MOTION-PRESERVING SPINAL IMPLANT FOR TOTAL DISC REPLACEMENT.

Abstract

A motion-preserving spinal implant is presented for placement within the intervertebral space for the total replacement of a degenerated spinal disc. The motion-preserving spinal implant has a pair of endplates sandwiched around an inner and an outer core, with the inner core positioned concentrically within the outer core. The outer core encapsulates the inner core and provides a proper seal while maintaining flexibility and elasticity to advantageously support physiological movements. The inner core is constructed of an elastomeric material and acts as a solid diaphragm to resist and withstand localized compression and other forces. The endplates provide anchorage and fusion with the adjacent vertebrae and maintain the inner and outer cores in place.The motion-preserving spinal implant restores normal height and natural function to the degenerated spinal disc and preserves natural spinal movement.

Description

MOTION-PRESERVING SPINAL IMPLANT FOR TOTAL DISC REPLACEMENT FIELD OF INVENTION The present invention relates generally to implants for the human body. More particularly, the present invention relates to a motion-preserving spinal implant for spinal disc replacement. BACKGROUND OF THE INVENTION Spinal implants are intended to treat degenerative disc disease (DDD) or other disc injuries. Spinal fusion is a widely used treatment for pain relief, but it limits a patient's range of motion and mobility. Total disc replacement is another treatment for degenerative disc disease that aims to preserve movement and limit complications associated with spinal fusion, such as wear and tear of the adjacent level and disc degeneration. Total disc replacement is an effective solution for degenerative disc disease and is gaining interest due to the increasing prevalence of neck pain, lower back pain, and pain in general. Therefore, there is a growing need for functional improvement.For example, without limitations, there is a need for total disc replacement spinal implants that reduce wear due to metal-to-metal sliding and corrosive surfaces, increase cushioning, improve shock absorption, reduce metal wear debris, and maintain spinal range of motion. The present invention solves these problems by providing a treatment solution that reduces metal wear due to the absence of slippage between the metal plates, increases damping through effective inner core design features, and utilizes special polymeric and elastomeric materials with varying hardness and physical properties, such as silicone or liquid silicone rubber, which also provides shock absorption. The effective outer core design, its characteristics, and the choice of materials also contribute to maintaining the range of motion. All components of the assembly are designed to effectively resist compressive, shear, and torsional forces. The additional advantages of the invention will be partly set forth in the following description, and partly will be obvious from the description, or can be learned through the practice of the invention. These additional advantages can be realized and achieved by means of the instrumentalities and combinations particularly noted in the detailed description of the invention. Other benefits and advantages of embodiments of the invention will become apparent from consideration of the following detailed description given with reference to the accompanying drawings, which specify and illustrate preferred embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of the present invention. FIG. 2 is an exploded perspective view of the present invention. FIG. 3 is a front view of the present invention. FIG. 4 is a rear view of the present invention. FIG. 5 is a top view and a side sectional view of the present invention. FIG. 6 is a top view and a front sectional view of one of the terminal plates of the present invention. FIG. 7 is a top view, a side sectional view and a side view of the internal core of the present invention. FIG. 8 is a top view, a side sectional view, and a side view of the outer core of the present invention. FIG. 9 is a top view and a side sectional view of an alternative embodiment of the present invention incorporating anchoring protrusions. FIG. 10 is a top view and a side sectional view of one of the end plates of the alternative embodiment. FIG. 11 is a top view and a side sectional view of the outer core in the alternative embodiment. FIG. 12 is an exploded perspective view of a second alternative embodiment of the present invention. FIG. 13 is a top view and a side sectional view of the second alternative embodiment. FIG. 14 is a top view, a side sectional view and a side view of the inner core of the second alternative embodiment. FIG. 15 is a top view, a side sectional view and a side view of the outer core of the second alternative embodiment. FIG. 16 is an exploded perspective view of a third alternative embodiment of the present invention. FIG. 17 is a top view and a side sectional view of one of the end plates of the third alternative embodiment. FIG. 18 is a top view, a side sectional view and a side view of the inner core of the third alternative embodiment. FIG. 19 is a top view, a side sectional view and a side view of the outer core of the third alternative embodiment. FIG. 20 is an exploded perspective view of a fourth alternative embodiment of the present invention. FIG. 21 is a top view and a side sectional view of the fourth alternative embodiment. FIG. 22 is a top view and a side sectional view of one of the end plates of the fourth alternative embodiment. FIG. 23 is a top view, a side sectional view and a side view of the inner core of the fourth alternative embodiment. FIG. 24 is a top view, a side sectional view and a side view of the outer core of the fourth alternative embodiment. DETAILED DESCRIPTIONS OF THE INVENTION All illustrations in the drawings are intended to describe selected versions of the present invention and are not intended to limit its scope. The present invention should be described in detail and is provided in such a way as to establish a complete understanding of the present invention. There may be aspects of the present invention that can be practiced or used without implementing some features as described. It should be understood that some details have not been described in detail so as not to unnecessarily obscure the focus of the invention. References herein to a preferred embodiment, an embodiment, some embodiments, or alternative embodiments should be regarded as illustrative of aspects of the present invention that may potentially vary in some cases