Patent Publication Number: US-2020276028-A1

Title: Expandable interbody device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57, including U.S. patent application Ser. No. 16/049,503, filed Jul. 30, 2018, U.S. patent application Ser. No. 15/608,079, filed May 30, 2017, now U.S. Pat. No. 10,034,765, U.S. patent application Ser. No. 14/333,336, filed Jul. 16, 2014, now U.S. Pat. No. 9,668,876, U.S. Provisional Application No. 61/912,360, filed Dec. 5, 2013 and U.S. Provisional Application No. 61/912,432, filed Dec. 5, 2013. 
    
    
     BACKGROUND 
     Field 
     The present disclosure generally relates to the field of spinal orthopedics, and more particularly to expandable spinal implants for placement in intervertebral spaces between adjacent vertebrae. 
     Related Art 
     The spine is a flexible structure that extends from the base of the skull to the tailbone. The weight of the upper body is transferred through the spine to the hips and the legs. The spine contains a plurality of bones called vertebrae. The vertebrae are hollow and stacked one upon the other, forming a strong hollow column for support. The hollow core of the spine houses and protects the nerves of the spinal cord. The spine is held upright through the work of the back muscles, which are attached to the vertebrae. While the normal spine has no side-to-side curve, it does have a series of front-to-back curves, giving it a gentle “S” shape. 
     Each vertebra is separated from the vertebra above or below by a cushion-like, fibrocartilage called an intervertebral disc. The discs act as shock absorbers, cushioning the spine, and preventing individual bones from contacting each other. In addition, intervertebral discs act as a ligament that holds vertebrae together. Intervertebral discs also work with the facet joint to allow for slight movement of the spine. Together, these structures allow the spine to bend, rotate and/or twist. 
     The spinal structure can become damaged as a result of degeneration, dysfunction, disease and/or trauma. More specifically, the spine may exhibit disc collapse, abnormal curvature, asymmetrical disc space collapse, abnormal alignment of the vertebrae and/or general deformity, which may lead to imbalance and tilt in the vertebrae. This may result in nerve compression, disability and overall instability and pain. If the proper shaping and/or curvature are not present due to scoliosis, neuromuscular disease, cerebral palsy, or other disorder, it may be necessary to straighten or adjust the spine into a proper curvature with surgery to correct these spinal disorders. 
     Surgical treatments may involve manipulation of the spinal column by attaching a corrective device, such as rods, wires, hooks or screws, to straighten abnormal curvatures, appropriately align vertebrae of the spinal column and/or reduce further rotation of the spinal column. The correct curvature is obtained by manipulating the vertebrae into their proper position and securing that position with a rigid system of screws and rods. The screws may be inserted into the pedicles of the vertebrae to act as bone anchors, and the rods may be inserted into heads of the screws. Two rods may run substantially parallel to the spine and secure the spine in the desired shape and curvature. Thus the rods, which are shaped to mimic the correct spinal curvature, force the spine into proper alignment. Bone grafts are then placed between the vertebrae and aid in fusion of the individual vertebrae together to form a correctly aligned spine. 
     Other ailments of the spine result in degeneration of the spinal disc in the intervertebral space between adjacent vertebrae. Disc degeneration can cause pain and other complications. Conservative treatment can include non-operative treatment requiring patients to adjust their lifestyles and submit to pain relievers and a level of underlying pain. Operative treatment options include disc removal. This can relieve pain in the short term, but also often increases the risk of long-term problems and can result in motor and sensory deficiencies resulting from the surgery. Disc removal and more generally disc degeneration disease are likely to lead to a need for surgical treatment in subsequent years. The fusion or fixation will minimize or substantially eliminate relative motion between the fixed or fused vertebrae. In surgical treatments, interbody implants may be used to correct disc space collapse between adjacent vertebra, resulting in spinal fusion of the adjacent vertebra. 
     A fusion is a surgical method wherein two or more vertebrae are joined together (fused) by way of interbody implants, sometimes with bone grafting, to form a single bone. The current standard of care for interbody fusion requires surgical removal of all or a portion of the intervertebral disc. After removal of the intervertebral disc, the interbody implant is implanted in the interspace. In many cases, the fusion is augmented by a process called fixation. Fixation refers to the placement of screws, rods, plates, or cages to stabilize the vertebrae so that fusion can be achieved. 
     Interbody implants must be inserted into the intervertebral space in the same dimensions as desired to occupy the intervertebral space after the disc is removed. This requires that an opening sufficient to allow the interbody implant must be created through surrounding tissue to permit the interbody implant to be inserted into the intervertebral space. In some cases, the intervertebral space may collapse prior to insertion of the interbody implant. In these cases, additional hardware may be required to increase the intervertebral space prior to insertion of the implant. 
     In addition, minimally invasive surgical techniques have been used on the spine. Under minimally invasive techniques, access to the intervertebral space is taken to reach the spine through small incisions. Through these incisions, discs are removed and an interbody implant is placed in the intervertebral disc space to restore normal disc height. Minimally invasive spine surgery offers multiple advantages as compared to open surgery. Advantages include: minimal tissue damage, minimal blood loss, smaller incisions and scars, minimal post-operative discomfort, and relative quick recovery time and return to normal function. 
     SUMMARY 
     It would be desirable to insert an interbody device with a first smaller dimension into an intervertebral space and once in place, deploy to a second, relatively larger dimension to occupy the intervertebral space. This first smaller dimension can permit the use of minimally invasive surgical techniques for easy access to the intervertebral space, which can cause less disruption of soft and boney tissue in order to get to the intervertebral space. The interbody device may be implanted with or without the need of additional hardware. 
     Disclosed is an expandable interbody device that is configured to have an initial collapsed configuration having a first height suitable for being inserted into an intervertebral space between a pair of adjacent vertebrae, and an expanded configuration having a second height that is greater than the first height. The implant can be expanded from the initial collapsed configuration to the expanded configuration in-situ. The expanded configuration can provide support to the adjacent vertebrae while bone fusion occurs and can also provide rigid support between the adjacent vertebrae that withstands compressive forces. In some configurations, the expandable interbody device can help increase the distance between the adjacent vertebrae. By inserting the expandable interbody device in the initial collapsed configuration into the intervertebral space, it is possible to perform the surgery percutaneously with minimal disruption to tissues surrounding the surgical site and intervening soft tissue structures. The expandable interbody device can be implanted through a minimally invasive or an open wound procedure. 
     In accordance with at least one of the embodiments disclosed herein, an expandable interbody device for placement between adjacent vertebrae can comprise an upper structure comprising an upper proximal angled surface and an upper distal angled surface; a lower structure comprising a lower proximal angled surface and a lower distal angled surface, the lower structure configured to slideably couple with the upper structure; and a screw mechanism between the upper structure and the lower structure. The screw mechanism can comprise a proximal section comprising a proximal frustoconical surface, a distal section comprising a distal frustoconical surface, and a coupler comprising a proximal side configured to engage the proximal section and a distal side configured to engage the distal section, wherein the proximal section and the distal section are configured to rotate as a unit to change a length of the screw mechanism from a first length to a second length. The proximal frustoconical surface can be configured to engage the upper proximal angled surface and the lower proximal angled surface, and the distal frustoconical surface can be configured to engage the upper distal angled surface and the lower distal angled surface to move the upper structure and the lower structure from a first distance to a second distance. 
     The coupler can further comprise at least one anti-rotational feature configured to engage the upper structure or lower structure to prevent the coupler from rotating when the proximal section and the distal section are rotated. 
     The proximal section can comprise first threads wound in a first direction configured to engage a proximal threaded hole in the coupler, and the distal section can comprise second threads wound in a second direction, opposite the first direction, configured to engage a distal threaded hole in the coupler. In some embodiments, the first threads and the second threads have an equal pitch, such that when the screw mechanism is actuated, a proximal end of the interbody device changes height at the same rate as a distal end of the interbody device. In other embodiments, the first threads and the second threads have a different pitch, such that when the screw mechanism is actuated, a proximal end of the interbody device changes height at a different rate than a distal end of the interbody device. 
     The upper structure and lower structure can further comprise a plurality of protrusions or teeth. The upper structure and/or the lower structure can comprise vertebrae engagement surfaces with a porous or roughened surface. For example, the vertebrae engagement surfaces can comprise a titanium coating. 
     In some embodiments, the proximal section comprises at least one hole in fluid communication with a drive interface and an interior cavity of the interbody device. The interbody device can further comprise at least one recess configured to couple with a deployment tool, the at least one recess comprising a hole in fluid communication with an interior cavity of the interbody device. 
     In some embodiments, the distal section comprises a keyed shaft configured to slideably engage with a matching keyed bore on the proximal section. 
     In accordance with at least one of the embodiments disclosed herein, an expandable interbody device for placement between adjacent vertebrae can comprise an upper structure, a lower structure configured to slideably couple with the upper structure, and a screw mechanism between the upper structure and the lower structure, the screw mechanism comprising a proximal section and a distal section that are configured to rotate as a unit to change a length of the screw mechanism from a first length to a second length, wherein the change in the length of the screw mechanism causes the distance between the upper structure and the lower structure to change from a first distance to a second distance to form a chamber to be filled by one or more of fluids, medication, bone graft material, allograft and Demineralized Bone Matrix. 
     In accordance with at least one of the embodiments disclosed herein, a kit for performing spinal stabilization can comprise an expandable interbody device for placement between adjacent vertebrae, wherein in an expanded configuration the expandable interbody device comprises a chamber, and a deployment tool for delivering the expandable interbody device between adjacent vertebrae, the deployment tool comprising a distal portion that is releasably attachable to the expandable interbody device and a proximal portion configured to extend outside a surgical incision. The proximal portion can comprise an opening to a channel that extends through the deployment tool and is in fluid communication with the distal portion of the deployment tool, the channel capable of transporting a material from outside the incision into the chamber of the expandable interbody device. 
