Abstract:
The invention provides a bolt apparatus for fixation of bones, the bolt apparatus including an expandable section being having respective ends, the expandable section being operable between a contracted position and an expanded position; and expanding means in operable association with the expandable section, to displace the expandable section between the contracted position and the expanded position by simultaneously applying force to the respective ends of the expandable section, such that each of the respective ends of the expandable section are advanced toward the opposing respective end. The invention also provides a method for fixation of bones. The method includes the steps of reducing the fracture; providing a channel across the fracture; inserting a bolt apparatus of the invention; and fixing the bolt apparatus in the channel. Preferably, the method also includes providing a plate in operative association with the bolt.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U. S. National Stage of International Application No. PCT/IE2008/000073, filed Jul. 3, 2008, which claims the benefit of Irish Patent Application Nos. S2007/0480, filed Jul. 3, 2007, and S2008/0120, filed Feb. 15, 2008, all of which are hereby incorporated by reference to the extent not inconsistent with the disclosure herewith. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     THE NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT 
     Not applicable. 
     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a bolt apparatus. In particular, the apparatus finds utility as a bolt apparatus for fixation of bones such as fractures of the femur, although it may be used in any suitable bone. By “bolt apparatus” is meant an apparatus that bolts or fixes objects together, which apparatus can be used for fixation of bones. 
     Bone fixation devices are well known and they find particular utility in the field of orthopaedic surgery, where they are used to fix a bone, which has sustained a fracture, across a fracture site. Generally, the type of fracture determines the type of surgery. 
     Patients with femoral neck fractures are treated with pinning or hip arthroplasty, depending on the age of the patient and the presence and degree of displacement. Patients with intertrochanteric fractures are treated with a sliding hip screw or an intramedullary hip screw, depending on the stability and location of the fracture. 
     If the fracture is stable, a sliding hip screw coupled to a side plate that is screwed onto the femoral shaft is used. The screw provides proximal fragment fixation. It is set inside a telescoping barrel that allows impaction of the bone, which promotes fracture union. A lateral buttress must be intact to stop excessive sliding of the screw. 
     When the direction of a fracture is parallel to the femoral neck, the fracture can be extremely unstable. This fracture type is called the reverse oblique pattern. A high rate of failure occurs if the fracture is treated with a sliding hip screw and a side plate. Because of the angle of the fracture, there is no bone laterally to stop the screw from sliding. 
     For unstable intertrochanteric fractures, including those of the reverse oblique pattern and those with subtrochanteric extension, an intramedullary hip screw is often indicated. This device combines a sliding hip screw with an intramedullary nail. Intramedullary hip screws can be placed through small incisions, and blood loss may be less than with a hip screw and side plate. The nail acts as a metal buttress to prevent sliding and provides better fixation in unstable fracture patterns. 
     Failure mechanisms of a hip screw include non-union, screw cut-out, nail breakage, malunion, and limp. Although sliding of the hip screw allows for bone compression and hopefully healing, it shortens the limb and causes abduction weakness. Most complications are subsequently treated with total hip arthroplasty. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved device for bone fixation, which provides a means for reducing the occurrence of screw cut-out, amongst other failure mechanisms, thereby reducing the necessity of a patient having to undergo total hip arthroplasty. 
     According to a first aspect of the present invention there is provided a bolt apparatus for fixation of bones, the bolt apparatus comprising an expandable section having respective ends, the expandable section being operable between a contracted position and an expanded position; and expanding means in operable association with the expandable section, to displace the expandable section between the contracted position and the expanded position by applying force to the respective ends of the expandable section, such that each of the respective ends of the expandable section are advanced toward the opposing respective end. 
     Optionally, the expanding means displaces the expandable section between the contracted position and the expanded position by simultaneously applying force to the respective ends of the expandable section, such that each of the respective ends of the expandable section are advanced toward the opposing respective end. 
     As used herein, the term “advanced” is intended to mean the positive displacement of an object between a first position and a second position, wherein the first and second positions are different, spaced-apart positions. It is understood that, in the present invention, the first position of each respective end is the position when the expandable section is in the fully expanded position, and the second position of each respective end is the position when the expandable section is in the fully contracted position. Each respective end is displaced by the application of a force to each of the respective ends of the expandable section. Each respective end can optionally be simultaneously displaced by the simultaneous application of a force to each of the respective ends of the expandable section. 
     The present invention finds utility as a bolt apparatus for fixation of bones such as fractures of the femur, although it may be used in any suitable bone. 
