Abstract:
A radially expandable spinal interbody device for implantation between adjacent vertebrae of a spine is deliverable to an implant area in a radially collapsed state having minimum radial dimensions and once positioned is then radially expandable through and up to maximum radial dimensions. The expanded radially expandable spinal interbody device is configured to closely mimic the anatomical configuration of a vertebral face. The radially expandable spinal interbody device is formed of arced, pivoting linkages that allow transfiguration from the radially collapsed minimum radial dimensions through and up to the radially expanded maximum radial dimensions once deployed at the implant site (i.e. between adjacent vertebrae). The pivoting linkages have ends with locking features that inhibit or prevent overextension of the linkages. In one form of the locking features, one end of the linkage includes lobes that form a pocket while the other end of the linkage includes a projection that is adapted to be received in the pocket of the lobes of an adjacent linkage. A kit is also provided including a tool for the implantation and deployment of the spinal interbody device into an intervertebral space.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application is a continuation-in-part of U.S. application Ser. No. 13/585,521, filed Aug. 14, 2012, which is a continuation-in-part of U.S. application Ser. No. 12/079,737, filed Mar. 28, 2008, which claims the benefit of U.S. Provisional Patent Application No. 60/920,766, filed Mar. 29, 2007. The entire contents of all of these applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     The present invention relates to spinal interbody devices for implantation between a pair of adjacent vertebrae for providing support to the adjacent vertebrae for fusion thereof and, more particularly, to expandable interbody devices for implantation between a pair of adjacent vertebrae for providing support to the adjacent vertebrae for fusion thereof. 
     The disc between vertebrae of a human spine may become damaged due to disease, injury, stress, deterioration because of age or otherwise, or due to a congenital defect. In some instances vertebrae may become compressed against a disc or otherwise become damaged. The spine may thereby become mis-aligned. In these and other cases the vertebrae can become too closely spaced anteriorly which causes an undesired abnormal curvature of the spine with respect to lordosis or kyphosis. Other deformations and/or problems may occur. 
     In these cases and more, spinal fusion surgery may be utilized to join or fuse two or more vertebrae together. Fusion surgeries typically require the use of bone graft to facilitate fusion. This involves taking small amounts of bone from the patient&#39;s pelvic bone (autograft), or from a donor (allograft), and then packing it between the vertebrae in order to “fuse” them together. This bone graft is typically packed into a biomechanical spacer implant, spinal prosthesis or interbody device, which will take the place of the intervertebral disc which is entirely removed in the surgical process. Spinal fusion surgery is a common treatment for such spinal disorders as spondylolisthesis, scoliosis, severe disc degeneration, or spinal fractures. Three common fusion surgeries are 1) Posterior Lumbar Interbody Fusion or PLIF; 2) Anterior Lumbar Interbody Fusion or ALIF; and 3) Transforaminal Lumbar Interbody Fusion (TLIF). 
     In the PLIF technique, the vertebrae are reached through an incision in the patient&#39;s back (posterior). The PLIF procedure involves three basic steps. One is pre-operative planning and templating including use of MRI and CAT scans to determine what size implant(s) the patient needs. Two is preparing the disc space. Depending on the number of levels to be fused, a 3-6 inch incision is made in the patient&#39;s back and the spinal muscles are retracted (or separated) to allow access to the vertebral disc. The surgeon then removes some or all of the affected disc and surrounding tissue. Third is insertion of the implant(s). Once the disc space is prepared, bone graft, allograft or BMP with a biomechanical spacer implant, is inserted into the disc space to promote fusion between the vertebrae. Additional instrumentation (such as rods or screws) may also be used to further stabilize the spine. 
     The TLIF technique is a refinement of the PLIF procedure and is used as a surgical treatment for conditions typically affecting the lumbar spine. The TLIF technique involves approaching the spine in a similar manner as the PLIF approach but more from the side of the spinal canal through a midline incision in the patient&#39;s back. This approach greatly reduces the amount of surgical muscle dissection and minimizes the nerve manipulation required to access the vertebrae, discs and nerves. The TLIF approach allows for minimal access and endoscopic techniques to be used for spinal fusion. Disc material is removed from the spine and replaced with bone graft (along with cages, screws, or rods if necessary) inserted into the disc space. The instrumentation helps facilitate fusion while adding strength and stability to the spine. 
     The ALIF procedure is similar to PLIF procedure however, the ALIF procedure is done from the front (anterior) of the body, usually through a 3-5 inch incision in the lower left lower abdominal area. This incision may involve cutting through, and later repairing, the muscles in the lower abdomen. This technique also lends itself to a mini open approach that preserves the muscles and allows access to the front of the spine through a very small incision and use of endoscopic technology. This approach maintains abdominal muscle strength and function. It is therefore oftentimes used to fuse the L 5 -S 1  disc space. As such, it can be appreciated that the smaller the interbody device the better. 
     When interbody devices are used, it is desirable for them to engage as much surface of the bone of the vertebrae as possible to provide support to the vertebral bone and to thereby reduce the likelihood of subsidence of the device into the bone resulting from contact pressure of the interbody device against bone surfaces. Subsidence can occur since part of the bone is somewhat spongy in nature, especially near the centers of the adjacent vertebrae. 
