Spinal stabilization device

Abstract

The invention relates to a spinal stabilization device comprising at least two screws, each with a first section that can be inserted into a vertebra and a second threaded section separated by a flange; at least one connecting rod for joining the second sections of the screws; and at least one fastening assembly and a second fastening assembly for attaching the rod to the screws. Each fastening assembly comprises at least one clamp arranged to clamp the first rod and a nut. The clamp comprises a first jaw and a second identical jaw held together by an elastic element. According to one embodiment of the invention, the device may include a third fastening assembly with at least one clamp having a first jaw and a third jaw, the latter having an inner surface identical to that of the first jaw and an outer surface complementary to that of a second jaw. FIGURE IN ABRIDGED FORM: [Fig. 1]

Description

Title of the invention: Spinal stabilization device

[0001] BACKGROUND OF THE INVENTION

[0002] The present invention relates to the field of surgical implants and more particularly to spinal stabilization devices implanted in a human or animal body for the treatment of spinal pathologies.

[0003] There are many spinal stabilization devices whose general principle is to connect adjacent vertebrae by rods.

[0004] In a first type of device, the rods (sometimes also called bars) are fixed on either side of the vertebrae to be connected along a plane substantially parallel to the median sagittal plane of the spine. This device provides very good stabilization of the vertebrae relative to one another but significantly limits spinal mobility, hindering or even preventing certain patient movements. According to this first device, the rods are inserted directly into the heads of pedicle screws, which requires that the screw heads be perfectly aligned with each other, which is sometimes difficult to achieve.

[0005] In a second type of device described in document WO-A-2018 / 019792, the rods are fixed to the vertebrae in such a way that they cross on the median sagittal plane of the vertebral column. This latter device allows for some mobility between the two vertebrae connected by the device while reinforcing their stability. The rods have a first end in the shape of a circular ring and a second end in the shape of an oblong ring. During placement, the rings are respectively engaged on threaded sections extending from the pedicle screws screwed directly into the vertebrae. The vertebrae are permanently fixed by screwing a nut onto each threaded section to lock the rod ring by tightening, thus fixing the position of the rod relative to the pedicle screws. This fixing principle, although simple, is rather difficult to adjust precisely.Furthermore, when tightening the nuts, there may be a slight displacement of the rod around the fixing elements, altering the initial adjustment made by the surgeon.

[0006] It is therefore understood that spinal stabilization devices must allow for the stabilization / fixation of the vertebrae while attempting to preserve as much mobility as possible for the patient. These devices must also allow the surgeon to adjust them as precisely as possible. Documents FR-A-2 865 377, WO-A-98 / 55038, and EP-A-1 665 994 thus present devices comprising a pedicle screw screwed into a vertebra. The head of this screw is shaped so that it can accommodate a pin onto which a clamp is engaged, which grips one end of a rod. The adjustment is made possible by the movement relative of the pawl with respect to the screw.

[0007] The main disadvantage of these different systems is that they involve many parts to be assembled, which increases the costs of said devices and lengthens the duration of interventions.

[0008] SUBJECT OF THE INVENTION

[0009] The invention aims in particular to overcome at least in part the aforementioned disadvantages by proposing a spinal stabilization device that is compact, made up of few parts and whose implantation is easy and quick. Summary of the invention

[0010] For this purpose, a spinal stabilization device is provided which includes:

[0011] - at least two screws, each having a first threaded section for being engaged in a vertebra and a second threaded section separated from the first threaded section by a collar;

[0012] - at least one first connecting rod having two opposite ends for connecting the second threaded sections of the screws to each other; and

[0013] - at least one first fastening set and a second fastening set to fix the ends of the rod to the screws, each fixing assembly includes at least one clamp, engageable on the second threaded section of one of the screws and arranged to clamp one end of the first rod, and a nut which has a lower bearing surface and which is arranged to be screwed onto the second threaded section by clamping the clamp against an upper surface of the screw flange.

[0014] According to the invention, said at least one clamp comprises a first jaw and a second jaw identical to each other, held together by an elastic retaining element. The first jaw has an inner surface opposite an inner surface of the second jaw. The inner surface has, at the level of a first connecting portion of each jaw, a recess and a projection of complementary shapes, the first connecting portions being engaged with each other to form a hinge.