     In some embodiments, a proximal section of the expandable interbody device comprises at least one hole in fluid communication with the chamber. The expandable interbody device can further comprise at least one recess with a hole that is in fluid communication with the chamber. The deployment tool can comprise arms that are configured to attach to the at least one recess and further comprise one or more channels extending to the tips of the arms to deliver material through the at least one recess into the chamber of the expandable interbody device. 
     In accordance with at least one of the embodiments disclosed herein, a method of implanting an expandable interbody device between adjacent vertebrae can comprise positioning the expandable interbody device between adjacent vertebrae. The expandable interbody device can comprise an upper structure, a lower structure configured to slideably couple with the upper structure, and a screw mechanism between the upper structure and the lower structure. The method can further comprise rotating the screw mechanism to change a length of the screw mechanism from a first length to a second length which causes the distance between the upper structure and the lower structure to change from a first distance to a second distance to form a chamber, and injecting material into the chamber. 
     In some embodiments, the first distance corresponds to a collapsed configuration with the upper structure adjacent the lower structure and the second distance corresponds to an expanded configuration with the upper structure separated from the lower structure. 
     The screw mechanism can comprise a proximal section comprising a proximal frustoconical surface, a distal section comprising a distal frustoconical surface, and a coupler comprising a proximal side configured to engage the proximal section and a distal side configured to engage the distal section. 
     The material can be one or more of fluids, medication, bone graft material, allograft and Demineralized Bone Matrix. 
     In some embodiments, the expandable interbody device can be positioned between the adjacent vertebrae using a deployment tool that extends from the vertebrae to outside an incision. 
     The step of injecting the material can comprise delivering the material through a channel extending through the deployment tool. 
     In accordance with at least one of the embodiments disclosed herein, an expandable interbody device for placement between adjacent vertebrae can comprise an outer structure having a central opening and front and back sides with opposed front and back openings, an inner structure configured to slideably fit vertically within the outer structure central opening, the inner structure having a central opening and front and back sides with opposed front and back threaded holes axially aligned with the opposed front and back openings of the outer structure, and a variable length screw mechanism having proximal and distal heads slideably engaged to the front and back openings of the outer structure, and proximal and distal threaded shafts threadably coupled to the front and back threaded holes of the inner structure, wherein rotation of the screw mechanism changes a length of the screw mechanism from a first length to a second length and the proximal and distal heads compress against the front and back openings resulting in vertical translation of the inner structure relative to the outer structure from a first height to a second height. 
     The first height can be a collapsed configuration with the inner structure within the outer structure central opening and the second height can be an expanded configuration with the inner structure extending vertically out of the outer structure central opening. 
     The threaded shafts can comprise proximal threads threadably coupled to the front threaded hole with first threads in a first direction, and distal threads threadably coupled to the back threaded hole with second threads in a second direction, opposite the first direction, such that when the screw mechanism is rotated, the length of the screw mechanism increases or decreases. In some embodiments, the first and second threads have an equal pitch, such that when the screw mechanism is rotated the vertical translation of a proximal end and a distal end of the inner structure moves at a same rate relative to a proximal end and a distal end of the outer structure. In other embodiments, the first and second threads have a different pitch, such that when the screw mechanism is rotated the vertical translation of a proximal end of the inner structure relative to the outer structure moves at a different rate than a distal end of the inner structure relative to the outer structure. 
     In some embodiments, the front and back openings of the outer structure comprise ramp portions and the proximal and distal heads of the variable length screw mechanism can be configured to engage and slide along the ramp portions during translation of the inner structure relative to the outer structure. In other embodiments, the front and back openings of the outer structure have non-complementary engagement surfaces with the proximal and distal heads of the variable length screw mechanism, and the proximal and distal heads of the variable length screw mechanism are configured to engage and slide along the non-complementary engagement surfaces during translation of the inner structure relative to the outer structure. 
     The interbody device can further comprise a keyed internal bore on the distal end of the proximal shaft, and a keyed outer surface on the proximal end of the distal shaft configured to slidingly engage with the keyed internal bore of the proximal shaft, wherein the keyed outer surface slides within the keyed internal bore to allow the screw mechanism to have a variable length. The outer structure and inner structure can further comprise a plurality of protrusions or teeth. 
     In some embodiments, the vertebrae engagement surfaces comprise a porous or roughened surface that may be formed of a porous material, coated with a porous material, or chemically etched to form a porous or roughened surface with pores for bone growth with the adjacent vertebra. 
     In accordance with at least one of the embodiments disclosed herein, an expandable interbody device for placement between adjacent vertebrae can comprise an outer structure having an outer wall enclosing a central opening, the outer wall having front and back sides with opposed front and back openings, an inner structure having an inner wall with a lower flanged portion enclosing a central opening, the inner wall being configured to slideably fit vertically within the outer structure central opening, the inner wall having front and back slots with ramps proximate the slots within the inner structure central opening, the front and back slots being axially aligned with the opposed front and back openings of the outer structure, and a screw mechanism coupled to the inner and outer structures. The screw mechanism can comprise a shaft with proximal and distal portions, and proximal and distal threaded ramped components threadably coupled to the proximal and distal portions, the ramped components being configured to slideably engage the ramps on the front and back sides of the inner structure during expansion of the screw mechanism. Rotation of the expansion screw mechanism can change a distance between the proximal and distal ramped components from a first length to a second length and the proximal and distal ramped components slide against the front and back ramps resulting in vertical translation of the inner structure relative to the outer structure from a first height to a second height. 
     The proximal and distal portions of the shaft can comprise proximal and distal ends positioned within the front and back openings of the outer structure. A proximal end of the shaft can comprise a tool engagement portion. 
     The shaft can comprise proximal threads threadably coupled to the proximal threaded ramped component with first threads in a first direction, and distal threads threadably coupled to the distal threaded ramped component with second threads in a second direction, opposite the first direction, such that when the screw mechanism is rotated, the distance between the proximal and distal ramped components increases or decreases. 
     In some embodiments, the first and second threads have an equal pitch, such that when the screw mechanism is rotated the vertical translation of a proximal end and a distal end of the inner structure moves at a same rate relative to a proximal end and a distal end of the outer structure. In other embodiments, the first and second threads have different pitches, such that when the screw mechanism is rotated the vertical translation of a proximal end of the inner structure relative to the outer structure moves at a different rate than a distal end of the inner structure relative to the outer structure. 
     The outer structure and inner structure can further comprise a plurality of protrusions or teeth. The vertebrae engagement surfaces can comprise a porous or roughened surface that may be formed of a porous material, coated with a porous material, or chemically etched to form a porous or roughened surface with pores for bone growth with the adjacent vertebra. 
     In accordance with at least one of the embodiments disclosed herein, a deployment tool for delivering an expandable interbody device between adjacent vertebrae can comprise a distal portion configured to releasably couple to the expandable interbody device, a proximal portion comprising a mechanism for coupling and releasing the expandable interbody device, and an actuation device capable of expanding the interbody device from a first configuration to a second configuration, wherein the proximal portion is configured to extend outside a surgical incision, wherein the proximal portion comprises an opening to a channel that extends through the deployment tool and is in fluid communication with the distal portion of the deployment tool, the channel capable of transporting a material from outside the incision into the expandable interbody device. 
     The distal portion can comprise arms configured to couple to at least one recess on the expandable interbody device. The arms can comprise one or more channels extending to the tips of the arms to deliver material through the at least one recess into a chamber of the expandable interbody device. The actuation device can comprise a shaft that extends through the deployment tool to drive the expandable interbody device at the distal portion by manipulating an actuator at the proximal portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Specific embodiments and modifications thereof will become apparent to those skilled in the art from the detailed description herein having reference to the figures that follow, of which: 
         FIG. 1  is a perspective view showing an expandable interbody device in a collapsed configuration, according to an embodiment of the present invention. 
         FIG. 2  is a perspective view showing the expandable interbody device of  FIG. 1  in an expanded configuration. 
         FIG. 3  is a cross-sectional view of the expandable interbody device of  FIG. 1  in a collapsed configuration. 
         FIG. 4  is a cross-sectional view of the expandable interbody device of  FIG. 2  in an expanded configuration. 
         FIG. 5  is a perspective exploded view showing the expandable interbody device of  FIG. 1 , including the outer structure, inner structure and screw mechanism. 
         FIG. 6  is a perspective exploded view showing the expandable interbody device of  FIG. 1  with the screw mechanism assembled with the inner structure prior to assembly into the outer structure. 
         FIG. 7  is a perspective view showing an expandable interbody device in a collapsed configuration, according to another embodiment of the present invention. 
         FIG. 8  is a perspective view showing the expandable interbody device of  FIG. 7  in an expanded configuration. 
         FIG. 9  is a cross-sectional view of the expandable interbody device of  FIG. 7  in a collapsed configuration. 
         FIG. 10  is a cross-sectional view of the expandable interbody device of  FIG. 8  in an expanded configuration. 
         FIG. 11  is a perspective exploded view showing the expandable interbody device of  FIG. 7 , including the outer structure, inner structure and screw mechanism. 
         FIG. 12  is a perspective view showing an expandable interbody device in a collapsed configuration, according to another embodiment of the present invention. 
         FIG. 13  is a top view of the expandable interbody device of  FIG. 12 . 
         FIG. 14  is a bottom view of the expandable interbody device of  FIG. 12 . 
         FIG. 15  is a side view of the expandable interbody device of  FIG. 12 . 
         FIG. 16  is a front view of the expandable interbody device of  FIG. 12 . 
         FIG. 17  is a rear view of the expandable interbody device of  FIG. 12 . 
         FIG. 18  is a perspective view showing the expandable interbody device of  FIG. 12  in an expanded configuration. 
         FIG. 19  is a perspective exploded view showing the expandable interbody device of  FIG. 12 , including the upper structure, lower structure and screw mechanism. 
         FIG. 20  is a cross-sectional view of the expandable interbody device of  FIG. 12  in a collapsed configuration. 
         FIG. 21  is a cross-sectional view of the expandable interbody device of  FIG. 18  in an expanded configuration. 
