Patent Publication Number: US-2022211514-A1

Title: Expandable intervertebral implant system and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 63/133,989, entitled EXPANDABLE INTERVERTEBRAL IMPLANT SYSTEM AND METHOD, filed on Jan. 5, 2021, which is incorporated by reference as though set forth herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to surgical systems, methods, instruments, and devices. More specifically, the present disclosure relates to improved surgical systems, methods, devices, and instruments for implanting expandable intervertebral implants between adjacent vertebral bodies in a patient. 
     BACKGROUND 
     Spinal fixation procedures utilizing expandable intervertebral implants can be used to correct spinal conditions such as degenerative disc disease, spondylolisthesis, spinal deformities, or other spinal conditions through minimally invasive or invasive spinal surgery. For example, intervertebral discs can degenerate or otherwise become damaged over time. In some instances, an expandable intervertebral implant can be positioned within a space previously occupied by a disc between adjacent vertebral bodies. Such expandable intervertebral implants can help maintain a desired spacing between adjacent vertebrae and/or promote fusion between adjacent vertebrae. The use of bone graft and/or other materials within an area that includes an expandable intervertebral implant can also facilitate the fusion of adjacent vertebral bodies. Accordingly, a need exists for improved expandable intervertebral implants and related surgical instrumentation, tools, systems, and methods. 
     SUMMARY 
     The various apparatus, devices, systems, and/or methods of the present disclosure have been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available technology. One general aspect of the present disclosure can include an upper endplate that may include: a proximal end; a proximal ramp near the proximal end, the proximal ramp may include a pair of upper proximal rails; a distal end; and a distal ramp near the distal end, the distal ramp may include a pair of upper distal rails. The implant may include a lower endplate that may include: a proximal end; a proximal ramp near the proximal end, the proximal ramp may include a pair of lower proximal rails; a distal end; and a distal ramp near the distal end, the distal ramp may include a pair of lower distal rails. 
     The implant may include an actuator assembly positioned between the upper endplate and the lower endplate, the actuator assembly may include: a proximal wedge positioned between the proximal end of the upper endplate and the proximal end of the lower endplate; a distal wedge positioned between the distal end of the upper endplate and the distal end of the lower endplate; and an actuator that engages both the proximal wedge and the distal wedge such that activation of the actuator in a first direction draws both the proximal wedge and the distal wedge toward each other to move the implant to an expanded configuration, and activation of the actuator in a second direction separates both the proximal wedge and the distal wedge from each other to move the implant toward a collapsed configuration. The implant may define a central plane that extends from the proximal end of the upper endplate to the distal end of the upper endplate and from the proximal end of the lower endplate to the distal end of the lower endplate and divides a left side of the expandable intervertebral implant from a right side of the expandable intervertebral implant; and where at least one of the lower distal rails and the lower proximal rails is closer to the central plane than one or more of the upper distal rails and the upper proximal rails. 
     Implementations may include one or more of the following features. The expandable intervertebral implant may include an expansion stop that impedes movement of the implant beyond the expanded configuration. The expansion stop may include threads for a predetermined length, a lack of threads beyond the predetermined length serve as the expansion stop. The expandable intervertebral implant may include a proximal wedge that may include an upper tongue configured to slidably engage a proximal groove of the upper endplate and a lower tongue configured to slidably engage a proximal groove of the lower endplate; and a distal wedge that may include an upper tongue configured to slidably engage a distal groove of the upper endplate and a lower tongue configured to slidably engage a distal groove of the lower endplate; and where the upper tongue of the distal wedge has a different width than the lower tongue of the distal wedge. The upper tongue of the proximal wedge may have a greater width than the lower tongue of the proximal wedge. The upper tongue of the distal wedge may have a greater width than the lower tongue of the distal wedge. 
     The proximal wedge may include a proximal wedge opening and the distal wedge may include a distal wedge opening and the actuator assembly may include: a shank having a head, a distal end, and proximal end, the shank configured to couple the proximal wedge to the distal wedge; and a retainer that secures the shank to one of the proximal wedge and the distal wedge. The retainer may include a protrusion that extends from the shank, the protrusion configured to extend a diameter of the shank such that the protrusion impedes lateral translation of the shank within the proximal wedge opening when the actuator assembly is assembled. The protrusion may include a ring that circumscribes and extends from the shank and the shank may include a groove configured to seat the ring, the groove positioned longitudinally along the shank such that the ring impedes lateral translation of the shank within the proximal wedge opening when the actuator assembly is assembled. The distal wedge may include a barrel, the barrel may include a bore coaxial with the distal wedge opening. The barrel may have a length configured such that the barrel and the distal wedge opening enclose a length of the shank when the implant is in the expanded configuration. The shank may include a single set of external threads configured to engage internal threads of one of the proximal wedge opening and the distal wedge opening. The upper endplate may include a guide tab and the lower endplate may include a pair of fingers configured to slidably engage the guide tab where: the guide tab and the pair of fingers extend from a first side of the expandable intervertebral implant; and a second side of the implant opposite the first side lacks at least one of a guide tab and a pair of fingers. The upper endplate may include a guide tab that extends in an inferior direction and within a perimeter of the upper endplate and the lower endplate may include a pair of fingers that extend in a superior direction and within a perimeter of the lower endplate, the pair of fingers may be configured to slidably engage the guide tab and the guide tab may be configured to sit within a guide tab opening in the lower endplate when the implant is in the collapsed configuration; and the pair of fingers may be configured to sit within finger openings in the upper endplate when the implant is in the collapsed configuration. 
     One general aspect of the present disclosure can include an upper endplate that may include: a proximal end; a proximal ramp near the proximal end, the proximal ramp may include a pair of upper proximal rails; a proximal groove may include an open proximal end and an open distal end; a distal end; a distal ramp near the distal end, the distal ramp may include a pair of upper distal rails; a distal groove may include a closed proximal end and an open distal end; and a guide tab. The implant may include a lower endplate that may include: a proximal end; a proximal ramp near the proximal end, the proximal ramp may include a pair of lower proximal rails; a proximal groove may include an open proximal end and an open distal end; a distal end; a distal ramp near the distal end, the distal ramp may include a pair of lower distal rails; a distal groove may include a closed proximal end and an open distal end; and a pair of fingers configured to slidably engage the guide tab. 
     The implant may include an actuator assembly positioned between the upper endplate and the lower endplate, the actuator assembly may include: a proximal wedge positioned between the proximal end of the upper endplate and the proximal end of the lower endplate and may include an upper tongue configured to slidably engage the proximal groove of the upper endplate and a lower tongue configured to slidably engage the proximal groove of the lower endplate; a distal wedge positioned between the distal end of the upper endplate and the distal end of the lower endplate and may include an upper tongue configured to slidably engage the distal groove of the upper endplate and a lower tongue configured to slidably engage the distal groove of the lower endplate; and an screw member that engages at least one of the proximal wedge and the distal wedge such that rotation of the screw member in a first direction about a longitudinal axis of the screw member draws at least one of the proximal wedge and the distal wedge toward each other to move the implant to an expanded configuration, and rotation of the screw member in a second direction about the longitudinal axis of the screw member separates at least one of the proximal wedge and the distal wedge from each other to move the implant toward a collapsed configuration. 
     Implementations may include one or more of the following features. The proximal wedge of the expandable intervertebral implant may include: a superior face; an inferior face; two opposite lateral faces; a proximal face; a distal face; and the upper tongue of the proximal wedge may extend from superior face, the lower tongue of the proximal wedge may extend from inferior face, and the proximal face may include a proximal wedge opening that extends from the proximal face to the distal face; and the distal wedge may include: a superior face; an inferior face; two opposite lateral faces; a proximal face; a distal face; and the upper tongue of the distal wedge may extend from superior face, the lower tongue of the distal wedge may extend from inferior face, and the proximal face may include a distal wedge opening that extends from the proximal face to the distal face. The expandable intervertebral implant may include an inserter interface that may include a pair of protrusions that extend from each lateral face. 
     One general aspect of the present disclosure can include an expandable intervertebral implant having an upper endplate that may include: a proximal end; a proximal ramp near the proximal end, the proximal ramp may include a pair of upper proximal rails; a proximal groove; a distal end; a distal ramp near the distal end, the distal ramp may include a pair of upper distal rails; and a distal groove. The implant may include a lower endplate that may include: a proximal end; a proximal ramp near the proximal end, the proximal ramp may include a proximal lower ramp face that may include a pair of proximal lower ramp pockets configured to receive the pair of upper proximal rails, the pair of proximal lower ramp pockets may form a pair of lower proximal rails; a proximal groove; a distal end; a distal ramp near the distal end, the distal ramp may include a distal lower ramp face that may include a pair of distal lower ramp pockets configured to receive the pair of upper distal rails, the pair of distal lower ramp pockets may form a pair of lower distal rails; and a distal groove. 
     The implant may include an actuator assembly positioned between the upper endplate and the lower endplate, the actuator assembly may include: a proximal wedge positioned between the proximal end of the upper endplate and the proximal end of the lower endplate and may include an upper tongue configured to slidably engage the proximal groove of the upper endplate and a lower tongue configured to slidably engage the proximal groove of the lower endplate; a distal wedge positioned between the distal end of the upper endplate and the distal end of the lower endplate and may include an upper tongue configured to slidably engage the distal groove of the upper endplate and a lower tongue configured to slidably engage the distal groove of the lower endplate; and an actuator that may include a shank that engages at least one of the proximal wedge and the distal wedge such that rotation of the actuator in a first direction about a longitudinal axis of the shank draws at least one of the proximal wedge and the distal wedge toward each other to move the implant to an expanded configuration, and rotation of the actuator in a second direction about the shank separates at least one of the proximal wedge and the distal wedge from each other to move the implant toward a collapsed configuration. 
     Implementations may include one or more of the following features. The expandable intervertebral implant where at least one of the proximal groove of the upper endplate and the proximal groove of the lower endplate may include an open proximal end and an open distal end. At least one of the distal groove of the upper endplate and the distal groove of the lower endplate may include a closed proximal end and an open distal end. In certain implementations, the proximal wedge may include a recess that extends into each lateral face. Each recess may be configured to seat a protrusion of an inserter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only exemplary embodiments and are, therefore, not to be considered limiting of the scope of the appended claims, the exemplary embodiments of the present disclosure will be described with additional specificity and detail through use of the accompanying drawings. 
         FIG. 1A  is a perspective top view of a proximal end of an expandable intervertebral implant  100 , according to an embodiment of the present disclosure. 
         FIG. 1B  is a perspective top view of a distal end of the expandable intervertebral implant  100  of  FIG. 1A . 
         FIG. 1C  illustrates a first side of the expandable intervertebral implant  100  of  FIG. 1A . 
         FIG. 1D  illustrates a second side of the expandable intervertebral implant  100  of  FIG. 1A . 
