Patent Publication Number: US-2019192189-A1

Title: Bone Compression and Fixation Devices

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/417,985 filed Nov. 30, 2010 entitled “Compression Screw” and U.S. Provisional Patent Application No. 61/417,981 filed Nov. 30, 2010 entitled “Flexible to Rigid Bone Fixation Device”, both of which are incorporated by reference herein in their entirety. U.S. Provisional Patent Application No. 61/415,953 filed Nov. 22, 2010 entitled “Compression Wire” is also incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to bone compression and fixation devices and in some particular embodiments, orthopedic devices for joining together in compression two or more pieces of a fractured bone for optimum healing. 
     BRIEF SUMMARY OF THE INVENTION 
     In one embodiment there is a bone screw for drawing first and second bone fragments together comprising a shaft having a distal section and a proximal section, the distal section having a first external male screw thread and a minor diameter, the proximal section having a second external male screw thread, a major diameter of the distal section being larger than a major diameter of the proximal section; and a sleeve having an internal female screw thread configured to mate with the second male screw thread, a distal portion of the sleeve having an outer diameter, the outer diameter being equal to or smaller than the minor diameter of the distal section of the shaft. 
     In one embodiment, the sleeve is configured to receive a tool to rotate the shaft and sleeve together when the shaft is driven into a first bone fragment or rotate the sleeve relative to the shaft to draw a second bone fragment toward the first bone fragment. In one embodiment, a pitch of the first external male screw thread is larger than a pitch of the second external male screw thread. In one embodiment, the distal portion of the sleeve is tapered. In one embodiment, the sleeve includes two or more external longitudinally extending slots configured to engage a tool. 
     In one embodiment, the distal portion of the sleeve is smooth. In one embodiment, the shaft is cannulated. In one embodiment, the shaft includes at least one aperture along a length of the shaft in fluid communication with a hollow center of the shaft. In one embodiment, the shaft includes a plurality of apertures along a length of the shaft, the plurality of apertures being in fluid communication with one another. 
     In another embodiment, there is a bone screw system for drawing first and second bone fragments together, comprising: a bone screw including: a shaft having a distal section and a proximal section, the distal section having a first external male screw thread, the proximal section having a second external male screw thread, a major diameter of the distal section being larger than a major diameter of the proximal section; and a sleeve having an internal female screw thread engageable with the second male screw thread, the sleeve being configured to receive a first tool for rotating the shaft and sleeve together and a second tool for rotating the sleeve relative to the shaft; a tool including: a first tool portion configured to rotate the sleeve relative to the shaft; and a second tool portion configured to rotate the shaft and the sleeve together. 
     In one embodiment, the second tool portion includes a threaded distal end that is engageable with the internal female screw thread and abuts the proximal section. In one embodiment, the second tool portion extends through the first tool portion when rotating the shaft and sleeve together and the second tool portion is withdrawn from the first tool portion when rotating the sleeve relative to the shaft. 
     In another embodiment, there is a wire device for drawing first and second bone fragments together, comprising: a wire having an external male thread; and a sleeve having an internal female thread configured to mate with the external male thread. In one embodiment, the sleeve is configured to slide over the external male thread in a distal direction without rotating the sleeve relative to the wire. In one embodiment, the sleeve includes two or more axially extending slots to form two or more phalanges. In one embodiment, the wire includes a distal section and a proximal section, the distal section having a first external male screw thread, the proximal section having a second external male screw thread, a major diameter of the distal section being larger than a major diameter of the proximal section. 
     In one embodiment, a pitch of the first external male screw thread is larger than a pitch of the second external male crew thread. In one embodiment, the sleeve includes two or more radially extending projections. In one embodiment, a distal portion of the sleeve has a diameter equal to or smaller than a minor diameter of the wire. In one embodiment, the sleeve is tapered. 