     Optionally, the expanding means is in operable association with the expandable section, to displace the expandable section between the contracted position and the expanded position by applying force to the respective ends of the expandable section, such that each of the respective ends of the expandable section are independently advanced toward the opposing respective end. As used herein, the term “independently advanced” is intended to mean the positive and independent displacement of an object between a first position and a second position, wherein the first and second positions are different, spaced-apart positions. Each respective end is displaced by the application of a force to each of the respective ends of the expandable section. Each respective end can be displaced by the independent application of a force to each of the respective ends of the expandable section. 
     Further optionally, the expanding means is in operable association with the expandable section, to displace the expandable section between the contracted position and the expanded position by simultaneously applying force to the respective ends of the expandable section, such that each of the respective ends of the expandable section are independently advanced toward the opposing respective end. Each respective end is displaced by the application of a force to each of the respective ends of the expandable section. Each respective end can be optionally simultaneously displaced by the independent and simultaneous application of a force to each of the respective ends of the expandable section. 
     Preferably, the expanding means comprises a connecting means and at least two bodies mountable to the connecting means. 
     Preferably, the connecting means, for example, a shaft is adapted to allow reciprocal movement of the at least two bodies relative to the connecting means. 
     Preferably, the connecting means is a shaft. 
     Preferably, the at least two bodies are threadably mountable to the connecting means, for example, the shaft. Further preferably, first and second bodies are threadably mountable to the connecting means, for example, the shaft, and arranged for displacement in response to rotation of the connecting means, for example, the shaft to apply mechanical pressure to the respective ends of the expandable section. The connecting means, for example the shaft, can be arranged to simultaneously and independently apply mechanical pressure to the respective ends of the expandable section. The at least two bodies are displaced in response to rotation of the connecting means, for example, the shaft relative to one, both or each of the at least two bodies, or can be displaced by rotation of one, both or each of the at least two bodies relative to the connecting means, for example, the shaft. 
     Preferably, the connecting means, for example, the shaft comprises first and second threaded portions, wherein the threads of the first portion are of reverse orientation to the threads of the second portion. 
     Preferably, each of the first and second threaded portions has first and second terminal ends. Further preferably, the first terminal end corresponds to the first position, and the second terminal end corresponds to the second position, between which an object can be positively displaced. It is understood that, in this case, positive displacement means the reciprocal movement of the object between the first and second terminal ends of each threaded portion. 
     Preferably, the first body is mountable to the first threaded portion of the connecting means, for example, the shaft, and the second body is mountable to the second threaded portion of the connecting means, for example, the shaft. 
     Optionally, the first and second threaded portions are located adjacent one end, for example, a distal end of the connecting means, for example, the shaft. Alternatively, the first and second threaded portions are located adjacent respective opposing ends of the connecting means, for example, the shaft. 
     Preferably, the threaded portions of the connecting means, for example, the shaft are helically threaded portions. 
     Optionally, a proximal end of the connecting means, for example, the shaft is dimensioned and arranged, for example, by way of a transverse cross-section, so as to inhibit the coaxial rotation of the shaft relative to a set screw, once assembled. 
     Optionally, the proximal end of the connecting means, for example, the shaft is dimensioned and arranged, so as to provide means for delivering torque to the connecting means, for example, the shaft. Preferably, the proximal end of the connecting means, for example, the shaft is dimensioned and arranged to receive a torque delivery device such as a screwdriver, or similar device. Alternatively, the proximal end of the connecting means, for example, the shaft is dimensioned and arranged to allow rotation thereof by a hex key, or similar device. However, it will be appreciated that any shape of screwdriver to deliver the required torque may be used. 
     Optionally, at least one projection extends from the outer curved surface of the connecting means, for example, the shaft, to inhibit the coaxial rotation of the connecting means, for example, the shaft relative to a set screw, once assembled. 
     Preferably, each projection extends substantially radially from the curved surface of the connecting means, for example, the shaft. 
     Alternatively, the at least two bodies are arranged for displacement in response to rotation relative to the connecting means, for example, the shaft, by delivering torque to the at least two bodies. Optionally, at least the proximal end of the expanding means is dimensioned and arranged, so as to provide means for delivering torque to the at least two bodies. 
     Optionally, one, both, or each of the at least two bodies is engagable with at least one of the respective ends of the expandable section. Further optionally, one, both, or each of the at least two bodies is irreversibly engagable with at least one of the respective ends of the expandable section. 
     Optionally, one, both, or each of the at least two bodies is shaped and/or adapted to inhibit the coaxial rotation of the one, both, or each of the at least two bodies relative to the respective end of the expandable section. 
     Preferably, the expandable section is reversibly expandable. More preferably, the section is reversibly expandable under mechanical pressure. 
     Preferably, the expandable section is collapsible along its longitudinal axis. Further preferably, the expandable section is radially inwardly collapsible. 
