Abstract:
An implant comprising a multi-directional locking mechanism that allows a bone fixation device, such as a screw, to be rigidly affixed to the implant in a plurality of angles relative to the implant. The implant can be a bone plate, a component of a joint prosthesis or the like. The locking mechanism comprises a passage hole in the implant for passage of a bone fixation device therethrough. One or more beam members are arranged adjacent the passage hole and a space is associated with each beam member. Each space allows the associated beam member to move into or about the space upon axial and/or radial deformation of the beam member caused by fastening the bone fixation device to a bone. The beam members and associated elements of the locking mechanism are sufficiently thin to permit axial and/or radial deformation. And said deformation causes the fixation device to be locked in place relative to the implant.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This is a non-provisional application claiming priority of provisional application Ser. No. 61/919,060 filed Dec. 20, 2013. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention is in the technical field of implanted medical devices. More particularly, the present invention relates to a multi-directional locking mechanism that can be incorporated in any kind of implant device that needs to be fastened to a bone, including fractured bones and bones that are not fractured. For example, the multi-directional locking mechanism can be incorporated into fixation systems for bones of all types which use plates and screws and other implants such as prostheses that are affixed to bones with screws. Such fixation systems are used in osteosynthesis (bone fusion), wherein bone screws are connected to a bone and a plate which bridges the fracture. It is desirable for optimal alignment onto the bone fragments, or for compensating target errors, to be able to incorporate the bone screws at different angles into the plate. 
         [0004]    2. The Related Art 
         [0005]    Implants of various types may be indicated for the entire skeleton. Implants include bone plates, intramedullary nails, suture anchors and prostheses of various types including joint prostheses and elements thereof such as acetabular cups for hip replacement prostheses. A “bone fixation device” may include any of a variety of devices that secure an object to a bone, including but not limited to bone screws, pins, blades and the like. 
         [0006]    The present invention seeks to remedy the problems of the prior art. The invention provides a multi-directional locking mechanism in the fastener hole (also referred to herein as a “hole” or “passage hole” or “through hole”) of an implant, without the need for additional components, that can accommodate conventional locking screws in a plurality of angles in a stable manner. The invention allows, for example, the overall thickness of a bone plate to be minimal providing for a low profile locking plate. Unlike the prior art, the invention is not required to rely on cross threading, gouging or stripping of the fastener hole threads and the bone screw threads. Also, the invention may create negative space around the periphery of the fastener hole to accommodate displaced material when the screw head engages features of the fastener hole to create a locked condition. This space may be created by a beam member (sometimes referred to herein as a “beam”) that is connected to the body of the implant. The space and beam configuration can be any geometry or combination of geometries as will be apparent to those having skill in the art based upon the disclosures herein. At least one space and one beam member should advantageously be present. The negative space may allow the beam member to translate both parallel and perpendicular to the axis of the passage hole. Because the beam member is thin, the movement of the beam member along its length may vary. All of these degrees of freedom may be beneficial to accommodate a wide variety of implants. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention comprises a multi-directional locking mechanism that allows a bone fixation device to be rigidly fixed to an implant in a plurality of relative angles. 
         [0008]    More specifically, the invention comprises, for use on an implant, one or more multi-directional locking mechanisms, each of which includes a passage hole, a perimeter, at least one beam member, and at least one space. The passage hole and corresponding perimeter can be any geometry, circular or otherwise. The beam member and space can have a plurality of geometries, orientations and configurations. The space(s) around the periphery of the hole accommodate displaced material of the beam member when the bone fixation device engages the beam member. In other words, the bone screw will contact the beam member causing movement of the beam member into or about the negative space. At least one space and one beam member is present in each multi-directional locking mechanism. The periphery of the passage hole has at least one beam member that is allowed to deform or adjust to the bone fixation device thereby locking the bone fixation device to the implant. The term “locking” as used herein can mean complete locking, i.e., axial and rotational locking, or just axial locking which allows rotational movement but no axial movement. When the beam member engages the bone fixation device, the beam or a portion of the beam may move into the negative space. This causes a radial compression force on the bone fixation device which may increase as the device is advanced further into the locking feature. The corresponding bone fixation device is appropriately sized to relatively interfere with the beam feature in a plurality of insertion angles. 
