Surgical guide for placement of a pedicle screw in revision surgery and method for producing said surgical guide

Abstract

The invention discloses a surgical guide (1) comprising: a first body (11); a second body (12) having a guide orifice (121) for guiding the drill bit (B); and a bridge (13) connecting the first body (11) to the second body (12). The first and second surfaces (111, 131) are in contact respectively with a fixed pedicle screw (TF) and the first vertebra (V1). The first surface (111) is provided on the first body (11) and the second surface (131) is provided on either the second body (12) or the bridge (13). Furthermore, said first and second surfaces (111, 131) are obtained by means of additive manufacturing from medical images of the assembly of the first vertebra (V1), a second vertebra (V2) to which said preexisting fixed pedicle screw (TF) is fixed, and the preexisting fixed pedicle screw (TF) itself.

Description

[0001] SURGICAL GUIDE FOR PLACING A PEDICLE SCREW IN REVISION SURGERY AND PROCEDURE FOR MANUFACTURING SAID SURGICAL GUIDE

[0002] DESCRIPTION

[0003] OBJECT OF THE INVENTION

[0004] The present invention falls within the field of medicine, and more particularly in the field of spinal revision surgery.

[0005] A first object of the present invention is a surgical guide specially designed for spinal revision surgeries in which it is necessary to remove a misplaced pedicle screw and replace it with another.

[0006] A second object of the present invention is a method for manufacturing said surgical guide.

[0007] BACKGROUND OF THE INVENTION

[0008] The spine is made up of a series of vertebrae that are connected to each other in an articulated manner. As shown in Fig. 1 , a vertebra (V) essentially comprises a vertebral body (C) from which emerge a series of bony protuberances, such as a central spinous process (AE) and two lateral transverse processes (AT). The spinous process (AE) and the transverse processes (AT) are connected by a lamina (L), which, in turn, is attached to the body (C) by means of pedicles (P). Between the lamina (L) and the body (C) there is a cavity called the spinal canal (RC) through which the bone marrow passes.

[0009] Spinal arthrodesis is a well-known technique suitable for certain pathologies. It essentially consists of immobilizing at least two vertebrae by rigidly connecting them. Pedicle screws are commonly used for this purpose. As shown in Fig. 2, a pedicle screw (T) is a screw that is inserted into the vertebra in a specific direction, passing through the pedicle (P). Pedicle screws (T) have a head specially designed to allow the screws (T) to be connected to each other by means of a rod (VA) or similar, thus achieving the aforementioned immobilization. Fig. 3 schematically shows three pedicle screws (T) rigidly connected to each other by means of the rod (VA).

[0010] In this context, it is of utmost importance that pedicle screws be inserted into the vertebra through the pedicle following a specific, predetermined trajectory. Failure to do so can lead to problems such as nerve or vascular damage, infection, bone fractures, and fixation failure.

[0011] To ensure that pedicle screws are inserted along the desired trajectory, the use of guides specifically designed for each patient's anatomy is now common. These guides comprise support areas on the vertebra that are shaped to complement the anatomical surface of the vertebra on which they will rest. To this end, medical images of the patient's bone structures are acquired prior to surgery, and, using additive manufacturing, customized guides are manufactured that fit perfectly onto a surface of the patient's vertebra. This feature helps ensure the guide is placed very precisely in a specific position on the patient's vertebra.The guides also have a hole oriented in the desired trajectory through which the instrument (for example, a drill bit) is introduced to make the hole in the vertebra through which the screw will later be inserted, thus ensuring correct placement.

[0012] Occasionally, when no guide is used, or even despite its use, positioning errors can occur, resulting in a pedicle screw being misplaced. In these cases, a second surgical procedure is necessary, sometimes called "revision surgery," in which the misplaced screw is removed and replaced with another. During the operation, it is of utmost importance that the new screw properly follows the planned trajectory. This is particularly complicated given that there is already a hole in the vertebra that the new screw tends to follow during the insertion process.

[0013] Currently, there is no guidance device designed specifically for this purpose.

[0014] DESCRIPTION OF THE INVENTION

[0015] The inventors of the present invention have developed a surgical guide specifically designed for the placement of pedicle screws in revision surgeries.

