Patent Publication Number: US-2007123995-A1

Title: Method and apparatus for reducing femoral fractures

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This is a divisional of co-pending U.S. patent application Ser. No. 10/266,319, filed Oct. 8, 2002, which is a continuation-in-part of U.S. patent application Ser. No. 10/155,683, filed May 23, 2002, which is a continuation-in-part of U.S. patent application Ser. No. 09/520,351, filed Mar. 7, 2000, now U.S. Pat. No. 6,447,514, the disclosures of which are each expressly incorporated herein by reference. 
    
    
     BACKGROUND  
      1. Field of the Invention  
      The present invention relates to a method and apparatus for treating hip fractures, and, more particularly, to a method and apparatus for reducing femoral fractures utilizing a minimally invasive procedure.  
      2. Description of the Related Art  
      Current procedures utilized to reduce hip fractures generally utilize a side plate/hip screw combination, i.e., a bone plate affixed to a lateral aspect of the femur and having a hip screw operably connected thereto, with the hip screw extending into the femoral head. To properly implant a side plate hip screw, a surgeon must dissect an amount of muscle to expose the femur and operably attach the bone plate and hip screw. Typically, the side plate hip screw requires an incision of about 10-12 cm through the quadriceps to expose the femur. While this approach provides surgeons with an excellent view of the bone surface, the underlying damage to soft tissue, including muscle, e.g., the quadriceps can lengthen a patient&#39;s rehabilitation time after surgery.  
      What is needed in the art is a method and apparatus for reducing a hip fracture without requiring incision of soft tissue, including, e.g., the quadriceps.  
     SUMMARY  
      The present invention provides an improved method and apparatus for reducing a hip fracture utilizing a minimally invasive procedure which does not require dissection of the quadriceps. A femoral implant in accordance with the present invention achieves intramedullary fixation as well as fixation into the femoral head to allow for the compression needed for a femoral fracture to heal. The femoral implant of the present invention allows for sliding compression of the femoral fracture. To operably position the femoral implant of the present invention, an incision aligned with the greater trochanter is made and the wound is developed to expose the greater trochanter. The size of the wound developed on the surface is substantially constant throughout the depth of the wound. In one exemplary embodiment of the present invention, the incision through which the femur is prepared and the implant is inserted measures about 2.5 centimeters (1 inch). Because the greater trochanter is not circumferentially covered with muscle, the incision can be made and the wound developed through the skin and fascia to expose the greater trochanter, without incising muscle, including, e.g., the quadriceps. After exposing the greater trochanter, novel instruments of the present invention are utilized to prepare a cavity in the femur extending from the greater trochanter into the femoral head and further extending from the greater trochanter into the intramedullary canal of the femur. After preparation of the femoral cavity, a femoral implant in accordance with the present invention is inserted into the aforementioned cavity in the femur. The femoral implant is thereafter secured in the femur, with portions of the implant extending into and being secured within the femoral head and portions thereof extending into and being secured within the femoral shaft. To allow for sliding compression, the portion of the implant extending into the femoral head is slidable relative to the portion of the implant extending into the femoral shaft.  
      The femoral implant of the present invention includes a sealed bag having a fill tube positioned therein to provide access to the bag interior so that the implant bag can be filled with material, e.g., bone cement after implantation of the femoral implant within the cavity formed in the femur. The femoral implant of the present invention further includes a lag screw tube placed within the bag of the femoral implant. The bag of the femoral implant is tightly secured to the exterior of the lag screw tube to prevent material injected into the bag from escaping the bag at any point at which the bag contacts the lag screw tube. The lag screw tube is hollow and accommodates a lag screw or other fixation device to be advanced into and secured to the femoral head.  
      The sealed bag of the femoral implant of the present invention can be, e.g., formed of various films and fabrics. In one exemplary embodiment the bag of the femoral implant of the present invention is formed from an acrylic material, e.g., a woven acrylic material. Because bone cement is an acrylic, if the implant bag is formed of an acrylic material, the bag and the bone cement will achieve an intimate chemical bond. The bag of the femoral implant of the present invention generally comprises a containment device and can be constructed of various materials including films such as, e.g., fiber or fabric reinforced films, or fabrics created by processes such as weaving, knitting, braiding, electrospinning, or hydrospinning. Alternative materials contemplated for the implant bag include various polymers including, e.g., polymethylmethacrylate, polycarbonate, ultra-high molecular weight polyethylene (UHMWPE), low density polyethylene (LDPE), high density polyethylene (HDPE), polyamides, polypropylene, polyester, polyaryletherketone, polysulfone, or polyurethane. Further alternative materials contemplated for the implant bag include fabrics constructed of fibers formed of glass, ceramics, surgical grade stainless steel (e.g., 316L), titanium, or titanium alloys. Moreover, implant bag materials may be coated with, e.g., calcium phosphate, or a bioactive glass coating. Furthermore, the implant bag and filler may be utilized as a delivery mechanism for, e.g., drugs, or growth factors.  
      In a further embodiment of the present invention, the bag structure of the implant of the present invention comprises a nested bag structure in which an inner bag is filled with a high strength material relative to the material of an outer bag in which the inner bag is placed. The outer bag of this form of the present invention is formed from and filled with a more bioresorbable material relative to the material of construction and fill material of the inner bag.  
      The femoral implant of the present invention is inserted through an access aperture formed in the greater trochanter and placed within the femoral cavity described hereinabove. The lag screw or other fixation device is thereafter advanced through the lag screw tube and into the cavity formed in the femoral head. The lag screw or other fixation device is then secured to the femoral head. The fill tube is thereafter utilized to fill the femoral implant with, e.g., bone cement to fill the femoral cavity and provide intramedullary fixation and stabilization of the lag screw. In an alternative embodiment of the present invention, bone cement is utilized in lieu of or in addition to lag screw threads to secure a lag screw shaft of an implant of the present invention.  
      Several different guides and reamers may be utilized in accordance with the present invention to ream the femoral cavity described hereinabove. These novel guides and reamers will be described in detail in the detailed description portion of this document. Generally, the guides and reamers of the present invention are designed to allow for formation of a femoral cavity from the greater trochanter across the femoral neck and into the femoral head as well as from the greater trochanter into the intramedullary canal, with the femoral cavity having exposed access thereto only over the greater trochanter.  
      The method and apparatus of the current invention advantageously allow for the treatment of a femoral hip fracture in a minimally invasive procedure, which hastens patient recovery. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:  
       FIG. 1  is a partial perspective view of a patient, with an incision made along the greater trochanter to allow for implantation of a femoral implant of the present invention;  
       FIG. 2  is a partial perspective view illustrating insertion of a guide plate in accordance with the present invention;  
       FIG. 3  is a partial perspective view illustrating a guide tube/retractor in accordance with the present invention inserted through the incision aligned with the greater trochanter and engaged with the guide plate;  
       FIG. 4  is an elevational view illustrating the use of an alignment device of the present invention to properly select the appropriate guide tube/retractor of the present invention;  
       FIG. 5  is an elevational view illustrating the alignment guide of  FIG. 4  properly aligned from the greater trochanter along the femoral neck to the femoral head;  
       FIG. 6  is a sectional view of a femur illustrating a plunge reamer utilized to begin making the femoral cavity of the present invention;  
       FIG. 7  is a sectional view illustrating the use of a swivel reamer in accordance with the present invention to further form the femoral cavity;  
       FIG. 8  is a sectional view illustrating further use of the swivel reamer depicted in  FIG. 7  to form the femoral cavity;  
       FIG. 9  is a sectional view illustrating the use of a curved femoral head reamer to extend the femoral cavity into the femoral head;  
       FIG. 10  is a sectional view illustrating the use of a curved femoral reamer to extend the femoral cavity into the intramedullary canal of the femur;  
       FIG. 11  is a sectional view illustrating a femoral cavity formed in accordance with the present invention;  
       FIG. 12  is a sectional view illustrating insertion of a femoral implant of the present invention into the femoral cavity illustrated in  FIG. 11 ;  
       FIG. 13  is a sectional view illustrating extension of the bag of the femoral implant into the intramedullary canal;  
       FIG. 14  is a sectional view illustrating extension of a lag screw through the lag screw tube and into the femoral head, as well as a pump and source of bag fill, e.g., bone cement, utilized to fill the bag of the femoral implant of the present invention;  
       FIG. 15  is a perspective view of a guide plate in accordance with the present invention;  
       FIGS. 16, 17 , and  18  are, respectively, top, side, and bottom elevational views thereof;  
       FIG. 19  is a sectional view of an insertion member of the present invention with the guide plate illustrated in  FIGS. 15-18  affixed thereto;  
       FIG. 20  is a perspective view of an insertion member which is utilized to operably position a guide plate, e.g., the guide plate illustrated in  FIGS. 15-18  atop the greater trochanter as illustrated in  FIG. 2 ;  
       FIG. 21  is a partial elevational view illustrating deactuation of the latch utilized to temporarily fix the guide plate to the insertion member;  
       FIG. 22  is a side elevational view of the insertion member illustrated, e.g., in  FIG. 20 ;  
       FIG. 23  is a perspective view of a guide tube/retractor of the present invention;  
       FIG. 24  is a radial elevational view thereof;  
       FIG. 25  is a further radial elevational view thereof, rotated approximately 90 degrees with respect to the radial elevational view of  FIG. 24 ;  
       FIG. 26  is a proximal axial view thereof;  
       FIG. 27  is a distal axial view thereof;  
       FIG. 28  is a radial elevational view of an angled guide tube/retractor of the present invention;  
       FIG. 29  is a perspective view of an alignment device of the present invention;  
       FIG. 30  is an elevational view thereof;  
       FIG. 31  is a perspective view of a plunge reamer of the present invention;  
       FIG. 32  is a distal axial view thereof;  
       FIG. 33  is a partial sectional, elevational view thereof;  
       FIG. 34  is a perspective view of a swivel reamer of the present invention;  
       FIG. 35  is a proximal axial elevational view thereof;  
       FIG. 36  is a sectional view taken along line  36 - 36  of  FIG. 38 ;  
       FIG. 37  is a distal axial elevational view thereof;  
       FIG. 38  is a partial sectional, radial elevational view of the swivel reamer of the present invention;  
       FIG. 39  is a perspective view of a curved femoral head reamer of the present invention;  
       FIG. 40  is a sectional view thereof;  
       FIG. 41  is an elevational view of a femoral implant of the present invention;  
       FIG. 42  is an exploded view of a lag screw of the present invention;  
       FIG. 43  is a sectional view of the femoral implant of the present invention taken along line  43 - 43  of  FIG. 41 ;  
       FIG. 44  is a perspective view of an alternative embodiment alignment device of the present invention;  
       FIG. 45  is an elevational view thereof;  
       FIG. 46  is a perspective view of a combination reamer in accordance with the present invention;  
       FIG. 47  is a sectional view thereof illustrating actuation of the swivel/plunge reaming selector into the plunge reaming position;  
       FIG. 48  is a sectional view thereof with the swivel/plunge reaming selector moved into position for swivel reaming;  
       FIG. 49  is a partial sectional view of the combination reamer of the present invention;  
       FIG. 50  is a perspective view of an alternative embodiment guide plate in accordance with the present invention;  
       FIGS. 51-54  are top, end, side, and bottom elevational views thereof, respectively;  
       FIG. 55  is a sectional view thereof taken along line  55 - 55  of  FIG. 53 ;  
       FIG. 56  is a perspective view of an alternative embodiment guide tube/retractor of the present invention;  
       FIG. 57  is a radial elevational view thereof;  
       FIG. 58  is a radial elevational view of an alternative embodiment angled guide tube/retractor of the present invention;  
       FIG. 59  is a distal axial elevational view of the guide tube/retractor illustrated in  FIG. 57 ;  
       FIG. 60  is a partial sectional view of the guide tube/retractor illustrated in  FIG. 57  taken along line  60 - 60  thereof;  
       FIG. 61  is a perspective view of a fixation screw in accordance with an alternative embodiment of the present invention;  
       FIG. 62  is a radial elevational view thereof;  
       FIG. 63  is a distal axial view thereof;  
       FIG. 64  is a proximal axial view thereof;  
       FIG. 65  is a perspective view of a second alternative embodiment guide plate in accordance with the present invention;  
       FIG. 66  is a top elevational view thereof;  
       FIG. 67  is a sectional view thereof taken along line  67 - 67  of  FIG. 66 ;  
       FIG. 68  is a bottom elevational view thereof;  
