Abstract:
An orthopedic plate has a portion with a curved bottom surface that is designed to extend longitudinally along the bone and change the inferior curve as it advances proximally along the bone from a shallower to a sharper radius and further spirals downward as the plate advances. The plate includes a set of tabs, offset from the longitudinal axis of the plate to provide for better pullout values. The ears may be located at the terminal portion of the plate or somewhat more intermediate to the terminus of the plate, depending on the intended application. A point in the center of the central screw hole can be used to define the origin of the plate, and the angles of the screw and/or pegs holes can be referenced with Z, Y, and Z coordinates relative to this central hole.

Description:
[0001]     This application is based on U.S. Provisional Application Ser. No. 60/780,027 filed on Mar. 7, 2006 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to an orthopedic plate for fixation of bones. In particular it relates to a terminal section of an orthopedic plate that is useful for stabilization of small bones; for example, for a tibial plate for fixation of a tibial fracture, or for a distal radial plate for fixation of a distal radial fracture, or other fracture areas that can benefit from the design of the present invention.  
       BACKGROUND OF THE INVENTION  
       [0003]     The ankle joint involves the intersection of the tibia, the fibula and the tarsals and metatarsals. The wrist is the joint formed at the intersection of the radius, the ulna, the carpals and the metacarpals. Both of these joints are designed to allow a great deal of freedom in the movement of the relevant appendage (i.e. the hand or foot). Attendant with this relative freedom, the joint itself is somewhat unstable, and easily subjected to trauma resulting in displacement or distortion within the bones of the joint, and in harm to the bones themselves. The wrist is the most frequently injured area of the upper extremity with three fourths of wrist injuries involving a fracture of the distal radius, and/or of the radius, and the ankle is subject to similar statistics with respect to the union of the tibia, the tarsals and the metatarsals. These injuries usually present in an emergency room setting, and often involve a fall for example for the wrist, onto an outstretched hand, and for the ankle, they involve a misstep onto a foot causing a rolling of the ankle. While the past conventional wisdom has included a belief that such injuries will tend to heal sufficiently on their own, there is often a loss of function and an early onset of arthritis that can be precipitated by the misdiagnosis and improper treatment of such injuries.  
         [0004]     The treatments known for trauma to the extremities have included external stabilization and fixation such as by plaster casts, external fixators, and orthopedic plates. Casting alone, presents the possibility of misalignment of the fragments which can lead to severe loss of function and early onset of arthritis, if the fracture is not properly reduced, and/or if the fragments do not stay in a reduced state, in particular where the patient is not compliant. External fixators have been demonstrated to have an efficacy, but are cumbersome, cosmetically unappealing, and can lead to the possibility of infection at the attachment sites.  
         [0005]     In order to avoid the foregoing problems, surgeons often consider methods of internal fixation, which typically include wire and/or screws, and plates. One issue presented by the use of wires is that a construct is time-consuming to construct; and screws alone, often do not provide the stability required for fusion of the fragments. Plates have the benefit of providing a construct that is designed for ease of implantation, and at the same time have the disadvantage that there is a significant variety in the shape and size of individual bones. Further, in particular, the tibia and radius bones are relatively small so that individual variations are relatively more significant than in larger bones, such as the femur, the pelvis, and the humerus. Moreover, the flesh surrounding the ankle joint is particularly dense with tendons, ligaments, nerves and blood vessels all of which are less forgiving of the intrusion of a metal construct than muscle or fatty tissue. This is also true for the wrist joint, particularly on the volar (or thumb) side.  