         FIG. 1E  illustrates a proximal end view of the expandable intervertebral implant  100  of  FIG. 1A . 
         FIG. 1F  illustrates a distal end view of the expandable intervertebral implant  100  of  FIG. 1A . 
         FIG. 1G  is a top view of the expandable intervertebral implant  100  of  FIG. 1A . 
         FIG. 1H  is a bottom view of the expandable intervertebral implant  100  of  FIG. 1A . 
         FIG. 2A  is a perspective view of a proximal end of the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration. 
         FIG. 2B  is a perspective view of a distal end of the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration. 
         FIG. 2C  is a perspective top view of a distal end of the expandable intervertebral implant of  FIG. 1A  with the upper endplate  110  removed and shown upside down. 
         FIG. 2D  illustrates a side view of the proximal wedge  114 , screw member  118 , and distal wedge  116  of the expandable intervertebral implant  100  of  FIG. 1A . 
         FIG. 2E  illustrates a side view of the screw member  118  of the expandable intervertebral implant  100  of  FIG. 1A ; 
         FIG. 2F  illustrates a first side of the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration. 
         FIG. 2G  illustrates a second side of the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration. 
         FIG. 2H  illustrates a proximal end view of the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration. 
         FIG. 2I  illustrates a distal end view of the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration. 
         FIG. 2J  is a top view of the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration. 
         FIG. 2K  is a bottom view of the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration. 
         FIG. 2L  illustrates a side view of an actuator assembly according to one embodiment. 
         FIG. 3A  is a top view of components of the expandable intervertebral implant  100  of  FIG. 1A  showing the proximal wedge, distal wedge, and screw member in a collapsed configuration. 
         FIG. 3B  is a top view of components of the expandable intervertebral implant  100  of  FIG. 1A  showing the proximal wedge, distal wedge, and screw member in an expanded configuration. 
         FIG. 4A  illustrates an inserter with an expandable intervertebral implant attached. 
         FIG. 4B  illustrates an inserter without an expandable intervertebral implant attached. 
         FIG. 5  is an exploded view of an inserter fork and a driver of the inserter of  FIGS. 4A and 4B . 
         FIGS. 6A-6B  illustrate perspective views of a proximal wedge in accordance with one embodiment. 
         FIGS. 6C-6D  illustrate perspective views of a distal wedge in accordance with one embodiment. 
         FIGS. 6E-6F  illustrate respective anterior view and posterior view of a proximal wedge in accordance with one embodiment. 
         FIGS. 6G-6H  illustrate respective anterior view and posterior view of a distal wedge in accordance with one embodiment. 
         FIGS. 6I-6J  illustrate opposite side views of proximal wedge and a distal wedge in accordance with one embodiment. 
         FIG. 7A  is a perspective top view of a proximal end of a lower endplate and an upper endplate with the upper endplate shown upside down. 
         FIG. 7B  is a perspective top view of a distal end of a lower endplate and an upper endplate with the upper endplate shown upside down. 
         FIG. 7C  is a perspective top view of a proximal end of the expandable intervertebral implant  100  of  FIG. 1A  with the upper endplate  110  removed and shown upside down. 
         FIG. 8A  illustrates a proximal end view of a lower endplate and an upper endplate with the upper endplate shown in an assembled position. 
         FIG. 8B  illustrates a distal end view of a lower endplate and an upper endplate with the upper endplate shown in an assembled position. 
         FIG. 8C  illustrates a perspective view of a central plane, a lower endplate, and an upper endplate with the upper endplate shown in an assembled position. 
     
    
    
     It is to be understood that the drawings are for purposes of illustrating the concepts of the disclosure and may or may not be drawn to scale. Furthermore, the drawings illustrate exemplary embodiments and do not represent limitations to the scope of the present disclosure. 
     DETAILED DESCRIPTION 
     Exemplary embodiments of the present disclosure will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. It will be readily understood that the components of the present disclosure, as generally described and illustrated in the Figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the apparatus and method, as represented in the Figures, is not intended to limit the scope of the present disclosure, as claimed in this or any other application claiming priority to this application, but is merely representative of exemplary embodiments of the present disclosure. 
     Standard medical planes of reference and descriptive terminology are employed in this specification. While these terms are commonly used to refer to the human body, certain terms are applicable to physical objects in general. A standard system of three mutually perpendicular reference planes is employed. A sagittal plane divides a body into right and left portions. A coronal plane divides a body into anterior and posterior portions. A transverse plane divides a body into superior and inferior portions. A mid-sagittal, mid-coronal, or mid-transverse plane divides a body into equal portions, which may be bilaterally symmetric. The intersection of the sagittal and coronal planes defines a superior-inferior or cephalad-caudal axis. The intersection of the sagittal and transverse planes defines an anterior-posterior axis. The intersection of the coronal and transverse planes defines a medial-lateral axis. The superior-inferior or cephalad-caudal axis, the anterior-posterior axis, and the medial-lateral axis are mutually perpendicular. Anterior means toward the front of a body. Posterior means toward the back of a body. Superior or cephalad means toward the head. Inferior or caudal means toward the feet or tail. Medial means toward the midline of a body, particularly toward a plane of bilateral symmetry of the body. Lateral means away from the midline of a body or away from a plane of bilateral symmetry of the body. Axial means toward a central axis of a body. Abaxial means away from a central axis of a body. Ipsilateral means on the same side of the body. Contralateral means on the opposite side of the body. Proximal means toward the trunk of the body. Proximal may also mean toward a user, viewer, or operator. Distal means away from the trunk. Distal may also mean away from a user, viewer, or operator. Dorsal means toward the top of the foot. Plantar means toward the sole of the foot. Antegrade means forward moving from a proximal location/position to a distal location/position or moving in a forward direction. Retrograde means backward moving from a distal location/position to a proximal location/position or moving in a backwards direction. Sagittal refers to a midline of a patient&#39;s anatomy, which divides the body into left or right halves. The sagittal plane may be in the center of the body, splitting it into two halves. 
     The phrases “connected to,” “coupled to” and “in communication with” refer to any form of interaction between two or more entities, including mechanical, electrical, magnetic, electromagnetic, fluid, and thermal interaction. Two components may be functionally coupled to each other even though they are not in direct contact with each other. The term “abutting” refers to items that are in direct physical contact with each other, although the items may not necessarily be attached together. The phrase “fluid communication” refers to two features that are connected such that a fluid within one feature is able to pass into the other feature. 
     The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated. 
     The present disclosure discloses an expandable intervertebral implant, expandable intervertebral implant system, tools, and methods of use. Medical procedures for using expandable intervertebral implants favor an expandable intervertebral implant that is small and compact. For example, minimally invasive or invasive surgery on the spine, such as spinal fusion, may be use a variety of approaches to access the spine, examples include Anterior Lumbar Interbody Fusion (ALIF), Posterior Lumbar Interbody Fusion (PLIF), Transforaminal Lumbar Interbody Fusion (TLIF), or Lateral Interbody Fusion (LIF). For each of these spinal procedures, a smaller implant that can be expanded, as needed, to a desired height, is preferred because the smaller expandable intervertebral implants can cause less disruption of soft tissue and smaller access openings can be used for the procedures. 
     For example, using a smaller expandable intervertebral implant for minimally invasive spine (MIS) surgery techniques can reduce the size of the incisions, sizes of instrumentation used, soft tissue damage, blood loss, post-operative pain, recovery time, risk of surgical complications, and the like. Furthermore, the shape, or profile, of an expandable intervertebral implant can facilitate insertion of the implant during the surgery and provide more stable and secure engagement between the implant and vertebral bodies on either side of a space where the implant is positioned. 
     For example, in one embodiment, the expandable intervertebral implant may have a wedge shaped profile with a narrower part of the wedge on a proximal end of the expandable intervertebral implant and a wider part of the wedge on a distal end of the expandable intervertebral implant. An expandable intervertebral implant with such a wedge-shaped profile can facilitate insertion of the expandable intervertebral implant during a MIS surgical procedure. In addition to the wedge-shaped profile, certain embodiments of the expandable intervertebral implant may include a camber on a top surface and bottom surface of the expandable intervertebral implant to further facilitate placement and positioning of the expandable intervertebral implant between vertebral bodies during the MIS procedure. Of course, one skilled in the art may recognize other situations and advantages of a wedge-shaped profile for an expandable intervertebral implant; this disclosure contemplates all such situations and advantages. 
     Similarly, a narrower expandable intervertebral implant can enable MIS surgery techniques that use a narrower incision and/or narrower cannulas to perform the procedure. A narrower expandable intervertebral implant can facilitate positioning and placement of the implant. In certain circumstances two or more expandable intervertebral implants may be used to provide desired support for vertebral bodies. 
       FIG. 1A  is a perspective view depicting one exemplary embodiment of an expandable intervertebral implant  100 . The expandable intervertebral implant  100  may generally include an upper endplate  110  configured to engage a superior vertebral body (not shown), a lower endplate  112  configured to engage an inferior vertebral body (not shown), a proximal wedge  114 , a distal wedge  116 , and a screw member  118 . 
     The upper endplate  110  may include a proximal end  120 , a distal end  122 , and a guide tab  124 . The proximal end  120  of the upper endplate  110  is an end of the upper endplate  110  closest to a surgeon installing the expandable intervertebral implant  100  between two vertebral bodies. The proximal end  120  of the upper endplate  110  is near an end of the expandable intervertebral implant  100  that removably connects to an insertion tool used to install the expandable intervertebral implant  100 . The proximal end  120  of the upper endplate  110  is near an end of the expandable intervertebral implant  100  that includes the proximal wedge  114 . 
       FIG. 1A  is a perspective top view of the proximal end  120  of the expandable intervertebral implant  100  and  FIG. 1B  is a perspective top view of the distal end  122  of the expandable intervertebral implant  100  of  FIG. 1A . In one embodiment, the distal end  122  of the upper endplate  110  is an end of the upper endplate  110  that first enters the space between two vertebral bodies as a surgeon deploys the expandable intervertebral implant  100 . As used herein, a “deploy” or “deployment” refers to an act, action, process, system, method, means, or apparatus for inserting an implant or prosthesis into a part, body part, and/or patient. “Deploy” or “deployment” can also refer to an act, action, process, system, method, means, or apparatus for placing something into therapeutic use. A device, system, component, medication, drug, compound, or nutrient may be deployed by a human operator, a mechanical device, an automated system, a computer system or program, a robotic system, or the like. 
     In certain embodiments, the distal end  122  of the upper endplate  110  is near an end of the expandable intervertebral implant  100  that includes the distal wedge  116 . In general, the proximal end  130  of the lower endplate  112  may include substantially the same area as the proximal end  120  of the upper endplate  110  and the distal end  132  of the lower endplate  112  may include substantially the same area as the distal end  132  of the upper endplate  110 . 