         [0009]    One advantage achieved by the invention is that, as a result of the beam members, a bone fixation device can be introduced at an angle that is different from or the same as the specified axis of the hole and rigidly fixed to the implant while maintaining rigidity. Furthermore the invention need not rely on cross threading, gouging, stripping, tapping, differential hardness, or third components, thereby reducing the potential for metal fragments and debris. The multi-directional locking mechanisms of the present invention benefit from material deformation in a predictable manner that allows radial and/or helical movement of the beam member. This is accomplished using a predefined space that accommodates the deformed or moved material. A plurality of bone fixation devices may be used for optimal fixation. The locking mechanisms and/or implants of the present invention can be made from a variety of conventional materials or from materials that previously were not conducive to current state of the art threading options, e.g. nitinol. 
         [0010]    By virtue of the beam and predefined space, and a relatively sized bone fixation device, a locking interface is produced between the implant and bone fixation device, even when the bone fixation device is inserted at an angle displaced from the axis of the hole. 
         [0011]    The geometry of the surface of the multi-directional locking mechanism may advantageously be constructed to facilitate compatibility with the bone fixation device to be introduced. The beam and/or other deformable features is adjacent to a predefined space, which is created to accommodate the movement of the beam. The space and thinness of the beam member allows the beam member to move in six degrees of freedom including radial and helical movement. The radial movement is uniquely advantageous over known locking mechanisms, which do not provide radial movement. The helical or complex deformation is also uniquely advantageous because it allows the deformed beam member to “match up” with the bone screw. The degrees of freedom and the predefined space thereby can adjust and/or move to accommodate the bone fixation device in a manner that provides relatively rigid fixation. The beam member is allowed to move or deflect in a manner that generally maintains the parallel nature of the opposing faces of the beam member. The multi-directional locking mechanism may be independent of the seating surface. Due to the plurality of possible combinations and movements, the bone fixation device “creates” its own proper seating position and geometry within the implant and locking mechanism. Said another way—the beams of the locking feature conform to the chosen trajectory of the bone fixation device. 
         [0012]    The beam and predefined space may have a shape to facilitate screw insertion. For example, a portion of the face or the entire face of the beam may be concave, spherical, tapered or contain a lead-in angle. This shape facilitates the insertion of a bone fixation device in such a manner that, in response to contact of the bone fixation device with the beam, the bone fixation device is automatically pulled into the hole in the implant without exerting a significant compression force to engage the two devices. This shape also allows the beam member to move in such a way that it creates a path for the mating feature on the bone fixation device. 
         [0013]    Any number of multi-directional locking mechanisms may be arranged radially symmetrically, non-radially symmetrically or radially but non-symmetric around the periphery of the passage hole. The passage hole may or may not be circular. The predefined space may be closed about its perimeter, or could have a small opening to the passage hole. 
         [0014]    In this specification the term “radial deformation” means the deformation of a beam member as it moves perpendicular to and away from the axis of the fastener hole. The terms “axial deformation” or “helical deformation” mean the deformation of a beam member as it moves in parallel with the axis of the fastener hole. Deformation may be more complex where a particular beam member may not deform uniformly. Both axial and helical deformation can and often do occur simultaneously according to the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a perspective view of a bone plate with multiple openings having beam members according to a first embodiment of the invention. 
           [0016]      FIG. 2  is a top plan view of the bone plate of  FIG. 1 . 
           [0017]      FIG. 3  is a detailed view illustrating the beam members according to the first embodiment of the invention. 
           [0018]      FIG. 4  is a perspective view, with an included cross-section view of a bone plate with multiple openings having beam members according to the first embodiment of the invention. 
           [0019]      FIG. 5  is a detailed view of the cross-section in  FIG. 4 . 
           [0020]      FIG. 6  is a front plan view of the cross section in  FIGS. 4 &amp; 5 . 
           [0021]      FIG. 7  is a bottom perspective view of a portion of  FIG. 4 . 
           [0022]      FIG. 8  is a perspective view of a bone plate with multiple openings having beam members according to a second embodiment of the invention. 
           [0023]      FIG. 9  is a top plan view of the bone plate of  FIG. 8 . 
           [0024]      FIG. 10  is a detailed view of the beam members according to  FIG. 8 . 
           [0025]      FIG. 11  is a perspective view of a typical orthopedic locking screw. 
           [0026]      FIG. 12  is a detailed plan view of the screw of  FIG. 11 . 
           [0027]      FIG. 13  is close-up plan view of the screw head of  FIG. 12 . 
           [0028]      FIG. 14  is a perspective view of the bone screw of  FIG. 12  inserted coaxially into a hole of the bone plate with multiple openings having beam members according to the first embodiment of the invention. 
           [0029]      FIG. 15  is a partial cross section view of  FIG. 14 . 
           [0030]      FIG. 16  is a plan view of the bone screw of  FIG. 14  inserted non-coaxially into a hole of the bone plate with multiple openings having beam members according to the first embodiment of the invention. 