     In another embodiment there is a method for drawing first and second bone fragments together, comprising: screwing a wire having an external male thread into a first bone fragment; sliding a sleeve having an internal female thread configured to mate with the external male thread along the wire without rotating the sleeve relative to the wire to abut a second bone fragment; rotating the sleeve relative to the wire to draw the second bone fragment toward the first bone fragment, a proximal portion of the wire extending proximally from the second bone fragment and the sleeve; and cutting and removing the proximal portion of the wire from the remainder of the wire. 
     In another embodiment there is a bone fixation device comprising: a distal end configured to attached to a first bone section and a proximal end configured to attached to a second bone section, a flexible body secured to the distal end and movably attached to the proximal end; and a plurality of cannulated rigid segments surrounding the body, wherein the segments are spaced and allow the body to flex when the body is in a first position relative to the proximal end and wherein the segments abut and prevent the body from being flexed when the plate is moved from the first position to a second position relative to the proximal end. 
     In one embodiment, the body is flexible along a first plane and rigid along a second plane, the first plane being orthogonal to the second plane. In one embodiment, the body has a rectangular cross section. In one embodiment, the body is threadably attached to a radially rotatable, axially fixed sleeve in the proximal end. In one embodiment, each segment includes a projection that mates with an indent of an adjacent segment in the second position. In one embodiment, the segments are cylindrically shaped. In one embodiment, the body includes at least one aperture and the proximal end includes at least one aperture, the at least one aperture of the body aligning with the at least one aperture of the proximal end in the second position. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The foregoing summary, as well as the following detailed description of embodiments of the bone compression and fixation devices, will be better understood when read in conjunction with the appended drawings of exemplary embodiments. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. 
       In the drawings: 
         FIG. 1A  is a perspective view of a bone screw device in accordance with an exemplary embodiment of the present invention; 
         FIG. 1B  is cross sectional perspective view of the bone screw device shown in  FIG. 1A ; 
         FIG. 1C  is cross sectional side view of the bone screw device shown in  FIG. 1A ; 
         FIG. 2A  is a perspective view of a tool for implanting a bone screw device in accordance with an exemplary embodiment of the present invention; 
         FIG. 2B  is a perspective view of the tool shown in  FIG. 2A ; 
         FIG. 2C  is a perspective view of a distal end of a sleeve of the tool shown in  FIG. 2A ; 
         FIG. 2D  is a cross sectional perspective view of the tool shown in  FIG. 2A ; 
         FIG. 3A  is a side elevational view of the bone screw device shown in  FIG. 1A  with a tool in accordance with an exemplary embodiment of the present invention; 
         FIG. 3B  is a cross sectional view of the bone screw device and tool shown in  FIG. 3A ; 
         FIG. 3C  is an enlarged cross section view of the bone screw device and tool shown in  FIG. 3B ; 
         FIG. 4A  is a perspective view of the bone screw device and tool shown in  FIG. 2A  in an initially engaged position; 
         FIG. 4B  is a cross sectional perspective view of the bone screw device and tool shown in  FIG. 4A ; 
         FIG. 4C  is a perspective view of the bone screw device and tool shown in  FIG. 4A  in a fully engaged position with lock sleeve over the driver phalanges; 
         FIG. 5A  is a side elevational view of a bone wire device in accordance with an exemplary embodiment of the present invention; 
         FIG. 5B  is an outline of a cross sectional view of the bone wire device shown in  FIG. 5A ; 
         FIG. 6A  is a side elevational view of the bone wire device shown in  FIG. 5A  between first and second bone fragments in an engaged position; 
         FIG. 6B  is a side elevational view of the bone wire device shown in  FIG. 6A  in a compressed position; 
         FIG. 7  is a perspective view of a bone fixation device in accordance with an exemplary embodiment of the present invention shown in a rigid configuration; 
         FIG. 8A  is a perspective view of the bone fixation device shown in  FIG. 7  with the plurality of segments removed; 
         FIG. 8B  is a perspective view of the bone fixation device shown in  FIG. 8A  with a fixation sleeve attached to the proximal end; 
         FIG. 9A  is a cross sectional side view of the bone fixation device shown in  FIG. 7  in a rigid configuration; and 
         FIG. 9B  is a cross sectional side view of the bone fixation device shown in  FIG. 7  in a flexible configuration. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In orthopedic surgery it is common to rejoin broken bones. However, in most situations where cross-fixation of the bone fragments is required, the success of the surgical procedure depends to a large extent on the degree of compression that can be achieved between the bone fragments. More specifically, if the surgeon is unable to bring the bone fragments in close contact with each other, there will exist a space or void into which the bone tissue must grow before the healing process is complete. Thus, the greater the distance between the bone fragments, the slower the healing process. In addition, the healing process can be retarded by any relative movement or shifting of the bone fragments which disturbs the bone tissue that has been laid down. 