       FIG. 69  is a perspective view of a second alternative embodiment guide tube/retractor in accordance with the present invention;  
       FIG. 70  is a radial elevational view thereof;  
       FIG. 71  is an exploded view of a flexible reamer guide in accordance with the present invention;  
       FIG. 72  is a sectional view thereof;  
       FIG. 73  is a sectional view illustrating the flexible reamer guide of  FIGS. 71 and 72  operably positioned within a patient&#39;s femur to guide a flexible reamer into the femoral head;  
       FIG. 74  is a sectional view illustrating a flexible reamer positioned over a flexible reamer guide wire for reaming into the femoral head;  
       FIG. 75  is a perspective view of a flexible reamer in accordance with the present invention;  
       FIG. 76  is a sectional view thereof;  
       FIG. 77  is an exploded view of a flexible reamer guide wire bender in accordance with the present invention;  
       FIG. 78  is an elevational view thereof;  
       FIG. 79  is a sectional view thereof;  
       FIG. 80  is an axial elevational view of the distal end of a fixation screw placement instrument in accordance with the present invention;  
       FIG. 81  is a perspective view of the fixation screw placement instrument partially illustrated in  FIG. 80 ;  
       FIG. 82  is a perspective view of a straight reamer utilized to prepare the greater trochanter to receive the fixation screw illustrated in  FIG. 61-64 ;  
       FIG. 83  is a perspective view of an alternative embodiment insertion member for inserting a guide plate of the present invention;  
       FIG. 84  is a partial sectional view thereof illustrating the release bars thereof actuated to effect release of the guide plate from locking engagement with the insertion member;  
       FIG. 85  is a partial sectional view illustrating the release bars of the insertion member illustrated in  FIG. 83  positioned whereby the guide plate can be temporarily fixed to the insertion member;  
       FIG. 86  is an elevational view of the insertion member illustrated in  FIG. 83 ;  
       FIG. 87  is a perspective view of a spring lock release instrument in accordance with the present invention;  
       FIG. 88  is a partial sectional view of the distal end thereof, illustrating the release pins in an unactuated position;  
       FIG. 89  is a sectional view of the spring lock release instrument of  FIG. 87  actuated to force release pins  346  to protrude therefrom;  
       FIG. 90  is an elevational view of an alternative embodiment femoral implant of the present invention;  
       FIG. 91  is a sectional view of an alternative embodiment lag screw of the present invention, illustrating insertion of an actuating device for actuating the lag screw head;  
       FIG. 92  is a partial sectional view of a further alternative embodiment lag screw of the present invention;  
       FIG. 93  is a partial elevational view of a femur illustrating insertion of a guide wire to guide reaming from the greater trochanter into the femoral head;  
       FIG. 94  is a partial elevational view of a femur illustrating use of a flexible reamer having two reaming diameters to ream a passage from the greater trochanter into the femoral head;  
       FIG. 95  is a partial radial elevational view of a flex up reamer for reaming a passage from the greater trochanter into the femoral head;  
       FIG. 96  is a distal axial elevational view thereof;  
       FIG. 97  is a radial elevational view of a telescoping reamer of the present invention illustrating extension of a reaming head therefrom;  
       FIG. 98  is a radial elevational view of the telescoping reamer of  FIG. 97  shown in its retracted position;  
       FIG. 99  is an exploded view of the telescoping reamer of  FIGS. 97 and 98 ;  
       FIG. 100  is a perspective view of a swivel/down reamer assembly shown in unactuated position;  
       FIG. 101  is a perspective view thereof shown in actuated position;  
       FIG. 102  is an exploded view of the swivel/down reamer assembly illustrated in  FIGS. 100 and 101 ;  
       FIG. 103  is a partial elevational view illustrating use of the swivel/down reamer assembly depicted in  FIGS. 100-102  to extend the femoral cavity into the intramedullary canal;  
       FIG. 104  is a sectional view of the tool housing of the swivel/down reamer assembly depicted in  FIGS. 100-102 ;  
       FIG. 105  is a radial elevational view of a flexible guide shaft of the swivel/down reamer assembly depicted in  FIGS. 100-102 ;  
       FIG. 106  is an axial elevational view thereof;  
       FIG. 107  is a perspective view of a unitube retractor of the present invention with the ball detent retaining mechanism thereof illustrated in position to retain an instrument within the unitube retractor;  
       FIG. 108  is a perspective view of the unitube retractor of  FIG. 107  illustrating the ball detent retaining mechanism actuated to allow for release of an instrument positioned within the unitube retractor;  
       FIG. 109  is an exploded perspective view of the unitube retractor illustrated in  FIGS. 107 and 108 ;  
       FIG. 110  is a sectional view of a plunger forming a part of the ball detent retaining mechanism depicted with the unitube retractor of  FIGS. 107-109 ;  
       FIG. 111  is an exploded perspective view of an alternative embodiment unitube retractor in accordance with the present invention;  
       FIG. 112  is a sectional view of the lock ring of the unitube retractor depicted in  FIG. 111 ;  
       FIG. 113  is a radial elevational view of the unitube retractor illustrated in  FIG. 111  shown in unactuated position;  
       FIG. 114  is a radial elevational view illustrating the unitube retractor of  FIGS. 111 and 113  in actuated position, with the fingers of the lock ring thereof radially expanded to lock the unitube retractor to the femur through the access formed therein; and  
       FIG. 115  is a partial radial elevational view thereof. 
    
    
      Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated to better illustrate and explain the present invention. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.  
      Throughout this document, “proximal” and “distal” are used to refer to opposite ends of instruments described herein. When referring to the opposite ends of instruments, “proximal” and “distal” are used with reference to a user of the instrument. For example, the end of the instrument nearest to the user during use thereof is described as the proximal end, while the end of the instrument farthest from the user during use thereof is described as the distal end of the instrument.  
     DETAILED DESCRIPTION  
      Implant  260  illustrated in  FIG. 41  is utilized to reduce a femoral fracture utilizing a method of implantation which does not require incision of the quadriceps. As illustrated in  FIG. 1 , incision  106  is aligned with greater trochanter  110 , with femur  108  being prepared to receive implant  260  through incision  106 . As described above, greater trochanter  110  is not covered with muscle and therefore, incision  106  can be developed to expose greater trochanter  110  without requiring the incision of muscle. Incision  106  measures about 2.5 centimeters (1 inch).  FIGS. 6-10  illustrate use of various novel reamers of the present invention to form femoral cavity  224  ( FIG. 11 ). Various instruments described below may be utilized in lieu of or in conjunction with the instruments illustrated in  FIGS. 6-10 . As illustrated in  FIG. 12 , implant  260  (further illustrated in  FIGS. 41-43 ) is inserted into femoral cavity  224  via access  101  ( FIGS. 13 and 14 ) formed through greater trochanter  110 . As illustrated in  FIG. 13 , lag screw  264  is advanced into femoral head  114  until lag screw threads  282  firmly engage femoral head  114  and lag screw  264  has achieved the position illustrated in  FIG. 14 . Bag  270  is thereafter filled with material, e.g., bone cement to fill femoral cavity  224  and provide intramedullary fixation of implant  260  and stabilization of lag screw  264 . In this way, a femoral fracture including, e.g., an intertrochanteric fracture can be reduced. Generally, this document will refer to a femoral fracture and, specifically, to an intertrochanteric fracture. However, the method and apparatus of the present invention is adaptable to various bone fractures including, e.g., supracondylar fractures of the femur.  
       FIG. 1  generally illustrates patient  100  including torso  102 , and legs  104 .  FIG. 1  further illustrates the general bone structures comprising the hip joint including, pubis  122 , anterior superior iliac spine  118 , ilium  116 , acetabulum  120 , and femur  108 . As illustrated in  FIG. 1 , femur  108  includes, e.g., greater trochanter  110 , femoral neck  112 , and femoral head  114 . As described above, incision  106  is aligned with greater trochanter  110 . Because greater trochanter  110  is not covered with muscle, incision  106  can be made and the wound developed through the skin and fascia to expose greater trochanter  110  without incising muscle, including, e.g., the quadriceps.  
      In one embodiment of the present invention, cannulated insertion member  124  is utilized to insert guide plate  126  through incision  106  to be placed atop and secured to greater trochanter  110  as illustrated, e.g., in  FIG. 2 . After guide plate  126  traverses incision  106  and is placed atop greater trochanter  10 , stabilization nail  144  is positioned through elongate aperture  132  ( FIG. 19 ) of insertion member  124  and impaction instrument  148  ( FIG. 2 ) is utilized to strike impaction surface  146  to drive stabilization nail  144  into femur  108  to provide initial stability to guide plate  126  prior to utilizing screws  128  ( FIG. 1 ) to fix guide plate  126  to greater trochanter  10 . In one exemplary embodiment, the surgeon implanting guide plate  126  will utilize a fluoroscope to verify proper placement of guide plate  126  atop greater trochanter  110 . In alternative embodiments, the surgeon implanting guide plate  126  will utilize tactile feedback either alone or in conjunction with a fluoroscope image to determine proper placement of guide plate  126  atop greater trochanter  110 . After guide plate  126  is properly positioned atop greater trochanter  110 , screws  128  are driven through corresponding screw apertures  286  ( FIG. 15 ) in guide plate  126  and into femur  108  to secure guide plate  126  to femur  108 . Screw apertures  286  are, in one exemplary embodiment, formed in guide plate  126  to allow for oblique insertion of screws  128  relative to guide plate  126 .  
      Insertion member  124  is illustrated in detail in  FIGS. 19-22 . As illustrated, insertion member  124  includes elongate aperture  132  accommodating stabilization nail  144  as described hereinabove. Insertion member  124  includes tubular latch connector  140  positioned about the distal end thereof. Intermediate the main body of insertion member  124  and tubular latch connector  140  is positioned spring  136 . Spring  136  acts against spring stop  150  to bias tubular latch connector into the position illustrated in  FIG. 22 . Release member  134  is connected to tubular latch connector  140  and is operable to facilitate movement of tubular latch connector  140  against the biasing force of spring  136  into the position illustrated in  FIG. 21 . Insertion member  124  includes distal end  142  for engaging guide plate  126 . Distal end  142  includes bosses  152  extending therefrom.  
      Guide plate  126  is temporarily affixed to insertion member  124  as described below. Bosses  152  of insertion member  124  enter attachment channels  290  of guide plate  126  (see, e.g.,  FIGS. 15 and 17 ). Concurrently, latch  138 , connected to tubular latch connector  140 , acts against the proximal surface of guide plate  126  to force tubular latch connector  140  against the biasing force of spring  136  and into the position illustrated in  FIG. 21 . Distal end  142  of insertion member  124  is then rotated until bosses  152  are positioned under lips  291  formed by attachment channels  290  and latch  138  can be positioned within one of attachment channels  290  and returned to its naturally biased position as illustrated in  FIGS. 19 and 22 . When guide plate  126  is attached to insertion member  124 , one of bosses  152  and latch  138  abut opposing radial extremes of one attachment channel  290  to prevent relative rotation of guide plate  126  and insertion member  124 . Moreover, when guide plate  126  is attached to insertion member  124 , bosses  152  cooperate with lips  291  formed by attachment channels  290  to prevent relative axial displacement of guide plate  126  and insertion member  124 . In this way, guide plate  126  is secured to insertion member  124  to facilitate positioning guide plate  126  atop greater trochanter  110  as described hereinabove.  
      After guide plate  126  is secured to greater trochanter  110 , release member  134  may be actuated to position latch  138  in the position illustrated in  FIG. 21  to allow for rotation of distal end  142  of insertion member  124  relative to guide plate  126 . When latch  138  is positioned as illustrated in  FIG. 21 , it is no longer contained within attachment channel  290  and therefore allows relative rotation between guide plate  126  and insertion member  124 . Distal end  142  of insertion member  124  is rotated to reposition bosses  152  out of axial alignment with lips  291  for removal from attachment channels  290 . Insertion member  124  is thereafter removed from engagement with guide plate  126  and removed through incision  106 .  
      After securement of guide plate  126  atop greater trochanter  110 , guide tube/retractor  154  ( FIGS. 23-27 ) is inserted through incision  106  and releasably fixed to guide plate  126  as illustrated in  FIG. 3 . Guide tube/retractor  154  is illustrated in detail in  FIGS. 23-27 , and guide plate  126  is illustrated in detail in  FIGS. 15-18 . With reference to  FIGS. 23-27  and  15 - 18 , the cooperating apparatus of guide tube/retractor  154  and guide plate  126  allowing for selective locking of guide tube/retractor  154  to guide plate  126  will now be described. Fixation of guide tube/retractor  154  to guide plate  126  is effected by first positioning attachment protrusions  302  of straight guide tube/retractor  154  into attachment channels  290  of guide plate  126 . Guide tube/retractor  154  is then rotated clockwise to position the radially extending portion of attachment protrusions  302  under lips  291  formed by attachment channels  290  of guide plate  126 . Once rotated into this position, spring biased locking pin  294  of guide tube/retractor  154  is positioned within lock detent  292  of guide plate  126  to prevent relative rotation of guide plate  126  and guide tube/retractor  154  and lock guide tube/retractor  154  to guide plate  126 .  
