Abstract:
The disclosed fasteners have a substantially cylindrical expansion head to secure the fastener in a support structure. The expansion fastener has a removable locking ring, a head, and a shaft extending from the distal end of the head. The exterior of the head has at least one slot extending from the edge toward the distal end. The slots can extend partially or fully to the base of the head. In one embodiment the locking ring has at least one tab that extends beyond the periphery and a tool receiving area. In one embodiment a channel having wall periphery reduction area receives a locking ring with tabs which, when rotated to contact the reduction areas expand the head. In another embodiment the locking ring has a threaded periphery that interacts with a reduced diameter threaded periphery within the head to expand the exterior of the head.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a non-provisional of U.S. 61/223,517 filed Jul. 7, 2009 which is incorporated by reference as though recited in full. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The invention relates general to biomedical fasteners and in particular to fasteners having an expandable head for the internal stabilization of a fractured bone and/or tissue. 
     2. Brief Description of the Prior Art 
     A variety of techniques exist in the field of osteosynthesis for treating bone fractures. Many known techniques utilize bone screws and bone fixation plates wherein the bone screws are connected to the ends of the bone and the connection carrier bridges the fracture. The connection carrier can in particular be a bone plate, a marrowbone nail or a fixator. With this it is desirable, whilst adapting to the nature of the bone part to be connected, for the optical alignment onto the fragments or for compensating target errors, to be able to incorporate fasteners, such as bone screws, at different angles into the connection carrier. 
     Many bone screws have heads with a roughly hemispherical-shaped seat surface of which one seat surface in passage holes is allocated to a bone plate. If for example with a tibia fracture the two bone pieces must be connected to one another, the metallic bone plate is applied onto the set-up bone pieces. Thereafter the screws are rotated into the bones such that the seat surfaces of the screw heads and of the plate holes come to bear on one another and the plate is pressed against the bone. From this there results a connection of bone parts, bone plate and bone screws. 
     It however has been shown that a loosening of the connection of bone screws and bone plates can take place. One cause lays in the insufficient stability of the angle connections of bone screw and bone plate which are secured by friction forces between the screw head and the plate hole. To resolve this problem an angular stable connection of the bone screw and bone plate must be made. 
     Simple mid-shaft fractures of bones are readily treated by bringing the fracture surfaces together and holding them in the desired orientation with respect to one another through the use of splints, casts and the like. Bones in general have dense outer, strong cortical portions and interior, non-cortical portions that may include cancellous bone. At the ends of bones this strong cortical region is typically thinner and the underlying cancellous bone tends to be a fluid filled porous medium which provides more “motion” and dissipates greater energy with transmission. 
     Comminuted fractures and fractures involving the breakage of a bone into numerous bone fragments are more difficult to deal with since one must attempt to reposition each bone fragment in an orientation relative to each other bone fragment so that the fragments may knit together properly. For this purpose, physicians have often used metal plates that attach to the outer cortical surfaces of the bones and which utilize bone screws to hold the bone fragments in position. 
     Another method involves the use of cerclage procedures in which a wire is, in effect, wrapped about a broken bone (or the bone and bone plate) to hold the fragments in place, the cerclage wire occasionally penetrating through the bone. Reference is made to Johnson et al., U.S. Pat. No. 4,146,022. Yet another common method is fixation of fragments with splints which are internal to the bone&#39;s medullary cavity. These are classified as intramedullary rods or interamedullary fixation devices. These devices may be metallic or polymeric, and typically involve a means to affix the ends of the device to prevent motion of one or more of the bone fragments around the device. When metallic devices are used, screws, pins and sliding nails are used to achieve this fixation. Another method, taught in Berger, U.S. Pat. No. 5,658,310, involves anchoring the balloon portion of a balloon catheter in the medullary cavity at one end of a long bone having a transverse fracture, and stretching the remaining portion of the elastic catheter across the fracture interface within the bone to maintain the fracture interface in compression. It would appear that unless the elastic catheter traverses the precise center of the bone at the fracture site, compressive forces will be uneven across the fracture site. That is, the compressive forces on the side of the bone nearest the catheter will be greater than the compressive forces on the opposite side of the bone, generating an unwanted bending moment across the fracture site. Furthermore, a primarily compressive repair is not able to buttress multiple fragment or share loading as is required to stabilize comminuted fractures, limiting the usefullness of the method to a specific class of simple fractures. 
