Abstract:
An apparatus for preparing the femur of a patient to receive a prosthesis is disclosed. A support is mountable in the recess and is shaped for mounting the first insert on the support. The insert is shaped for guiding pivoting of a post in a direction for reaming the recess.

Description:
FIELD OF THE INVENTION 
   This invention generally relates to a method and apparatus for preparing a bone cavity for receiving a prosthesis. In particular, the invention relates to a surgical apparatus and method for shaping a cavity within a bone for receipt of a prosthesis for forming a joint in a patient&#39;s body. 
   BACKGROUND OF THE INVENTION 
   When installing a prosthesis for replacing a joint within the body, a portion of a bone is generally resected and a cavity is formed for receiving a prosthesis having a portion for forming a joint. A resection may be performed using a tool with a cutting edge, such as a chisel that is forced across an end of the bone to form a flat surface on which the prosthesis can transfer loads to the bone, or to remove a portion of bone that is damaged or deficient. A cavity is formed by a tool with a cutting edge driven longitudinally into the bone, such as a chisel, reamer or rasp. The cavity extends down the medulary canal and receives the stem of the prosthesis, which is used to provide some stability for the joint. In the implantation of a hip joint prosthesis, the head at the proximal end of the femur is removed and a hole is formed in the medullary canal of the femur. The cavity is then shaped so as to conform to the shape of the prosthesis selected by the surgeon according to the patient&#39;s indications. 
   Tools for shaping a cavity in a bone are known. A support having a guide arm for guiding a reamer in shaping a cavity in the femur is known. This apparatus requires a number of parts, including at least one guide arm which must be connected to an upper end of the guide body. A guide arm for the anterior side, as well as another guide arm for the posterior side must be attached to the upper end of the guide body, in order to shape both the anterior and posterior sides of the cavity. This apparatus complicates the method for shaping the cavity in the femur and includes many parts. Further, the guide arm allows the reamer to deviate from the path that produces the desired shape for the cavity. Another support has a guide bar that guides pivoting of a reamer. This system requires a plurality of supports and a multitude of reamers that correspond to different sized prostheses. Thus, the inventory of instruments is large and complicates preparation for, as well as the conduct of, the surgical procedure. 
   A plurality of different guide arms which can be selected according to the size of the prosthesis to be installed has also been proposed. However, this apparatus suffers from the drawbacks mentioned above. 
   A guide for shaping a cavity within an end of a bone for receiving a prosthesis, which simplifies the method of shaping the bone, is desirable. In addition, an apparatus that is adaptable according to the size of the prosthesis to be installed is also desired. 
   SUMMARY OF THE INVENTION 
   In a first aspect of the present invention, an apparatus for shaping a bone, comprises an insert shaped for guiding the pivoting of a shaping tool, and a support having an end adapted to be inserted into a cavity in the bone and having a mounting portion for mounting the insert on the support. The insert desirably guides pivoting of a shaping tool in a predetermined direction of the bone. The shaping tool may be carried on the insert. In certain embodiments, the insert has a connecting portion for connecting with the shaping tool. 
   Embodiments of the invention desirably include a plurality of inserts. Each insert is arranged to position the shaping tool in a different position as compared to the other inserts. The inserts enable the apparatus to be used to shape the bone for receiving any prosthesis, from a set of prostheses. For further flexibility, more than one support is provided and more than one insert is arranged for being assembled with each support. The insert desirably has a surface for guiding pivoting of the shaping tool. 
   The connecting portion of the first insert may comprise a post having an end and being assembled with the insert. In a preferred embodiment, the first insert has a bore defined therein and the bore is open on an upper end and a lower end of the insert and incorporating an engagement surface for engaging an end of the post and the post is received in the bore so that the post extends out the bore at the upper end of the insert. 