[0015] Thus, the vertebral stabilization device according to the invention comprises only four different parts: a screw, a rod, two jaws, and a nut. The surgeon can therefore stabilize at least two vertebrae using at least one stabilization device according to the invention. Vertebral stabilization is easily achieved by means of rods simply fixed by the clamps of each fixation assembly, said clamps being composed of two identical jaws whose first joined parts form a hinge. Vertebral stabilization is achieved either in a crossed configuration on a median sagittal plane of the vertebral column or according to a conventional mounting of the rods on a plane parallel to the median sagittal plane of the spine. The device according to the invention allows not only easier and more reliable fixation of the rods but also for re-assembly in surgical patients, for example, by extending the assembly, without having to disassemble the entire device as is necessarily the case with currently available instrumentation. Furthermore, due to its small number of different parts, it is more economical to manufacture and easier and faster to assemble during surgery.

[0016] Preferably, the first part of each jaw comprises two semi-cylindrical surfaces of the same diameter and length, extending from one another and located within the width of the jaw, the first semi-cylindrical surface forming the projection, the second semi-cylindrical surface forming the recess. Thus, when two jaws are assembled facing each other, the first projecting semi-cylindrical surface of the first jaw fits into the second recessed semi-cylindrical surface of the second jaw, while the second recessed semi-cylindrical surface of the first jaw fits into the first projecting semi-cylindrical surface of the second jaw to form a hinge.

[0017] Each jaw includes, opposite the first part, a second part for connecting to the rod, which has a hollow receiving surface, preferably hemicylindrical, which is arranged to receive a portion of the rod and which has a depth less than a radius of the rod.

[0018] Preferably, the hollow hemicylindrical receiving surface of the second part of the connection to the rod has an axis parallel to an articulation axis of the hinge formed by the first part of the jaw.

[0019] Each jaw further comprises, besides the first part, a third part for connecting to the screw which has a through-cylindrical-truncated conical bore. The cylindrical-truncated conical bore has a larger diameter adjacent to an outer surface of the jaw, opposite the inner surface, and a smaller diameter adjacent to the inner surface of said jaw.

[0020] Each jaw preferably has the outer surface which is convex in shape in a spherical cap and which is complementary to that of the upper surface of the collar or nut.

[0021] The cylindrical-truncated conical drilling of the jaws as well as the convex shape in spherical cap of their respective outer surface makes it possible to create a ball joint between the clamp and the second screw section on the one hand between the collar and the clamp and on the other hand between the clamp and the nut, which allows the surgeon to adjust the stabilization device extremely precisely to the operated patient.

[0022] When the stabilization device is used to stabilize a vertebra not to another vertebra but to at least two other vertebrae, the stabilization device The vertebral joint according to the invention comprises at least a second connecting rod and a third fastening assembly. This third fastening assembly includes at least one clamp, which engages on the second threaded section of one of the screws and is arranged to clamp one end of the second rod. The clamp comprises a first jaw and a third jaw. The third jaw has an inner surface identical to the inner surface of the first jaw and an outer surface with a concave, spherical cap shape complementary to a convex outer surface of a second jaw.

[0023] The device according to the invention thus makes it possible to stabilize at least two vertebrae in a plane parallel to the median sagittal plane or in a crossed manner with the same device, with a high degree of adjustment precision. The device according to the invention also allows for easy readjustment of said device, for example, following a change in the patient's condition. Furthermore, the small number of parts composing the device allows for faster assembly, while reducing its manufacturing cost.

[0024] Other features and advantages of the invention will become apparent from the following description of particular, non-limiting embodiments of the invention. Brief description of the drawings

[0025] Reference will be made to the attached drawings, among which:

[0026] [Fig. 1] [Fig. 1] is a schematic, slightly perspective view of a spine of which two vertebrae are fitted with the device according to the invention;

[0027] [Fig.2] [Fig.2] is a schematic slightly perspective view of a clamp of a first or second fixing assembly composed of two identical jaws;

[0028] [Fig.3] [Fig.3] is a schematic, slightly perspective view of a bit;

[0029] [Fig.4] [Fig.4] is a schematic exploded and perspective view of two jaws identical to form a clamp of a first or second fastening assembly;

[0030] [Fig.5a] [Fig.5a] is a schematic longitudinal cross-sectional view of a screw of a fastening device during assembly, without a nut;

[0031] [Fig.5b] [Fig.5b] is a schematic longitudinal sectional view of a screw of a fastening device during assembly, with nut;