     Preferably, the expandable section comprises at least two expandable members that extend from the longitudinal axis of the apparatus under mechanical pressure. More preferably, the expandable members extend radially from the longitudinal axis of the apparatus under mechanical pressure. 
     Preferably, each of the expandable members comprises a deformable arm. 
     Preferably, at least one point of folding is provided along each deformable arm. 
     Preferably, the or each point of folding comprises a point of weakness, a hinge mechanism, or any such mechanism that will facilitate the folding of the deformable arm at a desired location. 
     Optionally, the bolt apparatus further comprises a sleeve. 
     Preferably, the sleeve comprises a tube that is generally cylindrical in shape and is open at least at one end. 
     Preferably, the connecting means, for example, the shaft is locatable within the sleeve and rotatable coaxially therein. 
     Preferably, an outer surface of the sleeve has a transverse cross-section, so as to inhibit the coaxial rotation of the sleeve relative to the external bone with which it is in contact, once in use. 
     Alternatively, at least part of the surface of the sleeve is shaped or adapted, for example, by its transverse cross-section, so as to inhibit the coaxial rotation of the sleeve relative to the external bone with which it is in contact, once in use. 
     Optionally, the outer surface is generally hexagonal in transverse cross-section. This is thought to provide mechanical strength along the longitudinal axis of the outer sleeve. However, it will be seen that any shape that can impart the mechanical strength and restrict the rotation of the outer sleeve relative to the external bone with which it is in contact, may be used. 
     Alternatively or additionally, at least part of the surface of the sleeve is shaped and dimensioned to reversibly engage with a barrel of a plate. The plate can be a plate commonly used in the art, and will be selected by one skilled in the art. Preferably, at least part of the outer surface of the sleeve is planar in shape, for example, has a generally circular transverse cross-section but for a planar section, wherein the cross-section of the planar section is a rectilinear line. 
     Optionally, at least two apertures are provided in the sleeve. 
     Further optionally, the apertures are generally rectangular in shape and are substantially parallel to the longitudinal axis of the sleeve. 
     Preferably, the apertures run a pre-determined distance along the length of the sleeve. More preferably, the apertures run from adjacent an open distal end of the sleeve to approximately half the length of the sleeve. Alternatively, the apertures run from adjacent an open distal end of the up to approximately one third the length of the sleeve. 
     Alternatively, each of the expandable members is defined by the apertures running a pre-determined distance along the length of the sleeve. 
     Optionally, the expandable section and the sleeve are separate elements that are coterminous with each other. 
     Alternatively, the expandable section is integral to the outer sleeve. 
     Optionally, one, both, or each of the at least two bodies is engagable with at least part of the sleeve. Further optionally, one, both, or each of the at least two bodies is irreversibly engagable with at least part of the sleeve. 
     Optionally, one, both, or each of the at least two bodies is shaped and/or adapted to inhibit the coaxial rotation of the one, both, or each of the at least two bodies relative to the at least part of the sleeve. 
     Alternatively, at least one of the at least two (further optionally one or both) bodies defines a portion of the expandable section. Further optionally, at least one of the at least two (further optionally one or both) bodies comprises a screw thread located on a portion of the expandable section. Alternatively, at least one of the at least two (further optionally one or both) bodies defines a portion of the sleeve. 
     Optionally, at least one of the at least two (further optionally one or both) bodies comprises a screw thread located on at least part of the inner surface of the sleeve. 
     Preferably, a cap is provided to stop any component of the apparatus from advancing beyond the terminal end, preferably the distal terminal end, of the sleeve, when in use. 
     Preferably, the bolt apparatus is formed of a material that is suitable for sterilisation, so as to be provided in a sterile packaged state for use. 
     Preferably, the material is autoclavable. 
     Preferably the material is surgical stainless steel, but it will be seen that any material that is suitable for sterilisation and can impart the required mechanical strength may be used. 
     For the purposes of the present specification, a user is a person who will undertake the operation of the device during routine use. Usually, this will be a medical professional, where routine use includes fixation of a bone of a patient. When in use, the invention is oriented so as to have a proximal end and a distal end relative to said user. 
     A patient is defined as a person on whom the device will be used during routine operation. 
     According to a second aspect of the present invention, there is provided a method for fixation of bones, the method comprising the steps of reducing the fracture; providing a channel across the fracture; inserting a bolt apparatus according to the first aspect of the invention in the channel; and fixing the bolt apparatus in the channel. 
     Preferably, the fixing step comprises displacing the expandable section toward the expanded position by applying force to the respective ends of the expandable section, such that each of the respective ends of the expandable section are advanced toward the opposing respective end. 