and should not be regarded as limiting the scope of the present invention as a whole. The present invention is a spinal implant intended for the total replacement of a degenerated spinal disc. In general, referring to Figures 1-5, the present invention comprises a first end plate 1, a second end plate 2, an inner core 3, and an outer core 4. In some embodiments of the present invention, the first end plate 1, the second end plate 2, the inner core 3, and the outer core 4 each have a generally radial geometry, although it may be noted that other geometries can be used as desired or useful. The inner core 3 and the outer core 4 are substantially wider than they are tall, having a certain thickness, or axial height. As mentioned above, in some embodiments, the inner core 3 and the outer core 4 each have a radial geometry and are generally disc-shaped, having a radial axial cross-section.In some embodiments, the first end plate 1, the second end plate 2, the inner core 3, and the outer core 4 may have other general geometries. For example, as shown in FIGS. 16-24, in some embodiments, the first end plate 1, the second end plate 2, the inner core 3, and the outer core 4 each have a generally rectilinear peripheral geometry with rounded corners. In the preferred embodiment, the inner core 3 is positioned within the outer core 4. In some embodiments, the inner core 3 is positioned concentrically within the outer core 4, wherein the inner core 3 comprises a centerline of the inner core 16 and the outer core 4 comprises a centerline of the outer core 17, as shown in FIGS. 2, 5, 7, 8, 12, 13, and 21. The centerline of the inner core 16 and the centerline of the outer core 17 are positioned to coincide with each other so that the inner core 3 and the outer core 4 are positioned concentrically with each other, as illustrated in FIG. 5.In some embodiments, the inner core 3 and the outer core 4 may be positioned in such a way that they are not exactly concentric, or not concentric, with each other, and therefore the centerline of the inner core 16 and the centerline of the outer core 17 are positioned offset from each other, either through translation or rotation, or both. In the preferred embodiment, the outer core 4 comprises an inner cavity 40, and the inner cavity 40 passes centrally through the outer core 4. This central displacement does not mean that the inner cavity 40 is necessarily concentric with the outer perimeter of the outer core 4, but rather that the inner cavity 40 passes through the outer core 4 in a position generally centralized with respect to the outer perimeter of the outer core 4. In some embodiments, however, the inner cavity 40 is positioned concentrically within the outer core 4, such that the inner cavity 40 passes centrally and axially through the outer core 4. In some other embodiments, the inner cavity 40 may be positioned non-concentrically within the outer core 4.The inner core 3 is positioned within the inner cavity 40 of the outer core 4, where the inner core 3 is sealed by the outer core 4, the first end plate 1, and the second end plate 2. In some embodiments, the inner core 3 is positioned concentrically within the inner cavity 40. In some embodiments, the internal lateral geometry of the inner cavity 40 may be determined by the external lateral geometry of the outer core 4. In some other embodiments, the inner core 3 may be positioned non-concentrically within the inner cavity 40. In various embodiments, the first end plate 1, the second end plate 2, the inner core 3, and the outer core 4 can be positioned concentrically with each other, where each of the first end plate 1, the second end plate 2, the inner core 3, and the outer core 4 comprises a centerline, where the centerlines of the first end plate 1, the second end plate 2, the inner core 3, and the outer core 4 are aligned with each other when the first end plate 1, the second end plate 2, the inner core 3, and the outer core 4 are positioned concentrically with each other.In other embodiments, one or more of the first end plate 1, the second end plate 2, the inner core 3, and the outer core 4 may not be positioned concentrically, or non-concentrically, with respect to each other, wherein the centerlines of one or more of said components may be positioned offset from each other, either by translation or linear rotation—an offset centerline may be positioned parallel to one or more centerlines of the aforementioned components, but offset by a linear distance, or an offset centerline may be oriented at an angle offset from one or more centerlines of the aforementioned components. In some embodiments, such a centerline may also correspond to a radial axis, or axis of revolution, of the generally radial features of said components. In the preferred embodiment, the outer core 4 is connected between the first end plate 1 and the second end plate 2. In some embodiments, as shown in Figures 1-11, the outer core 4 is connected between the first end plate 1 and the second end plate 2 via a plurality of interlocking members 5. In some embodiments, the outer core 4 is connected between the first end plate 1 and the second end plate 2 via an adhesive. Figures 12-15 and 20-24 illustrate examples of such embodiments. The adhesive may be any adhesive suitable for the intended use of the present invention. The adhesive must be sterile, biodegradable, and biocompatible.The adhesive may be based on, derived from, or comprise, but is not limited to, bone cement, polyurethane, acrylates, rubbers, polymers, epoxy resins, phenolic resins, natural adhesives, synthetic adhesives, or any other suitable adhesive substance. Alternatively, the adhesive may be the result of any suitable manufacturing process, rather than a distinct adhesive substance. Thus, the inner core 3 and the outer core 4 are sandwiched between the first end plate 1 and the second end plate 2. More specifically, as mentioned above, the outer core 4 comprises the inner cavity 40 that runs centrally through the outer core 4, with the inner core 3 positioned within the inner cavity 40 of the outer core 4, such that the inner core 3 is sealed by the outer core 4, the first end plate 1, and the second end plate 2. In the preferred embodiment, the inner core 3 is constructed of a polymeric material. More particularly, in various embodiments, the inner core 3 is preferably constructed of a medical-grade or implant-grade polymeric or elastomeric material that may have varying hardness and other physical properties in different embodiments. In some embodiments, the inner core 3 is constructed of a liquid silicone rubber material, wherein the liquid silicone rubber material may have varying hardness properties in different embodiments. In some embodiments, the inner core 3 is constructed of a medical-grade or implant-grade silicone elastomer with a hardness ranging from 60 Shore A to 90 Shore A. In some embodiments, the inner core 3 may be constructed of a liquid silicone rubber (LSR) material. This material is inert and is widely used in medical breast implants.Silicone rubber has the ability to retain its initial shape and mechanical stress under high compression, shear-compression, bending, torsion, and tension, and it has excellent creep properties. In other embodiments, other suitable materials may be used to fabricate the inner core 3. The inner core 3 serves as a solid diaphragm or cushion that resists and withstands localized compression, shear-compression, torsion, and other forces. In various embodiments, the diameter of the inner core 3 may vary between approximately [missing information]. 