PATENT ABSTRACT
A broaching system is disclosed for creating a cavity in a bone. The cavity has a cross section which has a generally triangular profile having a first side generally parallel with an axis of the bone and a second side forming an acute angle with the first side. The cavity is contiguous with a pre-existing conical cavity in the bone. The apparatus comprises as shaft and a broach. The shaft has a longitudinal axis. The broach is mounted to the shaft and has a first cutting side mounted at the acute angle relative to the longitudinal axis of the shaft. The first cutting side is formed to include teeth. The shaft and broach are configured so that when the longitudinal axis of the shaft is advanced into the bone along the axis of the bone, the teeth of the broach form the triangular cavity. A method for cutting a triangular cavity in bone is also described. The method comprises a providing a shaft step, an incising step and a cutting step. The provided shaft is configured to be movable relative to the bone to be prepared and includes a broach coupled thereto to dispose a cutting surface of the broach at an acute angle relative to the shaft. The shaft and broach have a width defined by the distance between the shaft and the outer most portion of the cutting surface. The incising step includes incising the patient adjacent the bone to be prepared to form an incision having a length approximating the width of shaft and broach. The cutting step includes cutting the cavity by driving the broach by moving the shaft relative to the bone.

PATENT DESCRIPTION
BACKGROUND AND SUMMARY  
       [0001]     This invention relates to the field of artificial joint prostheses and, in particular, to an improved instrument for broaching a cavity in bone for receiving a prosthesis.  
         [0002]     For implantation of prosthetic stems, such as hip stems, accurate preparation of the bone or intramedullary canal is important in order to guarantee good contact between the prosthesis stem and sleeve and the bone. The underlying concept behind precise preparation is that a precise bone envelope reduces the gaps between the stem and sleeve of the implant (i.e. prosthesis or prosthetic component) and the bone, thereby improving the initial and long-term bone ingrowth/fixation. The bone canal is presently prepared for implantation of a prosthetic stem by drilling and reaming a resected end of a bone, such as a femur, and then preparing an area adjacent the drilled hole to provide a seat for the prosthetic stem or a proximal sleeve coupled to the stem of a modular prosthetic system. A sleeve of modular prosthesis system is disclosed in U.S. Pat. No. 5,540,694, the disclosure of which is incorporated herein by this reference.  
         [0003]     Preparation of the area adjacent the reamed intramedullary canal may be accomplished by broaching or by milling. Currently available broaches or rasps used for bone preparation have limitations. Some such broaches or rasps rely solely on the surgeon for guidance. Currently available broaches and rasps suffer from a tendency to be deflected by harder sections of bone so that they do not create a precise triangular cavity for receipt of the stem or sleeve of the prosthesis.  
         [0004]     Thus, milling is currently the preferred method of bone preparation in many orthopaedic applications because it is a precise method of bone preparation. A limitation of milling systems today is that they are typically formed so that the drive shaft extends at an angle relative to the remainder of the frame from the end of the miller cutter machining the bone. A fairly large incision must be made to accommodate such milling assemblies. A typical incision for preparing a femur for a total prosthetic hip replacement using a standard triangle miller system is nine inches long. It is not uncommon for incisions as large as 12 inches to be used in a total hip replacement procedure. Efforts have been made to configure triangle miller systems to reduce the size of the incision required to accommodate a triangle miller during a prosthetic operation. However, to accommodate any miller, it is necessary to make an incision which may be undesirably large for cosmetic or other reasons.  
         [0005]     In a hip replacement operation, initially, an incision large enough to expose the proximal end of the femur and to accommodate the instruments to be used in the operation is made in the upper thigh of the patient. Then, the neck of the femur is resected at the appropriate varus-valgus and anterior-posterior locations (typically determined using a template) with a resection instrument such as an oscillating saw. Then the femoral canal is opened up and the femoral cortex is reamed in preparation for receipt of the distal stem component of the prosthesis. Typically a stepped starter drill is utilized to generate an initial hole in the intramedullary canal. The stepped starter drill is positioned to open the trochanteric region to guard against varus positioning of the reamer and prosthesis. To further protect against varus positioning a box osteotome can be used to remove additional bone from the medial aspect of the greater trochanter.  
         [0006]     Once the femoral canal has been appropriately opened, reaming begins utilizing a straight reamer. Distal reaming is done using a series of sequentially larger reamer diameters. The final straight reamer utilized should be ½ mm larger than the minor diameter of the selected femoral stem. The initial reamer is typically different from the rest in that it is an end cut reamer utilized to assist in canal finding, while the remaining reamers are blunt tipped side cutting reamers. The reamers are passed into the canal until a witness mark associated with the length of the stem component of the prosthesis to be utilized is adjacent the greater trochanter. The surgeon then works up progressively until cortical contact is made. Distal reaming is complete when the surgeon has reamed out to cortical bone in the shaft region.  
         [0007]     The proximal or cone portion of the femoral metaphysis is then performed. Progressively larger cone reamers attached to an appropriately sized pilot stem are utilized to perform the cone portion of the femoral metaphysis. The cone reamer is advanced until an appropriate witness mark on the shaft is adjacent the greater trochanter. Successively larger cone reamers are used until cortical contact is achieved in the proximal femur.  
