Intervertebral implant for quadruped

Abstract

To provide an improved system for providing intervertebral fixation of a quadruped, and in particular of a canine.SOLUTION: A low-profile intervertebral implant 20 for implantation in an intervertebral disc space between adjacent vertebral bodies of a quadruped, is provided. The intervertebral implant 20 includes a plate 34 and a spacer 36 that extends from the plate 34. The intervertebral implant 20 may define geometries that nest with complementary geometries of the vertebral bodies. Further, the plate 34 can include fixation holes that extend along trajectories such that screws inserted through the fixation holes and driven into the respective vertebral bodies can engage with dense cortical bone.SELECTED DRAWING: Figure 2B

Description

[Background technology]

[0001] Cervical spondylotic myelopathy (CSM), also known as wobbler's disease, affects primarily large and giant breed canines, such as Dobermans and Great Danes. Wobbler's disease can cause canines to have an unsteady gait and weakness. CSM can be caused by many different conditions, including vertebral deformities, disc protrusions, spinal stenosis, and disease of the interspinous ligaments, ligamentum flavum, and vertebral facets. Instability can result in compression of the spinal cord.

[0002] Surgical interbody fusion is often performed to fuse adjacent vertebrae together, thereby eliminating spinal cord compression. Conventional surgical procedures include distraction of vertebral bodies, bridging of the intervertebral disc space with an intervertebral spacer, typically made of polymethylmethacrylate (PMMA), and fixation of the spacer into the intervertebral disc space using screws or pins or the like. However, current surgical techniques carry the risk of complications such as dislodging of screws or pins, cracking of the spacer, laceration of the vertebral artery, spinal nerves, nerve roots, and trauma to the spinal cord. Complications may also include improper placement of pins or screws that are intended to be bicortical, meaning that they are intended to be screwed into both the proximal and distal cortices of the vertebral body. Summary of the Invention [Problem to be solved by the invention]

[0003] Therefore, what is needed is an improved system for providing intervertebral fusion in quadrupeds, particularly canines. [Means for solving the problem]

[0004] In one example, the intervertebral implant is configured to be implanted in a tetrapod intervertebral disc space defined by a cranial vertebral body and a caudal vertebral body. The implant may include a plate defining a ventral plate end and a dorsal plate end spaced apart in a dorsal direction opposite the ventral plate end. The plate may further include a plurality of fixation apertures extending through the plate from the ventral plate end to the dorsal plate end. The implant may further include a spacer extending in a dorsal direction from the plate. The spacer may define a caudal surface and a cranial surface opposite the caudal surface in a cranial direction. The caudal and cranial surfaces may be configured to grip the caudal and cranial vertebral bodies, respectively. The cranial surface may be convex in a first plane oriented along the dorsal and cranial directions, and the cranial surface may be convex in a second plane oriented along the cranial direction and a lateral direction substantially perpendicular to each of the dorsal and cranial directions. The caudal surface can be substantially straight and linear in a first plane, and the caudal surface can be convex in a second plane. [Brief description of the drawings]

[0005] The foregoing summary of the invention, as well as the following detailed description of the preferred embodiments of the present application, will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the preferred intervertebral implants of the present application, there are shown in the drawings preferred embodiments. It should be understood, however, that the present application is not limited to the precise arrangements and instrumentalities shown. The drawings are as follows: [Figure 1A] FIG. 1 is a cross-sectional view showing a portion of a canine spinal column and an intervertebral implant implanted within the intervertebral space between adjacent vertebrae. [Figure 1B] FIG. 1B is another cross-sectional view of the portion of the spinal column shown in FIG. 1A. [Figure 2A] 1B is a top view of the intervertebral implant shown in FIG. 1A showing the plate and spacer. [Figure 2B] FIG. 2B is a side view of the intervertebral implant shown in FIG. 2A. [Figure 2C] FIG. 2B is an end view of the intervertebral implant shown in FIG. 2A. [Diagram 3] 2B is another end view of the intervertebral implant shown in FIG. 2A. [Figure 4] 2B is a side view of one of a plurality of bone screws configured to secure the intervertebral implant shown in FIG. 2A to the adjacent vertebrae of FIG. 1A. [Figure 5A] FIG. 2B is a side view of the intervertebral implant shown in FIG. 2A showing the trajectories of the cranial and caudal fixation apertures extending through the plate. [Figure 5B] FIG. 2B is a cranial plan view of the intervertebral implant shown in FIG. 2A showing the lateral trajectory of the cranial fixation apertures extending through the plate. [Figure 5C] FIG. 2B is a caudal plan view of the intervertebral implant shown in FIG. 2A showing the lateral trajectory of the caudal fixation aperture extending through the plate. [Figure 6A] 2B is an end view of the intervertebral implant shown in FIG. 2A, but including a bone graft retaining cavity according to another embodiment. [Figure 6B] FIG. 6B is a cranial plan view of the intervertebral implant shown in FIG. 6A. [Figure 6C] FIG. 6B is a caudal plan view of the intervertebral implant shown in FIG. 6A. [Figure 6D] FIG. 6B is a side view of the intervertebral implant shown in FIG. 6A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] The present disclosure may be more readily understood by reference to the following detailed description in conjunction with the accompanying drawings and examples, which form a part of this disclosure. It is to be understood that the present disclosure is not limited to the specific devices, methods, applications, conditions, or parameters described and / or illustrated herein, and that the terminology used herein is for the purpose of describing specific embodiments by way of example only, and is not intended to limit the scope of the present disclosure. Also, as used herein, the singular forms "a", "an", and "the" include "at least one" and the plural, unless otherwise indicated. Furthermore, as used herein, references to the plural include the singular "a", "an", "one", and "the", unless otherwise indicated. Furthermore, the term "at least one" can include the singular "a", "an", and "the", and can further include the plural, unless otherwise indicated. Furthermore, references to a particular numerical value in the specification, including the appended claims, include at least that particular value, unless otherwise indicated.

[0007] The term "plurality," as used herein, means more than one, e.g., two or more. When a range of values ​​is expressed, it includes, in another embodiment, from one particular value and / or to the other particular value. The terms "substantially" and "approximately," when used herein in reference to a shape, size, or other parameter or numerical value, include the stated shape, size, or other parameter or numerical value, and further include plus or minus 10% of the stated shape, size, or other parameter or numerical value.