0.125 inches and 2.25 inches, but it should be understood that the various dimensions of the present invention may vary without departing from the spirit and scope of the present invention. In the preferred embodiment, the inner core 3 comprises a first convexity of core 30 and a second convexity of core 31, as shown in FIGS. 5 and 7. The first convexity of core 30 and the second convexity of core 31 are positioned opposite each other along the thickness of the inner core 3, along the centerline of the inner core 16. In some embodiments, the first convexity of core 30 and the second convexity of core 31 are axially positioned opposite each other along the thickness of the inner core 3, wherein the first convexity of core 30 and the second convexity of core 31 are positioned concentrically with the centerline of the inner core 16. In other embodiments, the first convexity of core 30 and the second convexity of core 31 may be positioned non-concentrically with respect to the centerline of the inner core 16. The first convexity of core 30 and the second convexity of core 31 are essentially centrally positioned protrusions on inner core 3 that contribute to inner core 3's ability to resist and withstand any force to which it is subjected while installed in a human spine. The first convexity of core 30 and the second convexity of core 31 also correspond to, and are coupled with, the inner concavities of first end plate 1 and second end plate 2, as will be discussed later. In various embodiments, the convexity angle of the first core 30 and the second core 31 can range from 5 degrees to 60 degrees, and the outer radius of the first core 30 and second core 31 can range from 0.075 inches to 2 inches.In some embodiments, the inner core 3 further comprises a side wall with a convex curvature, the radius of which may range in various embodiments from 0.063 inches to 2.250 inches, but it should be understood in this document that various dimensions of the present invention may vary without departing from the intended spirit and scope of the present invention. As mentioned above, in some embodiments, the inner core 3 comprises a centerline of the inner core 16, and the outer core 4 comprises a centerline of the outer core 17. The centerline of the inner core 16 and the centerline of the outer core 17 may be considered in some embodiments as an axis equidistant from the outer perimeter of the inner core 3 and the outer core 4, respectively, and / or an axis of revolution for other radial features in some embodiments. Additionally or alternatively, in some embodiments, a radial axis may be considered as such an axis of revolution, and may be considered distinct from the centerline of the inner core 16 and the centerline of the outer core 17 for the inner core 3 and the outer core 4, respectively. In various embodiments, the radial axis may be located offset from the centerline of the inner core 16 and the centerline of the outer core 17.In such embodiments, the first convexity of core 30 and the second convexity of core 31 of the inner core 3 are positioned concentrically about the radial axis of the inner core 3. Furthermore, the inner cavity 40 of the outer core 4 is positioned concentrically about the radial axis of the outer core 4 in such embodiments. In other embodiments, however, the first convexity of core 30 and the second convexity of core 31 of the inner core 3 may be positioned non-concentrically about the radial axis of the inner core 3, and the inner cavity 40 of the outer core 4 may be positioned non-concentrically about the radial axis of the outer core 4 in such embodiments. The outer core 4 acts as a sealing ring for the inner core 3 and provides the necessary movement to the spine once the present invention is implanted in a human body. In the preferred embodiment, the outer core 4 is constructed of a polymeric or elastomeric material with variable hardness and other physical properties in various embodiments. In various embodiments, the outer core 4 may be constructed of various materials. In the preferred embodiment, the outer core is constructed of a polymeric material. In some embodiments, the outer core is constructed of a liquid silicone rubber material, wherein the liquid silicone rubber material may have varying hardness properties in different embodiments. In some embodiments, the outer core 4 may be constructed of an ultra-high-molecular-weight polyethylene (UHMWPE) material. In some embodiments, the outer core 4 may be constructed of a medical-grade polypropylene (PP) material, although the material of the outer core 4 may vary in different embodiments as desired. In general, a material with superior abrasion and corrosion resistance, high strength, light weight, and a low coefficient of friction is desired for the outer core 4.In several embodiments, the diameter of the outer core 4 can vary from 0.175 inches to 2.375 inches, although as mentioned above, any dimensions listed for the various components of the present invention should not be considered limiting and may vary in different embodiments. In the preferred embodiment, the first endplate 1 and the second endplate 2 are each constructed of a polyethylene ether ketone (PEEK) material, although the material of the first endplate 1 and the second endplate 2 may vary in different embodiments. PEEK is increasingly used as a biomaterial for trauma, orthopedic, and spinal implant treatments. It is inherently strong, inert, and biocompatible. Properties that make PEEK a material of choice for endplates include: a bone-like modulus, reduced stress shielding, artifact-free imaging, and an osteoconductive surface for bone growth. Alternatively or