Abstract:
A medical device, method and system are provided for stabilizing and/or for fusing bone material, such as vertebra of the spine. The medical device (fusion device) has a pair of clamp members and an optional anchor member that cooperate to securely attach the fusion device to a facet joint of the spine. The fusion device may slide down a guide wire and driven into facet bone material of a facet joint. The clamp members may be pivoted together to grip adjacent bone facets and promote their fusion. Further features include injecting flowable bone fusion material between adjacent bone facets gripped by the device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application relates to, and claims the benefit of the filing date of, co-pending U.S. provisional patent application Ser. No. 60/947,746 entitled FACET FUSION IMPLANT, filed Jul. 3, 2007, the entire contents of which are incorporated herein by reference for all purposes. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates in general to skeletal stabilization systems, and in particular to implants, surgical guides, delivery instruments and methods for delivering and attaching implants to bony structures such as a facet of a vertebrae. 
       BACKGROUND INFORMATION 
       [0003]    The use of posterior rigid fixation devices for the stabilization of the spine has become very popular. Pedicle screw fixation has been the gold standard for posterior stabilization for more than two decades. However, the safety of pedicle screw fixation has come into question. Tissue damage during insertion, screw mal-position, and the potential risk of neurologic and vascular injury have been reported in the literature. The use of a less invasive means of fixation could reduce or prevent the risks involved with pedicle screw fixation. 
       SUMMARY 
       [0004]    A medical device, method and system are presented for securing such surfaces as bone material of a spine, such as for posterior stabilization or for fusing various segments of the spine. The medical device (facet fusion device) may have a pair of pivotable clamp members and an anchor member that interrelate to securely attach the facet fusion device to, say, a face joint of the spine. Further, the facet fusion device may have a head to help increase force exertion on the bone material. The facet fusion device may have other features which may allow for (flowable) bone fusion material to be injected into the bone. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following Detailed Description taken in conjunction with the accompanying drawings, in which: 
           [0006]      FIG. 1  is a front perspective view of one possible embodiment of an facet fusion device; 
           [0007]      FIG. 2  is a detailed exploded view of one embodiment of a component which may be incorporated into the facet fusion device of  FIG. 1 ; 
           [0008]      FIG. 3  is an exploded view of one possible embodiment of the facet fusion device of  FIG. 1 ; 
           [0009]      FIG. 4  is a side cross sectional view of one possible embodiment of the facet fusion device of  FIG. 1  in a first position; 
           [0010]      FIG. 5  is a side cross sectional view of one possible embodiment of the facet fusion device of  FIG. 1  in a second position; 
           [0011]      FIG. 6A  is a perspective view one possible embodiment of an instrumentation system which may be used with the facet fusion device of  FIG. 1 ; 
           [0012]      FIG. 6B  is a cross sectional view of the instrumentation system of  FIG. 6A  engaged to the facet fusion device of  FIG. 1 ; 
           [0013]      FIG. 7A  is a flow diagram that illustrates one possible method of delivering a facet fusion device; 
           [0014]      FIG. 7B  is a perspective view of the facet fusion device of  FIG. 1  secured to a facet joint; and 
           [0015]      FIG. 7C  is a posterior view of a segment of the spine with two facet fusion devices of  FIG. 1  secured to a pair of facet joints and an interbody spacer implanted between two adjacent vertebrae. 
       
    
    
       [0016]    It is important to note the drawings are not intended to represent the only aspect of the invention. Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the invention is intended to encompass within its scope such processes, machines, manufacture, compositions of matter, means, methods, or steps. 
       DETAILED DESCRIPTION 
       [0017]    Specific examples of components, methods, and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to limit the invention from that described in the claims. Well-known elements are presented without detailed description in order not to obscure the present invention in unnecessary detail. For the most part, details unnecessary to obtain a complete understanding of the present invention have been omitted inasmuch as such details are within the skills of persons of ordinary skill in the relevant art. 
