FR2729557A1 - INTERSOMATIC CAGE TYPE IMPLANT, AND INSTRUMENTATION AND METHOD FOR ITS INSTALLATION - Google Patents

Abstract

An interbody cavity type implant (10) for insertion into a hole provided in a region separating two adjacent vertebral bodies. The implant includes an elongate rigid body and has a generally non-circular cross-section. Said implant is designed to be inserted into a generally cylindrical hole and its front end comprises a plurality of sharp ridges (16a) forming gouges which, by impaction, can shape the hole according to the cross-section of the implant. Instrumentation for positioning the implant is also disclosed.

Description

INTERSOMATIC CAGE TYPE IMPLANT, AND INSTRUMENTATION AND
PROCESS FOR ITS INSTALLATION
The present invention relates generally to intersomatic implants used in spine surgery.

 It relates more particularly to a new rigid interbody cage as well as a tool and a method for its installation.

 Conventionally, such an implant is in the form of a cylindrical body of metal or biocompatible metal alloy. A cylindrical hole is formed using a rotary tool in the intervertebral space, and the implant is positioned in the hole, using a relatively basic ancillary.

This implant and its method of installation, however, suffer from a certain number of drawbacks
First, because of the shape of revolution of the implant, the stability of the position of the latter is not guaranteed.

 In addition, its installation using a nonspecific ancillary is extremely delicate and tedious, insofar as it is particularly necessary, to prepare the hole intended for the implant and to place the implant, to maintain the vertebral bodies suitably separated.

 In practice, it is common that after an operation to place an interbody cage, it takes play, moves and no longer fulfills its function or causes neurological disorders.

The present invention aims to overcome these drawbacks
Thus, the present invention first of all proposes an implant of the intersomatic cage type, of the type intended to be received in a generally cylindrical hole formed in a region separating two adjacent vertebral bodies, and comprising a rigid elongated body, characterized in that it has a section of generally non-circular shape and in that it comprises at its anterior end a plurality of sharp edges forming gouges allowing, by impaction, to conform the hole according to the section of the implant.

 - the cross section of the implant is generally square in shape with rounded corners and in that its front face is generally concave, thus forming four sharp edges forming gouges and for ensuring the entrainment of the bone debris torn off by the edges during impaction.

 - The upper and lower faces of the implant each have a notch intended for the self-stabilization of one implant in its housing.

 - the upper, lower and lateral faces of the implant have a slightly concave profile.

 - The implant comprises in the region of its rear face means for securing an instrument intended for its placement in its housing by a posterior route.

 - The securing means comprise a threaded hole formed centrally in said rear face.

 - The implant further comprises in the region of its rear face means for indexing in the axial direction and in rotation of the implant relative to said instrument.

 - The indexing means comprise a groove formed in said rear face and at the bottom of which is formed the tapped hole.

 - The implant comprises in the region of its front face means for securing an instrument intended for its placement in its housing by an anterior route.

 - The securing means comprise a threaded hole formed centrally in said anterior face.

 - The implant includes a through lumen extending between the upper and lower faces.

 - the upper and lower faces of the implant are oriented parallel.

 - its upper and lower sides of the implant are slightly inclined to one another, so as to restore lordosis.

According to a second aspect of the invention, a combination of an implant of the interbody cage type and of an instrumentation for its placement by posterior route is proposed in a region situated between two vertebral bodies, characterized in that the implant comprises an elongated rigid body having a section of generally non-circular shape and comprising at its anterior end a plurality of sharp edges forming gouges, the implant also comprising at its anterior end a threaded means and an indexing means with complementary shapes , and further characterized in that the instrumentation includes
- a first elongated tool intended for the distraction of the adjacent vertebral bodies between which the implant must be placed;
a tubular guide instrument intended to be placed around the first tool and comprising means intended to be anchored in the vertebral bodies so as to maintain their spacing after distraction, and so as to retain said guide instrument in a position of reference,
a second tool forming a reamer intended to be received in the guide instrument and to form by rotation a cylindrical hole of revolution between the vertebral bodies, and
- A third implant implantation tool by impaction, comprising at one end a threaded means intended to cooperate with the threaded means of the implant and an indexing means intended to cooperate with the indexing means of the 'implant, and intended to be engaged with the implant in the guide instrument.

