Abstract:
An expandable fusion device capable of being inserted between adjacent vertebrae and expanded laterally to facilitate the fusion process and the use of such device. The expandable fusion device can expand laterally such that it expands the cross-sectional support area of the device to provide more stable support of the support the spine and maintain the normal spacing between opposing vertebrae. The interior area of the expandable fusion device (in which the bone graft can be packed) does not decrease (and generally increases) during expansion of the device. This facilitates pre-packing of the expandable fusion device before utilization.

Description:
FIELD OF INVENTION 
     An expandable fusion device for promoting an intervertebral fusion, and more particularly, an expandable fusion device capable of being inserted between adjacent vertebrae and expanded laterally to facilitate the fusion process. 
     BACKGROUND OF INVENTION 
     The spine is the axis of the skeleton on which all of the body parts hang. In humans, the normal spine has seven cervical, twelve thoracic and five lumbar segments. The lumbar spine sits upon the sacrum, which then attaches to the pelvis, and in turn is supported by the hip and leg bones. The bony vertebral bodies of the spine are separated by intervertebral discs, which act as joints but allow known degrees of flexion, extension, lateral bending, and axial rotation and translation. 
     Typical vertebra has a thick anterior bone mass called the vertebral body, with a neural (vertebral) arch that arises from the posterior surface of the vertebral body. The central of adjacent vertebrae are supported by intervertebral discs. The spinal disc and/or vertebral bodies may be displaced or damaged due to trauma, disease, degenerative defects, or wear over an extended period of time. One result of this displacement or damage to a spinal disc or vertebral body may be chronic back pain. In many cases, to alleviate back pain from degenerated of herniated discs, the disc is removed along with all or part of at least one neighboring vertebrae and is replaced by an implant that promotes fusion of the remaining bony anatomy. 
     The success or failure of spinal fusion may depend upon several factors. For instance the spacer or implant or cage used to fill the space left by the removed disc and bony anatomy must be sufficiently strong to support the spine under a wide range of loading conditions. The spacer should also be configured so that it likely to remain in place once it has been positioned in the spine by the surgeon. Additionally the material used for the spacer should be biocompatible material and should have a configured that promotes bony ingrowth. 
     Cages have been developed to help support the spine and maintain the normal spacing between opposing vertebrae. Typically, cages are pre-manufactured at various heights requiring that a cavity between opposing vertebrae be prepared and distracted to a dimension corresponding to the most suitably sized cage. The surgical procedure to prepare the implant site can be difficult and lengthy. Moreover, the procedure can increase risk of trauma to the tissues surrounding of the implant site. 
     Distractible cages may be used as both a fusion device and/or a means for maintaining intervertebral spacing. Often these implants include a drive means that allows the cage to be expanded in situ to a size that corresponds to the cavity created when the damaged tissue is removed. The drive means typically includes devices such as gears, threaded rods, and the like, in mechanical engagement so as to expand or contract the device to a necessary distance between the vertebrae. 
     There are a number of known conventional fusion devices and methodologies in the art for accomplishing the intervertebral fusion. These include screw and rod arrangements, solid bone implants, and fusion devices which include a cage or other implant mechanism which, typically, is packed with bone and/or bone growth inducing substances (i.e., bone graft). These devices are implanted between adjacent vertebral bodies in order to fuse the vertebral bodies together, alleviating the associated pain. Examples of such fusion devices are taught and described the following U.S. Pat. Nos. 6,830,589, 8,062,375, 8,435,298, 8,518,087, and 8,556,979 and the 
     There are drawbacks associated with the known conventional fusion devices and methodologies. For example, while current expandable cages are designed to expand in height, their lateral profile remains the same (or is decreased) as they are expanded. Accordingly, there is a need for expandable fusion devices that expand laterally and a further need for expandable fusion devices that can expand laterally. 
     Moreover, it is advantageous to pack cages with bone graft. In view of the gears, threaded rods, and the like various used to expand the cages, packing such bone graft is more difficult. Accordingly, there is a need for an improved expandable fusion device that has the open volume for the bone graft and openings (i.e., graft windows) that render this open volume readily accessible. 
