WO1998048717A1

WO1998048717A1 - Apparatus for interlocking two contiguous, in particular lumbar, vertebrae

Info

Publication number: WO1998048717A1
Application number: PCT/FR1998/000880
Authority: WO
Inventors: Jean Taylor; Bernard Villaret; Harmodio Herrera
Original assignee: Jean Taylor; Bernard Villaret; Harmodio Herrera
Priority date: 1997-04-30
Filing date: 1998-04-30
Publication date: 1998-11-05
Also published as: IES80150B2; IES970323A2; EP0996383A1

Abstract

The disclosed device comprises means for joining two contiguous vertebrae at their respective pedicular and laminar facets. The invention specifically comprises, for each pair of articular facets, a pedicular implant (1) consisting of a screw (2) with a head (3) containing an inset ball-and-socket joint (5) rotating in the horizontal and frontal planes. The device further comprises a translaminar implant (4) which extends from the cord (22) of the vertebra (L4) through the plate; the end (7) of said implant (4) is inserted into the entire length of a threaded bore (11) completely intersecting the rotating ball-and-socket joint (5). The mechanical locking of the two implants thereby ensures that the two articular facets are joined, and are homologous due to the predetermined position of the ball-and-socket joint and the translaminar implant (4). The paired device allows the procedure to be restricted to only the pedicles of the vertebra concerned by the monosegmental immobilization, thereby ensuring rotatory as well as translatory immobilization. In other words, rotation is neutralized by the two translaminar screws, while translation is secured by the pedicular axis.

Description

DEVICE FOR SOLIDARIZING TWO CONGULATED VERTEBRES, ESPECIALLY LUMBARS

The present invention relates to a spinal osteosynthesis device for securing two contiguous vertebrae, in particular the lumbar vertebrae, with a view to their bone fusion, comprising means for securing the vertebrae at their respective pedicular and laminar facets.

It is known that a healthy intervertebral disc constitutes a viscoelastic joint unit. It allows mobility around a longitudinal axis, and its rotational movements are guided back by the articular facets, biplanes at the lumbar level. Mobility in the sagittal plane occurs in particular during flexion movements. Its control involves, in addition to the disc viscoelasticity, the limiting mechanical action of the antero-median and frontal portion of the articular facets, thus opposing the forces of intersomatic shearing. The posterolateral and sagittalized portion of the facets intervenes, in turn, during lateral movements, performed in the frontal plane.

Ultimately, each segment of lumbar mobility is presented as a triarticular complex in inter-relation. This complex involves, taking the L4-L5 segment as an example: the L4-L5 disc, the upper articular facets of the underlying L5 vertebra and the lower articular facets of the overlying vertebra. The upper facets are directly appended posterior to the vertebral pedicle of L5, an integral part of the functional complex. The lower facets are grafted distally to the infero-lateral part of the L4 blades. Their mean plane is orthogonal to the lamar axis.

These elements constitute an even functional unit arranged symmetrically on either side of the mid-sagittal plane. This set includes successive elements: disc, pedicle, upper and lower joint - blade. The posterior arch of the overlying vertebra locks back the rotational mobility of the anterior segment of the underlying vertebra. The function of the upper pediculo-articular assembly is to oppose the anterior translation of the posterior arch. In certain pathological situations, a release of these "locks" occurs. Segmental mobility deprived of self-control goes beyond its physiological framework. A reaction process tries to remedy this failure. In the event of bankruptcy, the use of surgery becomes a necessary analgesic alternative.

According to a first type of solution proposed, a posterior osteosynthesis is carried out of the spinal segment considered by resorting to a series of pedicle screws connected together by rods or plates, this solution having imposed itself in the indications of posterolumbar lumbar arthrodeses. side. Immobilization of the joints of the fixed segment facilitates the fusion induced by a complementary bone graft. This monoplanar synthesis neutralizes the only frontal plane.

It is in fact a variant of the posterior osteosyntheses initially designed for the correction of scoliosis using rods whose anchors have been made reliable.

