Patent Publication Number: US-11642228-B2

Title: Interbody fusion devices with self-affixing mechanisms

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation application of U.S. Ser. No. 15/841,629 filed on Dec. 14, 2017, which is a continuation application of U.S. Ser. No. 15/141,122, filed Apr. 28, 2016, which is a continuation application of U.S. Ser. No. 14/458,687, filed Aug. 13, 2014, now U.S. Pat. No. 9,351,847, which claims priority to Provisional Application No. 61/868,803 filed Aug. 22, 2013, the entire disclosures of which are incorporated herein by reference in their entireties for all purposes. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure generally relates to fixation devices for positioning and immobilizing adjacent vertebral bodies. In particular, the devices may include interbody fusion devices. 
     BACKGROUND OF THE INVENTION 
     As people age, the intervertebral discs in the spinal column may start to deteriorate. Subsequently, the intervertebral discs being to lose height. As a result of the loss of height between vertebral bodies, the nerves exiting from the spinal canal become compressed and pinched, which causes pain among other neurological deficits. One solution is to insert a spacer in place of the disc to restore the height and to promote fusion between adjacent vertebral bodies to permanently maintain the height restoration. Additional fixation may also be needed to stabilize the spinal segment. A plate is usually provided, and the plate may be positioned on the anterior portions of the adjacent vertebral bodies. In some cases, the profile of the plate becomes obstructive to the anatomy. The approach to the spine is also significant in that a direct anterior approach requires navigation or dissection of vascular anatomy. 
     As a result, there is a need to provide a spacer having fixation elements to attach the spacer directly to adjacent vertebrae, to limit any profile protruding out of the spine column anteriorly, and to avoid proximal anatomy from a direct anterior approach. 
     SUMMARY OF THE INVENTION 
     This application relates to interbody fusion devices with self-affixing mechanisms. Each of the interbody fusion devices can be used following a discectomy to assist in maintaining height between vertebral bodies. While the devices are particularly useful in the anterior spinal column, the devices can be used in different regions of the spine as well. 
     According to one embodiment, an implant for implantation in a treated area of an intervertebral space between vertebral bodies of a spine includes a spacer, an end member, and at least one fixation member. The spacer has a superior surface and an inferior surface. The spacer may define an opening extending from the superior surface to the inferior surface configured to receive bone graft material. The superior surface and the inferior surface each have a contact area configured to engage adjacent vertebrae. The end member is coupled to the spacer. The end member has at least one hole traversing the end member at an angle. The fixation member is configured to extend through the at least one hole traversing the end member. The fixation member may include a curved shim configured to be hammered into adjacent vertebrae. Shims alone may be used to secure the implant or other fixation members may be used in combination with the shim. 
     The shim may include a spline extending along at least a portion of a longitudinal axis of the shim. The spline may have the greatest height at a head portion of the shim, which tapers to a smallest height proximate to a distal most end of the shim. The shim may have a flat head portion. Alternatively, the shim may have a rounded head portion including an opening configured to retain an insertion instrument. In another embodiment, the shim may be smooth with a substantially conical shape. 
     The fixation member may be retained within the end member with a blocking mechanism. The blocking mechanism may include a screw having a head which covers over and/or rests against a portion of the fixation member, thereby preventing unintentional backout. Alternatively, the blocking mechanism may include a spring tab configured to block the fixation member once the fixation member is fully inserted into the end member. 
     The fixation member may be in a deployable form having a tip configured to expand after implantation. The deployable fixation member may include an inner portion and an outer sleeve. Once the deployable fixation member is inserted into bone, the inner portion is capable of being pulled opposite to the insertion direction to deform and splay the tip of the fixation member open. 
     According to another embodiment, an implant may include a spacer having a superior surface and an inferior surface. The superior surface and the inferior surface each have a contact area configured to engage adjacent vertebrae. The spacer defines at least one opening extending from the superior surface to the inferior surface. At least one shaft may be coupled to the spacer and extends through the opening in the spacer. One or more fins may be operatively attached to the shaft such that rotation of the shaft causes deployment of the one or more fins configured to engage adjacent vertebral bone when deployed. 
     The fins may be rotated about 90° between retracted and deployed positions. In one embodiment, the fins may rest on a wall dividing the opening when in the retracted position. In an alternative embodiment, the fins may be sized and shaped such that they are housed within the opening when in the retracted position. The fins may include a plurality of fins attached to a single shaft. Alternatively, more than one shaft may be used with one or more fins positioned on each shaft. The fins may have a sharpened edge configured to cut through the adjacent vertebral bone. The fins may have straight or hooked shapes, for example. 
     According to another embodiment, an implant may include a spacer having a superior surface and an inferior surface. The spacer may include a ramped surface positioned on a portion of the superior and/or inferior surface. An end member configured to be coupled to the spacer may house or contain one or more blades. As the end member is attached to the spacer, the one or more blades may engage the ramped surface of the spacer, thereby causing the one or more blades to expand outwardly and engage adjacent vertebrae. 
