Abstract:
A modular pedicle screw comprising a tulip or receiver having a body comprising a through bore for receiving a screw having a screw head, the tulip or receiver also comprising a rod receiving channel for receiving a rod, the body comprising a seat for receiving and supporting at least a portion of the screw head, a wall having at least one resilient or elastic arm, the at least one resilient or elastic arm having at least a portion that is operatively positioned in relation to the screw head to retain the screw head in the tulip or receiver.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to provisional U.S. Application Ser. No. 61/982,043 filed Apr. 21, 2014, to which Applicant claims the benefit of the earlier filing date. This provisional application 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 modular multi-axial or polyaxial screw system. 
         [0004]    2. Description of the Related Art 
         [0005]    Multi-axial screw systems are a mainstay of spinal orthopedic procedures. Exemplary inventions such as those disclosed in U.S. Pat. Nos. 4,641,636; 4,653,481; 4,805,602; 4,946,458; 4,987,892; 5,005,562; 5,176,780; 5,261,909; 5,360,431; 5,443,467; 7,604,655; 7,662,172; 7,686,835; 7,717,943; 8,012,185; 8,016,866; 8,066,745; 8,092,504; 8,097,025; 8,142,481; 8,147,522; 8,382,806 and U.S. Publication Nos. 2007/0123867 and 2013/0150893, which comprise various rod-based fixation systems, in which a screw is coupled to a fixation rod. Such coupling is multiaxial in nature, in order to respect variable anatomical relationships between the implanted rod and screw position. In the prior art, designs typically comprise at a minimum, a tulip-shaped rod-locking component, a ball-end threaded screw shaft component, a rod component and a locking cap component. 
         [0006]    With few exceptions, the extant systems are permanent assemblies permanently incorporating all the components. In fewer systems, exemplified by the Synthes Click-X system offered by Synthes Spine of West Chester, Pa., the tulip is mounted onto the ball as a separate intra-operative step. Such systems incorporate a captive split-ring mechanism at the base of the tulip to irreversibly capture the screw ball. Such mechanisms, requiring multiple components, are expensive to manufacture and prone to failure. 
         [0007]    What is needed, therefore, is a modular screw system that overcomes one or more of the problems in the prior art and that also allows for modular assembly of the tulip and screw components at the time of surgery, prior to implantation. Such a system would ideally be simple and reliable, without additional components which would defeat any cost saving benefit. 
       SUMMARY OF THE INVENTION 
       [0008]    Providing an unassembled modular pedicle screw system to the surgeon has several important benefits. Prior art systems have large selections of screw shaft types and sizes, each one with a permanently mounted tulip component. A modular system, however, can offer relatively few tulip components which can be assembled to the desired screw components at the time of surgery. This significantly reduces inventory costs, as the tulip components are typically the most expensive component of the system. Additionally, it is possible to offer a wider array of screw sizes and styles, without having to increase the number of tulip components in an individual surgical kit. 
         [0009]    It is, therefore, an object of an embodiment of the invention to provide an improved modular multi-axial screw system. 
         [0010]    Another object of an embodiment of the invention is to provide a screw system that can be assembled at the time of surgery by a surgeon. 
         [0011]    Still another object of the invention is to provide a tulip or receiver component that is adapted and capable of being used with a plurality of screws having different shaft types and sizes. 
         [0012]    Still another object of the invention is to provide a screw system having a tulip or receiver that allows for modular assembly of the tulip and receiver and the screw component at the time of surgery. 
         [0013]    In one aspect, one embodiment of the invention comprises a modular pedicle screw comprising a tulip or receiver having a body comprising a through bore for receiving a screw having a screw head, the tulip or receiver also comprising a rod receiving channel for receiving a rod, the body comprising a seat for receiving and supporting at least a portion of the screw head, a wall having at least one resilient or elastic arm, the at least one resilient or elastic arm having at least a portion that is operatively positioned in relation to the screw head to retain the screw head in the tulip or receiver. 
         [0014]    In another aspect, another embodiment of the invention a tulip or receiver comprising a body comprising a through bore for receiving a screw having a screw head, a rod receiving channel for receiving a rod, a seat for receiving and supporting at least a portion of the screw head, a wall having at least one resilient or elastic arm, the at least one resilient or elastic arm having at least a portion that is operatively positioned in relation to the screw head to retain the screw head in the tulip or receiver. 
