Abstract:
A bone plate, having a bone screw and a rotatable lock for retaining the bone screw in place, includes a retainer element and/or a stop element. The retainer element inhibits the lock from being pushed off of the bone plate, while the stop element limits the rotational range of motion of the lock.

Description:
[0001]    This application is a Continuation of, and claims priority under 35 U.S.C. §120 to, U.S. patent application Ser. No. 14/086,118, filed 21 Nov. 2013, which was a Continuation of U.S. patent application Ser. No. 12/567,978, filed 28 Sep. 2009, which claimed priority under 35 U.S.C. §119 to U.S. provisional patent application No. 61/101,737, filed 1 Oct. 2008, the entireties of which are incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    1. Field of Endeavor 
         [0003]    The present invention relates to devices, systems, and processes useful as bone plates, and more specifically to improvements in such plates fitted with screw locks. 
         [0004]    2. Brief Description of the Related Art 
         [0005]    U.S. Pat. No. D592,946 relates to a design of a rotatable lock for the bone screws used to hold bone plates to a bone, such as anterior cervical plates used in spinal surgeries. U.S. Patent Application Publication No. 2008/0091206, “Bone Plate”, describes similar bone plates including rotatable screw locks. The entirety of each of these documents is incorporated by reference herein. 
         [0006]    While the bone plates described in these patent documents perform well, in some circumstances the bone screws can back out of the bone to such an extent that the bone screw lock, which had been rotated over the head of the bone screw, is flexed upwards. Such flexing can cause damage to the bone screw lock, risking fracture of the lock. In addition, one difficulty that can arise with the use of such rotatable bone screw locks is that the practitioner does not have a way of knowing when the lock has been rotated the correct amount to adequately block the underlying bone screw from backing out, other than mere visual inspection. 
         [0007]    There remains a need for improvements in bone screw locks which can address these and other issues. 
       SUMMARY 
       [0008]    According to a first aspect of the invention, a bone plate comprises a plate formed of a biocompatible material and having an upper surface, at least one screw hole formed in the plate, and a stop element positioned on the plate upper surface, wherein, when a rotatable screw lock is rotatably mounted to the upper surface of the plate, at a position relative to the at least one screw hole so that, in a first unlocked position the screw lock does not impede passage of a bone screw through the at least one screw hole, and in a second locked position the screw lock does impede passage of a bone screw through the at least one screw hole, the stop element prevents the screw lock from complete rotation. 
         [0009]    According to another aspect of the present invention, a bone plate comprises a plate formed of a biocompatible material and having an upper surface, at least one screw hole formed in the plate, and a retainer element positioned adjacent to the screw hole and forming a gap between the retainer and the plate upper surface, and wherein, when a rotatable screw lock is rotatably mounted to the upper surface of the plate, at a position relative to the at least one screw hole so that, in a first unlocked position the screw lock does not impede passage of a bone screw through the at least one screw hole, and in a second locked position the screw lock does impede passage of a bone screw through the at least one screw hole, the screw lock passes under the retainer element when moving between the first and second positions. 
         [0010]    Still other aspects, features, and attendant advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of embodiments constructed in accordance therewith, taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The invention of the present application will now be described in more detail with reference to exemplary embodiments of the apparatus and method, given only by way of example, and with reference to the accompanying drawings, in which: 
           [0012]      FIG. 1  illustrates a top plan view of a first exemplary embodiment of a bone plate in accordance with the present invention; 
           [0013]      FIG. 2  illustrates an enlarged, top plan view of right side portions of the device illustrated in  FIG. 1 , taken at line F-F in  FIG. 3 ; 
           [0014]      FIG. 3  illustrates a cross-sectional view of the device of  FIG. 1 , taken at line A-A; 
           [0015]      FIG. 4  illustrates a cross-sectional view of the device of  FIG. 1 , taken at line C-C; 
           [0016]      FIG. 5  illustrates a cross-sectional view of the device of  FIG. 1 , taken at line D-D in  FIG. 2 ; 
           [0017]      FIG. 6  illustrates a cross-sectional view of the device of  FIG. 1 , taken at line B-B in  FIG. 3 ; 
           [0018]      FIG. 7  illustrates a cross-sectional view of the device of  FIG. 1 , taken at line E-E in  FIG. 2 ; 
           [0019]      FIG. 8  illustrates a top plan view of the embodiment of  FIG. 1 , showing screw locks; 
           [0020]      FIG. 9  illustrates a cross-sectional view of the device of  FIG. 1 , taken at line G-G in  FIG. 8 ; 
           [0021]      FIG. 10  illustrates a top, right, front perspective view of right side portions of  FIG. 11 , of the device of  FIG. 8 ; 
           [0022]      FIG. 11  illustrates a top, right, front perspective view of the device of  FIG. 8 ; 
           [0023]      FIG. 12  illustrates another top, right, front perspective view of the device of  FIG. 8 , with the screw locks oriented in their ‘unlocked’ positions&#39;; 
           [0024]      FIG. 13  illustrates the top, right, front perspective view of the device of  FIG. 8 , with the screw locks oriented in their ‘locked’ positions&#39;; 
           [0025]      FIG. 14  illustrates a top plan view of the device of  FIG. 8 , with the screw locks oriented in their ‘locked’ positions; and 
           [0026]      FIG. 15  illustrates a top, right, rear perspective view of right side portions of the device of  FIG. 8 , with the screw locks oriented in their ‘locked’ positions. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0027]    Referring to the drawing figures, like reference numerals designate identical or corresponding elements throughout the several figures. 