additionally, the PEEK material may be used in combination with a titanium material or with a titanium plasma spray on the outer surfaces of the outer core 4.The first end plate 1 and the second end plate 2 can be externally treated with a titanium material. In the preferred embodiment, as shown in FIGS. 1-6, the first end plate 1 and the second end plate 2 each comprise a plate body 20, an inner side 21, an outer side 22, a plate convexity 23, and a concavity 24, wherein a thickness of the plate body 20 extends between the inner side 21 and the outer side 22. In various embodiments, the diameter of the plate body 20 may range from 0.375 inches to 2.5 inches, while the thickness may range from 0.031 inches to 0.375 inches, but it is hereby understood that various dimensions of the present invention may vary without departing from the intended spirit and scope of the present invention. In the preferred embodiment, the plate body 20 of the first end plate 1 and the plate body 20 of the second end plate 2 are oriented at a specified tilt angle 6 relative to each other, as illustrated in FIG. 1. The specified tilt angle 6 defines a deviation of the plate bodies of the first end plate 1 and the second end plate 2 from being oriented parallel to each other. The specified tilt angle 6 may vary in different embodiments, primarily to correspond with different types of spinal discs to be replaced. In various embodiments, the specified tilt angle 6 may range from 0.5 degrees to 15 degrees. In some embodiments, the specified tilt angle 6 may be less than 0.5 degrees.In some embodiments, the specified tilt angle 6 may be 0 degrees, such that the first end plate 1 and the second end plate are oriented parallel to each other. In some embodiments, the specified tilt angle 6 may exceed 15 degrees. The convexity 23 of the plate is located centrally on the outer side 22 of the plate body 20 for each of the first end plate 1 and the second end plate 2; likewise, the concavity 24 is located centrally on the inner side 21 of the plate body 20 for each of the first end plate 1 and the second end plate 2. In some embodiments, the thickness of the plate body 20 is constant, and the plate convexity 23 and concavity 24 are formed through a deviation from the generally planar geometry of the plate body 20, such that the thickness of the end plates at the plate convexity 23 and concavity 24 is equal to the thickness of the end plates at their perimeter. In other embodiments, the convexity of plate 23 and the concavity 24 of the first end plate 1 and the second end plate 2 can be formed independently of each other.In some embodiments, a fillet can be formed between the body of plate 20 and the convexity of plate 23 with a radius of, for example, but not limited to, a range of 0.015 inches to 0.5 inches. The fillet serves to reduce any polymer stress due to localized vertical compressive forces in the first and second end plates 2. The first convexity of core 30 is positioned within the concavity 24 of the first end plate 1, and the second convexity of core 31 is positioned within the concavity 24 of the second end plate 2. As mentioned above, in some embodiments, the outer core 4 is connected between the first end plate 1 and the second end plate 2 via a plurality of interlocking members 5. In some embodiments, the inner core 3 is further connected between the first end plate 1 and the second end plate 2 in the same manner via a plurality of interlocking members 5, although this is not considered a requirement. More specifically, the inner side 21 of the first end plate 1 is connected to the outer core 4 via a plurality of interlocking members 5, and the inner side 21 of the second end plate 2 is connected to the outer core 4 opposite the first end plate 1 axially along the inner core 3 via a plurality of interlocking members 5. In some embodiments, the first end plate 1 and the second end plate 2 further comprise a fixing flange 25 and at least one fastener opening 26, as shown in Figures 1-6. The fixing flange 25 can be used to anchor the present invention to adjacent vertebrae via one or more implant screws. The inclusion of the fixing flange 25 in various embodiments will depend on the requirements of the final product. The fixing flange 25 is connected perpendicularly and around the perimeter of the plate body 20 and extends beyond the inner side 21, passing through the outer side 22 for each of the first end plate 1 and the second end plate 2, where the fixing flange 25 is connected along a flange arc segment of the perimeter of the plate body 20. Preferably, the fixing flange 25 does not extend beyond the inner side 21, although this may vary in different embodiments.At least one opening of fastener 26 passes through the flange of fastener 25 for each of the end plates 1 and 2. Each of the openings of fastener 26 can be a countersunk hole, a countersunk hole, a through hole, or other types of holes suitable for receiving various fasteners in different embodiments. Furthermore, in some embodiments, the fixing flange 25 comprises an internal groove 27. The internal groove 27 passes through and radially traverses the fixing flange 25 along the arc segment of the flange adjacent to the outer side 22 of the plate body 20 and adjacent to a perimeter of the plate body 20 for each of the first end plate 1 and the second end plate 2. The internal groove 27 serves to provide clearance to the edge of the adjacent vertebra where the total disc replacement is being performed to reduce any wear on the vertebral edges. In the preferred embodiment, referring to FIGS. 2 and 5-7, the outer core 4 comprises a first plurality of core interlocking members 50 and a second plurality of core interlocking members 51 of the plurality of interlocking members 5, wherein the first plurality of core interlocking members 50 and the second plurality of core interlocking members 51 are positioned opposite each other along a thickness of the outer core 4. In some embodiments, the first plurality of core interlocking members 50 and the second plurality of core interlocking members 51 are positioned axially opposite each other along the thickness of the outer core. Furthermore, the first end plate 1 and the second end plate 2 further comprise a plurality of plate interlocking members 52 of the plurality of interlocking members 5.The plurality of interlocking members of plate 52 is positioned concentrically around the concavity 24 on the inner side 21 of the plate body 20 for each of the first end plate 1 and the second end plate 2. The first plurality of interlocking members of the core 50 of the outer core 4 engages with