       SUMMARY OF THE INVENTION  
       [0006]     The orthopedic plate of the present invention has a portion that is designed to extend longitudinally along the bone. This portion has an inferior curved surface which faces, or in some, but not necessarily all instances, touches the bone surface. More specifically, the curved surface is intended broadly to face the bone and to touch along its surface so as to support it on the surface of the plate (i.e. the surface facing the surface of the bone) so much as is allowed given the particular variations in individual bones. This portion of the plate changes this inferior curve as it advances proximally along the bone from a shallower to a sharper radius and further spirals downward toward the more advanced side of the plate. The more advanced side means the side which advances further along the longitudinal axis. Further, the plate in accordance with the invention has a plurality of screw holes, including one or more which are positioned along a central portion of the plate and further which preferably includes two or more which are offset from the central portion of the plate. The screw holes can be threaded so as to accept screws having threaded heads which will lock into position, or alternatively so that a screw with a smaller rounded smooth head can be screwed into the bone and mesh with the internal threads of the screw holes.  
         [0007]     In a preferred embodiment, the plate includes a set of tabs or “ears” which are offset from the longitudinal axis of the plate, and further which allow the placement of screw holes that are offset from the longitudinal axis of the plate, as well as being offset longitudinally from each other. This allows the plate to be contoured about the circumference of the bone, and for the screws to be positioned at a convergent angle to provide for better pullout values, i.e. such that it requires a greater force to pull the screws from the bone. The ears may be located at the terminal portion of the plate or somewhat more intermediate to the terminus of the plate, depending on the intended application. The plate may also include an intermediate set of ears that similarly have a pair of offset intermediate threaded screw holes that are both longitudinally and laterally, or radially offset from the longitudinal axis of the plate, and which accept screws so as to have their axes at convergent angles. Again, the feature provides for better pullout values, and helps to avoid interference of the screws in the bone. In this instance, the plate includes a central screw hole which is located between the proximal pair of ears, and the intermediate pair of ears. This screw hole is preferably positioned so that the axis forms a right angle relative to the longitudinal axis of the plate, and further relative to a lateral axis through the hole. Thus, a point in the center of the central screw hole can be used to define the origin of the plate, and the angles of the screw and/or pegs holes can be referenced with X, Y, and Z coordinates relative to this central hole. Further, the topography of the head can be defined using this coordinate system, which permits the manufacture of the plate using computer generated imaging.  
         [0008]     Distal to the intermediate pair of ears, the plate includes a slot which is radiused at either end to accept a screw having a head of the same dimensions as the threaded screw holes. The slot is elongated along the longitudinal axis of the plate. This allows the plate to be loosely attached by inserting a screw through the slot, and prior to tightening the plate can be slid in the longitudinal direction to allow the plate to be optimally positioned on the bone. The slot also allows the bone to be viewed through the plate preferably in the vicinity of the fracture.  
         [0009]     In one embodiment, the plate of the invention may include a portion or head having a profile which flares from the sides of the plate to a leading edge that includes a central oblique linking area. This embodiment is designed expressly for use in the distal radius and the oblique linking area is designed to help to mark the placement of the plate relative to the radius. The head is shaped like a heart where the lobes have been asymmetrically truncated, like the palm of a hand, or like a modified kidney shape. Further in this embodiment, the head has a complex topography in the Z direction which echoes a generalized shape for the distal volar surface of a radius. The lunate prominence of the head has a lower elevation in the Z direction than the elevation of the styloid prominence in the direction relative to the radius. The longitudinal axis at the center of the proximal portion of the bone defines the Y direction, and the X direction extends transverse in a direction in which the bone widens. Further, the plate includes an oblique depression, or cup, that extends from the rounded pinky side of the head and gradually morphs into the