Bone Fixation Devices

Abstract

The present invention relates to a fixation device suitable for engaging an appropriate bone site in the context of regenerative and / or reconstructive surgery, such as for example vertebral surgery or trauma surgery. The bone fixation device 1 comprises a constraining portion 3 engageable in use with a respective bone seat and extending along a longitudinal direction, a fixation body 2 including a tip engagement end EE, a distal end CE and a screw thread 7, and a head portion 4 connected to the fixation body 2 by the distal end CE. The constraining portion 3 comprises a core or body (5) defining a first cross-section (FS). The bone fixation device 1 also comprises a complementary or filling structure and / or volume (6) defining a second cross-section (SS).

Description

[Technical field]

[0001] The present invention relates to a fixation device that is particularly suitable for engaging an appropriate bone site in the context of, for example, regenerative and / or reconstructive surgery, such as, for example, vertebral surgery or trauma surgery. More particularly, the fixation device may include a bone and / or pedicle screw, optionally fabricated by three-dimensional or 3D printing methods, such as, for example, additive manufacturing. [Background technology]

[0002] As is known, the most commonly used fixation devices in the medical field are screws, which may be pedicle screws, often used in the treatment of vertebral surgery, or simple bone screws, which may be used in trauma surgery.

[0003] Typically, in the context of vertebral surgery, these fixation devices are used together with other metal elements, in particular plates or bars, for the stabilization of the spine. Stabilization here means the application of one or more elements or devices to keep two or more adjacent vertebrae strong and rigid. This procedure is necessary, for example, in the case of vertebral spondylosis, which may be deformed, traumatic or degenerative.

[0004] In this regard, the fixation device must be able to accommodate the different orientations that the bar or plate may adopt as it follows the spinal column in order to re-establish the correct three-dimensional alignment of the affected vertebrae.

[0005] Consider for example pedicle screws, which are used by utilizing the pedicle, which is a protruding end of a vertebra in the shape of a hollow cylinder covered on the outside by cortical tissue with spongy tissue inside, the size and orientation of which vary according to different segments of the spinal column, and therefore pedicle screws of different lengths are provided for stabilization of different segments.

[0006] Furthermore, to be able to insert the screw in the desired direction, it is necessary to have a "movable head". This mobility is obtained by assembling two physically separate components with a hemispherical joint: the screw, which is inserted into the pedicle, and the head, to which the bar or plate is locked.

[0007] Generally, in the daily postoperative period, the implanted fixation device must withstand the stresses generated by the body in a state of bone resorption. To improve the bone fixation capacity, the outer surface of the screw is sometimes coated with a thin layer of titanium and / or hydroxyapatite particles applied by plasma spraying technique, which increases the surface roughness and bone bonding capacity of the device. In the case of small device size, this layer has in any case a very limited thickness, and therefore the increase in roughness and primary fixation capacity is limited.

[0008] Thus, with fixation devices provided by the prior art, it is not uncommon to see the device loosen its grip, unscrew from its seat, or disintegrate the screw relative to its head due to strains (torsion and bending) transmitted from the fixation bar or plate, resulting in failure of the internal fixation.

[0009] It can therefore be seen that the mechanical strength, the robustness of the assembly of the two components, and the adhesion of the fixation device with the bone seat are important factors for a successful surgical procedure.

[0010] Often times, these fixation devices create significant challenges to bone integration, significantly complicating and delaying the patient's post-operative recovery period.

[0011] US Pat. No. 5,399,433, US Pat. No. 5,499,463, US Pat. No. 5,523,636, and US Pat. No. 5,523,663 describe respective solutions according to the state of the art.

[0012] In particular, Patent Document 1 discloses a spinal internal fixation screw comprising a screw cap member and a bone connection member connected to the screw cap member, the bone connection member comprising a solid portion and a porous fusion portion fixedly disposed on a surface of the solid portion.

[0013] On the other hand, US Patent No. 5,999,633 discloses a fixation implant including a head, a shank, and a distal tip, one or more of which can be cannulated. The shaft includes a bone thread portion extending from the head to a tapered distal tip, the bone thread portion including an external thread and at least one network body extending along the length of the bone thread portion.

[0014] US Pat. No. 5,399,633 discloses a locking screw that includes a body extending along a longitudinal axis and provided with a threaded surface.

[0015] It is therefore necessary to design and manufacture a fixation device making it possible to overcome the drawbacks listed in the prior art. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] European Patent Application Publication EP2796104(A1) [Patent Document 2] U.S. Patent Application Publication No. 2018325570(A1) [Patent Document 3] European Patent Application Publication EP3932363(A1) [Patent Document 4] U.S. Patent Application Publication No. 2015313658(A1) Summary of the Invention

[0017] [Objective of the Invention] The technical objective of the present invention is to improve the state of the art with regard to fixation devices, and more particularly with regard to fixation devices suitable for engaging specific bone seats in the context of regenerative and / or reconstructive surgery, such as for example spinal surgery or trauma surgery.