     The structure of interbody devices mainly functions to support the two adjacent vertebral surfaces, unless the interbody device is also used as a fusion cage within or around which to pack bone fusion material. Because it is also desirable in such structures to maintain weight and volume as low as possible in order to make the device more compatible with the body, it is also desirable to make the interbody device as small and lightweight as possible, while still maintaining strength. 
     Accordingly, there presently exists a need for improved interbody devices. 
     SUMMARY 
     The present invention is a radially expandable spinal interbody device for implantation between adjacent vertebrae of a spine. The radially expandable interbody device is deliverable to an implant area in a radially collapsed state having minimum radial dimensions and once positioned is then radially expandable through and up to maximum radial dimensions. The expanded radially expandable spinal interbody device is configured to closely mimic the anatomical configuration of a vertebral face. 
     The radially expandable spinal interbody device is formed of arced, pivoting linkages that allow transfiguration from the radially collapsed minimum radial dimensions through and up to the radially expanded maximum radial dimensions once deployed at the implant site (i.e. between adjacent vertebrae). The pivoting linkages have ends with locking features that inhibit or prevent overextension of the linkages. In one form of the locking features, one end of the linkage includes lobes that form a pocket while the other end of the linkage includes a projection that is adapted to be received in the pocket of the lobes of an adjacent linkage. 
     In one form, the radially expandable spinal interbody device utilizes two like linkages that are pivotally connected to one another at opposite ends thereof. Each linkage is preferably, but not necessarily, formed of two pivotally connected arced links. The links each have serrations or teeth on upper and lower surfaces. The links are connected via pivot pins that also provide markers when formed of a radio opaque material such as tantalum. 
     The radially expandable spinal interbody device is made from a bio-compatible material such as titanium, a titanium alloy, stainless steel, other metal, polymer, composite, ceramic or a combination thereof as appropriate. The radially expandable interbody device  10  is preferably, but not necessarily, used as a lumbar interbody device and/or for use in ALIF surgery. 
     A surgical tool is provided for positioning and deploying the radially expandable interbody device/implant. The surgical tool has a positioning portion adapted to releasably attach to the radially expandable interbody device and a deployment portion movably retained by the positioning portion and adapted to deploy the radially expandable interbody device. The deployment portion is also adapted to introduce bone graft, BMP or the like into the radially expandable interbody device. 
     Releasable attachment to the radially expandable interbody device is accomplished in one form through multi-directional installation threads of a bore of each link. Since each link includes a threaded bore, various rotational orientations may be achieved during implantation. 
     Some embodiments are directed to a spinal interbody device comprising a base link having a first end and a second end; a linkage comprising a first link having a first end coupled to the first end of the base link and a second end; a second link having a first end coupled to the second end of the first link and a second end coupled to the second end of the base link; and an adjustment screw provided in the second end of the base link and configured to engage the second end of the second link to move the linkage between a collapsed position and an expanded position. 
     Another embodiment is directed to a spinal interbody device comprising a first link; a second link pivotally coupled to the first link; a third link having a first end and a second end, wherein the first link is coupled to the first end and configured to pivot and translate relative to the third link, wherein the second link is coupled to the second end and configured to move only in a pivoting fashion relative to the third link; wherein the second end of the third link is configured to engage a projection of the second link. 
     Another embodiment is directed to a spinal interbody device comprising a unitary base link having a first end and a second end, the first end having a first channel defined by a wall having a slot, the second end having a second channel defined by a pair of walls with apertures therein; a first link having a projection extending into the first channel of the base link; a second link pivotally coupled to the first link, the second link having a projection extending into the second channel of the base link; wherein the first link pivots and translates relative to the base link, and the second link moves only pivotally relative to the base link; wherein the first and second links are configured to move between a collapsed position and an expanded position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above mentioned and other features, advantages and objects of this invention, and the manner of attaining them, will become apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of an exemplary embodiment of a radially expandable spinal interbody device fashioned in accordance with the present principles. 
         FIG. 2  is an exploded view of the components of the radially expandable spinal interbody device of  FIG. 1 . 
         FIG. 3  is a top view of the radially expandable spinal interbody device of  FIG. 1 . 
         FIG. 4  is a side view of the radially expandable spinal interbody device of  FIG. 3  taken along ling  4 - 4  thereof. 
         FIG. 5  is a side view of the radially expandable spinal interbody device of  FIG. 3  taken along line  5 - 5  thereof. 
         FIG. 6  is a sectional view of the radially expandable spinal interbody device of  FIG. 1  taken along line  6 - 6  thereof. 
         FIG. 7  is a sectional view of an implantation and deployment device for use with the radially expandable spinal interbody device of  FIG. 1 . 
         FIG. 8  is an illustration of a stage in a method of use of the radially expandable spinal interbody device of  FIG. 1  utilizing the implantation and deployment device of  FIG. 7  wherein the radially expandable spinal interbody device is in a pre-expanded or collapsed state adjacent a vertebra. 
         FIG. 9  is an illustration of another stage in the method of use of the radially expandable spinal interbody device of  FIG. 1  utilizing the implantation and deployment device of  FIG. 7  wherein the radially expandable spinal interbody device is in an expanded or un-collapsed state adjacent the vertebra. 
         FIG. 10  is a perspective view of a radially expandable spinal interbody device according to another exemplary embodiment. 
         FIG. 11  is a top view of the device of  FIG. 10  in a radially collapsed configuration according to an exemplary embodiment. 
         FIG. 12  is a cross-sectional view of the device of  FIG. 11  according to an exemplary embodiment. 