     Surgical procedures used to mount bone plates and cerclage elements to a bone often require supportive tissue that is normally joined to the bone to be cut from the bony tissue to enable direct visual access to the bone. With cerclage procedures, one must entirely encircle a bone in order to hold the bony parts together. 
     Procedures using bone plates and cerclage elements also often tend to interrupt blood flow to the damaged bone fragments, and thus hinder the healing process. Moreover, the use of rigid bone plates and intramedullary rods especially with locked screws can lead to stress shielding of the fracture site. It is well known (Wolffs law) that bone growth is stimulated when stress is applied. However, continuous, excessive pressure applied to a bone can cause unwanted resorption of bone at the pressure site. In order to promote healing of bone fractures, the fracture surfaces that are brought together during reduction of the fracture should be subject to cyclic or periodic compressive forces so as to stimulate the growth of new bone across the fracture interface without causing bone resorption. When a fracture interface is immobilized, as by a cast, the bone material that is deposited at the fracture interface may have a collagen fiber matrix that is random rather than aligned with the fiber matrix of bone on either side of the fracture, the healed fracture interface being weaker in tension than bone on either side of the interface. 
     Some bone fractures result in the production of many bone fragments, and proper reduction of the fracture requires the fragments to be carefully reassembled next to each other with their fracture surfaces in contact. Bone screws and bone plate devices commonly are used for this purpose. Using bone screw techniques, two bone fragments may be joined together, and these two fragments as a unit may be moved into approximation with a third fragment and joined to it, and so on. Fragments that are thus joined together by rigid screws cannot move with respect to other fragments, and mismatching of the fracture surfaces as the first several fragments are joined together can have a compounding effect, causing mal-union or non-union of fracture surfaces and resulting in far less than perfect bone fragment assembly and healing. 
     As such, articular and comminuted fractures generally require special attention to create a repair construct stable enough to allow early mobilization, but not configured and assembled in a manner which causes stress shielding. 
     Stress shielding results from force transfer through the implanted stabilization device verses the bone fragments. This situation is exacerbated when bone fragments are held apart by the fracture repair implants. Appropriate reduction of fracture fragments is more important when more rigid “locked” fixation devices are employed as excessive stress-shielding can result in a non-union. The optimal results are achieved when: (1) normal bone anatomy is reconstructed; (2) a portion of the physiologic force is directly transmitted through the bone; and (3) the bone fragments are reassembled and supported in a manner that the fragments, and particularly any articular surface fragments, move less than about 1 to 2 mm in the early post operative stages while callus and/or bone are being formed. 
     Successful use of flexible plating techniques in unstable fracture patterns is dependent, in part, on the use of a combination of devices such that each fracture fragment is stabilized via direct fixation, buttressing or force neutralization. 
     When dealing with plating systems the placement of multiple screws on each side of the fracture can distribute of loading between more than one screw on either side. 
     Stabilization of a fracture requires prevention of translation in all three directions and rotation about all three axes. Restraining a point solves translation but not rotation. Plates provide some rotational stability. The best mechanical advantage is obtained during fixation when plates (or screws) are not placed along the same axis. 
     A range of fasteners are needed create rigid constructs which can provide mechanical stability to an injured skeletal structure, and yet facilitate optimal healing. Among the commonly used stabilizers are internal and external fasteners such as headed bone screws, pitch differential bone screws, bone screws with lag fragments, bone screws and pegs which, when locked to plates or rods, buttress fragments, bone bolts, bone nails, bone pins, bone plates, rods, rod connectors, cables, wires, external and adjustable fixators, et cetera. 
     Infractures in metaphyseal and epiphyseal bone, a single-sided internal fixation construct using non-rigid connections to plates or rods can not provide sufficient stability to prevent undesirable motion under non-resistance loading or passive motion, let alone normal functional loads. This is particularly applicable when pathological bone or comminution is encountered, and in certain juxta articular impaction fractures (e.g. a die punch fragment), In many cases appropriate stability can only be achieved by use of constructs with a combination of features such as rigid or semi-rigid connections (locked pegs or screws, unilateral motion as in sliding compression hip screw or sliding spinal plates), or use of multiple plates and fasteners or nails and fasteners. 
     Aptus by Medartis International (Germany) provides a fastener that retains its position through a surface wedge fit, relying on surface friction. This device, however, provides minimal material interference to resist pull out or pull through. 
     In U.S. Pat. No. 6,955,677 Dahners discloses the use of spherical threads on screws which tap in to a softened or compliant region of a plate which has been “disposed” on the inside surface of the aperture to facilitate this tapping. 
