Abstract:
Anterior cervical corpectomy plates are provided. An exemplary place comprises a fixing member for fixing the plate to a portion of a cervical spine and an adjustable member for adjusting a length of the plate.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application is based on and claims priority to co-pending U.S. provisional patent application entitled, “Anterior Cervical Corpectomy Plate,” having serial No. 60/410,783, filed Sep. 13, 2002, which is entirely incorporated herein by reference. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The present invention generally relates to surgical instruments and, in particular, relates to anterior cervical corpectomy plates.  
         DESCRIPTION OF THE RELATED ART  
         [0003]    The human spine is composed of a column of thirty-three bones, called vertebra, and their adjoining structures. The twenty-four vertebrae nearest the head are separate bones capable of individual movement and are generally connected by anterior and posterior longitudinal ligaments and by discs of fibrocartilage, called intervetebral discs, positioned between opposing faces of adjacent vertebrae. The twenty-four vertebrae are commonly referenced in three sections. The cervical spine, closest to the head and often referenced as the “neck,” comprises the first seven vertebrae of the spine. The thoracic spine and the lumbar spine are below the cervical spine. Each of the vertebra include a vertebral body and a dorsal arch, which enclose an opening, called the vertebral foramen, through which the spinal cord and the spinal nerve pass. The remaining nine vertebrae below the lumbar spine are fused to form the sacrum and the coccyx and are incapable of individual movement.  
           [0004]    Degenerative changes in the cervical spine are not uncommon. Such changes are often caused by the intervertebral discs wearing out and beginning to collapse or herniate, and becoming less flexible. Common causes of cervical spine disorders include arthritis, injuries or trauma, and in some cases spinal cord compression, tumors, or spinal infection. Pain caused by these and other maladies can be lessened or eliminated by a cervical corpectomy.  
           [0005]    A cervical corpectomy is the removal of vertebral bodies and surrounding intervertebral discs which are causing pressure on the spinal cord. Upon removal, autograft, or allograft bone or spacer is disposed in the void left by the removed material. Once the graft is disposed in the opening, the cervical spine is stabilized, typically with either a cervical collar (brace) or a metal plate, to help promote fusion of the graft to remaining vertebrae. Typically, a metal plate of non-variable length is screwed into the vertebra above and below the graft, usually with two screws at each contact location. Loosening of an attached plate is not uncommon, especially in long fusion, with such little anchorage of the plate. These plates also either fail to allow for any settling, or they allow for very limited, but not controlled, settling.  
           [0006]    Current translation plates that do allow for settling have elongated, or ovular, apertures through which the screws fixing the plate to the vertebrae above and below the bone graft are disposed. As settling occurs, the plate slides along the screws as allowed by the length of the aperture. As such, where settling occurs, the plate used is longer than necessary resulting in excess plate length extending above and/or below the bone graft.  
           [0007]    Thus, a heretofore undaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.  
         SUMMARY  
         [0008]    Anterior cervical corpectomy plates are provided. An embodiments of the present invention provide an anterior cervical corpectomy plate comprises a fixing member for fixing the plate to a portion of a cervical spine and an adjustable member for adjusting a length of the plate.  
           [0009]    Other systems, methods, features and/or advantages will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be protected by the accompanying claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    Many aspects can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.  
         [0011]    [0011]FIG. 1 illustrates a perspective view of an embodiment of an anterior cervical corpectomy plate.  
         [0012]    [0012]FIG. 2 illustrates a side view of the embodiment of the anterior cervical corpectomy plate illustrated in FIG. 1 mounted in position.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]    [0013]FIG. 1 illustrates one preferred embodiment of an anterior cervical corpectomy plate  10 . FIG. 2 illustrates the plate  10  mounted in position on a portion of a cervical spine  100 .  
         [0014]    More specifically, and with reference to FIG. 1, the anterior cervical corpectomy plate  10  (hereinafter, “the plate”) comprises a first plate member  12  and a second plate member  14 . First plate member  12  comprises a first mount  16  and a first support member  18  extending therefrom. The first mount  16  comprises a plurality of apertures  20  disposed therethrough. Although five apertures  20  are illustrated, it should be understood that any number of apertures  20  can be included. However, it is desirable that a plurality of apertures  20  are included for increased anchor strength of the plate  10 . The first support member  18  comprises a substantially rigid, elongated channel  22 .  