         FIG. 13  is a top view of the device of  FIG. 10  is a radially expanded configuration according to an exemplary embodiment. 
         FIG. 14  is a cross-sectional view of the device of  FIG. 13  according to an exemplary embodiment. 
         FIG. 15  is a side view of the device of  FIG. 10  in a radially expanded configuration according to an exemplary embodiment. 
         FIG. 16  is a side view of the device of  FIG. 10  in a radially collapsed configuration according to an exemplary embodiment. 
         FIGS. 17-18  are exploded perspective views of the device of  FIG. 10  according to exemplary embodiments. 
         FIGS. 19-20  are perspective views of a spinal interbody device according to another embodiment. 
         FIG. 21  is a top view of the device of  FIG. 19  according to one embodiment. 
         FIG. 22  is a cross-sectional view of the device of  FIG. 19  according to one embodiment. 
         FIG. 23  is a cross-sectional perspective view of the device of  FIG. 19  according to one embodiment. 
         FIG. 24  is another perspective view of the device of  FIG. 19  according to one embodiment. 
         FIG. 25  is a side view of the device of  FIG. 19  according to one embodiment. 
     
    
    
     Like reference numerals indicate the same or similar parts throughout the several figures. 
     A full dissertation of the features, functions and/or configuration of the components depicted in the various figures will now be presented. It should be appreciated that not all of the features of the components of the figures are necessarily described. Some of these non-discussed features as well as discussed features are inherent from the figures. Other non-discussed features may be inherent in component geometry and/or configuration . . . 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Referring to the Figures and in particular  FIGS. 1-6 , there is depicted an exemplary embodiment of a radially expandable interbody device, spinal prosthesis or the like generally designated  10  fashioned in accordance with the present principles. The radially expandable interbody device  10  is configured to be delivered to an implant site in a radially collapsed state or with radially minimal dimensions  200  (see, e.g.,  FIG. 8 ) and then radially expanded or with radially maximum dimensions  300  at the implant site (see, e.g.,  FIG. 9 ) hence the term expandable or dynamic. In this manner, the radially expandable interbody device  10  may be delivered to the implant site through a small delivery area when in the radially collapsed state and then easily radially expanded when implanted. The radially expandable interbody device  10  may be fashioned from a biocompatible material such as titanium, a titanium alloy, stainless steel, other metal, polymer, composite, ceramic and/or any combination thereof. The radially expandable interbody device  10  is preferably, but not necessarily, used as a lumbar interbody device and/or for use in an ALIF surgery. 
     The radially expandable interbody device  10  is defined by a first linkage  13  that is coupled to a second linkage  15 . The first linkage  13  is radially pivotally coupled to the second linkage  15  at first ends thereof to define a first radial pivot junction or juncture  17 , and at second ends thereof to define a second radial pivot junction or juncture  19 . The first linkage  13  is defined by a first pair of links  12  and  14 , while the second linkage  15  is defined a second pair of identical links  12  and  14 . The first and second links  12  and  14  of the first linkage  13  are radially pivotally connected to one another to define a third radial pivot junction or juncture  21 . Likewise, the first and second links  12  and  14  of the second linkage  15  are pivotally connected to one another to define a fourth radial pivot junction or juncture  23 . The ends of the first and second linkages  13  and  15  are pivotally connected to one another. In this manner, the linkages  13  and  15  are able to radially collapse in on themselves to a minimum radial size or dimension  200  and radially expand outwardly to a maximum radial dimension or size  300  as defined by a lock mechanism between the links  12 ,  14  which also provides an overextension feature (lobes with a pocket on one end thereof and a projection on the other end thereof). As best seen in  FIG. 8 , the curvature and pivoting of the connected links  12  and  14  of the first and second linkages  13  and  15 , when collapsed, defines a “figure 8” or minimum radial dimension (see, e.g.  FIG. 8 ). As best seen in  FIG. 3 , the curvature of the connected links  12  and  14  of the first and second linkages  11  and  13 , when expanded, defines an ovoid interior  99  that defines a maximum radial dimension of the radially expandable interbody device  10 . This shape approximates the end anatomy of a spinal disc (see, e.g.,  FIG. 9 ). The links  12  and  14  are joined via hinge or pivot pins  16  (see, e.g.  FIG. 2 ) made of an appropriate biocompatible material. The hinge pins  16  may provide reference markers on the interbody device and as such would be made from a marker-distinctive material (a radio opaque material) such as tantalum. Other materials may be used. 
     The first link  12  is defined by a generally curved body  20  having a serrated or toothed upper surface  22  and a serrated or toothed lower surface  24 . The upper and lower serrations  22  and  24  are directional (see, e.g.,  FIGS. 1, 2 and 3 ). The body  20  defines an inner curved surface  26  and an outer curved surface  28 . A multi-directional threaded bore  30  is provided in the body  20 . The longitudinal axis of the bore  30  is essentially perpendicular to the arc of the body  20 . In order to provide connectivity at one end of the body  20  of the link  12  to another link (i.e. link  14 ), the body  20  has an upper hinge or flange  32  on one end thereof. The upper hinge  32  is generally rounded, defines an undersurface  34 , and has an axial bore  38  extending from the upper surface  22  through the upper hinge  32  to the lower surface  24 . As best seen in  FIG. 2 , the upper hinge  32  has a ridge or projection  36  that extends axially along the upper hinge  32 . When assembled, the ridge  36  of the first link  12  co-acts with a channel, or groove or pocket  94  in the end  92  of lobes of the second link  14  to provide a lock mechanism to prevent the device from over opening or extending. The body  20  also has an end surface  40  that is below the lower surface  34  of the upper hinge  32 . The end surface  40  has an axial groove, channel or pocket  42  of lobes thereof. The groove  42  co-acts with a ridge  86  of a lower hinge  84  of the second link  14  that again provides a lock mechanism to prevent the device from over opening or over extending. 
