Abstract:
Spinal fusion system and method utilizing an implant and screw, wherein at least one pawl is mounted on or integral with the screw to prevent said plate or screw from moving in at least one of an axial direction or a rotational direction.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 11/778,284, filed Jul. 6, 2007, which is incorporated herein by reference and made a part hereof. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to a implant plate system, device and locking screw having at least one locking member. The preferred application for the device is in spinal surgery, however, applications in other areas of orthopedic surgery are appropriate. 
         [0004]    2. Description of the Related Art 
         [0005]    Many types of prosthetic devices have been proposed in the past. For example, U.S. Pat. No. 5,192,327 to Brantigan concerns a surgical prosthetic modular implant used singularly or stacked together to support and fuse together adjacent vertebrae or to totally or partially replace one or more vertebrae in a vertebral column. Other surgical implant devices and methods are shown in U.S. Pat. Nos. 4,488,543; 5,192,327; 5,261,911; 5,549,612; 5,713,899; 5,776,196; 6,136,002; 6,159,245; 6,224,602; 6,258,089; 6,261,586; 6,264,655; 6,306,136; 6,328,738; 6,361,537 and 6,592,586. Some or all of these devices have improved the success rate and have simplified the surgical techniques in inter-body veritable fusion. 
         [0006]    U.S. Pat. No. 6,258,089 B1 issued Jul. 10, 2001 to Campbell et al. for an Anterior Cervical Plate And Fixation System discloses an anterior cervical plate is disclosed, along with threaded fasteners for securing the plate to vertebrae or other osseous material. The cervical plate has several pockets or apertures, preferably at least four, to receive a corresponding number of the fasteners. The pockets have spherical surfaces, and the fasteners have heads with similarly sized spherical surfaces, which when engaged permit each of the fasteners to be oriented at a variety of projection angles with respect to the plate. In connection with each pocket, the cervical plate incorporates a fastener retaining feature. The feature can take the form of a cantilevered tab or a beam supported at its opposite ends, in each case plastically deformable between an open position for admitting the fastener and a closed position for preventing retraction. 
         [0007]    U.S. Pat. No. 5,549,612 issued Aug. 27, 1996 to Yapp et al. for Osteosynthesis Plate System discloses an osteosynthesis plate system is particularly well adapted to securely fuse adjacent cervical vertebrae. The plates are adapted for mounting upon the anterior or posterior surfaces of the vertebrae. Plates for mounting on the anterior vertebral surfaces have a concave bone contacting surface and a bone screw locking mechanism integral with each screw hole. Moreover, the bone contacting surface of the plate has a plurality of bone penetrating protrusions to more securely affix the plate to bone. Plates for mounting on the posterior vertebral surfaces also have bone penetrating protections on their bone contacting surfaces. Such plates are formed so as to have a curved bone contacting surface that is concave in the transverse axis of the plate and convex in the longitudinal axis of the plate. The screw holes of such plates are constructed so as to guide a bone screw along a desired angle to improve the anchoring of the screws in bone. 
         [0008]    U.S. Pat. No. 4,488,543 issued Dec. 18, 1984 to Tornier for Device For Osteosynthesis Of Fractures Of The Extremities Of The Femur discloses a device for osteosynthesis of the fractures of the extremities of the femur comprises a plate in which holes are provided for the passage of screws intended to be inserted into the bone to make the fractured bone and the plate solid. One end of the plate to be applied against one of extremities of the femur is wider than the other end and includes three holes arranged in an isosceles triangle. The median plane of the one end defines a plane which forms, with the plane of the rest of the plate, an obtuse angle of between 160° and 175°. 
         [0009]    U.S. Pat. No. 6,361,537 B1 issued Mar. 26, 2002 to Anderson for Surgical Plate With Pawl And Process For Repair Of A Broken Bone discloses a surgical plate and process for preventing screw backout of repaired bones. At least one pawl is provided on a surgical plate adjacent to a screw hole. A screw having a ratchet wheel is inserted through the hole and screwed into the bone. The pawl engages the ratchet wheel to prevent rotational movement of the screw to prevent the screw from backing out. In a preferred embodiment, a pawl plate comprising a base portion is rigidly connected to the surgical plate and a torsion bar is pivotally connected to the base portion. The pawl is positioned at the end of the torsion bar. In the preferred embodiments, several of these special screw holes with pawls, and several screws (each with a ratchet wheel) are used in bone repair. 
         [0010]    While the above approaches may have yielded favorable results in certain circumstances, there remains a need for reducing the need for multiple parts or tools and for providing a simpler, more reliable means and system of facilitating prevention of the screws from migrating out of the bone by axial or rotational movement after the plate is fixed thereto. 
         [0011]    Among some of the problems associated with the prior art devices is that after the device is inserted into a patient during a surgical procedure, there was a possibility of inadequate fixation of the implant device due to false-locking of fixating screws. 