     Screws commonly used in fracture fixation are of the lag type, and comprise a threaded leading end and an enlarged head incorporating a means to engage a driving tool at the trailing end. In some situations, the presence of a screw head has a deleterious effect on the outcome of the repair, specifically in cases where the screw must be inserted in or near a skeletal joint or where inadequate bone stock is available to allow countersinking of the screw head. 
     Typical headless compression screws, such as the Hubert Screw which achieves compression by providing two different thread pitches, one pitch toward a distal end an a different pitch toward a proximal end. Apart from being technique sensitive, the ability to compress the bone segments together with a Hubert Screw is based on the number of threads in the head. This allows for limited amount of compression. In some situation, a screw head is desirable but the head contacts the outer surface of the bone at the wrong time to provide the desired compression. 
     In some exemplary embodiments of the present invention, a screw device  10  includes a two piece construction that allows for improved compression between bone fragments. Though screw device  10  may be used with any bone fragments, in some embodiments, screw device  10  is configured for use with the small bones of the hand or foot. Any dimensions specifically mentioned below may be varied in some embodiments to accommodate a particular anatomy. 
     Referring to  FIGS. 1A-1C , screw device  10  includes a shaft  12  and a sleeve  18  that is movable along the shaft  12  to draw together at least two bone fragments. 
     In one embodiment, shaft  12  has a distal section  12   a  and a proximal section  12   b.  In one embodiment, the distal end of distal section  12   a  is pointed. In other embodiments, the distal end of distal section  12   a  is generally blunt. In one embodiment, a major diameter of distal section  12   a  is larger than a major diameter of proximal section  12   b.  In other embodiments, the major diameters of distal section  12   a  and proximal section  12   b  are equal. In one embodiment, the major diameter of distal section  12   a  and proximal section  12   b  are approximately 2.5 mm to approximately 10 mm. In one embodiment, the length of screw device  10  is approximately 10 mm—approximately 60 mm. 
     In one embodiment, distal section  12   a  includes a first external male screw thread  14 . In one embodiment, proximal section  12   b  includes a second external male screw thread  16 . In one embodiment, first external male screw thread  14  is configured to engage cortical and/or cancellous bone. In one embodiment, second external male screw thread  16  are machine threads configured to mate with sleeve  18  and allow the sleeve to travel down the length of shaft  12  as discussed below. In one embodiment, a pitch of first external male screw thread  14  is larger than a pitch of the second external male screw thread  16 . In one embodiment, the pitch of first external male screw thread  14  is approximately 1 mm and the pitch of second external male screw thread  16  is approximately 0.45 mm. In other embodiments, the pitch of first external male screw thread  14  is equal to the pitch of second external male screw thread  16 . 
     In one embodiment, shaft  12  is cannulated. In one embodiment, the entire shaft  12  is cannulated (bore  12   f ) such that both ends of shaft  12  are open and in fluid communication with one another. In one embodiment, shaft  12  is cannulated axially to allow screw device  10  to be driven over a guide wire. In one embodiment, the diameter of bore  12   f  is approximately 2.6 mm. In one embodiment, the diameter of bore  12   f  is approximately 1 mm or larger. In other embodiments, only a portion of shaft  12  is cannulated and/or one or more of the ends are closed. In one embodiment, shaft  12  includes at least one aperture  12   c  along a length of shaft  12  and in fluid communication with a hollow center of shaft  12 . In one embodiment, shaft  12  includes a plurality of apertures  12   c  along a length of shaft  12 , apertures  12   c  are in fluid communication with one another. In one embodiment, apertures  12   c  align with a corresponding diametrically opposed aperture  12   c.  In one embodiment, apertures  12   c  have a corresponding opposed aperture  12   c  on the opposite site of shaft  12  that is at an angle relative to the longitudinal axis of shaft  12 . In other embodiments, apertures  12   c  do not have a corresponding aperture  12   c  on the opposite side of shaft  12 . In one embodiment, apertures  12   c  are approximately 0.2 mm in diameter. In other embodiments, apertures  12   c  are larger than 0.2 mm in diameter. In one embodiment, apertures  12   c  are circular. In other embodiments, apertures  12   c  are any shape including triangular, rectangular or oval. 