         [0008]     Once cone reaming is completed calcar preparation is performed. Calcar preparation has been performed using triangular miller, broaches and reamers. When hand guided broaches or rasps or triangular millers are utilized for calcar prepartion, the initial incision must be fairly larger to accommodate these instruments. Following calcar preparation, a trial sleeve and trial implant are inserted into the proximal end of the femur. The trial sleeve is utilized to determine if anteversion or version must be changed in the prosthesis by performing trial reductions and adjusting the version and anteversion of the proximal trial component appropriately. Based on the trials, the final prosthesis components are selected assembled and inserted into the bone.  
         [0009]     Since the oscillating saw used for neck resection and the straight reamers and conical reamers used for canal preparation are typically smaller than the instrument used for calcar preparation, the calcar preparation instrument often dictates the size of the incision required to perform the operation. When a patient undergoes total hip replacement (THR) it is common for the patient to stay in the hospital for one to two weeks. Rehabilitation therapy lasts months and many patients do not fully recover for years. Some patients never fully recover. This recovery process poses a substantial psychological and financial strain on THR patients. Many patients are in the latter years of their lives and this recovery period represents a significant portion of the remaining years. Current trends in joint replacement surgery suggest that smaller incision size can lead to faster recovery, improved quadriceps function and increased patient satisfaction.  
         [0010]     When the calcar preparation is performed using a guided calcar broach, minimally invasive surgery can be performed. The disclosed broaching system is utilized for the calcar preparation in a hip prosthesis operation.  
         [0011]     In view of the above, it would be desirable to have a calcar preparation instrument that can be utilized through a smaller incision during a surgical process.  
         [0012]     According to one aspect of the disclosure, an apparatus is provided for creating a cavity in a bone, said cavity (i) having a cross section which has a generally triangular profile having a first side generally parallel with an axis of the bone and a second side forming an acute angle with the first side, and (ii) being contiguous with a pre-existing conical cavity in the bone. The apparatus comprises as shaft and a broach. The shaft has a longitudinal axis. The broach is mounted to the shaft and has a first cutting side mounted at the acute angle relative to the longitudinal axis of the shaft. The first cutting side is formed to include teeth. The shaft and broach are configured so that when the longitudinal axis of the shaft is advanced into the bone along the axis of the bone, the teeth of the broach form the triangular cavity.  
         [0013]     According to a second aspect of the disclosure an apparatus for creating a cavity in a bone for receiving a prosthesis which has a conical portion and a projection of a generally triangular profile is provided. The apparatus comprises a shell, a shaft and a broach. The shell comprises a conical portion which defines a longitudinal axis and a shaft-receiving cavity for receiving a shaft. The shaft is configured to be received in the shaft-receiving cavity and be movable with respect to the shell along the longitudinal axis when so received. The shaft is configured to carry a broach having a cutting surface disposed at an acute angle relative to the longitudinal axis. The broach has a generally triangular profile and includes oppositely facing spaced apart triangular shaped side walls between which the cutting surface extends. The broach is mounted to the shaft.  
         [0014]     According to yet another aspect of the disclosure, a method for cutting a triangular cavity in bone is provided. The method comprises a providing a shaft step, an incising step and a cutting step. The provided shaft is configured to be movable relative to the bone to be prepared and includes a broach coupled thereto to dispose a cutting surface of the broach at an acute angle relative to the shaft. The shaft and broach have a width defined by the distance between the shaft and the outer most portion of the cutting surface. The incising step includes incising the patient adjacent the bone to be prepared to form an incision having a length approximating the width of shaft and broach. The cutting step includes cutting the cavity by driving the broach by moving the shaft relative to the bone.  
         [0015]     The disclosed broaching system is configured to reduce the size of incision required for preparation of a bone to receive a prosthetic stem therein.  
         [0016]     The accompanying drawings, which are incorporated in and constitute part of the specification, illustrate the preferred embodiments of the invention, and together with the description, serve to explain the principles of the invention. It is to be understood, of course, that both the drawings and the description are explanatory only and are not restrictive of the invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     The illustrative devices will be described hereinafter with reference to the attached drawings which are given as non-limiting examples only, in which:  
         [0018]      FIG. 1  is a view with parts broken away of a broach assembly formed form components of a broaching system inserted through an incision into a resected femur of a patient using a selected broach shell and pilot stem and a selected guided broach received in the selected broach shell;  
         [0019]      FIG. 2  is an exploded view of the broaching system of  FIG. 1  showing the guided broach with the driver component disassembled from the broach tool, two broach tools intended to represent a plurality of broach tools each configured to be coupled to the driver component, two shells intended to represent a plurality of shells each configured to slidably receive a broach tool and two pilot stems each configured to mount to each shell;  
         [0020]      FIG. 3  is an elevation view of the guided broach of  FIG. 1 ;  
         [0021]      FIG. 4  is a plan view of the guided broach of  FIG. 3 ;  
         [0022]      FIG. 5  is a sectional view taken along line  5 - 5  of  FIG. 4  of the guided broach;  
         [0023]      FIG. 6  is an end elevation view of the broach toll of the guided broach of  FIG. 3 ;  
         [0024]      FIG. 7  is an enlarged view of the portion of the guided broach enclosed in phantom circle  7  in  FIG. 5 ;  
         [0025]      FIG. 8  is a sectional view taken along line  8 - 8  of the broach tool of  FIG. 3 ;  
         [0026]      FIG. 9  is a view with surrounding skin and tissue removed of a patient&#39;s resected a femur with parts broken away showing the final straight reamer used to prepare the intramedullary canal for a prosthesis;  
         [0027]      FIG. 10  is a view similar to  FIG. 9  showing the final conical reamer used to prepare a conical cavity in the intramedullary canal for a prosthesis; and,  
         [0028]      FIG. 11  is a view similar to  FIG. 10  showing a broach assembly including a broach shell and a pilot stem inserted in the straight and conical cavities formed in the femur and a guided broach positioned for insertion into or removal from the broach shell. 