elevated styloid prominence in one diagonal direction, and rises less gradually upward into the lunate prominence on the other side of the head. This distal cup undulates to define a superficial (i.e. relative to its surface) serpentine as it links into the proximal portion of the plate. The head preferably includes holes for pegs or screws which may be fixed, or variable. In other embodiments, such as for the distal tibias, the plate may include a corresponding head portion which is designed specifically to support the ankle joint at the union of the tibia, fibula, the tarsals and the metatarsals. Similarly, designs for other indications may include other head shapes, or none at all, so that the plate is straight, or even symmetrical from the top view about an axis transverse to the longitudinal axis of the plate. In the Z direction, the plate mimics the reverse spiral of the radial bone as it extends proximally away from the distal portion. Thus, the proximal portion of the plate appears to twist or spiral along the longitudinal axis, and includes a greater radial bend as it extends proximally since the bone becomes smaller and more circular in cross-section.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a top view of an orthopedic plate and plate head in accordance with a first embodiment of the invention for use on a left distal radius;  
         [0011]      FIG. 2  is a perspective view of the plate of  FIG. 1  viewed from the outer proximal surface looking toward the head with the styloid side of the plate downward;  
         [0012]      FIG. 3  is a cross section of the plate of  FIG. 1  taken along line  3 - 3  in  FIG. 1 ;  
         [0013]      FIG. 3   a  is a detail of the central screw hole of  FIG. 3 ;  
         [0014]      FIG. 4  is a cross section of the plate of  FIG. 3  taken along line  4 - 4  in  FIG. 3 ;  
         [0015]      FIG. 5  is a view taken from the styloid side edge of the plate of  FIG. 1 ;  
         [0016]      FIG. 6  is a view taken from the proximal edge of the plate of  FIG. 1 ;  
         [0017]      FIG. 7  is a section of the plate taken along line  7  of  FIG. 1 ;  
         [0018]      FIG. 7   a  is a detail of the screw hole of  FIG. 7 ;  
         [0019]      FIG. 8  is a view from the side of the lunate prominence with the plate head in a lowered orientation and viewing the head in partial section to illustrate the detail of the threads of the peg holes;  
         [0020]      FIG. 8   a  is a detail of the peg holes from  FIG. 8 ;  
         [0021]      FIG. 9  is a top view of the plate of  FIG. 1  showing the lines at which the lateral sections of  FIGS. 9   a  through  9   g;    
         [0022]      FIG. 9   a  is a section in the Y direction taken at line  9   a  of  FIG. 9 ;  
         [0023]      FIG. 9   b  is a section in the Y direction taken at line  9   b  of  FIG. 9 ;  
         [0024]      FIG. 9   c  is a section in the Y direction taken at line  9   c  of  FIG. 9 ;  
         [0025]      FIG. 9   d  is a section in the Y direction taken at line  9   d  of  FIG. 9 ;  
         [0026]      FIG. 9   e  is a section in the Y direction taken at line  9   e  of  FIG. 9 ;  
         [0027]      FIG. 9   f  is a section in the Y direction taken at line  9   f  of  FIG. 9 ;  
         [0028]      FIG. 9   g  is a section in the Y direction taken at line  9   g  of  FIG. 9 ;  
         [0029]      FIG. 10  is a top view of a second embodiment of the distal radius plate of the present invention;  
         [0030]      FIG. 11  is a view from the proximal portion of the radial bone showing the plate in accordance with the present invention in position on the volar side of the bone and illustrating the angles for the pegs;  
         [0031]      FIG. 12  is a top view of a third embodiment of the distal radial plate of the present invention with fixed angle pegs, and having an extended proximal portion;  
         [0032]      FIG. 13  is a side perspective view of the plate of  FIG. 12 ;  
         [0033]      FIG. 14  is a top view of a fourth embodiment of the distal radial plate of the present invention with both fixed angle and variable angle locking pegs, and having an different embodiment of the extended proximal portion;  
         [0034]      FIG. 15  is a side perspective view of the plate of  FIG. 14 ;  
         [0035]      FIG. 16  is a detail of the head of the distal radial plate of  FIG. 14  showing the locking cam inserts in position in the peg holes of the head;  
         [0036]      FIG. 17  is a top view of the locking cam insert used in the variable axis embodiment shown in  FIGS. 10, 14  and  15 ;  
         [0037]      FIG. 18  is a cross section of the locking cam insert of  FIG. 17 ;  
         [0038]      FIG. 19  is a side view of a variable axis locking screw for use with the embodiment shown in  FIGS. 10, 14  and  15 ;  
         [0039]      FIG. 20  is a top view of the variable axis locking screw of  FIG. 19 ;  