     In order to provide connectivity at another end of the body  20  of the link  12  to another link (i.e. link  14 ), the body  20  has a lower hinge or flange  44  on another end thereof. The lower hinge  44  is generally rounded, defines an upper surface  48 , and has an axial bore  50  extending from the upper surface  48  through the lower hinge  44  to the lower surface  24 . As best seen in  FIG. 2 , the lower hinge  44  has a ridge or projection  46  that extends axially along the lower hinge  44 . When assembled, the ridge  46  of the lower hinge  44  of the first link  12  co-acts with a channel, groove or pocket  82  of lobes in the end  80  of the second link  14  to provide a lock mechanism to prevent the device from over opening or over extending. The body  20  also has an end surface  52  that is above the upper surface  48  of the lower hinge  44 . The end surface  52  has an axial groove, channel or pocket  54  of lobes thereof. The groove  54  co-acts with a ridge  76  of an upper hinge  72  of the second link  14  that again provides a lock mechanism to prevent the device from over opening or over extending. 
     The second link  14  is defined by a generally curved body  60  having a serrated or toothed upper surface  62  and a serrated or toothed lower surface  64 . The upper and lower serrations  62  and  64  are directional (see, e.g.,  FIGS. 1, 2 and 3 ). The body  60  defines an inner curved surface  66  and an outer curved surface  68 . A multi-directional threaded bore  70  is provided in the body  60 . The longitudinal axis of the bore  70  is essentially perpendicular to the arc of the body  60 . In order to provide connectivity at one end of the body  60  of the link  14  to another link (i.e. link  12 ), the body  60  has an upper hinge or flange  72  on one end thereof. The upper hinge  72  is generally rounded, defines an undersurface  74 , and has an axial bore  78  extending from the upper surface  62  through the upper hinge  72  to the lower surface  74 . As best seen in  FIG. 2 , the upper hinge  72  has a ridge or projection  76  that extends axially along the upper hinge  72 . When assembled, the ridge  76  of the second link  14  co-acts with the channel, groove or pocket  54  of lobes in the end  52  of the second link  12  to provide a lock mechanism to prevent the device from over opening or over extending. The body  60  also has an end surface  80  that is below the lower surface  74  of the upper hinge  72 . The end surface  80  has an axial groove, channel or pocket  82  of lobes thereof. The groove  82  co-acts with the ridge  46  of the lower hinge  44  of the first link  12  that again provides a lock mechanism to prevent the device from over opening or over extending. 
     In order to provide connectivity at another end of the body  60  of the link  14  to another link (i.e. link  12 ), the body  60  has a lower hinge or flange  84  on another end thereof. The lower hinge  84  is generally rounded, defines an upper surface  88 , and has an axial bore  90  extending from the upper surface  88  through the lower hinge  84  to the lower surface  64 . As best seen in  FIG. 2 , the lower hinge  84  has a ridge or projection  86  that extends axially along the lower hinge  84 . When assembled, the ridge  86  of the lower hinge  84  of the second link  14  co-acts with a channel, groove or pocket  42  of lobes thereof in the end  40  of the first link  12  to provide a lock mechanism to prevent the device from over opening or over extending. The body  60  also has an end surface  92  that is above the upper surface  88  of the lower hinge  84 . The end surface  92  has an axial groove, channel or pocket  94  of lobes thereof. The groove  94  co-acts with the ridge  36  of the upper hinge  32  of the first link  12  that again provides a lock mechanism to prevent the device from over opening or over extending. 
     As depicted in  FIG. 2 , the links  12  and  14  are pivotally connected to one another via the hinge or pivot pins  16  that extend into the respective hinge bores of the links  12 ,  14 . The first linkage  11  includes a first link  12  that is pivotally connected to a second link  14 . Particularly, the upper hinge  32  of the first link  12  is disposed over the lower hinge  84  of the second link  14  such as to align bores  38  and  90  of the upper and lower hinges  32 ,  84  respectively. A pivot pin  16  is then provided in the bores  38 ,  90 . The second linkage  13  also includes a first link  12  that is pivotally connected to a second link  14 . Particularly, the upper hinge  32  of the first link  12  is disposed over the lower hinge  84  of the second link  14  such as to align bores  38  and  90  of the upper and lower hinges  32 ,  84  respectively. A pivot pin  16  is then provided in the bores  38 ,  90 . As well, the first and second linkages  11 ,  13  are pivotally connected to one another and at both ends thereof. Particularly, the upper hinge  72  of the second link  14  of the second linkage  13  is situated over the lower hinge  44  of the first link  12  of the first linkage  11  such that the respective bores  78  and  50  are aligned. A pivot pin  16  is then provided in the bores  78 ,  50 . The upper hinge  72  of the second link  14  of the first linkage  11  is situated over the lower hinge  44  of the first link  12  of the second linkage  13  such that the respective bores  78  and  50  are aligned. A pivot pin  16  is then provided in the bores,  78 ,  50 . The serrations or teeth of the links are oriented to provide directional gripping during implantation and use. Particularly, the serrations of the links are oriented essentially radially when the interbody device is expanded (see, e.g.,  FIG. 3 ). 