     The blades may include two blades attached together via a hinge (e.g., a living hinge). The blades may have a first, collapsed orientation before the end member is attached to the spacer, and a second, expanded orientation where the blades are expanded apart such that an angle between the blades is larger than in the collapsed orientation. The ramped surface may be angled such that the ramped surface extends from a central portion of the spacer and increases in height outward toward the lateral portion of the spacer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be best understood from the following detailed description when read in connection with the accompanying drawing. It is emphasized that, according to common practice, the various features of the drawing are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawing are the following figures: 
         FIG.  1    shows an example of an interbody fusion device implantable in a disc space in accordance with an embodiment of the present application; 
         FIG.  2    depicts an alternative embodiment of an interbody fusion device with self-affixing mechanisms; 
         FIG.  3    shows an alternative embodiment of an interbody fusion device with self-affixing mechanisms; 
         FIG.  4    depicts an alternative embodiment of an interbody fusion device with self-affixing mechanisms; 
         FIG.  5    shows an alternative embodiment of an interbody fusion device with self-affixing mechanisms; 
         FIG.  6    illustrates a top perspective view of an alternative interbody fusion device including a spacer body with deployable fins on multiple shafts; 
         FIG.  7    shows a top perspective view of an alternative interbody fusion device including a spacer body with deployable fins on a single shaft; 
         FIGS.  8 A and  8 B  illustrate top perspective views of an alternative embodiment of an interbody fusion device having hinged blades; 
         FIGS.  9 A and  9 B  illustrate an alternative interbody fusion device having deployable straight or curved nails; 
         FIGS.  10 A and  10 B  illustrate a spring tab feature on the embodiment depicted in  FIGS.  9 A and  9 B ; 
         FIGS.  11 A-D  provide an alternative interbody fusion device having deployable two-piece nails; 
         FIG.  12 A-F  show an alternative interbody fusion device having one or more sets of fins that cut through adjacent bone; 
         FIGS.  13 A and  13 B  show an alternative interbody fusion device having deployable spikes through a rack and pinion design; 
         FIG.  14    illustrates an alternative interbody fusion device having deployable spikes using movable ramps; 
         FIGS.  15 A and  15 B  show an alternative interbody fusion device having a deformable spike or nail; 
         FIGS.  16 A-C  show an alternative embodiment of an interbody fusion device having deployable spikes or nails; 
         FIGS.  17 A and  17 B  depict an alternative interbody spinal fusion device that includes an internal pivoting hook member; 
         FIGS.  18 A-E  show an alternative interbody spinal fusion device that includes deployable tangs; 
         FIG.  19    illustrates an interbody fusion device having a mechanism for facilitating inline operation; 
         FIGS.  20 A and  20 B  illustrates a universal joint (e.g., a ball joint) that can be built in the head of a bone screw to provide polyaxial adjustability; 
         FIG.  21    illustrates how deployable nails, fins etc. can be actuated by a worm and/or worm wheel with teeth; 
         FIG.  22    illustrates an embodiment of an interbody fusion device having deployable barb wires through a curved spike hammered in through the spacer body; 
         FIG.  23    illustrates an alternative interbody fusion device including a straight or curved rack and pinion mechanism; and 
         FIG.  24    illustrates a keeled connection between a spacer and a vertebral body. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the disclosure are generally directed to stand-alone interbody fusion implants. Specifically, the implants include a spacer body. The spacer may be combined with an end member. One or more fixation members, such as screws, nails, shims, tangs, spikes, staples, pins, fins, blades, or the like, may be used to secure the device to adjacent vertebrae. The fixation members may also include a combination of these to provide for optimal ease of insertion and fixation of the device. 
     The embodiments of the disclosure and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments and examples that are described and/or illustrated in the accompanying drawings and detailed in the following description. The features of one embodiment may be employed with other embodiments as the skilled artisan would recognize, even if not explicitly stated herein. Descriptions of well-known components and processing techniques may be omitted so as to not unnecessarily obscure the embodiments of the disclosure. The examples used herein are intended merely to facilitate an understanding of ways in which the disclosure may be practiced and to further enable those of skill in the art to practice the embodiments of the disclosure. Accordingly, the examples and embodiments herein should not be construed as limiting the scope of the disclosure, which is defined solely by the appended claims and applicable law. Moreover, it is noted that like reference numerals represent similar parts throughout the several views of the drawings. 
     As used herein and in the claims, the terms “comprising” and “including” are inclusive or open-ended and do not exclude additional unrecited elements, compositional components, or method steps. Accordingly, the terms “comprising” and “including” encompass the more restrictive terms “consisting essentially of” and “consisting of.” 
     Certain embodiments may be used on the cervical, thoracic, lumbar, and/or sacral segments of the spine. The size and mass increase of the vertebrae in the spine from the cervical to the lumbar portions is directly related to an increased capacity for supporting larger loads, for example. This increase in load bearing capacity, however, is paralleled by a decrease in flexibility and an increase in susceptibility to strain. When rigid immobilization systems are used in the lumbar segment, the flexibility is decreased even further beyond the natural motion restriction of that segment. Replacing the conventional rigid immobilization systems with certain embodiments disclosed herein may generally restore a more natural movement and provide added support to the strain-susceptible areas. 
     Referring now to the figures,  FIGS.  1 - 5    depict alternative embodiments of an interbody fusion device  10  having different types of fixation members  28  designed to secure the fusion device  10  to adjacent vertebral bodies. The fixation members  28  may be in the form of one or more screws  30 , nails or shims  32 , or the like. 
     With reference to  FIG.  1   , an example of an interbody fusion device  10  in accordance with one embodiment of the present application is shown, which is implantable in a disc space. The device may comprise a spacer or body portion  12  affixed to an end member  50 . The body portion  12  may be in the form of a spacer or cage having an opening  16  that may serve as a graft opening for receiving graft material. The body portion  12  can include a contact area having one or more protrusions  14 , for example, in the form of teeth, ridges, or ribs on either or both of its superior and inferior surfaces  42 ,  44  to prevent expulsion of the body portion  12  between adjacent vertebrae. The body portion  12  can be formed of PEEK (polyether ether ketone), other plastics, titanium, other metal or metal alloys, or other suitable bio-compatible materials known in the art. 
