flat surface extending at the periphery of the spherical outer surface of this head, while each housing has a diameter close to that of a corresponding head, while having an outlet whose transverse dimension is less than said diameter, while being close to the transverse dimension of said equatorial flat;

each end screw has a head adapted to be received in a housing of an intermediate end element, this head and this housing having at least one degree of freedom, in particular three degrees of freedom, in rotation relative to each other, while not having any degree of freedom in translation with respect to each other, each end intermediate element having a threaded rod adapted to penetrate through an orifice formed in a connecting element facing, for the purpose of cooperation with a corresponding bolt;

the connecting members are plates;

said plates are flat;

at least one plate is bent.

The invention also relates to a use of the above device, in which the pedicular end screws are implanted, so that they are not perpendicular to each other, in a vertical position. neutral of the patient.

According to an advantageous characteristic, this device is implanted between the sacrum and the fourth lumbar vertebra. The invention finally relates to a use of the above device, in which the pedicular end screws are implanted, so that they are substantially plumb with each other, in a neutral vertical position. of the patient.

According to an advantageous characteristic, this device is implanted between the first and third lumbar vertebrae.

The invention will be described below, with reference to the accompanying drawings, given solely by way of non-limiting examples, in which:

- Figure 1 is a perspective view, illustrating the various components of a connecting device according to the invention; - Figure 2 is a side view, illustrating this device mounted in three adjacent vertebrae; and

- Figure 3 is a side view, similar to Figure 2, illustrating an alternative embodiment of a connecting device according to the invention, implanted in three adjacent vertebrae. Figure 1 illustrates a connecting device for connecting at least three vertebrae together. This device essentially comprises two end pedicle screws 1 and V ₁ a medial pedicle screw 11, two plates link 21 and 21 ', as well as several intermediate elements, adapted to cooperate with both screws and with these plates.

The three screws 1, 1 'and 11 are identical, namely that they comprise a rod 2, 2', 12 intended to be implanted in a corresponding vertebral body, and a head 3, 3 ', 13 comprising a flat part. equatorial 4, 4 ', 14 extending inclined, in that it is not perpendicular to the main axis A, A', A "of each screw.This flat is for example in accordance with the teaching of FR-A-2 812 535.

Each end screw 1 or 1 'is intended to cooperate with a corresponding intermediate element 31 or 31', which comprises a threaded rod 32 or 32 ', and a cup-shaped end 33 or 33'. Similarly, the median screw 11 is intended to cooperate with a first intermediate element 41, which comprises a threaded rod 42 and a cup-shaped end 43. Each cup 33, 33 'or 43 defines a housing 34, 34 or 44, forming an interior volume bordered by truncated spherical walls, whose diameter D is identical to that of a corresponding head 4, 4 'or 14. The aforementioned spherical walls extend in an angular sector greater than 180 ° , so that the transverse dimension d, or width, of the outlet 35, 35 'or 45 of each housing 34, 34' or 44 is smaller than the diameter D of the latter. It should be noted that this transverse dimension d is substantially identical to that of the flat part 4, 4 'or 14. The structure of each intermediate element 31, 31' or 41 is similar to that described in FR-A-2 812 535.

There are also two first flat bolts 22 or 22 ', intended to cooperate with the rod 32 or 32' of each intermediate element 31 or 31 '. In addition, the intermediate element 41 is intended to cooperate, by its threaded rod 42, with a bolt 45, having a substantially spherical shape, so that it defines a tapping 46, and a head 47 on the periphery of which is formed an equatorial flat 48 similar to those 4, 4 'or 14 described above. The diameter of the head 47 is for example identical to that of the head 13, while the dimensions and the orientation of the flat 48 are for example identical to those of the flat 14. There is further provided a second intermediate element 41 ', similar to that 41 described above. Thus, this intermediate element 41 'comprises a rod 42' and a cup 43 'defining a housing 44'. This intermediate element 41 'is adapted to cooperate with an additional flat bolt 45', similar to those 22 and 22 'described above. Finally, it will be noted that each plate 21 or 21 'is hollowed out with two orifices 23 and 23' so as to allow the rods of the various intermediate elements to pass through.

For the mounting of the device of Figure 1, it is first of all to implant the three pedicle screws 1, 1 and 11 in three adjacent vertebrae. Then, each intermediate element 31, 31 'or 41 is secured to the head 3, 3' or 13 of each screw. To this end, each intermediate element 31, 31 'or 41 is first inclined, so that each flat part 4, 4' or 14 extends approximately perpendicular to the main axis of each element. intermediate 31 or 41. It then brings the latter, according to a translation parallel to the main axis. Since the transverse dimensions of the flat 4, 4 'or 14 and the outlet 34, 34' or 44 are identical, this allows the introduction of the head 3, 3 'or 13 in the housing 34, 34' or 44.

The perimeter of the outlet of each housing is substantially rigid, that is to say that it is made of non-deformable material, which has not undergone modification of its geometry since its machining. For this purpose, the intermediate element 31 or 41 may be made entirely of a rigid material, in particular metal. Alternatively, it may be made of a deformable material, such as polyethylene, a rigid ring being attached to the vicinity of the outlet.