         [0018]    Turning now to  FIG. 1  there is presented a front perspective view of one possible embodiment of a facet fusion device  500 . The facet fusion device  500  may incorporate a closure member  100  and a pair of clamp members  200  and  250 . The facet fusion device  500  may be utilized along with other instruments and implants to stabilize or fuse various segments of the spine. Accordingly, the closure member  100  and the pair of clamp members  200  and  250  may interrelate to securely attach the facet fusion device  500  to a facet joint of a spine to provide for adequate stabilization or fusion. 
         [0019]    Referring to  FIG. 2 , there is presented a detailed perspective view of one possible embodiment of the closure member  100 . In certain embodiments the closure member  100  may be a one piece integral design or may be assembled from different components, as shown. The closure member  100  may incorporate a fastener  10  and a head  50 . The fastener  10  may be coupled to the head  50  prior to or during implantation of the facet fusion device  500  into the spine. The fastener  10  may have an inner surface defining a bore  12  there though that extends along a longitudinal axis of fastener  10 . The fastener  10  may have a distal bone anchoring portion  20  at a first end and a coupling element  30  at a second end. The bone anchoring portion  20  may be a threaded fastener (as shown), a tack, a plate, a hook, a staple or other anchoring means known to those skilled in the art. In other embodiments, the fastener  10  may have a corkscrew or spiral type design (as shown in  FIG. 1 ) or may have a traditional thread design. The proximal end of fastener  10  may have an inner surface that defines a non circular recess  40  which may be utilized as a driving means to drive the fastener  10  into or between boney structures. In other embodiments the insertion of fastener  10  may be accomplished with an external driving means. Various geometries may be used for the driving means such as torc, hex, stars, oblong, rectangular, square, and collar shapes. 
         [0020]    In certain embodiments, the head  50  may have a spherical outer surface  60  and an inner surface defining a bore  52 . In other embodiments the head  50  may include a wedge or a cone design, as will be explained in greater detail below. In certain embodiments, the inner surface of the head  50  may have a distal threaded section  70  to receive the coupling element  30  of the screw  10 . The proximal coupling element  30  may have a threaded external surface that engages the threaded section  70  of the head  50 . The inner surface of the head  50  may also define non circular recess  80  which may be utilized as a driving means to transfer torque to the head  50  or the screw  10 . In other embodiments torque transfer may be accomplished with an external driving means. Various geometries may be used for the driving means such as torc, hex, stars, oblong, rectangular, square, and collar shapes. 
         [0021]    Now turning to  FIG. 3  an exploded view of the facet fusion device  500  is shown illustrating the fastener  10 , the head  50 , the pair of clamp members  200  and  250  and a bushing  300 . Each of the pair of clamp members  200  and  250  may have a first end or proximal end and a second end or distal end. The proximal end of each clamp member  200  and  250  may have an engagement surface  220  and  270 . In certain embodiments, the distal end may have a clamping portion  210  and  260  with bone gripping surfaces. The bone gripping surfaces may include spikes, textured surfaces or other protrusions which may penetrate and grip or fuse to a boney structure. 
         [0022]    In certain embodiments the first clamp member  200  may have a pair of arms  230  and  240  located between the first and second ends that extend out in a first direction and define a channel between the arms. The pair of arms  230  and  240  may have an attachment member or feature, such as a pin or a slot. In certain embodiments the second clamp member  250  may have a pair of arms  280  and  290  located between the first and second ends that extend out in a second direction and defines a channel between the arms. The pair of arms  280  and  290  may each have an attachment member or feature, such as a pin or a slot that mates with a corresponding attachment feature on the pair of arms  230  and  240  of the first clamp member  200  which may allow the clamp members  200  and  250  to pivot in relation to each other. In certain embodiments one pair of arms  280  and  290  (or  230  and  240 ) may be dimensioned to receive or surround the other pair of arms  230  and  240  (or  280  and  290 ). 