[0008] 1A-1B, an intervertebral implant 20 is configured to be implanted within a spinal column 22 of a quadruped, which may be a canine. The quadruped spinal column 22 includes a plurality of vertebrae 24 that, in a healthy quadruped, are separated from one another by a disc space 26 that contains disc material. The vertebrae 24 include a first or cranial vertebral body 28 and an adjacent second or caudal vertebral body 30 separated from the cranial vertebral body 28 by a corresponding disc space 32. If the quadruped is suffering from a condition indicative of fusion of adjacent vertebral bodies 28 and 30, then the intervertebral implant 20, fusing the vertebral bodies 28 and 30 to one another, may be implanted within the disc space 32 following a discectomy procedure in which some or all of the disc material is removed from the disc space 32. In one example, the quadruped may be suffering from CSM, and thus the vertebral bodies 28 and 30 may be cervical vertebral bodies. Although the intervertebral implant 20, as described below, may include features designed to be implanted within the cervical region of the spine, it should be understood that the vertebral bodies 28 and 30 may instead be located in the thoracic or lumbar regions of a quadruped.

[0009] 2A-2B, the implant 20 may include a plate 34 and a spacer 36 extending from the plate 34. The spacer 36 is preferably configured and dimensioned to be implanted within the intervertebral disc space 32 between the first vertebral body 28 and the second vertebral body 30. The spacer 36 is preferably sized and configured to maintain and / or restore a desired disc height between the adjacent vertebral bodies 28 and 30. The plate 34 may be configured to be secured to the first vertebral body 28 and the second vertebral body 30.

[0010] The intervertebral implant 20 may be constructed of any suitable material or combination of materials, including, but not limited to, polymers (e.g., PEEK), titanium, titanium alloys, stainless steel, nitinol, tantalum nitride (TaN), allograft bone, bioabsorbable materials, magnesium, composite materials, synthetic bone weld polymers, and the like. The plate 34 may be formed of a different material than the spacer 36. For example, the plate 34 may be formed of a metallic material, such as, for example, titanium or a titanium alloy, and the spacer 36 may be formed of a non-metallic material, such as, for example, allograft, polymers, bioabsorbable materials, ceramics, and the like. Alternatively, the plate 34 and the spacer 36 may be formed of the same material. For example, the plate 34 and the spacer 36 may both be constructed of tantalum nitride (TaN) or any suitable alternative material as desired.

[0011] The spacer 36 may include a first or anterior end 38 for insertion into the intervertebral disc space 32 and a second or posterior end 40 opposite the anterior end 38 along the longitudinal direction L. Thus, an anterior or insertion direction into the intervertebral disc space 32 may refer to a direction from the posterior end 40 toward the anterior end 38. A posterior direction opposite the anterior direction may refer to a direction from the anterior end 38 toward the posterior end 40. The intervertebral implant 20 may be configured such that the insertion direction is oriented along any suitable approach as desired, including, but not limited to, a lateral approach. Thus, the anterior end 38 may be referred to as the dorsal end and the posterior end 40 may be referred to as the ventral end. Additionally, the anterior or insertion direction may be referred to as the dorsal direction and vice versa. The posterior direction may be referred to as the ventral direction and vice versa. The ventral direction is opposite the dorsal direction. Thus, the term "longitudinal direction L" can be used interchangeably with dorsal-ventral direction, i.e., either or both of the dorsal and ventral directions, and vice versa. The ventral-dorsal direction includes each of the dorsal and ventral directions.

[0012] The spacer 36 may extend along a central spacer axis 37. The central spacer axis 37 may be oriented along a longitudinal direction L and may bisect the spacer 36 into two halves having substantially equal size and shape. The spacer 36 may include a first wall or cranial wall defining an outer first surface or cranial side 42. The outer cranial side 42 is configured to face in a cranial direction when implanted. The spacer 36 may include a second wall or caudal wall defining an outer second surface or caudal side 44. The outer caudal side 44 is configured to face in a caudal direction when implanted. Thus, the caudal side 44 may face opposite the cranial side 42 along a transverse direction T that is substantially perpendicular to the longitudinal direction L. The caudal side 44 may be further said to be in an opposite caudal direction from the cranial side 42. Similarly, the cranial side 42 may be further said to be in an opposite cranial direction from the caudal side 44. Thus, the term "lateral T" can be used interchangeably with either or both of the cranial and caudal directions, and vice versa. The caudal-cephalic direction includes each of the caudal and cranial directions.

[0013] The spacer 36 may further include opposing first and second sidewalls 43 and 45 opposed to one another along a lateral direction A substantially perpendicular to each of the lateral direction T and the longitudinal direction L. The spacer may define a midplane 39 (see FIGS. 5B-5C ) oriented along the longitudinal direction L and the lateral direction T and including a central spacer axis 37. The midplane 39 may thus divide the spacer 36 into equal lateral halves. The midplane 39 may further divide the plate 34 into equal lateral halves. Additionally, the implant 20 may be substantially symmetrical about the midplane 39.

[0014] 2A-2B , when spacer 36 is positioned within disc space 32, cranial side surface 42 can be configured to face cranial vertebral body 28, and caudal side surface 44 can be configured to face caudal vertebral body 30. Further, when spacer 36 is positioned within disc space 32, cranial side surface 42 can be configured to abut cranial vertebral body 28, and caudal side surface 44 can be configured to abut caudal vertebral body 30.

[0015] In one example, when the spacer 36 is positioned within the disc space 32, the cranial side surface 42 can be configured to grip the cranial vertebral body 28 and the caudal side surface 44 can be configured to grip the caudal vertebral body 30. The intervertebral implant 20 can include a plurality of teeth 46 projecting from the cranial side surface 42 and the caudal side surface 44, respectively. The teeth 46 are configured to penetrate the vertebral endplates of the corresponding cranial and caudal vertebral bodies 28 and 30. Thus, the intervertebral implant 20 can be configured to resist migration within the disc space 32 after implantation. The teeth 46 can be configured in any suitable manner as desired. Specifically, the teeth 46 can include a front surface 47 relative to the direction of insertion and a rear surface 48 opposite the front surface 47. The front surface 47 can be convex and the rear surface 48 can be concave. The front surface 47 and the rear surface 48 can converge to a sharp pointed tip 49. The distal ends of the front face 47 and the rear face 48 may extend along a rearward direction as they converge to a tip 49 .