[0018] Within this objective, it is the object of the present invention to provide a fixation device which has high mechanical resistance to twisting and bending and at the same time allows the use of a larger volume of material useful for the adaptation or integration of bone tissue, thus allowing better bone integration compared to fixation devices of the same size manufactured according to the state of the art.

[0019] Another object of the present invention is to provide a fixation device having a cross-section that is optimized as a function of the mechanical strength and volume of the material used for bone tissue adaptation or integration.

[0020] Yet another object of the present invention is to provide a fixation device which can be manufactured in a simple and quick manner, e.g. by a single manufacturing step, in order to avoid complex assembly operations and the risk of disassembly during clinical use.

[0021] This aim and these objects are achieved by a fixing device according to claim 1.

[0022] The dependent claims point out preferred and advantageous embodiments of the invention.

[0023] Other characteristics and advantages of the invention will become more apparent from the following description of an embodiment of the fixation device, illustrated by way of example in the accompanying drawings, in which: FIG. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a perspective view of a fixation device according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a side view of the fixation device according to the embodiment shown in FIG. 1. [Diagram 3] FIG. 2 is an exploded view of the fixation device according to the embodiment shown in FIG. 1. [Figure 4] 2 is a cross-sectional view of a component (eg, core or body) of the fixation device according to the embodiment shown in FIG. 1. [Diagram 5] 2 is a cross-sectional view of another component (eg, a complementary or filling structure and / or volume) of the fixation device according to the embodiment shown in FIG. 1. [Figure 6] 2 is a cross-sectional view of the fixation device according to the embodiment shown in FIG. 1. [Figure 7] 13 is a cross-sectional view of a fixation device according to an alternative embodiment of the present invention. [Figure 8] 13 is a cross-sectional view of a fixation device according to an alternative embodiment of the present invention. [Figure 9] 13 is a cross-sectional view of a fixation device according to an alternative embodiment of the present invention. [Figure 10] FIG. 2 is a front view of the fixation device according to the embodiment shown in FIG. 1 obtained by a three-dimensional or 3D printing method. [Figure 11] FIG. 2 is a perspective view of a fixation device according to the embodiment shown in FIG. 1 obtained by a three-dimensional or 3D printing method. [Figure 12] FIG. 13 is a perspective view of a fixation device according to yet another embodiment of the present invention. [Figure 13] 13 is a cross-sectional view of a fixation device according to another embodiment of the present invention. [Figure 14] FIG. 2 is a perspective view of a further non-limiting embodiment of the present invention. [Figure 15] FIG. 15 is a cross-sectional view of the embodiment of FIG. 14 along plane AA. [Figure 16] FIG. 15 is a cross-sectional view of the embodiment of FIG. 14 along plane XX.

[0025] In the accompanying drawings, identical parts or components are designated by identical reference numerals. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] With reference to the accompanying drawings, the number 1 indicates generally a fixation device according to a non-limiting embodiment of the present invention. The fixation device 1 is particularly, but not exclusively, suitable for use in the medical field, in particular in the context of regenerative and / or reconstructive surgery, such as for example spinal surgery or trauma surgery.

[0027] In essence, the fixation device is particularly suitable for use as a bone fixation device. In this case, the fixation device 1 may advantageously be a pedicle screw (eg as shown in FIG. 1) or a bone or trauma screw (eg as shown in FIG. 12).

[0028] The fixation device 1 according to the invention comprises a fixation body 2, which constitutes, for example, a portion extending along a first direction or longitudinal direction of the fixation device 1 and which is engageable in use with a bone seat, and a head portion 4. In at least one version of the invention, the fixation body 2 is comprised of a restraining portion 3 (e.g., in a structure that allows for physical constraints), a tip engagement end EE and a distal end CE, the distal end CE connecting with a head portion 4. Thus, the head portion 4 is connected or connectable to the fixation body 2 by the distal end CE.

[0029] In particular, the constraining portion 3 includes a core or body 5 that defines a first cross-sectional area FS (eg, as shown in FIG. 4). In at least one version of the invention, the constraining portion 3 also preferably includes a complementary or filling structure and / or volume 6 that limits (defines) a second cross-sectional area SS (e.g., as shown in FIG. 5).

[0030] The cross section SS together with the first cross section FS defines an overall cross section MS of the constraining portion 3 (eg, as shown in FIG. 6). In other words, the overall cross section MS of the restraining portion 3 is defined by the assembly or joining of a first cross section FS of the core or body 5 constituting the resistance section of the restraining portion 3 and a second cross section SS of a complementary or filling structure and / or volume 6, if present.

[0031] According to a non-limiting embodiment of the invention shown in FIG. 1, the overall cross section MS of the constraining portion 3 is of circular configuration. The cross section of the fixation body 2 and / or the fixation device 1 has a structure that substantially corresponds to the overall cross section MS.

[0032] The fixation device 1 according to the invention provides that the complementary or filling structure and / or volume 6 comprises or consists of at least two parts 6a. Similarly, the core or body 5 comprises at least a central portion 5a and at least two protruding or convex portions 5b extending from the central portion 5a, for example towards the outside of the fixation device 1.

