Abstract:
A modular spinal implant for stabilizing the spine is inserted between adjacent vertebrae after the removal of the intervertebral disk. The implant has a main body that may be connected with one of several different sized inserts to maintain or attain a desired spinal orientation. The insert and main body are connected by a fin received within a slot in the main body.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to the field of orthopedic and neuro-surgery and, more particularly, to implants to be placed between vertebrae in the spine.  
         BACKGROUND OF THE INVENTION  
         [0002]    Spinal stabilization is one approach to alleviating chronic back pain caused by displaced disk material or excessive movement of individual vertebrae. Conventional stabilization techniques include fusing two or more vertebrae together to circumvent or immobilize the area of excessive movement. Normally, the vertebral disk material which separates the vertebrae is removed and bone graft material is inserted in the space for interbody fusion. In addition to or, in place of, the bone graft material, a spinal implant may be inserted in the intervertebral space.  
           [0003]    The conventional surgical approach for stabilization has been posteriorly for ease of access to the spine and to avoid interfering with internal organs and tissue. As the art of spinal implants has expanded, different implant design has allowed or dictated other surgical approaches for proper placement of the implant and correct stabilization of the spine.  
         DESCRIPTION OF THE PRIOR ART  
         [0004]    U.S. Pat. No. 6,120,506 issued Sep. 19, 2000 to Kohrs et al discloses a lordotic implant and a tap for use in preparing the vertebrae. The implant is designed to be inserted between the non-parallel end plates of adjacent vertebrae and maintain the natural lordotic angle of the spine. This is done through the use of a threaded tapered plug inserted in a tapped hole in the direction required by the lordosis of the spine. The implant is hollow and has radial apertures for accommodating bone graft material.  
           [0005]    U.S. Pat. No. 6,015,436 issued Jan. 18, 2000 to Shoenhoeffer discloses a tubular spinal implant. The implant is hollow and has radial apertures for interbody fusion through bone growth material. The device is placed between adjacent vertebrae with the opposite ends of the tube contacting the opposing vertebrae. The opposite ends are threaded together to form the hollow tube.  
         SUMMARY OF THE INVENTION  
         [0006]    A modular spinal implant for stabilizing the spine by insertion between adjacent vertebrae after the removal of the intervertebral disk. The implant has a main body that may be connected with one of several different sized inserts to maintain or attain a desired spinal orientation. The main body is inserted between adjacent vertebrae with the fixed insert extending anteriorly therefrom for engaging the opposing surfaces of adjacent vertebrae.  
           [0007]    Accordingly, it is an objective of the instant invention to teach a lateral anterior surgical approach for placement of a particularly shaped spinal implant for interbody fusion.  
           [0008]    It is a further objective of the instant invention to teach a spinal implant having lateral and anterior support for adjacent vertebrae.  
           [0009]    It is yet another objective of the instant invention to teach an implant facilitating interbody fusion through bone graft or an ingrowth-type implant, such as bone inductive material.  
           [0010]    Other objectives and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0011]    [0011]FIG. 1 shows an exploded view of the implant of this invention;  
         [0012]    [0012]FIG. 2 is a perspective of an alternate construction of the implant of this invention;  
         [0013]    [0013]FIG. 3 is a side view of the implant in position within a spine;  
         [0014]    [0014]FIG. 4 is a superior view, partly in section, of the implant in position; and  
         [0015]    [0015]FIG. 5 is a side view of the implant showing apertures. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    The spinal implant  10  may be placed between two adjacent vertebrae, labeled L- 4  and L- 5 , in FIG. 3, approaching the spine surgically by an lateral approach. After the vertebrae have been visualized, the disk material between the vertebrae is removed and the opposing vertebral surfaces prepared by reaming and sizing. This surgical procedure would also include the alignment or orientation of the opposing surfaces to relieve stress and/or pain. A spinal implant would be chosen from a selection of sizes to best accommodate the intervertebral space of the patient. In so choosing the implant, several main bodies may be paired with several inserts until the best combination is achieved for each patient.  
         [0017]    The main body  11 , shown in FIG. 1, is cylindrical however, it may be of other shapes. Rather than cylindrical, the main body may be shaped as a rod or a solid configuration, as shown in FIG. 2. The rounded outer shape is preferred in the event of some minor movement of the vertebrae. The main body has a length approximating the width of the vertebrae, as shown in FIG. 3. The wall of the main body has a slot  12  which extends from one end toward the other end. The slot terminates in and end wall  13 . The edges  14  and  15  of the slot may be parallel to each other. As shown in FIG. 2, the edges  16  and  17  of the slot are sloped to define a keystone cross section. The keystone slot is used with a keystone shaped fin  18 . Also shown in FIG. 2, the slot  12  extends throughout the length of the main body  11 . The keystone shaped slot and fin cooperate to form a simple interlocked fit which cannot separate.  
         [0018]    In FIG. 1, the insert  19  has an integral fin  20  attached to an interlock  21 . The interlock  21  is sized to the internal diameter of the main body  11  and the fin  20  has a thickness similar to the width of the slot  12 . One end of the main body has an aperture  22  which has internal threads  23 . A closure plug  24  has external threads  25  to engage the internal threads  23 . After selection of a suitable insert, the interlock is slid into the main body with the fin extending through the slot. The closure is then threaded into the aperture with the closure plug forcing the interlock and fin against the end wall of the main body. This forms a rigidly coupled modular unit of appropriate size.  
         [0019]    As shown in FIG. 4, the insert has a rounded anterior wall  26  approximating the shape of the intervertebral space. The rounded anterior wall joins opposing planar faces  27  and  28  enclosing a space with a volume similar to the size of the intervertebral disk material. As shown in FIG. 5, the anterior wall may have small apertures  29  therethrough. The space my be filled with bone growth material, including bone grafts, to accelerate the fusion of the implant to the spine by bony ingrowth. The anterior wall and the wall of the main body may be provided with a surface treatment to promote bony ingrowth in addition or as an alternative to the apertures. This treatment could be in the form of a roughened surface and/or coatings of compositions enhancing bone growth.  
         [0020]    As shown in FIG. 2, the insert  19  has a similar shape to the main body  11 . The anterior wall  26  has a surface to facilitate bony ingrowth. The keystone fit between the fin and the slot may be a friction fit preventing lateral dislocation. In this regard, the slot and the fin may have a cooperating slope along their respective lengths requiring increasing pressure as they are telescoped together.  
         [0021]    It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement of parts herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and drawings.