[0016] Indeed, in addition to the pedicle screw to be replaced, revision surgeries typically involve at least one other preexisting pedicle screw inserted into the vertebra where the pedicle screw is to be replaced, or into an adjacent vertebra. The solution proposed in this application is a surgical guide with a surface configured to engage the head of said preexisting screw.

[0017] The main advantage of this new surgical guide is that the pre-existing screw provides a much firmer and more stable support than the natural anatomical surfaces of the vertebra where conventional guides rest. The first reason is that, unlike pre-existing pedicle screws, the anatomical surfaces are often covered by tissue, which negatively affects the stability of the support. A second reason is related to the fact that the shape of a pedicle screw head is specifically designed to allow for a firm, slip-free fit. Thanks to this, the proposed surgical guide does not require many additional support points, nor do it require support points with large surface areas. Typically, a small support point in addition to that provided by the pre-existing screw itself is sufficient.

[0018] First aspect: surgical guide

[0019] A first aspect of the present invention is directed to a surgical guide for placing a pedicle screw in revision surgery. The proposed guide is configured to guide a drill bit in the creation of a new hole in a first vertebra for a new pedicle screw. The surgical guide of the invention essentially comprises the following elements: a first body; a second body provided with a guide hole for the drill bit; and a bridge connecting the first body to the second body. These elements are normally formed as a single piece, although the possibility of incorporating elements formed separately and subsequently coupled together is not ruled out.

[0020] To this point, the features of the surgical guide of the invention are known in the prior art. However, the guide of the invention differs from those in that it comprises first and second surfaces configured to contact, respectively, a pre-existing fixed pedicle screw and the first vertebra. The first surface configured to engage a pre-existing fixed pedicle screw is comprised within the first body, while the second surface configured to engage an anatomical surface of the first vertebra is comprised within one of the second body and the bridge.

[0021] The first and second surfaces are obtained through additive manufacturing from medical images of the assembly consisting of the first vertebra, a second vertebra to which the pre-existing fixed pedicle screw is attached, the pre-existing fixed pedicle screw itself, and, if present, a rod connected to the pre-existing fixed pedicle screw and, possibly, to other pre-existing fixed pedicle screws. As is known, medical images can be obtained through various techniques, as well as combinations of them, the most important being Computed Tomography (CT) and Magnetic Resonance Imaging (MRI).

[0022] In a preferred embodiment of the invention, the first surface may comprise a first cavity portion configured to fit over a pre-existing fixed pedicle screw head. This first cavity portion will be the negative of the shape of the pre-existing pedicle screw head. The head of such a pedicle screw typically has a prismatic-shaped contour whose cross-section may be circular, square, rectangular, or the like. Thus, according to another particularly preferred embodiment, the first cavity portion may have a prismatic shape with a circular, square, or rectangular cross-section.

[0023] As previously mentioned herein, the pre-existing fixed pedicle screw to which the first surface of the surgical guide is attached may be attached to a rod that connects said pre-existing fixed pedicle screw to other pre-existing pedicle screws attached to other vertebrae to implement the arthrodesis. In view of this, in another preferred embodiment of the invention, the second surface of the surgical guide will comprise, in addition to the first cavity portion, a second cavity portion configured to fit over said rod connected to the pre-existing fixed pedicle screw. Since the rod is typically in the form of a straight bar, the second cavity portion preferably has the form of a straight slot.This second straight slot-shaped cavity portion will normally intersect with the first prism-shaped cavity portion, thus allowing a firm and stable coupling between the first body of the surgical guide and the assembly formed by the pre-existing pedicle screw and the aforementioned rod.

[0024] The bottom of the first and second cavity portions of the first surface may be flat, with the first body being fitted onto the pre-existing fixed pedicle screw and, where applicable, the rod, solely by contact with the side walls of said portions. Alternatively, in preferred embodiments of the invention, the bottom of said first and second cavity portions may also have the shape of the negative of the screw and, where applicable, the rod. That is, in that case, the bottom of the first cavity portion may have a central protuberance with a shape that fits into the hole in the screw head, for example, a hexagonal shape (to fit into an Allen key hole), a star shape (to fit into a Phillips screwdriver hole), a hexalobular shape (to fit into a Torx key hole), or others.For its part, the bottom of the second portion of the cavity, if it exists, will have a cylindrical angular section.

