Abstract:
A spinal interbody cage implant includes a cage, an endplate, and flexible barbs. The endplate is separately attached to the cage and is configured to receive, hold and direct a flexible barb into an upper vertebral surface and a flexible barb into a lower adjacent vertebral surface. Each proximal leg of the cage is configured to receive the endplate, and has a lateral bore that receives a pin which retains the endplate. The endplate directs a first flexible barb upwardly toward an upper vertebral surface, and directs a second flexible barb downwardly toward a lower vertebral surface. Each flexible barb has a proximal head, a shaft extending from the head with a bore extending from the head to its distal end. Teeth are provided along the exterior surface of the shaft with two flats disposed on opposite sides thereof with a slit extending from the distal end towards the head.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This U.S. non-provisional patent application claims the benefit of and/or priority under 35 U.S.C. §119(e) to U.S. provisional patent application Ser. No. 62/298,534 filed Feb. 23, 2016 titled “Spinal Interbody Cage Implant With Flexible Barbs,” the entire contents of which is specifically incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to orthopedic implants for the spine and, particularly, to interbody cages for spinal fusion. 
       BACKGROUND OF THE INVENTION 
       [0003]    Many people contend with spine issues as a result of age, disease, and trauma, as well as congenital and acquired complications and conditions. While some of these issues can be alleviated without surgery, other issues respond better to surgery. In some cases, surgery may include placing an implant into the spine. If vertebral fusion is required, a spine implant known as an interbody cage along with bone graft or bone graft material may be used. 
         [0004]    An interbody cage is a device that is placed in the disc space between adjacent vertebrae of a recipient&#39;s spine. The interbody cage includes openings, bores, and/or is porous or the like to permit the introduction and/or carrying of bone graft/bone graft material in order to allow the bone graft/bone graft material to grow from one vertebra through the interbody cage and into the adjacent vertebra. Such interbody cages provide excellent fixation such that most recipients do not require additional implants such as plates and/or bone screws. 
         [0005]    It is desirable that the interbody cage utilize the subchondral bone at the end of the vertebra rather than reaming it away, as this can weaken the disc space and lead to postoperative subsidence of the interbody cage into the vertebrae, causing a loss of fixation. While there are various geometries of interbody cages, a rectangular geometry allows for more surface area between the cage and the cage endplate, which in turn decreases the force per unit area on the cage endplate. Current interbody cages often fail as a result of the endplate not being able to support the stress of the cage. Decreasing the force per unit area should lead to less endplate failures and cage subsidence. 
         [0006]    However, while numerous interbody cages have been designed over the years, they are deficient in many respects. It is therefore an object of the present invention to provide an interbody cage that overcomes the deficiencies of the prior art. 
       SUMMARY OF THE INVENTION 
       [0007]    A spinal interbody cage implant includes a cage, an endplate, and flexible barbs, spikes, or the like (collectively, “barbs”). The endplate is separately attached to the cage and is configured to receive, hold and direct a flexible barb into an upper vertebra and a flexible barb into a lower adjacent vertebra. 
         [0008]    The cage is generally, but not necessarily, U-shaped having a distal cavity and, with attachment of the endplate, a proximal cavity. Upper and lower surfaces of the cage and endplate include serrations or the like that grip respective upper and lower vertebral surfaces. 
         [0009]    The cage has a generally tapered distal end and two proximal legs. Each proximal leg is configured to receive the endplate and has a lateral bore that receives a pin which is received in and retains the endplate. 
         [0010]    The endplate has distal sides that are configured for reception by the two configured proximal legs, a first bore extending from a front of the endplate and configured to direct a flexible barb upwardly toward an upper vertebral surface, and a second bore extending from the front of the endplate and configured to direct a flexible barb downwardly toward a lower vertebral surface. 
         [0011]    Each flexible barb has a proximal head, a shaft extending from the head with a bore extending from the head to its distal end. Teeth or the like are provided along the exterior surface of the shaft with two flats disposed on opposite sides of the shaft along with a slit extending from the distal end towards the head. The head has internal threading that aids in inserting the barb into the cage during implantation. 
         [0012]    The cage and endplate may be made from metal such as titanium, stainless steel or an alloy of either, PEEK, PET or PETE, carbon fiber, or other biocompatible material. The flexible barbs are formed of a flexible biocompatible material such as, but not limited to, PEEK, PET, PETE, or the like. 