     The spacer or body portion  12  and the end member  50  may be coupled, removably coupled, connected, or attached together in any suitable manner known in the art. The body portion  12  and the end member  50  may be coupled together through appropriate coupling means or fasteners. For example, at least a portion of the end member  50  and/or body portion  12  may be configured to provide male and female projections and recesses, which act as the mechanical interfaces between the two pieces. The body portion  12  and the end member  50  may be assembled together using, alone or in combination, a friction fit, a dovetail assembly, dowel pins, hooks, staples, screws, adhesives, and the like, or any suitable fasteners known in the art. The end member  50 , which can be formed of metal, for example, can include one or more openings for receiving one or more fixation members  28  therethrough. The openings may be angled such that the openings extend through the end member  50  at an angle divergent to a horizontal plane. The end member  50  may be contoured any may include one or more eyebrows, for example, to accommodate the angled trajectory of the fixation members  28 . 
     The fixation members  28  are configured to extend into a vertebral body to provide vertebral fixation. The fixation members  28  may include one or more components designed to secure the device to adjacent vertebrae. By way of example, the fixation members  28  may be selected from screws, nails, shims, staples, pins, or the like, and combinations thereof. As shown in  FIG.  1   , the fixation members  28  can include one or more bone screws  30  (facing downward in  FIG.  1   ), as well as one or more thinner nails or shims  32  (facing upward in  FIG.  1   ). 
     The bone screws  30  may include a threaded shaft and a head portion  31 . The head portion  31  may be rounded. The screws  30  may include any suitable screws known in the art including fixed or variable angle of any suitable size with appropriate thread spacing, thread pitch, head design, length, and the like. The screws  30  enter the screw holes in the end member  50  at specified angles to enter each of the adjacent vertebrae at the optimal locations. In particular, the screws  30  may be inserted at an angle for maximum screw purchase into the superior and/or inferior vertebral bodies. 
     The shims  32  may include a substantially flat or thin piece of material extending along a longitudinal axis. In some embodiments, the one or more shims  32  can be curved or angled, while in other embodiments, the one or more shims  32  can be straight. While bone screws  30  provide strength, in some situations, it may desirable to use a thinner nail or shim  32 , as such fixation members  28  can be easily inserted. In some embodiments, the bone screw  30  is screwed into bone (e.g., using a driver), while the shim  32  can be hammered into place. The shim  32  may include a head portion  33  which is substantially flattened at its proximal most end. The flattened head portion  33  may allow for greater contact area with an insertion instrument, for example, when the shim  32  is hammered into place. The shims  32  may include a rounded or pointed tip at the distal most end. The shims  32  may or may not contain an extension or spline  34 . If present, the spline  34  may be positioned at any suitable location along the shim  32 . For example, the spline  34  may extend along at least a portion of the longitudinal axis of the shim  32 . The spline  34  may also extend to the head portion  33 . The spline  34  may have the greatest height at the head portion  33  and taper to the smallest height proximate to the distal most end of the shim  32 . A cross piece may be positioned below the spline  34  and across the head portion  33 , for example, to further secure the shim  32  to the end member  50  and/or stabilize the device  10 . 
     While  FIG.  1    shows two bone screws  30  and one shim  32 , in other embodiments, the device can include different numbers, types, and variations of bone screws  30  and/or shims  32 . For example, in some embodiments, the device can be fixed to adjacent vertebrae using only shims  32  (e.g., via three or more shims  32 ). The fixation members  28  can not only provide a means of fixation between the device  10  and vertebrae, but in some embodiments, can also help lag vertebral bone down to the spacer body  12 . 
     In some embodiments, the fixation members  28  can be pre-assembled with the body portion  12  as the body portion  12  is inserted into the disc space. The fixation members  28  would simply need to be deployed into the vertebral bodies once the cage body is in a desired surgical site. In other embodiments, the fixation members  28  can be inserted into the body portion  12  after the body portion  12  is inserted into a disc space. 
     In addition to having one or more openings for receiving one or more fixation members  28 , the end member  50  can include one or more openings to retain one or more blocking mechanisms  20  to prevent undesirable backout of the fixation members  28  (e.g., screws  30  or shims  32 ). As shown in  FIG.  1   , the device  10  can include two or more blocking mechanisms  20  (e.g., blocking screws) that prevent backout. In some embodiments, the blocking mechanism  20  can prevent backout of one or more fixation members  28  (e.g., a bone screw  30  or a nail/shim  32 ). In other embodiments, the blocking mechanism  20  can prevent backout of two or more fixation members  28  (e.g., a bone screw  30  and a nail/shim  32 ). For example, as shown in  FIG.  1   , each blocking mechanism  20  serves to block both the bone screw  30  and the shim  32  from unintended backout. In some embodiments, the blocking mechanism  20  includes a cut-out portion that allows for insertion of the fixation member  28  through the end member  50 . Once the fixation member  28  is inserted through the end member  50 , the blocking mechanism  20  can be rotated, such that at least a portion of the blocking mechanism  20  covers over and/or rests against a portion of the fixation member  28 , thereby preventing unintentional backout. 
     Referring now to  FIG.  2   , an alternative embodiment of an interbody fusion device  10  is shown with self-affixing mechanisms. This device  10  includes similar features as the device described in  FIG.  1   , including body portion  12 , end member  50 , one or more fixation members  28 , and one or more blocking mechanisms  20 . However, the present device  10  utilizes three fixation members  28 —each comprising a bone screw  30  for maximum fixation. As shown in  FIG.  2   , two of the bone screws  30  face downwardly, while one of the bone screws  30  faces upwardly. 
     As shown in  FIG.  3   , an alternative embodiment of an interbody fusion device  10  with self-affixing mechanisms is shown. This device  10  includes similar features as the device described in  FIG.  1   , including the body portion  12 , the end member  50 , one or more fixation members  28 , and one or more blocking mechanisms  20 . As shown in  FIG.  3   , the fixation members  28  can include one or more bone screws  30  (facing downward in  FIG.  3   ), as well as one or more thinner nails or shims  32  (facing upward in  FIG.  3   ). However, the present device  10  utilizes a distinct upwardly facing nail or shim  32  that is slender and tapered. This shim  32 , which is curved in  FIG.  3   , advantageously accommodates easy insertion into a vertebral body. 