   In certain preferred embodiments, the insert has a top wall and a slot defined in the top wall. The first insert has a sidewall defining a bore in communication with the slot. The insert may have a central axis and the bore is desirably centered on the central axis. The slot extends in the top wall from the central axis to the sidewall of the insert. The slot and the bore may be offset from one another at a location and the bore may have an engagement surface at the location of the offset. The end of the post may have a shape corresponding to the shape of the engagement surface. In certain preferred embodiments, a fixing element is included for securing the end of the post in the insert. 
   In certain preferred embodiments, the insert comprises a first insert of a plurality of inserts. The insert is shaped for mounting on the support and for positioning the first insert with respect to the support. The apparatus desirably includes a second insert. In certain preferred embodiments, the first insert and the second insert are shaped for mounting on the support so that a shaping tool connected to the first insert has a position with respect to the support that is different from the position of the shaping tool connected to the second insert. 
   The support may have a body and the mounting portion may comprise a cavity defined by the body for receiving the insert. A longitudinally extending passage desirably communicates with the cavity. The body of the support may define an opening so that the passage is open at a front side of the support and so that the shaping tool may extend out the opening. The insert and the support are desirably shaped for positioning the insert and the shaping tool with respect to the support. 
   The lower end of the support is desirably shaped to be received in a cavity in a proximal end of a femur. In certain preferred embodiments, the support has an upper cylindrical portion and a lower conical portion. The lower conical portion may be shaped to correspond to a portion of a prosthesis to be inserted in the cavity. The conical portion of the support desirably positions the support within the bone. 
   The insert and the support are desirably shaped for locating the insert at a predetermined elevation with respect to the bone. The insert and the support are desirably shaped for locating the first insert with the respect to the bone so that the shaping tool pivots in a predetermined direction. A post is desirably assembled with the insert. A shaping tool is desirably shaped so as to be mounted on the post and to allow the shaping tool to rotate on the post. The shaping tool may comprise a reamer. 
   In certain preferred embodiments, the apparatus includes a post assembled with the insert, the insert has a central axis, and the post is pivotable between a first position and a second position. 
   In a further aspect of the present invention, a set of instruments for shaping a bone comprises a support to be mounted a cavity of the bone. The support has a mounting portion shaped for mounting an insert on the support. A first insert is shaped for guiding pivoting of a shaping tool and a second insert is shaped for guiding pivoting of a shaping tool. The first insert and the second insert are shaped for engagement with the support so that the first insert and second insert have different positions with respect to the bone. A set of instruments including a plurality of inserts having different positions with respect to the support may be mounted with a shaping tool for preparing the bone for receiving a prosthesis selected by the surgeon. 
   A further aspect of the present invention includes a method for shaping a bone comprising the steps of assembling an insert with a support. The insert carries a shaping tool. The support is inserted into a cavity in the bone, either before or after assembling the support and the insert, so as to position the shaping tool with respect to the bone. 
   In certain preferred embodiments, the insert is selected from a set of a plurality of inserts. The insert is desirably selected according to a desired position for shaping the bone. Each of the inserts of the plurality of inserts is desirably arranged so as to locate the shaping tool in a different position when the support is mounted in the cavity of the bone. 
   Desirably, the method includes selecting the insert according to a desired elevation. Each of the inserts is arranged so as to locate the shaping tool at a different elevation with respect to the bone. The support is, in certain preferred embodiments, shaped so as to locate the support at a desired elevation with respect to the bone for shaping the bone for a preselected prosthesis. The method includes positioning the insert with respect to the support so that the shaping tool pivots in a predetermined direction. The insert and the support are desirably positioned by adjusting the position of the insert with respect to the support until correspondingly shaped features of the insert and the support can be assembled with one another. 
   The method may include shaping the bone by pivoting the shaping tool in a predetermined direction of the bone. The insert is desirably shaped to guide the pivoting of the shaping tool. 
   The step of shaping desirably includes rotating the shaping tool so as to engage cutting surfaces of the shaping tool with the bone. 