         [0013]    Further aspects of the present invention will become apparent from consideration of the drawings and the following description of a form of the invention. A person skilled in the art will realize that other forms of the invention are possible and that the details of the invention can be modified in a number of respects without departing from the inventive concept. The following drawings and description are to be regarded as illustrative in nature and not restrictive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The features of the invention will be better understood by reference to the accompanying drawings which illustrate various views of a form of the present invention, wherein: 
           [0015]      FIG. 1  is a side view of a flexible barb of the present spine interbody cage implant fashioned in accordance with the present principles; 
           [0016]      FIG. 2  is an isometric front side view of the flexible barb of  FIG. 1 ; 
           [0017]      FIG. 3  is an isometric rear side view of the flexible barb of  FIG. 1 ; 
           [0018]      FIG. 4  is an isometric rear side exploded view of a cage and endplate of the present interbody cage implant; 
           [0019]      FIG. 5  is an isometric front top exploded view of the cage and endplate of the present interbody cage implant; 
           [0020]      FIG. 6  is an isometric end side view of the assembled cage and endplate of the present interbody cage implant; 
           [0021]      FIG. 7  is an isometric exploded side view of the assembled cage and endplate along with a flexible barb; 
           [0022]      FIG. 8  is an end side isometric view of the assembled cage and endplate with a flexible barb received in the endplate; 
           [0023]      FIG. 9  is a an end side isometric view of the assembled cage and endplate with two flexible bards received in the endplate; and 
           [0024]      FIG. 10  is an isometric end view of the assembled interbody cage implant of  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]      FIGS. 1-3  show a barb, spike, or the like generally designated  10  (collectively, barb  10 ) that is one component or element of an interbody cage implant  100  (see  FIGS. 9 and 10 ) that is used for the spine and, particularly, in the disc space of adjacent vertebrae of the spine in order to provide and/or promote fusion thereof. The barb  10  is formed of a flexible biocompatible material and is characterized by a generally elongated shaft  11  having a having a head  14  at a proximal end thereof, and a tip  13  at a distal end thereof. The head  14  has an internally threaded socket  20  that allows threaded engagement with a like threaded tool (not shown) for insertion of the barb  10 . 
         [0026]    The shaft  11  has external serrations  12  that extend from the tip  13  to the head  14 . As best seen in  FIG. 1 , the serrations  12  are step-shaped relative to the tip  13  to allow insertion of the barb but prevent the barb from backing out. Other styles of serrations or teeth, however, may be used. A bore  15  extends from the tip  13  to the socket  20  thereby making the barb also a cannula. As seen in  FIG. 2 , one side of the shaft  11  has a flat  17  that extends from the tip  13  to the head  14 . As seen in  FIG. 3 , another side of the shaft  11  also has a flat  19  that extends from the tip  13  to the head  14 . The flats  17  and  19  are preferably, but not necessarily, opposite one another on the shaft  11 . A slot, channel or the like  16  is provided along the flat  17  that extends from the tip  13  to proximate the head  20 . A slot, channel or the like  18  is likewise provided along the flat  19  that extends from the tip  13  to proximate the head  20 . These characteristics of the barb  10  allow the barb to flex without compromising its integrity. 
         [0027]      FIGS. 4 and 5  show an interbody cage assembly  27  in an exploded view that is defined by a cage  23  and an endplate  25 . The cage  23  has a generally U-shaped (but may be different if desired) body  24  having an angled, beveled, or tapered distal end  32 , a first leg  30  extending from a first side of the end  32 , and a second leg  31  extending from a second side of the end  32 , the nomenclature first and second being arbitrary. The first and second legs  30 ,  31  are spaced to receive the endplate  25 . A spur or the like  38  extends between the first and second legs  30 ,  31  to define a cavity  48  between the end  32  and the spur  38 . Serrations, teeth or the like (collectively, serrations)  34  are provided along an upper (superior) side of the first leg  30 , the serrations  34  providing gripping against a lower (inferior) surface of an upper vertebral surface (not shown) when implanted. Serrations, teeth or the like (collectively, serrations)  35  are likewise provided along a lower (inferior) side of the first leg  30 , the serrations  35  providing gripping against an upper (superior) surface of a lower vertebral surface (not shown) when implanted. Serrations, teeth or the like (collectively, serrations)  36  are provided along an upper (superior) side of the second leg  31 , the serrations  35  providing gripping against a lower (inferior) surface of an upper vertebral surface (not shown) when implanted. Serrations, teeth or the like (collectively, serrations)  37  are likewise provided along a lower (inferior) side of the second leg  31 , the serrations  37  providing gripping against an upper (superior) surface of a lower vertebral surface (not shown) when implanted. 