     In the illustrated embodiment, the guide tab  124  extends from a first side  126  of the upper endplate  110  and a second side  128  lacks a guide tab  124 . In another embodiment, the guide tab  124  may extend from the second side  128 . As used herein, “tab” refers to structure that extends or projects from another larger structure. A tab can be short and wide or long and thin. Typically, a tab is rigid and can include a degree of flexibility. Examples of a tab include a small flap or loop by which something may be grasped or pulled, a long thin projection that extends in one direction, a projection from a card or sheet, or the like. In certain embodiments, a tab can be an appendage or extension to another structure. (search “tab” on Merriam-Webster.com. Merriam-Webster, 2021. Web. 27 Jul. 2021. Modified.) As used herein, a “guide” refers to a part, component, member, or structure designed, adapted, configured, or engineered to guide or direct one or more other parts, components, or structures. A guide may be part of, integrated with, connected to, attachable to, or coupled to, another structure, device, or instrument. In one embodiment, a guide may include a modifier that identifies a particular function, location, orientation, operation, type, and/or a particular structure of the guide. Examples of such modifiers applied to a guide, include, but are not limited to, “pin guide” that guides or directs one or more pins, a “cutting guide” that guides or directs the making or one or more cuts, a “deployment or insertion guide” that guides or directs the deployment, installation, or insertion of a fastener and/or implant, a “cross fixation guide” that guides deployment of a fastener or fixation member, and the like. 
     The guide tab  124  serves to keep the upper endplate  110  aligned vertically with the lower endplate  112 . The guide tab  124  may be configured to slidably engage with the lower endplate  112  (e.g., the lower endplate  112  may include a tongue and groove engagement with the guide tab  124 ). 
       FIG. 1C  illustrates a first side  126  of the expandable intervertebral implant  100  of  FIG. 1A  and  FIG. 1D  illustrates a second side  128  of the expandable intervertebral implant  100  of  FIG. 1A . Referring to  FIG. 1C , the lower endplate  112  can include a proximal end  130 , a distal end  132 , and a pair of fingers  134 . The pair of fingers  134  can be configured to slidably engage the guide tab  124 . In one embodiment, the guide tab  124  and pair of fingers  134  extend from a first side  126  of the expandable intervertebral implant  100 . The second side  128  opposite the first side  126  may lack at least one of a guide tab  124  and/or a pair of fingers  134 . In this manner, the expandable intervertebral implant  100  may have a smaller cross-section and/or profile such that the expandable intervertebral implant  100  can be used in smaller cannula or with other more confined instruments and/or patient access pathways. 
     In the illustrated embodiment, the pair of fingers  134  extends from the first side  126  of the lower endplate  112  and the second side  128  lacks the pair of fingers  134 . The pair of fingers  134  cooperate with the guide tab  124  to keep the upper endplate  110  aligned vertically with the lower endplate  112 . The pair of fingers  134  may be configured to slidably engage with the guide tab  124  of the upper endplate  110 . 
       FIG. 1D  illustrates that the second side  128  lacks the pair of fingers  134  and/or the guide tab  124 .  FIG. 1D  does illustrate an end of the pair of fingers  134  on the first side  126  that can extend beyond a top of the upper endplate  110  and an end of the guide tab  124  on the first side that can extend beyond a bottom of the lower endplate  112 . 
     Referring now to  FIGS. 1C and 1D , in certain embodiments, an exemplary expandable intervertebral implant  100  is configured to form a wedge shape. The wedge shape may be observable when the expandable intervertebral implant  100  is in a collapsed configuration and is viewed in profile. Alternatively, or in addition, wedge shape may be observable when the expandable intervertebral implant  100  is in an expanded configuration and is viewed in profile. As used herein, “wedge shape” refers to a shape that resembles a wedge in which the three dimensional object, when viewed in profile has a first height measured at one end that is greater than a second height measured at an opposite end. 
     The wedge shape of the present disclosure can be seen in  FIGS. 1C and 1D . A first height H 1  measured from a distal end  122  of the upper endplate  110  to a distal end  132  of the lower endplate  112  is greater than a second height H 2  measured from a proximal end  120  of the upper endplate  110  to a proximal end  130  of the lower endplate  112 . In certain embodiments, the surface of one, or both of, the upper endplate  110  and the lower endplate  112  from the distal ends  122 ,  132  to the proximal ends  120 ,  130  can be straight. In other embodiments, such as the embodiment illustrated in  FIGS. 1C, 1D , the surface of one, or both of, the upper endplate  110  and the lower endplate  112  from the distal ends  122 ,  132  to the proximal ends  120 ,  130  can include a camber. 
     Referring now to  FIGS. 1C and 1D , in certain embodiments, an expandable intervertebral implant  100  can include a plurality of ridges  136   a  along a surface of the upper endplate  110  and a plurality of ridges  136   b  along a surface of the lower endplate  112 . The ridges  136   a  along a surface of the upper endplate  110  can serve to engage a superior vertebral body and the ridges  136   b  along a surface of the lower endplate  112  serve to engage an inferior vertebral body. The number of ridges  136   a,b  and/or their positions on the upper endplate  110  and/or lower endplate  112  may vary in certain embodiments of an expandable intervertebral implant  100 . In the illustrated embodiment of  FIGS. 1C and 1D , the ridges  136   a  each point towards the proximal end  120  and the ridges  136   b  each point towards the proximal end  130 . Of course, those of skill in the art recognize that other positions, patterns, placement and spacing of ridges  136   a,b  may be used with the expandable intervertebral implant disclosed herein. 
       FIG. 1E  illustrates a proximal end view of the expandable intervertebral implant  100  of  FIG. 1A  and  FIG. 1F  illustrates a distal end view of the expandable intervertebral implant  100  of  FIG. 1A .  FIG. 1E  illustrates an end view of the proximal wedge  114 , upper endplate  110 , lower endplate  112 , and screw member  118 .  FIG. 1F  illustrates an end view of the distal wedge  116 , upper endplate  110 , lower endplate  112 , and screw member  118 . 
       FIG. 1G  is a top view of the expandable intervertebral implant  100  of  FIG. 1A  and  FIG. 1H  is a bottom view of the expandable intervertebral implant  100  of  FIG. 1A .  FIG. 1G  illustrates that in certain embodiments, the upper endplate  110  can include one or more windows  138 .  FIG. 1H  illustrates that in certain embodiments, the lower endplate  112  can include one or more windows  140 . The windows  138 ,  140  may serve one or more of a variety of purposes. 
     For example, in one embodiment the windows  138 ,  140  may permit bone growth through the expandable intervertebral implant as part of a recovery process after the expandable intervertebral implant is inserted into a patient. In addition, or alternatively, the windows  138 ,  140  may facilitate proper placement and configuration of the expandable intervertebral implant  100  by observation using traditional visualization techniques. 
     A variety of shapes and/or sizes may be used for the windows  138 ,  140 . In the illustrated embodiment, the windows  138 ,  140  may both have a rectangular shape. Other shapes for the windows  138 ,  140  include but are not limited to elliptical, circular, square, and the like. 
       FIGS. 1G and 1H  illustrate an embodiment of the expandable intervertebral implant  100  that defines a central plane  142 . The central plane  142  extends from the proximal end  120  of the upper endplate  110  to the distal end  122  of the upper endplate and from the proximal end  130  of the lower endplate  112  to the distal end  132  of the lower endplate  112 . In certain embodiments, the central plane  142  passes through a longitudinal center of components of the expandable intervertebral implant  100 . The central plane  142  divides the expandable intervertebral implant  100  into two sides, a first side and a second side, also referred to as a left side  144  and a right side  146 . 
       FIGS. 1A-1H  illustrate the expandable intervertebral implant  100  of  FIG. 1A  in a collapsed configuration and  FIGS. 2A-2H  illustrate the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration. As used herein, a “collapsed configuration” refers to an arrangement of an upper endplate  110 , lower endplate  112 , and an actuator assembly (e.g., proximal wedge  114 , distal wedge  116 , and an actuator such as, for example, screw member  118 ) such that the assembly has its smallest height. In certain embodiments, the expandable intervertebral implant  100  is configured such that the upper endplate  110  engages the lower endplate  112  such that the upper endplate  110  is as close as possible to the lower endplate  112  in the collapsed configuration. 
     As used herein, an “expanded configuration” refers to an arrangement of an upper endplate  110 , lower endplate  112 , and an actuator assembly (e.g., proximal wedge  114 , distal wedge  116 , and an actuator such as, for example, screw member  118 ) such that the assembly has its greatest height. In certain embodiments, the expandable intervertebral implant  100  is configured such that the upper endplate  110  engages the lower endplate  112  such that the upper endplate  110  is as far away as possible from the lower endplate  112  in the expanded configuration. As described in more detail below, the expandable intervertebral implant  100  is configured to have any configuration between a collapsed configuration and an expanded configuration. 
       FIG. 2A  is a perspective view of a proximal end of the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration and  FIG. 2B  is a perspective view of the distal end of the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration. 
       FIG. 2A  illustrates that the upper endplate  110  can have a proximal ramp  210  and a proximal groove  212  and that the lower endplate  112  can have a proximal ramp  214  and a proximal groove  216 . The proximal ramps  210 ,  214  can be incline planes configured to engage the proximal wedge  114 . As the expandable intervertebral implant  100  moves from an expanded configuration to a collapsed configuration, the proximal wedge  114  slides along the proximal ramps  210 ,  214 . 
     The proximal groove  212  of the upper endplate  110  can be configured to receive an upper tongue  218  of the proximal wedge  114 . The proximal groove  212  is sized and configured to receive the upper tongue  218 . The upper tongue  218  slides within the proximal groove  212  as the expandable intervertebral implant  100  transitions from a collapsed configuration to an expanded configuration, or vice versa. The proximal groove  216  of the lower endplate  112  can be configured to receive a lower tongue  220  of the proximal wedge  114 . The proximal groove  216  of the lower endplate  112  is sized and configured to receive the lower tongue  220 . The upper tongue  218  slides within the proximal groove  216  of the upper endplate  110  as the expandable intervertebral implant  100  transitions from a collapsed configuration to an expanded configuration, or vice versa. 
       FIG. 2B  illustrates that the lower endplate  112  can have a distal ramp  222  and a distal groove  224  and that the upper endplate  110  can have a distal ramp  226  (See  FIG. 2C ) and a distal groove  228  (See  FIG. 2C ). The distal ramps  222 ,  226  can be incline planes configured to engage the distal wedge  116 . As the expandable intervertebral implant  100  moves from an expanded configuration to a collapsed configuration, the distal wedge  116  slides along the distal ramps  222 ,  226 . 