   The method may further comprise rotating the support with respect to the bone, to position the shaping tool. The support may be positioned so that the shaping tool engages a desired portion of the bone. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
       FIG. 1  is a top-right perspective view of a first insert in accordance with an embodiment of the invention; 
       FIG. 2  is a top plan view of a first insert in accordance with the embodiment of  FIG. 1 ; 
       FIG. 3  is a left elevational view of a first insert in accordance with the embodiment of  FIGS. 1 and 2 ; 
       FIG. 4  is a rear elevational view of a first insert in accordance with the embodiment of  FIGS. 1-3 ; 
       FIG. 5  is a cross-sectional view taken along line  5 - 5  in  FIG. 4 ; 
       FIG. 6  is a top-right perspective view of a second insert in accordance with the embodiment of  FIGS. 1-5 ; 
       FIG. 7  is a top plan view of a second insert in accordance with the embodiment of  FIGS. 1-6 ; 
       FIG. 8  is a left elevational view of a second insert in accordance with the embodiment of  FIGS. 1-7 ; 
       FIG. 9  is a rear elevational view of a second insert in accordance with the embodiment of  FIGS. 1-8 ; 
       FIG. 10  is a cross-section taken along line  10 - 10  in  FIG. 9 ; 
       FIG. 11  is a front elevational view of a post in accordance with the embodiment of  FIGS. 1-10 ; 
       FIG. 12  is a left side elevational view of the post assembled with the first insert in accordance with the embodiment of  FIGS. 1-11 ; 
       FIG. 13  is a cross-section taken along lines  13 - 13  in  FIG. 12 ; 
       FIG. 14  is a front elevational view of a support in accordance with the embodiment of  FIGS. 1-13 ; 
       FIG. 15  is a cross-section taken along line  15 - 15  in  FIG. 14 ; 
       FIG. 16  is a right elevational view of a support in accordance with the embodiment of  FIGS. 1-15 ; 
       FIG. 17  is a rear elevational view of a support assembled with a second insert in accordance with the embodiment of  FIGS. 1-16 ; 
       FIG. 18  is a rear elevational view of a support assembled with a first insert in accordance with the embodiment of  FIGS. 1-17 ; 
       FIG. 19  is a cross-section taken along line  19 - 19  in  FIG. 17 ; 
       FIG. 20  is a cross-section taken along line  20 - 20  in  FIG. 18 ; 
       FIG. 21  is a cross-sectional view of a support, insert and shaping tool in a first position in accordance with the embodiment of  FIGS. 1-20 ; 
       FIG. 22  is the cross-sectional view of  FIG. 21  showing the shaping tool in a second position; 
       FIG. 23  is a cross-sectional view of a support and a set of inserts in accordance with another embodiment of the invention. 
   

   DETAILED DESCRIPTION 
     FIGS. 1-22  show an embodiment of the present invention, in which an apparatus  10  includes a first insert  12 . The first insert has a sidewall  18  forming a generally cylindrical body with an upper end  14 , lower end  16 , front  21 , rear  25  and central axis  23 , as best seen in  FIG. 5 . The body has an upper cylindrical portion  20  and a lower cylindrical portion  22 , both centered on the axis  23 . In the embodiment shown, the first insert  12  is cylindrical and has an upper cylindrical portion  20  with a greater diameter than the diameter of the lower cylindrical portion  22 . However, the insert may have a variety of regular or irregular shapes. 
   As seen in  FIG. 5 , the wall  18  has an inner surface  28  defining a bore  30 . The bore  30  is desirably open at the upper end  14  and lower end  16  of the first insert  12  and centered on the axis  23 . In the embodiment shown, the first insert  12  includes a top wall  24  at the upper end  14 , in which a slot  26  is defined. ( FIGS. 1 and 2 ). The slot communicates with the bore  30 . The slot  26  has an elongate shape extending from a first end  11  at the central axis  23  of the first insert  12  to a second end  13  at the front  21  of the first insert  12 , as best seen in  FIG. 1 . The slot has edge surfaces  27  generally extending from the first end  11  to the second end  13 . 