     In one embodiment, apertures  12   c  and/or cannulated shaft  12  allow for fluid such as blood to vascularize the fracture site and aid in fracture healing. In one embodiment, apertures  12   c  and/or cannulated shaft  12  allow for fluid to exit the body while implanting screw device  10  rather than cause a buildup of pressure within the body. In other embodiments, apertures  12   c  and cannulated shaft  12  may be used to deliver a drug such as gentamicin or a bone graft through or from within screw  12  to the fracture site. 
     In one embodiment, the proximal end of shaft  12  includes a keyed surface  12   d.  In one embodiment, keyed surface  12   d  is a slot. In one embodiment, keyed surface  12   d  is configured to engage a driver tool to provide counter torque or to drive shaft  12  directly if necessary. 
     In one embodiment, sleeve  18  threadably mates with proximal section  12   b  of shaft  12 . In one embodiment, sleeve  18  includes an internal female screw thread  20  that is configured to mate with second external male screw thread  16 . In one embodiment, the length of sleeve  18  is approximately 7 mm. 
     In one embodiment, sleeve  18  is tapered toward distal section  12   a.  In one embodiment at least a portion of sleeve  18  is frustoconical in shape. In one embodiment, an outer surface of at least a distal portion of sleeve  18  is smooth. In one embodiment, the outer surface of at least a distal portion of sleeve  18  is void of threads. In one embodiment, the outer diameter of at least a portion of the distal portion of sleeve  18  is approximately equal to or smaller than the minor diameter of distal section  12   a  of shaft  12 . In one embodiment, the diameter of sleeve  18  is greater than the minor diameter of distal section  12   a  of shaft  12  and tapers toward distal end  18   a  to a diameter less than the minor diameter of distal section  12   a  of shaft  12 . In one embodiment, providing a tapered sleeve  18  allows for a desired compression between bone fragments without having to screw sleeve  18  into the bone. In one embodiment, shaft  12  and sleeve  18  are configured to allow the distal end of sleeve  18  to abut against the beginning of first external male screw thread  14 . 
     In one embodiment, sleeve  18  includes two or more external longitudinally extending slots  18   c  that are configured to engage a tool as discussed below. In other embodiments, sleeve  18  may include an internal hex, slot, projection, Torx or Phillips shape for receiving the tool. In one embodiment, sleeve  18  includes two or more radially extending projections  18   d.  In one embodiment, radially extending projections  18   d  act as a screw head to engage a bone surface. In other embodiments, sleeve  18  does not include radially extending projections  18   d  and is instead configured to be completely countersunk into the bone and generally flush with the outer bone surface. In one embodiment, projections  18   d  are countersunk into the bone. In one embodiment, sleeve  18  remains at the outer surface of the bone. 
     In one embodiment, screw device  10  is comprised of biocompatible materials. In one embodiment, screw device  10  is comprised of biocompatible metal, such as stainless steel or titanium. In one embodiment, screw device  10  is comprised of biocompatible polymer such as PEEK. 
     Referring to  FIGS. 2A-2D , a tool  22  may be used to implant screw device  10 . In one embodiment, tool  22  is an at least two piece design that has an outer drive sleeve  24   a  and an inner drive shaft  26   b.  In one embodiment, tool  22  is a three piece design with outer drive sleeve  24   a  including a lock sleeve  28 . In one embodiment, inner drive shaft  26   b  mates with internal female screw thread  20  of sleeve  18  while drive sleeve  24   a  engages slots  18   d  of sleeve  18 . 
