Abstract:
A prosthesis comprising: a humeral stem; a humeral cup; and, a variable angle tray coupled to the humeral stem and the humeral cup, the variable angle tray comprising: a plate including an arcuate wall at least partially defines an internal cavity, a bearing adapted to occupy at least a portion of the internal cavity, the bearing being axially and rotationally repositionable with respect to the plate, the bearing operative to selectively expand in at least one dimension to wedge the bearing against the arcuate wall to inhibit axial and rotational repositioning of the bearing with respect to the plate, and a projection adapted to be coupled to the bearing, the projection also adapted to be coupled to the humeral stem in order to mount the variable angle tray to the humeral stem, where the arcuate wall is sized to retain a portion of the bearing within the internal cavity.

Description:
RELATED ART 
     Field of the Invention 
     The present disclosure relates to retention devices for surgical procedures and, more specifically, relates to variable angle prosthetic components including reverse shoulder prostheses. 
     INTRODUCTION TO THE INVENTION 
     It is a first aspect of the present disclosure to provide a partial reverse shoulder prosthesis comprising: (a) a humeral stem; and, (b) a variable angle tray adapted to be coupled to the humeral stem, the variable angle tray comprising: (1) a plate including a through hole at least partially defined by a wall that at least partially defines an internal cavity; and, (2) a variable angle stem occupying at least a portion of the internal cavity, the variable angle stem selectively axially repostionable with respect to the plate to change the axial position of the variable angle stem with respect to the plate, the variable angle stem comprising: (i) a first washer including threads at least partially defining a first opening and being insertable into the internal cavity; (ii) a post at least partially occupying the internal cavity, the post including a tapered crown and an appendage axially extending from the plate, where the appendage is sized to be received the humeral stem via a friction fit, and, (iii) a pin including a threaded head and a longitudinal shaft extending from the threaded head, the pin is insertable into the first opening, where the threaded head is sized to engage the threads of at least one of the first washer and the post, where the wall is sized to retain the first washer and at least a portion of the post within the through hole. 
     In a more detailed embodiment of the first aspect, the prosthesis further includes a driver including a first engagement device and a second engagement device, wherein the first engagement device is rotatably repositionable with respect to the second engagement device, wherein the first engagement device engages the pin, and wherein the second engagement device engages the first washer. In yet another more detailed embodiment, the plate includes a primary body and a removable cap coupled to the primary body, the removable cap comprising a portion of the wall and at least partially defining the internal cavity. In a further detailed embodiment, the first washer is discontinuous. In still a further detailed embodiment, the through hole of the plate includes at least two cutouts extending into the wall, the at least two cutouts being oriented horizontally across from one another. In a more detailed embodiment, the at least two cutouts are both oriented on the same side of a horizontal diametric chord of the through hole. In a more detailed embodiment, at least one of the first washer and the tapered crown includes a rounded circumferential surface adapted to contact the wall. In another more detailed embodiment, the rounded circumferential surface is at least one of smooth and textured. In yet another more detailed embodiment, at least one of the first washer and the tapered crown includes a sloped circumferential surface adapted to contact the wall. In still another more detailed embodiment, the sloped circumferential surface is at least one of smooth and textured. 
     In yet another more detailed embodiment of the first aspect, the first opening of the first washer is partially defined by at least two threaded wall segments, each of the threaded wall segments being circumferentially spaced from one another and interposed by a circumferential discontinuity. In still another more detailed embodiment, each circumferential discontinuity is defined by an axially inset wall of the first washer, wherein the discontinuity is adapted to receive a driver. In a further detailed embodiment, the prosthesis further includes a second washer defining a second opening and being insertable into the through hole, the second washer includes a widthwise dimension substantially greater than a thickness. In still a further detailed embodiment, the second washer is a spring washer. In a more detailed embodiment, the second washer comprises at least one of a helical washer, a Belleville washer, a wave spring washer, and a helical coil. In a more detailed embodiment, the removable cap includes a snap ring received within a cavity of the primary body. In another more detailed embodiment, the post includes a hollow adapted to receive at least a portion of the longitudinal shaft of the pin, the hollow including a catch operative to limit the depth of insertion of the longitudinal shaft. In yet another more detailed embodiment, the tapered crown and the appendage are separable from one another. In a further embodiment, the prosthesis further includes a humeral cup mounted to the variable angle tray. 
