Abstract:
A bone plate locking mechanism and methods for utilizing same are disclosed. A bone plate in accordance with the present invention includes a bone screw hole having a plurality of first lips and a plurality of second lips. The first lips are closer to the upper surface than the second lips and the first and second lips are offset around the bone screw hole.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of the filing date of U.S. Provisional Patent Application No. 62/055,184 filed Sep. 25, 2014, the disclosure of which is hereby incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention pertains to orthopedic bone plates, and in particular, orthopedic bone plates with screw locking features. 
         [0003]    A common method utilized in repairing fractures of bones includes affixing bone plates to the bone with screws. Generally, the plates are oriented so that portions thereof are placed on either side of the fracture and screws are placed through bone screw holes of each bone plate portion. Depending upon the particular anatomical area of the fracture, different plate designs exist. For instance, plates designed for use on the distal and proximal portions of long bones such as the femur or tibia may include a shaft and a head, each with screw holes extending therethrough. 
         [0004]    One commonly encountered issue with standard bone plate and screw constructs is the tendency for the screws to back out of plate holes after implantation. This not only has the ability to affect the strength of the bone plate construct, but also may cause pain or discomfort in the patient. Often times, additional surgery is required to address screw back out issues. Plate and screw designs have attempted to address this issue by including, inter alia, threaded plate holes that are engaged by the threaded head of a screw or even deformable/deflectable screw hole portions. The aim of such designs is to essentially affix the screw in the hole, thereby preventing back out. 
         [0005]    Another common issue with standard bone plate and screw constructs is the inability of the screws to be positioned in a manner in which proper bone purchase can be achieved. In other words, it is often necessary to place the screws along a particular trajectory in order to direct them into portions of the bone that are healthy and capable of holding a screw. This issue has been addressed by allowing for screws to be placed at different angles in bone screw holes (i.e., polyaxially). 
         [0006]    There exists a need for a bone plate which addresses each of the aforementioned issues, while also allowing for ease of use by a surgeon or other medical professional. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    A first aspect of the present invention is a bone plate including a body having upper and lower surfaces and a bone screw hole formed through the body and including a plurality of first lips and a plurality of second lips. The first lips are closer to the upper surface than the second lips and the first and second lips are offset around the bone screw hole. 
         [0008]    The bone plate of the first aspect may include a design in which the first and second lips do not overlap each other or partially overlap each other. The first and second lips may include ramped surfaces, and the bone screw hole may further include a countersink. The bone plate discussed above may be packaged or offered with a bone screw having a head and a shank. In certain embodiments, the bone screw may be of a harder material than bone plate, in particular, the head may be of a harder material than the first and second lips. Placement of the bone screw through the bone plate may result in a deformation or deflection of the first and second lips. 
         [0009]    A second aspect of the present invention is a bone plate system including a body, a bone screw hole formed through the body including a plurality of upper and lower lips and a bone screw having a head and a shank. The head may deform or deflect the upper and lower lips upon insertion of the screw through the bone screw hole. 
         [0010]    In other embodiments, the upper and lower lips may be offset from each other around the bone screw hole, for instance, offset thirty degrees from each other. In still further embodiments, the first and second lips do not overlap each other. The first and second lips may partially overlap each other or not overlap each other. The first and second lips may include ramped surfaces. The bone screw hole may further include a countersink. The bone screw may be of a harder material than bone plate, in particular, the head portion. 
         [0011]    Yet another aspect of the present invention is another bone plate system. The system according to this aspect includes a body, a bone screw hole formed through the body including a plurality of ramped upper and lower lips and a bone screw having a head and a shank. The head is of a harder material than the upper and lower lips and deforms or deflects the upper and lower lips upon insertion of the bone screw in the bone screw hole. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    A more complete appreciation of the subject matter of the present invention and of the various advantages thereof can be realized by reference to the following detailed description in which reference is made to the accompanying drawings in which: 
           [0013]      FIG. 1  is a top view of a bone plate according to an embodiment of the present invention. 
           [0014]      FIG. 2  is another top view of the bone plate of  FIG. 1  focusing on two holes thereof. 
           [0015]      FIG. 3  is a bottom view of the plate of  FIG. 1  with a similar focus on the two plate holes as in  FIG. 2 . 
           [0016]      FIG. 4  is a top view focusing on a single plate/bone screw hole from the plate of  FIG. 1 . 
           [0017]      FIG. 5A  is a cross-sectional view of the bone screw hole of  FIG. 4  along a line B-B. 
           [0018]      FIG. 5B  is another cross-section of the bone screw hole of  FIG. 4  along a line C-C. 
           [0019]      FIG. 6  is a top perspective view of the bone screw hole of  FIG. 4 . 