         [0040]      FIG. 21  is a side view of a non-locking screw that can be used as part of the plate system of the present invention;  
         [0041]      FIG. 22  is a cross section of the non-locking screw of  FIG. 21  taken along line  22  of  FIG. 21 ;  
         [0042]      FIG. 22   a  is a detail of the thread of  FIG. 22 ;  
         [0043]      FIG. 23  is an end view of the insertion tip of the screw of  FIG. 21 ;  
         [0044]      FIG. 24  is an end view of the torque receiving recess of the head of the screw of  FIG. 21 ;  
         [0045]      FIG. 25  is a side view of a locking screw that can be used as part of the plate system of the present invention;  
         [0046]      FIG. 26  is a cross section of the non-locking screw of  FIG. 25  taken along line  26  of  FIG. 25 ;  
         [0047]      FIG. 26   a  is a detail of the head of  FIG. 26 ;  
         [0048]      FIG. 27  is a top perspective view of a drill guide that can be used with the plate system of the present invention; and  
         [0049]      FIG. 28  is a cross section of the drill guide of  FIG. 27 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0050]     The present invention relates to an orthopedic plate that can be used to stabilize the fracture of bone such as a radial bone, and in particular to the longitudinally extending plate portion, which tends to be placed proximally to the head, in the event that there is one.  
         [0051]     A first embodiment of the plate is shown generally at  10  in  FIG. 1  which includes a first, most distal portion or head  11  which has a profile from the top view similar to the palm of a hand, or which is shaped like a truncated heart, or a modified kidney shape. The head  11  slopes upward in a complex and organic topography away from the more elongated inversely curving proximal portion  12  of the plate. The head  11  includes a plurality of holes  13  for pegs, which holes can be internally threaded or not, or can also include means to provide for a variable locking axis. The proximal plate portion  12  also includes a plurality of holes  14  for screws, which similarly can include internal threads, or which can be smooth, or include means for a variable locking axis screw. The proximal portion of the plate also includes a slot  15  which is situated near the junction of the head  11  and the proximal portion of the plate, or the neck  16 . The slot  15  can have a smooth internal edge, or can include a textured feature, such as grooves or tracks. The proximal portion also has two sets of tabs or ears, an intermediate pair  17  and a terminal pair  18  which each extend laterally from the longitudinal profile of the plate, and which provide for opposing screw holes that are each offset from the longitudinal axis of the plate and from each other along the longitudinal axis. The central point of a central screw hole  19  provides a point of reference or origin for mapping in three dimensions the topography or superficial locus of any point on the plate, which in turn enables the plate to be made having the complex curving fully contoured configuration that it does. The offset ears provide for convergence of the screws in the proximal or plate portion  12  of the distal radius plate while still avoiding screw interference so as to provide for improved pullout strength as compared to a version where the proximal screws are located along a line, such as the longitudinal axis.  
         [0052]     As shown in this embodiment, the head portion  11  of the plate has a complex profile which is rounded on either side away from the neck area  16  to form a first prominence  21  and a second prominence  23 . The first prominence  21  has a more gradual curve than the second prominence and is also the more distally extending of the two prominences. It is intended to support the radial styloid, and thus is termed the styloid prominence herein. The plate is provided in a left and a right version, which are mirror images of each other. The plate is generally intended to be implanted on the volar side of the radius (i.e. the top side when the arm is supine, and the palm is pointed upward). The styloid prominence  21  is thus on the lateral facing side of the plate, or the thumbward side. The second prominence  23  is designed to fit under the ridge of the lunate process, and is thus termed the “lunate” prominence herein. The distal edge  22  of the head  11  extends in a direction across the longitudinal axis of the proximal portion of the plate in three segments. A first portion  25  extends substantially transverse to the longitudinal axis of the plate to a point slightly more than, or about midway across the head of the plate. A second edge portion  27  links the first portion  25  and the third portion  29  and extends at an oblique angle proximally toward the third edge portion. The edge portion  27  or oblique link helps the surgeon to gauge the placement of the plate relative to the lunate ridge of the radial bone.  
