Prosthesis for vertebral body replacement

Abstract

The present invention concerns a prosthesis (1) for vertebral body replacement. According to the invention, the prosthesis (1) comprises an upper module (2), a lower module (3) and a central module (4) mutually assembleable, and, in an assembled configuration of said prosthesis (1), said upper module (2) comprises a substantially flat upper surface (20), configured to contact with the vertebral structure (700) of the patient, a lower surface (21) in contact with said central module (4), and a lateral surface (22) comprising a hole (100), said lower module (3) comprises an upper surface (30) in contact with said central module (4), a substantially flat lower surface (31), configured to contact with the vertebral structure (700) of the patient, and a lateral surface (32) comprising a hole (101), and said central module (4) comprises an upper surface (41) in contact with said lower surface (21) of said upper module (2), a lower surface (40) in contact with said upper surface (30) of said lower module (3), and a lateral surface (42) comprising two through holes (102, 103) through two projecting parts (43, 44) of said lateral surface (42) and protruding to said upper module (2) and said lower module (3), respectively, wherein said lower surface (21) of said upper module (2) is inclined with respect to said upper surface (20), and said upper surface (30) of said lower module (3) is inclined with respect to said lower surface (31), and said central module (4) has said upper (41) and lower (40) surface not parallel and complementary to the surfaces (21) and (30), respectively, so as to allow a shape coupling between said central module (4) and said upper module (2) and said lower module (3), thus aligning said through holes (102, 103) to said hole (100), of said upper module (3), and to said hole (101), of said lower module (4), respectively, configured to be fixed with a screw, making said central module (4) solidly coupled to both said upper module (2) and to said lower module (3).

Description

[0001] PROSTHESIS FOR VERTEBRAL BODY REPLACEMENT

[0002] FIELD OF THE INVENTION

[0003] The present invention concerns a prosthesis for vertebral body replacement, in particular such prosthesis is implanted in the patient during thoracic corpectomy operations.

[0004] BACKGROUND

[0005] As is known, the corpectomy surgical procedure initially involves the step of removal or excision of the damaged vertebrae and / or intervertebral discs, followed by the placement of a prosthesis adapted to replace the damaged vertebral body, also known as “Vertebral Body Replacement” , to allow the subsequent reconstruction of the part of the spine affected by the damage, restoring its functionality, stability and alignment.

[0006] Generally, the main reasons that lead to a corpectomy, or vertebrectomy intervention being prescribed, for decompression and / or reconstruction of the spine are:

[0007] - the treatment of various spinal pathologies and instabilities due to vertebral fractures, such as vertebral compression fractures and / or fractures related to malignancy or infections; the causes of vertebral fractures may include falls, sports injuries and motor vehicle accidents;

[0008] - skeletal system tumours that affect the spine; in particular, when treating cancer patients, in the event that the cancer metastasizes, or spreads in the spine, the surgeon may choose to remove the affected vertebral bodies;

[0009] - osteomyelitis and degenerative disorders; diseases that therefore require a reconstruction of the affected vertebral parts to obtain decompression of the spinal cord and / or neural tissues.

[0010] Initially, the vertebral reconstruction step, typical of the corpectomy procedure, involved the use of grafts, such as autografts, allografts and / or bone substitutes. However, this surgery often led to complications such as, for example, high rates of pseudoarthrosis and delayed bone consolidation.

[0011] Medical research has then made the use of prostheses made of different materials being preferred, with significant improvements in both clinical and radiographic results. The various materials used for prostheses include, for example, acrylic resin and polymethylmethacrylate (PMMA), ceramics, metals, such as tantalum or carbon, for porous implants, and, nowadays, titanium or non-metallic materials, such as carbon or polyetheretherketone (PEEK), for expandable cage implants, which offer considerable advantages in radiological follow-up, producing fewer artifacts.

[0012] In particular, such expandable cages for corpectomy procedures, currently available on the market, provide for filling the metal body with bone grafting material.