 Preferably, the first tool comprises a body comprising at one end a distraction part of elongated section, and at the other end a removable handle.

 In a particularly advantageous manner, the tubular guide instrument has an internal section such that it can be engaged practically without play, but with the possibility of rotation, around the first tool.

 According to a preferred embodiment, the tubular guide instrument has at one end two pins intended to be engaged by impaction in the two vertebral bodies.

 Also preferably, the instrumentation further comprises a blind impaction tool cooperating with the end of the guide instrument opposite the pins passing around the homologous end of the first tool, which projects beyond said guide instrument, and through which impacts can be applied to the guide instrument.

 According to an advantageous characteristic, the second tool comprises a body capable of being engaged practically without play, but with the possibility of rotation, in the tubular guide instrument, at a first end of the body being provided a reamer of horstout section equal or lower to that of the body, and at a second end of the body being provided a rotation drive handle.

 According to another advantageous characteristic, the third tool comprises a hollow body capable of being engaged practically without play, but with the possibility of rotation, in the tubular guide instrument, a rod mounted to slide and rotate in the hollow body and comprising at a first end the threaded means in the form of a threaded rod and at a second end a rotary drive wheel for the rod, and said hollow body carries at its end homologous with the first end of the rod the cooperating indexing means with the means of indexing the implant.

The invention also provides a method of placing an implant of the intersomatic cage type posteriorly in a region located between two vertebral bodies, the implant comprising an elongated rigid body having a generally non-circular cross section and comprising at its anterior end a plurality of sharp edges forming gouges, the implant also comprising at its anterior end a threaded means and an indexing means with complementary shapes, the method comprising the steps consisting
(a) using a first elongated tool, distract the adjacent vertebral bodies between which the implant is to be placed;
(b) placing a tubular guide instrument around the first tool,
(c) anchoring the guide instrument in the vertebral bodies so as to maintain their spacing after distraction, and so as to retain said guide instrument in a reference position,
(d) remove the first tool from the tubular guide instrument,
(e) engaging in the tubular guide instrument a second tool forming a reamer and forming by rotation a cylindrical hole of revolution between the vertebral bodies,
(f) removing the second tool from the tubular guide instrument,
(g) mount the implant on one end of a third tool, by rotation, so as to index the position of the implant to that of the tool both angularly and in translation,
(h) engaging the third tool provided with the implant in the tubular guide instrument, and engaging the implant in said cylindrical hole by impaction on the other end of the third tool, said implant digging the cylindrical hole using of its sharp edges forming gouges to adapt it to its own section,
(i) rotate the third tool so as to separate it from the implant, then remove the third tool, and
(j) remove the tubular guide instrument.

 Advantageously, step (c) is performed by impaction to engage two pins provided on the tubular guide instrument respectively in the two vertebral bodies.

Other aspects, objects and advantages of the present invention will appear better on reading the following detailed description of a preferred embodiment thereof, given by way of example and made with reference to the accompanying drawings, in which
FIG. 1 is a top view of an interbody cage according to the invention,
FIG. 2 is a sectional view along the line II-II of FIG. 1,
FIG. 3 is a view according to arrow III in FIG. 1,
FIG. 4 is an elevation view on an enlarged scale of a detail of the cage of FIGS. 1 to 4,
FIGS. 5a and 5b are two side elevation views of part of a tool used in a first step of laying the cage of FIGS. 1 to 4,
FIG. 6 is a partial axial section view of part of the tool used in a second laying step,
FIG. 7 is a view in partial axial section of part of the tool used in a third laying step,
FIG. 8 is a view in partial axial section of part of the tool used in a fourth laying step,
FIG. 9a is a side view of part of the tool used in a fifth laying step,
FIG. 9b is a view in axial horizontal section of the part of the tool in FIG. 9a,
FIG. 10 is a view in partial axial section of part of the tool used in a sixth laying step,
FIG. 11 is a view in partial axial section of part of the tool used in a seventh laying step, and
Figure 12 is a schematic side elevational view of an interbody cage according to an alternative embodiment of the invention.