   The inner surface  28  includes an inclined surface  32  extending from the slot  26  at the front  21  of the first insert, toward the axis  23 , as best seen in  FIG. 5 . The slot  26  and bore  30  are offset from one another at the rear  25  of the first insert. The inner surface  28  of the sidewall  18  forms an engagement surface  33  extending between the slot  26  and the bore  30  at the offset, at the rear  25  of the first insert. As shown in  FIG. 5 , the engagement surface  33  curves inwardly from the bore  30  to the slot  26 . 
   An outer surface  29  of the sidewall  18  defines a notch  34  at the rear  25  of the first insert  12 . The notch  34  extends from a stop  36  closing an upper end of the notch  34  to an open end at the lower end  16 , as best seen in  FIG. 4 . 
   A second insert  40 , which is generally similar to the first insert, is shown in  FIGS. 6-10 . However, the second insert is shaped so as to be positioned at a different elevation with respect to the bone, as discussed further below. As best seen in  FIG. 10 , the second insert has a wall  48  forming a generally cylindrical body with an upper end  42 , a lower end  46 , a front  47 , a rear  49  and a central axis  57 . The wall  48  defines an upper cylindrical portion  50  and a lower cylindrical portion  52 . In the embodiment shown, the second insert  40  is generally cylindrical, but may have other shapes. The second insert  40  and first insert  12  may have the same height or different heights. Preferably, the first insert  12  and second insert  40  have about the same radial dimensions. The second insert  40  has a bore  53  extending from the lower end  46  to a slot  56  in a top wall  54 . The slot  56  has an elongate shape, extending from the central axis  57  to the outer surface of the wall  48 , at the front  47  of the second insert  40 . ( FIGS. 7 and 10 ) The second insert has an inclined surface  58  at the front of the insert. As best seen in  FIG. 9 , a notch  60  is defined by the wall  48  at the rear  49  of the second insert  40 . The notch  60  is open on the lower end  46  of the second insert  40  and extends from the lower end  46  to a stop  62 . 
   The slot  56  and bore  53  are offset from one another at the rear  49 . The second insert  40  has an engagement surface  43  extending between the slot  56  and the bore  53 , at the rear  49 , where the slot  56  and bore  53  are offset from one another. In the embodiment shown in  FIGS. 5 and 10 , the engagement surface  33  and engagement surface  43  have the same elevation on each insert. As seen in  FIGS. 5 and 10 , notch  34  and notch  60  have different elevations on each insert. Thus, the stop  36  is located closer to the engagement surface  33  on the first insert, as compared to the spacing of the stop  62  from surface  43 . 
   In certain preferred embodiments, a post is assembled with each of the inserts  12  and  40 . Each post may be as shown in  FIG. 11 . The post  64  comprises an elongate member having a first end  66  and a second end  70 . The first end  66  is shaped for engaging the engagement surface on the insert and for allowing the post to pivot. Preferably, the first end  66  has a curved surface  68 . However, the surface  68  of the post  64  may have a surface  68  with a variety of shapes. For example, the surface  68  may comprise a hemispherical surface, or another curved shape. Preferably, the engagement surface on the insert to be used with the post corresponds to the shape of the first end  66 . 
   The post may be assembled with one of the inserts as follows. For example, a second end  70  of the post is inserted into the bore  30  of the first insert  12 , at the lower end  16 , and advanced into the bore  30 . The second end  70  of the post passes through the slot  26 . The post  64  is advanced into the bore  30  until the curved surface  68  engages the engagement surface  33  in the bore  30 , as shown in  FIG. 12 . The post  64  is then fixed in the first insert  12  by any means known in the art. In certain embodiments, a washer  69  and a resilient element  76  is disposed in the bore  30  so as to engage the curved surface  68  and seat the first end  66  against the engagement surface. A cap  78  having a cylindrical shape corresponding to the bore  30  is inserted into the bore  30  so as to press the resilient element  76  against the curved surface  68  and is secured in the bore  30  to secure the resilient element  76  and post  64  in the first insert. One arrangement for securing the cap comprises a pin  80  in an aperture  65  extending laterally through the wall  18  of the first insert  12  and also through a hole  67  extending laterally through the cap  78 , so that the pin  80  extends through the wall  18  and through the cap  78 . However, any other arrangement may be used. For example, the cap  78  may be threadably received in the bore  30 . In other embodiments, the bore  30  at the lower end  16  is closed and the first end  66  is inserted in the bore  30  at the upper end  14  and secured at the upper end  14 . 