         [0015]    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 ACCOMPANYING DRAWINGS 
         [0016]      FIG. 1  is a perspective view of one embodiment showing a modular receiver and tulip, screw, rod and securing cap; 
           [0017]      FIG. 2  is a view of the embodiment shown in  FIG. 1  showing at least one generally elastic or resilient arm integrally or monolithically formed in a side wall of the tulip or receiver; 
           [0018]      FIG. 3  is a perspective view showing various details of the tulip or receiver; 
           [0019]      FIG. 4  is another perspective view showing further details of the tulip or receiver including the seat for supporting a screw head of the screw; 
           [0020]      FIG. 5  is a sectional view showing detail of at least one or a plurality of the elastic or resilient arms; 
           [0021]      FIG. 6  is a fragmentary view illustrating the operative relationship of a detent end of the at least one or a plurality of elastic or resilient arms in association with a surface of a screw head; 
           [0022]      FIG. 7  is a fragmentary view of the screw in accordance with one embodiment of the invention; 
           [0023]      FIG. 8  is a sectional view similar to the view shown in  FIG. 5  illustrating a rod situated in the tulip or receiver; 
           [0024]      FIG. 9  is another sectional view similar to  FIG. 8  illustrating various details of the tulip or receiver after it has received a cap; 
           [0025]      FIG. 10  is a sectional view illustrating the relationship of the screw relative to a bore of the tulip or receiver when the screw is inserted therethrough; 
           [0026]      FIG. 11  illustrates the screw being inserted into the tulip or receiver; 
           [0027]      FIGS. 12A-12C  illustrate the screw as it is inserted into the tulip or receiver and the response of the at least one or a plurality of elastic or resilient arms being deflected in response to the movement of the screw head into the tulip or receiver; 
           [0028]      FIG. 13  is a view similar to  FIG. 12C  showing further details; 
           [0029]      FIG. 14  illustrates an embodiment wherein the tulip or receiver comprises a plurality of arms in at least one or a plurality of the generally opposing walls of the tulip or receiver, with the plurality of arms each having a longitudinal axis that is generally parallel to an axis of the tulip or receiver; and 
           [0030]      FIGS. 15 and 16  illustrate at least one or a plurality of elastic or resilient arms integrally formed in the tulip or receiver and having an axis that is generally transverse or non-parallel with respect to an axis of the tulip or receiver. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]    A multi-axial or polyaxial screw system or modular screw assembly  10  is shown. The multi-axial or polyaxial screw or modular screw assembly  10  comprises a multi-axial or polyaxial screw  12  having a shank  12   a  and a screw head or ball  14  ( FIG. 5 ). The multi-axial or polyaxial screw or modular screw assembly  10  further comprises a tulip or receiver  16  having a pair of generally opposing and generally U-shaped walls  17  that define a plurality of generally U-shaped channels  18  ( FIG. 3 ), respectively, that cooperate to define a rod-receiving area  20  for receiving a rod  32 . 
         [0032]    The tulip or receiver  16  further comprises a plurality of threads  22  that define female threads for receiving a threaded cap  24  ( FIGS. 1 and 2 ). Although not shown, the lock or means for securing the rod  32  in the tulip or receiver  16  could be the capless locking system as shown and described in U.S. Pat. Nos. 7,604,655; 7,662,172; 7,686,835; 7,717,943; 8,012,185; 8,016,866; 8,066,745; 8,092,504; 8,097,025; 8,142,481; 8,147,522; 8,382,806; and U.S. Publication Nos. 2007/0123867 and 2013/0150893. These patents and applications are incorporated herein by reference and made a part hereof. 
         [0033]    The rod-receiving area  20  ( FIG. 5 ) is adapted to receive the rod  32  ( FIGS. 1 and 8 ) as shown. The tulip or receiver  16  receives the threaded cap  24  which, when screwed, forces the rod  32  against the screw head or ball  14  of the multi-axial or polyaxial screw  12  which in turn forces a lower spherical portion  14   a  ( FIG. 5 ) of the screw head or ball  14  into engagement with and against a tulip seat  16   a  ( FIGS. 4 and 10 ) of the tulip or receiver  16  as best illustrated in  FIGS. 1 ,  2 ,  4  and  8 - 10 . 
         [0034]    In the embodiment being described, the tulip or receiver  16  of the multi-axial or polyaxial screw  12  is modified with at least one or a plurality of integral, monolithically formed resilient or elastic members or arms  30  which allow for the simple and reversible assembly and retention of the screw head or ball  14  into the tulip seat  16   a  of the tulip or receiver  16 . In the illustration, the tulip or receiver  16  is machined to have cut-out areas  31  ( FIGS. 3 and 4 ) that define the at least one or plurality of resilient members or arms  30 . In a preferred embodiment, each of the at least one or a plurality of integral, monolithically formed resilient or elastic members or arms  30  may be linear or generally linear and may be generally L-shaped in cross-section as illustrated in  FIG. 9 . As mentioned later herein, however, the resilient or elastic members or arms  30  may have other shapes such as an arcuate or curved shape and could have other orientations relative to the axis of the tulip or receiver  16 . 
         [0035]    As mentioned, each of the at least one or plurality of arms  30  may be generally linear or may have a curved or arcuate shape is desired. Each of the at least one or plurality of arms  30  have a distal end  30   a  and a proximally attached or integral end  30   b  that is proximate to a rod-receiving end  19  ( FIG. 5 ) of the tulip or receiver  16 . An intermediate elongated portion  30   c  joins the integral end  30   b  and distal end  30   a . Although the at least one or plurality of arms  30  are shown to be integral or monolithically formed in the tulip or receiver  16 , they could be non-integral and/or non-monolithic separate components adhered or affixed to the tulip or receiver  16 , for example, by a fastener such as a screw. 