     Referring to  FIGS. 2B, 2C, and 2D , the distal groove  224  of the lower endplate  112  can be configured to receive a lower tongue  230  of the distal wedge  116 . The distal groove  224  is sized and configured to receive the lower tongue  230 . The lower tongue  230  slides within the distal groove  224  of the lower endplate  112  as the expandable intervertebral implant  100  transitions from a collapsed configuration to an expanded configuration, or vice versa. The distal groove  228  of the upper endplate  110  can be configured to receive an upper tongue  232  of the distal wedge  116 . The distal groove  228  of the upper endplate  110  is sized and configured to receive the upper tongue  232 . The upper tongue  232  slides within the distal groove  228  of the upper endplate  110  as the expandable intervertebral implant  100  transitions from a collapsed configuration to an expanded configuration, or vice versa. 
       FIG. 2D  illustrates the proximal wedge  114 , screw member  118 , and distal wedge  116 . In the illustrated embodiment, the proximal wedge  114  and distal wedge  116  are illustrated relative to the screw member  118  when the expandable intervertebral implant is in an expanded configuration. The distal wedge  116  can include a barrel  234  that includes threads configured to engage with threads on the screw member  118 . 
     As used herein, a “thread” or “screw thread” refers to a helical structure used to convert between rotational and linear movement or force and/or to connect or engage two structures. A screw thread can be a ridge that wraps around a cylinder in the form of a helix, referred to as a straight thread. A screw thread can also be a ridge that wraps around a cone shape, referred to as a tapered thread. A screw thread is a feature of a screw as a simple machine and also in use as a threaded fastener. 
     A screw thread can provide one or both of the following functions: conversion of rotary motion or force into linear motion or force, and preventing or mitigating linear motion or force without corresponding rotation motion or force. In certain implementations of screw threads that convert a rotation force or torque into linear motion, or vice versa, the screw threads may be referred to as drive threads because of the drive function rotating the threads serves to extend or retract a structure linearly. External screw threads are those formed on an external surface of a structure, such as a cylinder or cone shaped structure. Internal screw threads are those formed on an internal wall or surface of a nut, substrate, or opening. 
     The cross-sectional shape of a thread is often called its form or threadform (also spelled thread form). The thread form may be square, triangular, trapezoidal, or other shapes. The terms form and threadform can refer to other design aspects taken together (cross-sectional shape, pitch, and diameters) in addition to cross-sectional shape, but commonly refer to the standardized geometry used by the screw. Major categories of threads include machine threads, material threads, and power threads. Generally, triangular threadforms are based on an isosceles triangle. These threadforms are usually called V-threads or vee-threads because of the shape of the letter V. For 60° V-threads, the isosceles triangle is, more specifically, equilateral. For buttress threads, the triangle is scalene. The theoretical triangle shape for the thread form can be truncated to varying degrees (that is, the tip of the triangle is cut short). A V-thread in which there is no truncation (or a minuscule amount considered negligible) is called a sharp V-thread. Truncation occurs (and is codified in standards) for practical reasons. 
     The mechanical advantage of a screw thread depends on its lead, which is the linear distance the screw travels in one revolution. In general, the lead of a screw thread may be selected so that friction is sufficient to prevent linear motion or force from being converted to rotary, that is so the screw does not slip or disengage even when linear force is applied, as long as no external rotational force is present. A “length of thread engagement” refers to a distance that one set of threads (external or internal) engages another set of one or more threads (external or internal). The tightening of a fastener&#39;s screw thread is comparable to driving a wedge into a gap until the wedge sticks fast through friction and slight elastic deformation. (Search ‘screw thread’ on Wikipedia.com Jul. 16, 2021. Modified. Accessed Aug. 17, 2021.) 
       FIG. 2E  illustrates a side view of the screw member  118  of the expandable intervertebral implant  100  of  FIG. 1A . The screw member  118  may generally include a shank  236 , a head  238 , a neck  239 , and threads  240  on one end of the shank  236 . The screw member  118  may include a groove  242 . In one embodiment, the screw member  118  can be a jackscrew. The groove  242  may be sized and configured to seat a ring  243  or washer (See also  FIG. 3A ). In certain embodiments, the ring  243  sits or seats within a groove  242  (hidden in  FIG. 3A  by ring  243 , see  FIG. 3B  where groove  242  is visible and ring  243  is not shown) when the expandable intervertebral implant  110  is in a collapsed configuration. The ring  243  may comprise a retaining ring. In a collapsed configuration, the ring  243  may keep the screw member  118  positioned within the proximal wedge  114 . Alternatively, or in addition, the ring  243  may serve to prevent the screw member  118  from un-screwing from the distal wedge  116  when the screw member  118  is rotated in a particular direction. The ring  243  can be made of a variety of materials including plastic, rubber, ceramic, metal, or the like. 
     The head  238  can be configured to engage and seat within an opening in the proximal wedge  114  and/or distal wedge  116 . As used herein, an “opening” refers to a gap, a hole, an aperture, a port, a portal, a space or recess in a structure, a void in a structure, or the like. In certain embodiments, an opening can refer to a structure configured specifically for receiving something and/or for allowing access. In certain embodiments, an opening can pass through a structure. In other embodiments, an opening can exist within a structure but not pass through the structure. An opening can be two-dimensional or three-dimensional and can have a variety of geometric shapes and/or cross-sectional shapes, including, but not limited to a rectangle, a square, or other polygon, as well as a circle, an ellipse, an ovoid, or other circular or semi-circular shape. As used herein, the term “opening” can include one or more modifiers that define specific types of “openings” based on the purpose, function, operation, position, or location of the “opening.” As one example, a “fastener opening” refers to an “opening” adapted, configured, designed, or engineered to accept or accommodate a “fastener.” As used herein, a “recess” refers to hollow, void, opening, or depression formed in a surface. In certain embodiments, the recess does not pass through the structure having the surface. A recess can have a variety of cross-section shapes (e.g., ovoid, oval, round, circular, rectangular, square, or the like) and have a variety of configurations for one or more walls that define the recess. In one example, a recess can have one or more walls that connect in rounded corners. In certain embodiments, a recess is sized and shaped to receive or accept another structure. 
     The neck  239  connects the head  238  to the shank  236 . In certain embodiments, the neck  239  is slanted to fit, and/or seat, within a beveled section of an opening in the proximal wedge  114  and/or distal wedge  116 . In certain embodiments, the neck  239  and/or beveled section of an opening may include ratchet ridges that produce an audible sound (e.g., click) as the shank  236  rotates within an opening of the proximal wedge  114  and/or distal wedge  116 . 
     The threads  240  of the shank  236  can be configured to engage with one or more threads, or a lip, within the barrel  234  of the distal wedge  116 . In one embodiment, an opening of the barrel  234  may extend through the distal wedge  116 . The screw member  118  can include a drive recess  244  on one end of the head  238 . The screw member  118  includes a recess  244  configured to receive a drive member, described below. The recess  244  can be configured to have any one of a variety of shapes including slotted, Torx, Torx plus, Philips, Quadrex, Pozidriv, square recess, tri-wing, spanner, or the like. The drive recess  244  can be centered on a longitudinal axis  246  of the screw member  118 . 
     Those of skill in the art will recognize that a variety of designs may be used for the screw member  118 . For example, in one embodiment, the screw member  118  may include no head  238  and instead include threads on both ends of the shank  236 . The threads on opposite ends of the shank may be traverse the shank  236  in opposite directions about the axis  246  such that rotation of the screw member  118  in one direction about the axis  246  draws the proximal wedge  114  and distal wedge  116  together and rotation of the screw member  118  in one direction about the axis  246  moves the proximal wedge  114  and distal wedge  116  away from each other. 
     An actuator embodied as a screw member  118  may include the head  238  at a proximal end  241  and the set of external threads  240  at, or near, the distal end  245 . The screw member  118  may also include a retainer that secures the shank  236  to one, or both, of the proximal wedge  114  and the distal wedge  116 . Advantageously, the retainer keeps the shank  236  coupled to one of the proximal wedge  114  and the distal wedge  116  once the shank  236  is installed within an opening of for example, the proximal wedge  114 . 
     In one embodiment, the retainer may be a protrusion that extends from the shank  236 . As used herein, a “protrusion” refers to a structure or portion of a structure that protrudes or extends from at least one other structure such as a surface of the at least one other structure. Generally, the other structure is connected to, or in contact with, the protrusion. In one embodiment, the protrusion may extend from a portion of a surface of the shank  236 . In another embodiment, the protrusion may circumscribe and/or extend from a surface of the shank  236 . The protrusion is configured to extend a diameter (or at least extend an “effective diameter”) of the shank  236  such that the protrusion impedes lateral translation of the shank  236  within an opening in the proximal wedge  114  when the expandable intervertebral implant  100  is assembled. Examples of suitable protrusions include but are not limited to a pin transverse through the shank  236 , a bump or lip on a surface of the shank  236 , a washer, a nut, or the like. 
     In the illustrated embodiment of  FIG. 2E , the retainer can be a ring  243  that seats within the groove  242  and keeps the proximal end  241  of the shank  236  within the proximal wedge  114 . As used herein, a “retainer” refers to an apparatus, instrument, structure, member, device, component, system, or assembly structured, organized, configured, designed, arranged, or engineered to prevent, limit, impede, stop, or restrict motion or movement of one or more other objects, members, structures, components, parts, apparatuses, systems, or assemblies. 
       FIG. 2F  illustrates a first side of the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration and  FIG. 2G  illustrates a second side of the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration.  FIGS. 2F and 2G  illustrate that the proximal wedge  114  and distal wedge  116  are closer together than in a collapsed configuration as illustrated in  FIGS. 1C and 1D . In the collapsed configuration, shown in  FIGS. 1C and 1D , the proximal wedge  114  is closer to the proximal ends  120 ,  130  and distal wedge  116  is closer to the distal ends  122 ,  132 . In the expanded configuration, shown in  FIGS. 2F and 2G , the proximal wedge  114  is closer to the distal wedge  116  and further from the proximal ends  120 ,  130  and distal wedge  116  is closer to the proximal wedge  114  and further from the distal ends  122 ,  132 . 
     Rotating the screw member  118  about the axis  246  in a first direction  248  (See  FIG. 2H ) draws the proximal wedge  114  up the ramps  210 ,  222  and the distal wedge  116  up the ramps  222 ,  226 . Rotating the screw member  118  about the axis  246  in a second direction  250  (See  FIG. 2H ) drives the proximal wedge  114  down the ramps  210 ,  222  and the distal wedge  116  down the ramps  222 ,  226 . Movement of the proximal wedge  114  up the ramps  210 ,  222  causes the upper endplate  110  to move vertically relative to the lower endplate  112  and to separate from the lower endplate  112 . Movement of the distal wedge  116  up the ramps  222 , 226  causes the upper endplate  110  to move vertically relative to the lower endplate  112  and to separate from the lower endplate  112 . 
     Conversely, movement of the proximal wedge  114  down the ramps  210 ,  222  causes the upper endplate  110  to move vertically relative to the lower endplate  112  and to move vertically closer to the lower endplate  112 . Movement of the distal wedge  116  down the ramps  222 , 226  causes the upper endplate  110  to move vertically relative to the lower endplate  112  and to move vertically closer to the lower endplate  112 . 