[0025] Furthermore, according to another preferred embodiment of the invention, the second surface may be located at the end of a leg protruding from the bridge. The specific position and configuration of this leg may vary depending on the particular geometric configuration of each application, although preferably the second surface located at its end will be configured to rest on the lamina of the first vertebra in a position adjacent to the area where the new hole is to be made. Since the new hole in the first vertebra is to be made at one end of the lamina where it rests on the pedicle, the leg preferably rests on an area of ​​the lamina near the base of the spinous process. In short, the second surface preferably has an anatomical shape corresponding to the negative of the portion of the lamina of the first vertebra adjacent to the area where the new hole is to be made.

[0026] In another preferred embodiment of the invention, an alternative to the previous ones, the second surface may be located at a base of the second body. In this case, the second surface will be configured to rest on the area of ​​the lamina of the first vertebra where the new hole is to be made. That is, unlike the previous case where the leg was already resting near the base of the spinous process of the first vertebra, that is, in a position separated from the new hole, in this case the second surface rests on an area surrounding the position where the new hole is to be made. Therefore, in a particularly preferred embodiment of the invention, the second surface has an anatomical shape corresponding to the negative of the portion of the lamina of the first vertebra where the hole is to be made. For example, the guide hole may be located in the center of the second surface located at the base of the second body.The second surface may be, for example, circular and encompass the entire base of the second body. The surgical guide of the invention could have additional surfaces configured to contact a vertebra, a pre-existing pedicle screw, or a connecting rod between existing pedicle screws. However, thanks to the firmness and stability provided by the support on the existing pedicle screw, only the two contact points mentioned in the preceding paragraphs are necessary. Therefore, in another particularly preferred embodiment of the present invention, the guide is configured to contact any of the first vertebra, the second vertebra, the pre-existing fixed pedicle screw itself, and the rod solely through the first and second surfaces, without additional contact points.More specifically, the guide of the invention preferably does not comprise any surface configured to contact the spinous process of the first vertebra. Avoiding contact with the spinous process is advantageous because the spinous process is typically surrounded by tissues that prevent firm and stable support.

[0027] The guide of the invention can be configured in two main alternative ways. According to a first configuration mode, the first surface of the guide is fixed to a pre-existing pedicle screw that is fixed to the same vertebra in which the new hole is to be made. Therefore, in this case, the first and second vertebrae are the same vertebra. The pre-existing pedicle screw will necessarily be located in a position on the vertebra approximately symmetrical to that where the new hole is to be made. Therefore, the bridge connecting the two bodies must somehow traverse from one side to the other of the spinous process of the vertebra. This can be achieved, for example, by designing the bridge with a hole or cavity designed to accommodate, without contact, the spinous process when the guide is fixed in its natural position. Alternatively, if necessary, it is possible to remove the spinous process to allow the guide to rest.

[0028] Alternatively, in a second configuration alternative to the previous one, the first surface of the guide is fixed to a pre-existing pedicle screw that is fixed to a different vertebra than the one in which the new hole is to be made. That is, the new hole is made in a first vertebra, but the pre-existing pedicle screw that supports the guide is in a second vertebra different from the first. Preferably, the first and second vertebrae are adjacent vertebrae. Normally, a pedicle screw located in an adjacent vertebra on the same side of the spinous process as the one in which the new hole is to be made will be used to support the first body. Therefore, in this case, there are no significant protrusions between the pre-existing screw that supports the first body and the position of the second body where the new hole is to be made.This implies that the bridge connecting both bodies does not require any special shape as in the previous case.

[0029] Second aspect: manufacturing process

[0030] A second aspect of the invention is directed to a method for manufacturing a surgical guide for placing a pedicle screw in revision surgery. Again, the surgical guide is configured to guide a drill bit in creating a hole in a first vertebra for a new pedicle screw. The method comprises the following steps:

[0031] 1. Acquire medical images of a set consisting of the first vertebra, a second vertebra to which a pre-existing fixed pedicle screw is attached, and the pre-existing fixed pedicle screw itself.

[0032] 2. Next, manufacture the surgical guide. The surgical guide comprises a first body, a second body provided with a drill guide hole, and a bridge connecting the first body to the second body. Said surgical guide further comprises first and second surfaces configured to contact a pre-existing fixed pedicle screw and the first vertebra, respectively. The first surface configured to engage a pre-existing fixed pedicle screw is comprised within the first body. The second surface configured to fit onto an anatomical surface of the first vertebra is comprised within one of the second body and the bridge. Furthermore, the first surface and the second surface are obtained by additive manufacturing from the medical images acquired in the previous step. Even more preferably, the entire surgical guide is obtained by additive manufacturing.