[0032] [Fig.6] [Fig.6] is a schematic view in slight perspective of a spacer;

[0033] [Fig.7] [Fig.7] is a schematic, slightly perspective view of a spine of which three vertebrae are fitted with the device according to the invention;

[0034] [Fig.8] [Fig.8] is a schematic slightly perspective view of a clamp of a third fastening assembly;

[0035] [Fig. 9] [Fig. 9] is an exploded perspective view of a screw comprising a third fastening assembly consisting of two clamps, the first clamp bearing against the collar being composed of two identical jaws, the second clamp located between the first clamp and the nut is composed of a first and a third jaw;

[0036] [Fig. 10] [Fig. 10] is a schematic perspective view of a screw comprising a third fastening assembly composed of two clamps, the first clamp bearing against the flange being composed of two identical jaws, the second clamp located between the first clamp and the nut being composed of a first and a third jaw. DETAILED DESCRIPTION OF THE INVENTION

[0037] With reference to Figures 1 to 6, according to a first embodiment, the invention relates to a vertebral stabilization device, here illustrated for the stabilization of two adjacent vertebrae Va and Vb, comprising: - at least two screws; 1b; each fitted with a collar 2; - at least one first connecting rod 3; - at least one first set of Fa fixings and a second set of Fixing Fb for fixing the ends of the rod 3 respectively to the screws 1a and 1b. Each fixing assembly includes at least one clamp 5a, 5b, which can be engaged on the second threaded section 1.2 of one of the screws and arranged to clamp one end of the rod 3, and a nut 8.

[0038] According to the example of a spinal device shown in [Fig.1], two adjacent or non-adjacent vertebrae Va, Vb are stabilized with a vertebral stabilization device according to the invention, the rods of which cross along the median sagittal plane.

[0039] Here, the device comprises two screws referenced la, l'a on vertebra Va, two screws 1b, l'b on vertebra Vb. All screws 1, 1' are identical, the letters a, b only serve to distinguish the screws according to the vertebra on which they are implanted, the apostrophe allowing to distinguish the screw implanted on the right (without apostrophe) from the screw implanted on the left (with apostrophe) of the median sagittal plane.

[0040] Each screw, here monobloc and in one piece, comprises a first threaded section 1.1, not shown in [Fig.1] and visible in figures 5a or 5b, to be engaged in the vertebra and a second threaded section 1.2 separated from the first threaded section 1.1 by a collar 2.

[0041] The vertebrae Va, Vb to be instrumented are generally prepared beforehand before receiving the stabilization device. Typically, the articular or spinous processes of the vertebrae may have been previously reduced or resected in whole or in part, and the vertebrae pre-drilled to receive the screws 1. The first section 1.1 is completely inserted into the vertebral bone up to the collar 2. The collar 2 is thus on the surface of the vertebra, resting on the bone, with the second section of the screw 1.2 protruding from the vertebra. The surgeon knows how to drill and correctly position the screws 1 according to the patient's anatomy.

[0042] A person skilled in the art will know how to shape the first section 1.1 to facilitate its insertion into the bone. For example, the first section may be self-tapping and have a pointed end. Alternatively, the first section may also be self-drilling.

[0043] The collar 2, which separates the first and second sections 1.1; 1.2 of the screw 1, has a convex lower surface, shaped like a spherical cap, in contact with the vertebral bone, and a concave upper surface, also shaped like a spherical cap, bearing against the clamp. Those skilled in the art will be able to adapt the diameter, height, and convexity of the collar according to the patient's anatomy and the tightening force exerted when the collar is brought into contact with the bone.

[0044] The second section 1.2 of the screw 1 thus protrudes from the vertebra when the screw 1 is fixed. The thread of the second section 1.2 is designed to receive a fastening assembly F. The second threaded section 1.2 has an end portion arranged to allow rotational contact with a screwing tool. The end portion, shown only in [Fig. 1], may include a recess 1.3 with a shape complementary to that of a screwdriver tip. By way of non-limiting examples, the recess may be hexagonal, cruciform, star, or triangular. In addition, the second threaded section 1.2 may have a breakaway feature 1.4 visible in [Fig. 6] to allow the end portion of the second threaded section to be separated by breakage when the surgical procedure is completed.

[0045] The screw is here monobloc and in one piece between the first screw section 1.1, the collar 2 and the second screw section 1.2. It is made of biocompatible and stainless material sufficiently resistant mechanically and chemically for the intended application.