 It will be noted at the outset that, from one figure to another, identical or similar elements or parts are designated as far as possible by the same reference signs.

 Referring firstly to Figures 1 to 4, there is shown a cage type interbody implant 10 which has the general shape of an elongated body of generally square section with rounded corners. The upper, lower and lateral faces all have an axis concavity, intended to promote the angular stability of the implant.

 The upper and lower faces 11a, 11b of the cage each have a notch 12 intended for stabilizing the position of the implant between two vertebral bodies, this notch ensuring anchoring in the adjacent bone walls and consequently good blocking of the implant against movements in the axial direction.

 This notch is shown in detail in Figure 4, as regards the upper face, and has a series of transverse teeth 12a of symmetrical triangular profile, the apex angle of which is designated by a.

 The end of the implant located on the right in Figures 1 and 3 (so-called anterior end) has a concave face 16, for example in the form of a portion of a sphere.

 This concavity makes it possible to define, at the rounded corners of the implant at the level of this face, four cutting edges which, as will be seen below, act as gouges when the implant is placed. At the center of the concave face 16 is provided an axial threaded bore 17, for purposes explained below.

 The opposite or posterior face of the implant, as shown in Figures 1 to 3, is generally straight. It has over its entire width a shallow transverse groove 13 with straight edges, in the center of which an axial threaded bore 14 is made.

 Finally, the implant 10 is traversed right through, between its upper and lower faces 11a, 11b, by an oblong opening 15 of constant cross section, for the purposes explained below.

We will indicate below preferred dimensions, but in no way limiting, for the interbody cage described above.
overall length: 25 rmn
width: 10.5 mm
height: 10.5 mm
radius of curvature of rounded corners: 2.2 mm
radius of curvature of the axis concavity: 20 rmn
radius of curvature of the concave face 16: 8 rmn
angle at the top has anchor teeth: 900
width of the teeth: 2 mm
tooth height: 1 mm
groove height 13: 5 mm
depth of groove 13: 0.5 mm
We will now describe in detail an instrumentation and a method for placing the implant described above in the space between two vertebral bodies of the human spine, as well as the various functions given by the geometry of Implant.

 First of all, conventionally, the preparation of the route is carried out. Then a partial distraction of the intersomatic space on the side of the disc opposite to that which we are about to treat is carried out, not shown.

 Referring now to Figures 5a and 5b, there is illustrated a distraction tool generally designated by the reference 100, which comprises a main body 102 cylindrical of revolution. At one end of this body extends axially an intermediate portion 104 comprising at its free end a tool in the shape of a spatula 106 of oblong profile, for example elliptical.

 At the opposite end of the body extends axially a rod 108 on which can be removably mounted, for example snapped on, an operating handle 109, the reference 107 designating an unlocking member of said handle.

 It can be seen in FIG. 6 that the latching takes place by involving a groove 108a formed in the rod 108.

The tool 100 as shown in FIGS. 5a and 5b makes it possible, as a first step in the method of placing the implant, to distract the two vertebral bodies
CV1 and CV2 between which the implant must be placed. More precisely, by forcing the spatula 106 into the intervertebral space, and by rotating the tool a quarter of a turn according to arrow F5 in FIG. 5a, the two vertebral bodies are caused to move away from 'an appropriate distance (Figure 5b). This distance, fixed by the width of the spatula 106, is preferably slightly less than the height of the interbody cage to be placed.

 Now with reference to Figure 6, there is illustrated the tool 100 held in the position of Figure 5b, the handle 109 having been removed.

One then engages on the cylindrical body 102 of the tool 100 an instrument generally designated at 110. This instrument comprises a hollow cylindrical barrel 112 whose internal diameter is very slightly less than the external diameter of the body 102 of the tool 100. This barrel comprises at its end facing the spine two pointed pins 113 arranged diametrically, mounted on the barrel by means of a pin-carrying ring, and at its opposite end a handle 114 secured to the barrel 112. We also observe on the Figure 6 that the two pins 113 of the instrument 110 are arranged so as to be located respectively to the right of the two vertebral bodies
CV1, CV2.