the plurality of interlocking members of plate 52 of the first end plate 1, and the second plurality of interlocking members of the core 51 of the outer core 4 engages with the plurality of interlocking members of plate 52 of the second end plate 2. Furthermore, in some embodiments, the present invention further comprises a plurality of interlocking member 7 receiving channels, as shown in FIGS. 2, 5, 6, and 8-11. Each of the plurality of interlocking member 7 receiving channels is positioned concentrically with and adjacent to one of the plurality of interlocking members 5, and each of the plurality of interlocking members 5 is positioned within one of the plurality of interlocking member 7 receiving channels. The plurality of interlocking members 5 and the plurality of interlocking member 7 receiving channels are configured to resist extrusion of the inner core and outer core 4 when the inner core 3 and outer core 4 are subjected to external forces.The specific configuration and shape of the plurality of interlocking members 5 and the plurality of interlocking member receiving channels 7 may vary in different embodiments. For example, in some embodiments, the plurality of interlocking members 5 and the plurality of interlocking member receiving channels 7 have a dovetail coupling configuration as shown in FIGS. 2 and 5-8, wherein the cross-sectional width of each of the plurality of interlocking members 5 increases with the distance from the axial center of the outer core 4, and wherein each of the plurality of interlocking member receiving channels 7 has a shape that is the inverse of the plurality of interlocking members 5 to accommodate them.In some embodiments, a cross-section of each of the plurality of locking members 5 resembles a tooth, having an angular projection with a circular element at the end, wherein the cross-section of the receiving channels of locking members 7 would have a correspondingly negative geometry to receive the tooth. In any case, the distal geometry of the locking members 5 has a greater radial width than the rest of the locking members 5, facilitating the securing of the locking members 5 within the receiving channels of locking members 7. Alternatively, in some embodiments, the locking members 5 and the receiving channels 7 may not vary in thickness, as shown in FIG. 9. More particularly, FIGS. 9-11 illustrate an alternative embodiment in which each of the plurality of interlocking members 5 is oriented at a specified anti-extrusion angle 53 in order to adequately resist extrusion of the inner core 3 and / or the outer core 4 as described above. In this embodiment, more specifically, each of the first plurality of core interlocking members 50, the second plurality of core interlocking members 51, and the plurality of plate interlocking members 52 is oriented at the specified anti-extrusion angle 53. The specified anti-extrusion angle 53 can be defined in various ways, but in this case, the specified anti-extrusion angle 53 is defined with respect to a central axis 15 of the present invention.The central axis 15 can be considered as an axis around which the radial features of the present invention, such as, but not limited to, the inner core 3 and the outer core 4, and the plate body 20, are concentrically positioned. Separate central axes can be defined, as appropriate, for the inner core 3, the outer core 4, and the plate body 20, in order to account for any angular discrepancy due to the specified tilt angle 6. The centerline of the inner core 16 and the centerline of the outer core 17, discussed previously, can, in various embodiments, be the same as or different from the central axis 15. It can be understood here that, due to the specified tilt angle 6, the true centerlines of the plate body 20, the inner core 3, and / or the outer core 4 may not be exactly aligned with each other. However, for the sake of simplicity, this is considered to be the case. It is important to define here that the specified anti-extrusion angle 53 must be oriented radially outward from the central axis, such that an imaginary line extending outward from any given member of the first plurality of core interlocking members 50 or the second plurality of core interlocking members 51 does not intersect the central axis. This is important because an inwardly oriented anti-extrusion angle 53 would not be as effective, or as effective, and might not provide effective interlocking as an outwardly oriented anti-extrusion angle. As mentioned above, the plurality of interlocking members 5 and the plurality of interlocking member receiving channels 7 function primarily to secure the inner core 3 to the first end plate 1 and the second end plate 2, but also secondarily to resist extrusion of the outer core 4 (and of the inner core 3, in applicable embodiments) when the present invention is subjected to external forces, particularly compressive forces. When the present invention is subjected to an axial compressive force, the inner core 3 and the outer core 4 will tend to deform a certain amount axially in compression and laterally in expansion. Thus, it is a concern that, subjected to such forces, portions of the inner core 3 and the outer core 4 will extrude from their designated positions and potentially become misaligned or damaged.The plurality of interlocking member receiving channels 7 can function to provide some space to accommodate said extrusion, and furthermore the physical interlocking between the interlocking members 5 and the interlocking member receiving channels 7 prevents the inner core 3 and the outer core 4 from detaching from their positions relative to the first end plate 1 and the second end plate 2. The quantity of both the plurality of interlocking members 5 and the plurality of interlocking member receiving channels 7 can vary in different embodiments, from 1 to 9, for example, although any number of interlocking members 5 and interlocking member receiving channels 7 can be included as desired in various embodiments. As mentioned above, in various embodiments, the first end plate 1 and the second end plate 2 can be oriented at a specific tilt angle 6 relative to each other to mimic the geometry of a spinal disc to be replaced by the present invention. As such, the plate body 20 of the first end plate 1, the plate body 20 of the second end plate 2, the inner core 3, and the outer core 4 can be understood as extending in a longitudinal direction between a proximal end 8 and a distal end 9. The proximal end 8 and the distal end 9 are positioned diametrically opposite each other for each of the plate bodies 20, the inner core 3, and the outer