     In one embodiment, tool  22  includes a first tool portion  24  and a second tool portion  26 . In one embodiment, first tool portion  24  is configured to rotate sleeve  18  relative to shaft  12 . In one embodiment, second tool portion  26  is configured to rotate the shaft and sleeve together. 
     Referring to  FIGS. 3A-3C , in one embodiment, first tool portion  22  includes an enlarged handle  24   b.  In one embodiment, handle  24  is configured to be griped by a user&#39;s hand to torque first tool portion  24 . In one embodiment, driver sleeve  24   a  extends axially from handle  24   b.  In one embodiment, second tool portion  22  includes an enlarged handle  26   d.  In one embodiment, drive shaft  26   b  extends axailly from handle  26   d.  In one embodiment, handle  26   d  abuts handle  24   b  when drive shaft  26   b  extends through drive sleeve  24   a.  In one embodiment, handle  26   d  is releasably coupled to handle  24   b  to prevent drive shaft  26   b  from rotating relative to drive sleeve  24   a  during use. In one embodiment, second tool portion  26  includes an open bore  26   c.  In one embodiment, the diameter of bore  26   c  is equal to the diameter of bore  12   f.  In one embodiment, bore  26   c  allows for a guide wire extending from screw device  10  to extend through tool  22 . 
     In one embodiment, drive sleeve  24   a  includes two or more axially extending projections corresponding to slots  18   d  of sleeve  18 . In one embodiment, the axially extending projections are circumferentially spaced from one another such that this is an open space between each projection to form phalanges. In other embodiments, the projections of the drive sleeve  24   a  do not have an open space in between but instead project radially inward from the surrounding drive sleeve  24   a.  In one embodiment, drive shaft includes an external male screw thread  12   c.  In other embodiments, drive shaft  26   b  includes a mating surface other than a screw thread such as a hex, star, or Phillips. In one embodiment, the distal end of drive shaft  26   b  extends axially further than the distal end of drive sleeve  24   a  in a first position and the distal end of drive sleeve  24   a  extends axially further than the distal end of drive shaft  26   b  in a second position. 
     Referring to  FIGS. 4A-4C , in one embodiment, a lock sleeve  28  is provided on the outer surface of drive sleeve  24   a.  In one embodiment, lock sleeve  28  is used to ensure that the distal phalanges of drive sleeve  24   a  do not flex radially and out of engagement with sleeve  18 . In one embodiment, once drive shaft  26   b  and drive sleeve  24   a  are coupled to sleeve  18  in an initially engaged position ( FIG. 4A ), lock sleeve  28  is at least partially slid over distal phalanges of drive sleeve  24   a  in a fully engaged position ( FIG. 4C ). 
     Referring to  FIGS. 3A-4C , in an exemplary method of use of screw device  10 , shaft  12  and sleeve  18  are inserted into the fractured bone together using tool  22  coupled to sleeve  18 . In one embodiment, the distal tip of shaft  12  engages and is screwed into the distal fragment of the fractured bone. In one embodiment, both first tool portion  24  and second tool portion  26  are rotated together such that shaft  12  is rotated without advancing sleeve  18  relative to shaft  12 . In one embodiment, once the shaft  12  is in place, second tool portion  26  is unscrewed from sleeve  18  and at least partially withdrawn from first tool portion  24 . First tool portion  24  including drive sleeve  24   a  then rotates sleeve  18  relative to shaft  12  advancing sleeve  18  distally axially along shaft  12 . The outer surface of sleeve  18  contacts a proximal bone fragment and as sleeve  18  is advanced along shaft  12 , screw device  10  draws the distal and proximal bone fragments together. 