     SUMMARY OF THE INVENTION 
     The disclosed fasteners have a expansion head to secure the fastener in a support structure. The expansion fastener has a removable locking ring, a head, and a shaft extending from the distal end of the head. The exterior of the head has at least one slot extending, extending partially or fully, from the edge toward the distal end. In one embodiment the locking ring has an outer periphery, at least one tab that extends beyond the periphery and a tool receiving area. 
     The head is substantially cylindrical with a proximal end, middle section and a distal end. The proximal end has an open area with an edge, a base and a first diameter. The distal end has a tool receiving area and a diameter less than the diameter of either the proximal end or middle section. The middle section has a tool receiving area that is contiguous with the open area of the proximal end and a diameter greater than the distal and proximal ends. 
     A channel is formed along the periphery of open area by a top rim and the base having a channel wall. The interior diameter of the top rim is dimensioned to receive the outer periphery of the locking ring and at least one tab receiving area within the top rim is dimensioned to receive the locking ring tabs. There is a wall periphery reduction, preferably gradual to control expansion, adjacent to each of the tab receiving areas. The rotation of the locking ring to place the tabs in contact with the wall periphery reduction causes the exterior of the head to expand at the slots. 
     The exterior of the head can be smooth or have at least one thread having a height and a depth and extending from and around head. The thread can be perpendicular to the axis of the shaft; have parallel ridges to the axis of the shaft; or be perpendicular to the axis of the shaft. The shape of the head can be spherical with spherical threads or torroidal with torroidal threads. Alternatively the exterior of the head can be cross-hatched or a combination of the above. 
     The expansion fastener head can also have at least one flat extending from the proximal end to the distal end of the head as well as a cutting flute, adjacent one or more flats. 
     In another embodiment the locking ring is secured to the interior of the head by threading. The tool receiving area can be recesses or other applicable means. The locking ring has a treaded outer periphery and a tool receiving area. The interior of the substantially cylindrical head has a diameter that decreases from the edge to the base with a thread pattern matching the thread pattern of the locking ring. As the locking ring is threaded deeper into the decreasing interior diameter of the head, the exterior of the head expands at the slots. 
     To use the disclosed fastener to secure biological material to a support material it is preferably, although not mandatory, that the locking ring be placed into the expansion fastener head. The biological material, such as bone or tissue, is aligned with the support material, such as a plate, bone or other tissue. If holes are required they would be drilled and the material realigned. The fastener threaded shaft is threaded through the support material and into the biological material. Once in place, the locking ring is rotated to expand the head, thereby locking the fastener in place. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The preferred embodiments of the present invention are shown by a way of example, and not limitation, in the accompanying figures, in which: 
         FIG. 1  is a side perspective view of a smooth outer diameter split head fastener in accordance with the disclosure; 
         FIG. 2  is a side perspective view of a threaded outer diameter split head fastener having flats in accordance with the disclosure; 
         FIG. 3  is an enlarged view of the fastener of  FIG. 1  in accordance with the disclosure; 
         FIG. 4  is an enlarged view of the fastener of  FIG. 2  in accordance with the disclosure; 
         FIG. 5  is an end perspective view of the fastener of  FIG. 2  with the locking ring clearly separated from the head of the fastener, in accordance with the disclosure; 
         FIG. 6  is a side perspective view of the fastener of a threaded head, four slot fastener having two flats, in accordance with the disclosure; 
         FIG. 7  is a side perspective view of the fastener of  FIG. 6  clearly illustrating the four slots and the locking ring receiving area in accordance with the disclosure; 
         FIG. 8  is a top perspective of the fastener of  FIG. 6  clearly showing the flats, in accordance with the disclosure; 
         FIG. 9  is a top perspective view of a fastener having a smooth outer diameter and six slits, in accordance with the invention; 
         FIG. 10  is an perspective view of the fastener of  FIG. 9  with the locking ring separated from the head, in accordance with the disclosure; 
         FIG. 11  is a side view of a fastener having a smooth outer diameter head and two slits in accordance with the invention; 
         FIG. 12  is a side view of a fastener having a threaded outer diameter head and two slits having curved distal ends, in accordance with the invention; 
         FIG. 13  is a perspective view of the threaded head fastener having slits and flats with a keyhole distal end to the slit, in accordance with the invention; 