[0033] In at least one version, the central portion 5a is coaxial with the fixation body 2 and / or the restraining portion 3 and / or the fixation device 1. The projecting or convex portions 5b together with the central portion 5a define respective housing or receiving areas or spaces HA for the at least two portions 6a of the complementary or filling structures and / or volume 6.

[0034] Preferably, both the at least one central portion 5a and the at least two protruding or convex portions 5b extend along the longitudinal extension of the restraining portion 3, or more specifically along the longitudinal extension of the core or body 5, and should be considered to extend, for example, to a greater extent, with respect to one of their dimensions. Furthermore, the at least two protruding or convex portions 5b may both have a straight or curved or at least partially curved design, or alternatively, one protruding or convex portion 5b may have a curved or at least partially curved design and the other protruding or convex portion 5b may be straight.

[0035] Preferably, the core or body 5 is filled, ie not hollow, or in any case completely filled.

[0036] Furthermore, according to a non-limiting embodiment shown in FIG. 13, the core or body 5 can have a longitudinal through-hole TH, for example a circular longitudinal through-hole TH. Preferably, the longitudinal through-hole TH extends over the entire longitudinal extension of the fixation device 1 , if desired over the entire longitudinal extension of the restraining portion 3 or of the core or body 5 .

[0037] As can be appreciated, in this configuration the fixation device 1 can advantageously also be used as a cannulated screw.

[0038] According to other non-limiting examples of the invention, the longitudinal through-hole TH can extend only partially along the longitudinal extension of the fixation device 1, if desired the restraining portion 3 or the core or body 5, for example from the distal end CE towards the tip engaging end EE or vice versa, between 40% and 90%, for example for 65% thereof, of its longitudinal extension.

[0039] Furthermore, when a longitudinal through hole TH is provided as described above, it should be considered preferable to increase the volume of the core or body 5 relative to the volume of the complementary or filling structure and / or volume 6, if desired, in a proportion comprised, for example, between 10% and 30%, depending on the width of the longitudinal through hole TH, in order to eliminate or in any case reduce the reduction in the mechanical strength of the fixation device 1 caused by the presence of the longitudinal through hole TH.

[0040] By way of example and not limitation, with reference to the overall cross-section MS or cross-section FS of the restraining portion 3, each protruding or convex portion 5b has a substantially rectangular or square or trapezoidal or triangular or polygonal shape and / or cross-section (considered along a transverse or perpendicular plane to a first or longitudinal direction of such portion) and / or has some or all rounded edges, etc. Further non-limiting embodiments are shown in FIGS. 7-9 as well as FIG.

[0041] In particular, by way of example, each protruding or convex portion 5b may include a first segment 5c, a second segment 5d, and a connecting segment 5e for the first segment 5c and the second segment 5d. Each of the first segment 5c, the second segment 5d, and the connecting segment 5e may be a straight, curved, or at least partially curved segment.

[0042] In at least one version of the invention, the first segment 5c is substantially parallel to the second segment 5d and / or the third connecting segment 5e is perpendicular to the first segment 5c and / or the second segment 5d.

[0043] In at least one version of the invention, the first segment 5c and / or the second segment 5d have a larger size than the third connecting segment 5e. In yet a further version, the first segment 5c and the second segment 5d have substantially the same length.

[0044] In one version of the invention, as shown for example in FIG. 4, the core or body 5 has a cross-shaped cross section with four mutually perpendicular protruding or convex portions 5b. Preferably, at least a first segment 5c and / or at least a second segment 5d of at least one protruding or convex portion 5b, more preferably each first segment 5c and each second segment 5d of each protruding or convex portion 5b, has a connecting end 5f of the protruding or convex portion 5b having a central portion 5a of at least partially curved or in any case tapered design, e.g. so as not to form undesirable edges, points or undercuts.

[0045] Preferably, the fixation body 2, or more particularly the constraining portion 3, comprises at least one screw thread 7 to facilitate engagement or implantation of the fixation device 1 into the respective bone seat in use. In this connection, it should be noted that the protruding or convex portions 5b should be considered as parts emerging from the central portion 5a that are different and / or distinct from the thread 7 or, in any case, from the parts of the thread 7 itself, the thread 7 at least functionally constituting an element separated by the protruding or convex portions 5b. In other words, the at least two protruding or convex portions 5b are not defined by the thread 7 or any part thereof.

[0046] Advantageously, the at least one thread 7 extends concentrically along the longitudinal extension of the constraining portion 3, if desired with a variable pitch, for example gradually decreasing along the longitudinal extension of the constraining portion in the direction approaching the head portion 4, thus facilitating engagement of the fixation device 1 into the respective bone seat. For example, the thread 7 may comprise a helical or spiral coil structure that encases the constraining portion 3. Each coil is spatially separated along its length from further or subsequent coils. Thus, between one coil of the thread 7 and the other, there is a complementary or filling structure and / or volume 6 that is visible and / or that may come into contact, during use, with tissue of the bone site in which the fixation device 1 is implanted.