     SUMMARY OF INVENTION 
     The present invention is an expandable fusion device capable of being inserted between adjacent vertebrae and expanded laterally to facilitate the fusion process. In some embodiments of the present invention, the expandable fusion device expands laterally. The expandable fusion device can expand laterally such that it expands the cross-sectional support area of the device to provide more stable support of the support the spine and maintain the normal spacing between opposing vertebrae. The interior area of the expandable fusion device (in which the bone graft can be packed) does not decrease (and generally increases) during expansion of the device. This facilitates pre-packing of the expandable fusion device before utilization. 
     In general, in one aspect, the invention features an expandable fusion device that includes a main body. The main body has having an axis that runs from the back to the front of the main body, a left side, an a right side. The expandable fusion device further includes a left lateral expandable body connected to the main body and capable of moving outwardly from the left side of the main body while the left lateral expandable body remains parallel to the axis of the main body. The expandable fusion device further includes a right lateral expanding body connected to the main body and capable of moving outwardly from the right side of the main body while the left lateral expandable body remains parallel to the axis of the main body. The expandable fusion device further includes a guide body that is operable for moving within the main body along the main axis in which (i) the movement of the guide body in a first direction moves the left lateral expandable body and the right expandable body outward relative to the main body, and (ii) the movement of the guide body in a second direction (which is opposite to the first direction) moves the left lateral expandable body and the right expandable body inward relative to the main body. The expandable fusion device has an interior space formed from the main body, left lateral expanding body, and the right lateral expanding body. The interior space is adapted to be packed with bone growth inducing substances. 
     Implementations of the invention can include one or more of the following features: 
     The expandable fusion device can expand and contract without changing the height of the expandable fusion device. 
     The interior space of the expandable fusion device can be unreduced as the guide body is moved in the first direction. 
     The expandable fusion device has a width that can be increased between 1 mm and 6 mm as the guide body is moved in the first direction. 
     The expandable fusion device has a width that can be increased between 10% and 60% as the guide body is moved in the first direction. 
     The expandable fusion device can have a lateral length that does not change as the guide body is moved in the first direction and the second direction. 
     The lateral length can be between 22 mm and 28 mm. 
     The expandable fusion device can have a height that does not change as the guide body is moved in the first direction and the second direction. 
     The height can be between 8 mm and 14 mm. 
     The left lateral expandable body can be movably connected to the main body using a first left guide pin and a second left guide pin. The right lateral expandable body can be moveable connected to the main body using a first right guide pin and a second right guide pin. 
     The first left guide pin and second left guide pin can be attached to the left lateral expandable body. The main body can have a left horizontal channel and can be operable to permit the first left guide pin to move within the left horizontal channel in a horizontal direction that is perpendicular to the axis of the main body. The guide body can have a left diagonal channel and can be operable to permit the second left guide pin to move within the left diagonal channel in a diagonal direction such that the left lateral expandable body moves outward and inward as the guide body is moved along the axis of the main body. The first right guide pin and the second right guide pin can be attached to the right lateral expandable body. The main body can have a right horizontal channel and can be operable to permit the first right guide pin to move within the right horizontal channel in the horizontal direction. The guide body can have a right diagonal channel and can be operable to permit the second right guide pin to move within the right diagonal channel in a diagonal direction such that the right lateral expandable body moves outward and inward as the guide body is moved along the axis of the main body. 
     The expandable fusion device can further include a translation body that is movably connected to the guide body. The rotation of the translation body can be capable of moving the guide body along the axis of the main body. 
     The rotation of the translation body in one rotational direction can be capable of moving the guide body in the first direction. The rotation of the translation body in an opposition rotational direction that is opposite the one rotation direction can be capable of moving the guide body in the second direction. 
