Abstract:
A spinal fusion device that is expandable. The device features a top and bottom surface for engaging adjacent vertebrae, a hollow center for stacking of bone or bone growth material, and a slidable mechanism with grooves for expanding or unexpanding the device.

Description:
FIELD OF THE INVENTION 
     Embodiments of the invention relate to the field of orthopedic surgery, and more particularly, to implants to be placed between vertebrae in the spine. 
     BACKGROUND 
     Spinal stabilization is one approach to alleviating chronic back pain caused by disabled disk material or excessive movement of individual vertebrae. Conventional stabilization techniques include fusing two or more vertebrae together to circumvent or immobilize the area of excessive movement. Normally, the vertebral disk material which separates the vertebrae is removed and bone graft material is inserted in the space for interbody fusion. In addition to, or in place of, the bone graft material, a spinal implant may be inserted in the intervertebral space. 
     The conventional surgical approach for stabilization has been posteriorly for ease of access to the spine and to avoid interfering with internal organs and tissues. Usually the implant site is prepared to maintain natural lordosis and to accept, a certain sized implant within certain pressure limits. This requires considerable time and skill by the surgeon. 
     DESCRIPTION OF THE PRIOR ART 
     U.S. Pat. No. 8,556,979, issued Oct. 15, 2013, describes an expandable fusion device capable of being installed inside an intervertebral disc space to maintain normal disc spacing and restore spinal stability. The fusion device includes a body portion, a first end plate, and a second end plate; both of these end plates can be moved in a direction away from the body portion or towards the body portion into an unexpanded configuration. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention are directed to an expandable spinal fusion device comprising upper and lower sections with depending sidewalls forming a cube-like or rectangular structure with a hollow center. The upper and lower sections comprise a top and a bottom surface, respectively, for engaging adjacent vertebrae, a slidable mechanism for expanding or compacting the device, and a hollow center allowing for packing with bone graft or similar bone growth inducing material. The slidable mechanism comprises slots or grooves on each of the sidewalls depending from the top and bottom surfaces, and a distractor. The distractor comprises a rod, a body and an actuator for enabling distraction. The rod can be telescopic or a jack screw type rod. The distractor comprises a body with protruding members, rollers or pins, for engaging the grooves which are positioned in the exact location directly opposite from each other. When the distractor is actuated, the body slides upwards, downwards or sideways depending on the groove geometry. 
     The device is inserted between the adjacent vertebrae and expanded or increased in height to engage the opposing surfaces of the adjacent vertebra. The adjacent vertebrae are forced apart as the height of the implant increases. The spinal fusion device may be used unilaterally or bilaterally. 
     Accordingly, it is an objective of the instant invention to teach a posterior surgical approach for placement of an adjustable spinal implant for interbody fusion, allowing the implant to be inserted through a small incision and increased in size in situ. 
     It is another objective of the instant invention to teach a spinal implant which allows the surgeon to provide for lordosis intraoperatively and to distract through the implant. 
     It is yet another objective of the instant invention to teach an implant facilitating interbody fusion through bone graft or an ingrowth type implant. 
     Although embodiments are directed to posterior surgical approaches and to provide for lordosis intraoperatively, it is to be understood that the invention may be employed in cervical and thoracic spinal procedures as well as from any direction, that is, anterior, posterior and lateral. 
     Other objectives and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the spinal implant in a contracted position; 
         FIG. 2  is a side view of  FIG. 1 ; 
         FIG. 3  is a perspective view of the spinal implant in an expanded position; 
         FIG. 4  is a side view of  FIG. 3 ; 
         FIG. 5  is a cross sectional overlay of  FIG. 4 ; 
         FIG. 6  is a cross sectional of  FIG. 2 ; 
         FIG. 7  is a cross section of  FIG. 4 ; 
         FIG. 8  is an exploded view of the implant with an alignment tube; 
         FIG. 9  is an exploded view of the implant without an alignment tube. 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application or uses. 