[0047] Furthermore, at least one, and preferably each, of the at least two protruding or convex portions 5b may advantageously comprise a support for at least one thread 7 or a connection end 5b1 with at least one thread 7. In at least one version of the invention, this support for the at least one thread 7 or the connection end 5b1 with the at least one thread 7 corresponds to a connection segment 5e.

[0048] Thus, in essence, the thread 7 is attached, supported or restrained by at least two protruding or convex portions 5b and / or the support or connecting end 5b1 and / or the connecting segment 5e of said at least two protruding or convex portions 5b.

[0049] In this regard, the housing or receiving area or space HA of the at least two complementary or filling portions 6a may be defined by at least one screw thread 7 in addition to the central portion 5a and the at least two protruding or convex portions 5b. In this case, the central portion 5a, the at least two protruding or convex portions 5b and the at least one screw thread 7 may define each or at least one housing or receiving area or space HA as a housing or receiving cage for the respective complementary or filling portion 6a.

[0050] When at least one screw thread 7 is supported by or connected to a support or connecting end 5b1 of at least one or each protruding or convex portion 5b, the mechanical stresses caused by the coupling of the fixation device 1 can be released to at least one or each protruding or convex portion 5b, thereby obtaining considerable rigidity and resistance. Advantageously, at least one thread 7 can be made integral with, and if necessary even of the same material as, the core or body 5 and / or said complementary or filling structure and / or volume 6 by a method described in more detail below.

[0051] According to a non-limiting example of the invention, each complementary or filling portion 6a (four in FIG. 5) has a cross-section having a sector shape, for example a sector shape equal to a quarter of a circle. This section thus completes, together with section FS of core or body 5, the overall cross-section MS of constraining portion 3. Thus, as can be seen in the example of FIG. 6, the overall cross-section MS of constraining portion 3 is generally circular.

[0052] As can be seen from Figures 7 to 9, any structure can be provided, and the cross-section of each portion 6a of the complementary or filling volume 6 can correspond to a sector defining an angle greater than or less than 90°, in other words greater than or less than a quarter of a circle, or a rectangle, or an "L", or an "S", or an irregular shape, as shown in Figure 7. In particular, in this version, the at least two protruding or convex portions 5b are arranged such that the first cross-section FS is in the shape of two L's. The core or body 5 is structurally more resistant to mechanical stresses for reasons that will be explained in more detail below.

[0053] Returning to the structure of the constraining portion 3, it is generally preferred that the surface bulk (surface volume) of the first cross section FS and the second cross section SS relative to the overall cross section MS is designed and manufactured in such a way that it is selected by optimizing the mechanical strength of the fixation device 1, which varies with the configuration and with the surface occupied by the core or body 5, and the bone bonding capacity of the fixation device 1, which varies with the surface occupied by the complementary or filling structure and / or volume 6. It should be noted that although in the previous paragraph reference was made to a surface bulk because of reference to a cross section, the bulk can also be explicitly defined in volumetric terms, since both the core or body 5 and the complementary or filling structure and / or volume 6 preferably extend along the longitudinal extension of the constraining portion 3, thus defining a three-dimensional or volumetric bulk.

[0054] The mechanical strength of the fixation device 1 can be considered and evaluated as its resistance to twisting and bending when subjected to a given test load. In particular, considering a given configuration of the core or body 5 , the mechanical resistance is proportional to the volume of this core or body 5 .

[0055] Similarly, the bone bonding ability of the fixation device 1, which may be considered and evaluated as its ability to integrate into a complementary or filling structure and / or volume 6 with potential bone tissue of the engaged bone site during use, is also directly proportional to the porosity of the complementary or filling volume 6.

[0056] Advantageously, the fixation device 1 optimizes the volume occupied by the core or body 5, the complementary or filling volume 6 and its porosity so as to obtain the best compromise between the mechanical strength and the bone-integrating capacity of the fixation device 1. Preferably, the complementary or filling structures and / or volumes 6 have a porosity between 40% and 80%. Preferably, the second cross section SS has a surface bulk equal to 25% to 65%, for example 35% or 45%, relative to the surface of the entire cross section MS, or similarly, the volume of the complementary or filling structure and / or volume 6 is equal to 25% to 65%, for example 35% or 45%, of the volume of the constraining portion 3.

[0057] According to a further non-limiting embodiment of the invention shown in FIG. 14, the ratio between the surface bulk of the first cross section FS and the surface bulk of the second cross section SS is variable along the longitudinal development of the restraining portion 3. In connection with this embodiment, the first cross-section FS can advantageously have a surface bulk at the distal end CE that, for example, gradually decreases toward the tip engaging end EE, thus allowing an increase in the proportion of the second cross-section SS to the overall cross-section MS.

[0058] In other words, the thickness of the core or body 5 may advantageously be variable along the longitudinal development of the constraining portion 3 . More specifically, the thickness of the core or body 5 at the distal end CE preferably decreases, eg, gradually, towards the tip engaging end EE.