     In general, in another aspect, the invention features a method of using an expandable fusion device. The method includes creating disc access to a position in the disc space at which the expandable fusion device will be utilized. The method further includes preparing the disc space for receiving the expandable fusion device at the position. The method further includes inserting the expandable fusion device in the disc space. The method further includes expanding the expandable fusion device such that the width of the expandable fusion device increases by at least 10%. The method further includes verifying the expandable fusion device is positioned at the position. 
     Implementations of the invention can include one or more of the following features: 
     The expandable fusion device can include a main body. The main body can have an axis that runs from the back to the front of the main body, a left side, and a right side. The expandable fusion device can further include a left lateral expandable body connected to the main body and can be capable of moving outwardly from the left side of the main body while the left lateral expandable body remains parallel to the axis of the main body. The expandable fusion device can further include a right lateral expanding body connected to the main body and can be capable of moving outwardly from the right side of the main body while the left lateral expandable body remains parallel to the axis of the main body. The expandable fusion device can further include a guide body that can be operable for moving within the main body along the main axis in which (i) the movement of the guide body can be in a first direction that moves the left lateral expandable body and the right expandable body outward relative to the main body, and (ii) the movement of the guide body can be in a second direction (that is opposite to the first direction) that moves the left lateral expandable body and the right expandable body inward relative to the main body. The expandable fusion device can have an interior space formed from the main body, left lateral expanding body, and the right lateral expanding body. The interior space can be adapted to be packed with bone growth inducing substances. 
     The expandable fusion device can expand without changing the height of the expandable fusion device. 
     The interior space of the expandable fusion device can be unreduced during the step of expanding. 
     The expandable fusion device can have a width that increases between 1 mm and 6 mm during the step of expanding. 
     The expandable fusion device can have a width that increases between 10% and 60% during the step of expanding. 
     The expandable fusion device can have a lateral length that does not change during the step of expanding. 
     The lateral length can be between 22 mm and 28 mm. 
     The expandable fusion device can have a height that does not change during the step of expanding. 
     The height can be between 8 mm and 14 mm. 
     The left lateral expandable body can be movably connected to the main body using a first left guide pin and a second left guide pin. The right lateral expandable body can be moveable connected to the main body using a first right guide pin and a second right guide pin. 
     The first left guide pin and second left guide pin can be attached to the left lateral expandable body. The main body can have a left horizontal channel and the first left guide pin can move within the left horizontal channel in a horizontal direction that is perpendicular to the axis of the main body during the step of expanding. The guide body can have a left diagonal channel and the second left guide pin can move within the left diagonal channel in a diagonal direction such that the left lateral expandable body can move outward as the guide body is moved along the axis of the main body during the step of expanding. The first right guide pin and the second right guide pin can be attached to the right lateral expandable body. The main body can have a right horizontal channel and the first right guide pin can move within the right horizontal channel in the horizontal direction. The guide body can have a right diagonal channel and the second right guide pin can move within the right diagonal channel in a diagonal direction such that the right lateral expandable body moves outward as the guide body is moved along the axis of the main body. 
     The expandable fusion device can further include a translation body that can be movably connected to the guide body. The step of expanding can include rotating the translation body to move the guide body along the axis of the main body. 
     The rotation of the translation body in one rotational direction can move the guide body in the first direction. The rotation of the translation body in an opposition rotational direction (that is opposite the one rotation direction) can move the guide body in the second direction. 
     The step of expanding can include rotating the translation body with an instrument coupled to the translation body. 
     The method can further include packing the expandable fusion device with bone growth inducing substances before the step of inserting. 
     The method can further include removing the expandable fusion device from the position after healing has occurred. 
     The foregoing has outlined rather broadly the features and technical advantages of the invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
     It is also to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG. 1A  is a perspective view of an embodiment of the present invention showing an expandable fusion device in a closed (fully contracted) position. 
         FIG. 1B  is a perspective view of the embodiment of  FIG. 1A  in an open (fully expanded) position. 
         FIG. 2A  is top view of the embodiment of  FIG. 1A  (in the closed position). 
         FIG. 2B  is a top view of the embodiment of  FIG. 1B  (in the open position). 