     
    
       [0029]     Corresponding reference characters indicate corresponding parts throughout the several views. Like reference characters tend to indicate like parts throughout the several views.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0030]     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the invention is thereby intended. It is further understood that the present invention includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the invention as would normally occur to one skilled in the art to which this invention pertains.  
         [0031]     The disclosed broaching system  10  allows a surgeon to prepare bone for receipt of an implant through a smaller incision  12  compared to existing surgical instruments. In the illustrated embodiment, the incision  12  has a width  13 . Illustratively, the disclosed broaching system  10  can be utilized with an incision having a width  13  of less than two and a half inches. In one preferred embodiment, the width  13  of the incision  12  is two inches. The disclosed broaching system  10  is typically used for broaching of a triangular space  14  in a bone  16  adjacent the intramedullary canal  18  to facilitate receipt of a sleeve of a prosthesis that fits accurately in the intramedullary canal  18 , distributes loads evenly and provides rotational stability to the prosthesis.  
         [0032]     The disclosed broaching system  10  is particularly useful for preparing a bone  16  for receipt of a modular prosthesis having a plurality of stem components, a plurality of sleeves and a plurality of body components that may be assembled to provide a prosthesis appropriately sized and configured for a patient&#39;s specific anatomy. The disclosed broaching system  10  includes a plurality of broach shells  26 , a plurality of pilot stems  42 , and a plurality of guided broaches  20 . In one illustrated embodiment, the plurality of guided broaches  20  comprises a single driver component  24  configured for mounting to any one of a plurality of broach tools  22 .  
         [0033]     With reference now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in  FIG. 2  an exploded view of selected components of a broaching system  10  constructed in accordance with the invention. Broaching system  10  includes the plurality of guided broaches  20  for cutting the desired triangular-shaped cavity  14 , the plurality of broach shells  26  for registering the broaching system  10  with a pre-existing conical cavity in the patient&#39;s bone  16 , and the plurality of pilot stems  42  configured to be attached a broach shell  26  for insertion in a prepared medullary canal  18  of the patient&#39;s bone  16 . Indicators  28 ,  30  are provided for indicating the longitudinal location of guided broach  20  relative to the broach shell  26 . In the embodiment illustrated in  FIG. 2 , the plurality of guided broaches  20  comprises a single driver component  24  configured to be removably coupled to any one of the plurality of broach tools  22 . Those skilled in the art will recognize that a plurality of integrally formed driver components  24  and broach tools  22  could be provided as a plurality of guided broaches  20  within the scope of the disclosure. Providing a plurality of integrally formed guided broaches  20  makes it easier for instruments to be selected during the surgical procedure.  
         [0034]     While in the illustrated embodiment, only two broach shells  26 , two pilot stems  42 , and two broach tools  22  are shown, it is to be understood that a plurality of broach shells  26 , pilot stems  42  and broach tools  22  may be made available to the surgeon using the disclosed broaching system  10 . Each broach tool  22  is configured to be coupled to the driver component  24 . Thus a plurality of guided broaches  20  may be formed each utilizing the same driver component  24 . Each broach shell  26  is configured to slidably receive a portion of the broach tool  22  and act as a guide therefore during calcar preparation of the bone  16 . Each pilot stem  42  is configured to mount to each broach shell  26  to facilitate stable seating of the broach shell  26  and pilot stem  42  in the prepared bone  16 . Thus, the appropriate instrumentation for broaching the triangular cavity  14  can be selected and assembled by a surgeon to form a broach assembly  19  during a prosthetic operation.  
         [0035]     As shown, for example in  FIGS. 1 and 2 , broach shell  26  has a longitudinal axis  40 . Pilot stem  42  is removably attached to the main body of the broach shell  26  by, for example, a threaded shaft  38  extending from the proximal end of the pilot stem  42  which is configured to be received in a threaded cavity in the distal end of the broach shell  26 . The broach shell  26  also has an external frustoconical surface  44  which engages the wall of the pre-existing conical cavity, as shown, for example, in  FIG. 1 . In addition, the broach shell  26  has shaft-receiving cavity  46  formed concentrically about the longitudinal axis  40  for receiving the shaft  48  of the broach tool  22  and allowing the longitudinal axis  66  of the shaft  48  of the broach tool  22  to move along longitudinal axis  40 . In the illustrated embodiment, shaft-receiving cavity  46  is a cylindrical cavity extending longitudinally within the shell  26  from a circular opening in the proximal end of the shell  26  to adjacent the distal end of the shell  26 . In the illustrated embodiment, shaft-receiving cavity  46  has a diameter of approximately 0.375 inches.  
         [0036]     The broach shell  26  includes a laterally opening slot  76  communicating with the shaft-receiving cavity  46  and extending through the side wall of the shell  26  adjacent the proximal end of the shell  26 . A laterally opening channel  77  communicating with the shaft-receiving cavity  46  and the slot  76  extends through the side wall of the shell  26  below the slot  76 . Channel  77  is wider than slot  76  to allow triangular broaches  34  to ride in the channel  77  but not in the slot  76 . A triangular broach  34  riding straight upwardly in the channel  77  eventually engages a broach engaging wall  74  at the upper wall of channel  77  where the channel  77  and slot  76  form a junction. In the illustrated embodiment, slot  76  has a length  75  from the proximal end of the shell  26  to the wall  74 . The length  75  of slot  76  facilitates insertion and removal of broach tools  22  from the shell  26  without requiring removal of the shell  26  from the bone  16 , as described more fully below.  