     In certain embodiments, the proximal wedge  114 , distal wedge  116 , proximal ramp  214  and/or distal ramp  222  are configured such that the upper endplate  110  move vertically uniformly relative to the lower endplate  112 . Consequently, a ratio of the first height H 1  to the second height H 2  (See  FIG. 1C, 1D ) remains the substantially the same as the exemplary expandable intervertebral implant  100  transitions from a collapsed configuration to a partially expanded configuration or expanded configuration. In other words, where H 1  is greater than H 2  in a collapsed configuration, H 1  continues to be greater than H 2  in a partially expanded configuration or expanded configuration. 
     By way of example, angles between the ramps  214 ,  222  and wedges  114 ,  116  can be selected such that the upper endplate  110  moves uniformly vertically relative to the lower endplate  112 . In another embodiment, the ramps  214 ,  222 , wedges  114 ,  116 , and/or angles between them are configured such that a ratio of the first height H 1  to the second height H 2  (See  FIG. 1C, 1D ) changes as the exemplary expandable intervertebral implant  100  transitions from a collapsed configuration to a partially expanded configuration or expanded configuration. For example, in an expanded configuration H 1  and H 2  can be substantially the same. 
       FIG. 2H  illustrates a proximal end view of the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration and  FIG. 2I  illustrates a distal end view of the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration. Arrow  248  illustrates a first direction for rotation of the screw member  118  about the axis  246  and arrow  250  illustrates a second direction for rotation of the screw member  118  about the axis  246 . 
       FIG. 2J  is a top view of the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration and  FIG. 2K  is a bottom view of the expandable intervertebral implant  100  of  FIG. 1A  in an expanded configuration.  FIGS. 2J and 2K  are comparable to  FIGS. 1G and 1H . In  FIGS. 1G and 1H , the proximal wedge  114  and distal wedge  116  can be seen because the expandable intervertebral implant is in a collapsed configuration. In  FIGS. 2J and 2K , the proximal wedge  114  and distal wedge  116  cannot be seen because the expandable intervertebral implant is in an expanded configuration. Also,  FIGS. 1G and 1H  illustrate threads  240  of the screw member  118  because the expandable intervertebral implant is in a collapsed configuration.  FIGS. 2J and 2K  do not illustrate threads  240  of the screw member  118  because the expandable intervertebral implant is in an expanded configuration (the threads are hidden by the barrel  234 ). 
       FIG. 2L  illustrates a side view of an actuator assembly  252  according to one embodiment. In one embodiment, the actuator assembly  252  is positioned between the upper endplate and the lower endplate, when the expandable intervertebral implant  100  is assembled. An actuator assembly serves to move one or more parts, components, or structures to accomplish a desired function. In certain embodiments, the actuator assembly  252  serves to transition the relationship of the upper endplate  110  and lower endplate  112  from a collapsed configuration to an expanded configuration and any configuration in between these. As used herein, “actuator” refers to a component of a machine that is responsible for moving and/or controlling a component, structure, lever, mechanism, or system. (Search “actuator” on Wikipedia.com Nov. 15, 2021. CC-BY-SA 3.0 Modified. Accessed Dec. 28, 2021.) As used herein, an “assembly” refers to a collection, set, or kit of two or more structures, components, parts, systems, and/or sub-systems that together may be used, connected, coupled, applied, integrated, or adapted to be used to perform one or more functions and/or features. An assembly may include a modifier that identifies one or more particular functions or operations that can be accomplished using the assembly. Examples of such modifiers applied to an assembly, include, but are not limited to, “measurement assembly,” “correction assembly,” “fixation assembly,” “separation assembly,” “cutting assembly,” and the like. 
     In the illustrated embodiment, the actuator assembly  252  includes a proximal wedge  254 , a distal wedge  256 , and an actuator  258 . The proximal wedge  254  may be configured to be positioned between the proximal end  120  of an upper endplate  110  and the proximal end  130  of the lower endplate  112 . The distal wedge  256  may be configured to be positioned between the distal end  122  of an upper endplate  110  and the distal end  132  of the lower endplate  112 . In certain embodiments, the proximal wedge  254  may include an upper tongue  280  configured to slidably engage a proximal groove of the upper endplate  110  and a lower tongue  282  configured to slidably engage a proximal groove of the lower endplate  112 . The distal wedge  256  may include an upper tongue  284  configured to slidably engage a distal groove of the upper endplate  110  and a lower tongue  286  configured to slidably engage a distal groove of the lower endplate  112 . In certain embodiments, the upper tongue  280 , lower tongue  282 , upper tongue  284 , and lower tongue  286  may correspond to like named and numbered tongues illustrated in other embodiments described herein. 
     While the illustrated embodiments may include a proximal wedge  254  and distal wedge  256  with one or more tongues that engage one or more grooves of the upper endplate  110  and/or lower endplate  112 . Those of skill in the art will appreciate that other forms of structural engagement may be used between the endplates  110 ,  112  and/or the wedges  254 ,  256 . Similarly, the endplates  110 ,  112  may include tongues, while the wedges  254 ,  256  may include grooves. 
     The actuator serves to cause one or the other or both of the distal wedge  256  and/or proximal wedge  254  to move in order to change the configuration of expandable intervertebral implant  100  from collapsed to expanded or vice versa. Those of skill in the art appreciate that an actuator may be implemented in a variety of forms and configurations. In the illustrated embodiment, the actuator  258  is configured to engage both the proximal wedge  254  and the distal wedge  256  such that activation of the actuator  258  in a first direction draws both the proximal wedge  254  and the distal wedge  256  toward each other to move the implant  100  to an expanded configuration, and activation of the actuator  258  in a second direction separates both the proximal wedge  254  and the distal wedge  256  from each other to move the implant  100  toward a collapsed configuration. 
     In certain embodiments, the actuator may be embodied, in one example, as a screw member  118  in accordance with embodiments described herein. Alternatively, or in addition, the actuator may be implemented by a variety of other designs for mechanisms that can move the proximal wedge  254  and/or distal wedge  256  relative to each other to collapse or expand the upper endplate  110  and/or lower endplate  112  relative to each other. 
     In embodiments where the actuator  258  is implemented using a screw member  118 , rotation of the screw member  118  in a first direction about a longitudinal axis of the screw member  118  draws at least one of the proximal wedge  254  and the distal wedge  256  toward each other to move the implant  100  to an expanded configuration. Further, rotation of the screw member  118  in a second direction about the longitudinal axis of the screw member  118  separates at least one of the proximal wedge  254  and the distal wedge  256  from each other to move the implant  100  toward a collapsed configuration. 
     In the illustrated embodiment, the actuator  258  can be a shank with a proximal end and a distal end. The shank can engage at least one of the proximal wedge  254  and the distal wedge  256  such that rotation of the actuator  258  in a first direction about a longitudinal axis of the shank draws at least one of the proximal wedge  254  and the distal wedge  256  toward each other to move the implant  100  to an expanded configuration. Rotation of the actuator  258  in a second direction about the shank separates at least one of the proximal wedge  254  and the distal wedge  256  from each other to move the implant  100  toward a collapsed configuration. 
     The actuator  258  may also include a head at the proximal end and set of external threads at, or near, the distal end. The actuator  258  may also include a retainer  288  that secures the shank to one or both of the proximal wedge  254  and the distal wedge  256 . In the illustrated embodiment of  FIG. 2L , the retainer  288  can be a ring  243  that keeps the proximal end of the shank within the proximal wedge  254 . 
       FIG. 3A  is a top view of disassembled components of the expandable intervertebral implant  100  of  FIG. 1A . Specifically,  FIG. 3A  illustrates the upper endplate  110  and lower endplate  112  disassembled from the expandable intervertebral implant  100 .  FIG. 3A  also illustrates the proximal wedge  114 , distal wedge  116 , and a screw member  118  and their positions relative to each other when the expandable intervertebral implant  100  is in a collapsed configuration. 
     The upper endplate  110  can include a guide tab  124  and one or more finger openings  260 . The lower endplate  112  can include a pair of fingers  134  and one or more guide tab openings  262 . The guide tab  124  can extend in an inferior direction and within a perimeter  264  of the upper endplate  110 . The lower endplate  112  can include a pair of fingers  134  that extend in a superior direction and within a perimeter  266  of the lower endplate  112 . The pair of fingers  134  can be configured to slidably engage the guide tab  124 . In one embodiment, the guide tab  126  is configured to sit within a guide tab opening  262  in the lower endplate  112  when the implant  100  is in the collapsed configuration. Alternatively, or in addition, the pair of fingers  134  can be configured to sit within the finger openings  262  in the upper endplate  110  when the implant  100  is in the collapsed configuration. 
       FIG. 3B  is a top view of disassembled components of the expandable intervertebral implant  100  of  FIG. 1A . Specifically,  FIG. 3B  illustrates the upper endplate  110  and lower endplate  112  disassembled from the expandable intervertebral implant  100 .  FIG. 3A  also illustrates the proximal wedge  114 , distal wedge  116 , and screw member  118  and their positions relative to each other when the expandable intervertebral implant  100  is in an expanded configuration.  FIG. 3B  illustrates that the proximal wedge  114  and distal wedge  116  are closer to each other along the screw member  118  (note, in the depicted embodiment, the threads  240  are no longer visible being concealed by the barrel  234  and the distal wedge  116 ). 
     Referring now to  FIGS. 3A and 3B , the expandable intervertebral implant  100 , in certain embodiments, may include an expansion stop that impedes movement of the expandable intervertebral implant  100  beyond an expanded configuration. As used herein, a “stop” refers to an apparatus, instrument, structure, member, device, component, system, or assembly structured, organized, configured, designed, arranged, or engineered to prevent, limit, impede, stop, or restrict motion or movement and/or operation of the another object, member, structure, component, part, apparatus, system, or assembly. An expansion stop  268  can be useful to prevent a user from expanding the expandable intervertebral implant  100  too far which may cause components of the expandable intervertebral implant  100  to break, become misaligned, or otherwise unusable. 
     Those of skill in the art appreciate that an expansion stop  268  may be implemented in a variety of ways. In the illustrated embodiment, the expansion stop  268  includes a predetermined configuration for threads  240  of an actuator, such as for example screw member  118 , and an unthreaded portion of the actuator (e.g., screw member  118 ). For example, the threads  240  may extend along a shank of the actuator for a predetermined length  270 . The predetermined length  270  may be designed such that once a wedge, such as distal wedge  116 , travels the predetermined length  270  along the shank the expandable intervertebral implant  100  has reached is designed expansion configuration. Consequently, when the distal wedge  116 , reaches the end of the threads  240  the distal wedge  116  may not be able to travel closer to the proximal wedge  114  to transition to an expanded configuration. Thus, the lack of threads  240  beyond the predetermined length  270  serves as an expansion stop  268 . 