     It is a second aspect of the present invention to provide a partial reverse shoulder prosthesis comprising: (a) a humeral stem; (b) a humeral cup; and, (c) a variable angle tray adapted to be coupled to the humeral stem and the humeral cup, the variable angle tray comprising: (1) a plate including an arcuate wall at least partially defines an internal cavity, (2) a bearing adapted to occupy at least a portion of the internal cavity, the bearing being axially and rotationally repositionable with respect to the plate, the bearing operative to selectively expand in at least one dimension to wedge the bearing against the arcuate wall to inhibit axial and rotational repositioning of the bearing with respect to the plate, and (3) a projection adapted to be coupled to the bearing, the projection also adapted to be coupled to the humeral stem in order to mount the variable angle tray to the humeral stem, where the arcuate wall is sized to retain a portion of the bearing within the internal cavity. 
     In a more detailed embodiment of the second aspect, the plate includes a through opening that communicates with the internal cavity, and the internal cavity is partially spherical shaped. In yet another more detailed embodiment, the plate includes a removable cap that partially defines the internal cavity. In a further detailed embodiment, at least one of threads and a retention ring couples the removable cap to a remainder of the plate. In still a further detailed embodiment, the bearing comprises a plurality of washers and a threaded fastener. In a more detailed embodiment, the plurality of washers comprise a first washer and a second washer, the threaded fastener is sized to extend through and engage a threaded hole of the first washer, the threaded fastener is sized to engage the second washer, movement of the threaded fastener in a first direction with respect to the first washer causes the bearing to expand and wedge the bearing against the arcuate wall to inhibit axial and rotational repositioning of the bearing with respect to the plate, and movement of the threaded fastener in a second direction, generally opposite the first direction, with respect to the first washer causes the bearing to contract and allow axial and rotational repositioning of the bearing with respect to the plate. 
     In yet another more detailed embodiment of the second aspect, the plurality of washers include a spring washer that interposes the first washer and the second washer. In still another more detailed embodiment, the first washer includes a convex exterior surface adapted to contact the arcuate wall of the plate, the second washer includes a convex exterior surface adapted to contact the arcuate wall of the plate, and the projection is integrally formed with the second washer. 
     It is a third aspect of the present invention to provide a reverse shoulder prosthesis comprising: (a) a humeral component comprising: (1) a humeral stem; (2) a humeral cup; and, (3) a variable angle tray adapted to be coupled to the humeral stem and the humeral cup, the variable angle tray comprising: (i) a plate including an arcuate wall at least partially defines an internal cavity, (ii) a bearing adapted to occupy at least a portion of the internal cavity, the bearing being axially and rotationally repositionable with respect to the plate, the bearing operative to selectively expand in at least one dimension to wedge the bearing against the arcuate wall to inhibit axial and rotational repositioning of the bearing with respect to the plate, and (iii) a projection adapted to be coupled to the bearing, the projection also adapted to be coupled to the humeral stem in order to mount the variable angle tray to the humeral stem, where the arcuate wall is sized to retain a portion of the bearing within the internal cavity; and, (b) a scapula component comprising: (1) a scapula retainer; and, (2) a scapula ball adapted to be mounted to the scapula retainer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a frontal representation of bones, overlaid by skin, of a human shoulder region subsequent to a shoulder replacement where a reverse shoulder prosthesis has been implanted. 
         FIG. 2  is a cross-sectional view of a first exemplary partial shoulder joint implant. 
         FIG. 3  is a top view of the exemplary plate shown in  FIG. 2 . 
         FIG. 4  is a cross-sectional view taken along lines  3 - 3  of  FIG. 3 . 
         FIG. 5  is a profile view of the exemplary washer of  FIG. 2 . 
         FIG. 6  is an elevated perspective view of the exemplary washer of  FIG. 5 . 
         FIG. 7  is an elevated perspective view of the exemplary pin of  FIG. 2 . 
         FIG. 8  is an elevated perspective view of the exemplary post of  FIG. 2 . 
         FIG. 9  is an elevated perspective view of the exemplary spring washer of  FIG. 2 . 