[0016] Alternatively or in addition, the spacer 36 may include one or more windows 50 designed to accommodate bone graft material. The bone graft material may further fuse the intervertebral implant 20 to the first vertebral body 28 and the second vertebral body 30. The windows 50 may extend from the cranial side 42 to the caudal side 44. The windows 50 may be configured to accommodate bone graft material to promote bone growth through the windows 50 after implantation of the intervertebral implant 20 into the disc space 32. Alternatively or in addition, the spacer 36 may have one or more lateral channels extending through the spacer 20 from either one or both of the side walls 45 for accommodating bone graft material. In some instances, the lateral channels may open to the windows 50. The spacer 36 may include a plurality of longitudinally oriented ribs 51 and laterally oriented ribs 53 separating and defining the windows 50. The teeth 46 may extend outwardly from the ribs 51 and 53.

[0017] The spacer 36 can be shaped to substantially match the geometry of the vertebral endplates of the first vertebral body 28 and the second vertebral body 30. In one example shown in FIG. 2B, at least a portion, and up to the entirety, of the head side surface 42 can be curved as it extends in the insertion direction. For example, at least a portion, and up to the entirety, of the head side surface 42 can be curved as it extends from the plate 34 to the anterior end 38. Specifically, at least a portion, and up to the entirety, of the head side surface 42 can be convex as it extends from the plate 34 to the anterior end 38. Thus, the head side surface 42 can be curved in a first plane oriented along the longitudinal direction L and the lateral direction T. For example, the head side surface 42 can be convex in the first plane oriented along the longitudinal direction L and the lateral direction T. The head side surface 42 can be defined by a first radius of curvature in the first plane, which can range from about 5 mm to about 20 mm. For example, the first radius of curvature can range from about 10 mm to about 15 mm. In one example, the first radius of curvature can be about 11 mm. In another example, the first radius of curvature can be about 15 mm. Furthermore, the first radius of curvature can be constant or variable along the length of the head side surface 42 in the first plane. Thus, a first portion of the head side surface 42 can be defined by a radius of curvature of about 11 mm, and a second portion of the head side surface 42 can be defined by a radius of curvature of about 15 mm. In one example, the head side surface 42 can be convex in all of a first plane disposed from the first sidewall 43 to the second sidewall 45 oriented along the longitudinal direction L and the lateral direction T.

[0018] 2B , at least a portion, and up to the entirety, of the caudal surface 44 can be substantially straight and linear as it extends in the insertion direction. For example, at least a portion, and up to the entirety, of the caudal surface 44 can be substantially straight and linear as it extends from the plate 34 to the anterior end 38. For example, at least a portion, and up to the entirety, of the caudal surface 44 can be substantially straight and linear as it extends from the plate 34 to the anterior end 38. Thus, the caudal surface 44 can be straight and linear in a first plane oriented along the longitudinal direction L and the lateral direction T. In one example, the cranial surface 42 can be substantially straight and linear in all of a first plane disposed from the first sidewall 43 to the second sidewall 45 oriented along the longitudinal direction L and the lateral direction T.

[0019] Further, as shown in FIG. 2C, each of the head side surface 42 and the caudal side surface 44 may be curved in a plane oriented along the lateral direction T and the lateral direction A. Specifically, at least a portion, and up to the entirety, of the head side surface 42 may be curved as it extends along the lateral direction A. For example, at least a portion, and up to the entirety, of the head side surface 42 may be curved as it extends from the first side wall 43 to the second side wall 45. Specifically, at least a portion, and up to the entirety, of the head side surface 42 may be convex as it extends from the first side wall 43 to the second side wall 45. Thus, the head side surface 42 may be curved in a second plane oriented along the lateral direction A and the lateral direction T. For example, the head side surface 42 may be convex in the second plane oriented along the lateral direction A and the lateral direction T. The head side surface 42 may be defined by a second radius of curvature in the second plane ranging from about 10 mm to about 25 mm. For example, the second radius of curvature may range from about 15 mm to about 20 mm. In one example, the second radius of curvature may be about 17 mm. Furthermore, the second radius of curvature may be constant or variable along the length of the cephalad surface 42 in the second plane. Thus, the radius of curvature of the cephalad surface 42 in the second plane may be greater than the first radius of curvature of the cephalad surface 42 in the first plane. In one example, the cephalad surface 42 may be convex in all second planes disposed from the first sidewall 43 to the second sidewall 45 oriented along the lateral directions A and T. Thus, the cephalad surface 42 may be geometrically configured to match the complementary geometry of the vertebral endplates of the cephalad vertebral body 28.

[0020] Similarly, with continued reference to FIG. 2C, at least a portion, and up to the entirety, of the caudal surface 44 may be curved as it extends along the lateral direction A. For example, at least a portion, and up to the entirety, of the caudal surface 44 may be curved as it extends from the first sidewall 43 to the second sidewall 45. Specifically, at least a portion, and up to the entirety, of the caudal surface 44 may be convex as it extends from the first sidewall 43 to the second sidewall 45. Thus, the caudal surface 44 may be curved in a second plane oriented along the lateral direction A and the lateral direction T. For example, the caudal surface 44 may be convex in the second plane oriented along the lateral direction A and the lateral direction T. The caudal surface 44 may be defined by a radius of curvature in the second plane ranging from about 5 mm to about 25 mm. For example, the radius of curvature of the caudal surface 44 in the second plane may range from about 10 mm to about 20 mm. In one example, the radius of curvature of the caudal surface 44 in the second plane may be about 15 mm. Thus, the radius of curvature of the caudal surface 44 in the second plane may be less than the second radius of curvature of the cranial surface 42 in the second plane. In one example, the cranial surface 42 may be convex in all second planes disposed from the first sidewall 43 to the second sidewall 45 oriented along the lateral direction A and the lateral direction T. Thus, the caudal surface 44 may be geometrically configured to match the complementary geometry of the vertebral endplates of the caudal vertebral body 30. In one example, the cranial surface 42 and the caudal surface 44 may extend substantially parallel to one another in the second plane. Although specific geometries of the cranial surface 42 and the caudal surface 44 are described in one example, the geometries may vary as desired.

[0021] 2A-3, the plate 34 may be monolithic with the spacer 36. Alternatively, the plate 34 may be separate from and attached to the spacer 36. The plate 34 may extend outwardly along the lateral direction A relative to both the first sidewall 43 and the second sidewall 45 of the spacer 36. Further, the plate 34 may extend outwardly in a cranial direction a first distance relative to the cranial side surface 42 of the spacer 36. Still further, the plate 34 may extend outwardly in a caudal direction a second distance relative to the caudal side surface 44 of the spacer 36. In one example, the second distance may be greater than the first distance. Alternatively, the second distance may be substantially less than or equal to the first distance.