      As illustrated in  FIGS. 23 and 24 , spring biased locking pin  294  extends substantially axially along guide tube/retractor  154  and is operably connected to actuation member  300  to provide for manual actuation of locking pin  294 . Spring  298  is operatively associated with spring biased locking pin  294  and the interior of the cylindrical wall forming guide tube/retractor  154  to bias locking pin  294  into the position illustrated in  FIG. 24 . When distal shoulder  303  of guide tube/retractor  154  is initially positioned atop the proximal end of guide plate  126 , with attachment protrusions  302  entering attachment channels  290 , locking pin  294  is moved against the biasing force of spring  298  until guide tube/retractor  154  is rotated as described hereinabove to align locking pin  294  with detent  292  and lock guide tube/retractor  154  to guide plate  126 .  
      While the engagement of a guide tube/retractor of the present invention with guide plate  126  has been described with respect to straight guide tube/retractor  154 , angled guide tube/retractor  296  (illustrated in  FIG. 28  and described below) is locked to guide plate  126  in the same manner utilizing the same structure as described above with respect to straight guide tube/retractor  154 . The shared components of straight guide tube/retractor  154  and angled guide tube/retractor  296  are denoted with primed reference numerals. The mechanism for locking a guide tube/retractor of the present invention to guide plate  126  allows for locking of a guide tube/retractor to guide plate  126  in one of two positions separated by 180 degrees. This allows for angled guide tube/retractor  296  to provide for realignment in two directions as further described hereinbelow.  
      Guide tube/retractor  154  serves the dual purpose of maintaining an access from incision  106  to greater trochanter  110  and guiding various instruments utilized to prepare femoral cavity  224  ( FIG. 11 ). Generally, either a straight or an angled guide tube/retractor will be utilized.  FIGS. 24 and 28  respectively illustrate straight guide tube/retractor  154  and angled guide tube/retractor  296 . As illustrated, e.g., in  FIG. 28 , angled guide tube/retractor  296  includes distal end  299  and retractor body  301 . Longitudinal axis  297  of distal end  299  of angled guide tube/retractor  296  forms an angle Ø of about 10° with longitudinal axis  303  of retractor body  301 . In this way, angled guide tube/retractor  296  allows for a 10° realignment with respect to straight guide tube/retractor  154 . A surgeon can choose either straight guide tube/retractor  154  or angled guide tube/retractor  296  based upon the geometry of femur  108  into which implant  260  ( FIG. 41 ) will be placed. In accordance with the present invention, an alignment device is provided to facilitate choice of straight guide tube/retractor  154  or angled guide tube/retractor  296  as well as the orientation of angled guide tube/retractor  296  as further described hereinbelow.  
       FIGS. 4 and 5  illustrate use of alignment device  156  to choose either straight guide tube/retractor  154  or angled guide tube/retractor  296 . Alignment device  156  is illustrated in detail in  FIGS. 29 and 30  and includes extension  166  connected to transverse bar  168 , with alignment arm  174  slidably attached thereto. As illustrated in  FIG. 29 , extension  166  is connected to insertion member  160  at a distal end thereof. Insertion member  160  is sized for insertion into either straight guide tube/retractor  154  or angled guide tube/retractor  296  as illustrated in  FIGS. 4 and 5 .  
      As illustrated in  FIGS. 29 and 30 , insertion portion  160  of alignment device  156  includes distal end  158  connected via connecting rods  184  to positioning cylinder  164 . Positioning cylinder  164  includes a pair of opposing bosses  162 , only one of which is depicted in  FIGS. 29 and 30 . Distal end  158  and positioning cylinder  164  have external geometries sized to cooperate with the hollow interior of the guide tube/retractors of the present invention to provide a stationary base for alignment device  156 , as illustrated in  FIGS. 4 and 5 . Insertion portion  160  of alignment device  156  as illustrated in  FIGS. 29 and 30  comprises merely one exemplary design for an insertion portion of alignment device  156  operable to stabilize alignment device  156  with the guide tube/retractors of the present invention. Generally, insertion portion  160  will include a portion thereof having an exterior geometry sized to cooperate with the interior of the guide tube/retractors of the present invention to provide a stationary base for alignment device  156 . In an alternative embodiment, the insertion portion of alignment device  156  depicted in  FIGS. 29 and 30  comprises a solid insertion member having a consistent cross sectional area along its length. In this embodiment, the exterior of the solid insertion member will cooperate with the interior of the guide tube/retractors of the present invention to provide a stable connection of alignment device  156  with a guide tube/retractor in accordance with the present invention.  
      Alignment device  156  includes transverse bar  168  fixed to extension  166  via screw  170 . Positioning cylinder  164  and extension  166  provide a stable base for transverse bar  168 . As illustrated in  FIGS. 29 and 30 , alignment arm  174  is slidably connected to transverse bar  168  via slidable attachment member  176 . Slidable attachment member  176  includes attachment block  178  having a cutout therein accommodating transverse bar  168 . Top plate  180  is mounted atop attachment block  178 , with set screw  172  threaded therein. Set screw  172  traverses top plate  180  to selectively engage transverse bar  168  and lock alignment arm  174  in position along transverse bar  168 .  
      As illustrated in  FIGS. 4 and 5 , alignment device  156  is utilized to facilitate selection of the appropriate guide tube/retractor.  FIG. 5  illustrates alignment device  156  operably positioned within straight guide tube/retractor  154 , which is locked to guide plate  126 . In use, bosses  162  on positioning cylinder  164  are positioned within attachment channels  290  of guide plate  156  and positioning cylinder  164  is rotated until bosses  162  contact the terminal ends of channels  290  and are positioned under lips  291 . After positioning alignment device  156  within guide tube/retractor  154 , slidable attachment member  176  may be adjusted to accommodate the physiological characteristics of the patient and place alignment arm  174  adjacent the patient&#39;s skin. Alignment arm  174  of alignment device  156  includes a curved distal end having a curvature based on statistical data which follows a path from the central portion of greater trochanter  110 , along the central axis of femoral neck  112 , to the central region of femoral head  114 .  FIG. 5  illustrates an arrangement with the distal end of alignment arm  174  following the aforementioned path on femur  108 . In the environment illustrated in  FIG. 5 , straight guide tube/retractor  154  is the appropriate guide tube/retractor to be utilized to effect the method of the present invention. In some cases, the distal end of alignment arm  174  will not coincide with the aforementioned path on the femur in question due to, e.g., the specific geometry of the bone in question. In this case, angled guide tube/retractor  296  may be utilized in an attempt to provide the appropriate alignment with the femur in question.  
       FIG. 4  illustrates alignment device  156  utilized with angled guide tube/retractor  296  on femur  108 . As described above, femur  108 , illustrated, e.g., in  FIGS. 4 and 5  has a geometry accommodating the use of straight guide tube/retractor  154 . With this in mind,  FIG. 4  is useful in illustrating a situation in which the distal end of alignment arm  174  does not follow a path from the central portion of greater trochanter  110 , along the central axis of femoral neck  112  to the central region of femoral head  114  and, therefore, use of the attached guide tube/retractor, i.e., angled guide tube/retractor  296  is contraindicated. Comparison of the distal end of alignment arm  174  to the aforementioned path from the central portion of the greater trochanter, along the central axis of the femoral neck to the central portion of the femoral head will be effected during surgery with the use of a fluoroscope.  
      Generally, straight guide tube/retractor  154  will first be locked to guide plate  126 , and alignment device  156  will be operably positioned therein. A fluoroscope will then be utilized to compare the distal end of alignment arm  174  with the path from the central portion of the greater trochanter, along the central axis of the femoral neck to the central portion of the femoral head. If the distal end of alignment arm  174  does not follow the aforementioned path from the central portion of the greater trochanter to the central portion of the femoral head, then alignment device  156  and straight guide tube/retractor  154  will be removed and angled guide tube retractor  296  will be locked to guide plate  126 . The angle Ø of about 10° formed between longitudinal axis  297  of distal end  299  of angled guide tube/retractor  296  and longitudinal axis  303  of retractor body  301  allows for an approximately 10 degree realignment on either side of the longitudinal axis of straight guide tube/retractor  154  in a plane substantially containing the central axis of femur  108 . The inventors of the current invention have found that this 10 degree realignment in either direction typically accounts for the various bone geometries encountered. However, the inventors of the present invention further contemplate provision of additional angled guide tubes/retractors having an angle Ø as described hereinabove of other than 10 degrees. For example, Ø could measure 5°, 10°, or 15° to provide for increased versatility in performing the method of reducing a femoral fracture in accordance with the present invention.  
      Once the appropriate guide tube/retractor is chosen and attached to guide plate  126 , cavity  224  ( FIG. 11 ) can be formed in femur  108 . As illustrated in  FIG. 6 , straight reamer  186  is first positioned within guide tube/retractor  154  and utilized to create access  101  in greater trochanter  110 . In one exemplary embodiment, access  101  has a 1.9 centimeter (0.75 inch) diameter. After creating access  101  in greater trochanter  110 , straight reamer  186  is removed from guide tube/retractor  154  and replaced with swivel reamer  202  as illustrated, e.g., in  FIG. 7 . As illustrated in  FIG. 7 , swivel reamer  202  is rotatable about pivot  216  and, in the configuration illustrated in  FIG. 7 , allows for the extension of femoral cavity  224  toward femoral head  114 . After femoral cavity  224  is extended as illustrated in  FIG. 7 , swivel reamer  202  is repositioned to allow for extension of femoral cavity  224  toward the shaft of femur  108  as illustrated in  FIG. 8 . Swivel reamer  202  is then removed in favor of curved femoral head reamer  226 . As illustrated in  FIG. 9 , curved femoral head reamer  226  is advanced through access  101  into femoral head  114 , thus expanding femoral cavity  224  into femoral head  114 . Curved femoral head reamer  226  is thereafter removed from guide tube/retractor  154  and replaced with curved femoral shaft reamer  244 , as illustrated in  FIG. 10 . Curved femoral shaft reamer  244  is positioned through access  101  into the intramedullary canal of femur  108 , as illustrated in  FIG. 7 , to extend femoral cavity  224  into the femoral shaft. The reaming process illustrated in  FIGS. 6-10  produces femoral cavity  224  as illustrated, e.g., in  FIG. 11 .  
      Straight reamer  186  is illustrated in detail in  FIGS. 31-33 . As illustrated in  FIGS. 31-33 , straight reamer  186  includes straight reamer guide tube  188  surrounding straight reamer shaft  192 . Straight reamer guide tube  188  is positioned intermediate straight reamer head  190  and flange  194  and is operable to move along reamer shaft  192  therebetween. Straight reamer guide tube  188  as an exterior geometry cooperating with the internal geometry of straight guide tube/retractor  154  and/or angled guide tube/retractor  296  to provide a solid base for reaming femur  108  as illustrated in  FIG. 6 . Straight reamer  186  further includes proximal end  198  adapted to be received in chuck  200  ( FIG. 6 ) of any of the well known rotation devices utilized to impart rotational motion to various medical instruments including, e.g., reamers. Straight reamer guide tube  188  includes opposing bosses  196  protruding from the exterior surface thereof. Bosses  196  are engagable in boss channels  304  formed in the proximal end of the guide tube/retractors of the present invention (see, e.g.,  FIGS. 23, 24 , and  28 ).  
      In use, straight reamer guide tube  188  is positioned within a guide tube/retractor of the present invention, with bosses  196  entering boss channels  304  formed in a proximal end thereof. Guide tube  188  is then rotated until bosses  196  are positioned beneath the lip formed by the proximal end of straight guide tube/retractor of the present invention covering the radially extending portions of boss channels  304 . In this position, guide tube  188  cannot readily be axially displaced relative to the guide tube/retractor into which it is inserted. Proximal end  198  of straight reamer  186  is actuated to provide rotational movement of reamer head  190  to form access  101  in femur  108 . After achieving a predetermined reamer depth, flange  194  contacts the proximal end of guide tube  188  to limit axial displacement of reamer head  190 . In one exemplary embodiment, straight reamer  186  is configured to provide a reaming depth of 1.9 centimeters (0.75 inches) into femur  108 .  
      Swivel reamer  202  is illustrated in detail in  FIGS. 34-38 . As illustrated in  FIGS. 34-38 , swivel reamer  202  includes swivel reamer guide tube  204  having opposing bosses  212  protruding therefrom. Swivel reamer guide tube  204  includes cutout  210  operable to allow reamer shaft  208  to pivot about swivel reamer pivot  216  as further described hereinbelow and as illustrated in  FIG. 38 . Similar to straight reamer  186 , swivel reamer  202  includes proximal end  214  operable to connect swivel reamer  202  to chuck  200  ( FIG. 7 ). Bosses  212  are utilized to connect swivel reamer  202  to a guide tube/retractor of the present invention in the same manner as bosses  196  of straight reamer  186 .  