         FIG. 10  is a profile view of an exemplary tool for use with the exemplary partial shoulder joint implant of  FIG. 2 . 
         FIG. 11  is an elevated perspective view of a distal end of the exemplary tool of  FIG. 10 . 
         FIG. 12  is a cross-sectional view of an alternate exemplary plate taken along line  13 - 13  of  FIG. 13 . 
         FIG. 13  is a top view of the alternate exemplary plate of  FIG. 12 . 
     
    
    
     DETAILED DESCRIPTION 
     The exemplary embodiments of the present disclosure are described and illustrated below to encompass retention devices for surgical procedures and methods of fabricating the retention devices and using the retention devices in a surgical procedure. Of course, it will be apparent to those of ordinary skill in the art that the preferred embodiments discussed below are exemplary in nature and may be reconfigured without departing from the scope and spirit of the present invention. However, for clarity and precision, the exemplary embodiments as discussed below may include optional steps, methods, and features that one of ordinary skill should recognize as not being a requisite to fall within the scope of the present invention. 
     Referencing  FIGS. 1 and 2 , a first exemplary partial shoulder joint implant  100  comprises a portion of a reversible ball and socket joint. The ball portion of the joint is adapted to be coupled to a scapula  102 , and includes a scapula retainer  104  and a scapula ball  108 . In contrast, the socket portion of the joint comprises a humeral shaft  110  seated within an intramedullary canal of a proximal humerus  112  having a humeral cup  114  mounted to a variable angle tray  116  that is coupled to the humeral shaft. 
     As shown in  FIGS. 3 and 4 , the variable angle tray  116  includes a plate  120  having an oblong vertical profile. Generally centered within the plate  120  is a through orifice  122  extending between top and bottom surfaces  124 ,  126 . The vertical cross-section of the through orifice  122  is not constant, but rather changes along an axis extending vertically through the orifice. More specifically, an inner circumferential wall  130  of the plate  120  partially defines a spherical cavity  132  where the diameter of the through orifice  122  is at a minimum at the top and bottom surfaces  124 ,  126 , but is at a maximum at the vertical midpoint of the through orifice. In this first exemplary plate  120 , the spherical cavity is partially defined by a removable cap  136  that includes threads  138  that engage corresponding threads  140  of a primary portion  142  of the plate. In this fashion, the cap  136  may be disengaged from the primary portion  142  in order to allow components to be seated within the spherical cavity  132  and thereafter reattached to the primary portion to inhibit certain components from egressing from the spherical cavity. The underside of the cap  136  includes an inner circumferential wall  144  that partially defines the spherical cavity  132 . The diameter of the inner circumferential wall  144  increases from the underside of the cap  136  to the top planar surface  146  of the cap having an opening  148  formed therein to accept the pin  160 . 
     Alternatively, the cap  136  need not threadably engage the primary portion  142  of the plate  120 . Instead, the threaded cap  136  may be secured to the primary portion  142  by using a snap ring or a taper (not shown) received within a corresponding cavity of the primary portion. 
     Referencing  FIGS. 2-6 , a washer  150  is adapted to be seated within the spherical cavity  132 . This washer  150  comprises a Belleville washer having a convex, rounded exterior surface  152  (that may be smooth or textured) that converges and meets a substantially planar exterior surface  154 . The rounded exterior surface  152  may include one or more depressions  155  that circumscribe an orifice  156  extending linearly through the rounded exterior surface  152  at its apex. As will be discussed in more detail hereafter, the one or more of the depressions  155  are adapted to receive projections from a driver  260  that may be used to retain the relative orientation of the washer. The through orifice  156  is substantially perpendicular to the planar exterior surface  154  and is delineated by a circumferential, circular wall having a series of threads  158  adapted to be engaged by a pin  160 . 
     While the washer  150  is shown in exemplary form as a continuous washer, it is also within the scope of the disclosure for the washer to include a radial cut  157  (shown in phantom) that renders the washer discontinuous. In this manner, the circumferential dimension of the washer  150  can more readily expand and contract depending upon the presence or absence of the pin  160 . Moreover, while the washer is shown in exemplary form as a Belleville washer, it should also be known that one may use a helical washer, a wave spring washer, or a helical coil in place of the spring washer. 