     Note that in the present embodiment, the shim  32  has a rounded head portion  33 , similar to the head portions  31  of the bone screws  30 . The rounded head  33  may include an opening, for example, configured to retain an insertion instrument. This is in contrast to the shim  32  in  FIG.  1   , which does not have a rounded head portion  33 , but rather is substantially flattened at its proximal most end. The rounded head  33  of the shim  32  advantageously provides a mechanism for preventing over-insertion of the shim  32  into the device  10 . Likewise, however, the substantially flattened shim  32  in  FIG.  1    can also provide its own mechanism, such as a tab or particularly shaped feature that prevents over-insertion of the shim  32  in the fusion device  10 . Similar to  FIG.  1   , the shims  32  may include a spline  34 . The spline  34  may extend along at least a portion of the longitudinal axis of the shim  32 . In this case, the spline  34  extends along the entire length of the shim  32 . The shim  32  is also provided with a pointed tip at the distal most end. 
       FIG.  4    shows an alternative embodiment of an interbody fusion device  10  with self-affixing mechanisms in accordance with one embodiment. This device  10  includes similar features as the device described in  FIG.  1   , including body portion  12 , end member  50 , one or more fixation members  28 , and one or more blocking mechanisms  20 . However, in the present device  10 , the three fixation devices  28  are each slender, tapered nails or shims  32 . Each of the shims  32  is curved and designed to provide easy access into a vertebral body. 
       FIG.  5    shows an alternative embodiment of an interbody fusion device  10  with self-affixing mechanisms in accordance with one embodiment. This device  10  includes similar features as the device described in  FIG.  1   , including body portion  12 , end member  50 , one or more fixation members  28 , and one or more blocking mechanisms  20 . However, in the present device  10 , the fixation members  28  comprise three smoothened shims or nails  32  that can be inserted into a vertebral body. These nails  32  may be substantially conical in shape and do not include splines. The nails  32  may or may not include a head portion, and as shown, the nails  32  may be substantially flattened at its proximal most end. The nails  32  may include a rounded or pointed tip at the distal most end. In some embodiments, the nails  32  can be straight or, as shown in  FIG.  5   , may be curved, with a minimum of one in the superior direction and one in the inferior direction. The shims or nails  32  can be pressed through the spacer body  12  and retained partially within the spacer body  12 . The nails  32  can be held within the spacer body  32  by a component such as a blocking screw  20 . In some embodiments, the shims or nails  32  can be held in position via a spring tab (see  FIGS.  10 A  and B). 
       FIG.  6    illustrates a top perspective view of an alternative interbody fusion device  100  including a spacer body  112  in accordance with some embodiments of the present application. The spacer body  112  may be in the form of a spacer or cage having one or more openings  116  that may serve as a graft opening for receiving graft material. As shown, the opening  116  may be divided into two equal parts separated by a central wall. The spacer body  112  can include a contact area having one or more protrusions  114 , for example, in the form of teeth, ridges, or ribs on either or both of its superior and inferior surfaces  142 ,  144  to prevent expulsion of the spacer body  112  between adjacent vertebrae. In the present embodiment, the spacer body  112  is configured to have one or more ridges on a least a portion of its superior and inferior surfaces  142 ,  144 . In addition, it is configured to have one or more fins  152  that cut through bone in adjacent vertebrae. The one or more fins  152  can be operatively attached to one or more shafts  154 . The shaft  154  may be in the form of a cylinder extending through the opening  116  from a proximal portion to a distal portion of the spacer  112 . Rotation of the shaft  154  causes the deployment of the fins  152 , which can lodge and engage in adjacent vertebral bone. The fins  152  may have straight or hooked shapes, for example. The fin  152  may have a sharpened edge to facilitate insertion into the adjacent vertebrae. 
     As shown in  FIG.  6   , the device  100  can include two or more shafts  154 , each with one or more fins  152  attached thereto. The device  100  may be configured such that at least one fin  152  engages a superior vertebra and at least one fin  152  engages an inferior vertebra. As shown, the two shafts  154  may be offset from one another. The spacer body  112  can include one or more actuation openings  156  that provide access to the shafts  154 , thereby allowing one or more instruments to rotate and actuate the shafts  154 . As shown in  FIG.  6   , rotation of the shaft  154  in a first direction will cause deployment of the fin  152 , for example in a substantially vertical orientation  152  (not shown), whereas rotation of the shaft  154  in a second opposite direction will cause retraction of the fin  152 , for example, in a substantially horizontal orientation (in the position shown). In particular, the fin  152  may be rotated about 90° between the retracted and deployed positions. The fins  152  may rest on the wall dividing the opening  116  when in the retracted position. The fins  152  may be sized and shaped such that they are unable to enter the opening  116  when actuated. 
     Each of the shafts  154  can be operated independently from one another. The interbody fusion device  100  in  FIG.  6    can advantageously operate on its own, without the addition of a plate or other fixation members. However, in other embodiments, the device  100  in  FIG.  6    can also be fixed to an end member (as described in other embodiments herein), plate, or the like and can include one or more additional fixation members (e.g., bone screws, nails, shims) to provide additional fixation to adjacent vertebral bodies. 