 The object of the instrument 110 is, in the course of the fitting procedure, to provide operative guidance by defining an intervention reference axis, and as will be seen below, to keep the vertebral bodies suitably separated l of each other. Note that after engaging the guide instrument 110 on the tool 100, some alignment adjustment can be made to align it relative to the longitudinal axis of the patient.

 Now with reference to FIG. 7, there is shown the instrument 110, the tool 100 contained therein, and another tool generally indicated at 120, intended to allow the application of axial impacts to the instrument 110. This tool 120 has the form of a blind tube, a cylindrical skirt 122 of which surrounds, with play, the end part of the tool 100 which projects through the open end of the instrument 110, and of which a crown portion 124 is located at a distance from the end of the tool 100. The free edge of the skirt 122, opposite the crown 124, comes to rest on the hollow cylindrical body 112 of the instrument 110 at handle level 114.

 Impacts are then applied according to arrow F7 on the top 124 of the tool 120, these impacts being transmitted to the guide instrument 110 to plant the two pins 113 in the respective vertebral bodies CV1, Cv2, in the manner of a nailing. It will be observed that this operation is carried out while the first tool 100 remains in place and ensures the distraction of the two vertebral bodies.

 FIG. 7 shows the position of the instrument 110 at the end of this operation.

 Once this operation has been carried out, the bell 120 is removed, the handle 109 is reassembled on the tool 100 and traction can be exerted on the tool 100 using the said handle to extract the blade 106 from the intervertebral space. , and completely remove the tool 100 from the guide instrument.

 The instrument 110 then constitutes, for the entire continuation of the operations, a tool guide as will be seen below.

 With reference now to FIG. 8, a second tool 130 has been inserted into the guide instrument 110 in place of the first tool 100. This tool comprises a cylindrical body 132 whose diameter is very slightly less than the inside diameter of the barrel 112, a rod 134 extending axially at one end of the body 132 and a reamer 136 provided at the free end of the rod 134.

 At its opposite end, the tool 130 comprises a fixed or removable handle 138. By rotating the tool 130 using the handle 138 and simultaneously exerting pressure on the tool, a cylindrical bore of revolution is made in the space between the vertebral bodies.

The movement of the tool 130 is symbolized by the arrow
F8.

 Preferably, the diameter of the reamer 136 is equal to the overall width and height of the implant 10 described with reference to Figures 1 to 4. These dimensions are chosen so as to be slightly greater than the height intersomatic space, fixed by the width of the spatula 106 of the tool 100. Thus, the reamer removes disc material, and also a small amount of bone material in the vertebral plates.

 Once a hole of suitable depth has been formed (this depth can be controlled for example by a stop cooperating between the tool 130 and the guide 110, or by a graduation formed on the body 132 of the tool 130) , the latter is then extracted from guide 110.

 The following operation consists in mounting the implant 10 on a third tool shown in FIGS. 9a and 9b. The lumen 15 of the implant is previously filled with bone grafts which will be used after placement to establish a bone connection between the two vertebral bodies.

 This tool 140 is presented in two parts, namely an external part comprising a cylindrical barrel 141 and an internal part comprising a cylindrical body 143 which can slide and rotate freely, but practically without play, in the barrel 141.

 The barrel 141 has at its anterior end (on the left in FIGS. 9a and 9b) a non-cylindrical extension, and more particularly an extension 142 limited by two straight edges, the distance of which is very slightly less than the distance between the straight edges of the groove 13 of the implant. In the vicinity of its rear end, the external part of the tool 140 has two wings 148, for the purposes explained below.

 The inner part of the tool 140 comprises, extending axially from the body 143 its anterior end, a threaded rod 144. This threaded rod freely crosses the end of the outer part of the tool 140 in which the extension 142.

A shoulder 146 formed in the outer barrel 141 limits the axial movement of the inner part of the tool.

 At its opposite end, the body 143 is integral with a wheel 145 intended to drive it in rotation.

 The implant 10 is mounted on the tool 140 by screwing the threaded rod 144 into the threaded bore 14 of the implant, while the end 142 of the outer part is kept in alignment with the groove 13 of the implant. The threaded rod 144 is rotated using the wheel 145.

 After tightening, the implant 10 is secured to the tool 140 both in translation and in rotation, thanks to the cooperation of the screwing and the complementarity of shapes between shaped end 142 of the tool and the groove 13.

