Expandable interbody implant

Abstract

An intervertebral implant that can be surgically introduced between adjacent vertebrae and expanded in situ to occupy an optimal space between the vertebrae. The implant is inserted into the evacuated disc space obliquely and then oriented so as to extend laterally across the anterior adjacent vertebrae with its outer ends of the implant supported by the cortical rims on the opposite sides of the vertebrae. The implant has two body members with a space therebetween so the implant may be then distracted and a spacer of predetermined thickness that may be inserted within the space between the body members so as to maintain a desired amount of distraction. The upper and lower surfaces of the implant may have a desired lordotic angle. A method of using an implant is disclosed which permits endoscopic visualization of the disc space.

1 . An expandable spinal implant for insertion in a disc space between two adjacent vertebrae bodies to be fused together by bone graft material placed in said disc space, said vertebrae bodies each having a cortical rim, said disc space being defined by an annulus attached to said adjacent vertebrae bodies, said implant comprising an elongate body having a height and a width such that said implant is capable of being inserted into the disc space through an incision in the annulus, and said implement having a length such that said implant is at least in part supported by at least two spaced locations on at least one of said cortical rims of said vertebrae bodies when the implant is installed in the disc space, said implant having a lower body member and an upper body member each of which is adapted to be cooperable with a distractor for distraction of said body members while said implant is within said disc space a desired amount such that the disc space is correspondingly distracted, said implant further comprising a spacer configured to be inserted into said disc space through said incision in said annulus and to be positioned between said upper and lower body members when the upper and lower body members are distracted within said disc space such that said implant with said spacer installed between said upper and lower body members maintains said adjacent vertebrae bodies in a distracted state. 
     
     
         2 . An implant as set forth in  claim 1  wherein said incision is in a posterolateral portion of said annulus and wherein said implant is of such a length that with one end of the implant received in a first opening in said annulus generally opposite said incision, with said implant oriented to extend across said vertebrae bodies, and with the other end of said implant at least partially received in a second opening in said annulus generally opposite said first opening such that said implant is at least in part supported on said cortical rims. 
     
     
         3 . An implant as set forth in  claim 1  wherein one of said body members has an inner surface and a pair of stabilizing posts extending from said inner surface and the other of said body members has a pair of bores for receiving said stabilizing posts, said posts and said bores being configured to maintain said body members in desired relation to one another and yet permitting distraction and retraction of the body members relative to one another. 
     
     
         4 . An implant as set forth in  claim 3  wherein each said bore has a sliding axial fit relative to its respective said post so as to aid in stabilizing said body members relative to one another and so as to permit distraction and retraction of said body members relative to one another. 
     
     
         5 . An implant as set forth in  claim 4  wherein each said bore has a flange extending inwardly of said bore, said flange having a flange bore therethrough, and wherein each of said posts has an enlarged head on its distal end, said head being somewhat larger than said flange bore so that with the post inserted in said flange bore said flange bore and said head cooperate so as to prevent said post from becoming dislodged from said bore, and wherein each of said posts has a slot therein permitting said post to be at least partially compressed so that said head on said post may be inserted through its respective flange bore. 
     
     
         6 . An implant as set forth in  claim 1  wherein one of said body members has an inner surface and a tab extending from said inner surface, whereupon said tab being engaged by said spacer said tab preventing anterior movement of said spacer beyond said tab. 
     
     
         7 . An implant as set forth in  claim 6  wherein the other of said body members has a groove formed therein for receiving said tab upon retraction of said implant. 
     
     
         8 . An implant as set forth in  claim 1  having means for limiting movement of said spacer relative to said body members beyond a predetermined position relative to said body members. 
     
     
         9 . An implant as set forth in  claim 8  wherein said means for limiting movement of said spacer comprises at least one extension extending laterally from one end of said spacer, said extension cooperating with an adjacent said post so as to limit anterior or posterior movement of said spacer relative to said body members. 
     
     
         10 . An implant as set forth in  claim 9  having one of said extensions extending from each lateral end of said spacer with each of said extensions cooperating with a respective said post so as to limit anterior or posterior movement of said spacer relative to said body members. 
     