     In one embodiment, sleeve  18  enters the proximal bone fragment and at least partially countersinks itself In one embodiment, sleeve  18  is completely countersunk such that the proximal end of sleeve  18  is flush to the outer surface of the proximal bone fragment. In one embodiment, first tool portion  24  includes a torque gauge or a safety feature to prevent over compression of the bone fragments. In one embodiment, the excess portion of shaft  12 , extending proximally from sleeve  18  after screw device  10  has been compressed, is cut or broken off from the remainder of shaft  12 . In one embodiment, shaft  12  includes one or more points of weakness such as a score line or divot to aid in breaking off the excess portion of shaft  12 . In one embodiment, the proximal end of shaft  12  is generally flush with the proximal end  18   b  of sleeve  18  after removing the excess portion of shaft  12 . 
     In procedures requiring a smaller diameter implant or other procedures, a wire rather than a screw may be preferred. Typically Kirschner wires or K-wires are used to keep bone fragments in place in certain instances. However, K-wires have a single diameter and do not allow for effective compression. 
     Referring to  FIGS. 5A-5B , a wire device  30  includes a threaded wire  32  and a sleeve  38 . In one embodiment, a distal tip of wire  32  engages the bone shaft and sleeve  38  is secured to wire  32  to compress one or more bone fragments together. The remaining wire may then be cut or broken off. 
     In one embodiment, a distal section  32   a  of wire  32  includes an external male screw thread  34 . In one embodiment, the major diameter of wire  32  is approximately 1.3 mm. In one embodiment, external male screw thread  34  is a double lead pitch. In one embodiment, a proximal section  32   b  of wire  32  includes an external male screw thread  36 . In one embodiment, the major diameter of distal section  32   a  is larger than the major diameter of proximal section  32   b.  In other embodiments, the major diameters of the distal section  32   a  and proximal section  32   b  are equal. In one embodiment, the pitch of external male screw thread  34  is larger than the pitch of external male screw thread  36 . In other embodiments, the pitches of the external male screw threads  34 ,  36  are equal. In some embodiments, wire  32  includes a plurality of ribs in addition to or in place of external male screw thread  36 . In one embodiment, the distal end of wire  32  is pointed. In other embodiments, distal end of wire  32  is blunt. 
     In one embodiment, sleeve  38  includes an internal female screw thread  38   e  configured to mate with the external male screw thread  36 . In one embodiment, sleeve  38  is configured to slide over the external male screw thread  36  in a distal direction without rotating sleeve  38  relative to wire  32  but not slide in the proximal direction similar to a zip or cable tie. In one embodiment, sleeve  38  includes two or more axially extending slots  38   d  to form two or more flexible phalanges  38   g.  In one embodiment, internal female screw thread  38   e  is only on the flexible portion of sleeve  38 . In one embodiment, a proximal section  38   f  of sleeve  38  is smooth and does not contain threads. In one embodiment, a distal portion of sleeve  38  has a diameter equal to or small than the major diameter of distal section  32 . In one embodiment, distal end  38   a  of sleeve  38  is tapered. In one embodiment, the outer diameter of at least a portion of the distal portion of sleeve  38  is approximately equal to or smaller than the minor diameter of distal section  32   a  of wire  32 . In one embodiment, the tapered section of sleeve  38  is greater than the minor diameter of distal section  32   a  of wire  32  and tapers toward distal end to a diameter less than the minor diameter of distal section  32   a  of wire  32 . In one embodiment, wire  32  and sleeve  38  are configured to allow the distal end of sleeve  38  to abut against the beginning of external male screw thread  34 . 
     In one embodiment, sleeve  38  includes two or more radially extending projections  38   c.  In one embodiment, projections  38   c  are toward the proximal end  38   b  of sleeve  38 . In one embodiment, projections  38   c  allow for a tool or hand to more easily grasp and rotate sleeve  38  relative to wire  32 . In one embodiment projection  38   c  act as a screw head and remain on the outer surface of the bone. 