[0022] The plate 34 may define a first end or dorsal plate end 54 and a second end or ventral plate end 56 disposed opposite the dorsal plate end 54. The ventral plate end 56 may face away from the spacer 36. The dorsal plate end 54 is in a dorsal direction opposite the ventral plate end 56. It should be understood that the anatomical terms "cephalad," "caudal," "dorsal," "ventral," and other anatomical directional terms applied to the implant 20 may apply to the corresponding anatomical orientation when the implant 20 is implanted. The anatomical terms may similarly be applied as relative directional terms when the implant 20 is positioned outside the body. A cranial portion 55 of the dorsal plate end 54 may extend in a cranial direction outward relative to the cranial surface 42 of the spacer 36. A caudal portion 57 of the dorsal plate end 54 may extend in a caudal direction outward relative to the caudal surface 44 of the spacer 36. The caudal portion 57 of the dorsal plate end 52 may extend outwardly relative to the caudal surface 44 of the spacer 36 a distance greater than the distance that the cranial portion 55 of the dorsal plate end 52 extends outwardly relative to the cranial surface 42 of the spacer 36 .

[0023] Further, as shown in FIG. 5A , the cranial portion 55 of the dorsal plate end 54 and the cranial surface 42 of the spacer 36 may define a concave surface 59 in a first plane at the cranial interface between the spacer 36 and the plate 34. Thus, the implant 20 may include a cranial implant surface configured to be inserted into the intervertebral space and nest with the anatomical geometry of the cranial vertebral body 30. The cranial implant surface may include the cranial surface 42 and the cranial interface. Thus, the cranial implant surface, which may be defined by the cranial surface 42 of the spacer 36 and the cranial portion 55 of the dorsal plate end 52, may define a concave shape in a first plane oriented along the lateral direction T and the longitudinal direction L. The concave shape may include a concave portion defined at the interface between the cranial portion 55 of the dorsal plate end 52 and the cranial surface 42 of the spacer 36. The convex portion of the concave shape may be defined by the convex cranial surface 42 of the spacer 36.

[0024] The caudal portion 57 of the dorsal plate end 52 and the caudal surface 44 of the spacer 36 can combine to define a caudal recess 61 in a first plane at the caudal interface between the spacer 36 and the plate 34. Thus, the implant 20 can define a caudal implant surface configured to be inserted into the intervertebral space and nest with the anatomical geometry of the caudal vertebral body 30. The caudal implant surface of the implant can include the caudal surface 44 of the spacer 36 and the caudal interface between the spacer 36 and the plate 34. At least a portion of the caudal recess 61 can be offset in a ventral direction from the cranial recess 59. Additionally, the caudal recess 61 can have a greater curvature than the cranial recess 59. As shown in FIG. 1A, the cranial portion 55 of the dorsal plate end 52 can face or abut the cranial vertebral body 28 and the caudal portion 57 of the dorsal plate end 52 can face or abut the caudal vertebral body 30.

[0025] 3-5C, the implant 20 may include at least one fixation aperture 63, e.g., multiple fixation apertures, extending through the plate 34. Specifically, the at least one fixation aperture 63 may extend from the ventral plate end 56 to the dorsal plate end 54. The at least one fixation aperture 63 extends from the ventral plate end 56 to the dorsal plate end 54 along a central aperture axis. The intervertebral implant system may include the implant 20 and at least one bone fixation element 58 configured to be inserted through the corresponding at least one fixation aperture and driven into an aligned one of the cranial and caudal vertebral bodies, thereby securing the implant 20 to the corresponding vertebral body. The bone fixation element 58 may be configured as a bone screw 60 having a head 62 and a shaft 64 extending outwardly relative to the head 62 and configured to mate with a bone. The shaft 64 may include at least one screw 66 configured to threadably mate with a bone. Thus, as the bone screw 60 is driven into the vertebral body, the threaded shaft 64 threadably engages the vertebral body.

[0026] The at least one bone screw 60 may be configured as a set screw configured to mate with an implant within a corresponding at least one fixation aperture 63. Thus, the head 62 may have at least one thread 68, and the implant 20 may have at least one thread 70 within the at least one fixation aperture 63. Thus, the threads of the bone screw head 62 may mate with the threads of the implant 20 as the bone screw 60 is driven into the vertebrae.

[0027] Alternatively, at least one bone screw 60 may be configured as a compression screw that applies a compressive force to the implant 20 against the vertebral body as the bone screw is driven into the vertebral body. Thus, the head 62 of the bone screw 60 may be unthreaded and thus configured to apply a compressive force against the plate 34 at the corresponding at least one fixation aperture 63 as the shaft 64 is driven into the vertebral body. Thus, the at least one fixation aperture 63 is similarly unthreaded and may receive a force from the head 62, which in turn causes the implant 20 to compress towards or against the corresponding vertebral body.

[0028] In one example, the at least one fixation aperture 63 may include at least one cranial fixation aperture extending along a cranial aperture axis. Specifically, the at least one fixation aperture 63 may include a pair of cranial fixation apertures including a first cranial fixation aperture 72 and a second cranial fixation aperture 74. The first cranial fixation aperture 72 may define a first or dorsal opening 76a at the dorsal plate end 54 of the plate 34 and a second or ventral opening 76b at the ventral plate end 56 of the plate 34. The first cranial fixation aperture 72 may extend along a first cranial aperture axis 78. Thus, the first cranial aperture axis 78 may extend through the center of each of the dorsal opening 76a and the ventral opening 76b. The first cranial aperture axis 78 may be straight and linear.

[0029] 5A, the first cranial fixation aperture 72 may be oriented along a trajectory that flares outward in a cranial direction as the first cranial fixation aperture 72 extends in a dorsal direction. Thus, the first cranial aperture axis 78 may flares outward in a cranial direction as the first cranial aperture axis 78 extends in a dorsal direction. Thus, it should be appreciated that the center of the dorsal opening 76a may be offset in a cranial direction relative to the center of the ventral opening 76b. It should be appreciated that the first cranial aperture axis 78 may define a cranial angle 80 relative to a reference plane 41 oriented along the lateral direction A and the longitudinal direction L, as viewed from the lateral direction A of the first cranial aperture axis 78 and the reference plane 41. Thus, the angle 80 defines the extent to which the first cranial aperture axis 78 flares in a cranial direction as it extends in a dorsal direction. The angle 80 may be any suitable angle as desired. In one example, angle 80 can be in the range of about 5 degrees to about 45 degrees. For example, angle 80 can be in the range of about 10 degrees to about 30 degrees. In one example, angle 80 can be in the range of about 15 degrees to about 25 degrees. For example, the angle can be about 20 degrees.