[0059] In this regard, by way of example, reference is made to the cross-sections shown in Figures 15 and 16, which show that the surface bulk of the core or body 5 is greater in cross-section AA proximal to the distal end CE than the surface bulk of such core or body 5 in cross-section XX proximal to the tip engaging end EE.

[0060] In this regard, according to at least one version of the invention, it has been found that during installation of the fixation device 1, it is preferable to have a greater mechanical strength at the distal end CE of the fixation body 2, since this constitutes the most mechanically stressed point or area. These mechanical stresses then decrease towards the tip engaging end EE. Thus, at the distal end CE, a greater surface bulk of the first cross section FS defined by the core or body 5 can be advantageously provided, which can decrease in proportion towards the tip engaging end EE in favor of an increase of the second cross section SS limited by the complementary or filling structure and / or volume 6, and thus of an increase in bone integration.

[0061] From a manufacturing standpoint, the core or body 5 may be made from a metallic material such as titanium, a titanium alloy, steel, stainless steel if desired, or a biocompatible polymeric material if desired. Similarly, the complementary or filling structures and / or volumes 6 can also be made of a metallic material, such as titanium, a titanium alloy, a magnesium alloy, a tantalum alloy, stainless steel, or a polymeric material, such as polylactic acid, or a ceramic material, such as hydroxyapatite or brushite.

[0062] Obviously, different realization combinations can also be provided between the core or body 5 and the complementary or filling structures and / or volumes 6, for example between a core or body 5 made of titanium and a complementary or filling volume 6 made of hydroxyapatite. Alternatively, different materials can be provided for each complementary or filling portion 6a of the complementary or filling structure and / or volume 6, for example a complementary or filling portion 6a of hydroxyapatite and another complementary or filling portion 6a of titanium.

[0063] Referring to the non-limiting example of the overall cross section MS of the constraining portion 3 shown in FIG. 7, the core or body 5 comprises two protruding or convex portions 5b rising from a central portion 5a, e.g. from the ends of said central portion 5a, e.g. perpendicularly or at an angle to the direction of the central portion 5a. In this version, both the central portion 5a and each projecting or convex portion 5b have a cross-section (considered along a transverse or perpendicular plane to the longitudinal or first dimension of those cross-sections) that is substantially rectangular or square or trapezoidal or triangular or polygonal, and / or has rounded edges, etc.

[0064] Preferably, the core or body 5 comprises three or five protruding or convex portions 5b rising from a central portion 5a and arranged such that the first cross section FS is shaped like a sunburst or star having three or five points, for example as shown in Figures 8 and 9 respectively.

[0065] The configuration of the core or body 5 with four protruding or convex portions 5b arranged as a cross makes it possible to obtain the best compromise and best optimization between the volume or cross-sectional area occupied by the core or body 5 and the volume or cross-sectional area occupied by the complementary or filling structures and / or volumes 6, and therefore between the mechanical strength and the bone-integrating capacity of the fixation device 1.

[0066] As a non-limiting example, a tensile strength or R equal to about 860 MPa may be used, which may include four lobes or convex portions 5b arranged as a cross, a generally circular cross section MS having a diameter of about 10 mm, and m , and a yield strength or R equal to about 790 MPa. po.2 Considering the configuration of the core or body 5 including a construction material having a torsional load of about 12 Nm, the application of a torsional load equal to about 12 Nm produces a maximum critical value equal to about 147 MPa, and therefore the above-mentioned R m and R Po.2 is well below the limit. It should therefore be taken into account that the configuration just described is very robust against mechanical stresses, but at the same time it makes it possible to use a considerable volume for the complementary or filling structures and / or volumes 6, thus obtaining in fact a large bone integration capacity of the fixation device 1.

[0067] On the other hand, as can be seen, a configuration of the core or body 5 with two or three protruding or convex portions 5b benefits more the bone-integrating ability of the fixation device 1, but reduces its mechanical strength, because the proportion of the volume occupied by the complementary or filling structures and / or volumes 6 is greater than the volume that would be occupied in a constraining part 3 with a core or body 5 of the same configuration, but including four protruding or convex portions 5b arranged in a cross or star shape, where the thickness or volume of the protruding or convex portions 5b is considered to be the same for both configurations.

[0068] Conversely, a configuration of the core or body 5 having more than four protruding or convex portions 5b benefits the mechanical strength of the fixation device 1 more, but reduces its bone-integrating ability, because the proportion of the volume occupied by the complementary or filling structures and / or volumes 6 is smaller than the volume that would be occupied in a constraining part 3 of the same configuration, but with a core or body 5 including four protruding or convex portions 5b arranged in a cross or star shape, where the thickness or volume of the protruding or convex portions 5b is considered to be the same for both configurations.

[0069] It should be noted that in the case of a configuration of the core or body 5 comprising protruding or convex portions 5b arranged such that the first cross section FS is cross- or star-shaped, these protruding or convex portions 5b may also be curved or at least partially curved.