These pedicle implants are located in the sagittal plane. The cephalic screws of the assembly are inserted into vertebral pedicles belonging to the functional segment adjacent to the neutralization, which are unnecessarily damaged, which constitutes a significant drawback of this type of device.

Another drawback of these achievements lies in the frequent problems of neo-hinge which they induce, in particular due to the facet degradations above the fused level, caused by the osteosynthesis material.

Furthermore, the stabilization obtained is relative, since the assembly acts as a flying buttress. The addition of transverse extra-osseous inter-pedicular elements stiffens the assembly by securing the implants, preventing "wiper" phenomena. The interarticulo-lamar graft site is reduced because it is occupied by the plates or stems. Furthermore, radiological monitoring of the fusion is difficult given the overlays. Finally, learning a reliable pedicle sight is also deemed difficult. According to a second type of solution proposed, articular facets are joined by means of short transfixing screws.

This system, whose mechanical weakness is obvious, has been improved by the insertion of longer screws, starting from the base of the thorny plants through the blade, then inter-facet, ending at the anterior edge of the transverse, at its pedicle junction.

Such screws have certain advantages: a very satisfactory stabilization is thus obtained, controlling the mobility around a longitudinal axis. This principle applies in particular in cases of instability of disc origin. In addition, stabilization is truly mono-segmental, the neurological risk of the procedure is very low, thanks to the use of a viewfinder, the use of intraoperative radiological control is not necessary. Inter-transverse decortication to prepare the graft bed is not compulsory, the operating time is reasonable, learning the technique is relatively simple, and finally the economic impact of this osteosynthesis is reasonable.

On the other hand these lumbar fixations by translaminar screw present disadvantages.

First of all, such a technique requires beforehand that the blades are intact, and that the facets have been respected during a decompression. In addition, the abseiling through the base of the transverse process is very short. The translaminar screw does not effectively oppose a translational force, which explains the evolutionary failures. Finally, the application of this second technique to cases of facet arthropathies requires the absence of disorientation of the line spacing facet of degenerative origin. This procedure cannot be applied when there is a translational hypermobility combined around the transverse and anteroposterior axes (and in particular degenerative spondylolisthesis). Facet decortication is delicate, because it is necessary to preserve the subchondral bone. The good results of this technique suppose the respect of the indications which are, moreover, very narrow.

The present invention therefore aims to provide an osteosynthesis device for securing the mobility segment of two contiguous vertebrae, in particular lumbar, avoiding the above drawbacks of the two known types of embodiment described.

In accordance with the invention, the spinal osteosynthesis device for securing two contiguous vertebrae comprises, for each pair of pedicle and laminar facets, a transpedicular implant, a translaminar implant and locking means for mechanically joining these two implants in such a way angularly adjustable.

The invention thus achieves a combination of two translamary (or translaminar) and pedicle implants mechanically linked by a bolt system adjustable in several directions.

According to an advantageous embodiment, the pedicle implant is a screw comprising a threaded rod and a head containing an orientable ball joint and suitable for making the connection with the translaminar implant. Thanks to this device, only the pedicles concerned in this monosegmental neutralization are instrumented, which constitutes a first important advantage of the invention.

In addition, the interdependence between laminar and laminar implants combines the mechanical advantages of the two systems, namely rotary and translational neutralization.

The pedicle implant reinforces the anchoring in the portion mobility segment, which is thus armed and exerts a counter-support. Finally, a defect (defect) in the joint or lamina following an enlarged release gesture does not prevent the use of this osteosynthesis procedure. The invention also relates to an arthroplasty device between two articular facets of two contiguous vertebrae L4, L5, one of the facets lying in the extension of a pedicle of a L5 vertebra while the other facet is adjacent to a blade of the other L4 vertebra.

According to the invention, this device comprises a pedicle implant secured to a concave artificial facet, and a translaminar implant secured to a convex artificial facet.

Other features and advantages of the invention will become apparent during the description which follows, given with reference to the appended drawings which illustrate several embodiments thereof by way of nonlimiting examples.

