WO2024126942A1

WO2024126942A1 - Lockable polyaxial screw

Info

Publication number: WO2024126942A1
Application number: PCT/FR2023/051987
Authority: WO
Inventors: Cedric-Yves-Robert-Pascal BARREY; Mourad Ben Mokhtar
Original assignee: Spineway
Priority date: 2022-12-12
Filing date: 2023-12-12
Publication date: 2024-06-20
Also published as: FR3142880A1

Abstract

The invention relates to a pre-assembled pedicle screw (1) comprising: - a screw (10) with a spherical head (11), - a socket (20) receiving the spherical head (11) in the manner of a ball-and-socket joint and having a location (21) for receiving a connection rod (50) connecting a plurality of pedicle screws (1), - a nut (30) intended to be screwed into the socket (20) in order to block the rod, - a ring (40) housed in the socket (20) and configured to bear against the spherical head (11), and having an impression (41) intended to receive a tool for manipulating the ring (40) between a position for releasing the spherical head (11) and a position for blocking the spherical head (11). According to the invention, the ring (40) is arranged between the spherical head (11) and the location (21) of the rod (50) within the socket (20).

Description

Title of the invention: Lockable polyaxial screw

Technical area

[0001] The invention relates to the technical field of pedicle screws used in thoracolumbar surgery, and more particularly concerns a pre-assembled polyaxial screw, that is to say in which it is the screw which is inserted from above into a socket, unlike a top-loading polyaxial screw in which it is the socket which snaps onto the head of the screw.

Prior art

[0002] Generally speaking, a spinal implant comprises at least two pedicle screws intended to be screwed onto a variable anatomical element of the vertebra (blade, pedicle, vertebral body), and a connection system (plate or rod) uniting the two pedicle screws between them. It is perfectly known to use a threaded nut adapted to screw into the pedicle screw and to hold a connecting rod in place.

[0003] These pedicle screws are most often polyaxial, that is to say they have a spherical head connected to a socket by a ball joint, and the socket receives the connecting rod. In this way, it is possible to properly orient the socket of the polyaxial screw in relation to the direction of the connecting rod, before fixing the assembly. Indeed, the axis of the screw is rarely orthogonal to the axis of the connecting rod, and a polyaxial screw makes it possible to overcome this drawback.

[0004] Certain screws of the prior art provide that the tightening of the nut blocks both the rod within the socket, and the orientation of the socket relative to the screw. These systems are mechanically simple because they include few parts.

However, setting up the whole thing is difficult, because all the elements are mobile relative to each other during installation, and it is difficult for the practitioner to properly orient the elements according to the planned therapy.

[0005] In order to be able to separately lock the orientation of the socket relative to the spherical head, and the rod within the socket, different systems have been proposed. [0006] Document EP3493755 describes a first system making it possible to separately lock the orientation of the sleeve and the locking of the rod. However, before blocking the rod with a nut, this system requires manually maintaining a pressing force on a lever in order to block the orientation of the socket, which is impractical.

[0007] Document WO2019/149483 describes another system making it possible to separately lock the orientation of the socket and the locking of the rod. However, this system has a large number of parts. In addition, the size of the head of the pedicle screw is increased, particularly in width.

[0008] Finally, each of these solutions requires assembling all the parts of the system (pedicle screws, connecting rods then nut) before being able to make the adjustments and locking of the system. This has the disadvantage that once the screws have been implanted, and when mounting the connecting rod, the orientation of the sockets is not at all controlled, which prevents the connecting rod from being easily mounted within the sockets. .

[0009] It is therefore possible to propose improvements compared to existing systems, in terms of practicality and simplicity.

[0010] Documents US2011/0152949 and WO2010/103198 are also known, the design of which can be further improved.

[0011] Documents US2021/0052305A1, US2016/0361096A1, US2020/0054376A1, US2018/0193063A1 are also known, which do not give complete satisfaction and which do not concern a preassembled polyaxial screw, but rather a top-loading polyaxial screw. .

Presentation of the invention

[0012] One of the aims of the invention is to overcome the drawbacks of the prior art, by proposing a preassembled pedicle screw which is simple in design and use, and takes up little space.

[0013] For this purpose, a pre-assembled pedicle screw has been developed comprising:

- a screw, or handle, with a spherical head,

- a socket receiving the spherical head according to a ball joint, and having a location for receiving a connecting rod between several pedicle screws,

- a nut intended to be screwed into the socket to lock the rod,

- a ring housed in the socket and configured to come to bear against the spherical head, and having a recess intended to receive a tool for manipulating the ring between a release position of the spherical head and a locking position of the spherical head, that is to say that the ring allows the orientation of the socket to be locked relative to the spherical head.