[0030] Additionally, the first cranial aperture axis 78 may move away from the cranial side surface 42 of the spacer 36 in a cranial direction as the axis 78 exits the plate 34 and as the first cranial aperture axis 78 extends in a dorsal direction from the plate 34. Further, the entire first dorsal opening 76a may be offset in a cranial direction from the cranial side surface 42 of the spacer 36. Thus, when a bone screw 60 is inserted through the first cranial fixation aperture 72, the entire bone screw shaft 62, which extends dorsally outward from the first cranial fixation aperture 72, may move away from the cranial side surface 42 of the spacer 36 in a cranial direction. Further, because the bone screw shaft 62 extends along the first cranial aperture axis 78, the bone screw shaft 62 extends outward in a cranial direction as it extends in a dorsal direction.

[0031] 5B-5C, the first cranial aperture axis 78 may further extend laterally inward (or medially) toward the midplane of the spacer 36 as the axis 78 extends dorsally through the plate 34. Thus, the center of the dorsal opening 76a may be spaced a first distance from the midplane 39 along the lateral direction A, and the center of the ventral opening 76b may be spaced a second distance from the midplane 39 along the lateral direction A that is greater than the first distance. The first cranial aperture axis 78 and the midplane 39 may define a cranial lateral angle 82, which may be any suitable angle, as desired. In one embodiment, the angle 82 may range from about 5 degrees to about 25 degrees. For example, the angle 82 may range from about 10 degrees to about 15 degrees. In one particular example, the angle 82 may be about 12 degrees. The first cranial aperture axis 78 may be spaced dorsally from the anterior end 38 of the spacer 36 and thus intersect the midplane 39 at a location that is outside the footprint of the spacer 20 .

[0032] The second cranial fixation aperture 74 may define a first opening, a dorsal opening 84a, at the dorsal plate end 54 of the plate 34 and a second opening, a ventral opening 84b, at the ventral plate end 56 of the plate 34. The second cranial fixation aperture 74 may extend along a second cranial aperture axis 86. As such, the second cranial aperture axis 86 may extend through the center of each of the dorsal opening 84a and the ventral opening 84b. The second cranial aperture axis 86 may be straight and linear.

[0033] As shown in FIG. 5A, the second cranial fixation aperture 74 may be oriented along a trajectory that flares outward in a cranial direction as the second cranial fixation aperture 74 extends in a dorsal direction. Thus, the second cranial aperture axis 86 may flares outward in a cranial direction as the second cranial aperture axis 86 extends in a dorsal direction. Thus, it should be appreciated that the center of the dorsal opening 84a may be offset in a cranial direction relative to the center of the ventral opening 84b. It should be appreciated that the second cranial aperture axis 86 may define a cranial angle 82 relative to a reference plane 41 oriented along the lateral direction A and the longitudinal direction L as viewed from the lateral direction A of the first cranial aperture axis 86 and the reference plane 41.

[0034] Additionally, the second cranial aperture axis 86 may move away from the cranial side surface 42 of the spacer 36 in a cranial direction as the axis 86 exits the plate 34 and as the axis 78 extends in a dorsal direction from the plate 34. Further, the entire dorsal opening 84a may be offset in a cranial direction from the cranial side surface 42 of the spacer 36. Thus, when the bone screw 60 is inserted through the second cranial fixation aperture 74, the entire bone screw shaft 62, which extends dorsally outward from the second cranial fixation aperture 74, may move away from the cranial side surface 42 of the spacer 36 in a cranial direction. Further, because the bone screw shaft 62 extends along the second cranial aperture axis 86, the bone screw shaft 62 extends outward in a cranial direction as it extends in a dorsal direction.

[0035] 5B, the second cephalad aperture axis 86 may further extend laterally inward (or medially) toward the midplane 39 of the spacer 36 as the axis 86 extends dorsally through the plate 34. Thus, the center of the dorsal opening 84a may be spaced a first distance from the midplane 39 along the lateral direction A, and the center of the ventral opening 84b may be spaced a second distance from the midplane 39 along the lateral direction A that is greater than the first distance. The second cephalad aperture axis 86 and the midplane 39 may define the lateral angle 82 described above. The second cephalad aperture axis 86 may intersect with the midplane 39 at a location that is spaced dorsally from the anterior end 38 of the spacer 36 and thus outside the footprint of the implant 20.

[0036] The first and second cranial fixation apertures 72 may be spaced substantially equidistant from the mid-plane 39 and positioned on opposite sides of the mid-plane 39. Further, the first and second cranial aperture axes 78 and 86 may converge toward one another at an angle that may be approximately twice the lateral angle 82. Further still, the lateral angle 82 may be less than the cranial angle 80. Further still, the first and second cranial aperture axes 78 and 86 may diverge outward in the cranial direction at the same angle that they extend in the dorsal direction.

[0037] 5A-5C, the at least one fixation aperture 63 may include at least one caudal fixation aperture extending along a caudal aperture axis. Specifically, the at least one fixation aperture 63 may include a pair of caudal fixation apertures including a first caudal fixation aperture 88 and a second caudal fixation aperture 90. The first and second caudal fixation apertures 88 and 90 may be offset laterally inward (or medially) relative to the first and second cranial fixation apertures 72 and 74. The first caudal fixation aperture 88 may define a first opening or dorsal opening 92a at the dorsal plate end 54 of the plate 34 and a second opening or ventral opening 92b at the ventral plate end 56 of the plate 34. The first caudal fixation aperture 88 may extend along a first caudal aperture axis 94. Thus, the first caudal aperture axis 94 may extend through the center of each of the dorsal opening 92a and the ventral opening 92b. The first caudal aperture axis 94 may be straight and linear.