         FIG. 22  is a perspective view of the expandable interbody device of  FIG. 18  coupled to a deployment tool and being implanted between adjacent vertebrae. 
         FIG. 23  is a top view of the expandable interbody device and deployment tool of  FIG. 22 . 
         FIG. 24  is a top view of the shaft, handle and arms of the deployment tool of  FIG. 22 . 
         FIG. 25A  is a close-up top view of the arms of the deployment tool of  FIG. 22  in an open configuration. 
         FIG. 25B  is a close-up top view of the arms of the deployment tool of  FIG. 22  in a closed configuration. 
         FIG. 26  is a close-up perspective view of the expandable interbody device and deployment tool of  FIG. 22 . 
         FIG. 27  is a perspective view of an actuation device of the deployment tool of  FIG. 22 . 
         FIG. 28  is a cross-sectional top view of the deployment tool of  FIG. 22 . 
         FIG. 29  is a close-up cross-sectional view of the expandable interbody device and deployment tool showing fluid delivery through the screw mechanism. 
         FIG. 30  is a side view of the proximal section of the screw mechanism of  FIG. 19 . 
         FIG. 31  is a rear view of the proximal section of the screw mechanism of  FIG. 19 . 
         FIG. 32  is a cross-sectional view of the expandable interbody device and deployment tool showing fluid delivery through channels in the delivery tool, according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     An expandable interbody device can be configured to have an initial collapsed configuration having a first height suitable for being inserted into an intervertebral space between a pair of adjacent vertebrae, and an expanded configuration having a second height that is greater than the first height. The implant can be expanded from the initial collapsed configuration to the expanded configuration in-situ. The use of a small interbody implant which may be expanded in-situ allows the possibility of performing the surgery percutaneously with minimal disruption to tissues surrounding the surgical site and intervening soft tissue structures, through a minimally invasive or open procedure. The expandable interbody device of the present disclosure can include features that reduce displacement of soft tissue and structures during placement of the expandable interbody device while providing support after placement to the adjacent vertebrae while bone fusion occurs. The expandable interbody device includes a collapsed configuration with dimensions that can allow insertion of the expandable interbody device between the vertebrae. Once the expandable interbody device is positioned in a desired location between the vertebrae, the expandable interbody device may be expanded to an expanded configuration. The expanded configuration can increase the distance between the adjacent vertebrae and provide support to the adjacent vertebrae while bone fusion occurs. The expanded configuration can also provide rigid support between the adjacent vertebrae that withstands compressive forces. The expandable interbody device of the present disclosure may sometimes be referred to as an expandable interbody implant, expandable interbody spacer or expandable corpectomy device, all of which are envisioned for the present disclosure. 
     Several non-limiting embodiments will now be described with reference to the figures, wherein like numerals reflect like elements throughout. The terminology used in the description presented herein is not intended to be interpreted in any limited or restrictive way, simply because it is being utilized in conjunction with a detailed description of certain specific embodiments. Furthermore, some embodiments may include several novel features, no single one of which is solely responsible for its desirable attributes or which is essential to the devices and methods described herein. 
     The words proximal and distal are applied herein to denote specific ends of components of the instrument described herein. A proximal end refers to the end of a component nearer to an operator of the instrument when the instrument is being used. A distal end refers to the end of a component further from the operator and extending towards the surgical area of a patient and/or the implant. The words top, bottom, left, right, upper and lower are used herein to refer to sides of the device from the described point of view. These reference descriptions are not intended to limit the orientation of the implanted interbody device and the device can be positioned in any functional orientation. For example, in some configurations, the interbody device can be used in an upside-down orientation from the specific orientation described herein. 
     Referring now to  FIGS. 1-6 , an expandable interbody device  100  can be a spinal implant that includes an outer structure  102 , an inner structure  104 , and a screw mechanism  106 . The expandable interbody device  100  can be movable between a collapsed configuration (shown in  FIG. 1 ) to an expanded configuration (shown in  FIG. 2 ) utilizing the screw mechanism  106 . 
     The outer structure  102  can include a top surface  108 , a bottom surface  110 , a front side  112 , a back side  114 , and left and right sides  116 . A combination of the sides  112 ,  114  and  116  forms a wall that encloses a central opening  118 . The front side  112 , back side  114 , left and right sides  116  may have a varying height, length, thickness, and/or curvature radius. The left and right sides  116  may include longitudinal openings, slots or trenches  120  configured to interface with an insertion and/or deployment tool (not shown) during implantation and deployment of the device from the collapsed configuration to the expanded configuration. In some embodiments, the front side  112  and the back side  114  include slots  122  having inwardly facing ramp portions  124  on the outer surfaces proximate the slots  122 . The slots  122  and ramp portions  124  can interface with the screw mechanism  106 . As shown in  FIGS. 3 and 4 , the ramp portions  124  slant inward from the bottom toward the top. 
     In other embodiments not shown, the front side  112  and the back side  114  may include non-ramp features that interface with the screw mechanism  106  to translate inner structure  104  relative to the outer structure  102  from the collapsed configuration to the expanded configuration. For example, as long as the screw mechanism  106  head geometry and the slots  122  or non-ramp features have non-complimentary surfaces, the inner and outer structures may translate and expand. For example, the contact surface of the screw head may be conical or spherical and the outer structure may have a bore with a sharp ledge. As the screw head is drawn toward that ledge, the inner and outer structures may translate and expand. 
     The inner structure  104  can include a top surface  126 , a bottom surface  128 , a front side  130 , a back side  132 , and left and right sides  134 . A combination of the sides  130 ,  132  and  134  forms an outer wall and inner wall that can enclose a central opening  136 . The central opening  136  can be configured to receive bone graft material such as allograft and/or Demineralized Bone Matrix (“DBM”) packing. In some embodiments, the inner structure  104  may not have a central opening  136  and the top surface  126  can be closed. The inner structure  104  outer wall can be configured to slideably fit within the central opening  118  of the outer structure  102 . The front side  130  can include a distal threaded hole  140  and the back side  132  can include a proximal threaded hole  138  that interface with the screw mechanism  106  and are longitudinally aligned with the slots  122  of the outer structure  102 . The threaded holes  138 ,  140  can have threads in opposite directions, one having a left hand thread and the other a right hand thread. With matching opposite threads on the screw mechanism  106 , the screw mechanism  106  can contract or extend when turned to expand or collapse the interbody device, as discussed in more detail below. The front side  130 , back side  132 , left and right sides  134  may have a varying height, length, thickness, and/or curvature radius. In some embodiments, when the inner structure  104  is positioned within the outer structure  102 , the height and/or curvature radius of the top surfaces  108 ,  126 , and bottom surfaces,  110 ,  128 , of each should be approximately the same, as shown in  FIGS. 1 and 3 . In other embodiments, the height and/or curvature radius of each may be different. 
     The top surfaces  108 ,  126  and the bottom surfaces  110 ,  128  of the outer and inner structures  102 ,  104  can include a plurality of protrusions or teeth  142  (hereinafter, referred to as “teeth”). Teeth  142  can be configured to be spaced throughout the top surfaces  108 ,  126  and the bottom surfaces  110 ,  128 . As can be understood by one skilled in the art, the teeth  142  can be configured to have variable thickness, height, and width as well as angles of orientation with respect to surfaces  108 ,  126  and  110 ,  128 . The teeth  142  can be further configured to provide additional support after the expandable interbody device  100  is implanted in the intervertebral space of the patient. The teeth  142  can reduce movement of the outer structure  102  and inner structure  104  with the vertebrae and create additional friction between the vertebrae and the outer structure  102  and inner structure  104 . 
     In some embodiments, the teeth  142  on the top surfaces  108 ,  126  and the bottom surfaces  110 ,  128  can be configured to match when the outer structure  102  and inner structure  104  are joined in the collapsed configuration, as shown in  FIG. 1 . In other embodiments, the teeth  142  on the top surface  108  and the bottom surface  110  of the outer structure  102  may have different spacing, configuration, thickness, height, and width as well as angles of orientation with respect to the teeth  142  on the top surface  126  and the bottom surface  128  of the inner structure  104 . In other embodiments, the outer structure  102  and the inner structure  104  may only have the teeth  142  on surfaces that contact the lower and upper vertebrae in the expanded configuration. For example, the outer structure  102  may only have teeth  142  on the bottom surface in contact with the lower vertebrae while the inner structure  104  may only have the teeth  142  on the top surface  126  in contact with the upper vertebrae. 
     In some embodiments, the top surfaces  108 ,  126  and the bottom surfaces  110 ,  128  may be a porous or roughened surface, for example, they may be formed of a porous material, coated with a porous material, or chemically etched to form a porous or roughened surface with pores that participate in the growth of bone with the adjacent vertebra. 
     As shown in the figures, the screw mechanism  106  can include a proximal section  150  and a distal section  152  loosely coupled in a keyed configuration, such that when the proximal section  150  is rotated, the distal section  152  also rotates as a unit. For example, the distal section  152  may have a keyed shaft outer surface that slideably engages a bore on the proximal section  150  having a matching keyed inner surface. Therefore, the distal section  152  does not have to be rigidly connected to the proximal section  150 . One skilled in the art may appreciate that any suitable shapes or geometric configurations for a keyed connection between the proximal and distal sections  150 ,  152  may be included in the screw mechanism  106  to achieve the desired results. 
     In use, the screw mechanism  106  engages the outer structure  102  and inner structure  104  such that when it is rotated, the inner structure  104  translates relative to the outer structure  102  from the collapsed configuration to the expanded configuration. If desired, the screw mechanism  106  may be rotated in the opposite direction to translate the inner structure  104  from the expanded configuration back to the collapsed configuration. This allows the expandable interbody device  100  to be moved to another location or repositioned if it is expanded in the wrong location and needs to be collapsed prior to moving or repositioning. 