         [0012]    Another problem with the prior art devices is that the implant device and associated bone graft could loosen after the surgical procedure due to undesired back-out of fixating screws. 
         [0013]    Moreover, in some of the prior art devices, the fixation screws are locked to the prosthetic device in a multiple-step process, increasing the possibility for user error or false fixation. 
         [0014]    Another problem with prior art implant plate systems is that the screws or fasteners which secured the plate had a tendency to withdraw, causing injury to local structures by the screws themselves. 
         [0015]    What is needed, therefore, is a system and method, which facilitates overcoming one or more of the aforementioned problems as well as other problems and to provide a device that has unique features that will facilitate reducing the risk associated with neurological surgeries and advance the present state of the art. 
         [0016]    Therefore, there is a need for a plate and fixation system in which bone screws or other fasteners are more securely retained and less likely to work loose or migrate, which reduces or eliminates the need for auxiliary components, screws, tools or additional fixtures. 
       SUMMARY OF THE INVENTION 
       [0017]    It is, therefore, one object of the embodiments to provide a plate having an improved locking system which in one illustrative embodiment comprises a screw having a member, such as a resilient pawl, that is received in a channel in the plate to facilitate preventing screw migration. 
         [0018]    In one aspect this invention comprises a plate system comprising a screw having a screw head, a plate having an aperture for receiving the screw, and the screw comprising at least one pawl for restricting or preventing the screw from moving in at least one of an axial direction or a rotational direction. 
         [0019]    In another aspect this invention comprises a locking screw for use in a plate, comprising a threaded portion, a screw head, and the screw head comprising at least one member for cooperating with the plate to prevent migration or movement of the screw head. 
         [0020]    These and other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a perspective view illustrating one embodiment of the invention where at least one or a plurality of pawls are embodied in the screw; 
           [0022]      FIGS. 2-5  are various fragmentary views illustrating various details of the embodiment shown in  FIG. 1 ; 
           [0023]      FIG. 6  is a perspective and fragmentary view of another embodiment of the invention showing various notched-out areas in the plate; 
           [0024]      FIGS. 7-10  are various fragmentary and sectional views showing various details of the embodiment shown in  FIG. 6 ; 
           [0025]      FIG. 11  is a fragmentary perspective view illustrating another embodiment of the invention with a continuous channel in a plate; 
           [0026]      FIGS. 12-15  are various fragmentary and sectional views illustrating various details of the embodiments shown in  FIGS. 11 ; 
           [0027]      FIGS. 16  is a perspective view showing the screw and plate according to the embodiment illustrated in  FIGS. 6-10 ; and 
           [0028]      FIG. 17  is a perspective view of the embodiment corresponding to the embodiments shown in  FIGS. 11-15 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0029]    Referring now to  FIGS. 1-17 , means and apparatus for preventing axial and/or rotational movement in the form of a resilient lock may be provided.  FIGS. 1-17  illustrate a system and method for providing an integral lock. In  FIG. 1 , a system  10  comprises a screw  12  comprises at least one or a plurality of resilient fingers, springs, pawls, elastic projections or members  14  and  16 . The fingers or members are resilient, elastic and deflectable as with prior embodiments. In the illustration being described, the fingers or members  14  and  16  are integrally formed in the screw  12 , but they could be non-integral or assembled from multiple parts. 
         [0030]    Notice in the embodiment illustrated in  FIGS. 1-5  that a plate  18  is provided having a plurality of apertures  20 ,  22 ,  24 ,  26 ,  28  and  30 . In this embodiment, the plate  18  comprises a plurality of notches, projections or stops  32  associated with each aperture. The members  14  and  16  are normally biased a predetermined distance away from the axis of the screw  12  so that when the screw  12  is received in an aperture, such as aperture  20 , the screw  12  becomes locked or retained in the plate  18 . 
         [0031]    Notice in  FIG. 3  that the pawls  14  and  16  comprise beveled, curved or angled surfaces  14   a  and  16   a  which engage the notches  32   a ,  32   b  and  32   c ,  32   d , respectively, and deflected inwardly (as viewed in  FIG. 2 ) toward an axis of the screw  12  as the screw  12  is screwed into bone. After the screw  12  is screwed into the bone to a desired depth, an end  14   b  ( FIG. 1 ) of finger  14  and an end  16   b  of finger  16  becomes received between adjacent notches  32 , such as in areas  34  and  36  ( FIG. 4 ), between adjacent notches  32 . Notice that a surface  32   a  ( FIG. 4 ) of at least one notch  32  engages end  14   b  of the resilient pawl  14 , which prevents rotational movement in a counterclockwise direction (as viewed in  FIG. 4 ). At this point, ends  14   b  and  16   b  of fingers or pawls  14  and  16 , respectively, are received in the areas  34  and  36  as illustrated in  FIG. 4 . 
         [0032]    Thus, in the embodiment being illustrated,  FIGS. 1-5 , the pawls  14  and  16  cooperate with the notches or projections  32  to prevent rotational movement of the screw  12  after it is received in the plate  18  and in the bone. 