         FIG. 2C  is a right side lateral view of the embodiment of  FIG. 1A . 
         FIG. 3  is an exploded view of the embodiment of  FIG. 1A . 
         FIG. 4  is a perspective view of the main body of the embodiment of  FIG. 1A . 
         FIG. 5A  is a perspective view of the left lateral expandable body of the embodiment of  FIG. 1A . 
         FIG. 5B  is a side view of the left lateral expandable body of the embodiment of  FIG. 1A . 
         FIG. 5C  is a top view of the left lateral expandable body of the embodiment of  FIG. 1A . 
         FIG. 5D  is a different perspective view of the left lateral expandable body of the embodiment of  FIG. 1A . 
         FIG. 5E  is a third perspective view of the left lateral expandable body of the embodiment of  FIG. 1A  (which unlike the perspective views of  FIG. 5A  and  FIG. 5D  is from the back side of the left lateral expandable body. 
         FIG. 6  is a perspective view of the right lateral expandable body of the embodiment of  FIG. 1A  (with guide pins). 
         FIG. 7  is a perspective view of the right lateral expandable body of the embodiment of  FIG. 1A  (with guide pins, translation body, and guide body). 
         FIG. 8A  is a perspective view of the embodiment of  FIG. 1A  (in the closed position) with the insert device. 
         FIG. 8B  is a perspective view of the embodiment of  FIG. 1A  (in the open position) with the insert device (and without the left lateral expanding body). 
         FIG. 9  is a flowchart of a surgical technique using the embodiment of  FIG. 1A . 
         FIGS. 10A-10F  are illustrations of from portions of the surgical technique shown in the flowchart of  FIG. 9 . 
         FIG. 11  are illustrations of instruments that can be used in conjunction with the embodiment of  FIG. 1A  during a surgical technique. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is an expandable fusion device for promoting an intervertebral fusion and the method of using such a device. The expandable fusion device is capable of being inserted between adjacent vertebrae and expanded laterally to facilitate the fusion process. 
     Expandable Fusion Device 
     Referring to the figures,  FIG. 1A  is a perspective view of an expandable fusion device  100  in a closed (fully contracted) position. (An exploded view of expandable fusion device  100  is shown in  FIG. 3 ). Expandable fusion device  100  has a left lateral expandable body  101 , a right lateral expandable body  102 , and a main body  103 . The front section  108  of expandable fusion device  100  is a tapered nose that aides in the insertion of the expandable fusion device  100 . Above the tapered nose can be seen the tops of guide pins  104   a  and  104   b . As shown in later figures, guide pins  104   a  and  104   b  are in horizontal guide channels  304   a  and  304   b  of main body  103  (shown in  FIG. 3 ). Toward the back section of the expandable fusion device can be seen the tops of guide pins  105   a  and  105   b . Guide body  106  is shown in the back section also. As shown in later figures, the guide pins  105   a  and  105   b  are in diagonal guide channels  305   a  and  305   b  of guide body  106  (shown in  FIG. 3 ). Interior space  107  is formed by the left lateral expandable body  101 , a right lateral expandable body  102 , and a main body  103 . Such void space  107  is accessible for packing bone graft. 
       FIG. 1B  is a perspective view of expandable fusion device  100  in an open (fully expanded) position. As the guide body  106  moves forward relative to expandable fusion device  100 , guide pins  105   a  and  105   b  are in diagonal guide channels  305   a  and  305   b  of guide body  106  thereby causing the left lateral expandable body  101  to move outward to the left and right lateral expandable body  102  to move outward to the right relative to main body  103 . Left lateral expandable body  101  and right lateral expandable body  102  remains parallel to main body parallel because guide pins  104   a  and  104   b  in the front ends of left lateral expandable body  101  and right lateral expandable body  102 , can move horizontally outward in guide channels  304   a  and  304   b  of main body  103 . Accordingly, as guide body  106  moves forward (relative to main body  103 ) the expandable fusion device expands, and as guide body  106  moves backwards (relative to main body  103 ) the expandable fusion device contracts. In alternative embodiments, guide body  106  is designed to move backward (relative to main body  103 ) to expand expandable fusion device  100 , and is designed to move forward (relative to main body  103 ) to contract expandable fusion device  100 . 