       FIG.  7    illustrates a top perspective view of an alternative interbody fusion device  200 , which is similar to the device  100  shown in  FIG.  6   . The device  200  includes a spacer body  212 . The spacer body  212  may be in the form of a spacer or cage having opening  216  that may serve as a graft opening for receiving graft material. In this embodiment, a single opening  216  is provided in the spacer body  212 . Like the fusion device  100  in  FIG.  6   , the present fusion device  200  includes a plurality of ridges on a least a portion of its superior and inferior surfaces  242 ,  244 , as well as at least one shaft  254  and at least one fin  252 . However, in the present embodiment, the fusion device  200  includes only one central shaft  254  with multiple fins  252  extending therefrom (e.g., three upper and three lower fins  252 ) attached to the shaft  254 . The fins  252  may be all of the same height and configuration or may be different. The fins  252  may be coaxially aligned with one another on the shaft  254 . The shaft  254  may extend centrally through the opening  216  from a proximal portion to a distal portion of the spacer  212 . The shaft  254  may be provided with one or more openings to allow for egress and/or ingress of graft material. Rotation of the central shaft  254  causes deployment of the multiple fins  252  such that three upper fins  252  can engage an upper vertebra, while three lower fins  252  (not shown) can engage a lower vertebra. To rotate the shaft  254 , a driver opening  256  can be provided to accommodate an actuation or driving instrument. 
     Rotation of the shaft  254  in a first direction will cause deployment of the fins  252 , for example, in a substantially vertical orientation (shown in  FIG.  7   ), whereas rotation of the shaft  254  in a second opposite direction will cause retraction of the fins  252 , for example, in a substantially horizontal orientation (not shown). In particular, the fins  252  may be rotated about 90° between the retracted and deployed positions. The fins  252  may be sized and shaped such that they are housed within the opening  216  when in the retracted position. 
       FIGS.  8 A and  8 B  illustrate top perspective views of an alternative embodiment of an interbody fusion device  300  having hinged blades  352 .  FIG.  8 A  shows the device  300  disassembled, while  FIG.  8 B  shows the device  300  assembled and configured to be engaged into adjacent vertebrae. The interbody fusion device  300  includes a spacer body  312  and an end member  350  configured to be affixed to the spacer body  312 . The spacer body  312  may be in the form of a spacer or cage having an opening  316  that may serve as a graft opening for receiving graft material. The spacer body  312  can include one or more protrusions  314 , for example, in the form of teeth, ridges, or ribs on either or both of its superior and inferior surfaces  342 ,  344  to prevent expulsion of the spacer body  312  between adjacent vertebrae. As shown, the spacer body  312  is configured to have a plurality of teeth on a least a portion of its superior and inferior surfaces  342 ,  344 . 
     The spacer body  312  includes at least one ramped surface  318 . The ramped surface  318  may be positioned on a portion of the superior and/or inferior surfaces  342 ,  344  on a proximal portion of the spacer body  312  proximate to the end member  350 . The ramped surface  318  may include an angled or tapered surface configured to engage a blade  352 . The angle of the ramped surface  318  may range from about 1-70°, about 5-60°, about 10-40°, or about 15-30° relative to a horizontal axis. As shown in  FIG.  8 A , the spacer body  312  may include two ramped surfaces  318  on the superior surface  342  and two identical ramped surfaces  318  on the inferior surface  344  (not shown). The ramped surfaces  318  may be angled such that they extend from a central portion of the spacer body  312  and increase in height outward toward the lateral portions of the spacer body  312 . 
     The spacer body  312  can be removably coupled, attached, or affixed to the end member  350 . The spacer body  312  can be attached to the end member  350  by a coupling mechanism, friction fit, interference fit, or any other connection means. For example, the spacer body  312  and the end member  350  may be assembled together using, alone or in combination, a dovetail assembly, dowel pins, hooks, staples, screws, adhesives, and the like, or any suitable fasteners known in the art. The end member  350  may include upper and lower surfaces having one or more torsional stabilizers  370  extending therefrom configured to prevent or minimize torsional motion of the implant  300  once implanted. The torsional stabilizers  370  may act as extensions or fins, which may serve as knife edges to further purchase into the bone of the adjacent vertebrae and/or serve as a stop to abut anterior aspects of the adjacent vertebrae. The torsional stabilizer  370  may include a spiked or pointed projection or extension configured to engage adjacent vertebrae. The torsional stabilizers  370  may be provided at any suitable locations. For example, as shown in  FIG.  8 B , the torsional stabilizers  370  may be provided proximate to the lateral sides of the end member  350  and are also provided substantially medially on the end member  350  projecting superiorly and inferiorly from both the upper and lower surfaces, respectively. 
     The end member  350  houses one or more blades  352 . The blade  352  may have an elongated, relatively thin structure. The blade  352  may be substantially straight and flat or may be curved. The blade  352  may have any suitable length and width. For example, the blade  352  may have a length substantially the same as the spacer body  312  and a width that is substantially the same as the opening  316  in the spacer body  312 . The blade  352  may have a sharpened distal edge to facilitate insertion into the adjacent vertebrae. The distal edge may also be beveled or chamfered at the corners. 
     The one or more blades  352  may be attached together via a hinge  358 . For example, the hinge  358  may be in the form of a cantilevered v-spring with a cross-sectional configuration in the form of a V connecting two blades  352 . The hinge  358  may include a living hinge, barrel hinge, piano hinge, ball and socket type hinge, spring, or other suitable hinge known in the art. In one embodiment, the hinge  358  may include a living hinge connecting the blades  352 . Living hinges may include one-piece flexing devices or functional hinges having a flexing zone between the blades  352 . The living hinge may be constructed of pliant and/or flexible materials having properties which tolerate the repeated tension and compression of the opposing surfaces (i.e., the blades  352 ). The end member  350  may include one or more openings or windows providing visualization of the blades  352  and/or hinge  358 . 