         [0023]    In certain embodiments the facet fusion device  500  may incorporate a bushing  300 . The bushing  300  may have an inner surface  310  and outer surface  320 . The inner surface  310  may define a bore. The inner surface  310  may be threaded to engage the threaded surface of coupling element  30  of the fastener  10 . The outer surface  320  may be at least partially spherical and dimensioned to be received within the channel created by the pair of arms  230  and  240  and/or  280  and  290 . 
         [0024]    Turning to  FIG. 4 , a cross sectional view of the facet fusion device  500  is shown illustrating a first position. In certain embodiments, in the first position, the facet fusion device  500  may have a distance “D 1 ” between the distal clamping portions  210  and  260 . The clamping members  200  and  250  may attach to a boney structure (not shown), such as with a pair of facets (facet joint). The distance “D 1 ” may be dimensioned to allow the facets to be received between the distal clamping portions  210  and  260 . 
         [0025]    In certain embodiments, the bushing  300  may be captured between the pair of clamping members  200  and  250 . The bone anchoring portion  20  of fastener  10  may pass through the bore of the bushing  300  and may be advanced into or between boney structures (not shown). The bone anchoring portion  20  of the fastener  10  may secure the facet fusion device  500  to the boney structure. As the fastener  10  is advanced into or between the facets (as an example or a boney structure) at least a portion of the coupling element  30  may engage the threaded bore of the bushing  300 . 
         [0026]    Turning to  FIG. 5  a cross sectional view of the facet fusion device  500  is shown illustrating a second position. In the second position the facet fusion device  500  may have a distance “D 2 ” between the distal clamping portions  210  and  260 . In certain embodiments the head  50  may threadingly engage the coupling element  30  of the screw  10 . As the head  50  is threaded to the coupling element  30  (see, e.g.  FIG. 4 ), the spherical outer surface  60  may exert a force against engagement surfaces  220  and  270  of the clamping members  200  and  250 . The force may cause one or both of the clamping members  200  or  250  to pivot in relation to the other clamping member  200  or  250 , which may result in the clamping positions  210  and  260  to move to the second position. 
         [0027]    In certain embodiments D 2  may be less than D 1  which may result in the distal clamping portions  210  and  260  clamping or compressing a boney structure (not shown). The compression of bone by the distal clamping portions  210  and  260  may result in creating a localized area of denser bone for improved fixation of fastener  10 . In certain embodiments the final implanted facet fusion device  500  may result in multiple points of fixation. For example the screw  10 , the first clamping member  200  and the second clamping member  250  may all aid in securing the facet fusion device  500  to a boney structure. In other embodiments the facet fusion device  500  may be used as a clamp without a bone anchoring portion  20  of the fastener  10 . In yet other embodiments a fastener  10  may be used without the first clamping member  200  and the second clamping member  250 . 
         [0028]    In certain embodiments the head  50  may have a first position and a second position. When the head  50  is in the first position there may be little or no force exerted against the engagement surfaces  220  and  270 . The head  50  may engage and exert a greater force against the engagement surfaces  220  and  270  in the second position. Other embodiments of force transfer mechanisms, such as the head  50 , are also possible which do not utilize a spherical head. The head  50  may be generally cylindrical in shape and may taper to act as a wedge to exert force against the engagement surfaces  220  and  270 . The head  50 , for example, may have a cam surface that has a first non engagement position and a second engagement position which exerts a force against engagement surfaces  220  and  270 . In another embodiment, a wedge member may be inserted between and exerts a force against the two engagement surface  220  and  270 . In yet another embodiment a scissor jack or rack and pinion type mechanism may be used to exert a force against engagement surfaces  220  and  270 . In still other embodiments, closure type devices may slide over and compress the clamping members  200  and  250  to move clamping portions  210  and  260 . 