Figure 1 is a side elevational view, in a sagittal plane, on a substantially enlarged scale of a spinal segment consisting of two lumbar vertebrae, equipped with a first embodiment of the osteosynthesis device targeted by the invention. FIG. 2 is a view of the osteosynthesis device of FIG. 1 in a horizontal plane, that is to say a plane transverse to that of FIG. 1.

Figure 3 is a view of the spinal segment of Figures 1 and 2 and its osteosynthesis device in a posterior frontal plane. FIG. 4 is a view in longitudinal section on an enlarged scale of a pedicle screw and of its orientable ball joint forming part of the osteosynthesis device of FIGS. 1 to 3.

Figure 5 is a cross-sectional view along 5/5 of Figure 4. Figure 6 is a partial cross-sectional view of a second embodiment of the osteosynthesis device according to the invention. Figure 7 is a sectional view in partial elevation of a third embodiment of the osteosynthesis device according to the invention.

Figure 8 is a schematic top view of a fourth embodiment of the device according to the invention. Figure 9 is an elevational view in partial section on an enlarged scale of a fourth embodiment of the spinal osteosynthesis device according to the invention.

Figure 10 is an elevational and partial sectional view in a horizontal plane of a complete paired device, including that of Figure 9 and implanted in a vertebra.

FIG. 11 is an elevation view in a frontal plane, on a reduced scale, of the device of FIG. 10.

Figure 12 is an elevational view in partial section of a translaminar viewfinder for performing the aim for the placement of the translaminar implant.

FIGS. 13A and 13B are partial schematic elevation views of two variants of the viewfinder of FIG. 12.

The spinal osteosynthesis device shown in the drawings is intended to mechanically join two contiguous vertebrae, in particular two lumbar vertebrae L4 and L5 (FIG. 1) at their articular facets F (Fig. 2), pedicular and laminar, in order to allow their subsequent bone fusion.

This device comprises, for each of the two pairs of articular facets, a transpedicular implant 1 constituted by a screw comprising a threaded rod 2 as well as a head 3, a translamary (or translaminar) implant constituted by a screw 4, and means for allow a mechanical connection between the translaminar screw 4 and the pedicle screw 1, such as a swivel ball 5, drilled through and through, housed in the head 3, as well as means for hooking the upper part of the screw 4 on the blade, namely a cylindrical head 9 or, more advantageously, a washer 65 with pins 66 and a compression nut 70 (Figures 9-10). The head 3 is tubular, provided at its end with a part

18 factory set; in its wall is arranged a lateral opening 6 through which can penetrate an end 7 with a trocar point of the threaded rod of the translaminar screw 4. This insertion of the end 7 makes it possible to screw the latter in a diametral bore 11 of the ball joint 5, which is extended by a diametrical tubular section 12 coaxial with its bore 11. The latter is therefore dimensioned to receive the threaded end 7 of the corresponding screw 4 after proper angular orientation of the ball 5, which is supported on a spherical seat 13 formed in the head 3. The seat 13 extends at the base of the smooth non-tapped interior wall 3a of the head 3, as well as around an axial hole formed in the threaded rod 2. This hole is profiled, for example polygonally (hexagon) in order to be able to receive a tool (not shown) for screwing the implant 1 into the pedicle of the vertebra L5.

The head 3 is equipped with a means for blocking the ball joint 5 in a determined angular orientation. In the example shown, this means consists of a threaded plug 15 in which is arranged a profiled hole 16 for screwing by means of a tool not shown.

The plug 15 can be screwed into the threaded tubular wall 17 (limited on one side by the opening 6) until the face of the plug 15 facing the ball 5 comes to bear on the latter. Advantageously, on the side facing the ball 5, the plug 15 has a conical profile 18 terminated by a conical or spherical bearing

19 bearing on the surface of the ball 5.

The ball 5 with its lateral section 12 can be oriented in a horizontal plane PH which is that of FIGS. 2 and 4, between a frontal plane PF and a sagittal plane PS with a predetermined angular movement A of the axis OX of its bore 11. On the other hand, the ball 5 is also orientable in the frontal plane PF (plane of FIGS. 3 and 5) between the horizontal plane PH and the sagittal plane PS, with a predetermined angular movement B of its axis OX. The limits of the angular movement A correspond to the abutment, in the plane PH of the wall of the tubular section 12 against the profile conical 18, of the plug 15, these parts being of course adequately sized.