     As the spacer body  312  is attached or affixed to the end member  350 , the one or more hinged blades  352  engage the ramped surfaces  318  of the spacer  312 , thereby causing the blades  352  to spread apart and expand outwardly. The blades  352  may have a first, collapsed orientation where the angle between the blades  352  is small and a second, expanded orientation where the angle between the blades  352  is increased to be larger than in the collapsed orientation. The blades  352  are configured to engage one or more adjacent vertebral bone members when in the expanded orientation. 
     In some embodiments, the body portion  312  is configured to be inserted into a disc space prior to inserting and attaching the end member  350 . After clearing a disc space and performing a total or partial discectomy, the body portion  312  can be inserted first into a desirable location. Afterwards, the end member  350  with the one or more blades  352  connected thereto can be attached to the body portion  312 . During engagement between the body portion  312  and the end member  350 , the blades  352  extend outwardly and into adjacent bone members. In other embodiments, the body portion  312  can be pre-assembled with the end member  350  prior to inserting the interbody fusion device  300  in a disc space. 
       FIGS.  9 A  and B and  FIGS.  10 A  and B illustrate an alternative interbody fusion device  400  having deployable straight or curved fixation members  428 , such as nails. The interbody fusion device  400  may include any of the fusion devices described herein.  FIG.  9 A  depicts a top view of a spacer body  412  and an insertion instrument  480  configured for inserting two fixation members  428  through the spacer body  412 . The insertion instrument  480  may include a pusher element  482 , which may be threaded, for example. As the pusher element  482  is advanced and/or rotated in the direction of the arrows, the fixation members  428  are advanced into the spacer body  412  and deployed into the adjacent vertebrae. The pusher element  482  may be ratchet or lever operated, for example. The instrument  480  may be able to deploy multiple fixation elements  428  simultaneously. 
       FIG.  9 B  depicts a side view of the embodiment shown in  FIG.  9 A  where the fixation members  428  (initially depicted as dashed lines) enter the spacer body  412  to be deployed within the superior and inferior vertebral bodies. For example, the devices  400  may have a minimum of one in the superior direction and one in the inferior direction which are pressed through the spacer body  412  and retained partially within the spacer body  412 . The fixation members  428  may be straight or curved and may include any of the fixation members described herein. 
     The fixation member  428  may be held within the spacer body  412  with an additional component, such as a blocking mechanism. The blocking mechanism may include any of the blocking mechanisms described herein, such as a blocking screw. Alternatively, the fixation member  428  could be held in position with a spring tab  422 .  FIG.  10 A  illustrates a top view of the spacer body  412  having the spring tab  422  in an initial position before the fixation member  428  is fully inserted, and  FIG.  10 B  illustrates a top view of the same spacer body  412  in a final position with the fixation member  428  fully inserted and the spring tab  422  engaged to retain the fixation member  428 . The spring tab  422  may include a flexible portion that flexes as the fixation member  428  is inserted into the device  400 , and blocks the fixation member  428  once it is fully inserted. As shown in  FIG.  10 B , after insertion, the fixation member  428  is blocked by the spring tab  422  and is unable to back out of position. In addition, the fixation members  428  (e.g., nails) may be prevented from being pushed too far into the vertebral body by a head  433 , for example, on each nail, or by limits fixed to the deploying inserter instrument  480 . 
       FIGS.  11 A-D  illustrate an alternative interbody fusion device  500  having deployable two-piece fixation members  528 , such as nails, that could be curved or straight. The interbody fusion device  500  may include any of the fusion devices described herein.  FIG.  11 A  depicts a side view of a spacer body  512  including two-piece fixation member  528  extending therethrough and into an adjacent vertebra in an initial, insertion configuration.  FIG.  11 B  depicts a side view of the spacer body  512  with the fixation member  528  in a final, deployed configuration. 
     In some embodiments, the two-piece fixation member  528  can comprise an inner portion  560  and an outer sleeve  562 . The assembled inner and outer parts  560 ,  562  can be pushed into a vertebral bone together, for example, as shown in  FIG.  11 A . Once the assembly is inserted into a desired location into bone, the inner portion  560  is capable of being pulled back slightly toward the outer sleeve  562  and away from the insertion direction, as the arrow depicts in  FIG.  11 B . This action deforms and splays the tip  564  of the fixation member  528 , thereby advantageously helping to secure the fixation member  528  and/or the inner portion  560  in the bone. The deployed configuration may help to prevent back out of the fixation member  528 . In addition, this method may compressively load the graft within the graft window  516  in the spacer body  512 . Similarly,  FIG.  11 C  shows an alternative tip  564  for the fixation member  528  in the initial, insertion configuration, and  FIG.  11 D  shows the tip  564  in the final, deployed configuration. As above, the assembled inner portion  560  and outer sleeve  562  can be inserted into a vertebral bone together, and once the assembly is pushed into a desired location in the bone, the inner portion  560  is pulled opposite to the insertion direction to expand or inflate the tip  564  of the fixation member  528 . 
     Similar to the embodiments depicted in  FIGS.  6  and  7   ,  FIGS.  12 A-F  show alternative interbody fusion devices  600  having one or more sets of fins  652  that cut through adjacent bone.  FIG.  12 A  shows the device  600  having a spacer body  612 . The spacer body  612  may be in the form of a spacer or cage having opening  616  that may serve as a graft opening for receiving graft material. As shown, the fusion device  600  may have at least one central shaft  654  with one or more sets of fins  652 . The fins  652  may be initially contained within the opening  616  as shown in  FIG.  12 A . The fins  652  may be activated by a driver, for example, and the fins  652  may retain and secure the device  600  once deployed, as shown in  FIG.  12 B . The one or more sets of fins  652  can be straight or have hooked shapes.  FIGS.  12 C  and D depict a similar set of fins  652  in a deployed state where the fins  652  are larger than the graft opening  616 .  FIGS.  12 E  and F depict a similar set of fins  652  in a deployed state where the fins  652  have a bent or hooked configuration (e.g., L-shaped, J-shaped, C-shaped, or the like). The fins  652  may be all of the same type, height, and configuration or may be different on a given device  600 . 