[0013] In these cases, the surgery proceeds, after the aforementioned filling, with positioning the metal cage in the position previously occupied by the vertebral body and / or the damaged intervertebral discs.

[0014] Subsequently, screws are positioned, through plates, in the adjacent healthy vertebrae, and fixed, with appropriate metal bars, to the cage to provide additional support and stability during bone growth in the predefined position. At this point the incision can be closed to complete the surgery.

[0015] This cage therefore has the function of supporting the spine during the progressive growth of the new bone, in and around the cage, which will eventually fuse with the vertebrae below and above the site.

[0016] In general, the expandable cages have a single modular structure, formed by a cylindrical-shaped main module, which can be telescopically elongated or shortened by means of a threaded shaft and a nut, locking screws, positioned around the adjustment nut, which allow easy locking of the telescopic movement of the structure, and serrated end plates, to prevent movement of the cage after implantation.

[0017] Such cage implants for corpectomy operations of known type are not free of drawbacks among which it must be counted the fact that the expandable cages could have displacements, or even failures, of the end plates due to the strong loads to which the entire spine is subjected, thus compromising the entire graft.

[0018] In particular, displacements or failures usually occur on the internal surfaces of the end plates not resting on rigid contact surfaces, but only kept under pressure thanks to the telescopic elongation and / or shortening system of the threaded shaft of the main body and / or even by tips positioned on the external surface.

[0019] Another drawback of such expandable cage implants of known type consists in the fact that the different available configurations of end plates, despite having widely modulable geometric characteristics of the contact area, such as for example diameter, angles, shape, etc., do not lead to objective advantages in the correct bone fusion, but must always be weighed up in relation to the risk factors of the individual patient, thus lengthening and complicating the phases of diagnosis and preparation for surgery.

[0020] A further drawback of such expandable cage implants of known type consists in the fact that the type of introduction of bone graft is relevant for the purposes of success of the treatment. In particular, if the bone graft is positioned within the cage prior to expansion, the amount and compression that favours fusion of the grafted bone could be insufficient, while a bone graft after cage expansion could alter the pressure on the bone graft, leading to a non-perfect bone fusion. The graft must therefore be evaluated in relation to the risk factors of the individual patient, further lengthening and complicating the phases of diagnosis and preparation for surgery.

[0021] Another drawback of such expandable cage implants of known type consists in the additional encumbrance of the prosthesis given by its anchoring system, through screws and plates, and fixation, through the metal bars, to the adjacent healthy vertebrae, thus leading to the need to widen the surgical access route, increasing postoperative discomfort for the patient.

[0022] SUMMARY OF THE INVENTION

[0023] In light of the above, the task of the present invention is to make a prosthesis for vertebral body replacement that overcomes the limits of the prior art allowing to improve the stability of the implant in the face of the pressure to which the entire spine is subjected.

[0024] Within the scope of this task, it is an object of the present invention to make a prosthesis for vertebral body replacement having an improved contact surface with adjacent healthy vertebrae, so as to improve the subsequent bone fusion.

[0025] Another object of the present invention is to overcome the need for prior insertion of the bone graft material, leading to a more reliable system of bone growth in the implant, and subsequent fusion.

[0026] A further object of the invention consists in making a prosthesis having a smaller encumbrance, so as to restrict the surgical access route, and therefore the postoperative discomfort of the patient.

[0027] A further object of the invention consists in making a prosthesis which is capable of giving the greatest assurances of reliability and safety in use.

[0028] A still further object of the invention consists in making a prosthesis that is easy to make and economically competitive if compared to the prior art.

[0029] The aforementioned task as well as the aforementioned objects and others which will become more apparent hereinafter, are achieved by a prosthesis for vertebral body replacement as recited in claim 1.

[0030] Other features are provided in the dependent claims.