core 4.The proximal ends 8 are defined here to be radially aligned with each other, and the distal ends 9 are radially aligned with each other for each of the plate bodies of the first end plate 1 and the second end plate 2, the inner core 3, and the outer core 4. Thus, in some embodiments, the specified tilt angle 6 is defined in a plane coincident with the proximal ends 8 and the distal ends 9. In some embodiments comprising the flange fitting, the flange fitting is positioned at the proximal end 8 for each of the first end plate 1 and the second end plate 2. In various embodiments, the orientation and alignment of the specified tilt angle 6 may vary, however, and should not be considered limited to the above description. Furthermore, referring to FIGS. 7-8, in some embodiments, the specified tilt angle 6 can be achieved through a diametral difference in the thickness of the inner core 3 and the outer core 4, so that the axial outer ends of the inner core 3 and the outer core 4 are oriented at the specified tilt angle 6 to each other, and therefore the first end plate 1 and the second end plate 2, generally being flat, are oriented at the specified tilt angle 6 to each other as a result.As such, a proximal thickness 10 and a distal thickness 11 can be defined for both the inner core 3 and the outer core 4, where the proximal thickness 10 of the outer core 4 is the thickness of the outer core 4 at the proximal end 8 of the outer core 4, the distal thickness 11 of the outer core 4 is the thickness of the outer core 4 at the distal end 9 of the outer core 4, the proximal thickness 10 of the inner core 3 is the thickness of the inner core 3 at the proximal end 8 of the inner core 3, and the distal thickness 11 of the inner core 3 is the thickness of the inner core 3 at the distal end 9 of the inner core 3. Therefore, in some embodiments, the proximal thickness 10 of the inner core 3 is greater than the distal thickness 11 of the inner core 3, and the proximal thickness 10 of the outer core 4 is greater than the distal thickness 11 of the outer core 4. Therefore, the specified tilt angle 6 can be determined in some embodiments by the difference between the proximal thicknesses 10 and distal thicknesses 11. In other embodiments, the specified tilt angle 6 can be determined by other means; for example, the thickness of the inner core 3 and the outer core 4 can be constant, while the thickness of the first end plate 1 and the second end plate 2 can vary instead. In some embodiments of the present invention, as shown in FIG. 9, as an alternative to the fixing flange 25, the first end plate 1 and the second end plate 2 further comprise a plurality of anchoring protrusions 12. The plurality of anchoring protrusions 12 serve as an alternative means of mounting the first end plate 1 and the second end plate 2 to adjacent vertebrae. The anchoring protrusions 12 are connected to the outer face 22 and are preferably oriented perpendicular to the body of the plate 20. The anchoring protrusions 12 are distributed around the outer face 22 in any desirable configuration, such as, for example, but not limited to, four anchoring protrusions arranged in a 90-degree concentric pattern around the convexity of the plate 25.Furthermore, each of the anchorage projections 12 may comprise a plurality of teeth 13 positioned at a distal end 14 of the anchorage projections 12. The components of the present invention can be manufactured by any desirable manufacturing process, such as, but not limited to, 3D printing, CNC machining, injection molding, compression molding, or other manufacturing processes. The inner core 3 is preferably injection molded by an insert molding process in which the first end plate 1 and the second end plate 2 serve as inserts. Alternatively, the inner core 3 can be produced independently by injection molding, compression molding, or 3D printing and is subsequently assembled with the first end plate 1 and the second end plate 2. The outer core 4 is preferably injection molded or compression molded by an insert molding process in which an assembly of the first end plate 1, the second end plate 2, and the inner core 3 serve as inserts.Alternatively, the outer core 4 can be produced independently by injection molding, compression molding, or 3D printing and subsequently assembled with the first end plate 1, the second end plate 2, and the inner core 3. Furthermore, in the preferred embodiment, at each assembly stage of the present invention, the external surfaces of the various components of the present invention are treated to increase surface bonding to achieve sufficient covalent, cohesive, and / or adhesive bonds. Figures 12-15 show a second alternative embodiment of the present invention in which the inner cavity 40 of the outer core 4 is positioned off-center with the centerline of the outer core 17, and the first convexity of core 30 and the second convexity of core 31 of the inner core 3 are positioned off-center with the centerline of the inner core 16. Furthermore, the centerline of the inner core 16 and the centerline of the outer core 17 are also offset from each other. This geometric arrangement may have several advantages in different use cases, such as facilitating conformity to a patient's vertebrae. The second alternative embodiment further utilizes the previously discussed adhesive to bond the outer core 4 to the first end plate 1 and the second end plate 2. Figures 16-19 show a third alternative embodiment, in which the peripheral geometry of the inner core 3 and the outer core 4 are generally rectilinear. This geometric arrangement may also have several similar advantages in different use cases or implantation scenarios, such as facilitating the insertion of the present invention between the vertebrae. Figures 20-24 show a fourth alternative embodiment, in which the peripheral geometry of the inner core 3 and the outer core 4 are generally rectilinear, as in the third alternative embodiment, while the outer core 4 is connected between the first end plate 1 and the second end plate 2 via adhesive, as in the second alternative embodiment. Different embodiments comprising various combinations of the aforementioned features may be considered more or less advantageous in various situations, and the present invention should not be considered strictly limited to any of the embodiments specifically described herein. Although the invention has been explained in relation to its preferred embodiment, it should be understood that many other modifications and variations are possible without departing from the spirit and scope of the invention as claimed below.