     Referring to  FIGS. 2-7 , the pin  160  comprises a cylindrical shaft  162  having a convex, semispherical distal end  164 . Opposite the distal end  164  is a proximal end  166  including a substantially planar surface  168  that circumscribes an opening extending into the interior of the proximal end to create a proximal cavity  170 . In exemplary form, this proximal cavity  170  is delineated by a series of vertical walls  172  having a hexagonal configuration. An outer circumference of the proximal end  164  includes a series of threads  174  sized to engage the threads of the  158  of the washer  150 . In this manner, the pin  160  may extend into the orifice  156  of the washer  150  and be vertically repositioned therein by rotating the pin with respect to the washer. In addition to engaging the washer  150 , the pin  160  is also adapted to engage a post  180 . 
     Referencing  FIG. 8 , the post  180  comprises an elongated stem  182  with a generally circular axial cross-section that tapers from proximal to distal. A proximal end  184  of the post  180  includes a generally planar top surface with a circular edge  186  defining the circumferential boundary of the adapter. Inset and centered with respect to the circular edge  186  is a depression  190  formed into the interior of the post  180 . In exemplary form, the depression is bounded by a semispherical wall  192  having a diameter that is large enough to accommodate a portion of the proximal end  164  of the pin  160 . More specifically, in this exemplary embodiment, the diameter of the semispherical wall  192  is one and a half times the diameter of the pin  160 . 
     Extending proximally from the circular edge  186 , a peripheral surface  196  of the post  180  embodies the curvature of a partial sphere and tapers from proximal to distal until reaching a conical surface  198  that circumscribes a frustoconical projection  200  having a substantially planar distal surface  202 . In exemplary form, the horizontal cross-section of the frustoconical projection  200  is circular, the diameter of which decreases from proximal to distal between the endpoint of the peripheral surface  196  and the circular perimeter of the planar distal surface  202 . In this manner, the frustoconical projection  200  is centered along a longitudinal axis  204  that vertically extends through the depression  190 . 
     Referencing  FIG. 9 , a spring washer  210  is adapted to interpose the first washer  150  and the post  180  when positioned within the spherical cavity  132 . The function of the spring washer  210  is to force the rounded exterior surface  152  of the first washer  150  and the peripheral surface  196  of the post  180  against the inner circumferential walls  130 ,  144  of the plate  120  and cap  136 . The force of the spring washer is chosen to allow axial and rotational repositioning of the assembly (post  180  and washers  150 ,  210 ), but provide sufficient resistance to rotational motion of the first washer  150  so that this washer substantially stays in a fixed position when the pin  160  is inserted into the orifice  156  and rotated so the threads  158 ,  174  engage one another and the pin vertically advances with respect to the first washer. 
     In this exemplary embodiment, a domed spring washer  210  is utilized. This spring washer  210  includes a convex top surface  214  and a concave bottom surface that are generally parallel to one another and are spaced apart by a thickness dimension. An orifice  216  is axially centered and extends through the spring washer  210 . In this exemplary embodiment, the orifice is generally circular. But it should be noted that other shaped orifices could be alternatively used. The outer periphery  218  of the spring washer  210  takes on a circular shape so that the washer has a constant radial distance between the outer periphery and the boundary defining the orifice  216  along the entire circumference, to provide a ring shape. In this exemplary embodiment, the spring washer  210  is fabricated from a metal that includes material properties providing partial elasticity that allows the washer to be compressed (from top and bottom) and spring back into shape when not compressed. 
     Referring to  FIGS. 10 and 11 , an exemplary tool  240  for use with the partial shoulder joint implant  100  includes an outer housing  242  defining a cylindrical bore occupied by an inner shaft  244  that is longitudinally and rotatably repositionable with respect to the outer housing. The distal end  246  of the outer housing  242  includes four projections  248  evenly spaced and oriented in a circular pattern. In this exemplary embodiment, each projection  248  includes an outer arcuate surface  250  spaced apart from an inner arcuate surface  252  by two planar side surfaces  254  and a bottom surface  256 . As will be discussed in more detail below, the projections  248  are adapted to be received within the recesses  155  of the washer  150  in order to inhibit rotation of the washer with respect to the inner shaft  244 . At a distal end of the inner shaft  244  is a hexagonal driver  260  having six vertical sidewalls and a substantially planar bottom surface  264 . Again, as will be discussed in more detail below, the driver  260  is adapted to be received within the proximal cavity  170  of the pin  160  in order to rotate of the pin with respect to the outer housing  242  and the washer  150 . 