         [0037]     Broach shell  26  can include indicia  82  which relate to the geometry of the neck of the femoral prosthesis which is to be implanted. As shown in  FIG. 1 , these indicia are referenced to the most proximal portion  84  of the great trochanter  86  of the patient&#39;s femur  16 . The index  82  which lines up with proximal portion  84  provides the surgeon with information regarding selecting the appropriate neck geometry for the femoral component. Additional notations can be included on broach shell  26  to indicate the sleeve cone sizes for which the broach shell  26  is appropriate (see reference numeral  88  in  FIG. 1 ). A general reference number  90  to the cone size can also be imprinted on the broach shell  26 .  
         [0038]     The broach shells  26  and pilot stems  42  utilized with the present invention, are similar to miller shells and pilot stems utilized with triangular millers. Miller shells and pilot stems are disclosed in U.S. Pat. No. 5,540,694, which is incorporated herein by reference.  
         [0039]     In the illustrated embodiment, broach tool  22  includes a shaft  48  having a longitudinal axis  66  and a triangular broach  34  extending laterally from the shaft  48 . The proximal end  52  of the shaft  48  is configured to couple to the distal end  54  of the driver component  24 . In the illustrated embodiment, as shown, for example, in  FIG. 5 , the distal end  54  of the driver component  24  is formed to include a threaded shaft  53  configured to be received in a threaded cavity  51  formed in the proximal end  52  of the shaft  48  of the broach tool  22 . The distal end  56  of the shaft  48  is configured to be slidably received in the shaft-receiving cavity  46  of the broach shell  26 . The shaft  48  includes an intermediate anti-rotation plate portion  58  disposed between a distal rod portion  60  and a proximal rod portion  62 . The plate portion  58  is symmetrical about the plane of symmetry  33  of the triangular broach  34 .  
         [0040]     The longitudinal axis  66  of the shaft  48  of the broach tool  22 , when the shaft  48  is received in the broach shell  26 , as shown, for example, in  FIG. 1 , coincides with the longitudinal axis  40  of broach shell  26 . Shaft  48  is sized to fit and slide longitudinally within shaft-receiving cavity  46  of broach shell  26 . When shaft  48  is received in shaft-receiving cavity  46  of the broach shell  26 , the anti-rotation plate  58  extends through the slot  76  formed in the upper portion of the broach shell  26  for longitudinal movement relative to the slot  76 . To that end, anti-rotation plate  58  has a thickness  59  that is slightly less than the width  96  of the slot  76 . In the illustrated embodiment, the thickness  59  of anti-rotation plate  58  is approximately 0.1965 inches while the width  96  of slot  76  is 0.1975 inches. Thus, the side walls of anti-rotation plate  58  and the walls forming slot  76  cooperate to guide the triangular broach  34  and prevent it from rotating while it is being driven through the bone  16  to form the triangular cavity  14 .  
         [0041]     Near the distal end  56  of shaft  48  the hypotenuse  35  of the triangular broach  34  is coupled to the shaft  48 . The hypotenuse  35  of the triangular broach  34  forms an angle  99  with respect to the longitudinal axis  66  of the shaft  48 . Angle  99  corresponds to the angle the projection, or spout, forms with the body of the sleeve of the prosthesis and the angle of the triangular cavity  14  to be formed in the bone. Illustratively, angle  99  is approximately thirty one and eighty-three hundredths degree (31.83°).  
         [0042]     In the illustrated embodiments, the triangular broach  34  is configured as a right triangle having its hypotenuse side  35  extending at an acute angle  99  from adjacent the distal tip  56  of the shaft  48  upwardly and outwardly from the shaft  48 . The upper surface  36  of the triangular broach  34  is generally perpendicular to the longitudinal axis  66  of the shaft  48 . The upper surface  36  of the triangular broach  34  is displaced longitudinally from the distal end of the proximal rod portion  62  by a distance  43 . In the illustrated embodiment, distance  43  is greater than the length  75  of slot  76  to facilitate insertion and removal of a broach tool  22  into the shell  26  without removal of the shell from the bone  16 , as shown, for example, in  FIG. 11 . The side surface  39  of the triangular broach  34  is generally parallel to the longitudinal axis  66  and is displaced therefrom by a distance  41  approximately equal to the radius of the proximal rod portion  62  of the shaft  48 .  
         [0043]     At the corner  37  of the triangular broach  34  formed by the upper surface  36  and hypotenuse side  35 , the broach tool  22  has a maximum width  32  (measured from the shaft  48  to the apex  37  of the triangular broach  34  perpendicular to the longitudinal axis  66  of the shaft  48 ). It is this maximum width  32  that dictates the minimal size of the incision  12  required to perform a prosthetic surgery. Thus, the surgical incision  12  required to use the disclosed guided broach  20  need only be large enough to allow retraction to a width only slightly larger than the maximum width  32  of the guided broach  20 .  