     Alternatively, or in addition, an expansion stop  268  can be implemented by the length of the barrel  234 . The barrel  234  may be long enough that the barrel  234  abuts the ring  243  and/or proximal wedge  114  and thereby serves as an expansion stop  268 . Alternatively, or in addition, an expansion stop  268  can be implemented by a pin or protrusion along a shank of an actuator, such as screw member  118 , that contacts the barrel  234  and prevents further translation of the distal wedge  116  towards the proximal wedge  114 . 
       FIG. 3A  illustrates the components of one embodiment of an expandable intervertebral implant with the expandable intervertebral implant in a collapsed configuration.  FIG. 3B  illustrates the components of one embodiment of an expandable intervertebral implant with the expandable intervertebral implant in an expanded configuration. Comparing the two figures illustrates that the upper endplate  110  and lower endplate  112  remain in approximately the same position in either configuration. 
     A comparison of  FIGS. 3A and 3B  in relation to one example of an actuator assembly  252  illustrates differences between the collapsed configuration and the expanded configuration and an additional feature of the disclosed solution. Specifically, in certain embodiments, the barrel  234  has a length extending distally such that the barrel  234  and the distal wedge  116  (e.g., an opening within the distal wedge  116 ) enclose a length of the shank  236  when the expandable intervertebral implant  100  is in the expanded configuration. (See  FIG. 3B ). For example, in one embodiment, a length of the barrel  234  may be about half a length of the shank  236  and/or may be about half a length of the threads  240  of the shank  236 . Enclosing the shank  236  and/or threads  240  of the shank  236  may be advantageous where the expandable intervertebral implant  100  is implanted between two vertebral bodies and new bone has grown between the two vertebral bodies and grown through and/or around the expandable intervertebral implant  100  (e.g., via the window  138  and/or window  140 ). If the expandable intervertebral implant  100  is deployed in an expanded or partially expanded configuration, enclosing the shank  236  and/or threads  240  of the shank  236  may facilitate collapsing the installed expandable intervertebral implant  100  for example as part of a revision procedure. 
     In certain embodiments, the shank  236  is configured to have only one set of threads  240 . The single set of threads  240  may extend from an external surface of the shank  236  and serve as a single set of external threads  240  that engage internal threads of the distal wedge  116 . A single set of threads  240  may be advantageous as using a single set can reduce the manufacturing complexity, reduce time for quality control checks, simplify the operation of the expandable intervertebral implant  100 , and provide other benefits. 
       FIG. 4A  illustrates one exemplary embodiment of an inserter  400  with an expandable intervertebral implant attached. In one embodiment, the expandable intervertebral implant attached to the inserter  400  can be the expandable intervertebral implant  100  illustrated in  FIG. 1 . The inserter  400  may generally include an inserter body  410 , a handle  420 , an inserter fork  430 , a driver  440 , and a knob  450 . 
     The inserter body  410  may serve as a housing for the inserter fork  430 . The inserter body  410  can include a stock  412  and an arm  414 . The stock  412  can be configured to engage with the handle  420 . In one exemplary embodiment, the stock  412  is a cylindrical member with threads (not shown) around the outside on one end of the stock  412 . The threads of the stock  412  can engage internal threads in an opening (not shown) in the handle  420  such that screwing the handle onto the threads of the stock  412  secures the handle  420  to the stock  412 . 
     The arm  414  can include an internal longitudinal opening that is sized and configured to contain the inserter fork  430  and the driver  440 . The arm  414  is a rigid member of a length that enables a user to comfortably position an attached expandable intervertebral implant during an intervertebral procedure. In certain embodiments, the arm  414  can includes one or more windows  416 . 
     The handle  420  is sized and configured to fit comfortably in the hand(s) of a user such as a surgeon. By holding the handle  420 , a user is able to guide, position, and direct the inserter  400  attached to an expandable intervertebral implant during a procedure to install an expandable intervertebral implant, such as the expandable intervertebral implant  100 . 
     The inserter fork  430  is an elongated member coupled to the knob  450  which is secured within the inserter body  410 . The inserter fork  430  and knob  450  cooperate with the inserter body  410  to engage and disengage with an expandable intervertebral implant. 
     In certain embodiments, the inserter fork  430  has a length that extends beyond both ends of the arm  414 . The inserter fork  430  can slidably move within the arm  414  to assume a retracted position and an extended position. In the retracted position, the inserter fork  430  engages the expandable intervertebral implant and minimally extends beyond a distal end of the arm  414 . In the extended position, the inserter fork  430  disengages from the expandable intervertebral implant and extends further beyond a distal end of the arm  414  than when the inserter fork  430  is in the retracted position. 
     The knob  450  is connected to the inserter body  410  and coupled to the inserter fork  430 . In one embodiment, the inserter fork  430  is coupled to the knob  450  such that as the knob  450  is rotated about the longitudinal axis  460  in a first direction, the inserter fork  430  extends beyond a distal end of the arm  414  towards the extended position. Similarly, as the knob  450  is rotated about the longitudinal axis  460  in a second direction, the inserter fork  430  retracts within the arm  414  towards the retracted position. In one embodiment, the knob  450  can include a central opening with internal threads (not shown) that engage external threads (see  FIG. 5 ) one an outside of the inserter fork  430 . 
       FIG. 4B  illustrates an inserter  400  without an expandable intervertebral implant attached.  FIG. 4B  illustrates more details of one embodiment of the inserter fork  430 . 
       FIG. 5  is an exploded view of an inserter fork  430 , a knob  450 , and a driver  440 . In an exemplary embodiment, the inserter fork  430  can include a body  510 , a pair of prongs  520 , a longitudinal opening  530 , a bias member  540 , and a set of threads  550 .  FIG. 5  also includes a perspective view of a proximal wedge  114  and screw member  118 . 
     The body  510  is an elongated member that can be cylindrical or can have a rectangular cross section. The body  510  includes a longitudinal opening  530  that extends from one end of the body  510  to the other. The longitudinal opening  530  is configured to receive at least part of the driver  440 . The longitudinal opening  530  can have a central axis that is coaxial with the longitudinal axis  460 . The body  510  can include one or more windows  512  that connect to the longitudinal opening  530 . The windows  512  can facilitate cleaning and sterilizing of the inserter  400 . 
     In one exemplary embodiment, the body  510  includes a bias member  540  positioned at one end of the body  510  and coupled to the pair of prongs  520 . In one embodiment, the bias member  540  is formed as part of the body  510 . In the illustrated exemplary embodiment, the bias member  540  can include two legs  542  of the body  510  formed to naturally extend out away from the longitudinal axis  460 , with an opening  544  between the legs  542 . 
     In the illustrated exemplary embodiment, the pair of prongs  520  are configured to engage with an expandable intervertebral implant. In particular, the pair of prongs  520  can each include a protrusion  522  that extends towards the longitudinal axis  460 . Each protrusion  522  is configured to seat within one recess  524  of a proximal wedge  114 . In addition, the prongs  520  can include shoulders  526  configured to contact protrusions  528  of the proximal wedge  114  when the inserter fork  430  is connected to an expandable intervertebral implant. 
     The knob  450  can have a circular cross section and includes an opening that is coaxial with the longitudinal axis  460 . The opening of the knob  450  can be configured to engage external threads  550  along one section of the body  510  of the inserter fork  430 . As illustrated in  FIG. 4 , the knob  450  sits within an opening on the inserter body  410  of the inserter  400 . Accordingly, rotation of the knob  450  about the longitudinal axis  460  in one direction draws the inserter fork  430  into the inserter body  410  and rotation of the knob  450  about the longitudinal axis  460  in an opposite direction extends the inserter fork  430  out of the inserter body  410 . 
     In certain embodiments, the inserter fork  430  can be splayed prior to assembly (for example by way of the bias member  540 ) and insertion of the inserter fork  430  within the arm  414 . Thus, assembling the inserter fork  430  within the arm  414  brings the prongs  520  closer together and movement of the inserter fork  430  to an extended position results in the prongs  520  moving further apart, which can release an attached expandable intervertebral implant  100 . 
     The driver  440  includes a driver handle  560 , a shaft  570 , and a drive member  580 . In an exemplary embodiment, the driver handle  560  can be connected to, or coupled to, the shaft  570 . The driver handle  560  enables a user of the inserter  400  to rotate the shaft  570  and drive member  580  during a surgical procedure. The driver handle  560  has a circular cross section and is sized for convenient rotation in either direction about the longitudinal axis  460 . 
     The shaft  570  can be a solid piece of material that connects the driver handle  560  and the drive member  580 . The shaft  570  can have a circular cross section and is sized to fit within the longitudinal opening  530 . 
     The drive member  580  is configured to engage a drive recess  244  (See  FIG. 2H ) of a screw member  118 . Accordingly, the drive member  580  is configured to have a shape and configuration that matches the type of drive recess  244  of the screw member  118 . Depending on the type of recess  244 , the drive member  580  has a corresponding type and shape such as a slot to fit a slotted recess  244 , a torx end to fit a torx recess  244 , a Philips end to fit a Philips recess  244 , and the like. Of course, those of skill in the art recognize that the shape and configuration of the drive member  580  and the recess  244  can be reversed and thus comprise an embodiment within the scope of the present disclosure. The drive member  580  is configured to connect to the shaft  570  and fit within the inserter fork  430  such that the drive member  580  seats within the drive recess  244  when the expandable intervertebral implant is attached to the inserter  400 . 
       FIG. 5  illustrates in the exploded view that the driver  440  is configured to fit within the longitudinal opening  530  of the inserter fork  430 . When installed within the inserter fork  430 , the shaft  570  is long enough that the driver handle  560  remains outside the longitudinal opening  530  and the drive member  580  sits between the protrusions  522 . With the protrusions  522  seated within the recesses  524  of the proximal wedge  114  of an attached expandable intervertebral implant, the expandable intervertebral implant is securely attached to the inserter  400 . 
     During a procedure, when a user rotates the driver handle  560  the drive member  580  rotates the screw member  118  to expand or collapse the expandable intervertebral implant. As the driver handle  560  rotates about the longitudinal axis  460 , the shoulders  526  cooperate with the protrusions  528  to retain the proximal wedge  114  such that the screw member  118  rotates but the proximal wedge  114  and expandable intervertebral implant do not rotate. 
     Referring now to  FIGS. 4A, 4B, and 5 , examples of using the inserter  400  are described. With an expandable intervertebral implant  100  attached to the inserter  400 , the knob  450  engages threads  550  of the inserter fork  430  such that the prongs  520  are retracted within the arm  414 . In such a configuration, the legs  542  of the bias member  540  are biased against internal walls of the arm  414 . A user can then take the inserter  400  by the handle  420  and position the expandable intervertebral implant between vertebral bodies for the procedure. Once, the expandable intervertebral implant  100  is positioned, a user can rotate the driver  440  which rotates the screw member  118  which expands the expandable intervertebral implant from a collapsed configuration to either a partially expanded configuration or a fully expanded configuration. 