           [0031]      FIG. 17  is a perspective view of  FIG. 16 . 
           [0032]      FIG. 18  is a detailed partial cross section view of  FIG. 17 . 
           [0033]      FIG. 19  is a perspective view of a third embodiment of a bone plate of the invention. 
           [0034]      FIG. 20  is a top plan view of  FIG. 19 . 
           [0035]      FIG. 21  is a detailed view illustrating the beam members according to the third embodiment of the invention shown in  FIGS. 19 and 20 . 
           [0036]      FIG. 22  is a perspective view of a bone plate with numerous examples of alternate embodiments of the multi-directional locking mechanism. 
           [0037]      FIG. 23  is a top plan of the bone plate and locking mechanisms shown in  FIG. 22 . 
           [0038]      FIG. 24  is a top view of a bone fixation device with a predefined space and multiple beam members according to a fourth embodiment of the invention. 
           [0039]      FIG. 25  is a perspective view of the embodiment shown in  FIG. 24 . 
           [0040]      FIG. 26  is a partial front view of the embodiment shown in  FIG. 24 . 
           [0041]      FIG. 27  is a perspective view of a bone fixation device with a predefined space and a beam member according to a fifth embodiment of the invention. 
           [0042]      FIG. 28  is a cross section view of the embodiment shown in  FIG. 27 . 
           [0043]      FIG. 29  is a perspective cross section view of the embodiment shown in  FIG. 27 . 
           [0044]      FIG. 30  is a detailed partial cross section view of the embodiment shown in  FIG. 27 . 
           [0045]      FIG. 31  is a perspective top view of a laminate bone plate incorporating a multi-directional locking mechanism of the current invention. 
           [0046]      FIG. 32  is a perspective bottom view of the laminate bone plate of  FIG. 31 . 
           [0047]      FIG. 33  is a top plan view of a bone plate showing an alternate embodiment of the present invention as an assembly. 
           [0048]      FIG. 34  is a perspective view of the embodiment shown in  FIG. 33 . 
           [0049]      FIG. 35  is a partial detailed view of the embodiment shown in  FIGS. 33 and 34 . 
           [0050]      FIGS. 36A and 36B  illustrate the deformation of the beam members caused by insertion of a screw perpendicular to a bone plate as in  FIGS. 14 and 15 . 
           [0051]      FIG. 36C  illustrates the deformation of the beam members caused by insertion of a screw not necessarily perpendicular to a bone plate. 
           [0052]      FIGS. 37A-37D  illustrate a “blind hole” embodiment of the locking mechanism. 
           [0053]      FIGS. 38A and 38B  illustrate a mesh embodiment comprising multiple locking mechanisms of the invention. 
           [0054]      FIGS. 39A-39C  illustrate a first embodiment of a locking mechanism having a non-orthogonal orientation. 
           [0055]      FIGS. 40A-40C  illustrate a second embodiment of a locking mechanism having a non-orthogonal orientation. 
           [0056]      FIGS. 41A and 41B  illustrate an embodiment of a locking mechanism in a curved bone plate. 
           [0057]      FIGS. 42A-42C  illustrate an embodiment of the locking mechanism having “stacked” beam members. 
           [0058]      FIG. 43  is a top perspective view of an acetabular cup comprising polyaxial locking plates of the invention. 
           [0059]      FIG. 44  is a top plan view of the acetabular cup of  FIG. 43  and  FIG. 44A  is a section view of  FIG. 44 . 
           [0060]      FIG. 45  is a side view of the acetabular cup of  FIG. 43 . 
           [0061]      FIG. 46  is a bottom perspective view of the acetabular cup of  FIG. 43 . 
           [0062]      FIGS. 47A-47C  illustrate an intramedullary nail comprising locking mechanisms of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0063]    The embodiments described herein may be used in connection with any type of implant, including but not limited to bone plates such as various trauma plates and reconstruction plates, in numerous applications such as foot and ankle, upper extremity, rib fractures, pelvic fractures, maxillo-facial, etc. The bone plates may be curved, contoured, straight, or flat and may be of a particular shape for a particular anatomy or a more general shape for multiple anatomies. The bone plates may be provided precontoured or manipulated and/or contoured during use for a specific application. 