 The assembly thus obtained, represented in FIGS. 9a and 9b, is engaged in the guide instrument 110.

 Referring now to FIG. 10, it can be seen that the barrel 112 of the instrument 110 has at its rear end (on the right) two notches 112a which are suitable for receiving the wings 148 of the tool 140. In this way, the tool 140 can be engaged in the guide instrument 110 only in a determined angular position, which corresponds to a position of the implant 10 in which the top and bottom walls 11a, 11b are opposite of the two vertebral bodies.

 Axial impacts are then applied to the tool 140, at the level of the wheel 145. These impacts allow the implant to gradually penetrate into the cylindrical bore formed by the reamer (see FIG. 8), the four sharp edges 16a of the implant as described above playing the role of gouges to enlarge in their region. the tapped hole by attacking the bone material of the vertebral bodies. It will be observed here that the concavity of the anterior face 16 of the implant 10 allows, as this machining work progresses, to drive out the bone chips which are released in front of the implant, by accumulating them at the bottom of the hole . It is therefore the implant itself, according to an important characteristic of the invention, which acts as the last tool for its installation. Thus, it is the implant which conforms itself, from a pre- cylindrical hole of revolution, a housing having exactly the same section as the implant, which guarantees its stability.

 Once the implant positioned at the desired depth (determined concretely by the abutment of the wings 148 at the bottom of the grooves 112a), the wheel 145 of the tool 140 is turned to unscrew the threaded rod 144 from the tapped bore 14 and release the tool 140. This movement is symbolized by the arrows Flla. The tool 140 is then extracted from the guide instrument 110, either in a single step, or in two steps (inner part then outer part). Reference will be made to FIG. 11 which illustrates the partial withdrawal of the interior part of the tool 140.

 Finally, by pulling on the handle 114 (arrows Fllb), the guide instrument 110 is separated from the vertebral bodies CV1, Cv2. The two vertebral bodies then tend to come naturally and enclose the implant 10. The notched surfaces 12 thereof are then anchored in the bone material of the vertebral bodies to further improve the stability of the implant.

 It will be observed here that the vertical lumen 15 formed in the implant and filled with grafts before placement makes it possible to ensure, over time, a bone connection through it between the over- and underlying vertebral bodies. It will be noted in this regard that the self-machining action of the implant during its installation makes it possible to ensure cleaning of the faces facing the two vertebral bodies, which will facilitate the taking of the graft.

 Thus, an instrumentation and a method of placing an interbody cage by a posterior route have been described which have a certain number of advantages. The work is done quickly and with great precision, and the stability of the implant once placed is excellent.

 As described with reference to Figures 1 to 3, the implant 10 also has a threaded bore 17 in its anterior face. This bore allows it to be secured by washing with the tool 140, to allow installation by the anterior route when the latter is made necessary. In this case, the housing for the implant is at least partially preformed by hand.

 with reference to FIG. 12, there is shown an alternative embodiment of the implant adapted to a lordosis situation, that is to say to a non-parallelism between the faces facing the two vertebral bodies (case of lumbar vertebrae). In this case, the upper faces 11a and lower 11b of the implant 10 have a certain obliquity with respect to each other, suitable for lordosis.

In this case, the hole made using the reamer has a diameter substantially equal to the smallest height of the implant.

 Of course, the present invention is not limited to the embodiments described and shown, but those skilled in the art will be able to make any variant or modification in accordance with his spirit.

Claims (20)