[0033] BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Fig. 1 shows a schematic view of a vertebra with the different anatomical parts that compose it.

[0035] Fig. 2 shows a schematic view of the position of two pedicle screws fixed to a vertebra.

[0036] Fig. 3 shows a schematic view of several pedicle screws anchored to several vertebrae and connected by a rod to secure the arthrodesis.

[0037] Fig. 4 shows a schematic perspective view of a surgical guide according to the present invention designed to be fixed to a pedicle screw anchored to the same vertebra where the new hole is to be made.

[0038] Fig. 5 shows another schematic perspective view of the surgical guide shown in Fig. 4.

[0039] Figs. 6a-6e show a sequence of schematic views of the process of replacing a defective pedicle screw using a surgical guide similar to that shown in Figs. 4 and 5.

[0040] Fig. 7 shows a schematic perspective view of a surgical guide according to the present invention designed to be fixed to a pedicle screw anchored to a vertebra adjacent to the one where the new hole is to be made.

[0041] PREFERRED EMBODIMENT OF THE INVENTION

[0042] Examples of surgical guides (1) according to the present invention are described below with reference to the accompanying figures. Note that the shapes shown in these figures have been simplified, and therefore do not necessarily correspond exactly to the actual shapes of an operative surgical guide.

[0043] Figs. 4 and 5 show simplified perspective views of a surgical guide (1) designed to rest on a pre-existing pedicle screw (T P ) which is fixed to the same vertebra (V^ where the new hole (A) is to be made N ). That is, according to the notation used in this document, the first vertebra and the second vertebra are the same, which will be simply called "vertebra (Vi)''. As can be seen, the surgical guide (1) has a first body (11), a second body (12), and a bridge (13) that connects the first body (11) with the second body (12). In this example, the surgical guide (1) is formed as a single piece obtained by additive manufacturing in the manner that will be described later. The first body (11) has, at its base facing the vertebra (XA), a first surface (111) that has a first portion of a prismatic cavity of the same cross section as the head (CT P) of the pre-existing pedicle screw (T P ) to which it is attached. As can be seen, the pedicle screws (T P ) preexisting have a head (CT P ) with a substantially rectangular cross-sectional outline with the two short sides rounded. Therefore, although not apparent in Figs. 4 and 5, the first cavity portion of the first surface (111) will be in the form of a rectangular prism with a substantially rectangular cross-section with the two short sides rounded.

[0044] In addition, the pedicle screw (T P ) preexisting to which the first body (11) of the surgical guide (1) is coupled is connected to a rod (VA) that joins it to two pedicle screws (T P) fixed to vertebrae adjacent to the vertebra (V^ in question. Therefore, the first surface (111) of the first body (11) of the surgical guide (1) of this example also comprises a second cavity portion that has the shape of an essentially straight slot (its outline can be seen in Fig. 5). This straight slot will intersect with the prism of rectangular section with short sides rounded perpendicular to the long sides and centered in relation to them. In this way, the assembly formed by the head of the pedicle screw (T P ) preexisting and a portion of the rod (VA) fixed to it fit perfectly into the first surface (111). Thus, when the body (11) of the surgical guide (1) is placed so that the first surface (111) fits over the assembly formed by the screw (T P ) plus the piece of rod (VA), the guide (1) as a whole is fixed in an exceptionally firm and stable manner.

[0045] Although not seen in the figures, the bottom of the first cavity portion may be configured to engage the upper face of the pedicle screw (T P ) pre-existing, that is, to the face of the head (CT P ) of the pedicle screw (T P ) preexisting opposite the vertebra (V^. In that case, the bottom of the first portion of the cavity would have a hexalobular shaped protuberance to fit into the corresponding cavity on the upper face of the head (CT P ) of the pedicle screw (T P ) preexisting. The same could occur with the bottom of the second portion of the cavity, although in this case the shape would be of a cylindrical angular section.