[0014] According to the invention, the ring is arranged between the spherical head and the location of the rod within the socket. That is to say that the rod rests on the ring, and the nut rests against the rod.

[0015] In this way, it is possible to manipulate the ring and bring it into its locking position of the spherical head, even before having placed the rod in the socket.

[0016] The orientation of the socket can therefore be carried out freely, while all the elements of the system are not yet present, which facilitates manipulation. Once the orientation of the socket is correct, it can be blocked so that subsequent insertion of the connecting rod is not difficult, nor does it change the orientation of the socket.

[0017] The ring being coaxial with the nut within the socket, the bulk of the pedicle screw is not increased.

[0018] According to a first embodiment, the ring is threaded, which allows a simple and inexpensive design.

[0019] In this mode, the ring and the nut preferably have the same thread, that is to say that their threads have the same profile, the same pitch, and the same nominal diameter. The manufacture of the socket is even easier.

[0020] In order to guarantee optimal locking of the entire pedicle screw by means of the nut, a first axial functional clearance between the ring and the spherical head is less than a second axial functional clearance between the ring and the socket . Thus, a tightening force transmitted from the nut to the ring, via the rod, is transmitted to the spherical head instead of being absorbed by the connection between the ring and the socket. By “axial”, we mean the measurement of the play along the axis of revolution of the sleeve. [0021] To avoid hindering access to the screw when the ring is pre-assembled in the socket before fitting the pedicle screw, the impression of the ring is through, the spherical head has an impression configured for its screwing by means of a tool, and the impression of the spherical head is of dimensions smaller than the inscribed circle of the impression of the ring. The term "inscribed" is used here in the geometric sense, that is to say that seen from above, the profile of the imprint of the spherical head is contained in the largest circle tangent to the profile of the imprint of the ring. The tool used to tighten the screw can therefore pass through the ring, and it is not necessary to remove the ring from the socket to tighten the screw.

[0022] In order to guarantee the blocking of the orientation of the sleeve, the ring has a spherical support zone intended to come into contact with the spherical head, and the support zone has an elastic portion.

Preferably, the elastic portion is defined by at least one cutout, for example longitudinal, on the periphery of the support zone. This embodiment makes it possible to simply give the desired elasticity to the ring, without changing its material which is preferably rigid.

[0024] So that the ring cannot be removed from the socket, in order to avoid its accidental loss, the ring has first snap-fastening means inside the socket.

Preferably, the first latching means are at least one ramp, for example placed between two cutouts, and intended to latch into a bore of the socket. This embodiment is simple to manufacture and implement.

[0026] To guarantee that the tightening of the ring is maintained throughout the duration of installation of the connection ramp and before the firm and definitive tightening of the nut, the ring has immobilization means within the socket .

[0027] So that the immobilization of the ring is complete, the immobilization means comprise second latching means cooperating with a part of the socket.

[0028] To avoid increasing the bulk of the pedicle screw, the second latching means are formed on the threads of the ring. [0029] For the same purpose, the ring has first latching means inside the socket, and the immobilization means comprise the first latching means.

Brief description of the drawings

[0030] [Fig.1] is a perspective view, seen from above, of a pedicle screw according to the invention.

[0031] [Fig.2] is a sectional view of a first embodiment of such a screw.

[0032] [Fig.3] is a sectional view of a second embodiment of such a screw.

[0033] [Fig.4] is a perspective view of a first version of a ring fitted to a pedicle screw according to the second embodiment.

[0034] [Fig.5] is a top view of such a pedicle screw.

[0035] [Fig.6] is a front view of a second version of a ring for a pedicle screw.

[0036] [Fig.7] is a diagram of such a ring mounted in a socket of such a screw.

[0037] [Fig.8] is a perspective view of a third version of the ring.

[0038] [Fig.9] is a perspective section of a screw receiving such a ring.

[0039] [Fig.10] is a perspective view of a fourth version of the ring.

[0040] [Fig.11] is a partial perspective section of a screw receiving such a ring.

Detailed description of the invention

[0041] With reference to Figures 1 to 3, the invention relates to a preassembled pedicle screw (1) comprising a screw (10) with a spherical head (11), and a socket (20) mounted in ball joint connection on the spherical head ( 11). The ball joint between the socket (20) and the spherical head (11) can be blocked according to the desired orientation, by means of a ring (40) placed in the socket (20), configured to come into tight support against the spherical head (11).