Claims

1. A motion-preserving spinal implant for total disc replacement comprising a first end plate; a second end plate; an inner core; an outer core; the first end plate and the second end plate each comprising a plate body, an inner side, an outer side, a plate convexity and a concavity, wherein a thickness of the plate body extends between the inner side and the outer side; the inner core comprises a first core convexity and a second core convexity situated opposite each other along a thickness of the inner core; the outer core is connected between the first end plate and the second end plate; the outer core comprises an inner cavity;the inner cavity passes centrally through the outer core; the inner core is located within the inner cavity of the outer core, and the inner core is sealed by the outer core, the first end plate, and the second end plate; the body of the first end plate and the body of the second end plate are oriented at a specified angle of inclination to each other, wherein the specified angle of inclination defines a deviation of the body of the first end plate and the body of the second end plate from their parallel orientation; wherein the convexity of the plate is located at the center of the outer side of the plate body for each of the first and second end plates; the concavity is located centrally on the inner side of the plate body for each of the first and second end plates;The first convexity of the core is located within the concavity of the first extreme plate; and the second convexity of the core is located within the concavity of the second extreme plate.

2. The motion-preserving spinal implant for total disc replacement as claimed in claim 1, comprising: the inner cavity traversing the outer core centrally and axially; and the inner core being positioned concentrically within the inner cavity.

3. The motion preservation spinal implant for total disc replacement as claimed in claim 1, wherein the first end plate, the second end plate, the inner core, and the outer core each have a rectilinear peripheral geometry.