         [0053]     While the plate has tapering areas, the cross sectional dimension is generally sufficiently uniform that the contours of the top surface  30  generally mirror the contours of the bottom surface  31 . In this context, “bottom” or “internal” is used to mean the surface which faces, and which may, but does not necessarily have to touch the bone, and “top” or “external” means the outwardly facing surface. These surfaces undulate to mimic the shape or topography of the radial bone. More specifically, the bottom surface of the proximal portion of the plate includes a concavity or radius  32  along the longitudinal axis where the thumb side of the plate has a greater arc than the pinky side. As might best be viewed in  FIG. 8 , the pinky side of the plate, (i.e., in that view, the right side) forms a shallow serpentine on both the top and bottom surfaces which defines a gentle depression or cup  33  which is followed by a rise toward the lunate prominence  23  of the head. The cup extends and becomes shallower as the plate surface rises toward the styloid prominence, which has the highest elevation in the Z direction. Thus, particularly in the proximal portion, the plate appears to spiral along the longitudinal axis of the radial bone.  FIG. 6  further illustrates this aspect of the plate in accordance with the invention where the Y axis is taken through a central screw hole.  
         [0054]     The topography of the plate is even more clearly shown in the sectional drawings  FIGS. 9 through 9   g  which represent parallel slices taken in the Z planes at progressive locations along the longitudinal axis. It can be seen from these sections that the proximal portion  12  of the plate, as well as the head portion  11  of the plate is substantially non-planar, meaning that there is no significant portion of either the top surface or the bottom surface of either the proximal portion, or the head portion that defines a single plane. Instead, the head of the plate undulates from a central cup area that has a diagonal aspect from its lowest portion near the neck  16  of the plate on the pinky side of the head to the highest portion at the distal area on the styloid side of the plate. Thus, the top or exterior surface of the head  11  has a slightly concave area or cupped area  33  and other areas, such as the styloid prominence  21  and the lunate prominence  23  which are slightly convex on the top surface  30 , or which rise. This transition can be said to cause the head to have top and bottom surfaces  30 ,  31  which undulate as they transition from the proximal portion of the plate  12  to the head portion  11 . Further, the proximal portion of the plate  12  includes a bottom surface  31  which is radiused to fit the curve of the bone as it extends proximally from the wrist joint toward the elbow joint. This concave or radiused area changes as it extends along the longitudinal axis of the plate. In particular, the plate transitions from an area that is flatter in the vicinity of the neck  16 , and which increases in the amount of curve as can be seen by comparing  FIG. 9   d  through  9   g  which illustrate the cross-section of the plate at progressive proximal locations along the longitudinal axis. This topography is mirrored in the left and right versions of the plate, which are enantiomorphs (meaning that there is a three dimensional mirror symmetry) of each other. The plate spirals down the bone changing the internal curvature to accommodate the bone, and further changing the outline, or footprint that would be left on the bone by spiraling along the axis of the bone. Thus, the plate changes cross-section in the Z-direction, and also shifts in the X-Y directions to define this spiral.  