     The various hinge ridges or projections of the links  12 ,  14  and end grooves or channels of the links  12 ,  14  provide various features/functions for the radially expandable interbody device  10 . In one form, the hinge ridges and end groove form expansion stops for the radially expandable interbody device  10  and particularly for each link relative to other links. An expansion stop is formed by a hinge projection of one link and an end groove of another link. In the collapsed state as in  FIG. 8 , the links  12 ,  14  of the interbody device  10  are oriented such that hinge projections of one link and adjacent end grooves of an adjacent link do not register and thus are free to pivot relative to one another. When the radially expandable interbody device  10  is expanded (see, e.g.,  FIG. 9 ), the links  12 ,  14  pivot such that the hinge projections of one link and adjacent end grooves of an adjacent link do register thus providing a pivot locking mechanism at a maximum expansion of the links. This provides over extension prevention. 
     The version of the interbody device as shown in the figures has four (4) segments or links that form the body thereof. It should be appreciated, however, that the interbody device may be fashioned from additional or more than four segments or links. Thus, the interbody device may be formed of a body having up to n segments or links. 
       FIG. 7  depicts a surgical tool  100  that may be used with and/or for the implantation and deployment of the radially expandable interbody device  10 . Particularly, the surgical tool  100  is used for various implantation functions such as reaming of an implant site, deploying the radially expandable interbody device  10 , and the insertion of bone graft, allograft or BMP within the radially expandable interbody device  10 . The surgical tool  100  is fashioned from an appropriate bio-compatible material such as one or more of those described above. The surgical tool  100  includes a positioning portion  102  and a deploy portion  104 . The positioning portion  102  is defined by a cylindrical body or shaft  108  having a handle  110  formed at one end of the shaft  108  and a tapered end  114  formed at another end of the shaft  108  distal the handle  110 . External threads  116  are formed on the end  114 . These threads are sized to correspond to the threaded bores  30  and  70  of the links  12  and  14  respectively of the interbody device  10 . In this manner, the positioning tool  102  may be threadedly coupled to the interbody device  10  during implantation and orientation. (see, e.g.  FIGS. 8 and 9 ). The shaft  108  has a bore  118  that extends from the end  114  to and through the handle  110 . 
     The deploy portion  104  is defined by a rod  120  extending from a grip  122 . The rod  120  is dimensioned to be received in the shaft bore  118  and extend axially therefrom. The rod  120  has a tapered end  124  at an end of the rod  120  distal the grip  122 . The grip  122  forms a handle that is essentially bulb-shaped. The deploy portion  104  is thus configured to axially move back and forth relative to the positioning portion  102 . When the positioning tool  102  is attached to the radially expandable interbody device  10  and the interbody device  10  has been appropriately placed at an implant site (see, e.g.,  FIGS. 8 and 9 ), axial movement of the deploy portion  104  expands the radially expandable interbody device  10  as shown in an unexpanded state in  FIG. 8 , to the expanded radially expandable interbody device  10  as shown in an expanded state in  FIG. 9 . 
     Referring now to  FIGS. 10-18 , a spinal interbody device  210  is shown according to an exemplary embodiment. Device  210  includes a first link  212 , a second link  214 , and a third or base link  216 . First link  212  is pivotally connected to second and third links  214 ,  216  via pivot pins  218 ,  220 . Similarly, second link  214  is pivotally connected to third link  216  via a pivot pin  222 . Pivot pins  218 ,  220 ,  222  form hinge mechanisms acting between links  212 ,  214 , and  216  such that device  210  can be moved from a first, radially collapsed, or retracted configuration, as shown in  FIG. 2 , to a second, or radially expanded configuration, as shown in  FIG. 4 . Similar to device  10 , device  210  is implantable between adjacent vertebrae in a radially collapsed configuration and, once in proper position, is expandable through and up to a maximum radially expanded position. Device  210  may share many features of device  10 , and all such combinations of features are understood to be within the scope of the present disclosure. 
     According to an exemplary embodiment, first link  212  includes a first end  224  and a second end  226 . Upper and lower surfaces  228 ,  230  and inner and outer surfaces  232 ,  234  extend between first end  224  and second end  226 . Upper and lower surfaces  228 ,  230  include serrations  236  (e.g., grooves, teeth, projections, etc.) that may extend along all or a portion of the length of first link  212  between first end  224  and second end  226  Inner surface  232  may be curved such that when device  210  is expanded, links  212 ,  214 ,  216  form a generally oval-shaped interior. First and second ends  224 ,  226  include projections  238 , each projection  238  having an aperture  240  extending therethrough that is configured to receive one of pivot pins  218 ,  220 . 
     Second link  214  includes a first end  244  and a second end  246 . Upper and lower surfaces  248 ,  250  and inner and outer surfaces  252 ,  254  extend between first end  244  and second end  246 . Upper and lower surfaces  248 ,  250  include serrations  256  (e.g., grooves, teeth, projections, etc.) that may extend along all or a portion of the length of second link  214  between first end  244  and second end  246  Inner surface  252  may be curved such that when device  210  is expanded, links  212 ,  214 ,  216  form a generally oval-shaped interior. First end  244  of second link  214  includes a channel or recess  258  that is configured to receive projection  238  of first link  212 . First end  244  also includes an aperture  264  extending therethrough that is configured to receive pivot pin  220 . Second end  246  of second link  214  includes a projection  260  having an aperture  264  extending therethrough that is configured to receive pivot pin  222 . 