[0031] LIST OF FIGURES

[0032] Further characteristics and advantages will become more apparent from the exemplary but non-limiting description of a preferred embodiment of the present invention, illustrated with the aid of the accompanying drawings in which:

[0033] - figure 1 is a perspective view of a prosthesis for vertebral body replacement according to the invention in an assembled configuration;

[0034] - figure 2 is a perspective view of the prosthesis, according to the invention, in disassembled configuration;

[0035] - figure 3 is a front view of the prosthesis, according to the invention, in disassembled configuration;

[0036] - figure 4 is a side view of the prosthesis, according to the invention, in disassembled configuration;

[0037] - figure 5 is a side view of the prosthesis according to the invention in an assembled configuration;

[0038] - figure 6 is a side view of the prosthesis, according to the invention, in the first step of insertion between two vertebrae of the patient;

[0039] - figure 7 is a side view of the prosthesis, according to the invention, in the second step of insertion between two vertebrae of the patient;

[0040] - figure 8 is a side view of the prosthesis, according to the invention, in the third step of insertion between two vertebrae of the patient;

[0041] - figure 9 is a side view of the prosthesis, according to the invention, in the fourth step of insertion between two vertebrae of the patient;

[0042] - figure 10 is a side view of the prosthesis, according to the invention, inserted between two vertebrae of the patient.

[0043] DETAILED DESCRIPTION OF THE INVENTION

[0044] With particular reference to the attached figures, the prosthesis for vertebral body replacement, globally indicated with reference numeral 1, comprises an upper module 2, called “top”, a lower module 3, called “bottom” , and a central module 4, called “wedge”, where the module closest to the patient's skull is indicated as upper module 2, while the module closest to the patient's coccyx, according to the human body longitudinal axis, is indicated as lower module 4.

[0045] The invention provides for an assembled configuration in which the central module 4 is inserted between the upper module 2 and the lower module 3, as visible in figures 1 and 5, and a disassembled configuration in which the central module 4 is not totally inserted between the upper module 2 and the lower module 3, as visible in figures 2, 3 and 4.

[0046] In an assembled configuration of the prosthesis 1, the upper module 2, substantially cylindrical in shape, comprises a substantially flat upper surface 20, configured to contact with the vertebral structure of the patient, a lower surface 21, which in the assembled configuration is in contact with the central module 4, and a lateral surface 22 comprising a hole 100; the lower module 3, substantially cylindrical in shape, in turn comprises an upper surface 30, which in the assembled configuration is in contact with the central module 4, a flat lower surface 31, configured to contact with the vertebral structure of the patient, and a lateral surface 32 comprising a hole 101; the central module 4, substantially cylindrical in shape, comprising an upper surface 41, which in the assembled configuration is in contact with the lower surface 21 of the upper module 2, a lower surface 40, which in the assembled configuration is in contact with the upper surface 30 of the lower module 3, and a lateral surface 42 comprising two through holes 102, 103 through two projecting parts 43, 44 of the lateral surface 42 and protruding to the upper module 2 and the lower module 3, respectively.

[0047] Furthermore, with particular reference to Figure 4, the lower surface 21 of the upper module 2 is inclined with respect to the upper surface 20, the upper surface 30 of the lower module 3 is inclined with respect to the lower surface 31, and the central module 4 has the upper surface 41 and the lower surface 40 not parallel to each other and inclined in a complementary manner with respect to the surfaces 21 and 30, respectively, so as to allow a shape coupling between the central module 4 and the upper module 2 and the lower module 3.

[0048] Advantageously, said central module has, on a longitudinal vertical plane (i.e. sagittal thinking about the intended use of the prosthesis 1), a wedge-shaped profile.

[0049] Preferably, the lower surface 21 of the upper module 2 comprises at least one portion 21’ inclined with respect to the upper surface 20 of the upper module 2 and at least one portion 21” substantially flat and substantially parallel to said upper surface 20.

[0050] Preferably, the upper surface 30 of the lower module 3 comprises at least one portion 30’ inclined with respect to the lower surface 31 of the upper lower module 3 and at least one portion 30” substantially flat and substantially parallel to said lower surface 31.

[0051] Preferably, at least a portion 21’ of the lower surface 21 of the upper module 2 has an inclination with respect to the upper surface 20 of a value of between 1° and 8°, preferably between 4° and 6°, more preferably substantially equal to 5°.