[0042] Grip means (22) of the sleeve (20) allow it to be immobilized when handling the ring (40). [0043] It is then possible to mount a connecting rod (50) between several pedicle screws (1), at a receiving location (21) of the socket (20), which generally has a U shape. The connecting rod (50) is held within the socket (20), orthogonal to the axis of revolution of the socket (20), by a tightening nut (30) mounted in the socket (20). ).

[0044] In this way, the practitioner can:

- place the pedicle screws (1) on the affected vertebrae of the patient,

- properly orient the socket (20) of each screw (1), and lock the orientation by means of the ring (40) of each pedicle screw (1),

- and finally mount the connecting rod (50) connecting the pedicle screws (1), before proceeding to fix the rod (50) using the nuts (30).

[0045] Thus, when installing the rod (50), the bushings (20) are held in position and the installation of the rod (50) is facilitated.

[0046] In practice, the ring (40) has a bearing surface (42) of complementary shape to the spherical head (11), and a recess (41) intended to receive a tool for manipulating the locking of the ring ( 40) between a release position of the spherical head (11) and a blocking position resting against the spherical head (11), by a helical connection type kinematics. Preferably, the imprint (41) is hollow. It is understood that the tool is not part of the pedicle screw (1) because it is not implanted, and does not remain after the surgical procedure.

[0047] In a first preferred embodiment illustrated in Figure 2, locking is obtained by a thread of the ring (40) cooperating with a thread of the socket (20). In a second embodiment illustrated in Figure 3, locking is obtained by a cam profile (47) of the ring (40) cooperating with a complementary profile of the socket (20).

The tool manipulating the ring (40) is introduced inside the socket (20) along its axis of revolution, which makes it possible to avoid increasing the size of the pedicle screw (1).

[0049] The operation of the first and second embodiment, of the helical connection type, is similar: the rotation of the ring (40) in a first direction implies its descent within the socket (20), contrary to of the spherical head (11). The functional play of the ball joint is eliminated by tightening the ring (40) against the head (11), thus blocking the orientation of the sleeve (20) relative to the head (11). The advantage of the first mode is that the ring (40) and the nut (30) can have the same thread, the manufacture of the socket (20) is therefore facilitated by the production of a single tapping, over the entire height necessary.

Preferably, the blocking is reversible, the rotation of the ring (40) in a second direction implying its rise within the socket (20), therefore the release of the socket (20). This reversibility allows the surgeon to properly orient the socket (20), if necessary, by trial and error.

[0051] The ring (40) is manipulated using a tool inserted in a recess (41) of the ring (40).

[0052] In the two embodiments provided, a first axial functional clearance j1) between the ring (40) and the spherical head (11) is less than a second axial functional clearance (j2) between the ring (40) and the socket (20).

[0053] In practice, the first functional clearance (j1) is measured on a radius of the ball joint, as illustrated in Figures 2 and 3, but it is indeed the vertical component of the first clearance (j1) which must be less than the second clearance (j2), which is measured along the vertical axis. By convention, the vertical axis is defined by the axis of revolution of the socket (20).

[0054] When tightening, the nut (30) presses on the rod (50), which in turn presses on the ring (40). Since the second functional clearance (j2) is greater than the first functional clearance (j1), the movement of the ring (40) along the vertical axis is not hindered by the sleeve (20), and the ring (40) can transmit the tightening force of the nut (30) to the spherical head (11).

[0055] This has several advantages. First of all, in the unlikely event that the surgeon forgot to block the orientation of the sleeve (20) by means of the ring (40), then the tightening of the nut (30) is indeed suitable to block the entire pedicle screw (1), as in the solutions of the prior art.

[0056] Then, it is possible to use the ring (40) only for pre-locking the head (11), by means of a limited tightening force, whereas a greater tightening force and guaranteeing the locking of the assembly is provided by the nut (30). This makes it possible to reduce the height of the recess (41) of the ring (40), and therefore the height of the ring (40), because the dimensioning of the recess (41) with a moderate clamping force requires a smaller surface area.

The size of the pedicle screw (1) can thus be optimized.

[0057] So that a bearing surface (42) of the ring (40) can perfectly match the geometry of the spherical head (11), the ring (40) present at the level of the bearing zone (42) an elastic portion (43), whose elasticity is greater than the rest of the ring (40). By elasticity, we mean that its diameter can vary in response to a force exerted on said portion.

[0058] With reference to Figure 4, this elasticity is preferably conferred by cutouts, for example longitudinal (44) distributed around the periphery of the support zone (42). This solution is particularly suitable for rings (40) made of metallic materials.