[0046] A person skilled in the art will be able to determine the diameter and length of the screw best suited to the patient's age, morphology, and bone quality. For example, screw lengths typically range from 30 mm to 90 mm.

[0047] According to the embodiment illustrated in [Fig. 1], the device comprises two rods 3a, 3b. Each rod has two opposite ends to connect the second threaded sections of two of the screws. Thus, when vertebral stabilization is achieved by crossing the rods on the median sagittal plane, a first connecting rod 3a will connect the second section 1.2a of the screw 1a implanted in vertebra Va to the right of the median sagittal plane to the second section 1.2b of the screw 1b implanted in vertebra Vb to the left of the median sagittal plane, and a second connecting rod 3b will connect the second section 1.2a of the screw 1a implanted in vertebra Va to the left of the median sagittal plane to the second section 1.2b of the screw 1b implanted in vertebra Vb to the right of the median sagittal plane.

[0048] Alternatively, when stabilization is performed parallel to the median sagittal plane, rod 3a will connect the second threaded section 1.2a of screw 1a to the second threaded section 1.2b of screw 1b, screws 1a and 1b being implanted respectively in vertebrae Va and Vb, both to the right of the median sagittal plane. Rod 3b, for its part, will connect the second threaded section of screw 1.2a of screw 1a to the second section of screw 1.2b of screw 1b, respectively implanted in vertebrae Va and Vb to the left of the median sagittal plane.

[0049] Each rod 3a, 3b is made of a biocompatible material sufficiently rigid to stabilize the vertebrae relative to each other. For example, a material with a Young's modulus between 3.6 GPa and 60 GPa may be chosen. As an example, the material could be a composite material comprising a mixture of carbon fibers and polyetheretherketone (PEEK). Each rod 3 has a constant cross-section, here circular along its entire length.

[0050] A person skilled in the art is able to determine the diameter of the rod cross-section based on the material used, the desired mechanical characteristics, and the patient's anatomy. They will also be able to determine the rod length to adapt it to the patient's morphology and pathology, depending on whether the rods are placed parallel to the median sagittal plane or whether they cross over it.

[0051] Preferably and according to the particular embodiment of the invention, the rods are curved, thus facilitating their placement and limiting interference with the central part of the stabilized vertebrae.

[0052] The fixing of each end of the rods 3 to one of the screws la, 1b is ensured by a fixing assembly F engaged on the second threaded section 1.2a; 1.2b of the screw la; 1b.

[0053] The fastening assembly comprises at least one clamp 5. The clamp 5 consists of two identical jaws 5c and 5d held together by an elastic retaining element. The letters c and d distinguish the first jaw from the second, as well as the elements relating to them. It should be noted that the two jaws 5c and 5d are strictly identical. Each jaw 5c, 5d comprises an inner surface 5c.1; 5d.1 and an outer surface 5c.2; 5d.2 extending parallel to each other, and three parts: a first part for connecting to the other jaw 5c.3, 5d.3; a second part for connecting to the rod 5c.4, 5d.4 opposite the first; and, between the first and second parts, a third part 5c.5, 5d.5 for connecting to the screw 1.

[0054] More specifically, and as particularly illustrated by Figures 2 to 6, the inner surface 5.1 of each jaw 5 comprises, at the level of a first connecting portion 5.3 to the other jaw, a recess 5.31 and a projection 5.32 of complementary shapes. Preferably, the recess and the projection are semicylindrical in shape with identical diameter and length, and extend in line with each other in the Jaw width 5. Thus, when jaws 5c, 5d are assembled, the inner surfaces 5c.1, 5d.1 are aligned, and the recess 5c.31 and the projection 5c.32 of the first jaw 5c cooperate in a complementary manner with the projection 5d.32 and the recess 5d.31 of the second jaw 5d, respectively. The first connecting parts of each jaw 5c.3, 5d.3 are thus engaged with each other to form a hinge, allowing the jaws 5c, 5d to articulate with respect to each other along an axis of rotation corresponding to the central axis of the projections and recesses of the first parts 5.3c, 5.3d. Here, for illustrative purposes, the diameter of the projection (and therefore of the recess) is approximately 2 mm.