     Accordingly, the expandable fusion device  100  can be positioned anywhere between fully closed and fully opened. This permits the expandable fusion device  100  to be expanded by the practitioner based upon the needs of the patient. Typically, the expandable fusion device  100  can vary between 1 mm and 6 mm from its fully closed and fully open positions. In some embodiments, the expandable fusion device can increase in its width by between 10% and 60%. 
     The lateral length of the expandable fusion device  100  does not change with the expanded movement of the expandable fusion device  100 . Typically, the lateral length is between 22 mm and 28 mm. However, any lateral length can be utilized in the present invention. 
     The height of the expandable fusion device  100  also does not change with the expanded movement of the expandable fusion device  100 . Typically, the height is between 8 mm and 14 mm. However, any height can be utilized in the present invention. The lateral length and height utilized will often depend on the patient to which the expandable fusion device  100  is being utilized. The height is measured as the greatest distance from the top side to the bottom side (perpendicular to the length and width). For some embodiments of extendable fusion devices, the height is generally consistent (not including the teeth, such as teeth  201  shown in  FIG. 2C ), i.e., the top and bottom are generally parallel to one another. This is referred to as parallel orientation and also referred to as in 0°.  FIG. 2C  shows an expandable fusion device in 0° (parallel orientation). In other embodiments of extendable fusion devices, the height generally decreases from front to back (not including the teeth). For instance, the expandable fusion device can have a slant of 7° (which is referred to as a lordotic orientation). The slant of the expandable fusion device is selected to correspond with lordosis tilt angle for the position at which the expandable fusion device is to be used. 
       FIG. 2A-2B  are top views of expandable fusion device  100  (in the closed and open positions, respectively). Translation body  202  is shown at the back portion of the expandable fusion device  100 , which can be rotated to move guide body  106  forward and back. As shown in more detail in  FIG. 3 , translation body  202  has threads that couple the inside threads in hole  310  of main body  103 . As translation body  202  rotates, this moves section  309  along the axis of the main body  103 . Section  309  is coupled to guide block  106  via connector  307 . This allows section  109  to spin within guide block  106  and also moves guide block  106  back and forth relative to the movement of section  109  along the axis of main body  103 . Accordingly, by rotating translation body  202 , guide block  106  can move forward and backward relative to the axis of main body  103 . Again, by such movement of the guide block  106 , this moves the left lateral expandable body  101  and right lateral expandable body  102  simultaneously outward (or inward) relative to main body  103 . 
       FIG. 2C  is a right side lateral view of expandable fusion device  100 . As shown in this figure, right side expandable body  102  has teeth  201  that aggressively secure fixation of the device  100  when used. Left side expandable body  101  also has teeth  201 . 
       FIG. 3  is an exploded view of expandable fusion device  100 , which more clearly shows the various components of device  100 . These components include: 
     Left lateral expanding body  101 . 
     Right lateral expanding body  102 . 
     Main body  103 . 
     Guide Pins  104   a  and  104   b.    
     Guide Pins  105   a  and  105   b.    
     Guide body  106 . 
     Translation body  202 . 
     Top guide pin holes  301   a  and  301   b  (which are used for guide pins  104   a  and  104   b , respectively). While not shown in this figure, there is a corresponding bottom pin holes that are also used for guide pins  104   a  and  104   b , respectively. See, e.g., bottom pin hole  501   a  in  FIG. 5D . 
     Top guide pin holes  302   a  and  302   b  (which are used for guide pins  105   a  and  105   b , respectively). 
     Bottom guide pin holes  303   a  and  303   b  (which are used for guide pins  105   a  and  105   b , respectively). 
     Horizontal guide channels  304   a  and  304   b  (which are used for guide pins  104   a  and  104   b , respectively). 