         [0055]     The plate head  11  is further provided with a plurality of holes  40  which receive pegs that are implanted into the distal portion of the radius, or into fragments of the bone. In particular, the distal radius plate head of the present invention is presented in two embodiments. In a first embodiment, all of the holes define a fixed axis for the pegs which they receive. The pegs holes  40  include internal threads  41  which mate with locking threads on the head of the pegs and which therefore lock the pegs in position in the plate and which accordingly lock the bone relative to the plate. Of course, the plate could include peg holes which have no internal threads, or some combination of threaded and non-threaded holes. Alternatively, pegs can be used with a plate having threaded holes, where the pegs are not threaded at the top, but include a head that fits within the major diameter of the internal threads. In yet another embodiment, the pegs can be secured in the plate by means of a variable locking mechanism that allows the pegs to be inserted through the plate holes at a selected angle and to be subsequently locked into position at that angle. It is particularly preferred to provide a combination of locking pegs and variable locking pegs in the same head.  
         [0056]     The holes include a distal hole  42  in the styloid prominence  21 , and a hole in the lunate prominence  45  and one or more (two in the case shown) holes  43 ,  44  in the head intermediate to the two side holes. One or more proximal set of holes is also advantageously provided. For example, a hole  46  may be provided under the styloid hole  42  and a hole  48  may be provided proximal to the hole  45  in the lunate prominence  23 , and a hole  47  may be provided between the hole  46  and the hole  48 . The angles of these holes determine the angles of the pegs that they receive. The angles are defined on a three coordinate matrix where 0,0,0 is the origin and is located at the center of a central screw hole in the plate. Further, the plate is shown as including smaller diameter holes for K wires which help with the placement and angulation of the pegs. Thus, the holes K 43 -K 48  have similar orientations to the holes  43 - 48  (where no K holes are illustrated for holes  42 ,  45  and  47 ). The angles are set to provide for the most common dislocation of fragments and to provide for the optimal fixation using the pegs.  
         [0057]     The design contemplates a plurality of fixed peg holes, including one  42 ,  45  in each of the styloid (i.e. hole one) and lunate prominences (i.e. hole four), which splay outward and away from the plate such that they diverge away from one another to be capable of locking a styloid fragment and/or a fragment from the lunate fossa portion of the radial bone. A second distal-most hole  43  is located generally under the skewed linking area of the head, which defines a peg axis that extends through the radius and distally toward the scaphoid or navicular bone and a third hole  44  is distally aligned between the two holes of the prominences but is slightly backed off proximally from the second hole, with a peg axis that is more transverse than the peg axis of the second hole. The fourth peg hole  45  is the hole of the lunate prominence which is slightly more proximal than the first hole which is located in the styloid prominence. A fifth hole  46  is located in the first rounded side, which is on the styloid or thumbward side, toward the intersection between the proximal portion of the plate, and the plate head. The axis defined by this hole diverges outwardly toward the lateral portion of the radius (in a supine position). A sixth hole  47  is located in a central portion of the head such as on a longitudinal axis of the plate, and a final seventh hole  48  is located most proximally at the intersection of the head  11  and the proximal portion of the plate  12  at the neck  16  of the plate, with the axis of the peg appearing to be more or less transverse relative to the plane defined by the opening of the peg hole.  
         [0058]     In a further embodiment of the invention, pegs or screws are included which have a variable axis with a locking mechanism. While this mechanism is illustrated for use in the head portion of the plate, is should be understood that it could be used in the proximal portion of the plate instead, or as well.  FIGS. 10, 11 ,  14  through  20 , illustrate this embodiment of the invention. In particular, one or more of the peg holes in the head portion  111  of the plate  110  of the first embodiment may be replaced with variable locking pegs, or the pegs may be reoriented. The proximal portion  112  has the same features and is the same as previously described. In the embodiment shown, holes  42 ,  45 , and  47  are each replaced with a variable locking mechanism  142 ,  145 , and  147 . As one example of a variable locking mechanism, the one illustrated includes a camming mechanism on the head of the peg which mates with a cam locking insert that fits into and locks into a hole in the plate. The cam locking insert includes an anchor member that causes the cam locking insert to resist rotation as the camming members of the peg engage the cam raceway of the cam locking insert. Other variable locking mechanisms can be used with this invention, including other expansion inserts which mate with the holes in the plate at a variable angle, but can be locked in position, such as by expansion.  