     The proximal section  150  and the distal section  152  may be fabricated from any biocompatible material suitable for implantation in the human spine, such as metal including, but not limited to, titanium and its alloys, stainless steel, surgical grade plastics, plastic composites, ceramics, bone, or other suitable materials. In some embodiments, the proximal section  150  and the distal section  152  may be formed of a porous material that participates in the growth of bone with the adjacent vertebral bodies. In some embodiments, the proximal section  150  and the distal section  152  may include a roughened surface that is coated with a porous material, such as a titanium coating, or the material may be chemically etched to form pores that participate in the growth of bone with the adjacent vertebra. In some embodiments, only portions of the proximal section  150  and the distal section  152  may be formed of a porous material, coated with a porous material, or chemically etched to form a porous surface, such as the upper and lower surfaces that contact the adjacent vertebra are roughened or porous. In some embodiments, the surface porosity may be between 50 and 300 microns. 
     The proximal section  150  can include a shaft  154  with an internal bore  156  extending along its longitudinal axis. In some embodiments, shaft  154  has a cylindrical outer surface and the internal bore has a non-cylindrical surface or keyed surface, such as a square or hexagonal inner surface. The proximal section  150  can also include an external screw threaded portion  158  configured to couple with the proximal threaded hole  138  of the inner structure  104 . The proximal end of the shaft can include a proximal circular head  160  adapted to receive a driving tool for rotating or driving the proximal section  150 , and the distal end of the shaft  154  can be configured to receive the keyed shaft portion of the distal section  152  within the internal bore  156 . Between the external screw thread portion  158  and the head  160  can be a cylindrical engagement portion  162  configured to fit within the slot  122  of the outer structure  102 . The distal portion of the head  160  can have a spherical surface  164  configured to engage and slide along the proximal curved or ramp portion  124  of the outer structure  102 . 
     The distal section  152  can include a distal circular head  166 , external screw threaded portion  168  configured to couple with the distal threaded hole  140  of the inner structure  104 , a cylindrical engagement portion  162  positioned between the distal head  166  and external screw thread portion  168  configured to fit within the distal slot  122  of the outer structure  102 , and a keyed shaft  170  portion. The keyed shaft  170  portion can be configured to slideably fit within the internal bore  156  of the proximal section  150 . When joined, the keyed shaft  170  portion and internal bore  156  act as a keyed shaft and sleeve arrangement, such that when the proximal section  150  is rotated, the distal section  152  also rotates as a unit. The proximal portion of the head  166  can have a spherical surface  172  configured to engage and slide along the distal curved or ramp portion  124  of the outer structure  102 , as illustrated in  FIGS. 3 and 4 . 
     As mentioned above, the external screw threaded portions  158 ,  168  of the screw mechanism  106  can match the threaded holes  138 ,  140  of the inner structure  104 . Since threaded holes  138 ,  140  have thread patterns in opposite directions, the external screw thread portions  158 ,  168  may also have matching thread patterns in opposite directions. In some embodiments, the threaded holes and external screw thread portions may have equal pitch, such that during expansion, the proximal and distal end of the outer structure  102  and inner structure  104  translate or move at the same rate. In other embodiments, the proximal threaded hole and proximal external screw thread portion may have a different pitch than the distal threaded hole and distal external screw thread portion, such that during expansion, the proximal and distal ends of the outer structure  102  and inner structure  104  translate or move at different rates. For example, the proximal end of the outer structure  102  and inner structure  104  may translate or move at a first rate of speed and the distal end of the outer structure  102  and inner structure  104  may translate or move at a second rate of speed. The first rate of speed may be faster or slower than the second rate of speed. This allows for some angularity between the outer structure  102  and inner structure  104  during expansion. The difference between the first and second rates of speed allows the user to select an expandable interbody device  100  that has some angulation after expansion to account for the lordotic curvature of the spine. 
     When the screw mechanism  106  is coupled to the inner structure  104  it may vary in length during interbody expansion (as shown in  FIGS. 3 and 4 ). Initially, the length of the screw mechanism  106  can be L1 in the collapsed configuration, shown in  FIG. 3 . As the screw mechanism  106  is rotated in a first direction, it acts like a compression screw and the length of the screw mechanism  106  contracts to L2 in the expanded configuration, shown in  FIG. 4 , due to the threads on the proximal and distal sections being threaded in opposite directions. By reversing rotation of the screw mechanism  106  in a second direction, opposite the first, the screw mechanism  106  may extend in length from L2 back to L1, if desired. 
     Referring to  FIGS. 5 and 6 , the expandable interbody device  100  can be assembled by inserting the proximal section  150  of the screw mechanism  106  into proximal threaded hole  138  and the distal section  152  of the screw mechanism  106  into distal threaded hole  140 . The external screw threaded portions  158 ,  168  engage the threaded holes  138 ,  140  and the keyed shaft  170  of the distal section  152  is slid within and engaged, or keyed, with the internal bore  156  of the proximal section  150 . The screw mechanism  106  is then rotated in the direction for contraction until the engagement portion  162  for each section is left exposed (see  FIG. 6 ). The inner structure  104  may then be lowered into the central opening  118  of the outer structure  102 , with the engagement portions  162  sliding into the proximal and distal slots  122  of the outer structure  102 . The screw mechanism  106  is then rotated until the spherical surface  164  of the proximal head  158  and the spherical surface  172  of the distal head  168  engage the proximal and distal curved or ramp portions  124  of the outer structure  102 , shown in  FIG. 3 . The expandable interbody device  100  is now ready to be inserted. 
     Referring back to  FIGS. 3 and 4 , in the collapsed configuration the expandable interbody device  100  may have a height of H1. The proximal head  160  spherical surface  164  is engaged with the proximal ramp portion  124  of the outer structure  102  and the distal head  166  spherical surface  172  is engaged with the distal ramp portion  124  of the outer structure  102 . When the screw mechanism  106  is rotated in a first direction, the proximal head  160  and the distal head  166  can move toward each other (from L1 to L2). While this happens, the spherical surfaces  164  and  172  start sliding up the proximal and distal incline ramps  124  and translating the inner structure  104  vertically from H1 (collapsed configuration) toward H2 (expanded configuration). The expandable interbody device  100  does not have to be completely extended to H2 and can be stopped anywhere between H1 and H2, depending on the expansion needed between the adjacent vertebrae. The proximal and distal ramps  124  may also have features that that require more force or less force on the screw mechanism  106  during expansion. This difference in forces may provide tactile feedback to the surgeon as an indication of expansion of the expandable interbody device  100 . 
     In some embodiments, the screw mechanism may be a compression screw having a proximal section threadably coupled to a distal section, the proximal section having a threaded shaft and the distal section having a threaded bore, such that when the proximal section is rotated, the threaded shaft engages the threaded bore to shorten or lengthen the distance between the proximal head  158  and the distal head  168 . In this embodiment, holes  138 ,  140  would be sized to slideably fit the proximal and distal shafts of the compression screw and would not be threaded holes. 
     The expandable interbody device  100  may also include a deployment tool. The deployment tool may include various attachment features to enable insertion of the expandable interbody device  100  into the patient. For example, the deployment tool may include arms or clamps to attach to the longitudinal openings, slots or trenches  120  of the outer structure  102  and an actuation device to couple with the head  160  of the proximal section  150  of the screw mechanism  106 . Once the expandable interbody device  100  has been inserted and positioned within the intervertebral space between two vertebrae, the deployment tool may actuate to deploy and expand the expandable interbody device  100  by applying a rotational force to screw mechanism  106 . 
     In operation, the expandable interbody device  100  may be inserted into the intervertebral disc space between two vertebrae using an insertion or deployment tool. In some cases, the disc space may include a degenerated disc or other disorder that may require a partial or complete discectomy prior to insertion of the expandable interbody device  100 . The deployment tool may engage with the proximal end of the expandable interbody device  100 . As the deployment tool applies the rotational force, the expandable interbody device  100  gradually expands as described above. The deployment tool may allow an increase in the amount of force that can be applied to the screw mechanism  106  to overcome the friction or interference between the spherical surfaces  164 ,  172  of the distal and proximal heads and ramp portions of the outer structure  104  during expansion of the expandable interbody device  100 . The increase in the force may be used to provide tactile feedback to the surgeon indicating near complete deployment of the expandable interbody device  100 . 
     In some embodiments, more than one expandable interbody device  100  can be implanted between the adjacent vertebrae of the patient. In such embodiments, multiple expandable interbody devices  100  can be placed in a side-by-side configuration or any other suitable configuration, thereby creating additional support. 
     Referring now to  FIGS. 7-11 , an expandable interbody device  200  can be a spinal implant that includes an outer structure  202 , an inner structure  204 , and a screw mechanism  206 . The expandable interbody device  200  can be movable between a collapsed configuration (show in  FIG. 7 ) to an expanded configuration (shown in  FIG. 8 ) utilizing the screw mechanism  206 . 
     Referring now to  FIG. 11 , the outer structure  202  can include a top surface  208 , a bottom surface  210 , a front side  212 , a back side  214 , and left and right sides  216 . A combination of the sides  212 ,  214  and  216  can form a wall that encloses a central opening  218 . The front side  212 , back side  214 , left and right sides  216  may have a varying height, length, thickness, and/or curvature radius. The left and right sides  216  may include longitudinal openings, slots or trenches  220  configured to interface with an insertion and/or deployment tool (not shown) during implantation and deployment of the device from the collapsed configuration to the expanded configuration. The front side  212  and the back side  214  can have holes  222  sized to slideably fit portions of the screw mechanism  206 , see  FIGS. 9 and 10 . 
     The inner structure  204  can include an inner portion  204   a  and a lower flanged portion  204   b . The inner portion  204   a  can include a top surface  226 , a front side  230   a , a back side  232   a , and left and right sides  234   a . In the illustrated embodiment, a combination of the sides  230   a ,  232   a  and  234   a  forms an outer wall and inner wall that encloses a central opening  236 . The inner portion  204   a  outer wall can be configured to slideably fit within the central opening  218  of the outer structure  202 , as shown in the figures. The front side  230   a  and the back side  232   a  can include slots  223  sized to slideably fit the screw mechanism  206  threads. The holes  222  of the outer structure  202  are aligned with the slots  223 . 