[0038] 5A, the first caudal fixation aperture 88 may be oriented along a trajectory that flares outward in the caudal direction as the first caudal fixation aperture 88 extends in the dorsal direction. Thus, the first caudal aperture axis 94 may flares outward in the caudal direction as the first caudal aperture axis 94 extends in the dorsal direction. Thus, it should be appreciated that the center of the dorsal opening 92a may be offset in the caudal direction relative to the center of the ventral opening 92b. It should be further appreciated that the first caudal aperture axis 94 may define a caudal angle 96 relative to the reference plane 41 oriented along the lateral direction A and the longitudinal direction L, as viewed from the lateral direction A of the first caudal aperture axis 94 and the reference plane 41. Thus, the angle 96 defines the extent to which the first caudal aperture axis 94 flares in the caudal direction as it extends in the dorsal direction. The angle 96 may be any suitable angle as desired. In one example, angle 96 can be in the range of about 10 degrees to about 60 degrees. For example, angle 96 can be in the range of about 20 degrees to about 55 degrees. In one example, angle 96 can be in the range of about 30 degrees to about 50 degrees. For example, the angle can be about 40 degrees. Thus, caudal angle 96 can be greater than cranial angle 80. For example, caudal angle 96 can be about twice as large as cranial angle 80.

[0039] Additionally, the first caudal aperture axis 94 may space caudally from the caudal side 44 of the spacer 36 as the axis 94 exits the plate 34 and as the axis 94 extends dorsally from the plate 34. Further, the entire first dorsal opening 92a may be offset caudally from the caudal side 44 of the spacer 36. Thus, when the bone screw 60 is inserted through the first caudal fixation aperture 88, the entire bone screw shaft 62, which extends dorsally outward from the first caudal fixation aperture 88, may space caudally from the caudal side 44 of the spacer 36. Further, because the bone screw shaft 62 extends along the first caudal aperture axis 94, the bone screw shaft 62 extends outward in the caudal direction as it extends dorsally.

[0040] 5C, the first caudal aperture axis 94 may further extend laterally outward away from the mid-plane of the spacer 36 as the axis 94 extends in a dorsal direction through the plate 34. In other words, the first caudal aperture axis 94 may further extend laterally inward toward the mid-plane of the spacer 36 as the axis 94 extends in a ventral direction. Additionally, the center of the dorsal opening 92a may be spaced a first distance from the mid-plane 39 along the lateral direction A, and the center of the ventral opening 92b may be spaced a second distance from the mid-plane 39 along the lateral direction A that is less than the first distance. The first caudal aperture axis 94 and the mid-plane 39 may define a caudal lateral angle 97, which may be any suitable angle, as desired. In one example, the angle 97 may range from about 2 degrees to about 20 degrees. For example, the angle 97 may range from about 2 degrees to about 10 degrees. In one particular example, the angle 97 may be about 5 degrees. The first caudal aperture axis 94 may be spaced in a ventral direction from the ventral plate end 56 of the plate 34 and thus intersect the midplane 39 at a location that is outside the footprint of the implant 20. Alternatively, the first caudal aperture axis 94 may extend in a dorsal direction substantially parallel to the midplane 39.

[0041] The second caudal fixation aperture 90 may define a first or dorsal opening 98a at the dorsal plate end 54 of the plate 34 and a second or ventral opening 98b at the ventral plate end 56 of the plate 34. The first and second caudal fixation apertures 88 and 90 extend through the plate 34 from their corresponding dorsal openings to their corresponding ventral openings a distance less than the distance the cranial fixation apertures 72 and 74 extend from their corresponding dorsal openings to their corresponding ventral openings. The second caudal fixation aperture 90 may extend along a second caudal aperture axis 100. Thus, the second caudal aperture axis 100 may extend through the center of each of the dorsal opening 98a and the ventral opening 98b. The second caudal aperture axis 100 may be straight and linear.

[0042] As shown in FIG. 5A, the second caudal fixation aperture 90 may be oriented along a trajectory that flares outward in the caudal direction as the second caudal fixation aperture 90 extends in the dorsal direction. Thus, the second caudal aperture axis 100 may flares outward in the caudal direction as the second caudal aperture axis 100 extends in the dorsal direction. Thus, it should be appreciated that the center of the dorsal opening 98a may be offset in the caudal direction relative to the center of the ventral opening 98b. It should further be appreciated that the second caudal aperture axis 100 may define the caudal angle 96, as discussed above, with respect to the reference plane 41, as viewed from the lateral direction A of the second caudal aperture axis 100 and the reference plane 41.

[0043] Additionally, the second caudal aperture axis 100 may space caudally from the caudal side 44 of the spacer 36 as the axis 100 exits the plate 34 and as the axis 100 extends dorsally from the plate 34. Further, the entire first dorsal opening 98a may be offset caudally from the caudal side 44 of the spacer 36. Thus, when the bone screw 60 is inserted through the second caudal fixation aperture 90, the entire bone screw shaft 62, which extends dorsally outward from the first caudal fixation aperture 90, may space caudally from the caudal side 44 of the spacer 36. Further, because the bone screw shaft 62 extends along the second caudal aperture axis 100, the bone screw shaft 62 extends outward in the caudal direction as it extends dorsally.

[0044] 5C, the second caudal aperture axis 100 may further expand laterally outwardly away from the mid-plane 39 of the spacer 36 as the axis 94 extends dorsally through the plate 34. In other words, the second caudal aperture axis 100 may expand laterally inwardly toward the mid-plane 39 of the spacer 36 as the axis 100 extends ventrally. Thus, the first and second caudal aperture axes 94 and 100 may be inclined opposite the first and second cranial aperture axes 78 and 86, respectively. Thus, the center of the dorsal opening 98a may be spaced a first distance from the mid-plane 39 along the lateral direction A, and the center of the ventral opening 98b may be spaced a second distance from the mid-plane 39 along the lateral direction A that is less than the first distance. The second caudal aperture axis 100 and the mid-plane 39 may define the lateral angle 97 described above. Thus, the second caudal aperture axis 100 may intersect the midplane 39 at a location that is spaced ventrally from the ventral plate end 56 of the plate 34 and thus outside the footprint of the implant 20. Instead, the second caudal aperture axis 100 may extend in a dorsal direction substantially parallel to the midplane 39.

[0045] The first and second caudal fixation apertures 88 and 90 may be spaced substantially equidistant from and positioned on opposite sides of the midplane 39. Furthermore, as the first and second caudal aperture axes 94 and 100 extend along the dorsal direction, the axes 94 and 100 may diverge away from one another at an angle that may be approximately twice the lateral angle 97. Further still, the lateral angle 97 may be less than the caudal angle 96. Further still, the first caudal aperture axis 94 and the second caudal aperture axis 100 may diverge outward in the caudal direction at the same angle as they extend in the dorsal direction.