         [0044]     Triangular broach  34  is formed symmetrically about a plane  33  including the longitudinal axis  66  of the shaft  48  of the broach tool  22 . The hypotenuse wall  35  of the triangular broach  34  is curved to smoothly join with the oppositely facing side walls  45  of the triangular broach  34 . The oppositely facing triangular shaped side walls  45  are generally parallel to the plane of symmetry  33  of the triangular broach  34 . The triangular broach  34  is formed to include a plurality of rows of broach teeth  47  formed in the side walls  45  and hypotenuse wall  35 . Illustratively, the each row of the plurality of rows of broach teeth  47  is formed in a plane perpendicular to the plane of symmetry  33  of the triangular broach  34  and the longitudinal axis  66  of the shaft  48  of the broach tool  22 . A plurality of chip breakers  49  are formed in the side walls and hypotenuse wall  35  of the triangular broach  34 . In the illustrated embodiment, each chip breaker  49  is a full rounded channel, as shown for example, in  FIG. 8 . In the side walls  45  each chip breaker  49  runs at an angle with respect to the top surface  36  of the triangular broach  34 . Illustratively, the chip breaker angle is approximately forty-five degrees.  
         [0045]     The disclosed plurality of broach tools  22  include differently sized triangular broaches  34  coupled to the shaft  48  to allow calcar preparation of the femur for receipt of prosthesis having differently sized sleeves or projections from the stem component. Illustratively, broach tools  22  for calcar preparation of a femur for receipt of sleeves of the S-ROM modular prosthesis which includes a plurality of differently sized sleeves have maximum widths  32  of approximately 1.789 inches. For example, seven differently sized broach tools  22  designated 7×12, 9×14, 1 1×1 6, 13×18, 15×20, 17×22 and 19×24, respectively, are provided for use with the S-ROM modular prosthesis system. In such broach tools  22 , the thickness  94  of the triangular broach  34  varies depending on the size of triangular cavity  14  to be prepared. The triangle broaches  34  of broach tools  22  for utilization with the S-ROM modular prosthesis system for example have thicknesses  94  of approximately 0.315, 0.394, 0.472, 0.551, 0.630, 0.709, and 0.787 inches, respectively, to accommodate the plurality of differently sized sleeves provided in such modular prosthesis system. In such broach tools  22 , the length  98  of the triangular broach  34  varies depending on the size of triangular cavity  14  to be prepared. The triangle broaches  34  of broach tools  22  for utilization with the S-ROM modular prosthesis system for example have lengths  98  of approximately 1.780, 1.780, 1.780, 1.780, 1.820, 1.880, and 1.880 inches, respectively, to accommodate the plurality of differently sized sleeves provided in such modular prosthesis system.  
         [0046]     The driver component  24  includes a strike plate  50  coupled to a shaft  68 . Shaft  68  includes a proximal end  70 , a distal end  54  and a longitudinal axis  72 . The strike plate  50  is coupled to the proximal end  70  of shaft  68  as shown, for example, in  FIGS. 1-5 . In the illustrated embodiment, the shaft  68  includes a proximal portion  71  adjacent the proximal end  70  that is a larger diameter than the distal portion  55  adjacent the distal end  54 . The proximal portion  71  is knurled to facilitate gripping the shaft  68  as it is being used to drive the guided broach  20  into the bone  16 . In the illustrated embodiment, the proximal portion  71  of the shaft  68  terminates at a location that would not require insertion of the proximal portion  71  into the incision  12  during the surgical operation.  
         [0047]     The distal portion  55  of the shaft  68  may be partially inserted into the incision  12  during the surgical procedure and portions of the distal portion  55  may even be received in the shaft-receiving cavity  46  of the broach shell  26 . Thus, the distal portion  55  of the shaft  68  has a diameter  57  approximately equal to the diameter  63  of the proximal rod portion  62  and the diameter  61  of the distal rod portion  60  of the shaft  48  of the broach tool  22 . In the illustrated embodiment, diameters  57 ,  61  and  63  are approximately 0.372 inches to facilitate receipt of the distal portion  55  of the shaft  68  and the proximal rod portion  62  and distal rod portion  60  of the shaft  48  of the broach tool  22  in the shaft-receiving cavity  46  of the broach shell  26  for longitudinal movement of the guided broach  20  relative to the shell  26 .  
         [0048]     The distal portion  55  of the illustrated shaft  68  is formed to include witness marks  30 . The witness marks  30  are utilized in the same manner as witness marks are utilized in currently available triangle milling devices. For example, in the illustrated embodiment, three witness marks  30  are provided on the distal portion  55  of the shaft  68  corresponding to three differently sized sleeves available in the modular prosthesis (small, large and double extra large). The small sleeve witness mark  27  is located closest to the distal end  54  of the shaft  68  with the large sleeve witness mark  29  disposed between the double extra large witness mark  31  and the small sleeve witness mark  27 .  
         [0049]     When the triangular broach  34  contacts bone  16  during calcar preparation, broaching is stopped if a witness mark  30  is currently adjacent an indicator mark  28  (illustratively the proximal end of the broach shell  26 ) and the sleeve corresponding to that witness mark  30  is utilized during prosthesis installation. Otherwise, broaching is continued to remove enough of the bone  16  to bring the next witness mark  30  adjacent the indicator mark  28  and the sleeve corresponding to that witness mark is utilized during prosthesis installation.  