      As illustrated in  FIG. 36 , swivel reamer pivot  216  is pivotally connected to swivel reamer guide tube  204  via pivot pins  218 . As illustrated in  FIG. 38 , swivel reamer pivot  216  is positioned about reamer shaft  218  and abuts enlarged portion  222  of swivel reamer shaft  208  and flange  220  on opposing axial ends thereof to prevent axial displacement of swivel reamer head  206 . As illustrated in  FIGS. 7 and 8  and described hereinabove, the orientation of swivel reamer  202  is changed 180 degrees to accommodate swivel reaming toward femoral head  114  as illustrated in  FIG. 7  as well as swivel reaming toward the femoral shaft as illustrated in  FIG. 8 . As illustrated, e.g., in  FIGS. 23-25  and  28 , the guide tube/retractors of the present invention includes opposing cut-outs  305  to accommodate swivel reaming toward femoral head  114  as illustrated in  FIG. 7  as well as swivel reaming toward the femoral shaft as illustrated in  FIG. 8 , without repositioning the guide tube/retractor.  
      Curved femoral head reamer  226  is illustrated in detail in  FIGS. 39 and 40 . As illustrated in  FIGS. 39 and 40 , curved femoral head reamer  226  includes guide tube  228  having bosses  236  protruding therefrom. Bosses  236  are utilized to position curved femoral head reamer  226  within a guide tube/retractor of the present invention as described above with respect to straight reamer  186  and swivel reamer  202 . Curved femoral head reamer  226  includes curved reamer shaft  232  having reamer head  230  operably connected to a distal end thereof. Proximal end  234  of curved reamer shaft  232  is operable to connect curved reamer  226  to chuck  200  of an actuation device as illustrated in  FIG. 9 . As illustrated in  FIG. 40 , curved reamer shaft  232  comprises a hollow shaft formed by outer tube  242 . Flexible driveshaft  240  is positioned within outer tube  242  and allows for transmission of rotary motion from proximal end  234  of curved reamer  226  to reamer head  230  to effect reaming into femoral head  114  as illustrated in  FIG. 9 . Flexible driveshaft  240  may include various flexible cuts, including the flexible cuts described in U.S. Pat. No. 6,053,922. Guide tube  228  of curved femoral head reamer  226  includes curved guide channel  238  for guiding movement of outer tube  242  of reamer shaft  232  as reamer head  230  is advanced into femoral head  114  as illustrated in  FIG. 9 . Curved femoral shaft reamer  242  has an identical structure to curved femoral head reamer  226  and, therefore, is not illustrated in detail for the sake of brevity. In an exemplary embodiment of the present invention, the head of curved femoral shaft reamer  242  is larger than the head of curved femoral head reamer  226 . Similarly, the head of curved femoral head reamer  226  may be larger than the head of curved femoral shaft reamer  242 . Moreover, the radius of curvature of the reamer shafts may differ between curved femoral head reamer  226  and curved femoral shaft reamer  242 . In all cases, a tubular reamer shaft and flexible driveshaft is utilized.  
      Telescoping reamer  610  illustrated in  FIGS. 97-99  may be utilized in lieu of curved femoral head reamer  226  and/or curved femoral shaft reamer  242 . While illustrated in  FIGS. 97-99  with a flex up reamer head (described below), telescoping reamer  610  may be utilized with other reaming heads including, e.g., a reaming head adapted for extending the implant cavity distally into the intramedullary canal of the femoral shaft. Referring to  FIGS. 97-99 , telescoping reamer  610  includes body  614  having detent groove  612  formed in an exterior thereof. Detent groove  612  is useful for receiving the ball detent of the ball detent retaining mechanism described below, although body  614  may include any of the mechanisms disclosed herein for positioning and/or locking an instrument into any of the guide tube/retractors of the present invention.  
      Referring to  FIG. 99 , in construction, outer extension sleeve  616  is positioned within body  614  of telescoping reamer  610 , with exterior bosses  626  of outer extension sleeve  616  positioned within internal channels  628  (only one of which is depicted in  FIG. 99 ) of body  614 . Similarly, inner extension sleeve  618  is positioned within outer extension sleeve  616 , with exterior bosses  622  of inner extension sleeve  618  positioned within internal channels  627  (only one of which is depicted in  FIG. 99 ) of outer extension sleeve  616 . Internal channels  627  and  628  of outer extension sleeve  616 , and body  614 , respectively, guide the direction and extent of relative movement between inner extension sleeve  618  and outer extension sleeve  616 , and outer extension sleeve  616  and body  614 , respectively. Both channels  627  and  628  have proximal and distal ends. When bosses  622 , and  626  are positioned adjacent the proximal ends of channels  627  and  628 , respectively, telescoping reamer  610  maintains the retracted position illustrated in  FIG. 98 . Similarly, when bosses  622  and  626  abut the distal ends of channels  627  and  628 , respectively, telescoping reamer  610  maintains the extended position illustrated in  FIG. 97 .  
      As illustrated in  FIGS. 97-99 , body  614  of telescoping reamer  610  includes a cutout accommodating the proximal end of outer extension sleeve  616  when telescoping reamer  610  maintains the retracted position illustrated in  FIG. 98 . In construction, flexible reamer shaft  606  is positioned within inner extension sleeve  618  and, consequently, within outer extension sleeve  616  and body  614 . The reamer shaft runs the length of body  614 , with straight reamer shaft  608  extending from a distal end thereof. As illustrated in  FIG. 99 , flange  624  is positioned about flexible reamer shaft  606  and spaced from the proximal portion of large diameter portion  602  of flex up reamer  600  (further described hereinbelow). In construction, interior flange  620  of inner extension sleeve  618  is positioned intermediate large diameter portion  602  of flex up reamer  600  and flange  624  extending from flexible reamer shaft  606 .  
      To extend telescoping reamer  610  from the non-extended position illustrated in  FIG. 98  to the extended position illustrated in  FIG. 97 , force F ( FIG. 98 ) having a vector component parallel to the longitudinal axis of straight reamer shaft  608  is applied to straight reamer shaft  608 , placing flange  624  in abutting relationship with interior flange  620  of inner extension sleeve  618 . As additional force is applied to straight reamer shaft  608 , the abutting relationship of flange  624  and interior flange  620  causes extension of inner extension sleeve  618  outwardly from outer extension sleeve  616  and, consequently, body  614 . Inner extension sleeve  618  extends from outer extension sleeve  616  until bosses  622  abut the distal ends of internal channels  627  of outer extension sleeve  616 . In this position, additional force applied to straight reamer shaft  608  causes extension of outer extension sleeve  616  out of body  614 . Outer extension sleeve  616  extends until exterior bosses  626  abut the distal ends of internal channels  628  of body  614 . In this position, telescoping reamer  610  is fully extended as illustrated in  FIG. 97 . Inner extension sleeve  618  and outer extension sleeve  616  may be formed with various curvatures accommodating reaming from greater trochanter  110  into femoral head  114 , as well as reaming from greater trochanter  110  into the intramedullary canal of femur  108 .  
      To retract telescoping reamer  610  from the extended position illustrated in  FIG. 97  to the non-extended position illustrated in  FIG. 98 , straight reamer shaft  608  is pulled in a generally opposite direction to force F illustrated in  FIG. 98 . When straight reamer shaft  608  is pulled in this manner, the reamer head pulls inner extension sleeve  618  into outer extension sleeve  616  until bosses  622  abut the proximal ends of internal channels  627  of outer extension sleeve  616 . In this position, additional pulling of straight reamer shaft  608  pulls outer extension sleeve  616  into body  614  until telescoping reamer  610  achieves the non-extended position illustrated in  FIG. 98 .  
      In use, telescoping reamer  610  is inserted through incision  106  and secured within a guide tube/retractor of the present invention. Telescoping reamer  610  may be utilized to form access  101  in femur  108  in lieu of straight reamer  186  illustrated in  FIG. 6 . Alternatively, straight reamer  186  may be utilized to form access  101  in femur  108  prior to insertion of telescoping reamer  610  through incision  106 . In any event, after straight reaming is complete and access  101  is formed in femur  108  as illustrated in  FIG. 6 , telescoping reamer  610  is oriented whereby extension of telescoping reamer  610  from the non-extended position illustrated in  FIG. 98  to the extended position illustrated in  FIG. 97  extends implant cavity  224 ′ into femoral head  114 , forming femoral head arm  256 ′ of implant cavity  224 ′ as illustrated in  FIG. 103 . In certain embodiments, telescoping reamer may be reoriented to extend from greater trochanter  110  into the intramedullary canal of femur  108  to form femoral shaft arm  258 ′ of implant cavity  224 ′. In such an embodiment, telescoping reamer  610  will not include a reamer head having a pair of reaming diameters as illustrated in  FIGS. 97-99 .  
      After formation of femoral cavity  224 , any remaining guide tube/retractor as well as guide plate  126  is removed and implant  260  is positioned through access  101  to be implanted in femoral cavity  224 . During implantation of implant  260 , retractors are utilized to provide access from incision  106  to access  101  formed in femur  108 . As illustrated in  FIG. 12 , bag  270  ( FIG. 41 ) is manipulated into a relatively small package positioned adjacent lag screw tube  266  before inserting implant  260  through access  101 . In one exemplary embodiment, bag  270  is accordion folded. As further illustrated in  FIG. 12 , fill tube  262  and reinforcement/expansion bar  268  of femoral implant  260  are positioned adjacent lag screw tube  266  for positioning implant  260  through access  101  and into femoral cavity  224 . When femoral implant  260  is fully inserted through access  101 , lag screw thread  282  abuts the entry to femoral head arm  256  of implant cavity  224  as illustrated, e.g., in  FIG. 13 . In this position, fill tube  262  and reinforcement/expansion bar  268  can be manipulated into the operable position illustrated in  FIG. 14 . In this position, bag  270  extends into femoral shaft arm  258  of implant cavity  224 .  
      After implant  260  is positioned as illustrated in  FIG. 13 , a flexible drive device is utilized to advance lag screw  264  into femoral head  114  until reaching the terminal position illustrated in  FIG. 14 . With lag screw  264  firmly implanted in femoral head  114 , pump P is utilized to convey a bag fill material for filling bag  270  from source of bag fill  284  through fill tube  262 . In one exemplary embodiment, source of bag fill  284  comprises a source of bone cement. Fill tube  264  is formed to provide for retrograde filling of bag  270 . As bag  270  is filled with, e.g., bone cement, it expands to fill femoral cavity  224 , including, femoral shaft arm  258  thereof. Once bag  270  is filled, the bone cement injected therein cures and provides intramedullary fixation of femoral implant  260 . As indicated above, in a further embodiment of the present invention, the bag structure of the implant of the present comprises a nested bag structure in which an inner bag is filled with a high strength material relative to an outer bag in which the inner bag is placed. The outer bag of this form of the present invention is formed from and filled with a more bioresorbable material relative to the material of construction and fill material of the inner bag.  
      Implant  260  is illustrated in detail in  FIG. 41 . As illustrated in  FIG. 41 , bag  270  is secured to lag screw tube  266  to prevent material inserted into bag  270  from escaping between the contact points formed between bag  270  and lag screw tube  266 . As further illustrated in  FIG. 41 , reinforcement/expansion bar  268  is positioned to facilitate deployment of implant  260  into femoral shaft arm  258  of femoral cavity  224  as described hereinabove. Reinforcement/expansion bar  268  will not be utilized in every embodiment of the present invention. As illustrated in  FIG. 43 , reinforcement/expansion bar  268  also functions to laterally spread bag  270  to facilitate placement of bone cement therein. As illustrated in  FIG. 41 , fill tube  262  is positioned within bag  270 , with bag  270  securely affixed to a proximal end thereof.  
       FIG. 90  illustrates alternative embodiment femoral implant  260 ′. Femoral implant  260 ′ is generally identical to femoral implant  260  illustrated in  FIG. 41  except for the provision of external fasteners  279  utilized to securely affix bag  270 ′ to lag screw tube  266 . Although not illustrated in  FIG. 90 , it is contemplated that femoral implant  260 ′ will include a fill tube  262 ′ for filling bag  270  with bone cement. Bag  270  of femoral implant  260  can be, e.g., formed of various films and fabrics. In one exemplary embodiment, bag  270  is formed from an acrylic material, e.g., a woven acrylic material. Because bone cement is an acrylic, if implant bag  270  is formed of an acrylic material, implant bag  270  and the bone cement will achieve an intimate chemical bond. Implant bag  270  of femoral implant  260  of the present invention generally comprises a containment device and can be constructed of various materials including films such as, e.g., fiber or fabric reinforced films, or fabrics created by processes such as weaving, knitting, braiding, electrospinning, or hydrospinning. Alternative materials contemplated for implant bag  270  include various polymers including, e.g., polymethylmethacrylate, polycarbonate, UHMWPE, LDPE, HDPE, polyamides, polypropylene, polyester, polyaryletherketone, polysulfone, or polyurethane. Further alternative materials contemplated for implant bag  270  include fabrics constructed of fibers formed of glass, ceramics, surgical grade stainless steel (e.g., 316L), titanium, or titanium alloys. Moreover, implant bag materials may be coated with, e.g., calcium phosphate, or a bioactive glass coating. Furthermore, implant bag  270  and the associated filler may be utilized as a delivery mechanism for, e.g., drugs, or growth factors.  