   Preferably, posts are preassembled with each of the inserts. However, the posts, inserts and other parts can be disassembled or otherwise arranged so that they can be adequately cleaned. The engagement surface  33  of the first insert  12  and engagement surface  43  of the second insert  40  are shaped to correspond to the shape of the curved surface  68  of the first end  66  of the post  64  and to allow the post to pivot. The slot  26  is arranged in the top wall  24  so that the pivoting of the post  64  is guided in the direction in which the slot  26  extends. The post  64  translates from a position generally in alignment with the central longitudinal axis of the insert to a position leaning toward the front of the insert, as shown in  FIG. 12 . For example, the first insert  12  has a slot  26  extending from the axis  23  to the front  21  of the insert. The inclined surface  32  defines the end of the slot  26  at the front  21  and the slot  26  has a rear end  13  arranged so as to position the post  64  substantially along axis  23 , in a first position. The post  64  may be pivoted around the first end  66 , as guided by the edge surfaces  27  of the slot  26  toward the front end  11  of the slot  26 . At the front end  11 , the post  64  has a second position in which the post  64  rests on the inclined surface  32 . 
   The posts may be assembled on the inserts so that the posts are pivotable using any means known in the art. For example, the post and insert may have a hinged connection. The post may or may not have an end disposed in a bore in the insert. A portion of the post may be formed from a flexible material so that flexing of the post pivots the post with respect to the support. 
   The apparatus  10  includes a support  90  having a body  96  with a front side  95 , rear side  97 , upper side  92  and lower side  94 . (See  FIGS. 14-16 ). The body has an elongate shape and extends from the upper side  92  to the lower side  94 . The body  96  has an exterior surface  98  and an interior surface  100 . The interior surface  100  defines a passage  102  that is open on the upper side  92  of the support  90 . An opening  104  at the front side  95  of the body communicates with the passage  102 , whereas the rear side  97  is closed. The support body  96  forms a cylindrical part  105  extending from the upper side  92  to a conical part  107  at the lower side  94 . The opening  104  and passage  102  extend to the conical part, as best seen in  FIG. 14 . The conical part  107  has a frusto-conical shape, tapering toward the lower side  94  of the support  90 . In other embodiments, the support may have other shapes. 
   The support  90  has a mounting portion  106  in the conical part  107 . The passage  102  and opening  104  communicate with a cavity  103  in the mounting portion  106 . The cavity  103  is sized and shaped for receiving the first insert  12  and second insert  40 , or any number of inserts provided in a set. A protrusion  101  extends from the wall  96  at the rear side  97  into the cavity  103 , as best seen in  FIG. 15 . The upper side  92  incorporates a flange extending radially outwardly from the wall  96 . The flange is desirably arranged for mounting a handle or other instruments on the support. The lower side  94  is desirably arranged for connection with a stabilizing element. In the embodiment shown, the lower side  94  has a threaded bore  99  for connecting with the stabilizing element disposed in the bone. The stabilizing element may comprise a rod, stem, or any element disposed in or mounted on the bone. 
   The conical part  107  of the support  90  is shaped so as to be received in the cavity formed in the femur, at a predetermined elevation in the femur, seating the entire apparatus in the femur. The shape of the conical part  107  desirably corresponds to the shape, at the predetermined elevation, of the prosthesis to be implanted in the femur. Desirably, a tapered surface extends within the cavity in the femur so as to correspond to the prosthesis to be implanted, and the tapered shape of the conical part  107  seats the support in the recess. The support desirably includes a groove  108 , or may include indicia, for confirming the position of the support  90  in the recess in the bone. 