         [0028]    The aforementioned two patent document describe bone plates and locks for the screws of bone plates; as those of ordinary skill in the art are well familiar with bone plates, screws for bone plates, and locks for the screws of bone plates, the details of those devices will not be included herein. 
         [0029]    In general terms, in addition to the various features described in the two aforementioned patent documents, in accordance with principles of the present invention, a bone plate can be provided with a stop, a retainer, or both, for each one or more of the bone screw locks (also called a ‘bow-tie rivet’ herein). In essence, the stop is sized and positioned so that, when the bow-tie rivet is rotated in one direction, e.g., clockwise, the leading edge of the rivet hits the stop and prevents further rotational motion of the rivet. The lower surface of the retainer is spaced from the surface of the plate a distance sufficient to permit portions of the rivet to pass under the retainer as the rivet is rotated (e.g., clockwise); when the rivet&#39;s rotational motion ends, optionally because of the stop S, a portion of the rivet is still under the retainer R, which thus inhibits the rivet from popping off of the plate. Thus, by providing a stop to one side of the plate, when the practitioner turns the rivet, e.g., to 90 degrees, the rivet will hit against the stop and the practitioner thus knows to stop turning the rivet. Furthermore, the retainer can be provided so that when the rivet turns, it will stay under the retainer, so the rivet is inhibited or prevented from coming off of the plate. 
         [0030]    The positions of the retainer and the stop, relative to the rotatable lock and to the screw holes, can be tailored to the particular application. Furthermore, the locations of the retainer and the stop can be swapped, that is, can be moved to accommodate clockwise or counterclockwise rotation of the lock. Furthermore, while the lock is illustrated as being positioned so that its top surface is above the upper surface of the bone plate, the lock can alternatively be recessed in the plate; in this configuration, the stop can be formed as a shoulder in the plate itself, rather than as an element extending above the plate&#39;s surface, and the retainer can be suitably lowered. Further optionally, the rotatable lock itself can be made asymmetrical, so that one lateral side of the lock is shorter than the other, so that the shorter side would not be impeded by the stop, yet still restrained by the retainer. Yet further alternatively, the stop and retainer can be either co-located, or incorporated into a single element that both overhangs the screw hole, including a space for a portion of the lock to reside, yet also includes a portion that blocks further rotational motion of the lock. All of the devices and components described herein are formed of biocompatible, implantable materials typically used for bone plates. 
         [0031]    Turning now to the several drawing figures, exemplary bone plates embodying principles of the present invention are illustrated. In the top plan views of  FIGS. 1 and 2 , a bone plate  10  includes a generally flat body  12 , which can include curvatures depending on the particular use for which the plate will be employed. The plate  10  includes at least one, and advantageously numerous screw holes  14  which pass entirely through the body  12  from the top to the bottom surfaces, and are sized and otherwise configured to receive a bone screw in each of the holes. Further optionally, the plate  10  can include one or more (one being illustrated) additional holes  16 , for reducing the weight of the plate, among other purposes. One or more holes or bores  18  are formed in the body  12  to receive portions of a rotatable screw lock, described elsewhere herein and in the aforementioned U.S. patent documents; the holes  18  are positioned adjacent to at least one of the screw holes  14  so that when a screw lock is mounted in the hole  18 , the screw lock can lock the head of a screw positioned in the hole  14 . 
         [0032]    As discussed above, the plate  10  includes a stop  20 , a retainer  22 , or both, in proximity to one or more of the holes  14 . In the embodiment illustrated in  FIG. 1 , for each of the two pairs of bone screw holes on the left and right sides of the plate  10 , a stop  20  is positioned immediately adjacent to one screw hole and a retainer  22  is positioned adjacent to the other screw hole of the pair. As a single bone screw lock is used to secure the bone screws in each pair of bone screw holes in this embodiment, the stop  20  and the retainer  22  are provided for each rotatable bone screw lock. According to other exemplary embodiments, more than one retainer, stop, or both, can be provided for each bone screw lock, regardless of the number of bone screws the particular lock secures to the plate  10 . 
         [0033]      FIGS. 3 and 4  illustrate a cross-sectional view, taken at lines A-A and C-C in  FIG. 1 , respectively, and show that the stop  20  need not extend far from the body  12  in order to prevent a rotatable bone screw lock from moving. Additionally,  FIGS. 3 and 4  illustrate the overhanging feature of the retainer, which can inhibit or prevent a bone screw lock from popping off of the body  12 . 