     It should be understood that numerous specific details, relationships, and methods are set forth to provide a full understanding of the invention. One having ordinary skill in the relevant art, however, will readily recognize that the invention can be practiced without one or more of the specific details or with other methods. The present invention is not limited by the illustrated ordering of acts or events, as some acts may occur in different orders and/or concurrently with other acts or events. Furthermore, not all illustrated acts or events are required to implement a methodology in accordance with the present invention. 
     Embodiments of the invention may be practiced without the theoretical aspects presented. Moreover, the theoretical aspects are presented with the understanding that Applicants do not seek to be bound by the theory presented. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description and/or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” 
     Expandable Spinal Fusion Device(s) 
     A spinal fusion is typically employed to eliminate pain caused by the motion of degenerated disk material. Upon successful fusion, a fusion device becomes permanently fixed within the intervertebral disc space. 
     Referring now to the Figures, the spinal fusion device  10  is inserted into the intervertebral space in the insertion mode to replace damaged, missing or excised disk material. In an exemplary embodiment, the device  10  comprises an upper section  11 , a top surface  12 , a lower section  13 , a bottom surface  14 , a body portion  18  and a distractor  55 . The device may be made of conventional materials used for surgical implants, such as stainless steel and its many different alloys, titanium, titanium alloys, metallic alloys, polymeric materials, plastics, plastic composites, ceramic and any other metal or material with the requisite strength and biologically inert properties. 
     In an exemplary embodiment, the upper section  11  of the device  10  comprises a top surface  12  for engaging the end plate of a vertebra and the lower section  13  comprises a bottom surface  14  for engaging the end plate of adjacent vertebra. The top surface  12  and bottom surface  14  are planar to provide large contact areas with each vertebra. In an exemplary embodiment, the top and bottom surfaces  12  and  14  each end at one end with a sloping or angled edge  15 ,  16  running the width of the top  12  and bottom  14  surfaces, respectively. In an exemplary embodiment, the top surface ends with an edge  15  sloped towards the bottom surface, and the bottom surface comprises an edge  16  sloped towards the top surface. In other embodiments, only the top surface has a sloped edge. In another embodiment, only the bottom surface has a sloped edge. In yet other embodiments, the top and bottom surfaces lack a sloped edge. 
     The device  10  is hollow  20 , allowing for insertion of bone graft, bone graft material, scaffolds or any tissue or cellular material. In an exemplary embodiment, bone graft or similar bone growth inducing material can be introduced around and within the fusion device to further promote and facilitate bone fusion. The fusion device is hollow in the center, further providing a space for packing with bone graft or similar bone growth inducing material. Such bone graft or bone growth inducing material can be packed, prior to, subsequent to, or during implantation of the fusion device. 
     The device  10  has two extreme positions and is adjustable infinitely between these positions. The expanded position  100  is the sum of the height of the upper section  11  and the lower section  13 . The compact position  101  is the height of the sides  21  or  22  of the body portion and the sum of the thickness of the top surface  12  and bottom surface  14 . The top surface  12  and the bottom surface  14  contact the body portion  18  when the device is in a compact or unexpanded position with the upper section side walls  23  being able to slidably fit into the hollow area. It is to be understood that the placing of the side walls of the upper and lower sections is interchangeable, in that the sidewalls of the lower section can be placed at a distance further apart than the side walls of the upper section. In this embodiment, the upper section sidewalls slide down the inner side walls of the lower section sidewalls. Conversely, the upper section side walls are placed at a wider distance than the lower section sidewalls so that the upper section sidewalls slide over the lower section side walls during the extension or when the device is in a compacted position. In another embodiment, the upper and lower section sidewalls are placed equidistant from each other so that the sidewalls rest upon each other when the device is in the unexpanded or compact position. The device can be rotated along the longitudinal axis 180 degrees so that the upper section becomes the lower section and vice versa. 