         [0064]    The bone plate  100  shown in  FIG. 1  is a simple generic plate. The bone plate may have a head portion that is contoured to match a particular bone surface, such as a metaphysis or diaphysis, it may have projections from the shaft, be available in typical shapes (L-shape, T-shape, Y-shape, etc.) or may form any other appropriate shape to fit the bone/fracture to be treated. The cross-section of the bone plate  100  may be flat as shown in  FIG. 1  or contoured (such as a one-third tubular shape or similar). The bone plate  100  may be may be comprised of titanium, stainless steel, nitinol, cobalt chrome, carbon composite, plastic or polymer (e.g. PEEK, UHMWPe), resorbable materials (such as PLA, PGA) or some combination of these materials or any other appropriate material that has sufficient strength for the intended application, while also having sufficient biocompatibility for implantation in the body. It should be understood that bone plates comprised of any appropriate material are within the scope of this invention. 
         [0065]    A first embodiment of the invention is illustrated in  FIGS. 1 and 2  and the locking mechanism  300  thereof is illustrated by itself in  FIG. 3 . Bone plate  100  has at least one opening  130  that accepts the bone fixation device  390  (see  FIG. 11 ). Opening  130  has a central axis  135 . The multi-directional locking mechanism  300  illustrated in  FIG. 3  comprises the passage hole  130 , its central axis  135 , at least one beam member  150 , and at least one predefined space  140 . The opening  130  provides polyaxial fixation, and thus is adapted to receive a bone fixation device in a plurality of angles. The opening can also accommodate the bone fixation device straight in as well. Predefined space  140  may or may not pass through all or some of upper and lower surfaces, for example, upper and lower surfaces  110 ,  120 ,  180 ,  190 ,  1010  and  1020 . (See  FIGS. 1, 6 and 8 .) Stated another way, the predefined space  140  may be a pocket, enclosed space, blind hole, through hole, or a combination of the foregoing. For example,  FIGS. 37A-37D  illustrate and embodiment where the predefined space is a blind hole. The periphery  160  of passage hole  130  may have various shapes. The shape of the passage hole may be adapted to receive the head  400  of the bone fixation device  390 . The periphery of the passage hole  130  contains at least one beam member  150  and one predefined space  140 . The periphery  230  of the predefined space  140  may have any appropriately sized geometry. In other words, the geometry must be sized and configured to allow enough space for the beam member to move into when it is deformed by a fixation device. The beam member may move partially or completely into the predefined space  140 . Movement of the beam member  150  into the predefined space may be such that the beam member bottoms out, abuts, or significantly closes the predefined space  140 . The beam member may move partially or completely into the negative space. It may be desirable for the beam member to bottom out, abut, or significantly close the negative space. Bottoming out may provide a “stop” to the movement of the beam member thereby giving more rigidity to the assembled construct. Beam member  150  has a first beam connection  240  and a second beam connection  250  encircled by the ovals designated by the reference numerals  240  and  250 . The beam connections join the beam  150  to the remainder of the locking mechanism. Beam member  150  may have an optional lead-in feature  170  in the form of a thinned portion on the edge adjacent the passage hole. The lead-in feature can be on the top surface or the bottom surface or the top surface and bottom surface of the beam member, to facilitate engagement with the head  400  of the bone fixation device  390 . The figures show a passage hole and locking mechanism that are orthogonal to the plate top surface  110 . However, alternate embodiments could have the passage hole and/or locking mechanism not orthogonal to the bone plate as illustrated in  FIGS. 39A-39C and 40A-40C . 
         [0066]    The locking mechanism  300  shown in  FIG. 3  shows four beam members  150  and four predefined spaces  140 . Any combination and orientation of any number of beam members and predefined spaces are within the scope of this invention. 
         [0067]      FIGS. 5, 6 and 7  illustrate various views of a cross-section of the first embodiment of the invention. The locking mechanism  300  is positioned between an upper recess  210  and a lower recess  220 . The locking mechanism  300  may be equally spaced between the upper surface  110  and the lower surface  120 , or may be closer to the upper surface  110  or the lower surface  120 , as shown in  FIG. 6 . The locking mechanism  300  may also be biased completely towards the upper surface  110  or lower surface  120 . The upper recess  210  and the lower recess  220  are shown as cylindrical counterbores, but could also be countersinks, tapered, spherical, parabolic, or any other appropriate shape. Upper recess  210  and lower recess  220  are shown to have similar geometry but could have different geometries or combinations of geometries. 
         [0068]      FIG. 5  shows the beam members  150  and predefined spaces  140  in the same plane. The current invention may also include beam members and predefined spaces that are in different planes within the same locking mechanism. Stated differently, within a particular hole one beam member/predefined space combination may be on a different plane than another beam member/predefined space combination or the beam members in one hole may be on a different plane than another hole within the same implant. This may be advantageous to facilitate locking between the locking mechanism  300  and the bone fixation device  390 , for example, in cases where the shape of the implant may be more contoured, it may be necessary to have different beam members and predefined spaces on different planes to provide the necessary engagement between the implant and the fixation device. An example is in the acetabular cup illustrated in  FIGS. 41A, 41B and 43-46 . 