         [0050]     Thus, if for example, a surgeon through pre-surgical analysis determines that a small sleeve of a modular prosthesis system, should be utilized in the prosthesis, the surgeon would initially drive the guided broach  20  into the bone  16  until the small sleeve witness mark  27  is adjacent the indicator mark  28  on the shell  26 . If at this time, the broach  34  has contacted bone  16  of the appropriate consistency, broaching would be stopped and the small sleeve would be utilized with the modular prosthesis. If bone has not been contacted by the triangular broach  34  or the contacted bone is not of the appropriate consistency, broaching would be continued until the large sleeve indicator mark  29  is adjacent the indicator mark  28  on the shell  26 . If at this time, the broach  34  has contacted bone  16  of the appropriate consistency, broaching would be stopped and the large sleeve would be utilized with the modular prosthesis. If at that time bone has not been contacted by the triangular broach  34  or the contacted bone is not of the appropriate consistency, broaching would be continued until the double extra large sleeve indicator mark  31  is adjacent the indicator mark  28  on the shell  26  and the double extra large sleeve would be utilized with the modular prosthesis.  
         [0051]     As discussed above, broach tool  22  and broach shell  26  include indicators  28 ,  30 . The illustrated indicators or witness marks  30  comprise three indices  27 ,  29 ,  31  corresponding to three different triangles, referred to as small (“SML”), large (“LRG”), and double extra large (“XXL”) in the figures. More or less indices can be used as desired and, of course, can be otherwise designated. Illustratively, indicator  28  comprises the upper end of broach shell  26 . However, it is within the scope of the disclosure for broach shell  26  to include other structures or indicia thereon acting as indicator  28  for alignment with indicators  30  of guided broach  20 .  
         [0052]     Those skilled in the art will recognize that the position of the witness marks  30  may be varied to permit the witness marks to be aligned with other indicia of the appropriate size of sleeve to be selected. For instance, the witness marks may be positioned along the shaft  48  of the broach tool  22  to align with indicia on the broach shell  26 , witness marks may be provided on the broach tool  22  that align with indicia on the broach shell  26  or witness marks may be provided on the broach shell  26  that align with indicia on the broach tool  22 . It is within the scope of the disclosure for other indicia to be provided from which the surgeon can determine when to stop broaching the bone and from which the surgeon can determine the appropriate sleeve to select from a modular prosthesis system.  
         [0053]     The strike plate  50  is a rounded circular plate including a top surface  78  configured to be struck by a mallet and a planar bottom surface  80  substantially perpendicular to the longitudinal axis  72  of the driver  24 . In the illustrated embodiment, shaft  68  is welded to strike plate  50 . The top surface  78  of the strike plate  50  facilitates exerting downward pressure on the guided broach  20  during the broaching process. The strike plate  50  can also be used to remove the broach tool  22 . Removal of the broaching system  10  from the bone cavity may be accomplished by striking the bottom surface  80  of the strike plate  50  with a mallet. The strike plate  50  also facilitates extraction of the broach tool  22 , broach shell  26  and pilot stem  42  following bone cutting (see below).  
         [0054]     As mentioned previously triangular broach  34  has a thickness  94  that is greater than the width of the slot  76 . Illustratively, thickness  94  of triangular broach  34  is equal to or exceeds approximately 0.315 inches. Thus, when the guided broach is slid upwardly within the broach shell  26 , the triangular broach  34  cannot fit within slot  76 . Therefore, the top surface  36  of the triangular broach engages broach engagement surface  74  adjacent the distal opening of slot  76  during upward movement of the guided broach  20 . The engagement of top surface  36  of the triangular broach  34  with broach engagement surface  74  transfers removal forces applied to the guided broach  20  to the broach shell  26  facilitating removal of the broach shell  26  and the pilot stem  42  coupled thereto from the bone  16 .  
         [0055]     Referring now to  FIG. 1  there is shown a broach assembly  19  formed from a broach shell  26 , a broach tool  22 , a pilot stem  42  and a driver component  24  of the broaching system  10 . The broach tool  22  is slidably received in the broach shell  26  for reciprocal movement along the longitudinal axis  40  of the broach shell  26 . The pilot stem  42  is received in a previously reamed cylindrical cavity. Pilot stem  42  is coupled to broach shell  26  to align the axis  40  of broach shell  26  relative to the cylindrical cavity. The frustoconical surface  44  of the broach shell  26  is received in the previously reamed conical cavity. The pilot stem  42  and broach shell  26  are selected from the plurality of pilot stems  42  and broach shells  26  based on the size of the reamers used to form the cylindrical and conical cavities, respectively.  
         [0056]     As shown, for example, in  FIGS. 1-6 , the broach tool  22  includes a distal rod portion  60  and proximal rod portion  62  coupled to the anti-rotation plate  58  to which the triangular broach  34  is coupled. Anti-rotation plate  58  and the distal portion  60  and proximal portion  62  of the shaft  48 , are all aligned as shown, for example, in  FIG. 4 , so that they slide within the shaft-receiving cavity  46  and slot  76  formed in broach shell  26 . Anti-rotation plate  58  engages the walls of the laterally opening slot  76  in broach shell  26  to prevent rotation of the triangular broach  34  with respect to the shell  26  during calcar preparation. As the broach tool  22  is reciprocated upwardly (proximally) within the broach shell  26 , the top surface  36  of the triangular broach  34  comes into engagement with the broach engagement surface  74  adjacent the distal end of the slot  76  in the broach shell  26 . Thus, removal of the broach tool  22  from the calcar cavity induces the broach shell  26  and pilot stem  42  to be removed from the straight and conically reamed cavities in the intramedullary canal  18 .  