     Referring to  FIGS. 6A and 6B , in an exemplary method of use, wire device  30  is inserted between at least a proximal bone fragment  40  and a distal bone fragment  42 . In one embodiment, wire  32  is inserted using a wire driver. In one embodiment, wire  32  is screwed into distal bone fragment  42 . In one embodiment, sleeve  38  is slid along wire  32  without rotating sleeve  38  relative to wire  32  until sleeve  38  abuts the outer surface of proximal bone fragment  40 . In other embodiments, sleeve  38  is screwed to advance sleeve  38  along wire  32 . In embodiments where proximal section  32   b  of wire  32  includes threads, once sleeve  38  abuts bone, sleeve  38  is rotated relative to wire  32  to draw distal bone fragment  42  and proximal bone fragment  40  together. In one embodiment, sleeve  38  is countersunk into proximal bone fragment  40 . In other embodiments, projections  38   c  acts as a screw head to prevent sleeve  38  from completely countersinking. In one embodiment, once sleeve  38  is move to the desired position along wire  32 , the remaining wire  32   c  proximate to sleeve  38  is cut or bent off from the remainder of wire  32 . 
     In one embodiment, wire device  30  is comprised of biocompatible materials. In one embodiment, wire device  30  is comprised of biocompatible metal such as stainless steel or titanium. In one embodiment, wire device  30  is comprised of biocompatible polymer such as PEEK. 
     In certain bone fractures there is a need for a rod that will be flexible on insertion but can be converted to a rigid implant. 
     Referring to  FIGS. 7-9B , a bone fixation device  50  is initially flexible and can be stiffened after implanting into the body. Bone fixation device  50  may be sized and configured to secure any two bones or bone fragments together including long bones having an intramedullary canal such as the humerus, femur, tibia, radius or ulna. In one embodiment, bone fixation device  50  is a humeral nail for implanting into the humerus. 
     Referring to  FIG. 7 , bone fixation device  50  includes a plurality of rigid segments  54  that are moveable relative to one another in a flexible or implanting configuration ( FIG. 9B ) and are fixed relative to one another in a rigid or implanted configuration ( FIG. 9A ). In some embodiments, rigid means substantially unbending or stiff. In some embodiments, bone fixation device  50  and/or rigid segments  54  may bend slightly under extreme forces or due to material strength or machined tolerances. However, in some embodiments, bone fixation device is substantially stiffer in the implanted configuration than in the implanting configuration such that bone fixation device  50  can bend during implanting and be stiffened to provide support between bones or bone fragments once implanted. 
     In one embodiment, a distal end  50   a  is configured to be coupled to a first bone section and a proximal end  50   b  is configured to be coupled to a second bone section once implanted. In one embodiment, distal end  50   a  is generally pointed. In one embodiment, proximal end  50   b  is bent and the remainder of bone fixation device  50  is straight once implanted. In other embodiments, bone fixation device  50  is curved or any other shape in the rigid position to fit to a desired anatomy. In one embodiment, a substantial length of bone fixation device  50  is flexible in the implanting configuration. In other embodiments, only a portion of bone fixation device  50  is flexible in the implanting configuration. In one embodiment, the entire bone fixation device  50  is rigid in the implanted configuration. In other embodiments, at least a portion of bone fixation device  50  remains flexible in the implanted configuration. In one embodiment, bone fixation device  50  is comprised of biocompatible materials. In one embodiment, bone fixation device  50  is comprised of biocompatible metal. 
     In one embodiment, distal end  50   a  includes one or more apertures  50   c  configured to receive a fastener such as a pin or screw. In one embodiment, apertures  50   c  are perpendicular to one another. In one embodiment, proximal end  50   b  includes one or more apertures  50   d.  In one embodiment, apertures  50   d  are perpendicular to one another. In one embodiment, apertures  50   c,    50   d  are approximately 2.4 mm to approximately 3.5 mm in diameter. 
     Referring to  FIGS. 8A and 8B , which shows bone fixation device  50  with rigid segments  54  removed, bone fixation device includes a flexible body  52  secured to distal end  50   a  and movably attached to the proximal end  50   b  (see  FIGS. 9A and 9B ). In one embodiment, body  52  is flexible along a first plane and rigid along a second plane orthogonal to the second plane. In one embodiment, body  52  is rectangular cross section. In one embodiment, body  52  is wider than it is thick. In one embodiment, body  52  is machined out of a single block of material. In one embodiment, body  52  is comprised of multiple pieces joined together with pins, threads or other methods. 