The angular movement A in the horizontal plane PH can be approximately 33 °, while the angular movement in the frontal plane PF can be approximately 65 °. The amplitude of these angular deflections is determined by the dimensions of the opening 6 of the head 3 in the horizontal and frontal planes, by the thickness of the wall of the section 12 and the depth of insertion of the pin 14 in the head. 3.

The edge of the opening 6 contiguous to the threaded rod 2 is delimited by an angular sector 21 for tightening the screw 1, for example with a hexagon, the distance between the upper face of the sector 21 and the center O of the ball joint 5 may be around 2mm, this value not being limiting.

The installation by the surgeon of this system combining a pedicle implant 1, a translaminar implant 4 and ensuring interlamino-pedicle locking by means of the swivel joint 5, is carried out as follows.

Of course, the surgeon removes the articular facet mass from the vertebra L5 beforehand, in order to allow the head 3 of the screw 1 to be housed in its place. A) The pedicle implant 1 is placed according to a codified technique, know by catheterizing the pedicle of the L5 vertebra from the isthmo-articulo-transverse junction. b) The surgeon introduces through the opening 6 the spherical ball joint 5 with its section 12, which takes place just in front of the upper facet-sagittal junction belonging to the segment to be instrumented. c) A viewfinder comes to fit on the ball 5 and makes it possible to automatically guide the introduction of the translamary implant 4 crossing the thorny 22 of the vertebra L4. This guidance is carried out until its end 7 can be screwed into the bore 11 of the ball 5 previously oriented correctly in the horizontal and front planes, at angles included in the above values. d) The second implant 4 penetrates at the junction of the blade 23 and the thorny 22 to move in the direction of the blade, forward, outward and downward, guided in this by a specific ancillary not shown, towards the center of the lower facet of the posterior arch of this mobility segment. The implant 4 thus automatically joins the orientable ball joint 5 in the bore 11 from which it penetrates. e) The lock constituted by the ball joint system 5 is then actuated, joining the two implants 1 and 4. f) The same process is repeated on the controlateral side, in order to set up the second pair of implants 1 and 4 (Figure 2).

According to a second possible embodiment, illustrated in FIG. 6, the device is adapted to allow osteosynthesis to be carried out by a vertebral rod 24. For this purpose the pedicle implant 1 comprises a cage 25 which can be screwed onto a flange 26 of a plug 15 formed of the part 18 and of the pin 14. A cylindrical part 27 inside the cage 25 is provided with a pin 28 adapted to be introduced into the blind hole 50 of the plug 15 and has a semi-recess cylindrical for receiving the spinal rod 24.

The part 27 is introduced, free to rotate about its axis of revolution, above the plug 15.

The device is completed by a second cylindrical part 30 having a semi-cylindrical recess allowing it to cover the rod 24, above the part 27 and inside the cage 25. The part 30 is provided with a pivot 29 passing through a hole in the bottom 31 of the cage 25, and which thus ensures a connection between the latter and the part 30.

This pivot connection allows automatic positioning of the two parts 25 and 30 above the rod 24, during assembly. The cage 25 is screwed onto the upper flange of the plug 15, thus locking the positioning of the rod 24 inside the assembly. The transition from the embodiment of FIG. 4 to that of FIG. 6 implies the change of the plug 15, but retaining the translamary assembly already in place.

A pathological event can lead to a surgical resumption to extend the osteosynthesis by resorting to the implantation of screws 1 in the pedicles of adjacent vertebrae; these screws are connected, in particular, by rods 24, lying in a plane posterior to the translaminar implants. Under these conditions, and without removing the implant 4, the head of the pedicle screw 1 will be capped with the cage 25 acting as an extension and the plug 15 replaced so that the rod 24 comes to bear before being blocked . This adaptability of the invention will allow the possible use of pedicle implants, the properly intraspongeuse portion of which may have undergone a surface treatment capable of making the anchorage more reliable, thanks to an osteogenic induction.