         FIG. 14  is a top view of the fastener head having two flats and four slots with the locking ring partially rotated in accordance with the invention; 
         FIG. 15  is a top view of the fastener head having two flats and four slots with the locking ring partially rotated to provide minimal load in accordance with the invention, 
         FIG. 16  is a top view of the fastener head of  FIG. 15  having increased, but not yet maximum, load in accordance with the invention, 
         FIG. 17  is a top view of the fastener head of  FIG. 15  having maximum load in accordance with the invention, 
         FIG. 18  is a perspective view of the fastener head having two slots with opposing flats with minimum load in accordance with the invention; 
         FIG. 19  is a top view of the fastener head of  FIG. 18  in maximum load in accordance with the invention; 
         FIG. 20  is a top view of the four slot head having no load in accordance with the invention; 
         FIG. 21  is a cut away of the screw of  FIG. 10  having interior threads with the locking ring inserted in a no load position, in accordance with the invention; 
         FIG. 22  is a cutaway side view of the slotted head of  FIG. 10  with the locking ring rotated to provide increased load in accordance with the invention; 
         FIG. 23  is an additional perspective view of the four slot fastener head in accordance with the invention; 
         FIG. 24  is a perspective view of a three slot fastener head in accordance with the invention; 
         FIG. 25  is a perspective view of a two slot fastener head in accordance with the invention; 
         FIG. 26  is a perspective view of a cannulated expansion tool partially inserted into the 4 slot, smooth OD split head fastener in accordance with the invention; 
         FIG. 27  is a side view of a cannulated expansion tool positioned for insertion into a two slot, smooth OD split head fastener in accordance with the invention; 
         FIG. 28  is a perspective view of a cannulated expansion tool inserted into a three slot smooth OD split head fastener aligned with the locking ring in accordance with the invention; 
         FIG. 29  is a perspective view of a solid expansion tool positioned for insertion into a 4 slot, smooth OD split head fastener in accordance with the invention; 
         FIG. 30  is a perspective view of a solid expansion tool positioned for insertion into a two slot, smooth OD split head fastener in accordance with the invention; 
         FIG. 31  is a cross sectional side view of the cannulated expansion tool inserted into a two slot, smooth OD split head fastener in accordance with the disclosure; 
         FIG. 32  is a perspective view of a split lock fastener with a driver bit and expansion tool in place in accordance with the invention; 
         FIG. 33  is a side view of a split lock screw on a driver in accordance with the invention; 
         FIG. 34  is a cutaway view of examples of three different receiving holes that can be used in plates to receive the fasteners in accordance with the invention; 
         FIG. 35  is a cutaway view of three additional examples of different receiving holes that can be used in plates to receive the fasteners in accordance with the invention; 
         FIG. 36  is a cutaway side view of multiple smooth OD fasteners in a plate in accordance with the invention; 
         FIG. 37  is a perspective view of fasteners in a multi-fastener plate in accordance with the invention; 
         FIG. 38  is a perspective view of fasteners in a multi-fastener plate in accordance with the invention; 
         FIG. 39  is a perspective view of fasteners in a multi-fastener plate in accordance with the invention; 
         FIG. 40  is a perspective view of fasteners in a multi-fastener plate in accordance with the invention; 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Definitions 
     Where the definition of terms departs from the commonly used meaning of the term, applicant intends to utilize the definitions provided below, unless specifically indicated. 
     For the purposes of the present invention, the term “aperture surface” refers to any surface, organic or manufactured from natural or synthetic material, to which the head of the fastener is attached. 
     For the purposes of the present invention, the term “plate” refers to a piece of material with greater width and height than thickness, e.g. a thin piece of material. The plate can be flat, angled or curved and can have one at least one hole or groove channel to facilitate use with a fastener. 
     For the purposes of the present invention, the term “Osteosynthesis” refers any surgical procedure that stabilizes and joins the ends of fractured (broken) bones by mechanical devices such as metal plates, pins, rods, wires or screws until healing occurs. 
     For the purposes of the present invention, the term “slit(s)” and “slots(s)” are used interchangeably and refer to the spacing between sections of the fastener head the enable the fastener to expand. 
     For the purposes of the present invention, the term “pathologic bone” includes but is not limited to osteoporotic bone, osteoporotic vertebral bodies, fractured osteoporotic vertebral bodies, fractures of bones due to tumors especially round cell tumors, avascular necrosis of the epiphyses of long bones, especially avascular necrosis of the proximal femur, distal femur, distal radius and proximal humerus and defects arising from endocrine conditions. 