         [0059]     As an additional aspect of the invention, a distal radius plate is provided in an embodiment which has an elongated proximal portion. This design is illustrated in  FIGS. 12 through 14  and is shown with a distal head having only fixed angle pegs and having both fixed and variable angle pegs. In the embodiment shown in  FIGS. 12 and 13 , the plate  310  has a distal portion, or head  311  and a proximal portion  312 . The head portion includes pegs holes  313  which can be internally threaded so as to define screw holes having fixed axes as is shown in  FIGS. 12 and 13 , or as is illustrated in  FIG. 11 , and one or more of the fixed peg holes may be replaced with a variable axis mechanism, that advantageously also provides for locking of the angle of the axis. Again, it is envisioned that the proximal portion of the plate is provided in a right and a left version which are mirror images from each other.  
         [0060]     The elongated version of the plate includes the features of the previously described version, with screw holes  314  in the proximal portion; an elongated slot  315  located along the central axis of the plate, adjacent the neck  316  which is the area that links the head  311 , and the proximal portion  312 . The elongated version of the plate further includes an intermediate tabbed area  317  having opposing offset ears that each receive a screw through an internally threaded screw hole, and a terminal tabbed area  318  that includes opposing offset ears that likewise each includes internally threaded screw holes. This version of the plate includes a central screw hole  319  that defmes the origin for the coordinate system of the plate, and in addition, there are one or more additional longitudinally aligned screw holes  320 . The elongated version of the plate has a proximal portion having a spiraling radiused portion similar to the shorter version except with a longer, and thus, more pronounced spiral. The fixed angle head  311  is the same as for the shorter version and the fixed angle head  11  of  FIG. 1 , and the head  411  shown in  FIGS. 14 and 15  is the same as the head  111  shown in  FIGS. 10 and 16 .  
         [0061]     A camming insert is inserted in the variable axis bore holes, which have concavely rounded sides to permit variable angulation of the camming insert in the bore. The camming insert is a generally circular or ring shaped insert  710  having an expansion gap  712  which is essentially a planar slice taken in the insert so as to create a gap. The insert  710  has a top surface  714  which is generally planar joined to a co-planar bottom surface  716  by an outwardly curving side surface  718 . There is a concentric inwardly curving surface  720  which further includes the cam race  722 , which in this case are two grooves that spiral a portion of the way down and around the inside surface. The grooves are open, and preferably only for a portion of the top  714  where the grooves are located. This open area of the race allows the cams to be introduced into the race. Subsequently, as the screw or peg is turned in the camming insert, the cam engages the cam race and causes the insert to expand at the gap. This action causes the insert to lock in the recess  726  in the plate which receives the insert. Further, the insert  712  includes a stop  724 . The stop is a projection that is received in a well  728  in the recess which retains the stop  724  and prohibits the cam insert from turning with the peg as it is turned relative to the plate.  
         [0062]      FIGS. 19 and 20  show a variable axis locking screw  750 , which has a shaft  751  with a blunt or rounded insertion tip  790 . The shaft  751  tapers throughout its length. The screw includes a locking head  760 . The locking head includes a pair of cam wings  770  which are shaped to engage the race in the locking insert  710  and cause the insert to expand radially outwardly to form a friction fit in the bore hole and lock the camming insert in position in the bore. The shaft of the variable locking screw  750  is threaded with a thread  753  and having a taper to the minor diameter  752  of the shaft  751  over the first three to five turns of the thread toward the insertion tip  790  while the major diameter does not taper. The head  760  further includes a torque driving recess  780 , with an optional bore  782  connected to the torque driving recess by a transitional area  78 , which retains the screw  750  on the post of a screwdriver.  