     Diagonal guide channels  305   a  and  305   b  (which are used for guide pins  105   a  and  105   b , respectively). 
     Hole  306  (in guide body  106 ). 
     Connector  307  (positioned in interior of hole  306 ). 
     Rotational coupler  308  (of translation body  202 ). 
     Section  309  (of translation body  202 ). 
     Hole  310  of main body  103 . 
     Graft window  311  of left lateral expanding body  101 . 
     Graft window  312  of right lateral expanding body  102 . 
     Graft windows  313  of main body  103 . 
       FIG. 4  is a perspective view of main body  103 . This illustrates the interior space  107  and shows how it is open at the top, bottom, and also at graft windows  313 . This allows the bone graft (the grafting materials) to be packed with the interior space  107  and be open and exposed to the vertebrae during the healing process.  FIG. 4  also shows the horizontal guide channels  304   a  and  304   b  in which guide pins  104   a  and  104   b , respectively, can move horizontally (as the left lateral expanding body  101  and right lateral expanding body  102  move horizontally inward and outward relative to main body  103 ).  FIG. 4  also shows hole  310  of main body  103  in which translation body  202  rotates about to move guide body  106  along the axis of main body  103 . 
       FIGS. 5A-5E  are various views of left lateral expandable body  101  of expandable fusion device  100 . Such views are, respectively, a perspective view, a side view, a top view, another perspective view (more from the top), and a third perspective view. Such views show top guide pin hole  301   a  and the corresponding bottom guide pin  501   a . (Right lateral expandable body has a bottom guide pin hole that corresponds to top guide pin hole  301   b ). Such views also show top pin guide hole  302   a  and the corresponding bottom pin guide hole  303   a . Such views also show graft window  311 . 
       FIG. 6  is a perspective view of the right lateral expandable body  102  of expandable fusion device  100 . This view includes guide pins  104   b  and  105   b  in place.  FIG. 7  is a perspective view of the right lateral expandable body  102  with guide pins  104   b  and  105   b , translation body  202 , and guide body  106 . Diagonal guide channel  305   a  (for guide pin  105   a ) is also shown in guide body  106 . 
       FIG. 8A  is a perspective view of expandable fusion device  100  (in the closed position) with inserter  1108  (shown in  FIG. 11 ) having inserter arms  801  and  802 . The inerter  1108  is capable of positioning the expandable fusion device  100  in place, and then keeping main body  103  in position (and stationary) as inserter  1108  is also used to couple with translation body  202 . This inserter  1108  can then rotate translation body  202 , thereby moving guide body  106 , which in turn moves left lateral expandable body  101  and right lateral expandable body  102  outward relative to the axis of main body  103 . 
       FIG. 8B  is a perspective view of expandable fusion device  100  (in the partially open position) with the inserter arms  801  and  802  (and without the left lateral expanding body  101 ). As shown guide body  106  has been moved further toward the front of main body  103  which then moves guide pins  105   a  and  105   b  within diagonal guide channels  305   a  and  305   b , respectively, which moves these guide pins  105   a  and  105   b  outward. 
     In some embodiments, the inserter  1108  does not include the rotating portion and a separate rotating tool that can couple with translation body  202  can be utilized. 
     Method of Using Expandable Fusion Device 
     The expandable fusion devices (such as expandable fusion device  100 ) can be used for spinal fusion surgery to provide support and structural stability at the fusion site following discectomy. Such expandable fusion devices can be used for spinal fusion, such as spinal fusion procedures in skeletally mature patients with degenerative disc disease (DDD) at one or two contiguous levels of the lumbosacral spine (L2-S1). DDD is defined as back pain of discogenic origin with the degeneration of the disc confirmed by history and radiographic studies. These patients generally should have had six months of non-operative treatment prior to treatment with an intervertebral cage (such as expandable fusion device  100 ). In addition, these patients may have up to Grade 1 spondylolisthesis or retrolisthesis at the involved levels. An expandable fusion device of the present invention with associated system can be used with supplemental fixation and autograft to facilitate fusion and is implanted via a posterior approach. 