4. The motion-preserving spinal implant for total disc replacement as claimed in claim 1, comprising: the inner core and outer core each comprising a radial axis and a central axis; the radial axis being offset from the central axis for each of the inner and outer cores; and the first convexity of the inner core and the second convexity of the inner core being positioned concentrically around the radial axis of the inner core.

5. The motion-preserving spinal implant for total disc replacement as claimed in claim 1, characterized in that the outer core is connected between the first end plate and the second end plate via an adhesive.

6. The motion-preserving spinal implant for total disc replacement as claimed in claim 1, characterized in that the specified tilt angle is within a range of 0 to 15 degrees.

7. The motion-preserving spinal implant for total disc replacement as claimed in claim 1, characterized in that the inner core is constructed of a polymeric material.

8. The motion-preserving spinal implant for total disc replacement as claimed in claim 1, characterized in that the first endplate and the second endplate are constructed of a polyether ether ketone (PEEK) material.

9. The motion-preserving spinal implant for total disc replacement as claimed in claim 1, characterized in that the inner core is constructed of a liquid silicone rubber with variable hardness.

10. The motion preservation spinal implant for total disc replacement as claimed in claim 1, characterized in that the outer core is constructed of a liquid silicone rubber with variable hardness.

11. The motion-preserving spinal implant for total disc replacement as claimed in claim 1, characterized in that the outer core is constructed of a polymeric material.

12. The motion-preserving spinal implant for total disc replacement as claimed in claim 1, comprising: the first end plate and the second end plate each further comprising a fixing flange and at least one fixing opening; the fixing flange being connected perpendicularly and peripherally to the plate body and extending out of the inner side, passing through the outer side for each of the first end plate and the second end plate, wherein the fixing flange is connected along a flange arc segment of the perimeter of the plate body; and the at least one fixing opening passing through the fixing flange for each of the first end plate and the second end plate.

13. The motion-preserving spinal implant for total disc replacement as claimed in claim 12, comprising: the fixing flange comprising an inner groove; and the inner groove radially traversing the fixing flange along the arc segment of the flange adjacent to the outer side and adjacent to a perimeter of the plate body for each of the first end plate and the second end plate.

14. The motion-preserving spinal implant for total disc replacement as claimed in claim 1, comprising: the outer core being connected between the first end plate and the second end plate through a plurality of interlocking members; the inner side of the first end plate being connected to the outer core through the plurality of interlocking members; the inner side of the second end plate being connected to the outer core through the plurality of interlocking members opposite the first end plate along the thickness of the inner core.

15. The motion-preserving spinal implant for total disc replacement as claimed in claim 14, comprising: the outer core comprising a first plurality of core locking members and a second plurality of core locking members, characterized in that the first plurality of core locking members and the second plurality of core locking members are positioned opposite each other along a thickness of the outer core; the first end plate and the second end plate further each comprising a plurality of plate locking members that are positioned concentrically around the concavity on the inner side of the plate body for each of the first end plate and the second end plate;the first plurality of outer core interlocking members is coupled to the plurality of first end plate interlocking members; and the second plurality of outer core interlocking members are coupled to the plurality of second end plate interlocking members.

16. The motion-preserving spinal implant for total disc replacement as claimed in claim 15, comprising a plurality of locking member receiving channels; each of the plurality of locking member receiving channels is positioned concentrically with and adjacent to one of the plurality of locking members; and each of the locking members is positioned within one of the locking member receiving channels, wherein the plurality of locking members and the plurality of locking member receiving channels are configured to resist extrusion of the inner core and outer core when the inner core and outer core are subjected to external forces.

17. The motion-preserving spinal implant for total disc replacement as claimed in claim 1, comprising: the first end plate body, the second end plate body, the inner core, and the outer core, each of which extends longitudinally between a proximal end and a distal end, wherein the proximal end and the distal end are located diametrically opposite each other for each of the plate bodies, the inner core, and the outer core, characterized in that the proximal ends are radially aligned with each other and the distal ends are radially aligned with each other for each of the plate bodies of the first end plate and the second end plate, the inner core, and the outer core, and wherein the specified tilt angle is defined in a plane coincident with the proximal ends and the distal ends.

18. The motion-preserving spinal implant for total disc replacement as claimed in claim 17, comprising: the first end plate and the second end plate each further comprising a flange attachment; and the flange attachment being positioned at the proximal end for each of the first end plate and the second end plate.

19. The motion-preserving spinal implant for total disc replacement as claimed in claim 17, comprising: a proximal inner core thickness at the proximal end of the inner core that is greater than a distal inner core thickness at the distal end of the inner core; and a proximal outer core thickness at the proximal end of the outer core that is greater than a distal outer core thickness at the distal end of the outer core, characterized in that the specified tilt angle is determined by the difference between the proximal and distal thicknesses.

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