     Preferably, the method comprises providing a plate in operative association with the bolt. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEW OF THE DRAWINGS 
       Three embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is an exploded perspective view of a bolt apparatus according to a first embodiment of a first aspect of the present invention; 
         FIG. 2  is a perspective view of a first mountable body of an expanding means of the bolt apparatus of  FIG. 1 ; 
         FIG. 3A  is a side view of an expandable section of the bolt apparatus of  FIG. 1 ; 
         FIG. 3B  is a perspective view of the expandable section of  FIG. 3A ; 
         FIG. 4  is a perspective view of a set screw of the bolt apparatus of  FIG. 1 ; 
         FIG. 5  is a perspective view of a sleeve of a bolt apparatus according to a second embodiment of a first aspect of the present invention; 
         FIG. 6  is a distal end view at a slight angle from the longitudinal axis (thus, at a slight perspective) of the sleeve of  FIG. 5 ; 
         FIGS. 7A-F  are schematic diagrams illustrating at least some of the steps involved in the use of a bolt apparatus according to a second embodiment of a second aspect of the present invention; 
         FIG. 8  is an exploded perspective view of a bolt apparatus according to a third embodiment of a first aspect of the present invention; 
         FIG. 9  is a perspective view of a connecting means of the bolt apparatus of  FIG. 8 ; 
         FIG. 10A  is a plan view of a sleeve of the bolt apparatus of  FIG. 8 ; 
         FIG. 10B  is a side view of the sleeve of  FIG. 10A ; 
         FIG. 11A  is a vertical sectional view of a first mountable body of an expanding means of the bolt apparatus of  FIG. 8 ; 
         FIG. 11B  is a perspective view of the first mountable body of an expanding means of  FIG. 11A ; 
         FIG. 12A  is a vertical sectional view of a cap of the bolt apparatus of  FIG. 8 ; and  FIG. 12B  is a perspective view of the cap of  FIG. 12A . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the drawings, similar reference numerals will be used to indicate like parts. 
     Referring now to  FIG. 1  of the drawings, there is shown a bolt apparatus  10  according to a first embodiment of a first aspect of the invention. The bolt apparatus  10  comprises a connecting means, which is herein defined by a shaft  12 ; a sleeve  18 ; two mountable bodies, one proximal  22  and one distal  26 ; an expandable section  30 ; a cap  34 ; and two set screws, one proximal  36 ′ and one distal  36 . 
     The shaft  12  comprises an elongate member, which is generally cylindrical in shape. Two distinct helical screw threaded portions  14 ,  14 ′ are provided adjacent the distal end of the shaft  12 , wherein the relative orientation of each screw thread  14 ,  14 ′ is opposite in direction to that of the other. The proximal end  16  of the shaft  12  is generally hexagonal in transverse cross-section. 
     The sleeve  18  comprises a tube, which is generally cylindrical in shape and is open at each end. The outer surface of the sleeve  18  is generally hexagonal in transverse cross-section, and the inner surface of the sleeve  18  is generally circular in transverse cross-section. The internal diameter of the sleeve  18  is generally of similar length to the external diameter of the shaft  12 , whereby the shaft  12  can be located longitudinally and rotated coaxially within the sleeve  18 . 
     A helical screw thread  21  is provided along a limited length of the inner surface of the sleeve  18 . A generally rectangular aperture  20  is provided on each face of the outer surface of the sleeve  18 , each of which apertures  20  extend along the longitudinal axis from the distal end to approximately half the length of the sleeve  18 . 
     Two mountable bodies  22 ,  26  are provided, each of which is generally cylindrical in shape and is open at both ends. Each respective mountable body  22 ,  26  is of similar form, but has a helical screw thread that is oriented in the opposite direction relative to the other. 
       FIG. 2  is a perspective view of a first mountable body  22  of the bolt apparatus  10 . A helical screw thread  24  is provided on the inner surface of the first mountable body  22 . The internal diameter of the body  22  is generally of similar length to the external diameter of the shaft  12 , whereby the screw thread  24  of the first mountable body  22  can engage with the screw threaded portion  14  of the shaft  12 . A number of projections  23  are provided, each of which extend radially from the external surface of the mountable body  22 . Each of the projections  23  is of a size and location so as to locate in each of the apertures  20  of the sleeve  18 . A helical screw thread  28  is similarly provided (not shown in  FIG. 2  but shown in  FIG. 1 ) on the inner surface of the second mountable body  26 . The internal diameter of the body  26  is generally of similar length to the external diameter of the shaft  12 , whereby the screw thread  28  of the second mountable body  26  can engage with the screw threaded portion  14 ′ of the shaft  12 . A number of projections  23  are provided, each of which extend radially from the external surface of the mountable body  26 . Each of the projections  23  is of a size and location so as to locate in each of the apertures  20  of the sleeve  18 . 