     For the purposes of the present invention, the term pitch differential (Total PD) refers to the number of screw threads on the head multiplied by individual pitch differences. E.g. If pitch differential is 0.1 mm, the Total PD is 0.1×3=0.3 mm for the 3 threads. 
     For the purposes of the present invention the terms “sphere” and “spherical” as employed herein are not limited to exact spheres or spherical contours. The terms are intended to include hole contours that are of progressively decreasing diameters from the proximal end of the hole to the distal end of the hole. The progression forms a curved line and thus a conical contour is outside of the scope of the terms sphere and spherical. 
     For the purposes of the present invention, the term “fastener” refers to any device that joins or affixes two or more objects together. 
     For the purposes of the present invention, the term “flute” refers to a channel, groove, or furrow, on the body of the fastener head, or recessed regions below the spherical surface of the fastener head, that are provided specifically to facilitate tapping or cutting. The flutes can be cut to form a cutting edge at one edge. A flute&#39;s recessed region can have various shapes, but in all cases, a cutting edge or cutting lip is retained at one edge. Preferably, a flute in axial alignment with the shaft of the fastener body. Preferably, the shaft is threaded at an angle which is different from the angle of the threads of the fastener head. 
     For the purposes of the present invention, the term “flat” refers to a recessed region (below the fastener head) that does not feature a cutting edge or cutting lip. Flats can take on multiple shapes which include a truly flat surface, a convex surface or concave surface or a combination or recessed surfaces. 
     For the purposes of the present invention, the term “grooved”, “grooves” or “groove” refers to any channel, valley or path in the fastener surface, including but not limited to spiral, circular, oblong, as well as any other pattern that provides the desired result set forth herein, that forms the threads. 
     For the purposes of the present invention, the term “threaded”, “threads” or “thread” refers to the material between grooves. Preferably, a flute is in axial alignment with the shaft of the fastener body. Preferably, the shaft is threaded at an angle which is different from the angle of the threads of the fastener head. 
     Although the use of threaded-head screws has provided improvements in orthopedic surgical techniques, this method of retaining a screw in a plate is not applicable in all situations. 
     The disclosed fasteners use expansion, with or without additional locking through the use of treads, to retain a screw within a plate. When used with a plate having appropriately sized openings, the disclosed fastener mechanically locks to the plate in a manner to prevent the fastener from moving from the affixed position. Once expanded, the fastener will not rotate, slide pull through or back out of the opening. The disclosed design uses mechanical expansion to create surface pressures and a friction lock. Alternatively, depending upon the materials being used, the disclosed fastener can deform the surface of the bone or plate resulting in another form of mechanical fit. The residual surface tension and/or interference prevent motion of the fastener head at the expansion junction. 
     The disclosed fastener can be used to affix plates to bone, bone to bone or tissue to bone. The appropriate materials can be dependent upon the application and will be known to those skilled in the art. 
     Although prior art expansion fasteners are known, they have heretofore used threading to create the expansion. These have the disadvantage in that debris, such as bone, blood and/or tissue can make the mating of threads difficult. The disclosed system has overcome this disadvantage through the use of an internal expansion ring which, using a cam effect, forces the fastener head to expand when twisted. 
     Expansion is created by a cam effect using an internal expansion ring which when twisted forces the sides of the split, or slotted, fastener head to expand and engage the mating plate surfaces. At least one cam lock surface is required, but optimally 2 or more cam-lock surfaces are incorporated. In this embodiment, the fastener head has an undercut groove that has a cam surface and openings for the lock tabs of the cam lock ring to pass into the groove during assembly. The openings and tabs are sized such that the tabs snap into the fastener head and are retained within the fastener head. The cam is sized to effect expansion as the cam lock ring is turned. 
     In each of the embodiments shown, the expansion member is a ring that is preferably pre-installed into the fastener head. The ring preferably is sized to allow the fastener insertion into the plate or bone with the ring in place. For example, this allows the screw to be driven with the cam lock or thread lock in place. A second component does not have to be assembled to the screw to cause expansion after the screw has been installed and is within the surgical wound space. However a less preferred embodiment would include a dam ring that was either solid or whose center opening was not large enough to allow the screw driver tip to engage the screw while the cam lock is in place. This cam lock would be secondarily installed into the fastener head to cause the expansion lock to the plate holes. 