[0046] Although the plate 34 has been described as including first and second cranial fixation apertures 72 and 74 and first and second caudal fixation apertures 88 and 90, it will be understood that the plate 34 may include any one or more fixation apertures configured to accommodate bone fixation elements 58, such as, for example, one or more bone screws 60, respectively, for securing the intervertebral implant 20 to the adjacent vertebral bodies 28 and 30. The plate 34 may include any number of fixation apertures configured in any number of combinations. For example, the plate 34 may include two, three, four, five or more fixation apertures, preferably for receiving an equal number of bone screws 60. Moreover, the fixation apertures may instead be repeatedly staggered with respect to one another, such that one fixation aperture is angled cranially to define a cranial fixation aperture and an adjacent fixation aperture is angled caudally to define a caudal fixation aperture. Thus, the cranial fixation aperture may be surrounded on both sides by the caudal fixation aperture.Furthermore, the caudal fixation aperture may be surrounded on both sides by the cranial fixation aperture.

[0047] Referring again to FIG. 2A, the intervertebral implant 20 may have any suitable dimensions as desired. For example, the spacer 36 may have a spacer length along the longitudinal direction L from the anterior end 38 to the posterior end 40 ranging from about 12 mm to about 24 mm. The spacer 36 may have a spacer width along the lateral direction L from the first sidewall 43 to the second sidewall 45 ranging from about 4 mm to about 20 mm. For example, the spacer width may range from about 10 mm to about 16 mm. The plate 34 may have a plate length along the longitudinal direction L from the dorsal end 54 to the ventral end 56 ranging from about 3 mm to about 10 mm. In one example, the plate length may be about 6.5 mm.

[0048] 1A-5C , during surgery, plate 34 may be inserted into disc space 32 between adjacent vertebral bodies 28 and 30 such that a cranial portion 55 of a dorsal plate end 54 of plate 34 faces the cranial vertebral body 28 and a caudal portion 57 of the dorsal plate end faces the caudal vertebral body 30. In one example, the cranial portion 55 of the dorsal plate end 54 of plate 34 may abut the cranial vertebral body 28 and the caudal portion 57 of the dorsal plate end may abut the caudal vertebral body 30. The concave-convex shape of the cranial surface of implant 20 may geometrically nest relative to the anatomical shape of the cranial vertebral body 28. The caudal surface of implant 20 may geometrically nest relative to the anatomical shape of the cranial vertebral body 28.

[0049] Next, a plurality of bone screws 60 may be inserted through a respective one of the cranial and caudal fixation apertures 78, 80, 88, and 90. The bone screws 60 inserted into the cranial fixation apertures 72 and 74 may be driven into the cranial vertebral body 28. The respective trajectories of the first cranial aperture axis 78 and the second cranial aperture axis 86 may allow the bone screws 60 to engage with the dense cortical bone of the cranial vertebral body 28. Thus, secure fixation to the cranial vertebral body 28 may be achieved. Similarly, the bone screws 60 inserted into the caudal fixation apertures 88 and 90 may be driven into the caudal vertebral body 30. The respective trajectories of the first caudal aperture axis 94 and the second caudal aperture axis 100 may allow the bone screws 60 to engage with the dense cortical bone of the caudal vertebral body 30. Thus, secure fixation to the cranial vertebral body 30 may be achieved.

[0050] 6A-6D, the intervertebral implant 20 may be constructed as described above, but instead of the window 50 and the ribs 51 and 53, the implant 20 may include a bone graft cavity 102 configured to receive bone graft material that may further fuse the intervertebral implant 20 to the first and second vertebral bodies 28 and 30. Specifically, the bone graft cavity 102 may have a first open end 104 configured to accommodate bone graft material, such as an allograft, an autograft, or the like. The open end 104 may extend through the front end 38 of the spacer 36 along the longitudinal direction L, in one example. It is understood that the open end 104 is not limited to the front end of the spacer 36. For example, the open end 104 may instead extend through one of the first and second side walls 43 and 45, respectively.

[0051] In one example, the bone graft cavity 102 may extend in a posterior direction from the open end 104 to a wall 106 that defines a closed end of the bone graft cavity 102. The wall 106 may be defined by the spacer 36 or, alternatively, may be defined by the plate 34. The cavity 102 may also be partially defined by one or more, or up to all, of the cranial wall, the caudal wall, and one or both of the first and second side walls. For example, the cranial wall may include a cranial lattice structure 108 that defines the cranial end of the bone graft cavity 102. In this regard, it should be understood that the spacer 36 defines a plurality of openings that extend through the cranial wall and are open to the bone graft cavity 102. The openings may be defined by the cranial lattice structure 108 or may be otherwise defined, as desired. The caudal wall may include a caudal lattice structure 110 that defines the caudal end of the bone graft cavity 102. In this regard, it should be understood that the spacer 36 defines a plurality of openings that extend through the caudal wall and are open to the bone graft cavity 102. The openings may be defined by the caudal lattice structure 110 or may be otherwise defined, as desired. The cranial lattice structure 108 and the caudal lattice structure 110 may be spaced apart from one another along the lateral direction T.

[0052] The first sidewall may include first and second lateral lattice structures 112 that respectively define first and second lateral ends of the bone graft cavity 102. As such, the first and second lateral lattice structures 112 may be spaced apart from one another along the lateral direction A. In this regard, it should be understood that the spacer 36 defines a plurality of openings that extend through the first and second sidewalls and are open to the bone graft cavity 102. The openings may be defined by the lateral lattice structures 112 or may be otherwise defined, as desired.

[0053] During surgery, bone graft material can be inserted into the bone graft cavity 102 through the open end 104. Thus, the bone graft material can extend from one or more, up to all, of the openings in the cranial, caudal, and lateral walls. Thus, the bone graft material can extend through the openings in the cranial lattice structure 108 and contact the cranial vertebral body. Similarly, the bone graft material can extend through the openings in the caudal lattice structure 110 and contact the caudal vertebral body. Additionally, the bone graft material can extend through the openings in the first and second lateral lattice structures 112 and fuse with the bone ingrowth growing around the intervertebral implant 20.