           [0020]      FIG. 7  is a top perspective view of a bone screw hole according to another embodiment of the present invention. 
           [0021]      FIG. 8  is a bottom perspective view of the bone screw hole of  FIG. 7 . 
           [0022]      FIG. 9  is a perspective view of a bone screw for use with the bone plate of  FIG. 1  and the bone screw hole of  FIG. 4 . 
           [0023]      FIG. 10  is a cut away view depicting the bone screw of  FIG. 9  placed within a bone screw hole of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    With reference to  FIG. 1 , the present invention is directed to a bone plate  10  that includes a plurality of bone screw holes  12 . As shown in  FIG. 1 , bone plate  10  also includes a series of other holes  14 , which may be designed to receive different types of bone screws, k-wires, or the like, or in the case of the plate of  FIG. 1 , allows for the plate to be fit into a test fixture. Although shown as a straight plate with a rectangular shape, plate  10  may be designed to cooperate with different anatomical features of the body. For instance, plate  10  may be designed for placement on the distal radius, and therefore may include a head portion and a shaft portion (not shown). In any event, as will be readily apparent from the remaining description, the focus of the present invention is on bone screw holes  12 , which are to be included in any such plate design. It is to be understood that the plates may include any number of bone screw holes  12 , according to their specific intended use. 
         [0025]    As is shown in  FIGS. 2 through 6  in additional detail, hole  12  includes a countersink  20 , a plurality of upper lips  22  and a plurality of lower lips  24 . Countersink  20  is designed, as is shown in  FIG. 10 , to cooperate with a portion  54  of the head  52  of a bone screw  50 , to both facilitate and limit polyaxial movement of the screw with respect to the plate. In particular, both countersink  20  and portion  54  are curved so as to allow for articulation of the two components with respect to one another through a range of angles, e.g., up to fifteen degrees in all directions around hole  12 . Of course, the range of allowable polyaxial rotation can vary, including greater and less than the fifteen degrees allowed by the embodiment shown in  FIG. 10 . In addition, hole  12  is sized such that shank  58  of screw  50  is able to move a certain distance along with the articulation of head  52  (e.g., 15 degrees of rotation). 
         [0026]    Upper lips  22  and lower lips  24  are situated circumferentially around hole  12  in an offset manner from one another so that they are not stacked vertically, but rather extend between one another in the axial direction. This is best shown in  FIGS. 2 through 8 . The lips are also spaced axially from one another so that there is a space therebetween, which is best shown in  FIGS. 5A and 5B . As will be discussed more fully below, threaded portion  56  of head  52  of screw  50  is ultimately disposed within this space. In a preferred embodiment, upper lips  22  are arranged at 0°, 60°, 120°, 180°, 240° and 300°, while lower lips  24  are located at 30°, 90°, 150°, 210°, 270° and 360°. However, it is to be understood that the lips can be arranged at any orientation with respect to each other or hole  12 . For instance,  FIGS. 7 and 8  depict an embodiment hole  12  that includes four of each of upper lips  22  (situated at 0°, 90°, 180° and 270°) and lower lips  24  (situated at 45°, 135°, 225° and 315°). 
         [0027]    As is shown in  FIG. 10 , placement of screw  50  through hole  12  results in a threaded portion  56  being captured between lips  22  and  24 . This acts to prevent back out of the screw from the plate. Screw  50  may also be placed in hole  12  at a variety of angles, while still achieving the desired function. In fact, the configuration of lips  22  and  24 , as well as the remainder of hole  12  allows for screw  50  to be held in place in a plurality of different angular orientations. The angled nature of lips  22  and  24  (best shown in  FIGS. 5A-8 ) not only aids in such placement, but also makes the placement of threaded portion  56  easier to accomplish. As shown, the lips are effectively ramp-shaped (i.e., tapering towards a center of the hole) so as to make passing screw  50  through hole  12  easier. It is noted that the size of shank  58  of screw  50  must be sized to allow for the polyaxial movement of the screw within hole  12 . 
         [0028]    In certain embodiments, plate  10  and screw  50  can be constructed of the same material. Upper and lower lips  22 ,  24  act as somewhat weakened sections, and either deform or deflect upon placement of screw  50  in hole  12 . The fact that threaded section  56  may include threads that are significantly stronger than the thinner lips  22 ,  24  may facilitate this deformation or deflection. In addition, it is contemplated that the plate may be constructed of a softer material than the screw, thereby further facilitating the deformation and/or deflection of the lips upon placement of the screw. The particular embodiment shown depicts a conically threaded head portion  56  of screw  50  which allows for 15° of rotation of the screw with respect to the plate. Of course, other screw hole/screw shapes/designs can be employed. 
         [0029]    Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.