[0059] To facilitate operations during surgery, the pedicle screw (1) is preferably delivered with the ring (40) preassembled in the socket (20). The support zone (42) of the ring being able, thanks to its complementary shape to that of the spherical head (11), to participate in the definition of the ball joint connection, the pre-assembly of the ring (40) is preferably in a configuration close to blocking the head lock (11).

[0060] That is to say that in the case of a threaded ring (40), it is not left more than one thread from its locking position, and is on the contrary screwed at most near the head (11), while leaving the orientation of the socket (20) free relative to the head (11). Otherwise, in the event that the surgeon forgets to block the ring (40) before mounting the rod (50), the second set (j2) risks not being able to fulfill its role.

[0061] In order to avoid accidental loss of the ring (40), it preferably has first latching means (45) against the socket (20).

[0062] We see in Figure 4 an embodiment in which these first latching means (45) are two diametrically opposed ramps, arranged on the elastic portion (43) of the ring (40), between two cutouts (44 ). These ramps are configured to snap into a bore (23) provided for this purpose in the socket (20). The direction of engagement of the means (45) is parallel to the axis of revolution of the sleeve (40).

[0063] So that the prior assembly of the ring (40) does not hinder access to the recess (12) of the screw (10), with a view to its manipulation by a tool, the ring (40) has a impression (42) which is through, and of dimensions greater than those of the impression (12) of the screw (10), and in particular of dimensions greater than the inscribed circle of the impression (12).

[0064] With reference to Figure 5, we see that the inscribed circle (C4) of the imprint (42) of the ring (40) is of greater diameter than the circumscribed circle (C1) of the imprint (12) of the screw (10). In this way, the tool used to manipulate the screw (10) can pass through the ring (40) and the manipulation of the spherical head is easy.

[0065] The impressions are preferably of the hexagonal or hexalobular type (in the shape of a six-pointed star), which allow efficient transmission of the torque from the tool to the ring (40) and to the nut (30).

[0066] Figures 6 and 7 illustrate an embodiment in which the first latching means (45) comprise several ramps arranged on the elastic portions (43) of the ring (40), between two cutouts (44). Each ramp (45) is configured to snap into the bore (23) of the socket (20), in a snapping direction parallel to the axis of revolution of the socket (40).

However, the ramps (45) of the different elastic portions (43) are offset in height so as to define a helix of angle (p). In the mode shown:

- the ring (40) has ten elastic portions (43);

- the ramps (45) define a propeller with two threads;

- each net is made up of five ramps (45i to 45s).

[0068] In this way:

- when the ring (40) is assembled with the socket (20), the first two ramps

(451) are inserted into the bore (23) and guarantee the secure mounting of the ring (40), preventing its accidental loss;

- when in use, the ring (40) is tightened in order to lock the orientation of the socket (20), the ring (40) descends within the socket (20) and the second ramps

(452) will in turn be inserted into the bore (23), and so on. Of this In this way, the successive ramps (45) guarantee that the tightening of the ring (40) is maintained, because they prevent it from rising by unscrewing.

[0069] This embodiment of the ramps (45) constitutes a means of immobilization

(46) of the ring (40) within the socket (20).

[0070] In Figure 7, we see the last ramp (45s) inserted in the bore (23) and preventing untimely unscrewing of the ring (40).

[0071] This embodiment does not, however, prevent the possibility of adjusting the orientation of the sleeve (40) several times if necessary, because the force applied to the ring (40) by a tool is sufficient to bring out the ramps (45) of the bore (23).

[0072] In the mode illustrated, the upper face of the ramps (45) is inclined parallel to the angle helix (p). The contact between the ring (40) and the socket (20) is a point or an edge, depending on the depth of the ring (40). In an alternative mode not illustrated, the ramps (45) are offset in height to form the angle helix (p), but the upper faces are horizontal: the contact between the ring (40) and the socket (20) is a portion of the upper face of the ramps (45).

[0073] Figures 8 and 9 illustrate another embodiment of the immobilizing means (46) of the ring (40), which are pawls, advantageously arranged at one end of the cam profiles, or threads (47) of the ring (40).

[0074] When the ring (40) is tightened, the pawls (46) progress within the tapping of the socket (20), until it exits where they are released and come to cooperate with a stop (24), when the ring (40) is sufficiently tight.

[0075] Knowledge of:

- the value of the first axial functional clearance (j1), defining the tightening to be applied;

- the value of the pitch of the helical connection between the socket (20) and the ring (40); And

- the starting position of the threads of this connection; allows you to determine where to place the stop (24).