      Alternative embodiments of the lag screw of the present invention are illustrated in  FIGS. 42, 91 , and  92 . As illustrated in  FIG. 42 , lag screw  264  generally comprises curved lag screw shaft  274  rotatably connected to lag screw head  272 . In the embodiment illustrated in  FIG. 42 , lag screw shaft  274  includes distal male threads  276  cooperating with proximal female threads  278  formed in lag screw head  272 . Mating threads  276 ,  278  are left handed threads. Lag screw head  272  includes chamber  280  to accommodate distal threaded end  276  of lag screw shaft  274  when lag screw head  272  is operably positioned on lag screw shaft  274 . Lag screw head  272  includes distal lag screw threads  282  for implanting lag screw  264  into femur  108  as described hereinabove. Cooperating threads  276 ,  278  are left handed threads, while lag screw threads  282  are right handed threads. In this way, lag screw head  272  may be threadedly engaged on lag screw shaft  274  and, rotation of lag screw head  272  in a clockwise fashion to effect implantation of lag screw threads  282  into femur  108  will not cause lag screw head  272  to become separated from lag screw shaft  274 .  
       FIG. 91  illustrates alternative embodiment lag screw  264 ′ in which lag screw head  272  includes flange  277  and lag screw shaft  274  includes bearing protrusion  275 . In this embodiment, bearing protrusion  275  is positioned intermediate the most proximal portion of lag screw head  272 ′ and flange  277 . In this arrangement, flange  277  cooperates with the most proximal portion of lag screw head  272  and bearing protrusion  275  to prohibit axial displacement of lag screw head  272 ′. Lag screw head  272 ′ includes male hex  273 ′ operable for connection to flexible drive  281  as illustrated in  FIG. 91 . In use, flexible drive  281  will be inserted within tubular lag screw shaft  274  and engaged with male hex  273 ′ to rotate lag screw head  272  to effect implantation thereof. In the embodiment illustrated in  FIG. 42 , lag screw shaft  274  is similarly cannulated to allow a flexible drive to enter lag screw shaft  274  and engage a cooperating protrusion (not shown) formed on lag screw head  272 .  FIG. 92  illustrates an alternative embodiment of lag screw head  272 ″ wherein male threads  276 ″ are formed on lag screw head  272 ″, and female threads  278 ′ are formed in lag screw shaft  274 .  
      Alternative embodiments of guide plate  126  are illustrated in  FIGS. 50-55 , and  65 - 68 . Referring now to  FIGS. 50-55 , guide plate  126 ′ includes screw apertures  286 ′ for use in securing guide plate  126  to femur  108  as described hereinabove with respect to guide plate  126 . Guide plate  126 ′ further includes spring pins  318  traversing axially oriented apertures in guide plate  126 ′. As illustrated in  FIG. 55 , spring pins  318  engage alternate ends of springs  316  to hold springs  316  in position within guide plate  126 ′. As illustrated in  FIG. 51 , guide plate  126 ′ includes circular opening  322  as well as elliptical opening  324 , with springs  316  extending into circular opening  322 . In one exemplary embodiment, springs  316  are formed from titanium.  
      Referring now to  FIGS. 65-68 , guide plate  126 ″ includes axially oriented apertures accommodating spring pins  318 ″ in much the same way as guide plate  126 ′ illustrated in  FIGS. 50-55 . Spring pins  318 ″ are utilized to hold springs  316 ″ in position within guide plate  126 ″ as illustrated with respect to guide plate  126 ′ in  FIG. 55 . Guide plate  126 ″ includes circular opening  322 ″ as well as elliptical opening  324 ″ similar to the corresponding openings found in guide plate  126 ′. The distal end of guide plate  126 ″ includes gripping teeth  404  formed thereon. Additionally, guide plate  126 ″ includes fixation screw shoulder  406  as illustrated, e.g., in  FIG. 67 . Fixation screw shoulder  406  will be further described hereinbelow.  
      In use, guide plate  126 ′ is inserted through incision  106  for affixation to femur  108  in the same manner as guide plate  126  described hereinabove. Insertion member  124 ′ illustrated in  FIGS. 83-86  is utilized to position guide plate  126 ′ through incision  106  for placement atop greater trochanter  110 . In many respects, insertion instrument  124 ′ is similar to insertion instrument  124  illustrated in  FIGS. 19-22  and further described hereinabove. As illustrated in  FIGS. 83-86 , insertion instrument  124 ′ includes elongate aperture  132 ′ for accommodating stabilization nail  144  ( FIG. 2 ). Insertion member  124 ′ includes release member  134 ′ connected via connecting rods  348 , and cylindrical connector  352  to release bars  350 . Release bars  350  travel in axially oriented slots formed in the distal end of insertion member  124 . The distal end of insertion member  124 ′ includes elliptical protrusion  354  for placement within elliptical aperture  324  of guide plate  126 ′. Cooperation of elliptical protrusion  354  with elliptical aperture  324  insures proper rotational alignment of insertion member  124 ′ and guide plate  126 ′. Upon achieving proper rotational alignment, insertion member  124 ′ may be axially displaced into the central aperture of guide plate  126 ′, with springs  316  engaging spring slots  326 ″ formed in opposing sides of the distal end of insertion member  124 ′. In this way, springs  316  lock guide plate  126 ′ to insertion member  124 ′. Bevel  317  facilitates positioning of springs  316  in spring slots  326 ″. After guide plate  126 ′ is secured to femur  108  as described hereinabove with respect to guide plate  126 , release bars  350  are utilized to actuate springs  316  radially outwardly from their normally biased position to disengage spring slots  326 ″ and allow for removal of insertion member  124 ′ from guide plate  126 ′.  
      Release member  134 ′ is utilized to effect axial displacement of release bars  350  from the position illustrated in  FIG. 85  in which spring slots  326 ″ are available for engagement with springs  316  to the position illustrated in  FIG. 84  in which release bars  350  provide a radially outward force to springs  316  to allow for disengagement of insertion member  124 ′ from locking engagement with guide plate  126 ′ and allow for removal of insertion member  124 ′ through incision  106 . As illustrated in  FIG. 85 , release bars  350  include a distal bevel to facilitate movement from the position illustrated in  FIG. 85  to the position illustrated in  FIG. 84  to effect release of springs  316  from spring slots  326 ″. Similarly, insertion member  124 ′ can be lockingly engaged with guide plate  126 ″ illustrated in  FIGS. 65-68  to effect implantation of guide plate  126 ″ through incision  106  for placement atop greater trochanter  110 .  
      When utilizing guide plate  126 ″ illustrated in  FIGS. 65-68 , plunge reamer  480  ( FIG. 82 ) must first be utilized to form a cavity in femur  108  extending through greater trochanter  110 . Plunge reamer  480  includes reamer head  484  and flange  482 . In this embodiment, plunge reamer  480  is inserted through incision  106  and reamer head  484  is placed atop greater trochanter  110 . As with initial placement of guide plate  126  and  126 ′, a fluoroscope may be utilized to facilitate proper positioning of reamer head  484  atop greater trochanter  110 . Furthermore, a surgeon may rely on tactile feedback for proper positioning of plunge reamer  480 . Plunge reamer  480  is actuated and plunge reaming is effected until flange  482  abuts greater trochanter  110 . Plunge reamer  480  is thereafter removed through incision  106  to allow for placement of guide plate  126 ″ atop greater trochanter  110 . Fixation screw  394  illustrated in  FIGS. 61-64  is thereafter utilized to secure guide plate  126 ″ to greater trochanter  110 . While insertion instrument  124 ′ may be utilized to initially position guide plate  126 ″ through incision  108 , it must be removed prior to implantation of fixation screw  394 .  
      As illustrated in  FIGS. 61-64 , fixation screw  394  includes fixation screw head  398  with fingers  396  axially depending therefrom. Screw threads  400  are formed on axially extending fingers  396 . The proximal end of fixation screw  394  includes locking channel  402 , the utility of which will be further described hereinbelow. Fixation screw head  398  forms a flange engagable with fixation screw shoulder  406  formed in guide plate  126 ″ ( FIG. 67 ). Fixation screw  394  is inserted through the central aperture of guide plate  126 ″ and is screwed into the bore formed through greater trochanter  110  to secure guide plate  126 ″ atop greater trochanter  110 . Threads  400  cut into the femoral bone stock to provide fixation of fixation screw  394 .  
      Fixation screw placement instrument  470  as illustrated in  FIGS. 80 and 81  is utilized to insert fixation screw  394  through incision  106  and to secure fixation screw  394  within guide plate  126 ″ as described hereinabove. Referring now to  FIGS. 80 and 81 , fixation screw placement instrument  470  includes a proximal handle as well as a distal end having blades  466  and ball detent  464  formed therein. In use, blades  466  engage locking channels  402  in fixation screw  394 , with ball detent  464  engaging a detent (not shown) formed in the inner diameter of locking screw  394 . The proximal handle of fixation screw placement instrument  470  may then be utilized to rotate fixation screw  394  and secure the same within femur  108 .  
      When utilizing either guide plate  126 ′ ( FIGS. 50-55 ) or guide plate  126 ″ ( FIGS. 65-68 ), alternative embodiment guide tube/retractor  154 ′ is utilized in lieu of guide tube/retractor  154  described hereinabove with reference to guide plate  126 . Guide tube/retractor  154 ′ is illustrated in  FIGS. 56, 57 ,  59 , and  60 . As illustrated, guide tube/retractor  154 ′ includes a distal end having rounded portion  330  with spring slots  326  formed on opposing sides thereof. Furthermore, distal end of guide tube/retractor  154 ′ includes engagement protrusions  328  having a radius of curvature matching the rounded ends of elliptical openings  324  and  324 ″ in guide plates  126 ′ and  126 ″, respectively. Opposing spring slots  326  formed in the distal end of guide tube/retractor  154 ′ are utilized to selectively affix guide tube/retractor  154 ′ to either guide plate  126 ′ or  126 ″ in the same fashion as described above with respect to insertion member  124 ′. As illustrated in  FIG. 58 , angled guide tube/retractor  296 ′ is provided for use with guide plates  126 ′ or  126 ″. Angled guide tube/retractor  296 ′ provides the same functionality as angled guide tube/retractor  296  described hereinabove with respect to guide plate  126  and includes a distal end identical to the distal end of straight guide tube/retractor  154  illustrated in  FIGS. 56, 57 ,  59 , and  60 . Straight guide tube/retractor  154 ′ and angled guide tube/retractor  296 ′ have a greater axial length than straight guide tube/retractor  154  and angled guide tube/retractor  296  described in the primary embodiment of the present invention. The inventors of the present invention contemplate various guide tube/retractors having differing lengths to accommodate physiological differences in a variety of patients as well as different attaching mechanisms in accordance with the various embodiment of the present invention. As illustrated in  FIGS. 56-60 , guide tube/retractors  154 ′ and  296 ′ include latch channels  332  and  332 ′, respectively. The utility of latch channels  332  and  332 ′ will be further described hereinbelow.  
      Referring now to  FIGS. 44 and 45 , alignment device  156 ′ is utilized in conjunction with guide tube/retractors  154 ′,  296 ′ to select the appropriate guide tube/retractor as described hereinabove with respect to alignment device  156 . Alignment device  156 ′ includes alignment guide tube  306  for positioning within guide tube/retractor  156 ′, or angled guide tube/retractor  296 ′ and providing a stable base for alignment device  156 ′ as described above with respect to insertion portion  160  of alignment device  156  ( FIGS. 29 and 30 ). Alignment guide tube  306  includes latch  308  pivotally connected thereto via pivot pin  314 . Additionally, alignment guide tube  306  includes distal flat  386  which, in this exemplary embodiment will bottom out on the shoulder formed between the elliptical aperture and a round aperture in guide plates  126 ′ and  126 ″. Latch  308  includes oppositely depending locking tabs  310  extending from opposing sides thereof. Latch  308  is biased into the position illustrated in  FIG. 45  by spring  312 . As alignment guide tube  306  is inserted into guide tube/retractor  156 ′ or  296 ′, locking tabs  310  contact the proximal end of guide tube/retractor  154 ′ or  296 ′. After achieving this position, the distal end of latch  308  is depressed radially inwardly to move locking tabs  310  away from alignment guide tube  306  and allow for further insertion of alignment guide tube  306  into guide tube/retractor  154 ′ or angled guide tube/retractor  296 ′. As indicated above, distal flat  386  bottoms out on the shoulder formed between the elliptical and the round apertures in guide plates  126 ′ and  126 ″ when alignment guide tube  306  is fully inserted into guide tube/retractor  154 ′ or  296 ′. In this position, locking tabs  310  align with latch channels  332  ( FIGS. 56-58 ) and latch  308  can return to its normally biased position as illustrated in  FIG. 45 . In this position, locking tabs  310  engage latch channels  332  to prevent axial displacement of alignment guide tube  306  relative to guide tube/retractor  154 ′ or  296 ′. Furthermore, when engaged in latch channels  332 , locking tabs  310  resist rotational movement of alignment guide tube  306 . In all other respects, alignment device  156 ′ is identical to alignment device  156  described above and is utilized in a similar fashion to choose between straight guide tube/retractor  154 ′ and angled guide tube/retractor  296 ′.  