     Referring to  FIGS. 1-9 , assembly of the partial shoulder joint implant  100  includes seating the humeral shaft  110  within the intramedullary canal of the proximal humerus  112 . To ensure the shaft  110  maintains its position with respect to the humerus  112 , the shaft  110  may incorporate bone ingrowth materials or features in addition to the use of adhesives or cements interposing the shaft and humerus. This shaft  110  may include a socket adapted to directly receive a portion of the elongated stem  182  of the post  180  via a friction fit, thereby inhibiting relative movement between the post  180  and shaft  110 . Conversely, the shaft  110  may include a socket adapted to directly receive a stem adapter  230 , which itself includes a cavity  232  for receiving a portion of the elongated stem  182  of the post  180 . Relative movement between the stem adapter  230  and the humeral shaft  110  is inhibited after the adapter and shaft are secured via a friction fit. Alternatively, or in addition, the stem adapter  230  may be mounted to the humeral shaft  110  using an adhesive or cement. For purposes of explanation, the assembly will be discussed to include a stem adapter  230 . 
     After the shaft  110  is mounted to the humerus  112  and the stem adapter  230  is mounted to the shaft  110 , the variable angle tray  116  may be mounted to the stem adapter. Prior to mounting the variable angle tray  116  to the stem adapter  230 , at least a portion of the tray must be assembled. Assembly of the tray  116  begins with the plate  120  without the humeral cup  114  or the removable cap  136  being mounted thereto and without any components being seated within the spherical cavity  132 . Thereafter, the post  180  is inserted into the orifice  122  so that a portion of the elongated stem extends beyond the bottom surface  126  of the plate  120 . Generally, the peripheral surface  196  of the post  180  will contact the inner circumferential wall  130 . Given that the diameter of the orifice  122  is greater than the diameter of the elongated stem  182 , but less than the diameter of the proximal end  184  of the post  180 , the post is able to be rotationally and axially repositioned with respect to the tray  120 . 
     After the post  180  is inserted into the tray  120 , the spring washer  210  is inserted into the spherical cavity  132  so that the orifice  216  is axially aligned with the depression  190  of the post  180 . Thereafter, the washer  150  is inserted into the spherical cavity  132  so its orifice  156  is axially aligned with the orifice  216  of the spring washer  210  and the depression  190  of the post  180 . At this point, after the washer  150 , spring washer  210  and post  180  have been inserted into the spherical cavity  132 , the cap  136  is mounted to the plate  120  via a threaded connection between the threads  138  of the cap and threads  140  of the plate. The cap  136  is rotated with respect to the plate  120  until the cap can no longer be rotated, thereby securing the cap to the plate via a friction fit. At this time, the washer  150 , spring washer  210  and the post  180  cannot be removed from the spherical cavity  132 . But the compilation of the washer  150 , spring washer  210  and the post  180  are rotationally and axially repositionable within the spherical cavity  132  at this point. 
     In order to lock the position of the washer  150 , spring washer  210  and the post  180  within the spherical cavity  132 , the pin  160  is inserted (distal end  164  first) through the opening  148  of the cap  136 , through the orifice  156  of the washer, and through the orifice  216  of the spring washer  210 . Eventually, the pin  160  is inserted deep enough that its threads  174  engage the threads  158  of the washer  150 . At this point, further penetration of the pin  160  requires the pin to be rotated with respect to the washer  150 . 