         [0033]      FIGS. 6-10  and  16  illustrate another embodiment wherein both axial and rotational movement of the screw  12  is prevented or restricted. In this embodiment, a plate  40 , which is shown only in fragmentary view for ease of illustration and description, is provided with at least one or a plurality of screw-receiving apertures  42 , as best described in  FIG. 6 . In this regard, the plate  40  comprises a wall  44  defining the screw-receiving aperture  42 . The wall  44  also comprises a plurality of notched-out areas  48  associated with aperture  42 . Each of the plurality of notched-out areas  48  is defined by a wall  50  having side or wall surfaces  50   a  and inner surfaces  50   b  that cooperate to define the notched out area  48 . 
         [0034]    As illustrated in  FIGS. 8 and 10 , the pawls or fingers  14  and  16  may comprise beveled or angled camming surfaces  14   a  and  16   a , respectively, that resiliently deflect inwardly toward the axis of screw  12  after the screw  12  is received in the aperture defined by wall  52  and screwed into the bone. In the embodiment illustrated in  FIGS. 6-10 , the surfaces  14   a  and  16   a  engage the surface or edge  44  ( FIG. 6 ) of the plate  40  and yield inwardly (as viewed in  FIGS. 7-8 ) toward the axis of the screw  12 . After the surface  14   b  of pawl  14  and surface  16   b  of pawl  16  clear the surface  50   b   1  ( FIG. 8 ), the ends  14   c  and  16   c  of resilient pawls  14  and  16  move outwardly or away from the axis of the screw  12  until at least a portion, such as ends  14   c  and  16   c , are received in one of the notched-out areas  48 , whereupon the surfaces  14   d  and  16   d  ( FIG. 6 ) become operatively related to and generally opposed to the surface  50   b   1 , as illustrated in  FIGS. 9-10 . 
         [0035]    Notice that when the pawls  14  and  16  are in the locked position, the screw  12  is prevented or restricted from moving, migrating or withdrawing axially (i.e., to the right as viewed in  FIG. 10 ). Notice also that the walls  50   a  of notched-out areas  48  cooperate with ends  14   c  and  16   c  to restrict or prevent rotational movement of the screw  12  in a counter-clockwise direction in the illustration being described. 
         [0036]      FIGS. 11-15  and  17  show a similar arrangement except that a plate  60  comprises a U-shaped wall or surface  62  that defines a single, continuous notched-out area, endless channel, or channel  64 . In this embodiment, at least a portion of the ends  14   c  and  16   c  are received in the channel or notched-out area  64 , as shown in  FIGS. 14-15 . As with the embodiment described relative to  FIGS. 6-10  and  16 , this embodiment also prevents axial movement of the screw  12 . 
         [0037]    After screw  12  is received in an aperture, such as aperture  66  ( FIG. 11 ) of plate  60 , as best seen in  FIG. 11 , the angled surfaces  14   a  and  16   a  engage or cam against the surface  68  ( FIG. 11 ) and are deflected inwardly, as illustrated in  FIGS. 12-13 . The screw  12  is driven until the surfaces  14   a  and  16   a  clear the wall or surface  70  ( FIG. 11 ), whereupon at least a portion of the fingers, such as ends  14   c  and  16   c , spring or move away from the screw axis end and are received in the channel  64 , whereupon the surfaces  14   d  ( FIGS. 12) and 16   d  become generally opposed to surface  70  ( FIG. 13 ). This prevents or restricts axial movement or withdrawal of the screw  12  from the bone and plate  60 . 
         [0038]      FIGS. 16 and 17  are perspective views of the entire plate and screws for the embodiments shown in  FIGS. 6-10  and  11 - 15 , respectively. Of course, the various pawls, fingers, notched-out areas, notches and the like described could be adapted to have other shapes or configurations, with more or fewer of them, for example, without departing from the desire to provide a locking system and method that provides means for restricting axial and rotational movement of a screw in a plate. 
         [0039]    Advantageously, various embodiments described relative to  FIGS. 1-17  provide various means, apparatus and methods for preventing axial and/or rotational movement of the screw and for providing an integral lock to facilitate retaining the screw in a bone, such as a spinal bone. The system and method according to these embodiments show various means for providing a lock for retaining the screw in the plate in which it is received. 
         [0040]    Advantageously, the system and method provide means and apparatus for locking a screw to a plate and preventing withdrawal of the screw or unscrewing of the screw. The illustrative embodiments provide means and apparatus for facilitating preventing rotational movement of at least one or a plurality of screws in at least one or a plurality of directions and axial movement of the at least one or a plurality of screws. 
         [0041]    While the apparatus and method described constitute preferred embodiments of this invention, it is to be understood that the invention is not limited to this precise apparatus and method, and that changes may be made in either without departing from the scope of the invention, which is defined in the appended claims.