     The figures hereinafter illustrate the locking ring in different positions in a variety of embodiments. It should be noted that the movement and positioning of the locking ring occurs the same regardless of the exterior configuration of the head or the number of tabs. Figures have been incorporated that illustrate the progression for one embodiment, however not all embodiments have been illustrated in each of the separate positions of the ring. 
     As illustrated herein the tool receiving areas are recesses within the locking, either in the top or within the inner circumference. It should be noted that the tool receiving areas can be any design that will receive the appropriate tool including, but not limited to, slots, holes, or protrusions. Additionally, a single tool, or multiple tools, can be used to insert the fastener. A tool, as illustrated herein, can be used to place the fastener and a second tool used to rotate the locking ring. Alternatively, a single tool having a distal portion for positioning the fastener and a proximal portion that interacts with the locking ring once the fastener is placed. 
     In  FIGS. 1 and 3  the fastener  100  the outer surface of the head  102  is smooth with four slots  108   a ,  108   b ,  108   c  and  108   d . As can be seen in these figures, the slots  108   a - 108   d  are evenly spaced from one another around the head  102  and extend along the sides of the head  102  almost to the threaded shaft  104 . The proximal end  110  of the head  102  is open with an top rim  126  that has been dimensioned to receive the locking ring  120 . The top rim  126  has receiving areas  116  and  118  to receive locking ring  120  tabs  122  and  124 . 
     The periphery of the channel formed by the top rim  124  and the base of the open area gradually narrows, as illustrated in more detail hereinafter, to create the expansion when contacted by the tabs  124  and  122 . 
     In  FIG. 3  it can clearly bee seen how the tabs  122  and  124  of the locking ring fit into the receiving areas  116  and  118  at the initial stage of insertion. 
     The external surface of the disclosed fasteners herein can be smooth or ridged. The ridges of different forms are used to facilitate motion resistance in differing directions, particularly if, during the expansion process, the ridges of the fastener head are deformed into the surface of the plate or bone. 
     The ridges will generally follow the shape of the spherical or torroidal surface of the fastener head and may be one of several forms.
         (A) Circumferential rings perpendicular to the axis of a shaft to prevent rotation of the fastener head relative to the plate or bone under cantilever loading.   (B) Linear ridges which are generally parallel to the axis of the shaft to prevent rotation about the axis of the fastener.   (C) Spherical threads on a spherical surface or torroidal threads on a torroidal surface.   (D) Cross hatch pattern to prevent rotation about the axis of the fastener.       

     When the ridges on the external surface are helical threads, they can be sized such that the threaded peaks protrude or extend beyond the sizing of the mating surface in the plate or the bone. In this case, the thread can be tapered as in the tip of a wood screw to cut a thread into the mating surface. Alternatively one or more flats or one or more cutting flutes can be cut to facilitate thread engagements. In this manner early stability can be achieved with thread interference. This early stability is then enhanced by expansion of the head of the fastener. 
     Similarly,  FIGS. 2 ,  4 , and  5  illustrate the fastener  150  wherein the head  152  has a threaded exterior with flats  160  with threaded shaft  154 . The use of threads  156  and flats  160  are described in detail in co-pending application Ser. No. 12/266,210, filed Nov. 6, 2008 the disclosure of which is incorporated herein as though recited in full. In this embodiment the head  152  has two slots  158   a  and  158   b  on opposing sides of the head  152  with the flats  160  at a 90 degree rotation from the slots  158   a  and  158   b . In  FIG. 4 , the locking ring  170  has been rotated approximately 90 degrees, placing the tab  172  under the flat  160  and contacting the decreased diameter within the channel  180  thereby widening the slots  158   a  and  158   b . In  FIG. 5 , the locking ring  170  has been removed to more clearly illustrate the interior components. The channel  180  can be seen that has been dimensioned to receive the locking ring  170  and receiving areas  162  and  164  to receive the tabs  172  and  174 . As can be seen, the locking ring tabs  172  and  174  are dimensioned to match the receiving areas  162  and  164  to enable the locking ring  170  to by pass the top rim and rest on the bottom rim. 
     The channel  180  is formed by the top rim  184  and the bottom rim, or base,  182  and has a decreasing diameter (as illustrated in more detail hereinafter), therefore forcing the slots  158   a  and  158   b  to expand as the tabs  172  and  174  contact the decreased diameter. 