Then, each intermediate element 31, 31 'or 41 is rotated around the head 3, 3' or 13, so that the respective main axes of the screws 1, 1 or 11 and the intermediate elements 31, 31 'or 41 are approximately parallel, as shown in Figure 1. Each flat 4, 4 'or 14 is then no longer facing the outlet of the corresponding housing 34, 34' or 44.

Therefore, each intermediate element 31, 31 'or 41 is free to pivot relative to a corresponding head 3, 3' or 13, while not having no degree of freedom in translation relative to this head, since the diameter D of the latter is greater than the transverse dimension d of the outlet of each housing. The mounting operations described above are similar to those explained in FR-A-2 812 535. Then, the rod 32, 32 'or 42 of each intermediate element 31, 31' or 41 is passed through a corresponding orifice 23 or 23 'of a facing plate 21 or 21'. Each flat bolt 22 or 22 'is then applied to the threaded rod 32 or 32' of the intermediate end elements 31 and 31 '. Similarly, the spherical bolt 45 is reported on the threaded rod 42 of the medial intermediate element 41.

Then, the second medial intermediate element 41 'is placed on the head 47 of the spherical bolt 45, in a similar manner as described above. At the end of this operation, this element 41 'is adapted to pivot about the spherical bolt 45, while having no degree of freedom in translation relative to the latter. Finally, the threaded rod 42 'of this intermediate element 41' is passed through the orifice 23 'opposite, and the flat bolt 45' is secured to this threaded rod 42 '.

In Figures 1 and 2, the plates 21 and 21 'are flat, so that, once implanted, it extend substantially parallel to each other. Under these conditions, because of the presence of the two intermediate elements 41, 41 ', the two end pedicle screws 1 and 1 are not in alignment with each other. In this case, the lower pedicle screw 1a is, in FIG. 2, to the right of the upper pedicle screw 1. In this way, the device of the invention can advantageously be implanted in a region of the column which has pronounced lordosis, especially at the three adjacent vertebrae S1, L5 and L4.

In contrast, in the embodiment of Figure 3, the plate 21 'is replaced by a plate 121' which is not right, namely that it has a bend 122 '. In this way, the presence of this elbow compensates for the elevation due to the two intermediate elements 41 and 41 ', namely that the two end screws 1 and 101' are substantially plumb with each other. Such a device can advantageously be used in a region of the column presenting a weak lordosis, for example in the three upper lumbar vertebrae L1 to L3, or even in the dorsal or cervical column.

The invention achieves the previously mentioned objectives. It will first be noted that the device according to the invention allows articulation of each connecting plate 21, and 21 'or 121', with respect to the various pedicle screws. This possibility of pivoting thus reduces the stresses exerted on the screws, which prevents them from becoming disconnected.

In addition, there is a notion of segmentation, namely that the device according to the invention, while extending over several vertebrae, connects two by two. This makes it possible to satisfactorily treat the various pathologies that are likely to affect the spine.

The device of the invention is furthermore easy to implant for the surgeon who handles it.

Finally, this device induces only weak mechanical stresses on the or each median screw. Therefore, the latter does not tend to separate from the vertebra where it is implanted.

Claims

Connecting device for connecting at least three vertebrae together (S1, L5, L4, L3, L2, L1), comprising two end pedicle screws (1, V; 101 '), at least one intermediate screw ( 11), and at least two connecting members (21, 21 ', 121'), each extending between two adjacent vertebrae, characterized in that each intermediate screw (11) cooperates with a first intermediate element (41). ), this screw having a head (13) received in a corresponding housing (44) of the first intermediate element having at least one degree of freedom in rotation, in particular three, relative to this housing, while there is no degree of freedom in translation between this head and this housing, this first intermediate element having a rod (42) adapted to penetrate through an orifice of a first connecting element (21), this rod (42) being clean to cooperate with a tapping (46) of a first bolt (45) p a head (47) adapted to be received in a housing (44 ') of a second intermediate element (41') having at least one degree of freedom of rotation, in particular three, relative to this housing, while this head and this housing have no degree of freedom in translation, this second intermediate element (41 ') having a threaded rod (42') adapted to pass through an orifice (23 ') of a second connecting element (21 '; 121 '), while being adapted to cooperate with an additional bolt (45').

2. Connecting device according to claim 1, characterized in that each head (13, 47) is provided with an equatorial flat (14, 48) extending at the periphery of the spherical outer surface of this head, whereas each housing has a diameter (D) close to that of a corresponding head, while having an outlet whose transverse dimension (d) is less than said diameter, while being close to the transverse dimension (d) of said equatorial flat. 3. Connecting device according to claim 1 or 2, characterized in that each end screw (1, 1 '; 101') has a head (3,

3 ') adapted to be received in a housing (34, 34') of an intermediate end element (31, 31 '), this head and this housing having at least one degree of freedom, in particular three degrees of freedom, rotated relative to each other, while not having any degree of freedom in translation with respect to each other, each intermediate end element (31) having a rod threaded (32) adapted to penetrate through an orifice (23, 23 ') formed in a connecting element (21, 21'; 121 ') opposite, for the purpose of cooperation with a corresponding bolt (22, 22 ').

4. Connecting device according to any one of the preceding claims, characterized in that the connecting members are plates (21, 21 '; 121').

5. Connecting device according to claim 4, characterized in that said plates (21, 21 ') are flat.

6. Connecting device according to claim 4, characterized in that at least one plate (121 ') is bent.