       FIGS. 3A and 3B  are respectively side and perspective views of an expandable section  30  of the bolt apparatus  10 , which comprises a generally cylindrically shaped tube, which is open at both ends. At least two generally rectangular apertures  32  are provided on the curved surface of the expandable section  30 , each of which extends a limited length along the longitudinal axis of the expandable section  30 . The area between the apertures defines deformable arms  33 , the width of which is generally less than that of the apertures  20  of the sleeve  18 , thereby allowing each of the deformable arms  33  of the expandable section  30  to extend radially through each of the apertures  20  of the sleeve  18 , when in an in use, expanded state. A point of weakness  31  is provided at each of the respective ends of each deformable arm  33 , where the deformable arm  33  is attached to the respective ends of the expandable section  30 ; and adjacent the centre point of the length of each deformable arm  33 . 
     A cap  34 ,  FIG. 1 , is provided, wherein said cap is a disc, which is generally concave in transverse cross-section on one face. The cap  34  is provided for protection of the distal end of the bolt apparatus  10  during use, and is attached to the bolt apparatus  10  once assembled. 
       FIG. 4  is a perspective view of a set screw  36  (or  36 ′) of the bolt apparatus  10 , which comprises a generally cylindrically shaped member. A helical screw thread is provided on the outer surface  37  of the set screw  36 . The external diameter of the set screw  36  is generally of similar length to the internal diameter of the unidirectional screw thread  21  of the inner surface of the sleeve  18 , whereby the screw thread on the outer surface  37  of the set screw  36  can engage with the screw thread  21  of the inner surface of the sleeve  18 . 
     An aperture  38 , which is generally hexagonal in transverse cross-section, is provided along the longitudinal axis of the set screw  36 , and extends the full length therethrough. The shape and diameter of the aperture  38  is so that the proximal end  16  of the shaft  12  can locate within the aperture  38  of the set screw  36 . 
     Once assembled, each of the mountable bodies  22 ,  26  is located on one of the screw threaded portions  14 ,  14 ′ of the shaft  12 . Each of the mountable bodies  22 ,  26  is in tandem but opposite orientation relative to the other one, and is located at each respective end of the expandable section  30 . Preferably, each of the mountable bodies  22 ,  26  is attached to each respective end of the expandable section  30  by an adherent means such as an adhesive. 
     The assembly comprising the shaft  12 , mountable bodies  22 ,  26  and the expandable section  30  is located coaxially within the sleeve  18 , wherein each of the projections  23  of each of the mountable bodies  22 ,  26  are substantially colinear with each of the deformable arms  33  of the expandable section  30  and the apertures  20  of the sleeve  18 . 
     The cap  34  is attached to the distal end of the sleeve  18  by an adherent means such as an adhesive. 
     The distal set screw  36  engages with the proximal end  16  of the shaft  12 , thereby providing a means by which to rotate the shaft  12 , when in use. 
     Rotation of the shaft  12  within the sleeve  18  causes each of the mountable bodies  22 ,  26  to respectively advance along the screw threaded portions  14 ,  14 ′, respectively, of the shaft  12 . This applies mechanical pressure to the respective ends of the expandable section  30 , wherein the respective ends are bought sequentially into closer proximity relative to one another, causing the deformable arms  33  of the expandable section  30  to deform at each of the points of weakness  31 , and to expand radially from the longitudinal axis of the bolt assembly  10 . 
     Once in an in use, expanded state the proximal set screw  36 ′ is inserted into the proximal end of the sleeve  18  and can be rotated to provide a stop, which inhibits further rotation of the shaft  12  relative to the sleeve  18 , therein assuring that the expandable section  30  does not collapse under external pressure from the surrounding bone, with which it is in contact. 
     Rotation of the shaft  12  in the opposite direction can ultimately cause the deformable arms  33  to retract toward the longitudinal axis of the bolt assembly  10 , thereby facilitating the removal of the device, if required. 
       FIG. 5  is a perspective view of a sleeve  118  of a bolt apparatus  110  according to a second embodiment of a first aspect of the present invention. The sleeve  118  comprises a tube, which is generally cylindrical in shape and having an, in use, distal end  40  and proximal end  40 ′. The outer surface of the sleeve  118  adjacent the distal end  40  is generally circular in transverse cross-section. The outer surface of the sleeve  118  adjacent the proximal end  40 ′ is substantially curved having two opposing planar faces  42 ,  42 ′. 