[0055] In contrast to the first part 5.3, each jaw comprises a second connecting part 5.4 to the rod 3. This second part 5.4 has a recessed receiving surface 5.41, arranged to receive a portion of the rod 3, which has a depth equal to or less than half the cross-section of the rod 3. The receiving surface 5.41 is preferably shaped so as to have an axis parallel to the articulation axis of the hinge formed by the first part 5.3. Thus, when the portion of the rod 3 is placed between the receiving surfaces 5c.4, 5d.4 of the two jaws 5c, 5d, said portion of the rod 3 is perfectly held since it is pinched (or even slightly crushed) between the two jaws 5c, 5d, thus preventing the portion of the rod 3 from coming out of the clamp 5 once the device according to the invention is installed on the patient's vertebrae. Here, the rod 3 having a circular cross-section between 4 and 6 mm, the hollow receiving surface 5.41 is semicylindrical with a radius identical to that of rod 3.

[0056] Each jaw further comprises, besides the first part 5.3, a third connecting part 5.5 to the screw 1. This third part 5.5 is more or less parallelepiped-shaped and has a through-cylindrical-truncated conical bore 5.51. The through-cylindrical bore is formed such that the larger diameter is adjacent to the outer surface 5.2 of the jaw 5 and, conversely, the smaller diameter of the bore is adjacent to the inner surface 5.1. The inner surface 5c.1, 5d.1 of the third connecting part is flat, while the outer surface 5c.2, 5d.2 is shaped into a convex spherical cap 5.52 complementary to the upper surface of the flange 2 or the nut 8.

[0057] The clamp is formed by assembling the two jaws 5c, 5d, their respective inner surfaces 5c.1, 5d.1 being placed opposite each other. With the two jaws thus assembled, the three parts 5c.3, 5c.5, 5c.4 of the first jaw 5c are aligned with the three parts 5d.3, 5d.5 and 5d.4 of the second jaw 5d. The first part 5c.3 of the first jaw 5c complements the first part 5d.3 of the second jaw 5d to form the hinge of the clamp. The frustoconical hole 5c.51, 5d.51 in each jaw of the third part 5c, 5d allows for a through hole in the clamp 5 to be engaged on the second screw section 1.2. Figuratively speaking, the hole in the The clamp has a diabolo shape. The common center of rotation of the clamp in contact with the nut and the collar is located at the center of the clamp. Finally, the second parts 5c.4 and 5d.4 of the jaws 5c, 5d form a housing for a rod end 3 into which the rod end is fixed.

[0058] The two assembled jaws are joined by the elastic retaining element, here a spring-loaded metal clip 6, fixed in such a way that the jaws are movable relative to each other between an open and a closed position, positions permitted by the hinge formed by the complementarity of the first parts 5.3 of each jaw. The clip 6 is in the form of a plate having two opposing edges, each provided with a pair of tabs 6.1 which respectively grip, for the first pair of tabs, a portion of the outer surface 5c.2 of the first part 5c.3 of the first jaw 5c and, oppositely, for the second pair of tabs 6.2, a portion of the outer surface 5d.2 of the first part 5d.3 of the second jaw 5d. Clip 6 aligns and presses the jaw assembly 5c, 5d, thus forming the clamp 5. The opening of the clamp facilitates the insertion of the rod 3 into the housing formed by the second parts 5c, 4c, 5d.4 of the jaws 5c, 5d of the clamp 5 thus assembled. A person skilled in the art may use any type of clips to secure the first parts of each of the jaws.

[0059] The nut 8 is arranged to be engaged on the second screw section 1.2 and to clamp the clamp 5 against the collar 2 once said clamp 5 has been engaged on the second screw section 1.2 and the rod 3 positioned by the surgeon. The nut 8 comprises an inner surface 8.1 opposite the outer surface 5d.2 shaped as a concave spherical cap of the clamp 5.

[0060] Thanks to the ball joint created by the diabolo shape of the bore of the two jaws 5c, 5d, and the concave shapes of the surfaces of the collar 2 and the nut 81 opposite the outer surfaces of the two jaws respectively, and of the outer surface 5c2 in contact with the collar 2 and the outer surface 5d2 opposite the inner surface 81 of the nut, the surgeon can very precisely adjust the angular positioning of the clamp relative to the screw to obtain a rod positioning perfectly adapted to the patient. Indeed, the clamp 5 forms a partial sphere with the outer surfaces 5c2, 5d2 of the jaws 5c, 5d, the center of which is located equidistant from the jaws 5c, 5d.