      Reaming of femoral cavity  224  is effected with reamers having guide tubes and latches similar to guide tube  306  and latch  308  described above with respect to alignment device  156 ′. In one alternative embodiment, combination reamer  358  illustrated in  FIGS. 46-49  is utilized to effect both plunge, i.e., straight reaming into the femur as well as swivel reaming. In this embodiment, combination reamer  358  is inserted into guide tube/retractor  154 ′ or  296 ′, with orientation plate  384  cooperating with one of the longitudinal channels formed in guide tube/retractor  154 ′ or  296 ′ (see, e.g.,  FIGS. 56-60 ) to properly align combination reamer  358  within the guide tube/retractor. As illustrated in  FIGS. 46-49 , combination reamer  358  includes reamer head  360  connected to the distal end of reamer shaft  362 . Reamer shaft  362  includes flange  364  positioned toward the distal end thereof and ratchet teeth  382  formed toward the proximal end thereof. As illustrated in  FIG. 49 , reamer shaft  362  is positioned within reamer shaft tube  372  having reamer depth lock  374  formed on a proximal end thereof. Reamer depth lock  374  includes ratchet release  376  connected via connecting rod  378  to ratchet head  380  as illustrated in  FIG. 49 . As illustrated in  FIG. 49 , a spring is utilized to bias ratchet head  380  into engagement with ratchet teeth  382  on reamer shaft  362 . Ratchet release  376  is pivotally connected to reamer depth lock  374  such that actuation of ratchet release  376  causes outward radial movement of ratchet head  380  with respect to reamer shaft  362 , thus disengaging the ratchet teeth formed in ratchet head  380  from ratchet teeth  382  and allowing for relative axial movement of reamer shaft tube  372  and reamer shaft  362 . In the configuration illustrated in  FIG. 49 , combination reamer  358  can be utilized to effect plunge reaming, with the terminal reaming depth being reached when the distal end of reamer shaft tube  362  contacts pivot  216 . The overall depth of plunge reaming may thus be adjusted by varying the axial displacement of reamer depth lock  374  along reamer shaft  362 .  
      As illustrated in  FIG. 46 , combination reamer  358  includes combination reamer guide tube  366  having channel  368  formed therein. Swivel/plunge reaming selector  370  is operably connected to a proximal end of combination reamer guide tube  366 . As illustrated in  FIG. 49 , rotation guide pin  388  is fixably secured to combination reamer guide tube  366  and positioned within rotation guide channel  390  of swivel/plunge reaming selector  370 . Swivel/plunge reaming selector  370  may be rotated about guide tube  366  of combination reamer  358  between the extremes illustrated in  FIGS. 47 and 48 , i.e. with rotation guide pin  388  abutting opposite ends of rotation guide channel  390 . When swivel/plunge reaming selector  370  is positioned as illustrated in  FIG. 47 , swivel reaming with combination reamer  358  is not allowed because swivel/plunge reaming selector  370  covers channel  368 . To allow for swivel reaming, swivel/plunge reaming selector  370  is rotated into the position illustrated in  FIG. 48 . In the position illustrated in  FIG. 48 , channel  392  in swivel/plunge reaming selector  370  aligns with channel  368  in guide tube  366  of combination reamer  358 . In this position, swivel reaming can be effected as illustrated in  FIG. 48 . Reamer shaft  362  is connected to guide tube  366  of combination reamer  358  via pivot  216 ′ and pivot pins  218 ′ to allow for the swivel reaming illustrated in  FIG. 48 . Combination reamer  358  includes distal flat  386 ′ for signaling complete insertion of combination reamer  358  into reamer/guide tube  154 ′ or  296 ′. As described above with respect to alignment guide tube  306  of alignment device  156 ′, distal flat  386 ′ bottoms out on the shoulder formed between the elliptical and round apertures in guide plates  126 ′ and  126 ″ when combination reamer  358  is fully inserted into guide tube/retractor  154 ′ or  296 ′.  
      Upon completion of femoral reaming, guide tube/retractor  156 ′ or  296 ′ is removed from locked engagement with guide plate  126 ′ or  126 ″ with spring lock release instrument  336  illustrated in  FIGS. 87-89 . As illustrated in  FIGS. 87-89 , spring lock release instrument  336  includes a tubular body sized for insertion into guide tube/retractor  156 ′ or  296 ′ with a distal shoulder indicating complete insertion of spring lock release instrument  336  into guide tube/retractor  156 ′ or  296 ′ in the manner described above with respect to alignment guide tube  306  of alignment device  156 ′, and combination reamer  358 . Moreover, spring lock release instrument  336  includes latch  308 ′ as described hereinabove with respect to guide tube  306  of alignment device  156 ′. After insertion of spring lock release instrument  336  into guide tube/retractor  156 ′ or  296 ′, handle  338  is utilized to axially displace actuation rod  342  traversing internal aperture  344  of spring lock release instrument  336  into the position illustrated in  FIG. 89 . In this position, the distal ramped end of actuation rod  342  contacts the proximal ends of release pins  346  to overcome the biasing force of springs  347  ( FIG. 88 ) and cause release pins  346  to protrude from spring lock release instrument  336  as illustrated in  FIG. 89 . In this position, release pins  346  traverse apertures  155 ,  155 ′ and act against springs  316  to disengage springs  316  from spring slots  326  and allow for removal of guide tube/retractor  154 ′ or  296 ′. In the embodiment illustrated, release pins  346  are spring biased. The inventors of the current invention contemplate that release pins  346  could be linked to actuation rod  346  via a mechanical linkage whereby pulling actuation rod  342  would pull pins  346  into the instrument and, conversely, pushing rod  342  would push the pins outwardly from the instrument. Moreover, while release pins  346  are illustrated as forming an acute angle with the longitudinal axis of spring lock release instrument  336 , release pins  346  could be transversely positioned within spring lock release instrument  336 .  
      Guide tube/retractor  156 ″ in accordance with a further alternative embodiment of the present invention is illustrated in  FIGS. 69 and 70 . In this embodiment, guide tube/retractor  154 ″ is configured for affixation directly to greater trochanter  110 , with guide plate  126  no longer being used. As illustrated in  FIGS. 69 and 70 , guide tube/retractor  154 ″ includes gripping teeth  404 ″ formed in a distal end thereof. In use, gripping teeth  404 ″ are positioned atop greater trochanter  110  and fixation screw  394  is positioned within guide tube/retractor  154 ″ and utilized to affix guide tube/retractor  154 ″ to femur  108  as described above with reference to guide plate  126 ″. While not illustrated in  FIGS. 69 and 70 , guide tube/retractor  154 ″ includes a shoulder for engaging screw head  398  of fixation screw  394  to complete fixation of guide tube/retractor  154 ″ to femur  108  in the same manner as described above with respect to guide plate  126 ″.  
       FIGS. 107-109  illustrate another alternative embodiment guide/retractor in accordance with the present invention. Specifically,  FIGS. 107-109  illustrate unitube retractor  700 . Unitube retractor  700  functions as the guide tube/retractors described above to maintain an access from incision  106  ( FIG. 1 ) made in the epidermis of patient  100  and developed to expose femur  108 . Unitube retractor  700  is referred to as a “unitube” retractor because it is designed to be directly secured to femur  108 , without use of a discrete guide plate or fixation screw. To effect fixation of unitube retractor  700  to femur  108 , unitube retractor  700  includes self-tapping threads  702 . Self-tapping threads  702  are formed on the distal end of unitube body  706 , with cutouts  704  formed in and spaced about the periphery of the distal end of unitube body  706  to facilitate tapping of threads in femur  108  as unitube retractor  700  is threaded into engagement with femur  108  through access  101  described above. In an alternative embodiment, unitube retractor  700  will not include self-tapping threads, but rather will include threads that do not self-tap. In this embodiment, a discrete tap will be used to thread into access  101  in femur  108  prior to securement of unitube retractor  700  therein.  
      As illustrated in  FIGS. 107-109 , unitube body  706  includes a longitudinal slot to cooperate with guide tabs protruding from instruments to be inserted through unitube body  706  to properly align the instruments prior to use. The longitudinal slot formed in unitube body  706  will also accommodate the swivel reaming of certain embodiments of the present invention. In use, unitube retractor  700  will be inserted through incision  106  until the distal end abuts greater trochanter  110 . In this position, a surgeon will utilize tactile feedback to position the distal end of unitube retractor  700  in access  101  formed in greater trochanter  110 . In one exemplary embodiment, a fluoroscope will be utilized to facilitate positioning of the distal end of unitube retractor  700  in access  101  formed in greater trochanter  110 . In this position, unitube retractor  700  will be threaded into access  101  in femur  108 , with self-tapping threads  702  threading access  101  to secure unitube retractor  700  therein. Threading of unitube retractor  700  is complete when unitube retractor  700  is secured in access  101  and the longitudinal slot of unitube body  706  is aligned with an appropriate physiological landmark to guide alignment of instruments inserted therein. For example, a central axis of the longitudinal slot of unitube body  706  may be positioned substantially perpendicular to the plane of the greater trochanter and generally aligned with the axis of the femoral shaft.  
      As illustrated in  FIGS. 107-109 , unitube retractor  700  includes a ball detent retaining mechanism for retaining instruments inserted therein in a fixed longitudinal position relative to unitube body  706 . The ball detent retaining mechanism cooperates with the longitudinal alignment slot of unitube body  706  to fix instruments positioned in unitube retractor  700  and prevent relative rotational and axial displacement of an instrument positioned in unitube retractor  700 . Referring to  FIGS. 107-109 , ball detent  716  is received by counterbored ball detent aperture  720 . Counterbored ball detent aperture  720  is formed from the exterior of unitube body  706  to the hollow interior thereof such that the largest diameter portion of counterbored ball detent aperture  720  is formed in the exterior wall of unitube body  706 . Counterbored ball detent aperture  720  is sized whereby the smallest diameter portion thereof, i.e., the portion formed in the hollow interior of unitube body  706  is smaller than the equator of ball detent  716 . With this structure, ball detent  716  cannot traverse counterbored ball detent aperture.  
      Ball detent  716  is interposed between plunger  712  and unitube body  706 . As illustrated in  FIG. 110 , plunger  712  includes internal ball detent ramp  713  connecting base flat  711  and peak flat  715 .  FIG. 107  illustrates the ball detent retaining mechanism of unitube retractor  700  positioned to retain an instrument within unitube retractor  700 , with ball detent  716  protruding into the hollow interior of unitube body  706 . In this position, ball detent  716  contacts peek flat  715  ( FIG. 110 ) of plunger  712 , which forces ball detent  716  to protrude into the hollow interior of unitube body  706 .  FIG. 108  illustrates the ball detent retaining mechanism of unitube retractor  700  actuated to allow for release of an instrument positioned within unitube retractor  700 , with ball detent  716  not protruding into the hollow interior of unitube body  706 . In this position, ball detent  716  contacts base flat  711  ( FIG. 110 ) of plunger  712 , which allows ball detent  716  to retract from the hollow interior of unitube body  706 . As illustrated in  FIG. 108 , force F is applied to flange  714  of plunger  712  to reposition plunger  712  from its normally biased position illustrated in  FIG. 107  to the position illustrated in  FIG. 108 .  
      To bias plunger  712  into the position illustrated in  FIG. 107 , springs  724  ( FIG. 109 ) are positioned intermediate plunger  712  and collar  708 . Collar  708  includes internal collar flange  718  as illustrated in  FIG. 107-109 . In construction, collar  708  is secured to unitube body  706  with set screws  710  positioned through set screw apertures  722  (only one of which is illustrated in  FIG. 109 ) in collar  708  and secured in set screw apertures  741  in unitube body  706 . Springs  724  are positioned in spring slots  726  (only one of which is illustrated in  FIG. 109 ) on opposing sides of unitube body  706 , with the distal ends of springs  724  abutting internal collar flange  718  and distal end  728  of spring slots  726 . Spring slots  726  maintain the position of springs  724  substantially parallel to the longitudinal axis of unitube body  706 . In one exemplary embodiment, internal collar flange  718  of collar  708  includes circular cutouts aligned with spring slots  726  to further facilitate alignment of springs substantially parallel to the longitudinal axis of unitube body  706 . Plunger  712  is positioned over the proximal end of unitube body  706  such that springs  724  are interposed between internal collar flange  718  of collar  708  and the distal end of plunger  712 . Plunger  712  includes at least one set screw aperture  731  and unitube body  706  includes at least one corresponding set screw slot  730 . To complete assembly of unitube retractor  700 , set screws  732  are threaded into set screw apertures  731  in plunger  712  and extend into set screw slots  730  in unitube body  706 . Set screws  732  cooperate with set screw slots  730  to limit displacement of plunger  712  to longitudinal movement only. In the normally biased position illustrated in  FIG. 107 , set screws  732  abut the proximal end of set screw slots  730 . In use, ball detent  716  engages a detent formed in an instrument inserted into unitube retractor  700  to retain the instrument in a fixed position relative to unitube retractor  700 .  