         [0063]      FIGS. 21 through 24  show a non-locking proximal screw  810 , which is intended in particular for use in the proximal portion of the plate, when it is desirable that the screw does not lock into the plate. The screw  810  has a shaft portion  811  having a thread  813 . The thread  813  shown in  FIGS. 21 through 24  has a taper in the minor diameter  812  over a portion  815  of the shaft  811 , such as about the first three turns of the thread. Thereafter, the terminal portion  816  of the shaft  811  has a constant minor diameter  812 . The screw  810  has a blunt tip  850  and a rounded head  820  having a torque driving recess  830  optionally including a bore  832  to receive the post of a screwdriver to retain the screw on the screwdriver. The head has a spherically rounded lower portion  834  and a rounded upper portion  836  where the maximum outer diameter is smaller than the inner diameter of the threaded proximal screw holes. The shaft  811  has a minor diameter  512  about which the thread  813  spirals. The thread  813  includes a spiraling radial edge  514  best viewed in the thread detail  FIG. 22   a , which defines the major diameter. The thread further includes a front thrust face  815  which forms an angle of about 20°+/−5° to a plane transverse to the longitudinal axis of the screw. The trailing face  816  of the thread  813  forms an angle of about 5°+/−2° to the same plane.  
         [0064]      FIGS. 25 through 26 ( a ) show a locking proximal screw  860 , which is intended in particular for use in the proximal portion of the plate when it is desirable that the screw locks into the plate. The screw  860  has a shaft portion  861  having a thread  863  similar to the thread previously shown. The thread  863  shown in  FIGS. 25 and 26  has a taper in the minor diameter  862  over a portion  865  of the shaft  861 , such as the first three turns of the thread. Thereafter, the terminal portion  866  of the shaft  861  has a constant minor diameter  862 . The head of the screw  870  includes external locking threads  883  as can be best viewed in the head detail in  FIG. 26   a . These threads also include a radial edge  884 , a front thrust face  885 , and a trailing face  886 . The angle of the front thrust face  885  is the same as the angle of the trailing face relative to a plane which transverses the longitudinal axis of the screw, and is about 30°+/−5° for each angle. Thus, the locking thread  883  on the head  870  of the screw is a symmetrical v-shaped thread when viewed in profile in cross section. The head  870  tapers along the longitudinal axis, in both the major and the minor diameter, by a similar amount, as is shown in  FIG. 22   a . For a proximal screw, the taper is about 7°, or about 3.5° per side when measured in cross-section. A larger screw might be used in the distal head of the plate and might have a taper of 20° or 10° per side in section.  
         [0065]     The screw  860  has a blunt tip  890  and a rounded head  870  having a torque driving recess  880  optionally including a bore  882  to receive the post of a screwdriver to retain the screw on the screwdriver. The head has a locking thread  884  which tapers in both the major and minor diameter.  
         [0066]      FIGS. 27 and 28  show a drill guide for either the holes in the distal portion, or for the holes in the proximal portion. The drill guide  910  includes an extending handle  912  with a tapering linking portion  914  and a post  916  which engages the hole in the plate. The post  916  has an internal hole for the drill bit and can have a smooth tapered surface at the terminal end  918  which engages the hole of the plate by friction, or the post end  918  can include threads to lock into the internal threads of the plate and to fix the angle for the fixed screws.  
         [0067]      FIGS. 29 through 34  show a further embodiment of the plate in accordance with the invention. This plate  1010  is comparable to the other embodiments in having a head  1011  joined to a proximal plate portion  1012 . The head  1011  includes a plurality of peg holes  1013  as previously described and the proximal portion includes a plurality of screw holes  1014 . This embodiment of the plate has only a single set of offset tabs  1017  which allows for convergent screws and the plate ends in a terminus  1018 .  
         [0068]     While in accordance with the patent statutes the best mode and preferred embodiment have been set forth, the scope of the invention is not limited thereto, but rather by the scope of the attached claims.