[0046] For their part, the second body (12) and the bridge (13) that connects the first body (11) with the second body (12) both have a schematic form in Figs. 4 and 5. Naturally, as is conventional, the second body (12) has a hole (121) that serves as a guide for a drill bit (B) when making the new hole (A N ). In any case, the most important feature is that, when the surgical guide (1) is fixed to the vertebra (VA), a leg (132) protrudes from the bridge (13) and contacts an area of ​​the lamina (L) that is close to the base of the spinous process (AE). This contact point is close to the place where the new hole (A) will be made N ). The second surface (131) of the end of the leg (132) that contacts the sheet (L) has an anatomical shape that corresponds to the negative of the shape of the sheet (L) at that point.

[0047] The shape of the first surface (111) in the first body (11) and the shape of the second surface (131) of the leg (132) are obtained from medical images of the assembly formed by the vertebra (VA), the pedicle screw (T P ) preexisting and the rod (VA) connected to said pedicle screw (T P ) pre-existing. These medical images can be obtained, for example, by MRI or CT. Subsequently, the surgical guide (1) is manufactured using additive manufacturing techniques in a manner customized for the patient in question, using the previously acquired images. The information from the images is used to design the shape of the first surface (111) and the second surface (131), as well as the dimensions of the different elements that make up the surgical guide (1). Normally, not only these surfaces (111, 131), but the entire surgical guide (1) will be manufactured by additive manufacturing.

[0048] Figs. 5a-5e show schematically how a revision surgery would be performed in which a defective pedicle screw is to be replaced (T D ) by a new pedicle screw (T N ).

[0049] First, as shown in Fig. 5a, the defective pedicle screw (T D ), thus leaving a defective hole (A) in the vertebra (VA D ) whose trajectory does not coincide with the desired trajectory. A pedicle screw (T) can also be seen in this figure P ) pre-existing that is fixed to the vertebra (VA on the opposite side of the same, that is, on the other side of the spinous process (AE).

[0050] Next, as shown in Fig. 5b, the surgical guide (1) is anchored to the pedicle screw (T P ) pre-existing fitting the head (CT P ) of said pedicle screw (T P) on the first surface (111) of the first body (11). At the same time, the second surface (131) arranged at the end of the leg (132) protruding from the bridge (13) rests on the area of ​​the sheet (L) located next to the position of the defective hole (A). D ), specifically in an area adjacent to the base of the spinous process (AE) of the vertebra (XA). The first and second surfaces (111, 131) are the only two support points of the surgical guide (1), and are sufficient to position it in relation to the vertebra (XA) in a sufficiently rigid and stable manner. In this position, the hole (121) of the second body (12) is positioned and oriented such that its axis (E 121 ) follows the desired path for the new hole (A N ). The figure shows how this axis (E 12 I) is misaligned relative to the axis (E A D) of the defective hole (A) D ).

[0051] In Fig. 5c, a drill bit (B) connected to a suitable apparatus is used to make the new hole (A N ). The drill bit (B) is passed through the hole (121) of the second body (12), thus ensuring that the new hole (A N ) follows exactly the desired path.

[0052] Fig. 5d shows the situation where the new hole (A N ) is finished and the drill bit (B) has been removed.

[0053] In Fig. 5e, the new hole (A) has already been used. N ) to introduce a new pedicle screw (T N ) following the desired path.

[0054] Finally, Fig. 6 shows another configuration where the surgical guide (1) is designed to rest on a pedicle screw (T P ) preexisting that is fixed to the same vertebra (V2) different from the vertebra (V^ where the new hole (A) is to be made N ). In addition, the pedicle screw (T P) preexisting is located on the same side of the spinous process (AE) as the new foramen (A N ) to be practiced. Again, the surgical guide (1) has a first body (11), a second body (12), and a bridge (13) that connects the first body (11) with the second body (12). These elements have essentially the same characteristics as those described in relation to the previous configuration except for some differences.

[0055] On the one hand, the bridge (13) does not need to have any special configuration to save the spinous process (AE), since the two support points are located on the same side of it and the plane that contains it is not crossed. On the other hand, in this configuration the bridge (13) is parallel to a rod (VA) that connects several pedicle screws (T P ) pre-existing, and has a lower cavity in the form of a slot into which said rod (VA) fits.