The embodiment of FIG. 7 comprises an extension 40 which can cover the head 3 of the screw 1. This extension 40 consists of three parts: a nut 43 which is screwed onto the external thread 17 of the head 3, a body 44 engaged by its floating base, freely rotatable, in the nut 43, and a threaded pin 33 for fixing the spinal rod 24 in a channel 45 in U of the body 44. This assembly makes it possible to correctly orient the body 44 at the end tightening the nut 43.

FIG. 8 illustrates another possible embodiment of the invention. Considering that the pedicle axis orthogonally supports a concave upper articular facet, which articulates with a lower articular facet, convex, whose vertebral blade 32 constitutes the orthogonal axis supporting it, the same principles of the technique can be used for consider performing a prosthetic facet arthroplasty.

The pedicle implant 34 comprises in this embodiment (FIG. 8) a threaded rod surmounted not by a head, but by a concave facet prosthesis 35. The transiaminary implant 4 receives at its end a convex facet 36, prosthetic, in place of the locked portion in the ball joint 5. This assembly is carried out on the two pairs of facets, the natural facets having previously been removed as shown on the left-hand side of FIG. 8.

The two prosthetic facets 35, 36 are adapted on the support (or rod), respectively transpedicular 34 and translaminar 4, once in place in the manner of a cephalic sphere adapted on a prosthetic femoral rod. The connection can be obtained for example by clipping the facets 35, 36 on respective pins 37, 38 of the implants, coming to fit into conjugated holes 39, 41 of the facets 35, 36. In the embodiment illustrated in Figures 9 at 11, the spinal osteosynthesis device comprises a pedicle screw 51 having a conventional thread adapted to the pedicle P, and its head 52 is provided with a seat 53 formed by a projecting collar allowing the screw 51 to be in support optimum on the basis of the pedicle P of the vertebra. Above the seat 53, the head 52 is extended by a polygonal imprint 54, for example hexagonal, which is in turn extended by a tubular part 55 containing the ball joint 5. The end 55a of the tubular part 55 is threaded and can be capped by a nut 56 making it possible to protect the screw 51. If necessary, this nut 56 can be removed in order to replace it with an element making it possible to mount, if necessary, an adapter capable of receiving interpedicular fixing rods.

The ball 5 can be blocked by a threaded plug 57 which is screwed into the corresponding threaded opening of the tubular part 55. The ball 5 is pierced right through by a threaded hole 58 extended diametrically by an outer barrel 59 orientable in a lateral opening 61, of elongated shape, formed in the tubular part 55. A second opening 60 of oblong shape, is also formed in a location diametrically opposite to that of the opening 61. Thus the translamary screw 62 can pass right through the ball 5 and its barrel 59, as well as the opposite openings 61 and 60, so that its end 63 formed by a trocar tip, can be anchored distally in the vertebra at the pedicle-solid articular transverse junction.

The translamary (or translaminar) screw 62 is constituted by a threaded axis over its entire length, the end opposite to its trocar tip 63 has a profiled imprint 64, for example hexagonal (hexagon), used to hold this screw thanks to a specific instrument not shown, ensuring its penetration through the blade. The end 64 is also provided with a washer 65 with pins 66 which can be slid along the threaded axis 62 to come into contact with the rear face of the thorny. The end of the screw 62 is completed by a locking nut 65, which when the translamary screw 62 is put in place (FIGS. 10 and 11), is applied to the washer 65 and locks the screw 62 in place, exerting a booster effect if necessary.

The ancillary instrumentation intended for installing the osteosynthesis device according to the invention, in particular that of FIGS. 9 to 11, is partially illustrated in FIGS. 12, 13A and 13B. This instrumentation includes a cross-section viewfinder 67 which comprises: a) a handle 68, in T, with tubular body 80, extended by a jacket 69 adapted to cap the head 55 and the hexagonal imprint 54 of the pedicle screw; the handle 68 is removably mounted on the body 80; b) an arm 71 articulated on the handle 68, the distal free end 72 of which is provided with a sheath 79 adapted to be able to support the translaminar implant 62 and allow its introduction into the barrel 59 of the ball joint 5 through a lumen elongated 73 arranged in the wall of the jacket 69 (FIG. 13A). The lumen 73 extends parallel to the axis of the pedicle screw 51, so as to allow the barrel 59 of the ball 5 to be directed around its plane of mobility, frontal, thanks to its end which passes through the lumen 73 , while the end of the jacket 69 comes to bear on the seat 53. The height of the light 73 can vary, as visible in FIG. 13B which shows a variant 74 of this light, shorter than the light 73, in shirt 75.