         [0057]     During assembly of a broach assembly  19  from components of the broaching system  10 , an appropriately sized broach shell  26  is selected and an appropriately sized pilot stem  42  is coupled to the distal end of the broach shell  26 . The broach shell  26  and pilot stem  42  are selected based on the size of the straight and conical reamers used to prepare the intramedullary canal  18 . The driver component  24  is coupled to the broach tool  22  which is assembled into broach shell  26 . Illustratively, a threaded shaft  53  extends from the distal end  54  of the driver component  24  that is configured to be received in a threaded cavity  51  formed in the proximal end  52  of the broach tool  22 .  
         [0058]     As shown, representatively by two broach tools  22  in  FIG. 2 , a family of broach tools  22  is preferably provided to the surgeon with all members of the family having commonly sized shafts  48  to permit assembly of any on of the broach tools  22  with any one of the broach shells  26 . Each broach tool  22  of the family also includes a commonly sized threaded cavity  51  to facilitate assembling any broach tool  22  of the family to the driver component  24  to form a guided broach  20 .  
         [0059]     The broach tool  22  and broach shell  26  are configured so that the guided broach  20  may be inserted and removed from a broach shell  26  seated in the prepared cavities of the bone  16 . As shown, for example, in  FIG. 11 , the longitudinal axis  66  of the broach tool  22  may be tilted at an angle with respect to the axis  40  of the broach shell and the distal rod portion  60  of the shaft  48  may be inserted through the channel  77  into the shaft-receiving cavity  46 . The anti-rotation plate  58  of the broach tool  22  may be slid into the slot  76  in the broach shell  26  while the upper surface  36  of the triangular broach  34  is disposed below the broach engagement surface  74  and the distal end of the proximal rod portion  62  of the shaft is disposed above the proximal end of the broach shell  26 . The guided broach  20  may then be tilted to align the longitudinal axes  66 ,  72  of the broach tool  22  and driver component  24 , respectively, with the longitudinal axis  40  of the broach shell  26 . Once the axes  66 ,  72  and  40  are aligned, the guided broach  20  may be reciprocated longitudinally with respect to the broach shell  26  with the proximal rod portion  62  of the shaft  48  of the broach tool  22  and portions of the distal portion  55  of the driver component  24  being received in the shaft-receiving cavity of the shell  26 . Removal of the guided broach  20  from the broach shell  26  is accomplished in the opposite fashion when it is desired to remove the guided broach  20  from the broach shell  26  while leaving the broach shell seated in the bone  16 .  
         [0060]     The overall procedure in which broaching system  10  is used is similar in most steps to those described in greater detail in the Background of the Invention. Generally, an incision  12  large enough to receive the maximum width  32  of the broach tool  22  is made through which the patient&#39;s femur  16  is prepared. The head of the femur  16  is resected using an osteotome, oscillating saw or other instrument. An osteotome may be utilized to open the femoral canal  18 . The femoral canal  18  is then reamed with a straight reamer  100  to establish an extended cavity and center line for receipt of the distal stem of the femoral prosthesis and the pilot stem  42  of the broaching system  10 , as shown, for example, in  FIG. 9 . As described in the Background and Summary, the straight reaming step may be accomplished utilizing a plurality of straight reaming steps in which reamers  100  having progressively larger diameters are utilized.  
         [0061]     Next, the intramedullary canal  18  of the proximal femur  16  is reamed with conical reamers  102  to form a cavity for receiving the conical portion of a sleeve or a stem of a prosthesis and the frustoconical portion  44  of the broach shell  26  of the broaching system  10 , as shown, for example, in  FIG. 10 . This conical cavity is on the same center line as the straight cavity and the reaming is conducted until the proximal end of the reamer  102  is even with the proximal end of the resected femur. As described in the Background and Summary, the conical reaming step may be accomplished utilizing a plurality of conical reaming steps in which conical reamers  102  having progressively larger maximum and minimum diameters are utilized.  
         [0062]     Components of the broaching system  10  in its assembled form are shown in  FIG. 1  inserted into the proximal end of the femur  16 . The assembled instrument, or broach assembly  19 , includes a guided broach  20 , broach shell  26  and a pilot stem  42 . The guided broach includes a broach tool  22  and a driver component  24 . The broach tool  22 , broach shell  26  and pilot stem  42  are appropriate to 1) the size of the triangular projection of the sleeve which the surgeon wishes to implant, and 2) fit within the straight and conical cavities formed in the bone. As described below, this calcar preparation step may be performed using a single guided broach  20  or a plurality of guided broaches  20  having triangular broaches  34  with progressively increasing thicknesses  94 .  
         [0063]     Specifically, the broach assembly  19  is selected based on the width W of the triangular projection (or spout) of the sleeve which is to be implanted (see  FIG. 1  of incorporated U.S. Pat. No. 5,540,694). The broach shell  26  is selected based on the size of the conical reamer used in step  2 . Specifically, frustoconical portion  44  of broach shell  26  has the same taper and same maximum diameter as the conical reamer. The height of frustoconical portion  44  is preferably slightly less than the height of the conical reamer so that the proximal end of the frustoconical portion  44  can be aligned with the resected end of the femur  16  without bottoming out in the reamed conical cavity. The pilot stem  42  is selected based on the size of the final straight reamer used in step  1  which in turn is selected by the surgeon based on the inside diameter of the patient&#39;s femur  16 .  