         [0069]      FIG. 6  shows a bone plate  110  constructed of one piece. However, the plate could be a laminate construction made of two or more layers as shown in  FIGS. 31 and 32 . Laminate construction may be advantageous in the manufacturing of the plate geometry with the locking mechanism. The features of the locking mechanism could be manufactured on one layer or multiple layers. 
         [0070]    A second embodiment of the invention is shown in  FIGS. 8 and 9 . Bone plate  1000  has at least one opening  1030  that accepts a bone fixation device  390  (see  FIG. 11 ). Opening  1030  has a central axis  1035 . The locking mechanism  1200  illustrated in  FIG. 10  includes a passage hole  1030 , which has a central axis  1035 , at least one beam member  1050 , and at least one predefined space  1040 . The locking feature  1200  is adapted to receive a bone fixation device in a plurality of angles. The periphery  1060  of passage hole  1030  may have various shapes. The shape of the passage hole may be adapted to the appropriately sized head  400  of the bone fixation device  390 . The periphery of the passage hole  1030  contains at least one beam member  1050  and one predefined space  1040 . The periphery  1130  of the predefined space  1040  may be any appropriately sized geometry to allow movement of the beam member into the predefined space either partially or completely, thereby allowing the lock to occur. Beam member  1050  has a first beam connection  1140  and a second beam connection  1150  (the reference numerals  1140  and  1150  designate ovals drawn around the areas of connection) that join the beam  1050  to the locking mechanism. Beam member  1050  may or may not have a lead-in feature (such as  170  in  FIG. 6 ) to facilitate engagement with the head  400  of the bone fixation device  390 . One advantage of the embodiment shown in  FIGS. 8-10  is the thinness of the locking mechanism. The thin device may not have an upper recess or lower recess ( 210  and  220  as shown in  FIG. 1-7 ). The overall thin profile is advantageous for applications where a low profile implant is needed such as a rib fracture plate or in maxillofacial applications. One advantage of the present invention is that the function of the locking mechanisms  1200  and  300  is independent of the overall thickness of the plate. Other embodiments of bone plate  1000  include a mesh type configuration that would provide a thin mesh type plate with a minimal thickness locking mechanism such as illustrated in  FIGS. 38A and 38B . In contrast, known polyaxial locking mechanisms may rely on movement of material in a direction that would affect the overall thickness of the locking mechanism. Due to the predefined space of the current invention, the movement of the material can occur radially and/or axially without affecting the thickness profile of the overall construct. This is particularly advantageous in applications where low profile bone plates are required. 
         [0071]    The locking mechanism  1200  shown in  FIG. 10  has four beam members  1050  and four predefined spaces  1040 . Any combination and orientation of any number of beam members and predefined spaces are within the scope of this invention. 
         [0072]    The locking mechanism shown in  FIGS. 3 and 10  include at least one beam member ( 150  and  1050 ) that has substantially parallel upper surfaces and lower surfaces. The beam members may be in close proximity to the predefined spaces  140  and  1040 , respectively. The size, shape, orientation and configuration of the beam member  150 ,  1050  and corresponding predefined space  140 ,  1040  provide an appropriate interference with the head  400  of the bone fixation device  390 . The bone fixation device  390  illustrated in  FIG. 11  may be any typical, standard locking bone fixation device or a non-locking bone fixation device. However, the embodiments described herein are uniquely advantageous when used with locking bone fixation devices that have a series of threads on their heads.  FIGS. 11-13  show an example of a bone fixation device that may be used in accordance with the various embodiments of this invention. As shown in  FIG. 11 , bone fixation device  390  has a shaft  420  and a head  400 . Shaft  420  is threaded but it may be otherwise configured to engage bone. For example, it may be fully threaded or partially threaded, and may include a helical blade and/or one or more tacks, deployable talons, expanding elements, or other bone engagement features known in the art. Any feature that allows shaft  420  to engage bone is considered within the scope of this invention and may be referred to generally as a “threaded shaft” for the sake of convenience. It is also possible, however, that shaft  420  is not threaded, so that bone fixation device  390  takes the form of a peg or a pin. Such alternative embodiments may be preferred in certain procedures, where there is no concern that the bone fixation device may pull out from the bone or where the orientation/position of the peg/pin relative to the plate and other pegs/pins prevents the construct from pulling out of a bone. 