     The fastener of  FIGS. 6 ,  7  and  8  has a threaded head  200  with four slots  206   a ,  206   b ,  206   c  and  206   d , and two flats  208 . The upper rim  222  and base  224  are illustrated forming the channel  218 . The slots  206   a ,  206   b ,  206   c  and  206   d  have a keyhole opening  210  (only the opening of slot  206   d  is illustrated) at the distal end to permit additional expansion without damaging the head  200 . In  FIGS. 7 and 8  the locking ring  220  was initially inserted with the locking tabs at receiving areas  202  and  216  and resting on the base  224 . In these Figures, the locking ring has been partially turned from the insertion position and starting to engage the narrowed interior of the head  200 . In  FIGS. 9 and 10  the fastener head  302  has a smooth outer surface and six slits  304   a ,  304   b ,  304   c ,  304   d ,  304   e  and  304   f . Each of the slits  304   a ,  304   b ,  304   c ,  304   d ,  304   e  and  304   f  has an opening  306   a ,  306   b , and  306   c  (remaining openings not shown) at the distal end to facilitate spreading. In  FIG. 9  the locking ring  310  has been inserted into the head  302 . As can be seen in  FIG. 10  the interior of the head  302  is threaded  322  with a decreasing diameter. The locking ring  310 , shown prior to insertion in  FIG. 10  and inserted in  FIG. 9 , has an exterior thread that interact with the threads  322  in the interior of the head  302 . The recesses  314  and  316  are configured to receive a locking tool to turn the locking ring  310 . As the locking ring  310  is tightened, it forces the head  302  to expand at the slits  304   a ,  304   b ,  304   c ,  304   d ,  304   e  and  304   f  due to the pressure created with the decreasing interior diameter of the head  302 . 
       FIG. 11  is a side view of a fastener head  350  having a smooth outer diameter head and two opposing slits  352  having a curved distal end  354 . The curved distal end  354  serves the same purpose as the openings described heretofore. In  FIG. 12  the fastener head  360  has threads  362 , flats  366  and dual slits  362 . As with the design of  FIG. 11 , the slits  362  have a curved distal end  364 . 
     The head  380  of  FIG. 13  has threads  388 , flats  382  and two slits  384 . The distal end  386  of the slots  384  have a keyhole shape to facilitate spreading of the walls. 
       FIGS. 14 ,  15 ,  16  and  17  are top views of the fastener head  200  of  FIGS. 6-8  having two flats  208  and four slits  206   a ,  2064   b ,  206   c  and  206   d . In  FIG. 14  the locking ring  230  has been inserted into the receiving area  202  and partially turned.  FIGS. 15 ,  16  and  17  illustrate different degrees of rotation of the locking ring  230 , with  FIG. 17  illustrating the maximum expansion position. 
       FIG. 18  is a perspective view of the fastener head  150  of  FIGS. 2 and 4  showing the locking ring  172  causing minimum load while in  FIG. 19  the locking ring  172  has been rotated to cause maximum load.  FIG. 20  is a top view of the four slot  108   z ,  108   b ,  108   c ,  108   d  head of  FIG. 1  with the locking ring  120  initially inserted. As noted previously, the rotation of the locking ring and expansion of the head is applicable for all embodiments using the interior channel, whether the exterior is threaded or smooth. Therefore, the insertion of the locking ring  172  would appear the same as the insertion of the locking ring  120 . 
       FIGS. 21 and 22  illustrates, through a cutaway of the screw head, the fastener of  FIG. 10 . In  FIG. 21  the threaded ring  310  has been inserted into the head  302  and engaged with the interior threads  322 . In  FIG. 22 , the threaded ring  310  has been tightened, through use of a tool inserted into the recesses  314  and  316 . As described in conjunction with  FIG. 10 , as the ring  310  is tightened in the decreasing diameter of the head  302 , the head  302  expands at slots  306   a ,  306   b ,  306   c ,  3064   d ,  306   e  and  306   f.    
       FIG. 23  illustrates a head having four slots  502   a ,  502   b ,  502   c , and  502   d  with the locking ring  504  inserted into the receiving areas  508 . The upper rim  510  is dimensioned to retain the locking ring  504  in the channel  512 . is a perspective view of a four slot fastener head in accordance with the invention; 
     In  FIG. 24  the head  550  has three slots  552   a ,  552   b , and  552   c  with a receiving area  554   a ,  554   b  and  554   c  adjacent to each slot  552   a ,  552   b  and  552   c.  A three tab locking ring  558  is used to expand the head  550 . As with the embodiments described heretofore, the locking ring  558  rests on the base of the head  550  (not shown) and is maintained for rotation in channel  562  by upper rim  560 . 