         [0029]    Turning now to  FIGS. 6A and 6B  one embodiment of a delivery instrument system  2000  is shown which may be used to deliver the facet fusion device  500  to an implantation site. In certain embodiments the delivery instrument system  2000  may include the guide wire  600 , a driver  2100  and a counter torque instrument  2200 . The driver  2100  may include an inner driver  2110  having a longitudinal bore dimensioned to receive the guide wire  600  and an outer driver  2120  having a longitudinal bore dimensioned to receive the inner driver, as shown in  FIG. 6B . The inner driver  2110  may engage the fastener  10  and aid in the insertion of fastener  10  into or between boney structure(s). The outer driver  2120  may engage the head  50  and aid in securing the head  50  to the fastener  10 . 
         [0030]    The counter torque instrument  2200  may act as a cannula (access device) and/or a counter torque arm. The counter torque instrument  2200  may have a handle and an elongated portion having an inner surface defining a non circular bore (eg rectangular, square or oblong). The facet fusion device  500  may pass down the guide wire  600 , through the noncircular bore of the counter torque instrument  2200  and to the implantation site (boney structure). Alternatively, the facet fusion device  500  may slide over the guide wire to the implantation site and then the counter torque instrument  2200  may pass over the guide wire and engage the first end of clamping members  200  and  250 . The outer surface of the facet fusion device  500  may correspond to the geometry of the non circular bore of the counter torque instrument  2200  which may act to prevent the facet fusion device from rotating relative to the counter torque instrument  2200 . For example, the counter torque instrument  2200  may prevent the facet fusion device  500  from rotating while the fastener  10  and/or the head  50  are inserted and tightened. 
         [0031]    Referring to  FIG. 7A , a flow diagram is shown illustrating one possible embodiment of a method for delivering the facet fusion device  500 .  FIG. 7B , illustrates one embodiment of the facet fusion device  500  delivered and secured to a portion of a spine  700  with the delivery system  2000 . A surgeon may start with incision step  752  to aid in access to a pair of facets  720  and  750 , of a facet joint. The surgeon may insert a guide wire  600  into a facet or between two facets of a facet joint as shown in step  755  and  FIG. 6B . In step  760 , the facet fusion device  500  may be delivered to the facet joint with a guide wire  600 . In addition to or in lieu of a guide wire  600 , a surgeon may use a cannula to deliver the facet fusion device  500 . The facet fusion device  500  may slide down the guide wire to the facet joint (or other boney structure) for implantation. The guide wire may pass through the bore  310  of the bushing  300  (see, e.g.  FIG. 3 ) and the bore of the fastener  10 . The facet fusion device  500  may be delivered to the facet joint without the head  50  (see  FIG. 4 ) or may be partially coupled to the fastener  10  and later tightened. 
         [0032]    In step  760 , the driver  2100  and the counter torque instrument  2200  may couple to the facet fusion device  500  (see, e.g.,  FIG. 6A ,  6 B), as previously described. The driver  2100 , counter torque instrument  2200  and the facet fusion device  500  may slide along the guide wire  600  to a location adjacent to the facets  720  and  750  (e.g.  FIG. 7B ) as shown in step  765 . The facet fusion device  500  may provide for solid fixation of the facets  720  and  750  with an internal and an external fixation means. As previously described, a first fixation member, such as the fastener  10  may be secured between the first facet  720  and the second facet  750  as shown in step  770 . The first fixation member (for example, the fastener  10 ) may exert an outward force on the two facets  720  and  750  pushing them apart from each other. The counter torque instrument  2200  (e.g.  FIGS. 6A ,  6 B) may stabilize the facet fusion device  500  as the fastener  10  is being inserted. 
         [0033]    As shown in step  775 , a second fixation member (such as the clamping members  200  and  250 ) may clamp against the first and second facets  720  and  750  (e.g.  FIG. 7B ). The head  50  (e.g.  FIGS. 3 ,  5 ) may be inserted and/or tightened to increase the clamp force on the facets  720  and  750 . The second fixation member (for example, the clamping members  200  and  250 ) may exert an inward force against the two facets  720  and  750 , which may compress the two facets  720  and  750  toward each other. The counter torque instrument  2200  may stabilize the facet fusion device  500  as the head  50  is inserted and/or tightened. 