     A number of generally rectangular apertures  120  are provided on the outer surface of the sleeve  118 , each of which extend along the longitudinal axis from adjacent the distal end  40  to approximately one third the length of the sleeve  118 . The area between the apertures  120  defines deformable arms  133 , which form an expandable section  130 , which is located coterminous to the sleeve  118 . The deformable arms  133  extend radially from the longitudinal axis of the sleeve  118 , when in an in use, expanded state. A point of weakness  131  is provided at each of the respective ends of each deformable arm  133 , and at the centre point of the length of each deformable arm  133 . 
       FIG. 6  is a slightly perspective view from the distal end  40 , at a slight angle from the longitudinal axis, of a sleeve  118  of a bolt apparatus  110  according to a second embodiment of a first aspect of the present invention. The inner surface of the sleeve  118  adjacent the proximal end  40 ′ is generally circular in transverse cross-section. The internal diameter of the sleeve  118  adjacent the proximal end  40 ′ is generally of similar length to the external diameter of the shaft  112  (not shown), whereby the shaft  112  can be located longitudinally and rotated coaxially within the sleeve  118 . The inner surface of the sleeve  118  adjacent the distal end  40  is generally circular in transverse cross-section. The internal diameter of the sleeve  118  adjacent the distal end  40  is of a length to allow at least one of the mountable bodies  122 ,  126  (not shown) to locate coaxially within, and to irreversibly engage with, the lumen of the sleeve  118  adjacent the distal end  40 . 
     Once assembled, each of the mountable bodies  122 ,  126  is located on each of the screw threaded portions  114 ,  114 ′(not shown) of the shaft  112 . Each of the mountable bodies  122 ,  126  is in tandem but opposite orientation relative to the other one. The assembly comprising the shaft  112 , and mountable bodies  122 ,  126  is located coaxially within the sleeve  118 , wherein a first mountable body  122  is located adjacent the proximal end  40 ′ of the sleeve  118 , and is preferably attached thereto by an adherent means such as an adhesive; and a second mountable body  126  is located adjacent the distal end  40  of the sleeve  118 , and is preferably attached thereto by an adherent means such as an adhesive and/or by compressive tension applied to the second mountable body  126  by the inner surface of the distal end  40  of the sleeve  118 . 
     Rotation of the shaft  112  within the sleeve  118  causes each of the mountable bodies  122 ,  126  to advance along the screw threaded portions  114 ,  114 ′ of the shaft  12 , respectively. This applies mechanical pressure to the respective ends of the sleeve  118 , wherein the respective ends are bought sequentially into closer proximity relative to one another, causing the deformable arms  133  of the expandable section  130  to deform at each of the points of weakness  131 , and to expand radially from the longitudinal axis of the bolt assembly  110 . 
     Once in an in use, expanded state the proximal set screw  136 ′ (not shown) is inserted into the proximal end of the sleeve  118  and can be rotated to provide a stop, which inhibits further rotation of the shaft  112  relative to the sleeve  118 , therein assuring that each of the deformable arms  133  does not collapse under external pressure from the surrounding bone, with which it is in contact. 
     Rotation of the shaft  112  in the opposite direction can ultimately cause the deformable arms  133  to retract toward the longitudinal axis of the bolt assembly  110 , thereby facilitating the removal of the device, if required. 
       FIG. 8  is an exploded perspective view of a bolt apparatus  210  according to a third embodiment of a first aspect of the present invention. The bolt apparatus  210  comprises a shaft  212 ; a sleeve  218 ; a mountable body  226 ; an expandable section  230 ; and a cap  234 . 
     The shaft  212 ,  FIG. 9 , comprises an elongate member, which is generally cylindrical in shape. Two distinct helical screw threaded portions  214 ,  214 ′ are provided adjacent the respective ends of the shaft  212 , wherein the relative orientation of each screw threaded portion  214 ,  214 ′ is opposite in direction to that of the other. A hexagonal socket is provided at the proximal end  216  of the shaft  212 , and is shaped and adapted to receive a hex key or similar torque delivery device. 
     The sleeve  218 ,  FIGS. 10A  and B, comprises a tube, which is generally cylindrical in shape and having an, in use, distal end  140  and proximal end  140 ′. The outer surface of the sleeve  218  adjacent the distal end  140  is generally circular in transverse cross-section. The outer surface of the sleeve  218  adjacent the proximal end  140 ′ is substantially curved having two opposing planar faces  142 ,  142 ′. 