     In one embodiment, body  52  is threadably attached to a radially rotatable, axially fixed sleeve  56  in the proximal end  50   b.  In one embodiment, sleeve  56  is cylindrical in shape and includes a groove  56   b  that mates with a corresponding projection or pins in proximal end  50   b  or vice versa. Sleeve  56  is configured to rotate relative to proximal end  50   b  and groove  56   b  and the corresponding projection from proximal end  50   b  prevents sleeve  56  from moving axially relative to proximal end  50   b.  In one embodiment, body  52  includes an external male screw thread  52   c.  In one embodiment, sleeve  56  includes an internal female screw thread  56   b  configured to mate with male screw thread  52   c.  In other embodiments, the threads  52   c,    56   b  of body  52  and sleeve  56  are reversed. In one embodiment, a proximal end of sleeve  56  is configured to mate with a tool to rotate sleeve  56  relative to proximal end  50   b.  The proximal end of sleeve  56  may include any mating feature such as hex, slot, projection, Torx or Phillips shape for receiving the tool. 
     In one embodiment, body  52  includes at least one aperture  52   d.  In one embodiment, at least one aperture  52   d  of body  52  aligns with at least one aperture  50   d  of proximal end  50   b  in the rigid configuration. In one embodiment, body  52  includes a slot  52   e  configured to receive a projection or pin  50   e  (see  FIGS. 9A and 9B ). In one embodiment, pin  50   e  prevents proximal end from rotating relative to proximal end  50   b.    
     Referring to  FIGS. 9A and 9B , in one embodiment, rigid segments  54  are cannulated rigid segments that surround body  52 . Rigid segments  54  may have any cross sectional shape such as rectangular, triangular or oval. In one embodiment, rigid segments  54  are cylinders. In one embodiment, there is a space between the inner surface of the rigid segments  54  and at least a portion of body  52 . In one embodiment, any space between the inner surface of the rigid segments  54  and body  52  is filled with a material and/or includes a drug. 
     In one embodiment, rigid segments  54  have a contiguous outer surface. In one embodiment, rigid segments  54  include one or more apertures. In one embodiment, each rigid segment  54  includes at least one projection that mates with an indent of an adjacent segment. In one embodiment, each rigid segment includes an axially extending mating feature to prevent rigid segments  54  and proximal and distal ends  50   a,    50   b  from rotating relative to one another in the rigid position. 
     In one embodiment, body  52  has a first length measured between distal and proximal ends  50   a,    50   b  in the flexible configuration and a second length measured between distal and proximal ends  50   a,    50   b  in the rigid configuration, the first length being greater than the second length. In one embodiment, rigid segments  54  are spaced in a flexible configuration to allow body  52  to flex. In one embodiment, rotating sleeve  56  draws body  52  axially relative to proximal end  50   b  causing distal end  50   a  to be closer to proximal end  50   b  and each of the rigid segments  54  to collapse and abut one another to form a rigid device. 
     It will be appreciated by those skilled in the art that changes could be made to the exemplary embodiments shown and described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the exemplary embodiments shown and described, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the claims. For example, specific features of the exemplary embodiments may or may not be part of the claimed invention and features of the disclosed embodiments may be combined. Unless specifically set forth herein, the terms “a”, “an” and “the” are not limited to one element but instead should be read as meaning “at least one”. 
     It is to be understood that at least some of the figures and descriptions of the invention have been simplified to focus on elements that are relevant for a clear understanding of the invention, while eliminating, for purposes of clarity, other elements that those of ordinary skill in the art will appreciate may also comprise a portion of the invention. However, because such elements are well known in the art, and because they do not necessarily facilitate a better understanding of the invention, a description of such elements is not provided herein. 
     Further, to the extent that the method does not rely on the particular order of steps set forth herein, the particular order of the steps should not be construed as limitation on the claims. The claims directed to the method of the present invention should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the steps may be varied and still remain within the spirit and scope of the present invention.