         [0064]     To provide the surgeon with the ability to match the finished prosthesis to various patient requirements, sleeves of various sizes and configurations and femoral prostheses having various proximal and distal diameters are provided to the surgeon along with corresponding sets of guided broaches  20 , pilot stems  42 , broach shells  26 , straight reamers and conical reamers. Guided broaches  20  may comprise a plurality of integrally formed broach tools  22  and driver components  24  or a plurality of broach tools  22  and a single driver component  24  configured to mate with each of the plurality of broach tools  22  within the scope of the disclosure.  
         [0065]     The initial insertion of broach assembly  19  into the cavity in the femur brings the proximal end of frustoconical portion  44  into alignment with the proximal end of the resected femur  16 . At this point, the surgeon can use indicia  82  to confirm his or her selection of a neck geometry for the femoral prosthesis. Calcar broaching is accomplished using an appropriately sized pilot stem  42  for the distally reamed canal, an appropriately sized broach shell  26  for the size of the cone milling performed and a guided broach  20 . In the illustrated embodiment, the threaded proximal end of the pilot stem  42  is screwed into a threaded aperture in the distal end of the broach shell  26 . The pilot stem  42  is inserted into the reamed canal  18  until the frustoconical portion  44  of the shell  26  is seated in the conical aperture created during cone milling. The guided broach  20  is configured to be slidably received in the shell  26 . Once the broach  20  is partially inserted into the shell  26 , the assembly  19  is rotated to position the triangular broach  34  of the broach tool  22  over the best available host bone, which may or may not be in the calcar.  
         [0066]     The guided broach  20  is then lowered until the triangular broach  34  of the broach tool  22  makes contact with the cancellous bone. Once in contact with the cancellous bone, a hammer is used to strike the strike plate  50  on the proximal end of the guided broach  20  to drive the triangular broach  34  of the broach tool  22  into the femur until the cortical bone is contacted. Once the cortical bone is contacted, the surgeon examines the witness marks  30  on the shaft  68  of the broach  20  to determine which mark is most closely aligned with the proximal end of the shell  26 . In one embodiment of a method of calcar preparation, three increasingly larger guided broaches  20  are utilized to create the triangular calcar cavity.  
         [0067]     Triangular broach  34  is then driven into the bone  16  by impacting the driver component  24  with an appropriate instrument or tool, such as a mallet, while broach tool  22  is moved along longitudinal axis  40  of broach shell  26 . This process is continued until the appropriate index  30  on broach tool  22  is aligned with reference surface  28 , e.g., until the “LRG” index  29  is aligned if the sleeve to be inserted is to have a “LRG” triangular projection. In some cases, the original choice of triangular projection may be too small to reach the patient&#39;s hard calcar bone at the proximal end of the femur  16 , in which case the cutting of the triangular cavity  14  would be continued to the next index mark  30  and a further evaluation would be made at that point. If suitable at this point, a sleeve having a triangular projection portion or spout corresponding to the index mark  30  to which the cutting was continued would be used. Depending upon the circumstances, all or portions of the process may be repeated until a suitable fit is achieved.  
         [0068]     The broach assembly  19  is removed from the patient&#39;s femur by pulling guided broach  20  straight out using the strike plate  50  of the driver component  24 . During removal the top surface  36  of the triangular broach  34  engages with surface  74  of broach shell  26 . A light tap on the strike plate  50  from below with a hand, mallet, or other instrument, is usually sufficient to release broach shell  26  from the patient&#39;s bone allowing complete removal of the broach assembly  19 . Implantation of the femoral prosthesis then follows.  
         [0069]     In one embodiment of a method of broaching the triangular cavity  14  in a bone  16 , guided broaches  20  having triangular broaches  34  with progressively wider thicknesses  94  are utilized sequentially to form the triangular cavity  14 . As described above, in one embodiment of the broaching system  10  for use in preparation of a bone for receipt of an S-ROM modular prosthesis, seven broach tools are provided designated sizes 7×12, 9×14, 1 1×16, 13×18, 15×20, 17×22 and 19×24. These sizes correspond to the sizes of sleeves available in the modular prosthesis system. Thus, if the surgeon intends to utilize a size 13×18 sleeve, the initial guided broach  20  selected for calcar preparation would include the size 9×14 broach tool  22 . After broaching the triangular cavity  14  to the appropriate depth using the 9×14 broach tool  22 , the guided broach  20  would be removed from the broach shell  26  and the 9×14 broach tool  22  would be replaced with the 11×16 broach tool  22 . The guided broach  20  including the 11×16 broach tool  22  would then be inserted into the broach shell  26  and driven into the bone  16  to the appropriate depth. The guided broach  20  would then again be removed from the broach shell  26  and the 11×16 broach tool  22  would be replaced with the 13×18 broach tool  22 . The guided broach  20  including the 13×18 broach tool  22  would then be inserted into the broach shell  26  and driven into the bone  16  to the appropriate depth. The guided broach  20  would then be pulled straight up until the top surface  36  of the triangular broach  34  engages the broach engagement surface  74  of the broach shell  26  and the guided broach  20 , broach shell  26  and pilot stem  42  would be removed from the femur  16 .  
         [0070]     Broaching system  10  is fabricated using conventional techniques used in the manufacture of surgical instruments. Similarly, the broaching system  10 , is composed of conventional stainless steels or other materials employed in constructing surgical instruments.  
         [0071]     Although specific embodiments of the invention have been described herein, other embodiments may be perceived by those skilled in the art without departing from the scope of the invention as defined by the following claims. For example, although the invention has been described in terms of the implantation of the femoral portion of a hip prosthesis, it can be used with prostheses for other joints such as the shoulder, knee, or elbow.