         [0034]    The securing of the first and second fixation members can be performed in any order. For example, in one embodiment the second fixation member (for example, the clamping members  200  and  250 ) may be secured first followed by the first fixation member, such as the fastener  10 . The clamp members  200  and  250  may exert a compressive force on the facets  720  and  750  which may compact the bone of the facets  720  and  750  to allow for increased fixation of the fastener  10 .  FIG. 7B  shows the facet fusion device  500  implanted, illustrating the fastener  10  secured between the facets  720  and  750  and the clamp members  200  and  250  secured around the facet. After the procedure is completed the guide wire  600  may be removed. 
         [0035]    For additional fixation the surgeon in step  780  may insert bone fusion material, such as, BMP (bone morphogenetic protein), autograft or allograft bone ceramic materials, bone cement or other bone ingrowth promoting material between the two facets  720  and  750 . In certain embodiments the fastener  10  may be cannulated to allow for a flowable bone fusion material to be injected between the facets  720  and  750 . The bone fusion does not necessarily have to be liquid, but may be composed of very small solid pieces. A perforated or corkscrew shaped fastener  10  may allow for improved delivery of bone fusion material. In alternative embodiments the bone fusion material may be a solid material which may be inserted between the two facets  720  and  750  prior to inserting facet fusion device  500 . 
         [0036]    As shown in step  785  of  FIG. 7A , the facet fusion device  500  may be used in conjunction with other fusion devices to give three column support for improved stabilization. An interbody fusion device may be inserted between two adjacent vertebra to aid in fusing the same or adjacent level of the facet fusion device(s)  500 . Referring to  FIG. 7C , one embodiment of a system for fusion of a pair of adjacent vertebrae  800  and  900  is shown illustrating multiple fusion devices. The facet fusion device  500  is shown implanted to a pair of facet joints on either side of a spinous process  850 . An interbody fusion device  1000  may be inserted between two adjacent vertebra to aid in fusing the same or an adjacent level of the facet fusion device(s)  500 . An interbody spacer  1000  is shown implanted within the disc space of the pair of adjacent vertebrae  800  and  900 . The interbody spacer  1000  may be an ALIF (Anterior Lumbar Interbody Fusion), PLIF (Posterior Lumbar Interbody Fusion), or TLIF (Transforaminal Lumbar Interbody Fusion) spinal fusion device to promote fusion between the adjacent vertebrae  800  and  900 . The interbody spacer  1000  may be inserted before or after the insertion of the facet fusion devices  500 . This method may result in multiple points of fusion to better stabilize the vertebrae  800  and  900 . This method may also result in less surgical time and smaller incisions due to the small size of the facet fusion device  500  and the easy access to the facet joints. 
         [0037]    In certain embodiments the facet fusion device  500  may be manufactured using conventional manufacturing techniques such as machining, molding, welding, etc. The facet fusion device  500  may be manufactured from metals (such as stainless steel or titanium), plastics (such as PEEK or UHMWPE) or a combination. In certain embodiments the distal clamping portion may be manufactured from a flexible material to better match the contour of the anatomy being clamped. The delivery instrumentation system  2000  may be manufactured using convention manufacturing techniques such as machining, molding, welding, etc. The delivery instrumentation system  2000  may be manufactured from metals (such as stainless steel or titanium), plastics (such as PEEK or Radel) or a combination. 
         [0038]    Although only a few exemplary embodiments of this disclosure have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this disclosure. Also, features illustrated and discussed above with respect to some embodiments can be combined with features illustrated and discussed above with respect to other embodiments. Accordingly, all such modifications are intended to be included within the scope of this disclosure.