     An expandable section  230  is located adjacent the distal end  140  of the sleeve  218 . The expandable section  230  comprises a number of generally rectangular apertures  220 , which are provided on the outer surface of the sleeve  218 , each of which extend along the longitudinal axis from adjacent the distal end  140  to approximately one third the length of the sleeve  218 . The area between the apertures  220  defines deformable arms  233 , which extend radially from the longitudinal axis of the sleeve  218 , when in an in use, expanded state. A point of weakness  231  is provided at each of the respective ends of each deformable arm  233 , and at the centre point of the length of each deformable arm  233 . 
     Referring again to  FIG. 8 , the internal diameter of the sleeve  218  adjacent the proximal end  140 ′ is generally of similar length to the external diameter of the shaft  212 , whereby the shaft  212  can be located longitudinally and rotated coaxially within the sleeve  218 . A helical screw thread  221  is provided along a limited length of the inner surface of the sleeve  218 , extending at least part of the length from the proximal end  140 ′ of the sleeve  218  to the expandable section  230 . The helical screw thread  221  is engagable with the screw thread  214  of the shaft  212 . The inner surface of the sleeve  218  adjacent the distal end  140  is generally circular in transverse cross-section. The internal diameter of the sleeve  218  adjacent the distal end  140  is of a length to allow the second mountable body  226  to locate coaxially within, and to irreversibly engage with, the lumen of the sleeve  218  adjacent the distal end  140 . When engaged with the lumen at the distal end  140  of sleeve  218 , the second mountable body  226  is inhibited from coaxially rotating relative to the sleeve  218 , preferably by a press fit, but optionally by use of an adhesive. 
     A second mountable body  226 ,  FIGS. 11A  and B, is provided, which is generally cylindrical in shape and is open at both ends. A helical screw thread  228  is provided on the inner surface of the second mountable body  226 . The internal diameter of the second mountable body  226  is generally of similar length to the external diameter of the shaft  212 , whereby the screw thread  228  of the second mountable body  226  can engage with the screw threaded portion  214 ′ of the shaft  212 . 
     A cap  234 ,  FIGS. 12A  and B, is provided, wherein said cap is a disc, which is generally concave in transverse cross-section on one face. A screw-threaded socket  44  is located at the flat face of the cap  234 . The internal diameter of the screw-threaded socket  44  is generally of similar length to the external diameter of the shaft  212 , whereby the screw-threaded socket  44  can irreversibly engage with the terminal end of the screw threaded portion  214 ′ of the shaft  212 . 
     To assemble the bolt apparatus  210 , the second mountable body  226  is located onto the screw threaded portion  214 ′ of the shaft  212 . The cap  234  is located onto the terminal end of the screw threaded portion  214 ′. The shaft  212  is then inserted coaxially into the lumen of the sleeve  218 , and the screw threaded portion  214  of the shaft  212  is engaged with the helical screw thread  221  on the inner surface of the sleeve  218 , such that the second mountable body  226  is located coaxially within, and irreversibly engages with, the lumen of the sleeve  218  adjacent the distal end  140 . 
     In use, the shaft  212  is rotated using a hex key or similar torque delivery device, inserted into the hexagonal socket is provided at the proximal end  216  of the shaft  212 . Rotation of the shaft  212  within the sleeve  218  causes the proximal end  140 ′ of the sleeve  218  to advance along the screw threaded portion  214  of the shaft  212 ; and the second mountable body  226  to advance, in the opposite direction, along the screw threaded portion  214 ′ of the shaft  212 . This applies mechanical pressure to the respective ends of the expandable section  230 , wherein the respective ends are bought sequentially into closer proximity relative to one another, causing the deformable arms  233  to deform at each of the points of weakness  231 , and to expand radially from the longitudinal axis of the bolt assembly  210 . 
     Rotation of the shaft  212  in the opposite direction can ultimately cause the deformable arms  233  to retract toward the longitudinal axis of the bolt assembly  210 , thereby facilitating the removal of the device, if required. 
     Method of Surgery 
     The exposure and overall technique is similar to that used (as standard) for a dynamic hip screw. The conventional technique permits fixation of a wide variety of intertrochanteric, subtrochanteric and basilar neck fractures using, for example, a dynamic hip screw system provided by Synthes. Reference may be made to the Technique Guide produced by Synthes in this regard. However, an advantage to using the expanding hip bolt will be the possibility of utilising a minimally invasive technique, necessitating specialised instruments, to avoid the need for an open operation. 
     For the purposes of the present invention, a modified standard technique is described, as an alternative to the conventional technique. The patient is anaesthetised by general, regional or local anaesthesia, and placed supine on a standard fracture table. The leg is manipulated under x-ray fluoroscopy image intensifier to achieve a closed reduction. A longitudinal incision is placed (as in standard technique) on the lateral aspect of the thigh and the lateral part of the proximal femoral shaft is exposed using a combination of sharp and blunt dissection through the adipose tissue, fascia lata and vastus lateralis muscle. 