         [0036]    Each of the at least one or plurality of arms  30  is located in a side wall  16   b  ( FIGS. 1-4 ) of the tulip or receiver  16  and is dimensioned to avoid interference with the locking aspects of the rod  32 , threaded cap  24 , or screw head or ball  14  rotation. The distal end  30   a  comprises a projection portion or detent  30   d  ( FIG. 8 ) that may optionally have a beveled edge  30   d   1 . 
         [0037]    As best illustrated in  FIGS. 10-14 , the multi-axial or polyaxial screw  12  is inserted axially into a bore  21  of the tulip or receiver  16  and driven downward (as viewed in  FIG. 10 ) into the tulip or receiver  16 , as illustrated in  FIGS. 10-12C , until the screw head or ball  14  engages the detents  30   d  and/or beveled surface  30   d   2  and deflects the at least one or plurality of arms  30  outwardly as indicated by the arrows A and B in  FIGS. 12A and 12B . As illustrated in  FIGS. 12C and 13 , once the major radius of the screw head or ball  14  has cleared the detents  30   d , the at least one or a plurality of integral, monolithically formed resilient or elastic members or arms  30  return to their home position, as shown in  FIGS. 8 ,  9 ,  12 C and  13 . Note that the corner edges  30   d   1  of detents  30   d  or a portion of detent  30   d  may engage the screw head or ball  14  to retain the screw head or ball  14  against the seat  14   a  as illustrated in  FIG. 13  and to further prevent the screw head or ball  14  and multi-axial or polyaxial screw  12  from unscrewing, withdrawing or moving in a direction of arrow C in  FIG. 13 . 
         [0038]    It should be understood that in this position and until the rod  32  and cap  24  are secured in the tulip or receiver  16  the user, such as a surgeon, is free to move or adjust a position of the tulip or receiver  16  on the screw head or ball  14 . Note that this can occur both prior to insertion and implantation of the multi-axial or polyaxial screw or modular screw assembly  10  in a patient, but it could also occur in situ. 
         [0039]      FIGS. 14-16  show additional illustrative embodiments. Like parts are identified with the same part numbers, except a “′” mark has been added. As best illustrated in  FIG. 14 , note that each of the at least one or plurality of arms  30 ′ is generally linear and extends in a direction that is generally parallel to an axis X ( FIG. 14 ) of the tulip or receiver  16 ′. It should also be understood that more or fewer at least one or plurality of arms  30 ′ could be provided as well. In this regard,  FIG. 14  shows another embodiment of the invention where the tulip or receiver  16 ′ comprises a plurality of arms  30 ′ in each side wall  16   b ′. In the illustration, the side walls  16   b ′ each comprise the pair of the plurality of arms  30 ′. 
         [0040]      FIGS. 1-14  illustrate the at least one or a plurality of arms  30  having an axis that is generally parallel to the axis of the tulip or receiver  16 , but they could take any orientation. For example,  FIGS. 15 and 16  show the at least one or a plurality of arms  30 ′ having a generally curved or arcuate shape and having an axis oriented generally transverse to the axis X as shown. It should be understood, however, that they could take the form of different shapes and be curved, arcuate or non-linear if desired. Moreover, the at least one or a plurality of arms  30 ′ can take different orientations and have non-linear shapes. For example,  FIGS. 15 and 16  illustrate a radial at least one or a plurality of arms  30 ′ and associated detent end  30   d ′ having an axis that lies in a generally radial plane and that is generally perpendicular or transverse to the axis X of the tulip or receiver  16 ′. Note that the radial at least one or a plurality of arms  30 ′ in this embodiment has an integral end that generally lies in the same radial plane as the detent end  30   d′.    
         [0041]    Using the embodiments of this invention, a surgeon can assemble the multi-axial or polyaxial screw  12  downward through the tulip or receiver  16 , displacing the at least one arm  30 , detent  30   d  and distal end  30   a  outward, until the screw head or ball  14  radius passes the detent  30   d . The detent  30   d  then returns to its home position and retaining the screw head or ball  14  in the tulip or receiver  16 . At this point, the surgeon can implant the multi-axial or polyaxial screw  12  and rod  32  as normal. 
         [0042]    Advantageously, the embodiments can also be used with different screws, such as screws having different diameters. The at least one resilient or elastic arm  30  could also comprise an end that is not integral with the tulip or receiver  16 . 
         [0043]    The invention provides the following advantages: 
         [0044]    provides an improved modular multi-axial screw system; 
         [0045]    provides a screw system that can be assembled at the time of surgery by a surgeon; 
         [0046]    provides a tulip or receiver component that is adapted and capable of being used with a plurality of screws having different shaft types and sizes; 
         [0047]    provides a screw system having a tulip or receiver that allows for modular assembly of the tulip and receiver and the screw component at the time of surgery. 
         [0048]    While the system, apparatus and method herein described constitute preferred embodiments of this invention, it is to be understood that the invention is not limited to this precise system, apparatus and method, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.