The arm 71 comprises a proximal part 76 fixed to the handle 68, articulated on the distal part 72 around an axis 77 and to which is fixed a point 78 sized to be able to come into contact with the upper edge of the vertebral blade.

The orientation in the horizontal plane, of the barrel 59, can be achieved by rotation of the pedicle screw 51 about its axis, thanks to the removable handle 68 which can be replaced if necessary, over the shirt 69. The articulation around the axis 77 of the arm 71 allows, thanks to the mobility of the sheath 79, crossed by the threaded translamary axis 62, engaged in the barrel 59, to follow the orientation given to the threaded barrel 59 according to the anatomical topography of the lamar view.

The distal part 72 is correctly positioned as soon as the tip 78 is supported on the upper edge of the vertebral blade. The translamary screw 62 can then be introduced into the barrel 59, the ball joint 5 and pass through the opposite openings 61, 60, as well as an elongated lumen 81 formed in the jacket 69 opposite the lumen 73, in order to come file in the vertebra. The angle taken by the threaded barrel 59 adapts automatically, so that there is a correspondence as a function of the type of adjustment given by the sheath 79 to the barrel 59. The point 78 hung on the proximal part 76 prevents any crossing of the blade in the canal space following the translaminar aiming. The latter is carried out by means of a threaded spindle, introduced by the drilling barrel 59.

The translaminar screw 62 crosses the lateral part of the vertebra to ensure better anchoring. Its threaded axis is cut flush with the clamping nut 65, so that this assembly ensures perfect blocking of the axial mobility of the vertebral segment and cancels it in the horizontal plane. The two translaminar screws 62 (FIGS. 10 and 11) join the pedicle screw 51 seen from the rear at the level of the head. FIG. 11 clearly shows the blocking effect which also operates in the frontal plane. The two translaminar screws 62 are thus secured to the pedicle via the pedicle implant 51. The latter is put in place via a screwdriver (not shown), which adapts to the viewfinder 68, 69 and can slide inside the vertical part (tubular body 80) of this viewfinder.

The invention is susceptible of various variant embodiments. Thus, the attachment of the ball joint 5 with the implants 1 and 4 could be carried out by any means equivalent to the threaded plug 15, which can be produced in a manner different from that shown. Similarly, in the device of Figure 4, the plug 15 can be crimped on the ball 5, the recess 16 being removed. The angular fixing of the ball joint 5 can then be obtained by a pin screwed into the solid plug 15, through a threaded bore (Figure 4).

Claims

1. Spinal osteosynthesis device for bone fusion of two contiguous vertebrae, in particular lumbar (L4, L5), comprising means for securing the vertebrae at their respective pedicular and laminar facets (F), characterized in that it comprises, for each pair of pedicle and laminar facets, a transpedicular implant (1), a transiaminary implant (4) and locking means (5, 15 ...) for mechanically joining these two implants in an angularly adjustable manner.

2. Device according to claim 1, characterized in that the transpedicular implant is a screw (1) comprising a threaded rod (2), and a head (3) containing a ball joint (5) orientable and suitable for making the connection with the translaminar implant (4).

3. Device according to claim 2, characterized in that the head (3) is tubular and in its wall is arranged a lateral opening

(6) through which an end (7) of the translaminar implant (4) can penetrate to be secured with the ball joint (5) housed in the head of the screw (4).

4. Device according to claim 3, characterized in that the ball joint (5) has a tapped diametral bore (11) adapted to receive the threaded end (7) of a screw (4) constituting the translaminar implant, and the head (3) of the pedicle screw (1) is equipped with means for locking the ball joint in a determined angular orientation, for example a threaded pin (14) which can be screwed into the head (3) of screws (1) and come to apply on the ball joint (5).