[0052] Similarly, at least a portion of the upper surface 30 of the lower module 3 has an inclination with respect to the lower surface 31 of a value of between 1° and 8°, preferably between 4° and 6°, more preferably substantially equal to 5°.

[0053] More preferably, the inclination value of the portion 21’ of the lower surface 21 with respect to the upper surface 20 of the upper module 2 and the inclination value of the portion 30’ of the upper surface 30 with respect to the lower surface 31 of the lower module 3 are substantially the same.

[0054] In the assembled configuration, the through holes 102, 103 are aligned with the hole 100, of the upper module 3, and with the hole 101, of the lower module 4, respectively, said holes being suitable for receiving a screw for fixing said modules, making the central module 4 solidly coupled with the upper module 2 and the lower module 3.

[0055] In this way, the prosthesis 1 is assembled by first making the central module 4 slip between the upper module 2 and the lower module 3.

[0056] In particular, as illustrated in figure 6, the first step of insertion of the prosthesis 1 between two vertebrae 700 of the patient provides for the introduction of only the upper 2 and lower 3 modules in contact with each other. In this way, the initial surgical access route is smaller than the surgical incisions for the grafting of vertebral prostheses of known art.

[0057] The insertion of the upper module 2 and of the lower module 3 of the prosthesis 1 between two vertebrae 700 of the patient takes place by means of vertebral prosthesis introduction devices, not illustrated in the figures. These devices comprise a pressure handle, operable by the surgeon, connected to a lever mechanism to allow the distancing or approach, along a longitudinal vertical plane, of appropriate connection ends of the device with the spinal prosthesis 1.

[0058] During the first step of insertion of the prosthesis 1 between two vertebrae 700 of the patient, the connecting ends of each vertebral prosthesis introduction device are stably coupled with the upper module 2 and the lower module 3 of the prosthesis 1 through, respectively, the holes 221, 321 and 322, 222 present on the lateral surface 22 of the upper module 2 and on the lateral surface 33 of the lower module 3.

[0059] The presence of at least one substantially flat portion 21” of the upper module 2 substantially parallel to said upper surface 20 of said upper module 2, and of at least one substantially flat portion 30” of the lower module 3 substantially parallel to said lower surface 31 of said lower module 3, which are therefore parallel one 21’ to the other 30” and configured to contact with each other during the installation of the prosthesis, allows not only to have a flat rest surface in the step of insertion of the upper module 2 and of the lower module 3 between the patient's vertebrae 700 through the vertebral prosthesis insertion devices, but also to avoid the presence of pointed external surfaces of the prosthesis 1, which could cause cuts or lacerations on the patient's tissues in the surgical insertion area.

[0060] Preferably, the holes 222 and 322 are threaded blind holes, while the holes 221 and 321 are interlocking cylindrical blind holes. The presence of an interlocking coupling provided by the holes 221 and 321 prevents possible rotations of the upper module 2 and of the lower module 3 of the prosthesis 1 with respect to the vertebral prosthesis introduction device itself.

[0061] During the second step of insertion of the prosthesis 1 between two vertebrae 700 of the patient, as illustrated in figure 7, the upper module 2 and the lower module 3 of the prosthesis 1 are spaced apart, along a longitudinal vertical plane, by means of the vertebral prosthesis insertion devices.

[0062] During the third step of insertion of the prosthesis 1 between two vertebrae 700 of the patient, as illustrated in figure 8, the central module 4 of the prosthesis 1 is inserted into the surgical area.

[0063] During the fourth step of insertion of the prosthesis 1 between two vertebrae 700 of the patient, as illustrated in figure 9, the central body 4 is inserted by slipping it between the upper module 2 and the lower module 3. In this way, the extension between the upper module 2 and the lower module 3 increases, leading to an increase in the pressure exerted by the vertebrae 700 on the prosthesis 1, and therefore, actually, to an increase in the locking of the prosthesis 1 between the two vertebrae 700.