     The footprint of expandable fusion devices of the present invention has a hollow center to accommodate bone graft. Expandable fusion device  100  is available in various heights to accommodate variability among patients and the inferior and superior surfaces are designed with ridges to improve fixation and stability and prevent back out and migration. The expandable fusion devices can include one or more tantalum markers per ASTM F560 for radiographic visualization. 
       FIG. 9  is a flowchart of a surgical technique using the expandable fusion device  100 .  FIGS. 10A-10G  are illustrations from this surgical technique. 
     In step  901 , the surgeon/practitioner performs preoperative planning. This includes determination of the appropriate height of the expandable fusion device  100  before the surgery. To achieve maximal segment stability, the implant should be selected having the largest possible height that can be safely inserted without disturbing the surrounding neural elements. Typically, the height is between 8 and 14 mm. 
     In step  902 , the surgeon/practitioner creates disc access. For instance, the patient is placed in the prone position. From the midline laterally, the surgeon/practitioner dissect the skin, subcutaneous tissues, and the paraspinal muscles to locate the spinous process, lamina, dura, facets and nerve roots at the appropriate level(s). The surgeon/practitioner performs a laminotomy and carefully retract the dura to expose the disc space. This exposed disc space  1001  and disc  1002  are shown in  FIG. 10A . 
     In step  903 , the surgeon/practitioner prepares the disc space. Using the appropriate instruments, the surgeon/practitioner remove the disc  1002  material. A box chisel  1101  (shown in  FIG. 11 ) may be used to enlarge the entry and remove posterior osteophytes. The surgeon/practitioner can scrape the cartilaginous layers from the surface of adjacent vertebral endplates until bleeding bone is obtained. Such step is illustrated in  FIG. 10B . The surgeon/practitioner should use caution to avoid damage to the endplates. 
     In step  904 , the surgeon/practitioner makes a height determination. The surgeon/practitioner can select the paddle shaver  1102  that corresponds to the preoperative estimated height and the prepared endplates. Holes with laser marks for depth indication are typically cut into the paddle shaver at preset distances  1003   a  and  1003   b  (such as at 25 mm and 30 mm, respectively). The surgeon/practitioner can insert the paddle shaver  1102  into the disc space and rotate until the desired height is achieved. Such step is illustrated in  FIG. 10C . The surgeon/practitioner again should use caution to avoid damage to the endplates. The surgeon can confirm height and position, such as under fluoroscopy. 
     The surgeon/practitioner should then select the trial that corresponds to the preoperative estimated height and paddle shaver  1102  if applicable. Trials that can be selected include parallel trials  1104  and lordotic trials  1105 . For instance, a 28 mm trial can have grooves for depth indication at 22 mm and 25 mm. The surgeon/practitioner can attach the trial to the multi-tool  1112  or the inserter  1108  and insert the trial into the disc space. The surgeon/practitioner can apply gentle impaction to ensure that the trial fits tightly and accurately between the endplates. Such step is illustrated in  FIG. 10D . The surgeon/practitioner can then confirm height, depth, and position under fluoroscopy. Care must be taken to protect the nerve roots while placing paddle shavers and trials. (This is equally so when inserting the implants, including the expandable fusion device  100 ). 
     In step  905 , the surgeon/practitioner inserts expandable fusion device  100 . The surgeon/practitioner selects the expandable fusion device  100  that corresponds to the trial or paddle shaver size. The surgeon/practitioner can attach the expandable fusion device  100  to the inserter  1108  (having insert arms  801  and  802 ) by aligning the lateral pins with the flat surface of expandable fusion device  100  and turning the handle to expose the internal threaded shaft. The threaded tip of insert  1108  will engage with the central thread of expandable fusion device  100  for secure attachment. The surgeon/practitioner should take care not to over tighten the inserter  1108 . The surgeon/practitioner can pack the grafting area of expandable fusion device  100  with bone graft (such as autologous bone graft) in interior space  107  through graft windows  311 ,  312 , and  313 , as well as the openings at the top and bottom of expandable fusion device  100 . The surgeon/practitioner can insert expandable fusion device  100  into the prepared intervertebral space. Such step is illustrated in  FIG. 10E . Gentle impaction on the inserter  1108  will assist in correct positioning. 