5. Device according to claim 4, characterized in that the ball joint (5) is extended by a diametrical tubular section (12), coaxial with its threaded bore (11).

6. Device according to claims 4 and 5, characterized in that the ball joint (5) is orientable on the one hand in a horizontal plane (PH) between a frontal plane (PF) and a sagittal plane (PS) with an angular movement predetermined (A) of the axis of its bore (11), and secondly in a frontal plane (PF) between the horizontal plane (PH) and the sagittal plane (PS) with a predetermined clearance (B) of the axis of its bore, the clearance (A) in the horizontal plane being for example 33 degrees approximately while the clearance (B) in the frontal plane is approximately 65 degrees, the amplitude of these angular deflections being determined by the dimensions of the opening (6) of the head (3) of the screw (1) in the horizontal plane and in the frontal plane.

7. Device according to one of claims 2 to 6, characterized in that the ball joint (5) is supported on a spherical seat (13) formed in the threaded rod (2), and the head (3) of ia screw comprises a profiled shape (21) adapted to be able to receive a screwing tool.

8. Device according to one of claims 4 to 7, characterized in that it comprises an extension element (25) covering the head (3) of the pedicle screw (1) and which can be crossed by a spinal osteosynthesis rod (24), this extension being fixed on a blocking plug (15) and containing parts (27, 30) for positioning the rod.

9. Device according to one of claims 4 to 7, characterized in that it comprises an extension element (40) capable of covering the head (3) of the pedicle screw (1), and having a U-shaped channel for receiving 'a vertebral rod (24) fixed in this channel, this extender comprising a body (44) mounted floating on a nut (43) for fixing to the head (3) of the pedicle screw (1).

10. Device according to claim 4, characterized in that on the side facing the ball joint (5), the pin (14) is screwed into a part (18) and is provided with a conical profile terminated by a spherical or conical bearing surface (19) for blocking support on the ball joint.

11. Device for arthroplasty between two articular facets of two contiguous vertebrae (L4, L5) one of the facets lying in the extension of a pedicle of a vertebra (L5) while the other facet is adjacent to a blade (32) of the other vertebra (L4), characterized in that it comprises a pedicle implant (34) secured to an artificial facet concave (35), and a translaminar implant (4) integral with a convex artificial articular facet (36), the joining of the facets with the implants being carried out for example by clipping.

12. Device according to claim 3, characterized in that in the wall of the tubular head (55) is arranged a second lateral opening (60), oblong, which can be crossed at the same time as the first opening (61) by one end (63) of the translaminar implant (62).

13. Device according to claim 12, characterized in that the translaminar screw (62) is formed by a threaded axis of which one end has a profiled imprint (64) to allow the maintenance of this screw by a specific tool, and this end is provided with a washer (65) and with a locking nut (70), the washer being able to be provided with pins (66) for anchoring in the rear face of the thorny machine, the second end of the screw being constituted a trocar tip (63) for distal anchoring in a vertebra.

14. Ancillary instrumentation intended for fitting the osteosynthesis device according to any one of claims 1 to 13, characterized in that it comprises a translaminar viewfinder which comprises: a) a tubular handle (68, 80), extended by a jacket (69) adapted to cap the head (55) of the pedicle screw (51) and on which the handle is removably mounted, b) an arm (71) articulated on the handle, the distal free end of which ( 72) is adapted to be able to support the translaminar implant (62) and allow its introduction into a barrel (59) of the ball joint (5) through a lumen

(73) of the shirt.

15. Instrumentation according to claim 14, characterized in that the articulated arm (71) of the viewfinder comprises a proximal part (76) fixed to the handle (68), articulated on the distal part (72) and to which is fixed a point (78) sized to be able to come into contact with the upper edge of the vertebral blade.

16. Instrumentation according to claim 15, characterized in that it further comprises a screwdriver which can be introduced in translation inside the tubular handle (68) of the viewfinder after the jacket (69) of the latter has capped the head (53) of the pedicle screw (51) in order to screw said screw.