[0070] As regards the complementary or filling structures and / or volumes 6, more particularly the at least two complementary or filling portions 6a, they are advantageously configured based on a first cross section FS of the core or body 5. In other words, the at least two complementary or filling portions 6a can be configured to fill a respective housing or containing area or space HA defined by the at least one central portion 5a, the at least two protruding or convex portions 5b and, if present, the at least one screw thread 7.

[0071] According to a non-limiting embodiment of the invention shown in Figures 10 and 11, the complementary or filling structure 6 comprises a porous and / or trabecular structure and / or pores or cavities. This trabecular structure is defined by a plurality of trabeculae, i.e. a plurality of fine lamellar units, which communicate with each other if desired and are arranged, for example irregularly or regularly, and which limit (define) respective cavities designed to allow integration therein of the bone tissue present in the insertion seat of the fixation device 1.

[0072] Advantageously, the complementary or filling structures and / or volumes 6 may be made integrally with the core or body 5 by methods that will be described in more detail below. Alternatively, according to another non-limiting embodiment of the invention, after realization of the core or body 5, a complementary or filling structure and / or volume 6, or more specifically at least two complementary or filling portions 6a, can be inserted, for example by injection or positioning, into the respective housing or containing area or space HA.

[0073] From a structural point of view, the fixation device 1 and / or fixation body 2 may be provided with a distal engagement end EE, shaped like a tip if desired, configured to engage with a respective bone seat, as envisaged above. The tip engaging end EE is on the opposite side to the head portion 4 .

[0074] In at least one version of the invention, the tip engaging end EE has a substantially conical or frustum of a cone or pyramid or truncated pyramid or prism or diamond shape, and / or has grooves or ridges or the like.

[0075] Preferably, the distal engaging end EE at least partially comprises a porous structure or surface designed to facilitate, in use, the adaptation or integration of the fixation device 1 with bone tissue. Possibly, this porosity can be constituted by a regular or irregular cellular structure and / or a cellular structure comprising pores or cavities. Alternatively, the tip engaging end EE may be complete and / or solid, or in either case non-porous.

[0076] According to a non-limiting embodiment of the present invention shown in FIGS. 10 and 11, the tip engaging end EE is made integral with the core or body 5 .

[0077] Further, from a structural point of view, the fixation device 1 and / or the fixation body 2 may comprise an end CE distal from the tip engagement end EE for connection with the head portion 4 . As regards the head portion 4, it may advantageously be made integral with the fixation body 2 and / or the distal end CE. Distal end CE, in at least one version of the invention, has a substantially conical or frustoconical or pyramidal or frustopyramidal or disk-like or flat shape (eg, as shown in FIG. 12), or the like.

[0078] According to a non-limiting embodiment of the invention shown in FIG. 1, the head portion 4 is substantially spherical or hemispherical. According to other non-limiting embodiments of the invention, the head portion 4 can also have other configurations, for example pyramidal, prismatic, disc-shaped, cylindrical, or more generally irregular shapes.

[0079] Advantageously, the head portion 4 can define, at its own distal end relative to the restraining portion 3, a suitable engagement seat 12 (e.g. shown in FIG. 12 ) intended to enable coupling or tightening of the fixation device 1 by means of a suitable tool, such as a screwdriver.

[0080] If desired, the fixation device 1, or more specifically the fixation body 2, may comprise a connection component 8 which is operably associated or associable with the head portion 4 in use and which is designed to enable further devices to be connected to said fixation device 1 by suitable connection means.

[0081] In this regard, according to a non-limiting embodiment of the invention shown in Fig. 1, the head portion 4 is operatively associated in a rotational manner with the connection component 8 via a ball joint connection, in which case the head portion advantageously has a spherical or hemispherical construction and the fixation device 1 consists of a pedicle screw. In this regard, the substantially spherical or hemispherical head portion 4 is housed in a suitable housing seat HS defined in the connecting component 8 .

[0082] Alternatively, the connection component 8 may include a substantially spherical or hemispherically configured portion to be accommodated in a suitable housing seat defined in the head portion 4, the head portion 4 having any shape to form a coupling ball joint. This coupling is particularly advantageous in that it allows both tilting and rotation of the connection component 8 relative to the longitudinal axis of the fixation body 2 and therefore its position can be adjusted, making it very versatile when additional components or devices need to be associated with the fixation device 1.

[0083] If the fixation device 1 is a pedicle screw, the connection component 8 may advantageously be configured as a "U" and / or tulip shaped element, thereby allowing for operative connection of further devices, such as other fixation devices 1, for example by means of suitable metal elements, if desired metal bars or plates. It is noted that the term "tulip element" is a well-known and recognized term in the field of bone fixation devices, relevant to the field of regenerative and / or reconstructive surgery, such as spinal surgery or trauma surgery.