   The support  90  may have a variety of shapes, including polygonal, curved, cylindrical, conical, and other regular or irregular shapes. The support  90  is desirably shaped to correspond approximately to the shape of the recess in the bone or at least to fit therein adequately so that the shaping of the bone can be accomplished as desired with the assembly. 
   The inserts are received in the cavity  103  of the support  90 . For example, the first insert  12  is inserted in the cavity  103  of the mounting portion  106  with the rear  25  of the first insert  12  facing the rear side  97  of the support  90 . As the notch  34  is formed in the wall  18  at the rear  25 , and the protrusion  101  is formed at the rear side  97 , the protrusion  101  is received in the notch  34 . The slot  26  extends from the axis  23  to the front  21  of the first insert  12  so that, when the protrusion  101  is received in the notch  34 , the slot  26  extends in a predetermined direction of the apparatus. The slot  26  is thereby located so that when the post  64  tilts toward the front  21  of the first insert  12 , and the post  64  passes through the opening  104 . The protrusion  101  and notch  34  also locate the post in elevation with respect to the bone, as the mounting portion  106  has a predetermined elevation in the bone, the protrusion  101  has a predetermined elevation with respect to the seat  106  and the notch  34  and curved surface  68  have a predetermined elevation on the first insert  12 . 
   As shown in  FIGS. 19 and 20 , the protrusion  101  in the support  90  locates the inserts in the support. The second insert  40  has the notch  60  at the rear  49  of the insert  40 . Thus, the notch  60  is opposite the front  47  and the slot  56  extends generally between the rear  49  and the front  47  of the insert. The protrusion  101  is located at the rear side  97  of the support so that when the second insert  40  is inserted in the cavity  103  of the support  90  so that the notch  60  engages the protrusion  101 , the slot  56  extends generally between the rear side  97  and the front side  95  of the support  90 . As the opening  104  is located at the front side  95 , a post  64  extends through the opening  104  when the post  64  has been pivoted so as to rest on the inclined surface  58  of the slot  56 . 
   The second insert  40  has a notch  60  with a stop  62  at a predetermined position with respect to the top wall  54  of the second insert  40 . The stop  62  engages protrusion  101  so that the center of the protrusion  101  is spaced from the center of the first end  66  by a distance X 2 , as shown in  FIG. 20 . The first insert  12  shown in  FIG. 19  has the notch  34  with the stop  36  at a different position. The stop  36  engages the protrusion  101  so that the center of the protrusion  101  is spaced from the center of the first end  66  by a distance X 1 . As the distance X 2  for the second insert  40  is different from the distance X 1  for the first insert  12 , the shaping tool has a different position with respect to the support. 
   The apparatus desirably includes at least one shaping tool  110  for shaping the recess in the bone. The shaping tool  110  may comprise a reamer with an abrasive surface that may comprise cutting edges  112 . The cutting edges in  FIGS. 21 and 22  are helical in shape. However, other shapes may be used. The shaping tool  110  desirably has a top end  114  shaped for mating with a driver, which may comprise a manual or motorized driver. In further embodiments of the invention, the post has cutting features or abrasive features so that the post comprises a shaping tool. 
   The apparatus  10  desirably includes a set of instruments having a plurality of inserts for locating the post in a range of elevations in the femur with respect to the prosthesis to be implanted. After the surgeon has selected the prosthesis to be implanted, the cavity is formed in the bone by the surgeon. For example, the cavity may be formed using a conical reamer, for forming a cavity with a shape corresponding to the shape of the support and for locating the support in the bone. The conical reamer, or other reamer for forming the cavity includes indicia for indicating the depth of the cavity so that the prosthesis is property mounted in the cavity. The threaded bore  99  on the support  90  is used to connect the support  90  to a stabilizing element, such as a centralizing rod, and the stabilizing element is inserted into the elongated hole in the medullary portion of the bone. Other arrangements may be used to connect the stabilizing element and support  90 , in the event such element is used, such as corresponding polygonal shapes on the stabilizing element and in the bore. The stabilizing element may comprise a part of the prosthesis to be implanted. In other embodiments, the stabilizing element comprises a portion of the support. 