     The lower flanged portion  204   b  of the inner structure  204  can include a bottom surface  228 , a front side  230   b , a back side  232   b , and left and right sides  234   b . A combination of the sides  230   b ,  232   b  and  234   b  forms an outer wall and inner wall. The inner wall of the lower flanged portion  204   b  can also enclose the central opening  236 . 
     On the inner wall of the front side  230   a  and back side  232   a  are inwardly facing ramps  224  proximate the slots  223  within the central opening  236  of the inner structure  204  that interface with the screw mechanism  206 , shown in  FIGS. 9 and 10 . 
     The front sides  230   a ,  230   b , back sides  232   a ,  232   b , left and right sides  234   a ,  234   b , may have a varying height, length, thickness, and/or curvature radius. In some embodiments, when the inner structure  204  is positioned within the outer structure  202 , the curvature radius of the top surfaces  208 ,  226  can be approximately the same, as shown in  FIGS. 7 and 9 . In other embodiments, the curvature radius of each may be different. In some embodiments, the outer wall of the lower flanged portion  204   b  is approximately the same shape as the outer wall of the outer structure  202 , as shown in  FIGS. 7 and 9 . In other embodiments, the outer wall of each may be different. The central opening  236  can be configured to receive bone graft material such as allograft and/or Demineralized Bone Matrix (“DBM”) packing. 
     The top surfaces  208 ,  226  and the bottom surface  228  of the outer and inner structures  202 ,  204  can include a plurality of protrusions or teeth  242  (hereinafter, referred to as “teeth”). Teeth  242  can be configured to be spaced throughout the top surfaces  208 ,  226  and the bottom surface  228 . As can be understood by one skilled in the art, the teeth  242  can be configured to have variable thickness, height, and width as well as angles of orientation with respect to surfaces  208 ,  226  and  228 . The teeth  242  can be further configured to provide additional support after the expandable interbody device  200  is implanted in the intervertebral space of the patient. The teeth  242  can reduce movement of the outer structure  202  and inner structure  204  with the vertebrae and create additional friction between the vertebrae and the outer structure  202  and inner structure  204 . 
     In some embodiments, the teeth  242  on the top surfaces  208 ,  226  can be configured to match when the outer structure  202  and inner structure  204  are joined in the collapsed configuration, as shown in  FIG. 7 . In other embodiments, the teeth  242  on the top surface  208  of the outer structure  202  may have different spacing, configuration, thickness, height, and width as well as angles of orientation with respect to the teeth  242  on the top surface  226  of the inner structure  204 . In other embodiments, the outer structure  202  and the inner structure  204  may only have the teeth  242  on surfaces that contact the lower and upper vertebrae in the expanded configuration. For example, the outer structure  202  may only have teeth  242  on the top surface  208  in contact with the first vertebrae while the inner structure  204  may only have the teeth  242  on the bottom surface  228  in contact with the second vertebrae. 
     In some embodiments, the top surfaces  208 ,  226  and the bottom surface  228  may be a porous or roughened surface, for example, they may be formed of a porous material, coated with a porous material, or chemically etched to form a porous or roughened surface with pores that participate in the growth of bone with the adjacent vertebra. 
     The proximal section  250  and the distal section  252  of the screw mechanism  206  may be fabricated from any biocompatible material suitable for implantation in the human spine, such as metal including, but not limited to, titanium and its alloys, stainless steel, surgical grade plastics, plastic composites, ceramics, bone, or other suitable materials. In some embodiments, the proximal section  250  and the distal section  252  may be formed of a porous material that participates in the growth of bone with the adjacent vertebral bodies. In some embodiments, the proximal section  250  and the distal section  252  may include a roughened surface that is coated with a porous material, such as a titanium coating, or the material is chemically etched to form pores that participate in the growth of bone with the adjacent vertebra. In some embodiments, only portions of the proximal section  250  and the distal section  252  may be formed of a porous material, coated with a porous material, or chemically etched to form a porous surface, such as the upper and lower surfaces that contact the adjacent vertebra are roughened or porous. In some embodiments, the surface porosity may be between 50 and 300 microns. 
     As shown in the figures, the screw mechanism  206  can include a shaft  254 , a proximal ramped component  264  and a distal ramped component  272 . The proximal end of the shaft can include an opening  260  adapted to receive a driving tool for rotating the shaft  254 . The proximal and distal ramped components  264 ,  272  can have threaded holes  238 ,  240  with threads in opposite directions, hole  238  having a left hand thread and hole  240  a right hand thread, or vice versa. In the illustrated embodiment, the shaft  254  includes proximal section  250  with external threads  258 , and distal section  252  with external threads  268  in opposite directions, external threads  258  having a left hand thread and external thread  268  having a right hand thread, or vice versa, matching the threads  238 ,  240  of the proximal and distal ramped components  264 ,  272 . When assembled, proximal ramped component  264  is threaded onto the proximal thread  258  of the proximal section  250  while the distal ramped component  272  is threaded onto the distal thread  268  of the distal section  252 . Having opposite threads on the proximal and distal ramped components  264 ,  272  matching the proximal and distal sections  250 ,  252  can allow the proximal and distal ramped components  264 ,  272  to extend or contract along the shaft  254  when the screw mechanism  206  is rotated or turned to expand or collapse the interbody device (see below). 
     In use, the proximal and distal ramped components  264 ,  272  of the screw mechanism  206  can engage the inwardly facing ramps  224  and the proximal and distal sections  250 ,  252  can extend through slots  223  of the inner structure  204  and into holes  222  of the outer structure  202  (shown in  FIGS. 9 and 10 ). When the screw mechanism  206  is rotated, the proximal and distal ramped components  264 ,  272  move along the shaft  254  and slide along the inwardly facing ramps  224  of the inner structure  204  and the proximal and distal sections  250 ,  252  slide in slots  223  of the inner structure  204 , while the extreme part of the proximal and distal sections  250 ,  252  stay within the holes  222  of the outer structure  202 . This action translates the inner structure  204  relative to the outer structure  202  from the collapsed configuration to the expanded configuration. If desired, the screw mechanism  206  may be rotated in the opposite direction to translate the inner structure  204  from the expanded configuration back to the collapsed configuration. This can allow the expandable interbody device  200  to be moved to another location or reposition if it is expanded in the wrong location and needs to be collapsed prior to moving or repositioning. The shaft  254 , the proximal and distal ramped components  264 ,  272 , the outer structure  202  and inner structure  204  may be fabricated from any biocompatible material such as stainless steel, or other suitable material. 
     As discussed above, the external screw threaded portions  258 ,  268  can match the threaded holes  238 ,  240  of the ramped components  264 ,  272 . Since threaded holes  238 ,  240  may have thread patterns in opposite directions, the external screw thread portions  258 ,  268  may also have matching thread patterns in opposite directions. In some embodiments, the threaded holes and external screw thread portions may have equal pitch, such that during expansion, the proximal and distal end of the outer structure  202  and inner structure  204  translate or move at the same rate. In other embodiments, the proximal threaded hole and proximal external screw thread portion may have a different pitch than the distal threaded hole and distal external screw thread portion, such that during expansion, the proximal and distal ends of the outer structure  202  and inner structure  204  translate or move at different rates. For example, the proximal end of the outer structure  202  and inner structure  204  may translate or move at a first rate of speed and the distal end of the outer structure  202  and inner structure  204  may translate or move at a second rate of speed. The first rate of speed may be faster or slower than the second rate of speed. This can allow for some angularity between the outer structure  202  and inner structure  204  during expansion. The difference between the first and second rates of speed can allow the user to select an expandable interbody device  200  that has some angulation after expansion to account for the lordotic curvature of the spine. 
     When the screw mechanism  206  is coupled to the inner structure  204  the distance between the ramped components  264 ,  272  can vary in length during interbody expansion (as shown in  FIGS. 9 and 10 ). Initially, the distance is L3 in the collapsed configuration, shown in  FIG. 9 . As the screw mechanism  206  is rotated in a first direction, the distance between the ramped components  264 ,  272  can extend in length to L4 in the expanded configuration, shown in  FIG. 10 , due to the threads on the proximal and distal sections and ramped components being threaded in opposite directions. By reversing rotation of the screw mechanism  206  in a second direction, opposite the first, the distance may shorten in length from L4 back to L3, if desired. 
     Referring back to  FIGS. 9 and 10 , in the collapsed configuration the expandable interbody device  200  can have a height of H3. The proximal ramped component  264  can be engaged with the proximal ramp portion  224  and the distal ramped component  272  can be engaged with the distal ramp portion  224  of the inner structure  204 . When the screw mechanism  206  is rotated in a first direction, the proximal ramped component  264  and the distal ramped component  272  can move away from each other (from L3 to L4). While this happens, the proximal and distal ramped components  264  and  272  are forced against the proximal and distal incline ramps  224 , sliding the proximal and distal incline ramps  224  in a downward direction, translating the inner structure  204  vertically downward from H3 (collapsed configuration) toward H4 (expanded configuration). The expandable interbody device  200  does not have to be completely extended to H4 and can be stopped anywhere between H3 and H4, depending on the expansion needed between the adjacent vertebrae. The proximal and distal ramps  224  may also have features that that require more force or less force on the screw mechanism  206  during expansion. This difference in forces may provide tactile feedback to the surgeon as an indication of expansion of the expandable interbody device  200 . 
     The expandable interbody device  200  may also include a deployment tool. The deployment tool may include various attachment features to enable insertion of the expandable interbody device  200  into the patient. For example, the deployment tool may include arms or clamps to attach to the longitudinal openings, slots or trenches  220  of the outer structure  202  and an actuation device to couple with the head  260  of the proximal section  250  of the screw mechanism  206 . Once the expandable interbody device  200  has been inserted and positioned within the intervertebral space between two vertebrae, the deployment tool may actuate to deploy and expand the expandable interbody device  200  by applying a rotational force to screw mechanism  206 . 