     
         11 . An implant as set forth in  claim 10  wherein at one end of said spacer a pair of extensions extend from said one end where the extensions comprising said pair are spaced from one another a distance wider than the thickness of a respective said post received therebetween so that said spacer may be inserted between said body members at an angle such that a respective post is received between said pair of extensions and thereafter said spacer may be further inserted between said body members to that said extension at the other end of said spacer engages its respective post thereby to limit movement of said spacer relative to said body members. 
     
     
         12 . An implant as set forth in  claim 8  wherein said means for limiting movement of said spacer relative to said body members comprises said spacer and at least one of said body members having a pair of cooperating members, one of said cooperating members being a male protuberance and the other of said other of said cooperating members being a female recess with said recess receiving said protuberance upon retraction of said implant thereby to limit movement of said spacer relative to said body members. 
     
     
         13 . An implant as set forth in  claim 1  wherein said spacer and one of said body members having at least one pair of cooperating members, wherein one of said cooperating members is located on a surface of said spacer and the other of said cooperating members is located on an adjacent inner surface of one of said body members, wherein one of said cooperating members is a male protuberance and wherein said other of said cooperating members is a female recess for receiving said protuberance thereby limiting movement of said spacer relative to said one body member upon retraction of said implant. 
     
     
         14 . An implant as set forth in  claim 13  wherein spacer said and said one body member having two pairs of said cooperating members for limiting movement and rotation of said spacer and said one body member relative to one another. 
     
     
         15 . An implant as set forth in  claim 13  wherein said male protuberance has a generally convex shape, and wherein said female recess has a generally concave shape such that upon retraction of said body members and upon the application of compression to said implant, said protuberance and its respective said recess cooperate with one another so as to locate said spacer in a desired general location between said body members and so as to positively retain said spacer relative to said one body member. 
     
     
         16 . An implant as set forth in  claim 15  wherein said female recess, when viewed in plan, is larger than its respective said male protuberance. 
     
     
         17 . An implant as set forth in  claim 16  wherein upon the reception of said male protuberance within its respective said female recess, the concave shape of said female recess acts as a cam and the convex shape of said male protuberance acts as a cam follower cooperable with said cam such that upon the application of a compressive load to said implant, the cooperation of each said male protuberance with its respective said female recess tends to self-locate said spacer in a desired general location relative to said body member. 
     
     
         18 . An implant as set forth in  claim 17  wherein said female recess is sufficiently large such that with said spacer positioned between said body members, upon retraction of said implant said male protuberance will be received within its respective said female recess such that cooperation of said male protuberance in its said female recess will move said spacer relative to said body members to its said desired general location between said body members. 
     
     
         19 . An implant as set forth in  claim 13  wherein with each said protuberance received in its respective recess and with a compression load applied to said implant, said protuberance and its recess prevents said spacer from becoming dislodged from the space between said body members. 
     
     
         20 . A spinal implant for insertion in a disc space between two adjacent vertebrae bodies, said disc space being defined by an annulus wall attached to said adjacent vertebrae bodies, each of said vertebrae bodies having an cortical rim and an endplate within its cortical rim, said implant comprising an elongate body that may be inserted within the disc space through an incision in a posterolateral portion of said annulus wall, with one end of the implant being at least partially received in a first opening formed in the anterior annulus wall generally opposite said incision, said implant being maneuverable within said disc space so that with said implant being oriented so that with its said one end remaining in register with said first opening and so that with said implant extending generally laterally of said vertebrae bodies its other end being at least partially received within a second opening in said annulus wall generally opposite said first opening such that said implant is least in part supported on the cortical rim of at least one of said vertebrae bodies, said implant having a lower body member and an upper body member, each of said body members being adapted to receive an operating blade of a distractor so that upon operation of said distractor said body members are forced apart a desired amount so as to in turn distract the disc space, said implant further comprising a spacer of a predetermined thickness that may be inserted through said incision into said disc space and positioned between said upper and lower body members while said body members are distracted. 
     
     
         21 . An implant as set forth in  claim 20  wherein said outer surfaces of said upper and lower bodies are angled relative to the horizontal thereby to form a predetermined lordotic angle such that said implant may be used to introduce or maintain lordosis in the reconstructed disc space. 
     
     
         22 . An implant as set forth in  claim 21  wherein said lordotic angle may range between about 0° and about 12°.