       FIG. 25  illustrates a head having dual slits  570   a  and  570   b  with locking ring  580  inserted into the receiving areas  572   a  and  572   b.    
       FIG. 26  show a cannulated expansion tool  602  partially inserted into the head  606  of a four slot, smooth outer diameter fastener. In this figure the locking ring  608  has been inserted into the head  606  and will be engaged once the fastener has been placed 
       FIG. 27  shows a cannulated expansion tool  722  positioned for insertion into a two slot, smooth OD split head fastener  720  having a curved distal end slot  724 . 
     In  FIG. 28  the smooth surface head  736  has three slots  740 , having the three receiving areas  734  and a three tab locking ring  740 . The insertion tool  732  has three flanges  733  to engage each of the locking ring tabs  738 . 
     In  FIG. 29  the solid expansion tool  742  is positioned to be inserted into the smooth exterior head  740  having four slots  746 . As can be seen the expansion tool  742  aligns with the dual tab locking ring  744 . Once inserted the expansion tool  742  rotates the locking ring  744  to apply the appropriate expansion to the head  740  through slots  746 . In  FIG. 30  the same expansion tool  742  is used with head  760  having two slots  762  and dual tabs  764 . As seen, it is preferable that the locking rings having the same number of I tabs have the same dimension, no matter which expansion head being used. This facilitates not only ease of manufacture but convenience of using the same locking tool. 
       FIG. 31  the interior of the smooth head fastener  802  that positioned to receive the cannulated expansion tool  800 . In. 
       FIGS. 32 and 33  are examples of tools that can be used in conjunction with the disclosed fasteners and are for example only.  FIG. 32  is a split lock fastener  822  with a driver bit and expansion tool  820 .  FIG. 33  illustrates a fastener  832  on a driver  830 . 
       FIGS. 34 and 35  illustrate examples of plate receiving holes  850 ,  852 ,  854 ,  856 ,  858 , and  860 . These are examples only and it should be noted that alternate holes can be used as will be known in the medical arts. 
       FIG. 36  illustrates fasteners  882 , inserted into plate  880  at slightly different angles. In  FIG. 37  the fasteners  902  are inserted into plate  900  at more of an extreme angle than illustrated in  FIG. 36 . The fasteners  882 , illustrated in  FIG. 36  are smooth exterior heads  886  with a locking ring  884  that interacts with the channel, as described heretofore. In  FIG. 37 , the fasteners  902  have threaded interiors that interact with the threaded locking ring as illustrated in  FIGS. 10 ,  21  and  22 . 
     In  FIG. 38  the smooth outer surface fastener  606  is shown inserted into plate  920  while  FIGS. 39 and 40  illustrated fasteners inserted into the plate  922  at various angles to illustrate the versatility of the disclosed system. 
     Broad Scope of the Invention 
     While illustrative embodiments of the invention have been described herein, the present invention is not limited to the various preferred embodiments described herein, but includes any and all embodiments having equivalent elements, modifications, omissions, combinations (e.g., of aspects across various embodiments), adaptations and/or alterations as would be appreciated by those in the art based on the present disclosure. The limitations in the claims (e.g., including that to be later added) are to be interpreted broadly based on the language employed in the claims and not limited to examples described in the present specification or during the prosecution of the application, which examples are to be construed as non-exclusive. For example, in the present disclosure, the term “preferably” is non-exclusive and means “preferably, but not limited to.” In this disclosure and during the prosecution of this application, means-plus-function or step-plus-function limitations will only be employed where for a specific claim limitation all of the following conditions are present in that limitation: a) “means for” or “step for” is expressly recited; b) a corresponding function is expressly recited; and c) structure, material or acts that support that structure are not recited. In this disclosure and during the prosecution of this application, the terminology “present invention” or “invention” may be used as a reference to one or more aspect within the present disclosure. The language of the present invention or inventions should not be improperly interpreted as an identification of criticality, should not be improperly interpreted as applying across all aspects or embodiments (i.e., it should be understood that the present invention has a number of aspects and embodiments), and should not be improperly interpreted as limiting the scope of the application or claims. In this disclosure and during the prosecution of this application, the terminology “embodiment” can be used to describe any aspect, feature, process or step, any combination thereof, and/or any portion thereof, etc. In some examples, various embodiments may include overlapping features. In this disclosure, the following abbreviated terminology may be employed: “e.g.” which means “for example.”