[0061] The fixation assembly F may, if deemed necessary by those skilled in the art and depending on the patient's anatomy, include a spacer 11 which may be placed either between the collar 2 and the clamp 5, or between the clamp 5 and the nut 8. The spacer 11 has its ends shaped so as to maintain the ball joint connection between the clamp and the screw. By way of example, one end of the spacer 11 may be shaped into a concave spherical cap 11.1 to be in contact with the clamp and the second The end of this same spacer can be shaped into a convex spherical cap 11.2 to make contact with the collar or the nut. A person skilled in the art will be able to determine the height of the spacer and its position (between the collar 2 and the clamp 5 or between the clamp 5 and the nut 8). The presence of a spacer thus allows the height of the entire fastening assembly to be adjusted on the second threaded section of the screw, thereby enabling the rods to be positioned according to the patient's anatomy and the pathology being treated. In particular, when spinal stabilization is achieved by crossing the rods in the median sagittal plane, the spacers allow the height of the rods to be adjusted relative to each other without friction, or with controlled contact.

[0062] According to a second embodiment of the invention, the surgeon may need to stabilize more than two vertebrae, here three vertebrae Va, Vx, Vb as illustrated in Figures 7 to 10. In this situation, some of the stabilized vertebrae will be stabilized simultaneously by two rods 3ax, 3'xb, 3'ax, 3xb as illustrated in [Fig. 8]. It is therefore necessary to have a third fixation assembly comprising at least two clamps 10 that can be engaged on the second threaded section lx.2, l'x.2 of one of the screws and arranged to clamp one end of the second rod 3xb, 3'xb. Like clamp 5, clamp 10 comprises two jaws, a first jaw 5e strictly identical to the jaws 5c, 5d of clamp 5, and a jaw 9 having an inner surface 9.1 identical to the inner surface 5e. 1 of the first jaw and an outer surface 9.2 different from the outer surface 5 e.2 of the first jaw. Thus, as for the gripper 5, the first parts 5e.3 and 9.3 of each jaw 5e and 9 comprise a hollow 5.31, 9.31 and a projection 5.32, 9.32 of complementary shapes. Preferably, the hollow and the projection are hemisylindrical in shape with identical diameter and length and extend in line with each other across the width of jaw 5, 9. The first parts complement each other, the hollow 5.31 complementing the projection 9.32 and the projection 5.32 complementing the hollow 9.31 to form the hinge; the third parts 5e.5 and 9.5 are drilled in a cylindro-truncated conical manner to obtain a through-hole in the jaw 10 in the shape of a diabolo. As with the clamp 5, the second parts 5e.4 and 9.4 form a housing for one end of the rod 3xb, 3'xb. The outer surface 9.2 of the jaw 9 is shaped into a concave spherical cap, complementary to the outer surface 5d.2 of the second jaw 5d of the first clamp 5.According to this arrangement, the screw Ix includes, bearing against the collar 2x, a first clamp 5 comprising two jaws 5c, 5d. The outer surface 5c.2 of the first jaw 5c bears against the collar 2x, the outer surface 5d.2 of the second jaw 5d is in contact with the outer surface 9.2 of the first jaw 9 of the second clamp 10. The outer surface 5e.2 of the second jaw 5e of the second clamp 10 is then in contact with the inner surface 8x.l of the nut 8x.

[0063] When the surgeon has to fit three vertebrae, he will be able to implant the device according to the invention comprising the fixation assembly F with a single clamp 5 in the vertebrae which only accommodate one rod 3, here vertebrae Va, Vb and the device according to the invention comprising the fixation assembly F' with two clamps 5, 10 in the vertebra or vertebrae which accommodate two rods, here Vx.

[0064] The device according to the invention thus allows the surgeon to stabilize as many vertebrae as the patient's condition requires, to finely adjust the orientation and position of the rods thanks to the ball joint between the clamp and the screw, all with an ease and speed of setup linked to the small number of different elements: a screw, two different jaws, one with an outer surface shaped as a convex spherical cap, and the other with an outer surface shaped as a convex spherical cap, capable of being combined to form a clamp with two convex outer surfaces or with one convex outer surface and the other concave outer surface, a nut, and optionally a spacer.