     In operation, the expandable interbody device  200  may be inserted into the intervertebral disc space between two vertebrae using an insertion or deployment tool. In some cases, the disc space may include a degenerated disc or other disorder that may require a partial or complete discectomy prior to insertion of the expandable interbody device  200 . The deployment tool may engage with the proximal end of the expandable interbody device  200 . As the deployment tool applies the rotational force, the expandable interbody device  200  can gradually expand as described above. The deployment tool may allow an increase in the amount of force that can be applied to the screw mechanism  206  to overcome the friction or interference between the proximal and distal ramped components  264 ,  272  and ramp portions  224  of the inner structure  204 . The increase in the force may be used to provide tactile feedback to the surgeon indicating near complete deployment of the expandable interbody device  200 . 
     In some embodiments, more than one expandable interbody device  200  can be implanted between the adjacent vertebrae of the patient. In such embodiments, multiple expandable interbody devices  200  can be placed in a side-by-side configuration or any other suitable configuration, thereby creating additional support. 
     With reference to  FIGS. 12-19 , some embodiments of the expandable interbody device  300  can include an upper structure  302 , a lower structure  304 , and a screw mechanism  306 . The expandable interbody device  300  can be changeable between a collapsed configuration, as shown in  FIG. 12 , to an expanded configuration, as shown in  FIG. 18 . 
     The upper structure  302  can include a top surface  308 , a distal side  312 , a proximal side  314 , and left and right sides  316 . One or more slots  318  can extend through the upper structure  302 , having an opening on the top surface  308  that is in fluid communication with the bottom of the upper structure  302 . The one or more slots  318  can be configured to receive fluids, medication, bone graft material, or other material to help in the integration of the interbody device with the vertebrae, such as with allograft and/or Demineralized Bone Matrix (“DBM”) packing. The distal side  312 , proximal side  314 , and left and right sides  316  may have a varying height, length, thickness, and/or curvature radius. In some embodiments, the upper structure  302  may not have any slots and the top surface  308  can be closed. In some embodiments, the upper structure  302  can have one or more markers  319  to help visualization using radiation during the implantation procedure. The marker  319  can be made of a radiopaque material, such as titanium. 
     The lower structure  304  can include a bottom surface  328 , a distal side  330 , a proximal side  332 , and left and right sides  334 . One or more slots  336  can extend through the lower structure  304 , having an opening on the bottom surface  328  that is in fluid communication with the top of the lower structure  304 . In some embodiments, the one or more slots  336  may line up with the one or more slots  318  on the upper structure  302 , such that the slots extend through the interbody device  300 . The one or more slots  336  can be configured to receive fluids, medication or other material to help in the integration of the interbody device with the vertebrae, such as with allograft and/or Demineralized Bone Matrix (“DBM”) packing. The distal side  330 , proximal side  332 , and left and right sides  334  may have a varying height, length, thickness, and/or curvature radius. In some embodiments, the lower structure  304  may not have any slots and the bottom surface  328  can be closed. In some embodiments, the lower structure  304  can have one or more markers  337  to help visualization using radiation during the implantation procedure. The marker  337  can be made of a radiopaque material, such as titanium. The left and right sides  334  may include recesses  320  configured to interface with a deployment tool during implantation and deployment of the device from the collapsed configuration to the expanded configuration, as explained below. In some embodiments, the recesses  320  can extend through to the inner cavity of the interbody device and can be used as an access location for delivering fluids, medication or other material, as discussed below. 
     The top surface  308  of the upper structure  302  and the bottom surface  328  of the lower structure  304  can have a roughened surface, such as a plurality of protrusions or teeth  342 . The protrusions can be configured to be spaced throughout the top surface  308  and the bottom surface  328 . As can be understood by one skilled in the art, the protrusions can be configured to have variable thickness, height, and width as well as angled surfaces. For example, as illustrated in  FIG. 15 , the top surface  308  and bottom surface  328  can have teeth  342  that are angled toward the proximal side. The distal facing side of the teeth  342  are less steep than the proximal facing side of the teeth  342 . This can allow for easy insertion of the interbody device and help prevent backing out of the device from the intervertebral space. The teeth  342  can be configured to provide additional support after the expandable interbody device  300  is implanted in the intervertebral space of the patient. For example, the friction between the vertebrae and the upper structure  302  and lower structure  304 , provided at least in part by the teeth  342 , can help reduce movement of the interbody device  300  in the intervertebral space. 
     The upper structure  302  and lower structure  304 , or portions thereof, can be made of any of a variety of materials known in the art, including but not limited to a polymer such as polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyethylene, fluoropolymer, hydrogel, or elastomer; a ceramic such as zirconia, alumina, or silicon nitride; a metal such as titanium, titanium alloy, cobalt chromium or stainless steel; or any combination of the above materials. The interbody device  300  may be made of multiple materials in combination. For example, the upper structure  302  can comprise a polymer, such as PEEK or polyethylene, and the lower structure  304  can comprise a metal or ceramic. 
     In some embodiments, the upper structure  302  and/or the lower structure  304  may be formed of a porous material or have a roughened surface. The surfaces may be formed of a porous material, coated with a porous material, or chemically etched to form a porous or roughened surface with pores, which may help participate in the growth of bone with the adjacent vertebra. In some embodiments, only portions of the interbody device  300  may be formed of a porous material, coated with a porous material, or chemically etched to form a porous surface. For example, at least some portions of the top surface  308  and/or the bottom surface  328  can be coated with a porous material, such as a titanium coating. In some embodiments, the surface porosity may be at least approximately 50 microns and less than or equal to approximately 300 microns. 
     The upper structure  302  can be configured to slideably fit with the lower structure  304 . For example, in the embodiment illustrated in  FIG. 21  the upper structure  302  has smooth surfaces on its sides that slide against smooth surfaces on the sides of the lower structure  304  to form a slide bearing. In other embodiments, the upper structure and lower structure can have any of a plurality of different types of functional couplers to form a slideable connection. 
     The distal sides  312 ,  330  and the proximal sides  314 ,  332  of the top surface  308  and bottom surface  328  can have a screw opening  322  that accepts the screw mechanism  306 , as illustrated in  FIG. 21 . The outer surfaces of the screw opening  322  can have an angled surface  324 . The angled surface  324  can flare outward toward the surface, such that the screw opening  322  is larger at the surface of the distal side or proximal side than the opening in toward the middle. When the upper structure  302  and the lower structure  304  are in the collapsed configuration, the angled surfaces  324  can form a frustoconical shape. The upper structure  302  can have approximately half of the cone and the lower structure can have approximately half of the cone. The angled surfaces  324  can interface with the screw mechanism  306  to transition the interbody device  300  from the collapsed to expanded configuration, as explained below. 
     With reference to  FIG. 19 , the screw mechanism  306  can include a proximal section  350 , a distal section  352  and a coupler  380 . The coupler  380  can have a proximal hole  382  configured to engage the proximal section  350  and a distal hole  384  configured to engage the distal section  352 . The holes  382 ,  384  can have threads in opposite directions (i.e., one having a left hand thread and the other a right hand thread). The proximal section  350  can have threads that are configured to engage threads in the proximal hole  382  and the distal section  352  can have threads that are configured to engage threads in the distal hole  384 . In the illustrated embodiment, the proximal section  350  and distal section  352  have external threads while the coupler  380  has internal threads. In other embodiments, the coupler can have external threads while the proximal section and distal section have internal threads. As discussed in more detail below, the threads in opposite directions enable the screw mechanism  306  to contract or extend when rotated. 
     The coupler  380  can include protrusions  386  configured to engage with apertures  388 ,  390  in the upper structure  302  and lower structure  304 , respectively, to prevent the coupler  380  from rotating as the proximal section  350  of is rotated with a drive tool. In the illustrated embodiment of  FIGS. 12-19 , the coupler  380  includes two protrusions  386  having oval shaped extensions that fit into oval-shaped apertures  388 ,  390 . In other embodiments, the protrusions can have any of a variety of shapes, such as cylindrical or rectangular extensions. 
     The proximal section  350  can include a threaded portion  358  configured to engage the threads on the proximal hole  382  of the coupler  380 . The proximal end of the proximal section  350  can include a head  360  with a drive interface  361  adapted to receive a driving tool for rotating or driving the proximal section  350 . In the illustrated embodiment, the head  360  has a hexagonal shaped cavity for receiving a hexagonal drive wrench. In other embodiments, the head can have any of a variety of drive interfaces, such as slotted, cross and polygonal heads. The distal end of the proximal section  350  can have a bore  356  extending along its longitudinal axis configured to receive a shaft  370  of the distal section  352 . The distal facing side of the head  360  can have an angled surface  364  configured to slide and press against the angled surfaces  324  of the upper structure  302  and lower structure  304 . For example, the angled surface  364  can be a tapered cylindrical surface (i.e., a frustoconical shape as illustrated in  FIG. 19 ), with sufficient smoothness to functionally slide and press against the angled surfaces  324 . 
     The distal section  352  can include a head  366  and a threaded portion  368  configured to couple with the distal hole  384  of the coupler  380 . The distal section  352  can also have a shaft  370  extending proximally along the longitudinal axis that is configured to slideably couple with the bore  356  of the proximal section  350 . As described below, the shaft  370  and bore  356  can be keyed, such that when the proximal section  350  is rotated, the distal section  352  also rotates as a unit. The proximal facing side of the head  366  can have an angled surface  372  configured to slide against the angled surfaces  324  of the upper structure  302  and lower structure  304 , as illustrated in  FIGS. 20 and 21 . 
     The proximal section  350  and the distal section  352  can be rotatably linked with a keyed coupling, such that when the proximal section  350  is rotated, the distal section  352  also rotates as a unit. The shaft  370  on the distal section  352  can have a keyed shape that slideably engages with the bore  356 , on the proximal section  350 , which has a matching keyed shape. In the embodiment illustrated in  FIG. 21 , the shaft  370  has a square cross-sectional shape that slideably engages a bore  356  having a square cross-sectional shape. Other suitable shapes or geometric configurations for a keyed connection between the proximal section  350  and distal section  352  may be used in the screw mechanism  306  to achieve the desired results, such as triangular, hexagonal, oval, star-shaped, or other non-circular shape. 