     The upper section  11  comprises a top surface  12  with a large aperture  20  to facilitate bone ingrowth after implantation, and opposing depending sidewalls  23  and  24  projecting from the top surface  12  and positioned parallel to each other. The depending side walls  23 ,  24  terminate in a flat plane and each side wall possesses at least one slot or groove  70  for engaging a protruding member, rollers or pins  52  of the distractor body  55 ; the protruding member dimensioned to slidably fit in the slots or grooves  70 . The angle of the slot or groove relative to a 90° angle to the horizontal plane can vary so that the maximum expanded position can be increased or decreased. For example, if the groove is vertical at a 90° angle to the horizontal plane, the maximum expanded position is greater than if the slot or groove is at a 45° angle to the horizontal plane. However, it is to be understood that a slot or groove having, for example, a 45° angle to the horizontal plane would not only expand the device vertically, but also horizontally. The slot or groove  70  engages the protruding member  52  of the distractor  55  to guide the relative movement of the sections, maintaining the distractor and the depending sidewalls in alignment. 
     The bottom surface  14  of the lower section  13  has a large aperture  20  to facilitate bone ingrowth after implantation. The lower section  13  comprises opposing upstanding sidewalls  40 ,  41  projecting from the bottom surface  14  and positioned parallel to each other. The distance between the opposing sidewalls  40 ,  41  is dimensioned to be less than the distance between the opposing sidewalls  23  and  24  of the upper section  11  so that the upper and lower sections can slidably move between the expanded and compact positions of the device. The depending side walls  40  and  41  terminate in a flat plane, and each side wall possesses at least one slot or groove  71  for engaging a protruding member  52  of the distractor  55 , dimensioned to slidably fit in the slots or grooves  71 . The protruding member can be any type, size or shape, for example, rollers, pins, as long as these protruding members can be engaged by the slots or grooves  71 . The angle of the slots or grooves  71  of the lower depending side walls  40  and  41  and the angle of the slots or grooves  70  of the upper depending side walls  23  and  24  is greater than 0° and up to 180° relative to each other. The slots or grooves  70 ,  71  engage the protruding members, rollers or pins  52  of the distractor  55  to guide the relative movement of the sections, maintaining the distractor and the depending sidewalls in alignment. The slots or grooves  70 ,  71  on each opposing sidewall are diametrically opposed on the opposite side walls. 
     The depending sidewalls of the upper and lower sections and the slot or groove of each sidewall are smooth to provide ease in the relative sliding contact between the sidewalls and between the protruding members  52  of the distractor. In alternative embodiments, the slots or grooves may comprise jagged steps which are positioned to provide a lock-step expansion when the device height is adjusted. 
     In an exemplary embodiment, the device  10  comprises a body portion  18 . In an exemplary embodiment, the body portion  18  has a first end  17 , a second end  19 , a first side portion  26  connecting the first end  17  and the second end  19  and a second side portion  27  connecting the first end  17  and the second end  19 . The first end  17  of the fusion device  10  includes at least one angled surface, a grooved end and a flat end or planar end plate. In preferred embodiments, the first end  17  comprises multiple angled surfaces. In an exemplary embodiment, there are at least two opposing angled surfaces  30 ,  31  forming a generally wedge-shape. In other preferred embodiments, there are at least two opposing angled surfaces  30 ,  31  and a flat end or planar end plate  32  wherein the angled surfaces do not meet but culminate at the flat end  32  at a first end, forming a generally wedge shape; and at the opposing end, the angled surfaces culminate to form a receptacle for receiving the sloped edges of the top and bottom surfaces when the device is in a compacted or unexpanded form. In an exemplary embodiment, the top edge  15  and the bottom edge  16  are angled so as to run parallel with the angled surfaces  30  of the first end  17 . 