         [0073]    Shaft  420  may be cylindrical or non-cylindrical, threaded or non-threaded depending on the application. The minor diameter  440  may have a consistent dimension or may have a varying dimension along its length. For example, for a threaded application, the minor diameter  440  may taper, while the major diameter  450  remains constant. The opposite is also possible. 
         [0074]      FIG. 12  shows one embodiment of a bone fixation device that has a tapered head  400 . In this particular embodiment, minor diameter  480  is larger than minor diameter  470 , which is larger than minor diameter  460 . This tapered geometry allows for engagement with the beam member via the first diameter  460 . The diameters of  460 ,  470 , and  480  are sized to fit the passage opening  130  or  1030 . The larger diameter  480  is sized to prevent the bone fixation device from proceeding through the locking mechanism. As the screw is advanced, the radial compression increases thereby “locking” the bone fixation device to the locking mechanism. In this embodiment the larger diameter  480  is effectively a radial stop. The major diameters of the head  400  are tapered correspondingly with the minor diameters. Major diameter  485  is larger than major diameter  475 , which is larger than major diameter  465 . The major diameters are appropriately sized to fit within the locking mechanism boundaries of each embodiment. Alternate embodiments may not have a typical threaded geometry. For example, for a unidirectional locking application, the bone fixation device may have a pan head with a cam or groove feature that will engage the locking mechanism. There are numerous alternate embodiments that would be obvious to those skilled in the art with the aid of the present disclosure. One advantage of this locking mechanism is the ability to achieve multi directional, including unidirectional, locking without the need for a threaded feature in the plate. The locking mechanism can also be used with bone fixation devices that are not locking. The shank  410  shown in  FIG. 12  may or may not be a distinct feature on an appropriate bone fixation device. The threaded head  400  may transition into the shaft  420  without a smooth shank  410 . 
         [0075]      FIGS. 14 and 15  show an assembly of a bone fixation device  390  and the bone plate  100 . The bone fixation device  390  is a bone screw with a threaded head.  FIGS. 14 and 15  show the bone fixation device in a neutral or zero degree position.  FIG. 15  shows the engagement  490  between the beam member  150  and the head diameter  470 . As the head  400  engages the locking mechanism the beam is allowed to move to accommodate the needed engagement. The deformed state of the fixation assembly with fixation device  390  therein is shown in  FIG. 36A . In this case, a helical threaded feature is used, but in other embodiments, this could be replaced with a variety of other features including concentric rings, cams, etc. In the present invention, the beam may move into the space above and/or below the beam member; however, the present invention also allows the beam, when engaged with the bone fixation device, to move into the predefined space. Thus, the present invention allows for a radial movement in addition to other degrees of freedom. 
         [0076]      FIGS. 16 through 18  show an assembly of a bone fixation device  390  and the bone plate  100 . The bone fixation device  390  is a threaded head bone screw.  FIGS. 16-18  show the bone fixation device in an angled position. For this image the angle is approximately 20 degrees. This 20 degree angle is not a limiting feature and is only used for demonstration purposes. A wide range of angles may exist between the bone fixation devices and bone plates of the present invention.  FIG. 18  shows the engagement  490  between the beam member  150  and the head diameter  470  (see  FIG. 11 ). It should be noted that as the bone fixation device is introduced at different angles into the passage hole, the beams  150  will engage various positions of the head of the screw  400 . As the head  400  engages the locking mechanism, the beam moves to accommodate the needed engagement. The beam may move into the space above and/or below the beam member. However, the present invention also allows the beam when engaged with the bone fixation device to move into the predefined space allowing for a radial movement. 
         [0077]    A third embodiment of the locking mechanism is shown in  FIGS. 19, 20 and 21 . The locking mechanism  690  may be similar to that described in respect of other embodiments herein with the inclusion of an interruption  735 . Interruption  735  divides the beam member  710  into two members, each member having only one connection point  740  as designated by the oval in  FIG. 20 . The interrupted beam member does not project toward the axis of the passage hole  730 . The predefined space  720  has an interruption or connection space  735  to the passage hole  730 . The beam members are allowed to move into the predefined space  720 . Such an embodiment may be used for ease of manufacturing. Alternate embodiments may vary the size, geometry, configuration, volume, shape, perimeter, and/or other features of the predefined space and/or beam member. Furthermore, alternative embodiments may encompass any relationship between the number of beams, number of predefined spaces, size, geometry, configuration, volume, shape, perimeter, etc. 