         [0034]      FIG. 5  illustrates a cross-sectional view, taken at line D-D of  FIG. 2 , of an exemplary retainer  22 . The retainer  22  includes an upstanding portion  24  which is attached to the body  12  of the plate  10 , and a laterally extending portion  26  which is attached to the upstanding portion  24 . While the embodiment illustrated in  FIG. 5  includes portions  24 ,  26  being integral with each other and with the body  12 , other exemplary embodiments include these portions which are formed of one or more separate pieces which are joined together and joined to the body  12 . The laterally extending portion has a bottom surface  28  which at least in part faces the top surface of the body  12  and defines a gap  30  between the bottom surface of the laterally extending portion and the top of the body  12 . The gap  30  is sized and shaped to receive a portion of a bone screw lock therein and to thus inhibit or prevent the bone screw lock from moving vertically away from the body  12 . 
         [0035]      FIGS. 6 and 7  illustrate further cross-sectional views of the plate  10 . As illustrated in  FIG. 7 , the stop  20  advantageously includes a vertically extending wall  32  which provides a well-defined position at which a bone screw lock will stop when rotated against the stop  20 . 
         [0036]      FIG. 8  illustrates a top plan view of the bone plate  10 , with an exemplary rotatable bone screw lock  40  mounted to the body  12  at the hole  18 . According to preferred embodiments, the lock  40  is configured and positioned on the body  12  in the manner described in the aforementioned two U.S. patent documents. The lock  40  includes a narrow central portion  42  and at least one, preferably two, and alternatively more than two, flared end portions  44  which extend outward from the central portion  42 . As will be described in greater detail below, the configuration of the flared end portion(s)  44 , the stop  20 , and the retainer  22  are mutually dependent, and are constructed so that the lock  40  has at least two alternative rotary positions: a first position at which at least one of the adjacent bone screw holes  14  are unobstructed, so that a bone screw can be positioned in the bone screw hole; and a second position at which at least one of the flared end portions  42  overlies and obstructs the bone screw hole. In the second position, one of the flared end portions bears against the stop  20 , and/or one of the flared end portions is at least partially under the laterally extending portion of a retainer  22  and in the gap  30 . The lock  40  advantageously includes an opening  46  in the central portion  42  which can be configured to accept a torque driving tool (e.g., screwdriver, not illustrated) to assist the practitioner in rotating the lock  40  between its various rotary positions. 
         [0037]      FIG. 9 , which is a cross-sectional view taken at line G-G in  FIG. 8 , illustrates the top surface  50  the lock  40 , a portion of which will be trapped beneath the laterally extending portion  30  when in the aforementioned second position. While the top surface  50  is illustrated as being convex and slightly dome-shaped, the top surface can be other shapes as well. The lock  40  optionally includes a vertically extending post  48 , optionally formed of a deformable material, so that the lock can be rotatably secured to the plate body  12 . 
         [0038]      FIGS. 10-15  illustrate several perspective and plan views of the plate  10 , with locks  40  in both the first (open) and second (locking) positions, and illustrate exemplary positions of the flanges  44  of the locks relative to the stop  20  and the retainer  22 .  FIGS. 10 and 11  illustrate perspective views of the plate  10  having both a stop  20  and a retainer  22 , and a rotatable bone screw lock  40  rotated into an unlocked positioned, that is, the flanges  44  of the lock do not obstruct a bone screw hole  14 .  FIG. 12  illustrates a similar view, with two locks  40  in the same, unlocked orientation.  FIG. 13  illustrates the same view as  FIG. 12 , but with the locks  40  rotated clockwise (as seen from above) into locking positions, that is, with the flanges  44  at least partially covering a hole  14 . As can be seen in  FIGS. 13-15 , at least one of the flanges  44  is positioned under the laterally extending portion  26  of the retainer  22 , and in the gap  30 , when in the second position. Additionally, when provided with a stop  20 , one of the flanges  44  abuts against the stop, and more particularly against the wall  32  in this embodiment. The stop  20  is thus advantageously positioned so that, when a flange  44  meets the stop, another portion of the lock  40 , e.g., a flange of the lock, is under the laterally extending portion  26  and in the gap  30 . The stop  20  can be eliminated from the plate  10 , if desired. 
         [0039]    According to further embodiments, the stop  20  and the retainer  22  can be located immediately adjacent to each other or integrated into a single structure, and the combination can be positioned as the retainers illustrated herein. Further optionally, the bottom surface  28  can be angled so that a flange  44  can enter into the gap  30 , and upon further rotation of the lock  40  into the gap, the top surface  50  of the lock bears against the bottom surface  28  and locks the flange to the retainer  22 . Yet further optionally, the bottom surface  28  and top surface  50  can be formed with cooperating snap-fit structures, such as one or more ridges and grooves, so that when the flange  44  is rotated into the gap  30  and the top surface  50  and bottom surface  28  bear against each other, the ridge(s) and groove(s) can snap together, thus forming a releasable lock. 
         [0040]    While the invention has been described in detail with reference to exemplary embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention. The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. The entirety of each of the aforementioned documents is incorporated by reference herein.