     In step  906 , the surgeon/practitioner expands expandable fusion device  100 . Generally, the inserter  1108  includes a portion that rotating coupler that the surgeon/practitioner can attach to translation body  202 . (Alternative, a tool separate from the inserter  1108  can be used to attach to translation body for rotation). The surgeon/practitioner can then rotate translation body  202  to move guide body  106  along the axis of main body  103  of expandable fusion device  100 . This movement of guide body  106  opens expandable fusion device  100  by moving left lateral expanding body  101  and right lateral expanding body  102  horizontally outward relative to main body  103 . Such step is illustrated in  FIG. 10F . 
     The surgeon/practitioner can then release inserter  1108  from translating body  202 . (If this is a separate tool, the surgeon/practitioner can also optionally remove this separate tool at this point in the procedure). Optionally, the surgeon/practitioner can lock the translation body  202  in place using a locking mechanism (not shown). The surgeon/practitioner can then fully release the inserter  1108 , such as by turning the handle of inserter  1108  counter-clockwise to disengage from expandable fusion device  100 . If additional positioning is required, a tamp may be used with a mallet  1109  to move expandable fusion device  100  to the desired location. 
     In alternative embodiments, the inserter is attached to the translation body  202  and then either in the same tool or a different tool, arms are then used to keep the device in place and stationary during rotation. 
     In step  907 , the surgeon/practitioner verifies the placement of expandable fusion device  100 . Such step is illustrated in  FIG. 10F . The surgeon/practitioner can remove inserter  1108  (and any other instruments) and verify the optimal position (such as by using fluoroscopy). 
     In step  908 , the surgeon/practitioner can supplementary fix expandable fusion device  100 . For instance an FDA cleared pedicle screw system can be used to fix expandable fusion device  100 . 
     In step  909 , and if desired, the surgeon/practitioner can remove or revise expandable fusion device  100 . Expandable fusion device  100  can be removed by breaking the fused bone/device interface with a cutting tool (such as an osteotome or chisel). Once expandable fusion device  100  is loose, surgeon/practitioner attach the inserter  1108  and pull expandable fusion device  100  from the disc space. If additional assistance is required, a slap hammer  1106  can be used to retrieve expandable fusion device  100 . 
     A medical procedure kit fully supports the surgical procedure to implant expandable fusion device  100  can be supplied. Such kit can include one or more expandable fusion devices  100  and some or all of the following tools (shown in  FIG. 11 ): 
     Box chisel  1101 . 
     Paddle shaver  1102 . 
     Paddle starter  1103 . 
     Parallel trial  1104 . 
     Lordotic trial  1105 . 
     Slap hammer  1106 . 
     T-handle  1107 . 
     Inserter  1108 . 
     Mallet  1109 . 
     Impactor  1110 . 
     Handle  1111 . 
     Multi-tool  1112 . 
     The combination of tools and expandable fusion devices  100  can be pre-sterilized for ready use. 
     The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated herein by reference in their entirety, to the extent that they provide exemplary, procedural, or other details supplementary to those set forth herein. It will be understood that certain of the above-described structures, functions, and operations of the above-described embodiments are not necessary to practice the present invention and are included in the description simply for completeness of an exemplary embodiment or embodiments. In addition, it will be understood that specific structures, functions, and operations set forth in the above-described referenced patents and publications can be practiced in conjunction with the present invention, but they are not essential to its practice. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without actually departing from the spirit and scope of the present invention. 
     While embodiments of the invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. The embodiments described and the examples provided herein are exemplary only, and are not intended to be limiting. Many variations and modifications of the invention disclosed herein are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited by the description set out above.