     Third link  116  includes a body  268  having a first end  270  and a second end  272 . Upper and lower surfaces  274 ,  276  and inner and outer surfaces  278 ,  280  extend between first end  270  and second end  272 . First end  270  includes a rounded, narrowed end portion  184  (e.g., a bull nose portion, etc.) that may narrow between upper and lower surfaces  274 ,  276  and/or between inner and outer surfaces  278 ,  280 , and facilitate insertion of device  210  into a desired area within a patient. Upper and lower surfaces  274 ,  276  include serrations  282  (e.g., grooves, teeth, projections, etc.) that may extend along all or a portion of the length of third link  216  between first end  270  and second end  272  Inner surface  278  may be curved such that when device  210  is expanded, links  212 ,  214 ,  216  form a generally oval-shaped interior. 
     First end  270  of third link  216  includes a slot  292  (e.g., an elongated aperture, recess, etc.) that is configured to receive pivot pin  218  and enable pivot pin  218  to pivot and translate within slot  292 . As such, first link  212  is able to move in both a pivoting and translating manner. An end wall  296  limits the pivoting and translational movement of first link  212  relative to third link  216  as device  210  is moved between a radially collapsed position and a radially expanded position. First end  270  further includes a channel, groove, or recess  294  that is configured to receive projection  238  (e.g., lobe, knuckle, hinge portion or member, etc.) on first link  212 . As shown in  FIG. 17 , pivot pin  218  is received within slot  292  in third link  216  and aperture  240  in first link  212 . 
     Second end  272  of third link  216  includes a channel or recess  298  configured to receive projection  260  on second link  214 . As shown in  FIG. 18 , pivot pin  222  is received within aperture  302  in third link  216  and aperture  264  in second link  214 . As such, link  214  is configured to move relative to third link  216  in only a rotating or pivoting manner (and, unlike first link  212 , not in a translating manner) as device  210  moves between a radially collapsed position and a radially expanded position. 
     Second end  272  of third link  216  further includes a screw, or worm,  286  that is received within a bore  288  in second end  272 . Worm  286  is configured to engage gears  262  (e.g., teeth, etc.) on projection  260  of second link  214  such that rotation of worm  286  about its longitudinal axis (e.g., by way of a tool, etc.) causes a corresponding rotation of second link  214  about pivot pin  222 . In this manner the radially collapsing and expanding movement of device  210  can be controlled via rotation of worm  286 , which together with projection  260  and gears  262 , forms a worm drive enabling adjustable control of the expansion of device  210 . Worm  286  may include a suitable recess (e.g., a hex recess, etc.) that enables rotation of worm  286  by any suitable tool (e.g., a screwdriver, etc.). On either side of aperture  290  are a pair of recesses  304 . Recesses  304  may be configured to receive a portion of the insertion tool and prevent rotation of device  210  relative to the tool, thereby enabling a user to manipulate device  210  (e.g., rotate, adjust, etc.). 
     According to an exemplary embodiment, second end  272  of third link  216  further includes an aperture  290 . As shown in  FIG. 14 , aperture  290  may extend through third link  216 , and all or a portion of the length of aperture  290  may be threaded. In some embodiments, aperture  290  is configured to threadingly receive a tool (e.g., an insertion tool, etc.) that may be inserted into aperture  290 , used to properly position device  210  within a patient, and subsequently removed from device  210 . Aperture  290  may further enable the insertion of bone growth or similar materials into the cavity formed by device  210 . Any suitable tool, including tools similar to those disclosed elsewhere herein, may be used in combination with device  210 . 
     In use, device  210  may initially be in a radially collapsed configuration, as shown, for example, in  FIGS. 10-12 and 16 . In the collapsed configuration, pivot pin  220  and the hinge mechanism coupling first link  212  to second link  214  may be adjacent third link  216 . Device  210  may be inserted into a patient in a desired position using a suitable insertion tool. Once in a desired position, device  210  may be radially expanded to an expanded configuration, as shown in  FIGS. 13-15 . To expand/collapse device  210 , a tool may be inserted into worm  286  and rotated, such that rotation of worm  286  causes rotation of second link  214  toward an expanded position. First link  212 , by way of its pivotal linkage to second link  214 , is in turn also moved to an expanded position. In an expanded position, pivot pin  220  and the hinge mechanism coupling first link  212  to second link  214  may extend away from third link  216 . 
     According to one embodiment, first link  212 , second link  214 , and/or third link  216  include motion limiting features intended to limit the range of motion of the links relative to one another. For example, referring to  FIG. 14 , device  210  is shown in a radially expanded configuration. First link  212  includes a lip  242  that may be provided on one or both of upper and lower surfaces  228 ,  230  of first link  212  and that acts to engage second link  214  to limit the relative range of motion between the links. Similarly, second link  214  includes a lip  266  that engages first link  212  to likewise limit the relative range of motion between the links. Third link  216  includes end walls  296 ,  300  that limit the relative range of motion of first link  212  (both pivotally and translationally) and second link  214  (only pivotally). According to various alternative embodiments, other features may be provided to further define and/or limit the range of motion of links  212 ,  214 , and  216 . 