     Once the user confirms that the expandable intervertebral implant is properly positioned and expanded, the user can rotate the knob  450  to extend the inserter fork  430 . Extending the inserter fork  430  causes the bias member  540  to move the protrusions  522  out of the recesses  524  and thereby detach the expandable intervertebral implant  100  from the inserter  400 . If needed, the process can be reversed to retrieve an expandable intervertebral implant  100  using the inserter  400 . 
       FIGS. 6A-6B  illustrate perspective views of a proximal wedge in accordance with one embodiment. The proximal wedge  114  can have six sides: a superior face  602 , an inferior face  604 , two opposite lateral faces  606 ,  608 , a proximal face  610 , and a distal face  612 . In the illustrated embodiment, the proximal wedge  114  has a generally wedge shape with a distance between the superior face  602  and inferior face  604  being shorter as the distance is measured closer towards to the distal face  612 . One or more faces of the proximal wedge  114  may include features. For example, an upper tongue, such as upper tongue  218 , may extend from the superior face  602 ; a lower tongue, such as lower tongue  220 , may extend from the inferior face  604 ; and the proximal face  610  may include a proximal wedge opening  614  that extends from the proximal face  610  to the distal face  612 . 
     The upper tongue  218  and lower tongue  220  may have a variety of configurations. In the illustrated embodiment, the upper tongue  218  has a planar superior surface and lateral surfaces that have an “S” shaped cross-section. In the illustrated embodiment, the lower tongue  220  has a planar superior surface and lateral surfaces that have an “5” shaped cross-section. Those of skill in the art appreciate that the form and shape of the cross-section of the upper tongue  218  and/or lower tongue  220  can have many forms as long as the form and shape of the cross-section of the upper tongue  218  and/or lower tongue  220  is compatible with the cross-sectional shape of an upper groove and/or lower groove that receives the upper tongue  218  and/or lower tongue  220 . In certain embodiments, the proximal wedge opening  614  can include a beveled edge  615  configured to contact a ring  243  when an actuator is assembled within the proximal wedge opening  614 . The proximal wedge opening  614  may have a diameter sized to accept passage of a shank  236  of an actuator therethrough and a diameter sized to prevent passage of a head  238  of an actuator therethrough. 
     In one embodiment, the proximal wedge  114  includes an inserter interface  615 . The inserter interface  615  can include features of the lateral face  606  and/or lateral face  608 . In one embodiment, the inserter interface  615  includes a pair of protrusions  528  that extend from the lateral face  606  and/or lateral face  608 . The pair of protrusions  528  may cooperate with shoulders  526  of an inserter  400 . The inserter interface  615  can include a recess  524  formed in each lateral face  606 ,  608 . A recess  524  may extend into each lateral face  606 , 608 . The recess  524  may accept one or more protrusions  522  from an inserter  400 . Each recess  524  may be configured to seat a protrusion  528  of an inserter  400 . 
     As used herein, an “interface” refers to an area, a boundary, or a place at which two separate and/or independent structures, members, apparatus, assemblies, components, and/or systems join, connect, are coupled, or meet and act on, or communicate, mechanically or electronically, with each other. In certain embodiments, “interface” may refer to a surface forming a common boundary of two bodies, spaces, structures, members, apparatus, assemblies, components, or phases. (search “interface” on Merriam-Webster.com. Merriam-Webster, 2021. Web. 15 Nov. 2021. Modified.) In certain embodiments, the term interface may be used with an adjective that identifies a type or function for the interface. For example, an engagement interface may refer to one or more structures that interact or connect to mechanically join or connect two separate structures, each connected to a side of the interface. 
       FIGS. 6C-6D  illustrate perspective views of a distal wedge in accordance with one embodiment. The distal wedge  116  can have six sides: a superior face  616 , an inferior face  618 , two opposite lateral faces  620 ,  622 , a proximal face  624 , and a distal face  626 . In one embodiment, the proximal face  624  may have a convex surface. In the illustrated embodiment, the distal wedge  116  has a generally wedge shape with a distance between the superior face  616  and inferior face  618  being shorter as the distance is measured closer towards to the distal face  626 . One or more faces of the distal wedge  116  may include features. For example, an upper tongue, such as upper tongue  232 , may extend from the superior face  616 ; a lower tongue, such as lower tongue  230 , may extend from the inferior face  618 ; and the proximal face  624  may include a distal wedge opening  628  that extends from the proximal face  624  to the distal face  626 . In certain embodiments, the distal wedge opening  628  may be sized to have the same diameter as the proximal wedge opening  614 . In other embodiments, the distal wedge opening  628  and the proximal wedge opening  614  may each have a different diameter. 
     The upper tongue  232  and lower tongue  230  may have a variety of configurations. In the illustrated embodiment, the upper tongue  232  has a planar superior surface and lateral surfaces that have an “S” shaped cross-section, for at least part of the lateral surface. In the illustrated embodiment, the lower tongue  230  has a planar superior surface and lateral surfaces that have an “S” shaped cross-section, for at least part of the lateral surface. Those of skill in the art appreciate that the form and shape of the cross-section of the upper tongue  232  and/or lower tongue  230  can have many forms as long as the form and shape of the cross-section of the upper tongue  232  and/or lower tongue  230  is compatible with the cross-sectional shape of an upper groove and/or a lower groove that receives the upper tongue  232  and/or lower tongue  230 . 
     In certain embodiments, the distal wedge  116  includes a barrel  234  that extends from the distal face  626 . The barrel  234  may include a bore  235  that is coaxial with the distal wedge opening  628 . The bore  235  may include internal threads configured to engage with external threads  240 . 
       FIGS. 6E-6F  illustrate respective anterior view and posterior view of a proximal wedge  114  in accordance with one embodiment. In the illustrated embodiment, the upper tongue  218  has a different width (W 1 ) than a width (W 2 ) of the lower tongue  220 . Having different widths may enable a desired level of stability as the expandable intervertebral implant  100  is deployed within a patient. Alternatively, or in addition, having different widths W 1 , W 2  may facilitate the expansion of the expandable intervertebral implant  100  from a collapsed configuration to an expanded configuration. In another embodiment, the widths W 1 , W 2  may be the same. In the illustrated embodiment, the upper tongue  218  has a greater width than the lower tongue  220  of the proximal wedge  114 . In another embodiment, the lower tongue  220  has a greater width than the upper tongue  218  of the proximal wedge  114 . 
       FIGS. 6G-6H  illustrate respective anterior view and posterior view of a distal wedge  116  in accordance with one embodiment. In the illustrated embodiment, the upper tongue  232  has a different width (W 3 ) than a width (W 4 ) of the lower tongue  230 . Having different widths may enable a desired level of stability as the expandable intervertebral implant  100  is deployed within a patient. Alternatively, or in addition, having different widths W 3 , W 4  may facilitate the expansion of the expandable intervertebral implant  100  from a collapsed configuration to an expanded configuration. For example, a smaller width lower tongue  220  and/or lower tongue  232  may provide difference in friction coefficients between superior surfaces of the wedge  114 ,  116  and the endplates  110 ,  112  and inferior surfaces of the wedge  114 ,  116  and the endplates  110 ,  112 . In another embodiment, the widths W 3 , W 4  may be the same. In the illustrated embodiment, the upper tongue  232  has a greater width than the lower tongue  230  of the distal wedge  116 . In another embodiment, the lower tongue  230  has a greater width than the upper tongue  232  of the distal wedge  116 . 
       FIGS. 6I-6J  illustrate opposite side views of proximal wedge and a distal wedge in accordance with one embodiment.  FIG. 61  illustrates a left side view of the proximal wedge  114  and distal wedge  116  positioned relative to each other as they are when the expandable intervertebral implant  100  is assembled.  FIG. 6J  illustrates a right side view of the proximal wedge  114  and distal wedge  116  positioned relative to each other as they are when the expandable intervertebral implant  100  is assembled. 
       FIG. 7A  is a perspective top view of a proximal end of a lower endplate  112  and an upper endplate  110  with the upper endplate  110  shown upside down. The upper endplate  110  has a proximal end  120  and a distal end  122  and includes a proximal ramp  210  and a proximal groove  212 . The proximal ramp  210  may be near the proximal end  120 . The lower endplate  112  has a proximal end  130  and a distal end  132  and includes a proximal ramp  214 . The proximal ramp  214  may be near the proximal end  130 . 
     In the illustrated embodiment, the proximal ramp  210  includes a pair of upper proximal rails  702   a,b . The upper proximal rails  702   a,b  may extend from the proximal end  120  toward the distal end  122 . The upper proximal rails  702   a,b  may slide against and support the proximal wedge  114  as the expandable intervertebral implant  100  transitions from a collapsed configuration to an expanded configuration. Similarly, the proximal ramp  214  includes a pair of lower proximal rails  704   a,b . The lower proximal rails  704   a,b  may extend from the proximal end  130  toward the distal end  132 . The lower proximal rails  704   a,b  may slide against and support the proximal wedge  114  as the expandable intervertebral implant  100  transitions from a collapsed configuration to an expanded configuration. 
     Referring still to  FIG. 7A , the upper endplate  110  may include one or more cutouts  706   a,b . In certain embodiments, the cutouts  706   a,b  may be part of an inserter interface  615 . The cutouts  706   a,b  may form a ledge that begins on a surface of the proximal ramp  210  and extends towards the distal end  122 . The cutouts  706   a,b  may be shaped and sized to accommodate distal parts of an inserter fork  430  such that when the inserter fork  430  engages the expandable intervertebral implant  100  the inserter fork  430  is within a maximum cross-sectional diameter of the expandable intervertebral implant  100 . In this manner, the cutouts  706   a,b  enable the expandable intervertebral implant  100  to be used in a low diameter and confined space such as a cannula or a narrow minimally invasive surgical access path. 
     In certain embodiments, the lower endplate  112  may also include cutouts  708   a,b . In certain embodiments, the cutouts  708   a,b  may be part of the inserter interface  615 . The cutouts  708   a,b  may serve a similar purpose to the cutouts  706   a,b  on the proximal end  120  of the upper endplate  110  and may cooperate with the cutouts  706   a,b  to accept an inserter fork  430 , or other instrument, configured to engage the expandable intervertebral implant  100  for deployment of the expandable intervertebral implant  100 . 