         [0078]    The present invention does not require a threaded feature in the implant. This allows for a number of different bone fixation devices to be used. It also allows for a substantially thinner implant than prior art locking mechanisms. The non-threaded aspect enables locking mechanisms to be manufactured using materials that were previously thought to be non-viable options due to the difficulty in producing typical locking mechanisms or the inability of the material to produce a durable lock. For example, materials like nitinol are very costly and difficult to thread and are typically not used where a locking interface is needed. Also, materials such as PEEK are not suitable for the locking mechanisms used by many prior art devices due to the destructive nature of the locking mechanism or the cantilevered geometry involved. Such geometries may fracture and break if produced in materials such as PEEK. Also, cross-threading, gouging, or stripping of PEEK may generate unwanted wear debris. Additionally, polymeric materials may not allow for a robust locking interface when used in conjunction with known locking mechanisms. 
         [0079]      FIGS. 22 and 23  show numerous alternate embodiments of the locking mechanism. All embodiments show varying size, geometry, configuration, volume, shape, perimeter, etc. of the passage holes  801 ,  811 ,  821 ,  831  predefined spaces  803 ,  813 ,  823 ,  833  and, beam members  802 ,  812 ,  822 ,  832 . It should be noted that the beam member itself may also have a predefined space or a passage hole. 
         [0080]    In  FIGS. 31 and 32 , an alternate embodiment is shown that may be manufactured as a laminate construct. Bone plate assembly  800  includes a top plate  830  and a bottom plate  840 . When assembled, a top surface  810  is created from the top plate  830  and a bottom surface  820  is created from the bottom plate  840 . A passage hole  850  is present as well as the beam member(s)  860  and the predefined space(s)  870 . In this representation, the locking mechanism is part of the bottom plate  840  and the top plate  830  incorporates a through hole that aligns with the locking mechanism. Alternate embodiments could have part of the locking mechanism on one plate and other features on another plate. For example, one plate may have two beam members and two predefined spaces while another plate may have multiple beam members and predefined spaces such that when assembled, the various features of the locking mechanism are no longer co-linear. The laminate construct may be made up of multiple plates (i.e. more than one). The embodiment shown here consists of two plates. In other alternative embodiments, more than two plates may be secured together to form laminate constructs. 
         [0081]    The benefits and advantages of the locking mechanism of the invention can also be achieved as a permanent assembly.  FIGS. 33, 34 and 35  show an embodiment of a bone plate  900  that has a locking mechanism  970  that comprises a passage hole  930 . Passage hole  930  has a beam member  950  that is a component that is assembled to the plate. In this particular embodiment, the beam member  950  is a pin that is assembled into the bone plate  900  via a hole  960 . This assembly creates a predefined space  940 . This embodiment has the benefits and advantages described in connection with other embodiments herein. The beam members  950  may or may not be coplanar and/or coaxial. Beam members  950  may or may not be formed of the same material as the bone plate  900 . Based on the disclosure herein, those skilled in the art will understand that an assembly construct can have a wide variety of sizes, geometries, configurations, volumes, shapes, perimeters, etc. This embodiment may or may not be combined with the embodiment described in  FIGS. 31 and 32 . 
         [0082]    The principles of the present invention can also be incorporated into the alternate bone fixation devices instead of or in addition to a bone plate.  FIGS. 24-26  show an embodiment of a bone fixation device  500  that includes a predefined space  510  in the head of the bone fixation device. The predefined space  510  is open to the perimeter via the interruption  540 . The beam member  520  is created and allowed to move into the predefined space when engaged into a bone plate. An alternate embodiment of a bone fixation device  600  incorporating the current invention is shown in  FIGS. 27-30 . The bone fixation device  600  includes a predefined space  610  in the head. In this embodiment, the predefined space  610  does not have an interruption, thereby creating a single beam member  620 . The beam member  620  moves into the predefined space when engaged into the bone plate. The bone fixation devices described in  FIGS. 24-30  show a mostly cylindrical head, but alternate embodiments could include bone fixation device heads that are non-circular in cross-sectional shape. For example, tri-lobular, elliptical, equilateral polygonal, or other cross sectional shapes may be used to form the head of the bone fixation device. 
         [0083]      FIGS. 36A, 36B and 36C  are provided to illustrate the deformation of the beam members  150  as a result of screwing in a bone fixation device  390 .  FIG. 36A  is essentially a partial bottom view of  FIG. 14  illustrating fixation device  390  in the locking mechanism elements.  FIG. 36B  illustrates the condition and positions of locking mechanism elements of  FIG. 36A  but without fixation device  390 . As can be seen from both  FIGS. 36A and 36B , fixation device  390  causes beam members  150  to be deflected into predefined spaces  140  and it causes optional lead-in features  170  to be deformed. This combination of deflection and deformation locks fixation device  390  into the locking mechanism, but either deflection or deformation can also be sufficient to cause locking. In  FIG. 36C , beam members  150 D have been deflected to a point where they have “bottomed out” in predefined spaces  140  and beam member  150 P has also been substantially deflected but not bottomed out. 