     The second end  19  includes an opening  60  which may include threading. The opening  60  is dimensioned to fit a distractor  55 . In an exemplary embodiment, the distractor  55  comprises an actuation member  51 , a rod  54  and a distractor body  55 . The actuation member  51  is located on the outer surface  52  of the second end  19 , and a member  53  of the second end  19  aligns the rod  54  with the distractor body  55 . The rod  54 , which extends into the hollow area of the distractor body  55 , may be threaded or telescopic for slidably moving the distractor body  55  within the hollow center of the device  10 . Although the term “rod” is used, it is merely descriptive and encompasses any shape or form as long as it can move the body of the distractor. In an exemplary embodiment, the distractor body  55  is dimensioned to fit in the hollow center of the device and to provide a large volume for the placing of bone graft, bone graft inducing material, scaffolds or any tissue or cellular material. In an exemplary embodiment, the rod  54  is attached to the distractor body  55 . The distractor body  55  comprises a first end  80 , a second end  81 , a first side portion  82  connecting the first end  80  to the second end  81 , and a second side portion  83  connecting the first end  80  to the second end  81 . The first side portion  82  and the second side portion  83  each comprise at least one, preferably two protruding members, rollers or pins  52  which are dimensioned to slidably fit into the grooves or slots  70 ,  71  in the sidewalls of the upper and lower sections. The first end  80 , in exemplary embodiments is a planar surface. In some embodiments, an alignment tube  84  is attached at the center of the planar surface of the first end  80 . The alignment tube  84  may be hollow and threaded, or may be hollow and smooth, and dimensioned for insertion into support aperture  79 . In preferred embodiments, the rod  54  is a jack screw for engagement of a threaded bore  85  at the second end  81  of the distractor body  55 . A bracket  86  is attached to the second end  19  of the body portion  18 . In an exemplary embodiment, the bracket  86  comprises a bore  87  which has a larger countersunk bore  88  for receiving the rod  54 . The bore  87  and countersunk bore  88  are aligned with the bore  85  of the distractor body  55 . As illustrated in  FIG. 9 , the alignment tube can be removed and still provide stability to the distractor. 
     The distance between the top surface  12  and the bottom surface  14  is adjustable by moving the upper section  11  relative to the lower section  13 . The protruding members  52  of the distractor slide downwards when the distractor is actuated and the distance between the upper and lower section decreases. Conversely, the protruding members  52  of the distractor slide upwards when the distractor is actuated and the distance between the upper  11  and lower section  13  increases. The distractor can be a telescopic mechanism whereby the distractor comprises a member, for example, a telescopic rod, for moving the distractor body  55  by a sliding mechanism and, optionally, a locking mechanism to lock the distractor at a desired position. The distractor is not limited to a sliding mechanism, but can utilize any mechanism as long as the distractor can cause the distractor body  55  to move. 
     The device is inserted into the disk space between adjacent vertebrae with the top surface in contact with the end plate of one vertebra and the bottom surface in contact with the end plate of the adjacent vertebra. When the surgeon actuates the distractor, the rod  54  is extended into the cavity, pushing the distractor body  55  and the protruding members  52  to slide along the slots or grooves  70 ,  71  thereby changing the distance between the top and bottom surfaces  12 ,  14  as the sidewalls move apart, thereby expanding the device  10 . When the actuator is actuated in the opposite direction, the rod member  54  retracts, pulling the distractor body  55  towards the end of the outer wall to which the distractor  55  is fastened. The extending of the rod member  54  can be accomplished by a variety of means, including a pushing or pulling mechanism or a rotating mechanism utilizing a screw and thread means. The telescopic rod, in this embodiment, comprises one or more rods of equal and/or varying lengths, each rod having a circumference slightly smaller than the previous rod so that when the actuator is actuated the rods can extend beyond the length of the first rod or retract into each other. 
     The invention has been described in detail with reference to preferred embodiments thereof. However, it will be appreciated that those skilled in the art, upon consideration of this disclosure, may make modifications and improvements within the spirit and scope of the invention. The following non-limiting examples are illustrative of the invention. 
     All documents mentioned herein are incorporated herein by reference. All publications and patent documents cited in this application are incorporated by reference for all purposes to the same extent as if each individual publication or patent document were so individually denoted. By their citation of various references in this document, Applicants do not admit any particular reference is “prior art” to their invention.