     It should be noted that while the FIGURES generally illustrate device  210  in either a fully radially collapsed position or a fully radially expanded position, according to various alternative embodiments, device  210  is configured to be implanted in any intermediate position between the fully collapsed configuration and the fully expanded configuration. Furthermore, in some embodiments, the worm drive components may be omitted such that device  210  is moved between a fully collapsed configuration and a fully expanded configuration in a similar manner to device  10 . 
     Referring now to  FIGS. 19-25 , a spinal interbody device  310  is shown according to an exemplary embodiment. As shown in  FIGS. 19-22 , device  310  includes a first link  312 , a second link  314 , and a third or base link  316 . First link  312  is pivotally connected to second and third links  314 ,  316  via pivot pins  318 ,  320 . Similarly, second link  314  is pivotally connected to third link  316  via a pivot pin  322 . Pivot pins  318 ,  320 ,  322  form hinge mechanisms acting between links  312 ,  314 , and  316  such that device  310  can be moved from a first, radially collapsed, or retracted configuration, (similar to that shown in  FIG. 2 ), to a second, or radially expanded configuration, as shown in  FIG. 21 . Similar to devices  10  and  210 , device  310  is implantable between adjacent vertebrae in a radially collapsed configuration and, once in proper position, is expandable through and up to a maximum radially expanded position. Device  310  may share many features of device  10  and/or device  210 , and all such combinations of features are understood to be within the scope of the present disclosure. 
     Referring to  FIGS. 22-24 , according to an exemplary embodiment, first link  312  includes a first end  324  and a second end  326 . Upper and lower surfaces  328 ,  330  and inner and outer surfaces  332 ,  334  extend between first end  324  and second end  326 . Upper and lower surfaces  328 ,  330  include serrations  336  (e.g., grooves, teeth, projections, etc.) that may extend along all or a portion of the length of first link  312  between first end  324  and second end  326 . Inner surface  332  may be curved such that when device  310  is expanded, links  312 ,  314 ,  316  form a generally oval-shaped interior. First and second ends  324 ,  326  include projections  338 , each projection  338  having an aperture  340  extending therethrough that is configured to receive one of pivot pins  318 ,  320 . 
     Second link  314  includes a first end  344  and a second end  346 . Upper and lower surfaces  348 ,  350  and inner and outer surfaces  352 ,  354  extend between first end  344  and second end  346 . Upper and lower surfaces  348 ,  350  include serrations  356  (e.g., grooves, teeth, projections, etc.) that may extend along all or a portion of the length of second link  314  between first end  344  and second end  346  Inner surface  352  may be curved such that when device  310  is expanded, links  312 ,  314 ,  316  form a generally oval-shaped interior. First end  344  of second link  314  includes a channel or recess  358  that is configured to receive projection  338  of first link  312 . First end  344  also includes an aperture  364  extending therethrough that is configured to receive pivot pin  320 . Second end  346  of second link  314  includes a projection  360  having an aperture  364  extending therethrough that is configured to receive pivot pin  322 . 
     Third link  116  includes a body  368  having a first end  370  and a second end  372 . Upper and lower surfaces  374 ,  376  and inner and outer surfaces  378 ,  380  extend between first end  370  and second end  372 . First end  370  includes a rounded, narrowed end portion  384  (e.g., a bull nose portion, etc.) that may narrow between upper and lower surfaces  374 ,  376  and/or between inner and outer surfaces  378 ,  380 , and facilitate insertion of device  310  into a desired area within a patient. Upper and lower surfaces  374 ,  376  include serrations  382  (e.g., grooves, teeth, projections, etc.) that may extend along all or a portion of the length of third link  316  between first end  370  and second end  372 . Inner surface  378  may be curved such that when device  310  is expanded, links  312 ,  314 ,  316  form a generally oval-shaped interior. 
     First end  370  of third link  316  includes a slot  392  (e.g., an elongated aperture, recess, etc.) that is configured to receive pivot pin  318  and enable pivot pin  318  to pivot and translate within slot  392 . As such, first link  312  is able to move in both a pivoting and translating manner. An end wall  396  limits the pivoting and translational movement of first link  312  relative to third link  316  as device  310  is moved between a radially collapsed position and a radially expanded position. First end  370  further includes a channel, groove, or recess  394  that is configured to receive projection  338  (e.g., lobe, knuckle, hinge portion or member, etc.) on first link  312 . As shown in  FIG. 23 , pivot pin  318  is received within slot  392  in third link  316  and aperture  340  in first link  312 . 
     Second end  372  of third link  316  includes a channel or recess  398  configured to receive projection  360  on second link  314 . As shown in  FIG. 23 , pivot pin  322  is received within aperture  302  in third link  316  and aperture  364  in second link  314 . As such, second link  314  is configured to move relative to third link  316  in only a rotating or pivoting manner (and, unlike first link  312 , not in a translating manner) as device  310  moves between a radially collapsed position and a radially expanded position. 