         [0084]      FIGS. 37A-37D  illustrate a blind hole configuration wherein predefined spaces  1240  do not pass all the way through plate  1300 .  FIG. 37A  is a top view of plate  1300  and  FIG. 37C  illustrates, independently of plate  1300 , the elements of the locking mechanism, namely, opening  1230 , predefined spaces  1240 , beam members  1250  and countersink  1270 . Section  37 B shows predefined spaces  1240  that do not pass all the way through plate  1300 .  FIG. 37D  is a bottom view of the elements of the locking mechanism of plate  1300 . 
         [0085]      FIG. 38A  is a top plan view of mesh  1400  having locking mechanisms  300  of the type illustrated in  FIG. 3 . Connecting elements  1401  connect the locking mechanisms  300  to one another to make up the mesh.  FIG. 38B  is a perspective view of  FIG. 38A . 
         [0086]      FIGS. 39A-39C  illustrate a locking mechanism having a non-orthogonal orientation.  FIG. 39B  illustrates the locking mechanism in plate  1500 . The elements of the locking mechanism independent of the plate are illustrated in  FIG. 39A , namely, opening  1530 , predefined spaces  1540  and beam members  1550 .  FIG. 39C  is a section view of  FIG. 39B . 
         [0087]    Another non-orthogonal locking mechanism is illustrated in  FIGS. 40A-40C . Plate  1600  has a recessed locking mechanism  1601 . The mechanism has an opening  1630 , predefined spaces  1640  and beam members  1650 .  FIG. 40A  is a top plan view of plate  1600  and  FIG. 40B  is a section view thereof. The elements of the locking mechanism are illustrated in  FIG. 40C . 
         [0088]      FIG. 41A  is a top plan view of locking mechanism  1701  in curved plate  1700  and  FIG. 41B  is a section view thereof. The locking mechanism has an opening  1730 , predefined spaces  1740  and beam members  1750 . 
         [0089]      FIGS. 42A-42C  illustrate a locking mechanism embodiment having stacked beam members  1850 A and  1850 B in a plate  1800 .  FIG. 42A  is a top view of plate  1800  illustrating opening  1830 , predefined spaces  1840  and beam members  1850 A. In section view  42 B and the perspective view of the locking mechanism elements  42 C beam members  1850 B are illustrated. Beam members  1850 B have optional lead-in features  1870 B and somewhat small optional lead-in features  1870 A are in beam members  1850 A. The stacked beam members are separated by space  1802 . In this illustration there are two stacked beam members but there can be three or more as will be apparent to those having skill in the art based on the description and drawings herein. 
         [0090]      FIG. 43  is a perspective top view of acetabular cup  1900  having locking mechanisms  1901  (see  FIG. 44A ).  FIG. 44  is a top plan view of acetabular cup  1900  and  FIG. 44A  is a section view thereof.  FIG. 45  is a side elevation view and  FIG. 46  is a bottom perspective view of acetabular cup  1900 . The locking mechanism  1901  is in a recess  1903  on the inside of acetabular cup  1900  and it is flush with the outside surface of the cup. The elements include opening  1930 , predefined spaces  1940  and beam members  1950 . Optional lead-in features  1970  are also shown. 
         [0091]      FIGS. 47A-47C  illustrate intramedullary nail  2000 . The nail is illustrated in perspective in  FIG. 47A .  FIG. 47B  is a partial side elevation view and  FIG. 47C  is a partial top elevation view of nail  2000 . The locking mechanisms  2001  are variously located along the nail as a matter of design choice depending upon the application for the nail. In this embodiment, there is a locking mechanism  2001  in nail head  2004  and other locking mechanisms  2001  are arranged along the shaft  2005 . The locking mechanism  2001  is recessed below the nail surfaces and each mechanism contains an opening  2030 , predefined spaces  2040  and beam members  2050 . 
         [0092]    As will be apparent to those having skill in the art based upon the description and drawings herein, the locking mechanisms of the present invention can be incorporated into any implant device that needs to be affixed to bone. 
         [0093]    Various manufacturing methods may be used to make the components of the current invention. Some may result in beam members that are not flat in shape. The orientation of the individual beam members shown and described herein is not limiting. For example, if a bone plate was machined according to the principles of the current invention and then stamped to a final shape, the locking mechanism may also undergo a forming that would maintain parallelism between the top and bottom surfaces of a beam member, but the surfaces may not necessarily be flat.