     Rotation of the central shaft  654  causes deployment of the fins  652  such that the fins  652  can engage an upper and/or lower vertebrae. Rotation of the shaft  654  in a first direction will cause deployment of the fins  652 , for example in a substantially vertical orientation, whereas rotation of the shaft  654  in a second opposite direction will cause retraction of the fins  652 , for example, in a substantially horizontal orientation. In particular, the fins  652  may be rotated about 90° between the retracted and deployed positions. 
       FIGS.  13 A  and B show an alternative interbody fusion device  700  having deployable fixation members  728  through a rack and pinion design. Similar to the other devices described herein,  FIG.  13 A  depicts a top view of a spacer body  712  with a graft opening  716 .  FIG.  13 B  depicts a side view of the device  700 . One or more fixation members  728  may be connected or coupled to the spacer body  712  with a rack and pinion  724 . The rack and pinion  724  may include circular gear or pinion, which engages teeth on a linear gear or rack. The rack and pinion  724  may convert rotational motion, for example, from a driver, into linear motion of the fixation members  728 . The fixation members  728  may include screws, nails, shims, spikes, staples, pins, or the like. In an exemplary embodiment, the fixation members  728  are in the form of deployable spikes or nails. Alternatively, the interbody fusion device  700  can have deployable screws via a worm gear mechanism (see  FIG.  21   ). 
       FIG.  14    illustrates an alternative interbody fusion device  800  using one or more movable ramps  826 . The ramp  826  may have a translation member  836  having one or more ramped surfaces  838  that engage deployable fixation members  828 , such as a spikes. As shown in  FIG.  14   , the translation member  836  of the device  800  can include at least two upper ramps  838  connected via a bridge, and two lower ramps  838  connected via a bridge. Each of the ramped surfaces  838  is configured to engage a deployable fixation member  828 . As the translation member  836  is translated (e.g., via a rotatable actuation member) in a first direction, the ramped surfaces  838  engage the fixation members  828 , thereby deploying them through openings in the upper and lower surfaces of the fusion device  800 . Thus, the ramped surfaces  838 , when translated linearly, cause the fixation members  828  to expand outwardly and engage the adjacent vertebrae. Although two ramped surfaces  838  are depicted to engage two fixation members  828  on each of the upper and lower surfaces, any suitable number of ramped surfaces  838  and fixation members  828  may be used. 
       FIGS.  15 A  and B show an alternative interbody fusion device  900  having deformable fixation members  928 , such as a nails or a spikes. The interbody fusion device  900  may include any of the fusion devices described herein.  FIG.  15 A  depicts a side view of a spacer body  912  including a first member  962  extending therethrough and into an adjacent vertebrae in an initial, insertion configuration.  FIG.  15 B  depicts a side view of the spacer body  912  with the fixation member  928  in a final, deployed configuration. The deformable fixation member  928  may be comprised of a two-piece design whereby a first member or outer sleeve  962  is first introduced into the vertebral body. A second member or inner portion  960  is then threaded or otherwise pushed through the first member  962 . The tip of the first member  962  is configured to splay and deform as shown in  FIG.  15 B . The deployed configuration may help to prevent back out of the fixation member  928 . The fixation members  928  may be curved or straight before and/or after being deployed. 
       FIGS.  16 A-C  show an alternative embodiment of an interbody fusion device  1000  having deployable fixation members  1028 , such as spikes or nails. The interbody fusion device  1000  may include any of the fusion devices described herein.  FIG.  16 A  depicts a side view of a spacer body  1012  including fixation members  1028  extending therethrough and into adjacent vertebrae in a deployed configuration. The device  1000  may use a threaded shaft  1054  and two or more keyed parts  1040  that are internally threaded and move in different directions when the threaded shaft  1054  is turned. This motion allows the fixation members  1028 , which may be attached to the keyed parts  1040 , to deploy in an anterior-superior and anterior-inferior direction as shown ( FIG.  16 A ), as well as in the posterior-superior and posterior-inferior directions ( FIG.  16 C ), if preferred. 
       FIGS.  17 A  and B show an alternative interbody spinal fusion device  1100  that includes an internal pivoting hook member  1128  which is made to pivot by an actuation member  1136 . The interbody fusion device  1100  may include any of the fusion devices described herein.  FIG.  17 A  depicts a side view of a spacer body  1112  including hook member  1128  retracted within the spacer body  1112 .  FIG.  17 B  shows a side view of the spacer body  1112  with the hook member  1128  extending therefrom and into an adjacent vertebra in a deployed configuration. The translation or actuation member  1136  is configured to translate and push the pivoting hook  1028  outward such that it is configured to grip an intervertebral member. The actuation member  1136  may include a ramped surface or beveled tip to provide for uniform movement of the hook member  1128 . The actuation member  1136  may be threaded or pushed, and may be locked into position to deploy the hook member  1128 . 