     In certain embodiments, the lower endplate  112  may include one or more lower ramp pockets. Specifically, the lower endplate  112  may include a pair of proximal lower ramp pockets  710   a,b . In certain embodiments, a ramp pocket is a recess, opening, cutout, or other feature of an endplate configured to accept all or a portion of a ramp and/or a ramp rail of another endplate. Either, or both, of an upper endplate  110  and a lower endplate  112  can include one or more ramp pockets. Ramp pockets serve to enable two endplates to be brought closer together than corresponding endplates without ramp pockets. In the illustrated embodiment, the lower endplate  112  can include four ramp pockets, two towards the proximal end  130  and two towards the distal end  132  of the lower endplate  112 . Strategically placed ramp pockets can enable the upper endplate  110  and a lower endplate  112  to nest together when the expandable intervertebral implant  100  is in a collapsed configuration. 
     The pair of proximal lower ramp pockets  710   a,b  may be formed as part of the proximal ramp  214 . In the illustrated embodiment, the pair of proximal lower ramp pockets  710   a,b  are configured to receive the pair of upper proximal rails  702   a,b . In certain embodiments, the pair of proximal lower ramp pockets  710   a,b  may be formed as an opening that extends from a proximal lower ramp face of the proximal ramp  214  toward the distal end  132 . The proximal lower ramp face may be a surface of the proximal ramp  214 . The pair of proximal lower ramp pockets  710   a,b  may also extend from a side surface of the lower endplate  112  and into the proximal ramp  214 . In certain embodiments, the position and configuration of the proximal lower ramp pockets  710   a,b  can define and/or form the pair of lower proximal rails  704   a,b . Proximal lower ramp pockets  710   a,b  may also form a side for one or more fingers  134 . 
       FIG. 7B  is a perspective top view of a distal end  132  of a lower endplate  112  and an upper endplate  110  with the upper endplate  110  shown upside down. The lower endplate  112  has a distal end  132  and a proximal end  130  and includes a distal ramp  222  and a distal groove  224 . The distal ramp  222  may be near the distal end  132 . The upper endplate  110  has a distal end  122  and a proximal end  120  and includes a distal ramp  226  and a distal groove  228 . The distal ramp  226  may be near the distal end  122 . 
     In the illustrated embodiment, the distal ramp  226  includes a pair of upper distal rails  712   a,b . The upper distal rails  712   a,b  may extend from the distal end  122  toward the proximal end  120 . The upper distal rails  712   a,b  may slide against and support the distal wedge  116  as the expandable intervertebral implant  100  transitions from a collapsed configuration to an expanded configuration. Similarly, the distal ramp  222  includes a pair of lower distal rails  714   a,b . The lower distal rails  714   a,b  may extend from the distal end  132  toward the proximal end  130 . The lower distal rails  714   a,b  may slide against and support the distal wedge  116  as the expandable intervertebral implant  100  transitions from a collapsed configuration to an expanded configuration. 
     In certain embodiments, the lower endplate  112  may include one or more lower ramp pockets. Specifically, the lower endplate  112  may include a pair of distal lower ramp pockets  716   a,b . The pair of distal lower ramp pockets  716   a,b  may be formed as part of the distal ramp  222 . In the illustrated embodiment, the pair of distal lower ramp pockets  716   a,b  are configured to receive the pair of upper distal rails  712   a,b . In certain embodiments, the pair of distal lower ramp pockets  716   a,b  may be formed as an opening that extends from a distal lower ramp face of the distal ramp  222  toward the proximal end  130 . The distal lower ramp face may be a surface of the distal ramp  222 . The pair of distal lower ramp pockets  716   a,b  may also extend from a side surface of the lower endplate  112  and into the distal ramp  222 . In certain embodiments, the position and configuration of the distal lower ramp pockets  716   a,b  can define and/or form the pair of lower distal rails  714   a,b . Distal lower ramp pockets  716   a,b  may also form a side for one or more fingers  134 . 
     The lower endplate  112  has a proximal groove  216  and a distal groove  224  and the upper endplate  110  has proximal groove  212  and a distal groove  228 . Of course endplates of the expandable intervertebral implant  100  may have more or fewer grooves than those illustrated and described herein. Further, the cross-section shape of each groove of an expandable intervertebral implant  100  may differ in a single embodiment or in relation to other embodiments. 
     In the illustrated embodiment of  FIGS. 7A and 7B , different types of grooves may be used in one of the upper endplate  110  and the lower endplate  112 . In the present disclosure the grooves may be open end grooves of closed end grooves. An open end groove is a groove having one open end and a closed opposite end. An open end permits a tongue to move into the groove. A closed end prevents a tongue from moving into or exiting from the groove once the tongue enters the groove from an open end. 
       FIGS. 7A and 7B  illustrate that the expandable intervertebral implant  100  may include a proximal groove  212  and proximal groove  216  that are open end grooves and a distal groove  224  and distal groove  228  that are closed end grooves. As illustrated, the proximal groove  212  includes an open proximal end and an open distal end. Similarly, the proximal groove  216  includes an open proximal end and an open distal end. The distal groove  224  includes a closed proximal end  718  and an open distal end  720 . The distal groove  228  includes a closed proximal end  722  and an open distal end  724 . Grooves that include a closed end may form a “U” shaped groove as illustrated in  FIGS. 7A and 7B . 
       FIG. 7C  is a perspective top view of a proximal end of the expandable intervertebral implant  100  of  FIG. 1A  with the upper endplate  110  removed and shown upside down. Use of a combination of one or more open grooves and/or closed grooves can provide advantages in the manufacturing, design, fabrication, assembly, and deployment of expandable intervertebral implant  100  that includes one or more of these groove types. For example, in the illustrated embodiment, a closed groove for the distal groove  224  and distal groove  228  may facilitate assembly of the expandable intervertebral implant  100 . The closed distal groove  228  can accept a lower tongue  230  of the distal wedge  116  and retain the distal wedge  116  coupled to the lower endplate  112  as the other components are connected or coupled. For example, the distal wedge  116  can be slid distally and remain coupled to the lower endplate  112 . The upper tongue  232  of the distal wedge  116  can likewise be coupled to the upper endplate  110  via the closed distal groove  224 . Similarly, the open groove proximal groove  212  and open groove proximal groove  216  can further facilitate coupling the proximal wedge  114  to the endplates, actuator, and/or distal wedge  116 . 
       FIG. 8A  illustrates a proximal end view of a lower endplate  112  and an upper endplate  110  with the upper endplate  110  shown in an assembled position, other components are omitted for clarity.  FIG. 8A  illustrates the central plane  142  and a left side  144  and a right side  146 .  FIG. 8A  illustrates the upper proximal rails  702   a,b  and lower proximal rails  704   a,b . In the illustrated embodiment, the lower proximal rails  704   a,b  may be closer to the central plane  142  than the upper proximal rails  702   a,b . In another embodiment, the upper proximal rails  702   a,b  may be closer to the central plane  142  than the lower proximal rails  704   a,b . In yet another embodiment, one of the upper proximal rails  702   a,b  may be closer to the central plane  142  than one or more of the lower proximal rails  704   a,b , and vice versa. In one embodiment, the upper proximal rails  702   a  may not be vertically aligned with the lower proximal rails  704   a,b  so that the upper endplate  110  and lower endplate  112  can intermesh when in a collapsed configuration for a smaller profile for the expandable intervertebral implant  100 . 
       FIG. 8B  illustrates a distal end view of a lower endplate  112  and an upper endplate  110  with the upper endplate  110  shown in an assembled position, other components are omitted for clarity.  FIG. 8B  illustrates the central plane  142  and a left side  144  and a right side  146 .  FIG. 8A  illustrates the upper distal rails  712   a,b  and lower distal rails  714   a,b . In the illustrated embodiment, the lower distal rails  714   a,b  may be closer to the central plane  142  than the upper distal rails  712   a,b . In another embodiment, the upper distal rails  712   a,b  may be closer to the central plane  142  than the lower distal rails  714   a,b . In yet another embodiment, one of the upper distal rails  712   a,b  may be closer to the central plane  142  than one or more of the lower distal rails  714   a,b , and vice versa. In one embodiment, the upper distal rails  712   a  may not be vertically aligned with the lower proximal rails  714   a,b  so that the upper endplate  110  and lower endplate  112  can intermesh when in a collapsed configuration for a smaller profile for the expandable intervertebral implant  100 . 
       FIG. 8C  illustrates a perspective view of a central plane  142 , a lower endplate  112 , and an upper endplate  110  with the upper endplate  110  shown in an assembled position.  FIG. 8C  illustrates a couple of features. First,  FIG. 8C  illustrates with a perspective view an embodiment in which the lower proximal rail  704   b  is closer to the central plane  142  than the upper proximal rail  702   a  on the right side  146 . Second,  FIG. 8C  illustrates a relationship between the upper proximal rail  702   a  and the proximal lower ramp pocket  710   b.    
     Any methods disclosed herein comprise one or more steps or actions for performing the described method. The method steps and/or actions may be interchanged with one another. In other words, unless a specific order of steps or actions is required for proper operation of the embodiment, the order and/or use of specific steps and/or actions may be modified. 
     Reference throughout this specification to “an embodiment” or “the embodiment” means that a particular feature, structure or characteristic described in connection with that embodiment is included in at least one embodiment. Thus, the quoted phrases, or variations thereof, as recited throughout this specification are not necessarily all referring to the same embodiment. 
     Similarly, it should be appreciated that in the above description of embodiments, various features are sometimes grouped together in a single embodiment, Figure, or description thereof for the purpose of streamlining the disclosure. This method of disclosure, however, is not to be interpreted as reflecting an intention that any claim require more features than those expressly recited in that claim. Rather, as the following claims reflect, inventive aspects lie in a combination of fewer than all features of any single foregoing disclosed embodiment. Thus, the claims following this Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment. This disclosure includes all permutations of the independent claims with their dependent claims. 
     Recitation in the claims of the term “first” with respect to a feature or element does not necessarily imply the existence of a second or additional such feature or element. Elements recited in means-plus-function format are intended to be construed in accordance with 35 U.S.C. § 112 Para. 6. It will be apparent to those having skill in the art that changes may be made to the details of the above-described embodiments without departing from the underlying principles set forth herein. 
     While specific embodiments and applications of the present disclosure have been illustrated and described, it is to be understood that the scope of this disclosure is not limited to the precise configuration and components disclosed herein. Various modifications, changes, and variations which will be apparent to those skilled in the art may be made in the arrangement, operation, and details of the methods and systems of the present disclosure set forth herein without departing from it spirit and scope. 
     It should be appreciated that in the above description of embodiments, various features are sometimes grouped together in a single embodiment, Figure, or description thereof for the purpose of streamlining the disclosure. This method of disclosure, however, is not to be interpreted as reflecting an intention that any claim require more features than those expressly recited in that claim. Rather, as the following claims reflect, inventive aspects can be present in a combination of fewer than all features of any single foregoing disclosed embodiment. Thus, the claims following this Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment. This disclosure includes all permutations of the independent claims with their dependent claims. 
     Those of skill in the art will appreciate that the solutions provided in present disclosure may be accomplished with all, or less than all, of the components, structures, features, or aspects disclosed in the specification or illustrated in the figures in relation or a particular embodiment or claim.