     The tool  240  is thereafter used to rotate the pin  160  with respect to the washer  150 , as well as axially reposition the washer  150 , spring washer  210  and the post  180  with respect to the plate  120 . Depending upon the desired angle a surgeon wants to set the tray  116  with respect to the humeral shaft  110 , the surgeon manipulates the tool  240  to the desired angle to lock the relative position of the washer  150 , spring washer  210  and the post  180  with respect to the plate  120 . In exemplary from, the driver  260  is inserted into the proximal cavity  170  of the pin  160  so that rotation of the driver will result in rotation of the pin in the same direction. Likewise, the projections  248  of the outer housing  242  are received within recesses  155  of the washer  150  so that if the outer housing  242  is stationary, so too is the washer. After the tool  240  has engaged the pin  160  and the washer  150 , the driver  260  is rotated so the threads  158 ,  174  engage one another to draw the pin deeper into the spherical cavity  132 . At a predetermined point, the distal end  164  of the pin  160  contacts the semicircular wall  192 . After this point, continued movement of the pin  160  operates to moves the washer  150  vertically away from the proximal end  184  of the post  180  to eventually form a wedge locking the washer and post in position. This wedge is exhibited when no further rotational motion of the pin  160  with respect to the post  180  is available. When the wedge is created, the axial position of the post  180 , and hence its elongated stem  182 , is locked in position with respect to the plate  120 . At this time, the tool  240  may be removed and the tray  116  mounted to the stem adapter  230 . In this manner, relative movement between the stem adapter  230  and the tray  116  is inhibited after the adapter and tray are secured via a friction fit. Alternatively, or in addition, the stem adapter  230  may be mounted to the tray  116  using an adhesive or cement. After the tray  116  is mounted to the stem adapter  230 , the humeral cup  114  may be mounted to the tray. 
     Referring to  FIGS. 12 and 13 , an alternate exemplary plate  320  may be used in place of the foregoing plate  120 . In contrast to the foregoing plate  120 , this alternate exemplary plate  320  does not include a removable cap  136 . As with the first exemplary plate  120 , this alternate exemplary plate  320  includes an oblong vertical profile. Generally centered within the plate  320  is a through orifice  322  extending between top and bottom surfaces  324 ,  326 . The vertical cross-section of the through orifice  322  is not constant, but rather changes along an axis extending vertically through the orifice. More specifically, an inner circumferential wall  330  of the plate  320  partially defines a spherical cavity  332  where the diameter of the through orifice  322  is at a minimum at the top and bottom surfaces  324 ,  326 , but is at a maximum at the vertical midpoint of the through orifice. But the spherical cavity  332  is not entirely spherical. A pair of cutouts  336  are formed vertically through the top surface  324  and radially into the plate  320  to accommodate insertion of washers. The cutouts  336 , in exemplary form, may be oriented on the same side of a diametric line and formed vertically to a midpoint of the plate  320 . The dimension of the cutouts  336  accommodate vertical insertion of the washers when the washers are turned so that the vertical dimension (i.e., thickness) of the washers is oriented horizontally so the washers can be inserted into the spherical cavity  332  and then axially repositioned so the vertical dimension is oriented vertically. In other words, the thickness of each of the washers is less than the width of the cutouts  336 . Because the cutouts  336  do not extend around the entire circumference of the cavity  332 , once the washers are inserted into the cavity and axially repositioned, the washers may not be removed from the cavity unless the washers are axially repositioned so that the horizontal position is vertically oriented. 
     Using the alternate exemplary plate  320  requires using a modified post  180 . In this manner, the elongated stem  182  is removable from the proximal end  184  via a threaded connection. More specifically, the elongated stem  182  includes a male threaded connection that is received with a female threaded connection of the proximal end  184 . As a result, only the proximal end  184  of the post  180  need to inserted in between the cutouts  336 . After the proximal end  184  of the post  180  is within the spherical cavity  332 , the elongated stem  182  is coupled to the proximal end by engagement of the threaded connections. Beyond these modifications, all other aspects are substantially the same as the first exemplary embodiment. 
     Following from the above description and invention summaries, it should be apparent to those of ordinary skill in the art that, while the methods and apparatuses herein described constitute exemplary embodiments of the present invention, the invention contained herein is not limited to this precise embodiment and that changes may be made to such embodiments without departing from the scope of the invention as defined by the claims. Additionally, it is to be understood that the invention is defined by the claims and it is not intended that any limitations or elements describing the exemplary embodiments set forth herein are to be incorporated into the interpretation of any claim element unless such limitation or element is explicitly stated. Likewise, it is to be understood that it is not necessary to meet any or all of the identified advantages or objects of the invention disclosed herein in order to fall within the scope of any claims, since the invention is defined by the claims and since inherent and/or unforeseen advantages of the present invention may exist even though they may not have been explicitly discussed herein.