[0084] According to a non-limiting embodiment of the invention shown in figures 10 and 11, the fixation device 1 is made by a method, which will be described in more detail below, that makes it possible to obtain a connection component 8 already associated or assembled to the fixation body 2. In this way, it is possible to avoid clinical disassembly problems linked to the fact of having a connection component 8 that is initially separate from the fixation body 2 and that is later assembled to the fixation body 2.

[0085] Additionally, the connecting component 8 may include an at least partially porous or complete trabecular volume and / or surface consisting of cells having a regular or irregular pattern. Thus, according to at least one version of the invention, and if desired a preferred version, the head portion 4 is movable relative to the remaining components of the fixation device 1 , such as for example the connection component 8 and / or the fixation body 2 .

[0086] The fixation device 1 is preferably obtained, for example completely or entirely, by a three-dimensional or 3D printing method, and even more preferably by additive manufacturing. This method makes it possible to obtain in a single process, via suitable positioning of the supports for the realization of the fastening device 1, together with a suitable digital design of the fastening device 1, for example the fastening body 2 and, if the connecting component 8 is present, the connecting component 8 already assembled.

[0087] Furthermore, this additive manufacturing method allows the fixation device 1 to be realized in an optimal manner, for example by multi-layer manufacturing, even if the complementary or filling structures and / or volumes 6 of the fixation device 1 include geometrically very complex porous surfaces or structures, porous or trabecular structures, etc.

[0088] According to other non-limiting embodiments of the present invention, only some components of the fixation device 1 can be fabricated by additive manufacturing, if desired, by three-dimensional or 3D printing methods, and assembled only sequentially with the remaining components that make up the fixation device 1.

[0089] Thus, for example, the fixation body 2 may comprise a constraining portion 3 comprising a core or body 5 and a screw thread 7. At least the constraining portion 3 is made by additive manufacturing methods, for example as a single object, and possibly a complementary or filling structure or volume 6 is then inserted or injected or placed into the respective housing or receiving area or space HA. Alternatively, it may be a complementary or filling structure and / or volume 6 that is produced by additive manufacturing and then inserted or constrained by a fixed body 2 that is separately produced by a different method.

[0090] A non-limiting example of the use of the fixation device 1 according to the non-limiting embodiment of the present invention shown in Figures 10 and 11 is described below. As an example, assuming the fixation device 1 is a pedicle screw used in the field of spinal surgery, a surgeon may insert the fixation device 1 into a target bone site.

[0091] The core or body 5, thanks to its optimized first cross section FS with its two L, cross or star configuration, can easily withstand the stresses caused by the insertion of the fixation device 1 into the bone seat. Similarly, the screw threads 7 supported or connected by the respective supporting or connecting ends 5b1 of the protruding or convex portions 5b allow for easier insertion as well as better overall mechanical strength of the fixation device 1.

[0092] Furthermore, thanks to the ball joint connection between the head portion 4 and the connecting component 8, the surgeon can easily adjust the inclination of the connecting component 8 to connect other fixation devices 1 to the connecting component 8 by appropriate connecting bars or plates as needed. Once inserted, the fixation device 1 allows for a significant improvement in the osteointegration capacity of the bone tissue present at the bone implant site, thanks to the complementary or filling structures and / or volumes 6, or more specifically the high volume occupied by the trabecular structures.

[0093] In this regard, the external accessibility of the trabecular structure allows for continuous wetting of the trabecular structure with biological fluids necessary for the growth of bone tissue inside the cavities defined therein. As can be appreciated, with a greater volume of available trabecular structure, bone tissue integration is deeper, stronger and more effective, providing greater fixation and stabilization of the fixation device, resulting in increased resistance to stress.

[0094] The fixation device 1 according to the invention has properties of high mechanical resistance to torsion and bending and at the same time allows the use of a larger volume of material useful for the adaptation or integration of bone tissue, allowing better bone integration compared to fixation devices of the same size manufactured according to the prior art. This is achieved by optimizing the first cross section FS of the core or body 5, i.e., its configuration and its dimensions, given a particular overall cross section MS of the constraining portion 3, as a function of the mechanical strength and volume of the material used for bone tissue matching or integration.

[0095] If the fixation device 1 is used in the field of vertebral surgery, for example as a pedicle screw, these properties of mechanical strength and optimized bone integration make it possible to significantly improve and accelerate the post-operative recovery of the patient.

[0096] Furthermore, the fixation device 1 can also be obtained in a single manufacturing step by three-dimensional or 3D printing methods, such as additive manufacturing, so as to avoid complex assembly operations and to obtain components that are complex from a structural point of view, such as porous or trabecular structures.