      Referring to  FIGS. 111-115 , alternative embodiment unitube retractor  700 ′ is illustrated. Unitube retractor  700 ′ includes a ball detent retaining mechanism as described above with respect to unitube retractor  700 , with corresponding parts denoted with primed reference numerals. The ball detent retaining mechanism of unitube retractor  700 ′ is structured and operates substantially identical to the ball detent retaining mechanism described above with respect to unitube retractor  700  and, therefore, a detailed description of this mechanism will not now be repeated for the sake of brevity.  
      Unitube retractor  700 ′ utilizes instrument alignment cutouts in unitube body  706  as opposed to the longer longitudinal slot of unitube body  706 . Also, collar  708 ′ and plunger  712 ′ do not include cutouts corresponding to instrument alignment cutouts in unitube body  706 , unlike collar  708  and plunger  712  of unitube retractor  700 . With this in mind, the instrument alignment tabs associated with the instruments to be positioned in unitube retractor  700 ′ will not protrude past the exterior wall of unitube body  706 ′. Similar alignment tabs, could be used with unitube retractor  700 , allowing use of plunger  712 ′ and collar  708 ′ with unitube  700 . Similarly, plunger  712  and collar  708  could be used with unitube retractor  700 ′ if the alignment tabs of the instruments to be inserted in unitube retractor  700 ′ extend past the exterior wall of unitube body  706 ′. Unitube body  706 ′ includes a pair of opposing instrument alignment cutouts allowing 180° of instrument realignment, which would necessitate a pair of corresponding cutouts in plunger  712  and collar  708 , if used with unitube retractor  700 ′. If a pair of cutouts are required in the plunger and collar, then the plunger and collar will either be constructed in two pieces, or the cutouts will not run the entire length of the plunger and collar as do the cutouts of plunger  712  and collar  708  illustrated in  FIGS. 107-109 .  
      Unitube retractor  700 ′ employs lock ring  742  to secure unitube retractor  700 ′ in access  101  formed in femur  108  as described above. Lock ring  742  includes a number of expandable fingers  744  as illustrated in  FIGS. 113-115 . In use, unitube retractor  700 ′ is inserted through incision  106  until fingers  744  abut greater trochanter  110 . In this position, a surgeon will utilize tactile feedback to position the distal end of unitube retractor  700 ′ in access  101  formed in greater trochanter  110 . In one exemplary embodiment, a fluoroscope will be utilized to facilitate positioning of the distal end of unitube retractor  700 ′ in access  101  formed in greater trochanter  110 . After insertion of unitube retractor  700 ′ into access  101  and alignment of instrument alignment cutouts  756  with an appropriate physiological landmark such as, the longitudinal axis of the femur, fingers  744  are expanded from the position illustrated in  FIG. 113  to the position illustrated in  FIGS. 114 and 115  to secure unitube retractor  700 ′ in femur  108 .  FIGS. 111 and 112  illustrate alternative embodiment lock ring  742 ′ having teeth  748  radially extending from fingers  744  to facilitate locking of lock ring  742 ′ in femur  108 .  
      As illustrated in  FIG. 112 , each finger  744 ′ of lock ring  742 ′ includes internal ramp  749 . Although not illustrated, each finger  744  of lock ring  742  similarly includes an internal ramp. As illustrated in  FIG. 111 , unitube body  706 ′ includes beveled distal end  746 . In the unactuated position of unitube retractor  700 ′ as illustrated in  FIG. 113 , beveled distal end  746  of unitube body  706 ′ abuts internal ramps  749  of fingers  744 . To actuate fingers  744  from the position illustrated in  FIG. 113  to the position illustrated in  FIG. 114  to effect locking of unitube retractor  700 ′ to femur  108 , unitube body  706 ′ is longitudinally displaced toward lock ring  742 , with beveled distal end  746  of unitube body  706 ′ cooperating with internal ramps  749  of expandable fingers  744  to force expandable fingers  744  to move radially outwardly as illustrated in  FIGS. 114 and 115 .  
      A number of mechanisms may be employed to effect the necessary longitudinal displacement of unitube body  706 ′ relative to lock ring  742 .  FIGS. 111, 113 , and  114  illustrate one such mechanism. As illustrated in  FIGS. 111, 113 , and  114 , threaded driver  736  is rotationally connected to unitube body  706 ′ via set screw  738 . Specifically, set screw  738  is threaded into set screw aperture  739  of threaded driver  736  and extends into annular threaded driver rotation groove  752  formed in unitube body  706 ′. In this way, threaded driver  736  may rotate relative to unitube body  706 ′, but may not be longitudinally displaced relative to unitube body  706 ′. Connector shaft  734  is positioned about unitube body  706 ′ and is threaded to threaded driver  736 . After connector shaft  734  is positioned about unitube body  706 ′, a set screw is threaded into set screw aperture  750  of connector shaft  734  and extends into guide slot  754  formed in unitube body  706 ′ to restrict relative movement between connector shaft  734  and unitube body  706 ′ to axial movement only. Connector shaft  734  is further threaded to lock ring  742 , although, in an alternative embodiment, lock ring  742  could be secured to connector shaft  734  via any one of a number of connectors including, e.g., one or more set screws. In the position illustrated in  FIG. 113 , connector shaft  734  is threaded into threaded driver a sufficient distance to place beveled distal end  746  ( FIG. 111 ) of unitube body  706 ′ in abutting relationship with the internal ramps of expandable fingers  744  of lock ring  742 . To actuate unitube retractor into the position illustrated in  FIG. 114 , connector shaft  734  is held stationary, while threaded driver  736  is rotated to continue threading connector shaft  734  into threaded driver  736  and thereby force unitube body  706 ′, which cannot be longitudinally displaced relative to threaded driver  736 , further into lock ring  742 , whereby beveled distal end  746  of unitube body  706 ′ cooperates with internal ramps  749  of expandable fingers  744  to force expandable fingers  744  into the position illustrated in  FIG. 114 . Specifically, set screw  738  acts against threaded driver rotation groove  752  to force unitube body  706 ′ further into lock ring  742  as connector shaft  734  is threaded into threaded driver  736 .  
      In an alternative embodiment of the present invention, flexible reamer  428  illustrated in  FIGS. 75 and 76  is utilized in lieu of the curved reamers described above to ream into femoral head  114  and into the shaft of femur  108 . As illustrated in  FIGS. 75 and 76 , flexible reamer  428  includes reaming head  432  and flexible reaming shaft  434 . As illustrated in  FIG. 76 , flexible reaming shaft  434  is cannulated, allowing for insertion of flexible reamer shaft  434  over a guide wire to guide reaming into femoral head  114  and into the shaft of the femur  108 . Flexible reamer  428  illustrated in  FIGS. 75 and 76  utilizes flexible reamer guide tube  430  and a latch member associated with a particular reamer/guide tube of the present invention. However, flexible reamer  428  may include various guide tubes having physical characteristics allowing for use of flexible reamer  428  with the various guide tube/retractors of the present invention. As illustrated in  FIGS. 75 and 76 , the proximal end of flexible reamer shaft  434  is connected to flange  436  which acts against the proximal end of flexible reamer guide tube  430  to limit the reaming depth of flexible reamer  428 .  
      In one exemplary embodiment, flexible reamer guide  408  ( FIGS. 71 and 72 ) is utilized to position guide wire  410  within the femur to guide flexible reamer  428 . As illustrated in  FIGS. 71 and 72 , flexible reamer guide  408  includes guide  416  having guide shaft fixation channel  412  formed therein. Guide  416  is insertable within guide channel  420  of the main body of flexible reamer guide  408  as illustrated in  FIG. 72 . Guide pegs  418  depend from guide  416  and are further inserted within guide channel  420  as illustrated in  FIG. 72 . Flexible reamer guide tube  486  of flexible reamer guide  408  includes advance/retract screw aperture  488  and guide wire aperture  490 . With guide  416  inserted in guide channel  420  of flexible reamer guide tube  486 , guide wire  410  is inserted in guide wire aperture  490  and positioned within guide shaft fixation channel  412 . Set screw  414  is utilized to secure guide wire  410  within guide shaft fixation channel  412 . Advance/retract screw  422  traverses a proximal aperture in guide  416  and advance/retract screw aperture  488 , and is threadably engaged with receiving block  426  as illustrated in  FIG. 72 . Advance/retract screw  422  includes flange  424  for abutting the proximal end of guide  416  and for forcing guide  416  to be distally displaced in flexible reamer guide tube  486  in response to distal movement of advance/retract screw  422 . Guide wire  410  is formed from a memory metal such as, e.g., NITINOL. With this in mind, advance/retract screw  422  may be retracted from receiving block  426  to allow guide wire  410  to retreat into guide wire aperture  490  to completely retract guide wire  410  within flexible reamer guide tube  486  of flexible reamer guide  408 , without losing the ability of guide wire  410  to regain the bent shape illustrated in  FIG. 71 .  
      In use, flexible reamer guide  408  is inserted within a guide tube/retractor of the present invention with guide wire  410  not protruding from the distal end of guide wire aperture  490 . The proximal end of advance retract screw  422  is thereafter actuated to force guide  416  and, consequently, guide wire  410  through flexible reamer guide tube  486  and into femoral head  414  as illustrated in  FIG. 73 . Once guide wire  410  achieves the position illustrated in  FIG. 73 , set screw  414  may be removed and flexible reamer guide  408  removed from the guide tube/retractor, leaving guide wire  410  in place within femur  108 . Flexible reamer  428  may then be operably inserted in guide tube/retractor  154  as illustrated in  FIG. 74  and, with guide wire  410  positioned within the cannula of flexible reamer  428 , femoral cavity  224  may be extended into femoral head  114  as illustrated in  FIG. 74 , with flexible reamer  428  being guided by guide wire  410 . A similar technique may be utilized for advancing guide wire  410  into the femoral shaft to extend femoral cavity  224  therein.  
      In a further alternative embodiment of the present invention, flexible reamer guide wire bender  440  as illustrated in  FIGS. 77-79  is utilized to in vivo bend a guide wire to guide reaming into, e.g., femoral head  114  as illustrated, e.g., in  FIG. 73 . As illustrated in  FIGS. 77-79 , flexible reamer guide wire bender  440  includes guide tube  456  for insertion into a guide tube/retractor of the present invention. Guide tube  456  includes a pair of elongate apertures. A first of these apertures accommodates inner wire tube  450  and outer wire tube  452  as illustrated, e.g., in  FIG. 79 . The second of the elongate apertures formed in guide tube  456  accommodates adjustment screw  458  as illustrated, e.g., in  FIG. 79 . Wire shaping head  448  is pivotally connected via pivot pin  444  to the distal end of flexible reamer guide wire bender  440  as illustrated in  FIG. 79 . As illustrated in  FIGS. 77 and 79 , roller  442  is positioned about pivot pin  444 . Wire shaping head  448  further includes roller pin  446  for connecting a second roller  442  in a rotatable manner to wire shaping head  448 . As illustrated in  FIG. 77 , screws  454  are utilized to affix the distal end of flexible reamer guide wire bender  440  to guide tube  456 . As illustrated in  FIG. 79 , outer wire tube  452  includes proximal wire extreme  462  against which an end of a guide wire will abut. Outer wire tube  452  is threadably engagable with either guide tube  456  or inner wire tube  450  so that outer wire tube  452  may be advanced into guide tube  456  to force a guide wire positioned against proximal wire extreme  462  through distal aperture  500  of flexible reamer guide wire bender  440 . Adjustment screw  458  is utilized to rotate wire shaping head  448  about pivot pin  444  whereby rollers  442  bend a guide wire into the desired shape as it exits distal aperture  500 . Shaping of a guide wire in vivo with flexible reamer guide wire bender  440  may be observed with a fluoroscope.  
      A guide wire bent with flexible reamer guide wire bender  440  will be advanced into, e.g., femoral head  114  as illustrated, e.g., in  FIG. 73  with respect to guide wire  410 . In this way, a flexible reamer will be utilized to extend femoral cavity  224  toward the femoral head as illustrated in  FIG. 74 . A similar procedure may be utilized for extending femoral cavity  224  into the shaft of femoral  108 .  