[0076] In this mode, the mobility of the pawl (46) is substantially parallel to the axis of revolution of the socket (40).

[0077] Machining (48) makes it possible to impart the necessary elasticity to the portion of the thread

(47) defining the pawl (46). [0078] Figures 10 and 11 illustrate another embodiment of the immobilization means (46) in which the mobility of the pawl (46) is substantially radial relative to the axis of revolution of the socket (40).

[0079] Analogous to the previous mode, the pawls (46) progress within the tapping of the socket (30) until they come to cooperate with a stop (24) of the socket (20).

[0080] This mode has the advantage of being able to use an insert such as a pin to make the stop (24): its positioning is easier compared to the previous mode, because it is sufficient to provide a radial drilling (25) through the socket (20) in the desired location.

[0081] In these last two embodiments, the pawls (46) are advantageously arranged at the end of the threads (47), so as not to increase the bulk of the screw (1).

[0082] In all cases, the immobilizing means (46) prevent untimely disassembly of the ring (40), but do not prevent intentional disassembly of the ring (40) using a tool exerting a force on the imprint (41).

[0083] The pawls (46) can be placed on the socket (20), and the stop (24) can be placed on the ring (40).

[0084] Furthermore, the pedicle screw (1) can be shaped differently from the examples given without departing from the scope of the invention, which is defined by the claims.

[0085] According to an embodiment not illustrated, the first means for latching the ring (40) are an attached element preventing its disassembly from the socket (20), such as a pin or an elastic ring, but not is however not preferred as this would increase the number of parts.

[0086] Furthermore, the technical characteristics of the different embodiments and variants mentioned above can be, in whole or for some of them, combined with each other. Thus, the pedicle screw (1) can be adapted in terms of cost, functionality and performance.

Claims

[Claims 1] Pre-assembled pedicle screw (1) comprising:

- a screw (10) with a spherical head (11),

- a socket (20) receiving the spherical head (11) according to a ball joint, and having a location for receiving (21) a connecting rod (50) between several pedicle screws (1),

- a nut (30) intended to be screwed into the socket (20) to lock the rod,

- a ring (40) housed in the socket (20) and configured to come to bear against the spherical head (11), and having a recess (41) intended to receive a tool for manipulating the ring (40) between a position of release of the spherical head (11) and a locking position of the spherical head (11), characterized in that the ring (40) is arranged between the spherical head (11) and the location (21) of the rod ( 50) within the socket (20).

[Claims 2] Pedicle screw (1) according to claim 1, characterized in that the ring (40) is threaded.

[Claims 3] Pedicle screw (1) according to claim 2, characterized in that the ring (40) and the nut (30) have the same thread.

[Claims 4] Pedicle screw (1) according to one of the preceding claims, characterized in that a first axial functional clearance (j1) between the ring (40) and the spherical head (11) is less than a second functional clearance axial (j2) between the ring (40) and the socket (20).

[Claims 5] Pedicle screw (1) according to one of the preceding claims, characterized in that the recess of the ring (40) is through, the spherical head (11) has a recess (12) configured for its screwing to the means of a tool, and the impression (12) of the spherical head (11) is of dimensions smaller than the inscribed circle of the impression (41) of the ring (40).

[Claims 6] Pedicle screw (1) according to one of the preceding claims, characterized in that the ring (40) has a spherical bearing zone (42) intended to come into contact with the spherical head (11), and the support zone (42) has an elastic portion (43).

[Claims 7] Pedicle screw (1) according to claim 6, characterized in that the elastic portion (43) is defined by at least one longitudinal cutout (44) on the periphery of the support zone (42).

[Claims 8] Pedicle screw (1) according to one of the preceding claims, characterized in that the ring (40) has first latching means (45) inside the socket (20).

[Claims 9] Pedicle screw (1) according to claims 7 and 8, characterized in that the first latching means (45) are at least one ramp intended to latch into a bore (23) of the socket (20). ).

[Claims 10] Pedicle screw (1) according to one of the preceding claims, characterized in that the ring (40) has immobilization means (46) within the socket (20).

[Claims 11] Pedicle screw (1) according to claim 10, characterized in that the immobilizing means (46) comprise second latching means cooperating with a part of the socket (20).

[Claims 12] Pedicle screw (1) according to claim 11 taken in combination with claim 2, characterized in that the second latching means are formed on threads (47) of the ring (20).

[Claims 13] Pedicle screw (1) according to one of claims 10 to 13, characterized in that the ring (40) has first latching means (45) inside the socket (20), and the immobilizing means (46) comprise the first latching means (45).