[0054] The open end 104 may define any suitable shape as desired. For example, the open end 104 may be defined by a substantially planar caudal surface 105 and a concave surface 107 adjacent opposing ends of the planar caudal surface. The concave surface 107 may include a cranial substantially arcuate surface 109 and a pair of laterally opposed segments 111 that diverge away from each other as they extend from opposing ends of the substantially arcuate surface 109 to opposing ends of the caudal surface 105. The concave surface 107 may be defined by a single curved surface or by multiple surfaces that may include one or more of curved segments and straight segments that are angled relative to each other. The open end 104 may be further defined by an angled lead-in surface. Of course, it should be understood that the open end 104 may have any suitable configuration as desired.

[0055] It should be understood that the foregoing description is only illustrative of the present invention. Various alternatives and modifications may be devised by those skilled in the art without departing from the present invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications, and variations that fall within the scope of the appended claims.

[0056] [Embodiment] (1) An intervertebral implant configured to be implanted within an intervertebral disc space of a quadruped defined by a cranial vertebral body and a caudal vertebral body, comprising: a plate defining a ventral plate end, a dorsal plate end spaced in a dorsal direction opposite the ventral plate end, and a plurality of fixed apertures extending through the plate from the ventral plate end to the dorsal plate end; a spacer extending in the dorsal direction from the plate, the spacer defining a caudal side and a cranial side opposite the caudal side in a cranial direction, the caudal side and the cranial side configured to grasp the caudal vertebral body and the cranial vertebral body, respectively; the cranial surface is convex in a first plane oriented along the dorsal and cranial directions, and the cranial surface is convex in a second plane oriented along the cranial direction and a lateral direction substantially perpendicular to each of the dorsal and cranial directions; The intervertebral implant, wherein the caudal surface is substantially straight and linear in the first plane and the caudal surface is convex in the second plane. (2) The intervertebral implant of embodiment 1, wherein the head surface defines a first radius of curvature in the first plane and a second radius of curvature in the second plane that is greater than the first radius of curvature. (3) The intervertebral implant according to embodiment 1, wherein the first radius of curvature is in the range of about 5 mm to about 20 mm. (4) The intervertebral implant according to embodiment 1, wherein the second radius of curvature is in the range of about 10 mm to about 25 mm. (5) The intervertebral implant of embodiment 1, further comprising a plurality of teeth projecting outwardly from the cranial and caudal surfaces, the teeth defining anterior and posterior surfaces having respective distal ends extending in a ventral direction as they converge to a tip, the ventral direction being opposite the dorsal direction.

[0057] (6) The intervertebral implant of embodiment 1, further comprising a bone graft cavity configured to receive bone graft material to fuse the implant to the cranial and caudal vertebral bodies. (7) The intervertebral implant of embodiment 6, wherein the bone graft cavity has an opening at the anterior end of the spacer. (8) The intervertebral implant of embodiment 1, further comprising a plurality of windows configured to accommodate bone graft material, the windows extending through the spacer from the cranial side to the caudal side. (9) The intervertebral implant of embodiment 1, wherein the plate and the spacer are monolithic with each other. (10) The intervertebral implant of embodiment 1, wherein the dorsal plate end comprises a cranial portion extending outward in the cranial direction relative to the cranial side surface of the spacer, and the dorsal plate end further comprises a caudal portion extending outward in the caudal direction relative to the caudal side surface of the spacer.

[0058] (11) The intervertebral implant of embodiment 10, wherein the implant defines a cranial implant surface defined by the cranial side of the spacer and the cranial portion of the dorsal plate end, the cranial implant surface having a concave-convex shape in the first plane. (12) The intervertebral implant of embodiment 10, wherein the implant defines a caudal recess in the first plane at a caudal interface between the spacer and the plate. (13) The intervertebral implant of embodiment 1, wherein the plurality of fixation apertures comprises a first cranial aperture extending through the plate along a first cranial aperture axis that diverges in the cranial direction as it extends in the dorsal direction, and a first caudal aperture extending through the plate along a first caudal aperture axis that diverges in the caudal direction as it extends in the dorsal direction. (14) The intervertebral implant of embodiment 13, wherein the first cranial aperture axis defines a cranial angle with respect to a reference plane oriented along the lateral direction A and the dorsal direction, and the first caudal aperture axis defines a caudal angle with respect to the reference plane that is greater than the cranial angle. (15) The intervertebral implant according to embodiment 14, wherein the cranial angle is in the range of about 10 degrees to about 30 degrees and the caudal angle is in the range of about 30 degrees to about 50 degrees.

[0059] (16) The intervertebral implant of embodiment 13, wherein the first cranial aperture axis is angled toward the midplane as it extends in the dorsal direction, and the first caudal aperture axis is angled toward the midplane as it extends in a ventral direction opposite the dorsal direction, and the midplane is oriented along the cranial and dorsal directions. (17) The intervertebral implant of embodiment 16, wherein the first cranial aperture axis and the central plane define a cranial lateral angle in the range of about 5 degrees to about 25 degrees. (18) The intervertebral implant of embodiment 16, wherein the first caudal aperture axis and the central plane define a caudal lateral angle in the range of about 2 degrees to about 10 degrees. (19) The intervertebral implant of embodiment 16, comprising a first cranial aperture and a second cranial aperture, and a first caudal aperture and a second caudal aperture disposed between the cranial apertures in the lateral direction. (20) An intervertebral implant system comprising: the intervertebral implant of embodiment 19; and a plurality of screws configured to be inserted through each of the cranial apertures and the caudal apertures and delivered into the cranial and caudal vertebral bodies, respectively.

Claims

[Claim 1] 1. An intervertebral implant configured to be implanted within an intervertebral disc space of a quadruped defined by a cranial vertebral body and a caudal vertebral body, comprising: a plate defining a ventral plate end, a dorsal plate end spaced in a dorsal direction opposite the ventral plate end, and a plurality of fixed apertures extending through the plate from the ventral plate end to the dorsal plate end; a spacer extending in the dorsal direction from the plate, the spacer defining a caudal side and a cranial side opposite the caudal side in a cranial direction, the caudal side and the cranial side configured to grasp the caudal vertebral body and the cranial vertebral body, respectively; the cranial surface is convex in a first plane oriented along the dorsal and cranial directions, and the cranial surface is convex in a second plane oriented along the cranial direction and a lateral direction substantially perpendicular to each of the dorsal and cranial directions; The intervertebral implant, wherein the caudal surface is substantially straight and linear in the first plane and the caudal surface is convex in the second plane.

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