[0097] It has thus been seen that the present invention fully achieves the proposed objects. Modifications and variations of the invention are possible within the scope of protection defined by the claims. [Explanation of symbols]

[0098] 1 Bone fixation device 2 Fixed body 3 Restraint part 4 Head part 5 Core or body 6 Complementary or filling structures and / or volumes 7 Thread

Claims

1. a fixation body (2) including a constraining portion (3) engageable with a respective bone seat in use and extending along a first or longitudinal direction, a tip engagement end (EE) and a distal end (CE), and at least one screw thread (7); a head portion (4) connected or connectable to the anchoring body (2) by said distal end (CE), said constraining portion (3) comprising a core or body (5) provided with an overall cross-section (MS) and defining a first cross-section (FS), said core or body (5) comprising at least a central portion (5a) and at least two protruding or convex portions (5b) extending from said central portion (5a), said at least two protruding or convex portions (5b) and said at least one thread (7) defining, together with said central portion (5a), a respective housing or containing area or space (HA); said bone anchoring device (1) also comprises a complementary or filling structure and / or volume (6) defining a second cross section (SS) which together with said first cross section (FS) defines the overall cross section (MS) of said constraining portion (3); 1. A bone anchoring device comprising: at least two protruding or convex portions (5b) arranged such that the first cross section (FS) is in the shape of two L's or in the shape of a cross or in the shape of a star or in the shape of a radial line and at least one of the protruding or convex portions (5b) comprises a support or a connection end (5b1) for or with the screw thread (7).

2. 2. The fixing device (1) according to claim 1, wherein the complementary or filling structure and / or volume (6) comprises at least two complementary or filling portions (6a) and / or the complementary or filling structure and / or volume (6) defining the second cross section (SS) is arranged or contained in the housing or containing area or space (HA).

3. The fixation device (1) according to claim 1 or 2, wherein the complementary or filling structures and / or volumes (6) have a porosity of between 40% and 80%.

4. The complementary or filling structures and / or volumes (6) are 4. The fixation device (1) according to any one of claims 1 to 3, made of a metallic material, such as titanium, a titanium alloy, an alloy of magnesium, a tantalum alloy, stainless steel, or a polymeric material, such as polylactic acid, or a ceramic material, such as hydroxyapatite or brushite.

5. 5. The fixing device (1) according to any one of claims 1 to 4, wherein the second cross section (SS) has a surface bulk between 25% and 65% with respect to the surface of the total cross section (MS).

6. 6. The fixing device (1) according to any one of claims 1 to 5, wherein each housing or containing area or space (HA) is defined by the central portion (5a) as well as by the at least two protruding or convex portions (5b), also from the screw thread (7).

7. 7. The fixation device (1) according to any one of claims 1 to 6, wherein the threads (7) extend concentrically along the longitudinal development of the arresting portion (3) and / or the threads (7) extend with a variable pitch to facilitate engagement of the fixation device (1) in the respective bone seats.

8. 8. The fixation device (1) according to any one of claims 1 to 7, wherein the at least one thread (7) is made integral with the core or body (5) and / or with the complementary or filling structure and / or volume (6).

9. 9. The fixation device (1) according to any one of claims 1 to 8, wherein at least one of the at least two complementary or filling portions (6a) at least partially comprises a structure or surface (6a1) designed to facilitate compatibility or integration of the fixation device (1) with bone tissue during use.

10. 10. The fixation device (1) according to claim 9, wherein said structure or surface (6a1) is a porous or trabecular structure or surface.

11. A fixation device (1) according to any one of the preceding claims, comprising a connection component (8) operatively associated or associable, in use, with said head portion (4).

12. The fixation device (1) according to claim 11, wherein said head portion (4) is operatively associated in a rotational manner with said connecting component (8) via a ball joint connection.

13. The fastening device (1) according to claim 11 or 12, wherein the connection component (8) is formed as a "U"-shaped or tulip-shaped element.

14. The fixation device (1) according to any one of the preceding claims, wherein the fixation body (2) comprises a distal engagement end (EE) opposite the head portion (4) that is shaped like a distal tip.

15. The fixation device (1) according to claim 14, wherein said distal engaging end (EE) comprises at least partially a porous or trabecular structure or surface.

16. 16. The fixation device (1) according to any one of claims 1 to 15, wherein the core or body (5) is made of a biocompatible metallic or polymeric material and / or the complementary or filling structures and / or volumes (6) are made of a biocompatible metallic or polymeric material.

17. 17. The fastening device (1) according to any one of claims 1 to 16, wherein the at least one protruding or convex portion (5b) comprises a first segment (5c) and a second segment (5d), and at least the first segment (5c) and / or at least the second segment (5d) of the protruding or convex portion (5b) has a connection end (5f) between the protruding or convex portion (5b) and the central portion (5a) that has an at least partially curved or tapered development.

18. 18. The fixation device (1) according to any one of claims 1 to 17, wherein the at least two protruding or convex portions (5b) are three, four, five or more and / or the fixation device (1) is a pedicle screw or a bone screw.

19. A fixation device (1) according to any one of the preceding claims, obtained by a three-dimensional or 3D printing method.

20. The fixation device (1) according to claim 19, wherein the three-dimensional or 3D printing method is an additive manufacturing technique.

21. 21. The fixation device (1) according to any one of claims 1 to 20, wherein the ratio between the surface bulk of the first cross section (FS) and the surface bulk of the second cross section (SS) is variable along the longitudinal development of the restraining portion (3).

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