     Using a 2 mm guide wire with a 135 degree drill guide, the position for the proximal fixation is obtained. The optimum position for the expanding hip bolt is similar to that of a DHS lag screw, with the tip-apex distance being less than 5 mm on both AP and lateral views with the image intensifier. The hole for the bolt is drilled over the guide wire using a 9.25 mm drill bit. The wider drill-hole for the barrel at the lateral cortex is drilled using a 13 mm drill bit, over the guide wire. The proximal set screw  36 ′ is removed from the assembled hip bolt apparatus and kept for later use. 
     An introducer with a distal threaded portion is screwed into the proximal threads  21  of the sleeve  18 . The bolt assembly and introducer can be slid though the barrel of the plate to facilitate insertion of the plate onto the femur. The plate (with barrel) is inserted and positioned, so as the barrel fits into its proximal drill-hole and the distal plate sits on the lateral cortex of the femur. The plate is then fixed to the shaft of the femur via cortical screws through the distal holes of the plate. 
     The bolt assembly can be advanced though the barrel until in optimum position confirmed using the image intensifier. The deformable arms of the expandable section should not be deployed until the bolt assembly is in the optimum position, with the plate secured to the femur. The deformable arms are expanded using a torque hex-screwdriver, which rotates the shaft via the distal set screw, thus causing the mountable bodies  22 ,  26  to converge, compressing the expandable section. The torque hex-screwdriver has a torque limiter to prevent excessive torque force being applied to the bolt apparatus. The progress of the deformable arms expanding radially can be followed using the image intensifier. The screwdriver can be removed once the deformable arms have been deployed to an optimal position, as checked on the image intensifier or as limited by the torque limiter. 
     Fracture compression if necessary, can be performed by re-inserting the introducer into the bolt assembly and delivering controlled traction. Leg traction via the fracture table should be released prior to this manoeuvre. The proximal set screw, previously removed and kept, can be now re-inserted into the proximal end of the sleeve, using the hex-screwdriver. This tightens down onto the distal set screw, to prevent rotation or telescoping of the shaft. Final confirmation of the fixation is checked with the image intensifier, and the wound closed. 
     An alternative method of use of a second embodiment of the present invention will now be described, with reference to  FIG. 7  of the drawings. 
     Using a 2 mm guide wire with a 135 degree drill guide, the position for the proximal fixation is obtained. The optimum position for the expanding hip bolt is similar to that of a DHS lag screw, with the tip-apex distance being less than 5 mm on both AP and lateral views with the image intensifier. The hole for the bolt assembly  110  is drilled over the guide wire using a 9.25 mm drill bit. The wider drill-hole for the barrel at the lateral cortex is drilled using a 13 mm drill bit, over the guide wire. 
     The bolt  110  can be advanced though the proximal drill hole until in optimum position confirmed using the image intensifier,  FIG. 7A , ensuring that the proximal end  40 ′ of the sleeve  118  is in the correct orientation to receive the barrel of a plate, FIG.  7 B. The barrel of a plate can then be positioned and inserted on the proximal end  40 ′ of the sleeve  118 ,  FIG. 7B . The plate is then inserted and positioned, so as the barrel fits into its proximal drill-hole and the distal plate sits on the lateral cortex of the femur,  FIGS. 7E &amp; 7F . The plate is then fixed to the shaft of the femur via cortical screws through the distal holes of the plate. 
     The deformable arms  133  of the expandable section should not be deployed until the bolt assembly  110  is in the optimum position and rotation of the sleeve  118  is resisted by the barrel and plate that are securely fixed to the shaft of the femur. The deformable arms  133  are expanded using a torque screwdriver (not shown), which rotates the shaft  112 ,  FIG. 7C , thus causing the mountable bodies  122 ,  126  to converge, compressing the expandable section  130 ,  FIG. 7D . The torque screwdriver has a torque limiter to prevent excessive torque force being applied to the bolt assembly  110 . The progress of the deformable arms  133  expanding radially can be followed using the image intensifier. The screwdriver can be removed once the arms have been deployed to an optimal position, as checked on the image intensifier or as limited by the torque limiter. 
     Final confirmation of the fixation is checked with the image intensifier, and the wound closed. 
     The above-mentioned alternative method of surgical use has now be described using the bolt apparatus of the second embodiment of the invention. It will, of course, be appreciated that the above-mentioned alternative method of surgical use can equally be employed with any other bolt apparatus of the invention, including those of the first and third embodiments of the first aspect of the invention. 
     The invention is not limited to the embodiments described herein but can be amended or modified without departing from the scope of the present invention.