      In yet another alternative embodiment of the present invention, flexible reamers having flexible reaming heads are utilized to form the cavity in femur  108  into which a femoral implant in accordance with the present invention is implanted. As illustrated in  FIG. 93 , guide wire  590  is inserted into femur  108  and extends from greater trochanter  110 , through femoral neck  112 , and into femoral head  114 . Guide wire  590  can be inserted into femur  108  utilizing flexible reamer guide  408  ( FIGS. 71 and 72 ), or flexible reamer guide wire bender  440  ( FIGS. 77-79 ). After inserting guide wire  590  into femur  108 , flex up reamer  600  is used to ream a path from greater trochanter  110 , through femoral neck  112 , and into femoral head  114  as illustrated in  FIG. 94 . In one embodiment of the present invention, access  101  is formed in femur  108  prior to using flex up reamer  600  to ream a path from greater trochanter  110 , through femoral neck  112 , and into femoral head  114 . As illustrated in  FIG. 96 , flex up reamer  600  includes elongate aperture  611 . In use, guide wire  590  is positioned through elongate aperture  611  to guide reaming from greater trochanter  110 , through femoral neck  112 , and into femoral head  114 .  
      As illustrated in  FIGS. 94-96 , flex up reamer  600  includes a reamer head having large diameter portion  602  and small diameter portion  604 , with flexible cuts throughout the length of the flex up reamer head to allow the flex up reamer head to curve along the path defined by guide wire  590 . A number of flexible cuts may be utilized along the length of the reamer head of flex up reamer  600 , including the flexible cuts described in U.S. Pat. No. 6,053,922 with respect to flexible reamer shafts. Flex up reamer  600  may be inserted through any of the guide tube/retractors of the present invention, and may include a cooperating guide tube matched to the guide tube/retractor utilized. Flex up reamer  600  advantageously includes large diameter portion  602  and small diameter portion  604  sized to form apertures accommodating lag screw tube  266 , and lag screw shaft  274 , respectively.  
      After formation of femoral head arm  256 ′ ( FIG. 103 ) of the implant cavity, swivel/down reamer assembly  630  ( FIGS. 100-102 ) is utilized to extend the implant cavity as illustrated in  FIG. 103 . Referring to  FIGS. 100-102 , swivel/down reamer assembly  630  includes tool housing  632  having longitudinal aperture  631  running the length thereof as illustrated in  FIG. 104 . Tool housing  632  includes detent groove  640  for receiving the ball detent of the ball detent retaining mechanism described above. Tool housing  632  further includes set screw aperture  660  for securing flexible guide shaft  650  therein. As illustrated in  FIG. 102 , flexible guide shaft  650  includes set screw aperture  656  corresponding to set screw aperture  660  in tool housing  632 .  
      As illustrated in  FIGS. 102 and 105 , flexible guide shaft  650  includes flexible portion  654  and proximal end  658 , with set screw aperture  656  formed in proximal end  658 . Flexible portion  654  of flexible guide shaft  650  can be formed with a plurality of alternating, substantially semi-circular cuts  668  as illustrated in  FIG. 105 . Specifically, cuts  668  are alternatively formed from the top and the bottom of flexible portion  654  as illustrated in  FIG. 105 . As further illustrated in  FIG. 105 , alternating cuts  668  overlap the center line of flexible guide shaft  650 . Using non-continuous cuts as illustrated in  FIG. 105  to create flexibility in flexible portion  654  of flexible guide shaft  650  also limits flexibility to a plane perpendicular to the cuts because continuous material remains on either outside edge of flexible portion  654  of flexible guide shaft  650 . This additional material at both sides of flexible guide shaft  650  advantageously prevents axial compression of the tube along the longitudinal axis thereof. In an alternative embodiment, cuts  668  are pie shaped, terminating in an apex toward the center of flexible portion  654  of flexible guide shaft  650 . In construction, proximal end  658  of flexible guide shaft  650  is positioned within longitudinal aperture  631  of tool housing  632  and secured therein via a set screw. When proximal end  658  of flexible guide shaft  650  is secured within tool housing  632 , flexible portion  654  of flexible guide shaft  650  protrudes from tool housing  632 . Flexible guide shaft  650  includes reamer shaft aperture  653  ( FIG. 106 ) running the length thereof. Reamer shaft aperture  653  of flexible guide shaft  650  accommodates flex down reamer shaft  644  ( FIG. 102 ). Referring to  FIG. 102 , to assemble swivel/down reamer assembly  630 , flex down reamer shaft  644  is positioned within reamer shaft aperture  635  of flex down reamer head  634  and secured therein with a set screw positioned through set screw aperture  636  in flex down reamer head  634 . Flexible guide shaft  650  is inserted through flexible guide shaft aperture  639  of flex down reamer head  634  until end  651  ( FIG. 105 ) of flexible guide shaft  650  abuts shoulder  641  ( FIG. 102 ) of flex down reamer head  634 . Flex down reamer shaft  644  is positioned within reamer shaft aperture  653  of flexible guide shaft  650 , with flexible guide shaft  650  positioned within flexible guide shaft aperture  639  of flex down reamer head  634 . Flex down reamer shaft  644  extends the length of reamer shaft aperture  653  of flexible guide shaft  650  as well as the length of longitudinal aperture  631  of tool housing  632 , with chuck end  648  of flex down reamer shaft  644  extending out of tool housing  632  as illustrated in  FIGS. 100 and 101 .  
      Prior to securing flexible guide shaft  650  to tool housing  632 , and positioning flex down reamer shaft  644  therein, cable  662  is inserted through cable aperture  652 , which runs the length of flexible guide shaft  650 . After inserting cable  662  through cable aperture  652 , a piece of material larger in cross sectional area than cable aperture  652  is secured to the end of cable  662  extending outwardly from end  651  of flexible guide shaft  650  to prevent cable  662  from being pulled out of cable aperture  652  in a distal to proximal direction relative to flexible guide shaft  650 . In one exemplary embodiment, a ball of weld material is welded to the end of cable  662 . In construction, cable  662  extends from flexible guide shaft  650  through the length of tool housing  632 .  
      As illustrated in  FIGS. 100 and 101 , cable rod  664  traverses aligned cable rod slots  642  ( FIGS. 102 and 104 ) formed in opposing sides of tool housing  632 . Cable rod  664  includes cable aperture  665  for receiving cable  662 . After cable  662  is inserted through cable aperture  665  in cable rod  664 , the slack in cable  662  is eliminated and cable  662  is secured to cable rod  664 . As illustrated in  FIGS. 100-102 , handle  670  includes cable rod cutout  672  accommodating cable rod  664 . Handle  670  further includes tool housing aperture  674  into which tool housing  632  is positioned. Tool housing  632  can be secured to handle  670  via a set screw or other fastener extending through handle  670  into tool housing aperture  674 .  
      As illustrated in  FIGS. 100 and 101 , lever handle  682  is pivotally connected to handle  670  via pivot shaft  671 , with pivot shaft  671  traversing pivot apertures  686  and  676  ( FIG. 102 ) in lever handle  682  and handle  670 , respectively. Lever handle  682  includes a pair of elliptical cable rod apertures  688  in opposing arms thereof. Elliptical cable rod apertures  688  accommodate cable rod  664 . With cable rod positioned through elliptical cable rod apertures  688  in lever handle  682 , cable rod end nuts  666  are secured to opposing ends of cable rod  664  to prevent axial displacement of cable rod  664 . To complete assembly of swivel/down reamer assembly  630 , ratchet bar  692  is positioned within ratchet cutout  680  of handle  670  and pivotally connected thereto, with a leaf spring interposed between ratchet bar  692  and handle  670  to bias ratchet bar  692  upwardly toward handle  670 . As illustrated in  FIGS. 100 and 101 , lever handle  682  includes pawl end  690  for engaging the ratchet teeth of ratchet bar  692 .  
      In use, swivel/down reamer assembly  630  can be actuated from a straight or unflexed position as illustrated in  FIG. 100  to a flexed position as illustrated in  FIG. 101 . To actuate swivel/down reamer assembly  630  from the straight position illustrated in  FIG. 100  to the flexed position illustrated in  FIG. 101 , force is applied to lever handle  682  to pivot lever handle  682  about pivot shaft  671  toward handle  670 . When lever handle  682  is actuated in this manner, cable rod  664  is pulled toward handle  670 , causing flexible guide shaft  650  to flex downwardly. Specifically, cable  662  pulls the lower portion of flexible guide shaft inwardly, flexing flexible guide shaft  650  whereby the top portion of flexible guide shaft  650  is placed in tension or stretches, and the bottom portion of flexible guide shaft  650  is compressed. As illustrated in  FIGS. 100-102 , flex down reamer head  634  includes flexible cuts along its length. When flexible guide shaft  650  flexes as described above, flex down reamer head  634  similarly flexes downwardly, as flex down reamer shaft is positioned within flexible guide shaft aperture  639  of flex down reamer head  634  when swivel/down reamer assembly  630  is actuated from the straight position illustrated in  FIG. 100  to the flexed position illustrated in  FIG. 101 . As illustrated in  FIG. 101 , pawl end  690  of lever handle  682  engages the teeth of ratchet bar  692  to retain swivel/down reamer assembly  630  in the actuated position of  FIG. 100 . As described above, ratchet bar  692  is biased toward handle  670  by a leaf spring. To release swivel/down reamer assembly  630  from the actuated position illustrated in  FIG. 100 , a distal end of ratchet bar  692  may be pushed downwardly, i.e., away from handle  670  to release pawl end  690  of lever handle  682  from engagement with the teeth of ratchet bar  692 .  
      Referring to  FIG. 102 , lever handle  682  includes radiused cutout  684  sized to accommodate flex down reamer shaft  644 . In the straight or unflexed position illustrated in  FIG. 100 , radiused cutout  684  is positioned about flex down reamer shaft  644  such that cross bar  685  of lever handle  682  abuts the shoulder formed on flex down reamer shaft  644  between chuck end  648  and the remainder of flex down reamer shaft  644 . This cooperating shoulder arrangement prevents flex down reamer shaft  644  and, consequently, flex down reamer head  634  from being advanced through and away from tool housing  632 . When swivel/down reamer assembly  630  is actuated into the flexed position as illustrated in  FIG. 101 , lever handle  682  is moved so that flex down reamer shaft  644  is no longer positioned within radiused cutout  684  contacting flex down reamer shaft  644  and the cooperating shoulder arrangement which prevents flex down reamer shaft  644  and flex down reamer head  634  from being advanced through tool housing  632  is eliminated.  
      In use, flex down reamer head  634  is inserted into access  101 ′ formed in femur  108  as described above. As illustrated in  FIG. 103 , on initial insertion, flex down reamer head  634  is positioned about flexible guide shaft  650  as illustrated in  FIG. 103 . As illustrated in  FIG. 103 , tool housing  632  abuts greater trochanter  110  when swivel/down reamer assembly  630  is utilized to extend implant cavity  224 ′ as illustrated in  FIG. 3 . Upon insertion of flex down reamer head  634  through access  101 ′ in femur  108 , flex down reamer head  634  is actuated by coupling an actuation device to chuck end  648  of flex down reamer shaft  644  and supplying rotational motion thereto. With flex down reamer head  634  rotating to ream bone from femur  108 , swivel/down reamer assembly is actuated from the straight or non-flexed positioned illustrated in  FIG. 100  to the flexed position illustrated in  FIG. 101  to extend implant cavity  224  from femoral head arm  256 ′ formed by flex up reamer  600 , as illustrated in  FIG. 94 , toward the shaft of femur  108 . Actuation of swivel/down reamer assembly  630  from the straight or non-flexed position illustrated in  FIG. 100  to the flexed position in  FIG. 101  generally effects a swivel type reaming as described above. After swivel reaming is complete, chuck end  648  of flex down reamer shaft  644  is advanced through tool housing  632  to advance flex down reamer head  634  into and through the intramedullary canal of femur  108 . As flex down reamer head  634  is advanced relative to tool housing  632 , flex down reamer head  634  is also advanced relative to flexible guide shaft  650  so that flexible reamer head  634  is eventually moved out of engagement with flexible guide shaft  650 , i.e., flexible guide shaft  650  is no longer positioned within flexible guide shaft aperture  639  of flex down reamer head  634  (see  FIG. 102 ). As flex down reamer head  634  is advanced toward the intramedullary canal of femur  108 , flex down reamer head  634  will be directed into the intramedullary canal of the femur as it is moved from engagement with flexible guide shaft  650  due to the curvature provided by flexible guide shaft  650  and also due to the softer cancellous bone occupying the intramedullary canal versus the harder cortical bone material of the femur. To facilitate appropriate movement of flex down reamer head  634  into the intramedullary canal of femur  108 , flex down reamer head  634  has a generally bullet shape as illustrated, e.g., in  FIGS. 100-103 . The distal end of bullet shaped flex down reamer head  634  will glance off the harder cortical wall of the femur and be directed into the intramedullary canal as described above.  
      While this invention has been described as having exemplary designs, the present invention may be further modified with the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention utilizing its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.