     In use, the drive interface  361  can be actuated to compress the screw mechanism  306 , which engages the upper structure  302  and lower structure  304  to move the two structures away from each other from the collapsed configuration to the expanded configuration. If desired, the drive interface  361  may be actuated in the opposite direction to change the interbody device  300  from the expanded configuration back to the collapsed configuration. This allows the expandable interbody device  300  to be moved to another location or repositioned if it is expanded in the wrong location and needs to be collapsed prior to moving or repositioning. 
     With reference to  FIGS. 20 and 21 , the screw mechanism  306  can vary in length to change the interbody device from the collapsed configuration to the expanded configuration. Initially, the length of the screw mechanism  306  can be L5 in the collapsed configuration, shown in  FIG. 20 . As the drive interface  361  is rotated in a first direction, the proximal section  350  and the distal section  352  are screwed into the coupler  380  and the length of the screw mechanism  306  contracts to L6 in the expanded configuration, shown in  FIG. 21 . The protrusions  386  on the coupler  380  are constrained in the apertures  388 ,  390  on the upper structure  302  and lower structure  304  to prevent the coupler  380  from rotating with the proximal section  350  and distal section  352  as the drive interface  361  is rotated. By reversing rotation of the drive interface  361  in a second direction, opposite the first, the screw mechanism  306  can be extended in length from L6 back to L5, if desired. 
     In the embodiment illustrated in  FIGS. 20 and 21 , in the collapsed configuration the expandable interbody device  300  has a distance of H5. The angled surface  364  of the proximal section  350  can contact the proximal ramp portions  324  of the upper structure  302  and lower structure  304 . The angled surface  372  of the distal section  352  can engage the distal ramp portions  324  of the upper structure  302  and lower structure  304 . When the drive interface  361  is rotated in a first direction, the proximal section  350  and the distal section  352  can move toward each other from L5 to L6, as explained above. When this happens, the angled surfaces  364  and  372  can push against the angled surfaces  324  of the upper structure  302  and lower structure  304 , causing the upper structure  302  and lower structure  304  to separate. The distance between the upper structure  302  and the lower structure  304  can increase from H5 (collapsed configuration) to H6 (expanded configuration). The expandable interbody device  300  does not have to be completely expanded to H6 and may only be expanded to a partial distance between H5 and H6, depending on the expansion needed between the adjacent vertebrae. The proximal and distal angled surfaces  324  can have features that increase resistance to turning of the screw mechanism  306 , so that increased actuating forces are required during select portions of the expansion procedure. This variation of actuating forces can provide tactile feedback to the surgeon as an indication of expansion position of the expandable interbody device  300 , such as when the interbody device  300  is nearing the limits of its expansion. 
     As mentioned above, the threaded portion  358  of the proximal section  350  can engage with the proximal hole  382  of the coupler  380  and the threaded portion  368  of the distal section  352  can engage with the distal hole  384  of the coupler  380 . The proximal hole  382  and distal hole  384  can have thread patterns in opposite directions and the thread portions  358 ,  368  can have corresponding thread patterns in opposite directions. In some embodiments, the proximal and distal holes  382 ,  384  and the thread portions  358 ,  368  may have equal pitch, such that during expansion, the proximal side and distal side of the upper structure  302  and lower structure  304  translate or move at the same rate. In other embodiments, the proximal hole  382  and threaded portion  358  of the proximal section  350  may have a different pitch than the distal hole  384  and threaded portion  368  of the distal section  352 , such that during expansion, the proximal side and distal side of the upper structure  302  and lower structure  304  translate or move at different rates. For example, the proximal side of the upper structure  302  and lower structure  304  may translate or move at a first rate of speed and the distal side of the upper structure  302  and lower structure  304  may translate or move at a second rate of speed. The first rate of speed may be faster or slower than the second rate of speed. This allows for some angularity between the upper structure  302  and lower structure  304  during expansion. The difference between the first and second rates of speed allows the user to select an expandable interbody device that has some angulation after expansion, for example to account for the lordotic curvature of the spine. 
     The screw mechanism  306  or portions of the screw mechanism  306  can be fabricated from any biocompatible material suitable for implantation in the human spine, such as metals including, but not limited to, stainless steel, titanium and titanium alloys, as well as surgical grade plastics, plastic composites, ceramics, bone, and other suitable materials. In some embodiments, the proximal section  350  and the distal section  352  may be formed of a porous material that participates in the growth of bone with the adjacent vertebral bodies. In some embodiments, the screw mechanism  306  can include a roughened surface that is coated with a porous material, such as a titanium coating, or the material may be chemically etched to form pores that participate in the growth of bone with the adjacent vertebra. In some embodiments, only portions of the screw mechanism  306  may be formed of a porous material, coated with a porous material, or chemically etched to form a porous surface, such as the head  360  of the proximal section  350  and head  366  of the distal section  352 , which may be exposed to the native anatomy after implant. In some embodiments, the surface porosity may be between 50 and 300 microns. 
     In some embodiments, the screw mechanism may be a compression screw having a proximal section threadably coupled to a distal section, the proximal section having a threaded shaft and the distal section having a threaded bore, or vice-versa, such that when the proximal section is rotated, the threaded shaft engages the threaded bore to shorten or lengthen the distance between the proximal head and the distal head. The distal section can have anti-rotational features, such as for example an oblong head shape, to prevent it from rotating as the proximal section is engaged with distal section. 
     With reference to  FIG. 22 , a deployment tool  400  can be used to implant the interbody device  300  into the patient. In use, an incision  10  can be made on the patient to allow access to the implant site in the intervertebral space  20 . The incision can be made for implanting the device from the posterior, lateral or anterior directions. The incision can be small for a minimally invasive procedure or a larger incision can be used for an open surgery. Once the implant site is accessed, the two adjacent vertebrae  30  can be distracted in some situations to open up the intervertebral space  20 . In some situations, the expandable interbody device  300  can be used to at least partially distract the vertebrae during the implant procedure. In some situations, the intervertebral space  20  may include a degenerated disc or other disorder that may require a partial or complete discectomy prior to insertion of the expandable interbody device  300 . 
     In some configurations, more than one expandable interbody device  300  can be implanted between the adjacent vertebrae of the patient. In such embodiments, multiple expandable interbody devices  300  can be placed in a side-by-side configuration or any other suitable configuration, thereby creating additional support. 
     With reference to  FIG. 23 , the deployment tool  400  can have an elongate shaft  406  with a coupling feature toward the distal side  401  that is configured to secure an interbody device  300 . The proximal side  403  of the deployment tool  400  can include a handle  408  attached to the shaft  406 . A hollow sleeve  410  can be disposed over the shaft  406  such that the longitudinal axis of the shaft  406  is generally coincident with the longitudinal axis of the sleeve  410 . The sleeve  410  is movably attached to the shaft  406  and is configured to translate along the longitudinal axes. An actuation device  420  can extend through the length of the deployment tool  400  such that a drive of the actuation device  420  is at the distal side  401  and a knob is toward the proximal side  403 . 
     The coupling feature includes arms  402  or clamps that engage with the recesses  320  of the lower structure  304  of the interbody device  300 . As shown in the close-up views of  FIGS. 25A-B , the arms  402  can have protrusions  404  that are configured to be retained by the recesses  320  of the interbody device  300 . The arms  402  can be moved from an open configuration to a closed configuration by manipulation of a translation mechanism  412 . In the open configuration, illustrated in  FIG. 25A , the sleeve  410  is in its proximal position, allowing the arms  402  to be spread apart sufficiently to fit around the interbody device  300 . In the closed configuration, illustrated in  FIG. 25B , the sleeve  410  is in its distal position and the walls of the sleeve  410  can compress the arms  402  together around the interbody device  300 .  FIG. 26  shows a close-up view of the arms  402  of the deployment tool  400  coupled to a interbody device  300 . The arms  402  can have protrusions  404  that engage the recesses  320  on the interbody device  300 . In some configurations, the arms  402  can have rails that engage with slots on the interbody device  300 . 
     In other embodiments, the deployment tool can be coupled to the interbody device through other mechanisms, such as rotational (e.g., threaded) engagement, temporary adhesives, clips, hooks, and the like. The deployment tool  400  can include any of a variety of suitable attachment features to couple the deployment tool  400  to the interbody device  300 . 
     With continued reference to  FIG. 23 , the sleeve  410  can have a translation mechanism  412  toward the proximal end that is configured to actuate the coupling feature. In the illustrated embodiment, the translation mechanism  412  is manipulated by rotation to move the sleeve  410  longitudinally relative to the shaft  406 . In some configurations, the translation mechanism  412  and the distal part of the sleeve  410  can be rotatably coupled such that rotation of the translation mechanism  412  is translated to linear movement of the distal part of the sleeve  410 . In other configurations, the translation mechanism  412  may be rigidly connected to the distal part of the sleeve  410  such that the entire sleeve  410  rotates as it translates. The inner surface of the translation mechanism  412  can have threads that engage threads  414  on the shaft  406 , as illustrated in  FIG. 24 . The threaded coupling between the shaft  406  and the sleeve  410  may provide increased mechanical advantage for securing the arms  402  around the interbody device  300 . 
     In some configurations, the sleeve  410  can be slideably connected to the shaft  406 , in which case the sleeve  410  is manipulated by pushing and pulling. Other means of coupling the sleeve to the shaft such that an actuation of the translation mechanism results in a desired corresponding movement of the sleeve are possible and are considered within the scope of the disclosure. The deployment tool  400  can be straight or curved or a combination of these shapes. In some configurations, the deployment tool can have a variable angle shaft such that the shape of the tool can be adjusted during use. For example, the deployment tool can have a hinge that adjusts the bend angle of the shaft for improved fitment of the deployment tool through the incision and to the target implant site. The deployment tool  400  can be stiff, bendable, or partially stiff and partially bendable. In still other embodiments, a power source may be provided for hydraulic, pneumatic or other power-assisted manipulation of the sleeve  410 . 