[0065] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0066] In particular, a person skilled in the art can adapt the device according to the invention depending on the number of vertebrae to be fitted and the number of rods required to stabilize each vertebra, whether the stabilization is crossed or parallel to the median sagittal plane, or whether it includes both types of stabilization (crossed and parallel). A person skilled in the art can thus use one clamp 5 and two clamps 10 engaged one after the other on the second screw section if the vertebra requires stabilization with three rods, each additional rod being held by an additional clamp 10.

[0067] Here, the rod 3 has a circular cross-section, but it could have a different cross-section, for example prismatic or ovoid. Those skilled in the art will then be able to adapt the recessed surface of the second connecting part of the clamp to the cross-section of the rod so that the latter is perfectly held by the clamp.

[0068] The jaws are configured so as to be joined together. It is thus possible to make a clamp with two jaws 9, the two outer surfaces of which are concave.

[0069] Clip 6 can be removed once nut 8 is tightened, the clip only serving to hold the jaws temporarily for assembly.

Claims

Claims

1. Vertebral stabilization device, comprising: - at least two screws (1a, 1b) each having a first threaded section (1.1a, 1.1b) for being engaged in a vertebra (Va, Vb) and a second threaded section (1.2a, 1.2b) separated from the first threaded section by a collar (2); - at least one first connecting rod (3) having two opposite ends for connecting the second threaded sections of the screws to each other; and - at least a first fixing assembly (F) and a second fixing assembly (F') for fixing the ends of the rod (3) to the screws (1a, 1b), each fixing assembly comprising at least one clamp (5), engageable on the second threaded section (1.2a, 1.2b) of one of the screws (1, 2) and arranged to tighten one end of the first rod (3), and a nut (8) which has a lower bearing surface and which is arranged to be screwed onto the second threaded section (1.2a, 1.2b) by clamping the clamp (5) against an upper surface of the collar (2a, 2b) of the screw (la, 1b), said at least one clamp (5) comprising a first jaw (5c) and a second jaw (5d) identical to each other and held together by an elastic holding member (6), the first jaw comprising an inner surface (5c. 1) facing an inner surface (5d. 1) of the second jaw (5d), the inner surface comprising, at a first connecting part (5.3) of each jaw, a hollow (5.31) and a projection (5.32) of complementary shapes, the first connecting parts (5c. 3, 5d. 3) being engaged one in the other to form a hinge.

2. A spinal stabilization device according to claim 1, wherein the first part of each jaw comprises two semi-cylindrical surfaces of the same diameter and length extending in line with each other across the width of the jaw, the first cylindrical surface forming the projection (5.32), the second cylindrical surface forming the hollow (5.31).

3. A vertebral stabilization device according to claim 1 or 2, wherein each jaw comprises, opposite the first part (5.3), a second connecting part (5.4) to the rod (3), which comprises a hollow receiving surface (5.41) which is arranged to receive a portion of the rod (3) and which has a depth less than a radius of the stem.

4. A spinal stabilization device according to claim 3, wherein the recessed receiving surface (5.41) of the second part (5.4) has an axis parallel to an articulation axis of the hinge formed by the first part (5.3).

5. Vertebral stabilization device according to claims 1 to 4, in which each jaw (5c, 5d) comprises, next to the first part (5.3), a third part (5.5) for connection to the screw (1), comprises a cylindro-truncated conical bore (5.51) opening right through, the cylindro-truncated conical bore having a larger diameter adjacent to an outer surface (5c.2, 5d.2) of the jaw (5c; 5d) opposite the inner surface (5c.1, 5d.l), and a smaller diameter adjacent to the inner surface (5c.1, 5d.l).

6. A vertebral stabilization device according to any one of claims 1 to 5, wherein the third part (5c.5, 5d.5) of each jaw (5c, 5d) comprises a convex outer surface (5c.2, 5d.2) shaped as a spherical cap complementary to that of the upper surface of the collar (2) or the nut (8).

7. A vertebral stabilization device according to any one of claims 1 to 6, comprising at least one second connecting rod (3') and a third fixing assembly comprising at least one clamp (10), engageable on the second threaded section (la”.2, 1 ”b.2) of one of the screws (la”, 1b”) and arranged to tighten one end of the second rod (3'), the clamp comprising a first jaw (5e) and a third jaw (9) having an internal surface (9.1) identical to the internal surface (5e.1) of the first jaw 5e and an external surface (9.2) of concave spherical cap shape complementary to an external surface (5c.2, 5d.2) of a second jaw (5c, 5d).

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