[0064] The insertion of the prosthesis 1 between two vertebrae 700 of the patient ends with the central module 4 being interlocked between the upper module 2 and the lower module 3, as illustrated in figure 10, so as to achieve the alignment of the through holes 102, 103 to the hole 100, of the upper module 3, and to the hole 101, of the lower module 4, respectively, and to make the central module 4 solidly coupled and fixed with the upper module 2 and the lower module 3 through a screw housable in said holes, and the subsequent decoupling of the vertebral prosthesis introduction device from the prosthesis 1, as well as the removal of said device from the surgical area.

[0065] In particular, when the central module 4 reaches the final position and is positioned between the upper module 2 and the lower module 3 with the projecting parts 43, 44 of the lateral surface 42 in contact respectively with the upper module 2 and the lower module 3, the interlocking and fixing take place both thanks to the pressure exerted by the vertebrae 700 of the patient on the prosthesis 1, specifically on the upper surface 20 of the upper module 2 and on the surface 31 of the lower module 3, and thanks to the presence of the screws through the through holes 102, 103, of the central module 4, and housed in the holes 100 and 101, of the upper module 2 and of the lower module 3, respectively.

[0066] Furthermore, the upper module 2 and the lower module 3 can be made with different height measurements and the surfaces 21 and 30 with different inclinations to obtain the desired lordosis of the prosthesis 1. These characteristics allow the prosthesis 1 to be easily adapted to the needs of the patient.

[0067] Preferably, the hole 100 of the upper module 2 is obtained in a recess 22’, while the hole 101 of said lower module 3 is obtained in a recess 32’, where the recesses 22’, 32’ have a shape complementary to the projecting parts 43, 44 of the central module 4, respectively, to enable a shape coupling.

[0068] Even more preferably, the projecting parts 43, 44 present a substantially cylindrical shape.

[0069] Preferably, the upper module 2, the lower module 3 and the central module 4 are made of titanium alloys of titanium or other biocompatible materials suitable for implantation in the human body.

[0070] In this way, the lower surface 21 of the upper module 2, the upper surface 31 of the lower module 3 and the surfaces of the upper 41 and lower 40 module of the central module 4 all have an equal rigidity, thus favouring the sliding of the central module 4, between the upper module 2 and the lower module 3, and obviating the risk of possible relative displacements and / or failures between the modules 2, 3 and 4, since the same modules 2, 3 and 4 are held in contact by the pressure of the vertebral structure of the patient and by the screws of the prosthesis 1, without any suspension or empty space between the relative contact surfaces.

[0071] Even more preferably, the upper surface 20 of the upper module 2 and the lower surface 31 of the lower module 3 comprise a trabecular structure 20’, 31’, respectively, made of titanium or similar alloys, also called “net trabecular” .

[0072] This structure favours osteo-induction processes, thus avoiding the need to insert bone graft material into the prosthesis, as well as additional anchoring and fixing systems to the patient's bone structure, such as screws and metal bars.

[0073] The prosthesis 1 according to the present invention thus provides an innovative solution for the stabilization of the spine in that the assembly of the three modules can take place directly at the implantation site allowing the surgeon to use a reduced access route compared to those used in similar cases.

[0074] The prosthesis for vertebral body replacement according to the present invention is susceptible to numerous modifications and variants all falling within the scope of the inventive concept as defined by the appended claims.

[0075] Furthermore, all the details can be replaced by other technically equivalent elements.

[0076] In practice, any materials can be used according to requirements, as long as they are compatible with the specific use, the dimensions and the contingent shapes.