     With continued reference to  FIG. 23 , the deployment tool  400  can include an actuation device  420  that extends the length of the deployment tool  400  for actuating the drive interface  361  from the proximal portion of the deployment tool  400 . The actuation device  420  can have a distal portion configured to engage the drive interface  361  of the proximal section  350  of the screw mechanism  306 , and a proximal portion for actuation. For example, the embodiment illustrated in  FIG. 27  shows an actuation device  420  with an elongate shaft  422  that extends the length of the deployment tool  400 . A knob  424  can be disposed at the proximal end of the shaft  422  to enable the user to rotate the actuation device  420 . In other configurations, the proximal end can have a lever, flat protrusion, drive interface or other suitable rotational mechanism for manipulating the actuation device. The distal end of the shaft  422  can have a drive  426  configured to engage the drive interface  361 . For example, the drive  426  can be a hexagonal-shaped driver, or any other shape that is complementary to the drive interface  361  cavity of the screw mechanism  306 . 
     In operation, the actuation device  420  can be placed through a passageway extending through the center of the deployment tool  400 , as illustrated in the cross-sectional view of  FIG. 28 . After the expandable interbody device  300  is inserted and positioned within the intervertebral space  20  between two vertebrae  30 , the actuation device  420  can be used to deploy and expand the expandable interbody device  300  by applying a rotational force to the actuation device  420 . By rotating the knob  424  at the proximal portion of the deployment tool  400 , the drive  426  is also rotated, which in turn rotates the drive interface  361  of the screw mechanism  306  and expand the interbody device  300 . 
     As the deployment tool  400  applies the rotational force, the expandable interbody device  300  gradually expands as described above. The interbody device  300  can be expanded until it contacts the two adjacent vertebrae. In some configurations, the interbody device  300  can be used to distract the two adjacent vertebrae and open up the intervertebral space  20 . The actuation device  420  can advantageously transmit sufficient torque to the screw mechanism  306  to enable distraction using the interbody device  300 . In some configurations, the actuation device  420  can have a torque-limiting feature to prevent over-tightening of the screw mechanism  306 . For example, the torque-limiting feature can include a spring-loaded clutch mechanism along the shaft  422  of the actuation device  420  that can only transmit a predetermined amount of torque before the clutch slips. The amount of torque that can be transmitted can depend on the stiffness of the clutch spring. In other embodiments, the torque-limiting feature can be a portion of the shaft  422  that is configured to break at a predetermined torque. In other embodiments, the feature can be any functional torque-limiting device. 
     In some embodiments, the deployment tool  400  can be used to deliver fluids, medication or other materials, especially materials that can help in the integration of the interbody device with the vertebrae, such as allograft, Demineralized Bone Matrix (“DBM”) packing, and/or other bone graft material. The material can also fill up the empty cavity created between the upper structure  302  and lower structure  304  upon expansion, helping to provide support to the vertebrae. 
     With reference to  FIG. 29 , a delivery tube  430  can extend the length of the deployment tool  400  from the proximal side  403  of the deployment tool  400  to the proximal section of the screw mechanism  306 . The delivery tube  430  can have a channel  432  extending the length of the delivery tube  430  and open at the distal end so that it is in fluid communication with the drive interface  361  of the proximal section  350  of the screw mechanism  306 . In some embodiments, the delivery tube  430  is the same as the actuation device except with a channel extending longitudinally through it. The actuation device  420  can be a separate component that is removed from the deployment tool  400  to insert the delivery tube  430 . In some embodiments, the delivery tube  430  and actuation device  420  are the same component that serves both functions. For example, the actuation device can have a distal end configured to engage the drive interface  361  and a channel extending through its length. 
     In some configurations, the material is forced through the delivery channel  432  by a pressurized delivery system. For example, a powered compressor can be attached to the proximal end of the delivery tube  430  to push material through the delivery channel  432  and into the cavity of the interbody device  300 . In some configurations, the fluids, medication or other material is delivered to the interbody device  300  by manually pushing the material through the delivery tube, for example by using a push rod. The push rod can be an elongate shaft that closely fits the inside diameter of the delivery channel. The push rod can have a force multiplier to provide increased mechanical advantage for pushing the material through the delivery channel. For example, the push rod can be threadedly engageable with the delivery tube such that the material is pressed through the delivery channel as the push rod is screwed onto the delivery tube. In another example, the push rod can include a ratcheting handle that provides leverage to help push material through the delivery channel. 
     With reference to  FIGS. 30 and 31 , the proximal section  350  of the screw mechanism can have injection holes  359  that extend from the drive interface  361  to the angled surface  364 . The proximal section  350  can have one, two, three, or more injection holes  359 . In the illustrated embodiment, the injection holes  359  are round holes. In other embodiments, the injection holes can be any of a variety of shapes, such as square, oval or polygonal. The injection holes can provide fluid communication between the delivery channel  432  and the interior of the interbody device  300 . In the illustrated embodiment of  FIG. 23 , the delivered material travels through the channel  432 , into the drive interface  361 , through the injection holes  359  and into the cavity between the upper structure  302  and lower structure  304 . The material can fill up the cavity and also travel through the slots  318  in the upper structure  302  and the slots  336  in the lower structure  304  to come into contact with the vertebrae. 
     As illustrated in cross-sectional top view of  FIG. 32 , the fluids, medication or other materials can be delivered through the arms  402 ′ of the deployment tool  400 ′. Channels  432 ′ can extend through the arms  402 ′ and have an opening at the tips of the arms  402 ′. When the deployment tool  400 ′ is coupled with the interbody device  300 , the opening in the arms  432 ′ can be positioned in the recesses  320  of the lower structure  304 , placing the channels  432 ′ in fluid communication with the interior cavity of the interbody device  300 . This configuration advantageously allows the materials to be delivered to the interbody device  300  through existing components without having to introduce a separate pathway. 
     The deployment tool can be made of any appropriate material for the particular part. Materials can include, but are not limited to, stainless steel, surgical steel, cutlery steel, tool steel, cobalt and its alloys, nickel and its alloys, chromium and its alloys, titanium and its alloys, zirconium and its alloys, aluminum and its alloys, magnesium and its alloys, polymers, elastomers, and ceramics. Ceramics may include, but are not limited to silicon carbide, silicon oxide(s), silicon nitride, aluminum oxide, alumina, zirconia, tungsten carbide, other carbides. 
     The sizes of the interbody device and deployment tool are appropriate for treating the particular bone. Smaller devices can be used for smaller vertebra and larger devices for larger vertebra. In addition, the device can be used on bones other than the vertebra and on bones for humans and non-humans. 
     A method of implanting the interbody device  300  comprises coupling the interbody device  300  to the deployment tool  400 . The deployment tool  400  can engage the interbody device  300  by manipulating the translation mechanism  412  to clamp the arms  402  onto the recesses  320 . An incision  10  can be made on the patient to allow access to the implant site in the intervertebral space  20 . The incision can be made for implanting the device from the posterior, lateral or anterior directions. The incision can be small for a minimally invasive procedure or a larger incision can be used for an open surgery. In some situations, two adjacent vertebrae  30  can be distracted to open up the intervertebral space  20 . In some configurations, the expandable interbody device  300  can be used to at least partially distract the vertebrae during the implant procedure. 
     A user can hold the handle  408  of the deployment tool  400  to implant the interbody device  300  in the intervertebral space  20 . Once the interbody device  300  is positioned between adjacent vertebrae, the actuation device  420  can be rotated to turn the drive  426  and engage the screw mechanism  306 . The screw mechanism  306  changes length from a first length to a second length such that the proximal frustoconical surface  364  engages the upper proximal angled surface and the lower proximal angled surface, and the distal frustoconical surface  372  engages the upper distal angled surface and the lower distal angled surface to expand the upper structure  302  and the lower structure  304  from a first distance to a second distance. 
     In some embodiments, materials such as fluids, medication, bone graft material, allograft and/or Demineralized Bone Matrix (DBM) can be delivered to the interior cavity of the interbody device  300 . The material can be delivered through a delivery tube  430  and into the proximal section  350  of the screw mechanism  306  or through the arms  402  of the deployment tool. In other embodiments, the material can be delivered through other paths to reach the cavity of the interbody device  300 . 
     To release the interbody device  300 , the translation mechanism  412  is rotated. Rotation motion of the translation mechanism  412  is transferred to the sleeve  410  as a linear motion away from the arms  402  via the threaded connection. The arms  402  can move apart to release the interbody device  300  and allow removal of the deployment tool  400  from the patient. 
     In some configurations, more than one expandable interbody device  300  can be implanted between the adjacent vertebrae of the patient. In such embodiments, multiple expandable interbody devices  300  can be placed in a side-by-side configuration or any other suitable configuration, thereby creating additional support. 
     In some embodiments of the deployment tool  400 , the movement of the translation mechanism  412  and/or actuation device  420  can be effected by manual force applied by a person, such as by his or her hands, or alternatively it can be supplied or supplemented with a motor, pneumatics, hydraulics, springs, and/or magnetics. Some embodiments of the tool may comprise a squeeze handle for actuating the tool. Other embodiments of the tool can include closing mechanisms that include compound leverage, ratcheting, and/or multistep closing. 
     Although certain embodiments, features, and examples have been described herein, it will be understood by those skilled in the art that many aspects of the methods and devices illustrated and described in the present disclosure may be differently combined and/or modified to form still further embodiments. For example, any one component of the device illustrated and described above can be used alone or with other components without departing from the spirit of the present disclosure. Additionally, it will be recognized that the methods described herein may be practiced in different sequences, and/or with additional devices as desired. Such alternative embodiments and/or uses of the methods and devices described above and obvious modifications and equivalents thereof are intended to be included within the scope of the present disclosure. Thus, it is intended that the scope of the present disclosure should not be limited by the particular embodiments described above, but should be determined only by a fair reading of the claims that follow.