         [0015]    Second plate member  14  comprises a second mount  24  and a second support member  26  extending therefrom. The second mount  24  comprises a plurality of apertures  28  disposed therethrough. Although five apertures  28  are illustrated, it should be understood that any number of apertures  28  can be included. However, it is desirable that a plurality of apertures  28  are included for increased anchor strength of the plate  10 . The apertures  20  of the first mount  16  and the apertures  28  of the second mount  24  are adapted to each receive a screw  32  therein for fixing the plate  10  in position, as illustrated in FIG. 2.  
         [0016]    Second support member  26  is a substantially rigid, elongated member adapted to engage and slide axially within the channel  22  of the first support member  18 . It should be understood that the first support member  18  having a channel  22  disposed therein is one example of a configuration providing the desired length variable plate  10 . It should be noted that the variable length attribute of the plate  10  can be achieved through various configurations, all of which are within the spirit of the present invention.  
         [0017]    A stop  30  can be included on the plate  10 . As illustrated herein, the stop  30  is disposed on the second support member  26 . It should be understood that the stop  30  can be disposed in any suitable location on the plate  10 . The stop  30  limits the length to which the plate  10  can be decreased thereby limiting the amount of settling of an inserted graft  106  (FIG. 2). Upon the plate  10  reaching the minimum desired length, the stop  30  engages the end of the channel  22  thereby preventing further axial movement of the first support member  18  and the second support member  26  with respect to each other. It is desirable that the stop  30  can be disposed at varying locations along the second support member  26  thereby allowing a surgeon to select the appropriate amount of settling for the patient. The stop  30  can also be stationary.  
         [0018]    In one configuration, the stop  30  can comprise a pin and row of apertures along the length of the second support member  26  through which the pin can be disposed. In this embodiment, the pin can be disposed through the desired aperture corresponding to the desired minimum length of the plate  10 . The pin-and-aperture configuration for the stop  30  is merely one example of a configuration that would allow for variable minimum length selection of the plate  10 . It should be understood that the stop  30  can comprise any suitable configuration without departing from the spirit of the present invention. The plate  10 , stop  30  and screws  32  preferably comprise a substantially rigid, surgical safe material such as stainless steel, or the like.  
         [0019]    [0019]FIG. 1 illustrates but one embodiment of the present invention. Other exemplary embodiments include, but are not limited to, a first support member  24  and second support member  26  having a circular or semi-circular cross-section wherein the first support member  24  and the second support member  26  engage at least each other in a manner to allow for length adjustment. Furthermore, more than a first support member  24  and a second support member  26  can be included and can be formed of any suitable size and shape. The embodiments can also include various configurations and locations for points of contact of the anterior cervical corpectomy plate  10  to vertebral bodies comprising the cervical spine  100 .  
         [0020]    [0020]FIG. 2 illustrates the embodiment of the plate  10  of FIG. 1, fixed on a portion of a cervical spine  100 . The post-corpectomy cervical spine  100 , as illustrated, comprises an intervertebral disc  102  disposed on a vertebral body  104 . A graft  106  is disposed between the vertebral body  104  and another vertebral body  108  having an untouched intervertebral disc  110  disposed therebelow. The cervical spine  100  can continue both above and below the illustrated portion with alternating vertebral bodies and vertebral discs. It should be noted that the space between vertebral body  104  and vertebral body  108  can represent the removal of any amount of vertebral bodies and intervertebral disc(s).  
         [0021]    The plate  10  is configured to the desired length by fitting the second support member  26  into the channel  22  of the first support member  18  and sliding the second support member  26  axially therein to reach the desired length. The optional stop  30  is disposed in a position to limit compression of the plate  10  to a desired minimum length. The plate  10  is fixed to the cervical spine  100  at the vertebral bodies  104  and  106  above and below the graft  106 . More specifically, the first mount  16  is fixed to vertebral body  104  at the apertures  20  by the screws  32 . Similarly, the second mount  24  is fixed to the vertebral body  108  at the apertures  28  by the screws  32 . As stated above, it is preferable that a plurality of screws  32  are disposed through a plurality of apertures  20  disposed in the first mount  16  and a plurality of apertures  28  disposed in the second mount  24  to fix the plate  10  to the cervical spine  100 . The first support member  18  and the second support member  26  axially slide with respect to each other toward each other as the graft  106  settles during fusion. The stop  30  disposed at a pre-determined position along the second support member  26  controls the amount of settling allowed.  
         [0022]    It should be emphasized that the above-described embodiments of the present invention, particularly, a “preferred” embodiment, are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiment(s) of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein with the scope of this disclosure and the present invention and protected by the following claims.