       FIGS.  18 A-E  show an alternative interbody spinal fusion device  1200  that includes deployable fixation members  1228 , such as tangs.  FIG.  18 A  depicts a front view of a spacer body  1212  with fixation members  1228  configured to extend superiorly and inferiorly. The fixation members  1228  may be pressed through the spacer body  1212  (e.g., made of PEEK) and embedded into adjacent vertebral bodies. The fixation members  1228  may be tapered such that a distal end of the fixation member  1228  is narrower than a proximal portion of the fixation member  1228  residing within the spacer body  1212 . The distal end of the fixation member  1228  may have a sharpened edge to facilitate insertion into the adjacent vertebrae.  FIG.  18 B  depicts a side view of the spacer body  1212  with the fixation members  1228  extended therethrough. As shown in FIG.  18 C, the fixation members  1228 , for example, in the form of tangs, can be prevented from moving out of the spacer body  1212  by one or more spring retainers  1222  on the fixation members  1228  and/or on the spacer body  1212 . The spring retainers  1222  may include a flexible portion that flexes as the fixation member  1228  is inserted into the device  1200 . As shown in  FIG.  18 E , the fixation member  1228  could also be locked in position through a third component, such as a blocking mechanisms  1220  (e.g., a blocking screw). The fixation members  1228  may also be locked in position by locking the proximal ends together as shown in  FIG.  18 D . The fixation members  1228  may include tangs that are flat or curved. The fixation members  1228  may be made from metal including hydroxyapatite (HA) coated metal. 
     To assist in providing easy insertion of the fusion devices above, various instruments are provided. In particular, the instruments help facilitate inline operation. In many locations of the spine, such as the most caudal or most cephalad cervical disc spaces (e.g., C5-C6/C6-C7 and C2-C3), it can be hard to insert the fusion devices due to interferences with the chin or chest. The same is true for caudal lumbar levels (e.g., L5-S1), where insertion can be complicated due to interference with tissue. The following descriptions include alternative interbody fusion devices, some of which facilitate inline operation. 
       FIG.  19    illustrates an interbody fusion device  1300  having one mechanism for facilitating inline operation. The fusion device  1300  comprises a spacer body  1312  with an end member  1350 . The device  1300  includes a combination of two angled holes  1366  in the spacer body  1312  and corresponding straight holes  1368  in the end member  1350 . A fixation member, such as a bone screw having a polyaxial head and a shaft attached thereto, is insertable through the end member  1350  and the spacer body  1312 . During insertion, the bone screw would be inserted straight with an appropriate sleeved instrument. As the bone screw is inserted, the sleeve will move back and expose the polyaxial head of the bone screw. As the bone screw is inserted further, the shaft of the screw hits one of the predrilled angled holes  1366  in the spacer body  1312  while the polyaxial head engages the straight hole  1368  in the end member  1350 . In other words, the addition of a polyaxial head on the bone screw allows the shaft to angle through the angled holes  1366 . In some embodiments, the shaft is threaded and can engage an adjacent vertebral body. Using this design, the interbody fusion device  1300  can be inserted via an inline operation until the shaft of the bone screw angles down the angled hole  1366 . 
       FIGS.  20 A and  20 B  illustrate a universal joint (e.g., a ball joint) that can be built in the head  1431  of a bone screw  1430  to provide polyaxial adjustability. In some embodiments, the universal joint can be used with the embodiment in  FIG.  19    to provide a polyaxially adjustable bone screw  1430 . The screw head  1431  can comprise a spherical trough  1429  with a slot perpendicular to the longitudinal axis of the screw  1430  which mates with a screw driver  1480 , for example, having projections configured to mate with the trough  1429 . This design allows for driving of the bone screw  1430  into a fusion device at any angle, thereby allowing the shaft of the driver  1480  to remain parallel to a disc space if desired. 
       FIG.  21    illustrates how deployable fixation members, such as nails, fins etc. can be actuated by a worm drive. In particular, the worm drive may include a worm  1546  and/or worm wheel  1548  with teeth at an angle. The worm  1546  may be in the form of a screw, which meshes with the worm wheel  1548 . The worm wheel  1548  may have a wheel-like body with a plurality of teeth positioned along the periphery of the body and which radially extend outward. The worm wheel  1548  may have teeth machined at an angle configured to interlock with the worm  1546 . 
       FIG.  22    illustrates fixation members, such as spikes  1528 , having one or more deployable barb wires  1572 . The barb wires  1572  may be deployed through the spike  1528 . For example, the spike  1528  may be hammered in through the spacer body  1512 , and the barbs  1572  may be deployed simultaneously or after the spike  1528  has been fully implanted. The barbs  1572  may extend through a distal portion of the spike  1528 . The ends of the barbs  1572  may have a sharp point, and the barbs  1572  may be curved to enhance fixation. The spikes  1528  may be curved or straight, and may include any of the fixation members described herein. 
       FIG.  23    illustrates an alternative interbody fusion device including a straight or curved rack and pinion mechanism with an inline actuated pinion  1576  driving a curved or straight rack  1574  into a vertebral body. The rack  1574  has a longitudinal body and includes a plurality of teeth on at least one side of the rack  1574 . The pinion  1576  has a wheel-like body with a plurality of teeth positioned along the periphery of the body and which radially extend outward. The pinion  1576  translates rotation motion (e.g., from a driver) to linear or curvilinear movement of the rack  1574 , thereby causing the rack  1574  to be deployed into the adjacent vertebral space. In this case, the rack  1574  may be acting and functioning as the fixation member. 
       FIG.  24    illustrates a keeled connection between a spacer and a vertebral body. The keeled connection may include a plurality of keels  1578 , for example, which are deployable from the superior and/or inferior surfaces of the device. The keels  1578  may be in the form of teeth, ridges, ribs, extensions, fins, or the like. The keels  1578  may include a sharp edge to further purchase into the bone of the adjacent vertebrae. The keels  1578  can be deployed similar to any of the fixation members including nails, shims, or fins as discussed above. 
     There are many different features to the present invention and it is contemplated that these features may be used together or separately. Unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. Thus, the invention should not be limited to any particular combination of features or to a particular application of the invention. Further, it should be understood that variations and modifications within the spirit and scope of the invention might occur to those skilled in the art to which the invention pertains. Accordingly, all expedient modifications readily attainable by one versed in the art from the disclosure set forth herein that are within the scope and spirit of the present invention are to be included as further embodiments of the present invention.