     Second end  372  of third link  316  further includes a screw, or worm,  386  that is received within a bore  388  in second end  372 . Worm  386  is configured to engage gears  362  (e.g., teeth, etc.) on projection  360  of second link  314  such that rotation of worm  386  about its longitudinal axis (e.g., by way of a tool, etc.) causes a corresponding rotation of second link  314  about pivot pin  322 . In this manner the radially collapsing and expanding movement of device  310  can be controlled via rotation of worm  386 , which together with projection  360  and gears  362 , forms a worm drive enabling adjustable control of the expansion of device  310 . Worm  386  may include a suitable recess  389 (e.g., a hex recess, etc.) that enables rotation of worm  386  by any suitable tool (e.g., a screwdriver, etc.). 
     According to an exemplary embodiment, worm  386  defines an aperture  390  (e.g., a central aperture, etc.). As shown in  FIG. 23 , aperture  390  may extend through third link  316 . In some embodiments, aperture  390  is configured to receive a tool (e.g., an insertion tool, etc.) that may be inserted into aperture  390 , used to properly position device  310  within a patient, and subsequently removed from device  310 . Aperture  390  may further enable the insertion of bone growth or similar materials into the cavity formed by device  310 . Any suitable tool, including tools similar to those disclosed elsewhere herein, may be used in combination with device  310 . In one embodiment, a portion of aperture  190  is hex shaped to receive a correspondingly-shaped tool. 
     In some embodiments, second end  372  may include a boss, or raised portion  391 . One or more recesses  393 ,  395  may be provided on one or both sides of raised portion  391  to enable grasping of device  310  by a suitable tool. In one embodiment, recesses  393  are provided on opposing sides of boss  391  and provide undercut areas usable to retain an end of a tool. 
     Referring now to  FIGS. 19 and 22 , while in some embodiments one or more of links  312 ,  314 ,  316  may be made of a single material (e.g., PEEK, etc.), in other embodiments, multiple materials may be used to form discreet portions of one or more of links  312 ,  314 ,  316 . 
     For example, as shown in  FIG. 19 , in one embodiment, third link  316  may include a first portion  397  and a second portion  399 . In one embodiment portions  397  and  399  are different materials. For example, first portion  397  may be a polymer (e.g., PEEK) and second portion  399  may be a metal (e.g., titanium, etc.). First portion  397  and second portion  399  may be divided by a dovetail configuration or other separating geometry. In some embodiments, first portion  397  is molded over second portion  399 . In other embodiments, other ways of joining first and second portions  397 ,  399  may be used. 
     Similarly, as shown in  FIG. 22 , in one embodiment, second link  314  may include a first portion  401  and a second portion  403 . In one embodiment portions  401  and  403  are different materials. For example, first portion  401  may be a polymer (e.g., PEEK) and second portion  403  may be a metal (e.g., titanium, etc.). First portion  401  and second portion  403  may be divided by a curved configuration (e.g., U-shaped, etc.) or other separating geometry. In some embodiments, first portion  397  is molded over second portion  399 . In other embodiments, other ways of joining first and second portions  397 ,  399  may be used. 
     Using differing materials for first and second portions may provide added strength where needed, such as with second portion  399  (to retain worm  386 ) and second portion  403  (to interact with worm  386 ). The first and second portions  397 ,  399  and  401 ,  403  may be joined together using any suitable methods, including overmolding, mechanical fasteners, and the like. In one embodiment, pins  407  are used to maintain the first and second portions in position 
     In use, device  310  may initially be in a radially collapsed configuration, as shown, for example, in  FIGS. 10-12 and 16  with respect to device  210 . In the collapsed configuration, pivot pin  320  and the hinge mechanism coupling first link  312  to second link  314  may be adjacent third link  316 . Device  310  may be inserted into a patient in a desired position using a suitable insertion tool. Once in a desired position, device  310  may be radially expanded to an expanded configuration, as shown in  FIGS. 21-23 . To expand/collapse device  310 , a tool may be inserted into worm  386  and rotated, such that rotation of worm  386  causes rotation of second link  314  toward an expanded position. First link  312 , by way of its pivotal linkage to second link  314 , is in turn also moved to an expanded position. In an expanded position, pivot pin  320  and the hinge mechanism coupling first link  312  to second link  314  may extend away from third link  316 . 
     According to one embodiment, first link  312 , second link  314 , and/or third link  316  include motion limiting features intended to limit the range of motion of the links relative to one another. For example, referring to  FIG. 21 , device  310  is shown in a radially expanded configuration. First link  312  includes a lip  342  that may be provided on one or both of upper and lower surfaces  328 ,  330  of first link  312  and that acts to engage second link  314  to limit the relative range of motion between the links. Similarly, second link  314  includes a lip  366  that engages first link  312  to likewise limit the relative range of motion between the links. Third link  316  includes end walls  396 ,  400  that limit the relative range of motion of first link  312  (both pivotally and translationally) and second link  314  (only pivotally). According to various alternative embodiments, other features may be provided to further define and/or limit the range of motion of links  312 ,  314 , and  316 . 
     It should be noted that while the FIGURES generally illustrate device  310  in a fully radially expanded position, according to various alternative embodiments, device  310  is configured to be implanted in any intermediate position between the fully collapsed configuration and the fully expanded configuration. Furthermore, in some embodiments, the worm drive components may be omitted such that device  310  is moved between a fully collapsed configuration and a fully expanded configuration in a similar manner to device  10 . Further yet, while some embodiments illustrate certain components as including both metal and polymer portions, in various alternative embodiments any components may be made of a single material (e.g., a bio-compatible material such as PEEK, titanium, etc.). 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only a preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.