Claims

CLAIMS1. Modular prosthesis (1) for vertebral body replacement comprising an upper module (2), a lower module (3) and a central module (4) mutually assembleable in an assembled configuration of said prosthesis (1), said upper module (2) comprising a substantially flat upper surface (20), configured to contact with the vertebral structure (700) of the patient, a lower surface (21) configured to contact, in an assembled configuration, with said central module (4), said lower module (3) comprising in turn an upper surface (30) which, in said assembled configuration, is in contact with said central module (4), and a substantially flat lower surface (31), configured to contact said vertebral structure (700) of the patient, wherein said central module (4) comprises an upper surface (41) configured to contact, in said assembled configuration, said lower surface (21) of said upper module (2), and a lower surface (40) configured to contact, in said assembled configuration, said upper surface (30) of said lower module (3), wherein said lower surface (21) of said upper module (2) is inclined with respect to said upper surface (20) of said upper module (2), and said upper surface (30) of said lower module (3) is inclined with respect to said lower surface (31) of said lower module (3), and wherein said central module (4) has said upper surface (41) and lower surface (40) not parallel to each other and complementary to said lower surface (21) of said upper module (2) and upper surface (30) of said lower module (3), respectively, so as to allow a shape coupling between said central module (4) and said upper (2) and lower (3) modules, wherein said lower surface (21) of said upper module (2) comprises at least one portion (21’) inclined with respect to said upper surface (20) of said upper module (2) and at least one portion (21”) substantially flat and parallel to said upper surface (20) of said upper module (2), and wherein said upper surface (30) of said lower module (3) comprises at least one portion (30’) inclined with respect to said lower surface (31) of said lower module (3) and at least one portion (30”) substantially flat and parallel to said lower surface (31) of said lower module (3).

2. Modular prosthesis (1) according to claim 1, wherein said central module (4) has a wedge-shaped profile on a longitudinal vertical plane, in particular sagittal thinking about the intended use of said modular prosthesis (1).

3. Modular prosthesis (1) according to claim 1 or 2, wherein said portion (21’) has an inclination with respect to said upper surface (20) of said upper module (2) of a value of between 1° and 8°, preferably between 4° and 6°, more preferably substantially equal to 5°.

4. Modular prosthesis (1) according to one or more of the preceding claims, wherein said portion (30’) has an inclination with respect to said lower surface (31) of said lower module(3) of a value of between 1° and 8°, preferably between 4° and 6°, more preferably substantially equal to 5°.

5. Modular prosthesis (1) according to claims 3 and 4, wherein said value of inclination of said portion (21’) of said lower surface (21) with respect to said upper surface (20) of said upper module (2) and said value of inclination of said portion (30’) of said upper surface (30) with respect to said lower surface (31) of said lower module (3) are substantially the same.

6. Modular prosthesis (1), according to one or more of the preceding claims, characterized in that said upper module (2) further comprises a lateral surface (22) in turn comprising a hole (100), said lower module (3) further comprises a lateral surface (32) comprising in turn a hole (101), and said central module (4) comprises a lateral surface (42) in turn comprising two through holes (102, 103) through two projecting parts (43, 44) of said lateral surface (42) and protruding to said upper module (2) and said lower module (3) respectively in said assembled configuration of said modular prosthesis (1), said modules (2, 3, 4) of said modular prosthesis (1) being stably connectable to each other by means of screws by aligning said through holes (102, 103) of said central module (2) to said hole (100) of said upper module (3) and to said hole (101) of said lower module (4), respectively, making said central module (4) solidly coupled to said upper module (2) and said lower module (3).

7. Modular prosthesis (1), according to claim 2, characterized in that said hole (100) of said upper module (2) is obtained in a recess (22’) of said lateral surface (22) of said upper module (2), said hole (101) of said lower module (3) is obtained in a recess (32’) of said lateral surface (32) of said lower module (3), where said recesses (22’, 32’) have a shape complementary to said projecting parts (43, 44) of said central module (4), respectively, to enable a shape coupling.

8. Modular prosthesis (1), according to one or more of the preceding claims, wherein said projecting parts (43, 44) present a substantially cylindrical shape.

9. Modular prosthesis (1), according to one or more of the preceding claims, wherein said upper module (2), said lower module (3) and said central module (4) are made of titanic material, or similar alloys.

10. Modular prosthesis (1), according to one or more of the preceding claims, wherein said upper surface (20) of said upper module (2) and said lower surface (31) of said lower module (3) comprise a trabecular structure (20’, 31’) made of titanium, or similar alloys.

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