 1. Implant (10) of the interbody cage type, of the type intended to be received in a generally cylindrical hole formed in a region separating two adjacent vertebral bodies (CV1, Cv2), and comprising an elongated rigid body, characterized in that it has a section of general non-circular shape and in that it comprises at its anterior end a plurality of sharp edges (16a) forming gouges allowing, by impaction, to conform the hole according to the section of the implant.  2. Implant according to claim 1, characterized in that its cross section is of generally square shape with rounded corners and in that its front face (16) is generally concave, thus forming four sharp edges forming gouges (16a) and for ensure the entrainment of the bone debris torn off by the edges during the impaction.  3. Implant according to claim 2, characterized in that its upper and lower faces (lla, llb) each have a notch (12) intended for self-stabilization of the implant in its housing.  4. Implant according to one of claims 2 and 3, characterized in that the upper, lower and lateral faces of the implant have a slightly concave profile.  5. Implant according to one of claims 1 to 4, characterized in that it comprises in the region of its rear face means (14) for securing an instrument intended for its placement in its housing by a posterior approach.  6. Implant according to claim 5, characterized in that the securing means comprise a threaded hole (14) formed centrally in said rear face.  7. Implant according to claim 5 or 6, characterized in that it further comprises in the region of its rear face means (13) for indexing in axial direction and in rotation of the implant relative to said instrument.  8. Implant according to claims 6 and 7 taken in combination, characterized in that the indexing means comprise a groove (13) formed in said rear face and at the bottom of which is formed the tapped hole.  9. Implant according to one of claims 1 to 8, characterized in that it comprises in the region of its anterior face means (17) for securing an instrument intended for its placement in its housing by a anterior approach.  10. Implant according to claim 5, characterized in that the securing means comprise a threaded hole (17) formed centrally in said anterior face.  11. Implant according to one of claims 1 to 10, characterized in that it comprises a through lumen (15) extending between its upper and lower faces.  12. Implant according to one of claims 1 to 11, characterized in that its upper and lower faces (lla, llb) are oriented parallel.  13. Implant according to one of claims 1 to 11, characterized in that its upper and lower faces (lla, llb) are slightly inclined relative to one another. 14. Instrumentation for placing an implant (10) of the interbody fusion type according to one of claims 1 to 13 posteriorly in a region located between two vertebral bodies (CV1, Cv2), the implant also comprising at its posterior end a threaded means (14) and an indexing means (13) with complementary shapes, characterized in that it comprises  - a first elongated tool (100) intended for the distraction of the adjacent vertebral bodies between which the implant must be placed;  - a tubular guide instrument (110) intended to be placed around the first tool and comprising means (113) intended to be anchored in the vertebral bodies so as to maintain their spacing after distraction, and so as to retain said instrument guidance in a reference position,  a second tool (130) forming a reamer intended to be received in the guide instrument and to form by rotation a cylindrical hole of revolution between the vertebral bodies, and  a third tool (140) for placing the implant by impaction, comprising at one end a threaded means (144) intended to cooperate with the threaded means of the implant and an indexing means (142) intended to cooperate with the indexing means of the implant, and intended to be engaged with the implant (10) in the guide instrument.  15. Instrumentation according to claim 14, characterized in that the first tool (100) comprises a body (102) comprising at one end a distraction part (106) of elongated section, and at the other end a removable handle (109 ).  16. Instrumentation according to claim 15, characterized in that the tubular guide instrument (110) 10) has an internal section such that it can be engaged practically without play, but with the possibility of rotation, around the first tool (100) .  17. Instrumentation according to claim 16, characterized in that the tubular guide instrument (110) comprises at one end two pins (113) intended to be engaged by impaction in the two vertebral bodies (CV1, Cv2).  18. Instrumentation according to claim 16 or 17, characterized in that the instrumentation further comprises an impact tool (120) cooperating with the end of the guide instrument (110) opposite the pins passing around the end counterpart of the first tool (100), which projects beyond said guide instrument, - and by means of which impacts can be applied to the guide instrument.  19. Instrumentation according to one of claims 16 to 18, characterized in that the second tool (130) comprises a body (132) capable of being engaged practically without play, but with the possibility of rotation, in the tubular guide instrument, at a first end of the body being provided a reamer (136) of overall section equal to or less than that of the body, and at a second end of the body being provided a handle (138) for driving in rotation.  20. Instrumentation according to one of claims 16 to 19, characterized in that the third tool (140) comprises a hollow body (141) capable of being engaged practically without play, but with the possibility of rotation, in the tubular instrument guide, a rod (143) mounted to slide and rotate in the hollow body and comprising at a first end the threaded means (144) in the form of a threaded rod and at a second end a rotary drive wheel (145) of the rod, and in that said hollow body (141) carries at its end homologous with the first end of the rod the indexing means (142) cooperating with the indexing means (13) of the implant (10 ).