   The insert corresponding to the prosthesis is selected by the surgeon and introduced into the cavity  103  of the guide body  90 . The engagement of the protrusion  101  locates the insert accurately within the cavity  103 , as discussed above. The support  90  is arranged so as to locate the slot on the insert so that the post extends out opening  104  of the support when pivoted, and at the correct elevation in the femur, once the support  90  is positioned in the cavity of the femur. 
   A shaping tool is then selected for shaping the cavity and the shaping tool is mounted on the post. For example, the shaping tool  110  comprises a reamer with a hole and the post is inserted into the hole in the shaping tool  110 . Other arrangements for mounting the shaping tool on the post may be used. The engagement of the notch  34  and protrusion  101  ensures that the shaping tool has the desired elevation within the femur, so that the shaping tool  110  shapes the cavity for the prosthesis selected by the surgeon. The end  114  of the shaping tool  110  is connected to a driver, for either manual or mechanically driven rotation of the shaping tool. The shaping tool  110  is simultaneously pivoted, pivoting the post  64  and the shaping tool  110  installed on the post. ( FIGS. 21 and 22 ) The shaping tool  110  is arranged to form the appropriately sized cavity within the proximal portion of the femur for the prosthesis already selected by the surgeon. 
   Thus, each insert corresponds to a prosthesis that may be selected from a set of prostheses. As several inserts may be assembled with the support, the inventory for the set of instruments is reduced. 
   The support may comprise any suitable support for the insert and for being received in the cavity of the bone. For example, the support may comprise a part of the prosthesis to be implanted, or any other orthopedic device. 
   In further embodiments of the invention, the inserts have shapes other than cylindrical shapes. The inserts may have any polygonal or curvilinear shape. In addition, the support may be arranged so as to receive the inserts from a lower end of the support. In certain embodiments, the shape of the insert locates the position of the post and shaping tool in elevation. For example, the insert may have a tapered shape, in the direction toward the lower end. The radial dimensions of each insert may determine the elevation of the insert with respect to the bone, when mounted on the support. In other embodiments, the insert may have a flange that engages a ledge within the cavity so as to locate the post. In certain embodiments, the shape of the insert locates the post and shaping tool for pivoting in a predetermined direction of the bone, such as a polygonal insert received in a polygonal cavity in the support. In addition, in other embodiments, a further element may engage the support and insert so as to locate the post. In other embodiments, the insert is threadably received in the cavity of the body. In further embodiments, the cavity in the support may be omitted and the inserts and support may be assembled with each other by other means. For example, the inserts may include a cavity for receiving a portion of the support. 
   The insert may be shaped for connecting to a reamer or other shaping tool, and the post may be omitted. The post may be connected to the insert using any suitable mechanical arrangement. The insert may have a connecting portion received by the reamer, for example. 
   In a further embodiment of the invention, each insert from a set of inserts has a feature that engages the support and which is located in the same position on all the inserts in the set. As shown in  FIG. 23 , each insert  212   a ,  212   b ,  212   c  has an engagement surface  233   a ,  233   b ,  233   c  with a different position in elevation from the other inserts. Each insert has an upper end  214   a ,  214   b ,  214   c  that abuts a flange  201  on the support  290 . The inserts are received at a lower end of the cavity  203  in the support  290 . The inserts desirably carry a resilient element  276  for biasing the end of the rod against the engagement surface, seating the rod. A threaded cap  278 , or other feature, is used to secure the insert and resilient element in the insert. In other embodiments, the inserts and support are shaped so that the shaping tool is positioned at the same elevation, but different positions with respect to the recess, in some other respect. 
   Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. For example, the specific embodiments discussed above are directed to shaping the femoral bone. However, embodiments of the present invention include instruments for shaping bones other than the femur. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.