Claims

CLAIMS 1. Surgical guide (1) for placing a pedicle screw in revision surgeries, configured to guide a drill bit (B) in making a hole (A) N ) in a first vertebra (V^ for a new pedicle screw (T N ), comprising: a first body (11); a second body (12) provided with a guide hole (121) for the drill bit (B); and a bridge (13) connecting the first body (11) with the second body (12), characterized in that it comprises first and second surfaces (111, 131) configured to contact respectively with a fixed pedicle screw (T F ) preexisting and with the first vertebra (V^, where: the first surface (111) configured to engage a fixed pedicle screw (T F) preexisting is comprised in the first body (11); and the second surface (131) configured to fit on an anatomical surface of the first vertebra (V^ is comprised in one of the second body (12) and the bridge (13), where said first surface (111) and second surface (131) are obtained by additive manufacturing from medical images of the assembly formed by the first vertebra (V^, a second vertebra (V2) to which said fixed pedicle screw (T F ) preexisting, and the fixed pedicle screw itself (T F ) pre-existing.

2. Surgical guide (1) according to claim 1, wherein the first surface (111) comprises a first cavity portion configured to fit over a head (CT F ) of the fixed pedicle screw (T F ) pre-existing.

3. Surgical guide (1) according to claim 2, wherein the first cavity portion has a prismatic shape with a circular, square or rectangular section.

4. Surgical guide (1) according to any of claims 2-3, wherein the first surface (111) further comprises a second cavity portion configured to fit over a rod (VA) connected to the fixed pedicle screw (T F ) pre-existing.

5. Surgical guide (1) according to claim 4, wherein the second cavity portion has a straight slot shape.

6. Surgical guide (1) according to any of the preceding claims, wherein the second surface (131) is located at the end of a leg (132) that protrudes from the bridge (13).

7. Surgical guide (1) according to claim 6, wherein the second surface (131) is configured to rest on the lamina (L) of the first vertebra (VA) in a position adjacent to the area where the new hole (A) is to be made. N ).

8. Surgical guide (1) according to claim 7, wherein the second surface (131) has an anatomical shape corresponding to the negative of the lamina portion (L) of the first vertebra (VA) adjacent to the area where the new hole (A) is to be made. N ).

9. Surgical guide (1) according to any of claims 1-5, wherein the second surface (131) is located at a base of the second body (12) and is configured to rest on the area of the lamina (L) of the first vertebra (VA) where the hole (A) is to be made. N ).

10. Surgical guide (1) according to claim 9, wherein the second surface (131) has an anatomical shape corresponding to the negative of the lamina portion (L) of the first vertebra (VA) where the hole (A) is to be made. N ).

11. Surgical guide (1) according to any of the preceding claims, which is configured to contact any of the first vertebra (VA), the second vertebra (V2), the fixed pedicle screw (T) itself F ) pre-existing and the rod (VA) only through the first and second surfaces (111, 131).

12. Surgical guide (1) according to claim 11, which does not comprise any surface configured to be in contact with the spinous process (AE) of the first vertebra (VA.

13. Surgical guide (1) according to any of the preceding claims, wherein the first vertebra (VA) and the second vertebra (V2) are the same vertebra.

14. Surgical guide (1) according to any of claims 1-12, wherein the first vertebra (VA) and the second vertebra (V2) are adjacent vertebrae.

15. Surgical guide (1) according to any of the preceding claims, which is manufactured entirely by additive manufacturing.

16. Procedure for manufacturing a surgical guide (1) for placing a pedicle screw in revision surgeries, where the surgical guide (1) is configured to guide a drill bit (B) in the making of a hole (A N ) on a first vertebra (XA) for a new pedicle screw (T N ), characterized by comprising the following steps: - acquire medical images of a set consisting of the first vertebra (XA), a second vertebra (V2) to which a fixed pedicle screw (T) is attached F ) preexisting, and the fixed pedicle screw itself (T F) pre-existing; then, manufacturing the surgical guide (1), where the surgical guide (1) comprises a first body (11), a second body (12) provided with a guide hole (121) for the drill bit (B), and a bridge (13) that connects the first body (11) with the second body (12), said surgical guide (1) comprising first and second surfaces (111, 131) configured to contact respectively with a pre-existing fixed pedicle screw (TF) and with the first vertebra (X / 1), where the first surface (111) configured to couple to a pre-existing fixed pedicle screw (TF) is comprised in the first body (11) and the second surface (131) configured to fit on an anatomical surface of the first vertebra (X / 1) is comprised in one of the second body (12) and the bridge (13), where said first surface (111) and second surface (131) are obtained by additive manufacturing from the acquired medical images.

Images