         [0028]    A proximal end  40  of the first leg  30  terminates in an angle, slant or taper  46  and includes a bore  42  that extends from a lower portion of the outside surface thereof to a lower portion of the inside surface thereof. A proximal end  41  of the second leg  31  also terminates in an angle, slant or taper  44  and includes a bore  43  that extends from an upper portion of the outside surface thereof to an upper portion of the inside surface thereof. Each bore  42 ,  43  is sized to receive a pin or the like  28 . The pins  28  retain the endplate  25  onto the first and second ends  40 ,  41  of the cage body  24  as explained below. 
         [0029]    The inside of the angle  44  of the end  41  of the second leg  31  is configured to receive and retain the endplate  25  and, particularly, a side of the endplate  25  as described below. As best seen in  FIG. 4 , the angle  44  has a slot  45  that extends the length of the angle  44  and cuts into the end  41  a depth towards the distal end  32 . While not seen, the inside of the angle  46  of the end  40  of the first leg  30  has the same configuration as the inside of the angle  44  of the end  41  of the second leg  31 . 
         [0030]    The endplate  25  is defined by a body  26  having a generally rectangular cuboid shape. The body  25  has a first boss  52  on a first side of the front (proximal) side thereof, the first boss  52  having a first bore  53  that extends from the front to a rear (distal) side of the body  26 . The first bore  53  projects generally upward from the front to the rear side of the body. As best seen in  FIG. 5 , rearward of the first bore  53  is a surface  57  that slants upwardly. The first bore  53  and surface  57  cooperate to bend a flexible barb  10  upwardly when inserted into and through the first bore  53  (see  FIGS. 8-10 ). The body  25  has a second boss  54  on a second side of the front (proximal) side thereof, the second boss  54  having a second bore  55  that extends from the front to a rear (distal) side of the body  26 . The second bore  55  projects generally downward from the front to the rear side of the body. While not seen in the figures, rearward of the second bore  55  is a surface that slants downwardly (in like manner to the slanted surface  57  but in the opposite direction). The second bore  55  and surface cooperate to bend a flexible barb  10  downwardly when inserted into and through the first bore  53  (see  FIGS. 9-10 ). It should be appreciated that the nomenclature first and second is arbitrary. Moreover, the slant of the first and second bores (and rearward slanting surface) may be reversed, or the body  26  itself may be reversed to that which is shown in the figures. Additionally, the endplate  25  may have more bores that slant a flexible barb into other or the same directions. As best seen in  FIG. 10 , the endplate  25  also has a central bore  56  that accepts an insertion tool (not shown). 
         [0031]    The rear or distal portion of the body  26  has serrations, teeth or the like  50  on an upper (superior) surface thereof that provide gripping against the lower (inferior) surface of the upper vertebra, and serrations, teeth or the like  51  on a lower (inferior) surface thereof that provide gripping against the upper (superior) surface of the lower vertebra when implanted. The rear or distal portion of the body  26  also is configured for reception by and/or on the first and second legs  30 ,  31 . Particularly, and as best seen in  FIG. 5 , a first rear side of the body  26  has a slanted surface  58  that corresponds in angle to the slant  46  of the end  40  of the first leg  30 . A ridge  59  projects from the slanted surface  58  that is configured for reception in the slot (not seen) in the slant  46  of the end  40 . A bore  62  is also provided in the slanted surface  58  below the ridge  59  that aligns with the bore  42  of the first leg  30 . The bore  62  is sized to receive a pin  28 . A second rear side of the body  26  has a slanted surface  60  that corresponds in angle to the slant  44  of the end  41  of the second leg  31 . A ridge  61  projects from the slanted surface  60  that is configured for reception in the slot  45  in the slant  44  of the end  41 . A bore  63  is also provided in the slanted surface  60  above the ridge  61  that aligns with the bore  43  of the second leg  31 . The bore  63  is sized to receive a pin  28 . Again, the nomenclature first and second is arbitrary. 
         [0032]      FIG. 6  shows the cage assembly  27 —i.e. the endplate received onto the cage, with pins installed. With the endplate received onto the legs, a second cavity  49  is defined between the transverse spur  38  and the rear of the endplate.  FIG. 7  shows the cage assembly  27  with a flexible barb  10  ready for insertion into the first bore  53  of the endplate.  FIG. 8  shows the flexible barb  10  received in the first bore of the endplate and bent or flexed upwardly (in the superior direction) by the configuration of the endplate as described above.  FIGS. 9 and 10  show an assembled interbody cage implant  100  with a flexible barb  10  received in the first and second bores of the endplate, with the flexible barb  10  of the first bore bent or flexed upwardly (in the superior direction) by the configuration of the endplate and the flexible barb  10  of the second bore bent or flexed downwardly (in the inferior direction) by the configuration of the endplate as described above. 
         [0033]    It should be appreciated that dimensions of the components, structures, and/or features of the present interbody cage implant may be altered as desired within the scope of the present disclosure.