Abstract:
A modular implant system includes a set of anatomically-designed diaphyseal fitting and filling modular implant components and adapters for connection to another implant component such as a modular articular component, a segmental component or an intercalary component. The other end of each diaphyseal component is a tapered porous surface. The tapered porous surface is received with a tapered bore in the bone diaphysis that is prepared to match the size and shape of the tapered porous surface. The diaphyseal implant is easy to insert and remove, does not bind before fully seating, and is designed to prevent stress shielding. The diaphyseal sleeve eliminates the long lever arm created when fixation occurs only at the tip of the stem, and should therefore eliminate related stem loosening.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present invention claims priority to U.S. Provisional Patent Application Ser. No. 60/637,015, filed on Dec. 17, 2004 by Robert K. Heck and Stephen A. Hazebrouck and entitled “Modular Implant System and Method with Diaphyseal Implant,” U.S. Provisional Patent Application Ser. No. 60/731,999, filed on Oct. 31, 2005 by Robert K. Heck and Stephen A. Hazebrouck, and entitled “Modular Diaphyseal and Collar Implant,” and U.S. Provisional Patent Application Ser. No. 60/732,402, filed on Oct. 31, 2005 by Robert K. Heck and Stephen A. Hazebrouck and entitled “Modular Implant System and Method with Diaphyseal Implant and Adapter,” all of which are incorporated by reference herein in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to prosthetic joints and, more particularly, to modular orthopaedic lower extremity implant systems. 
     The knee joint basically consists of the bone interface of the distal end of the femur and the proximal end of the tibia. Appearing to cover or at least partially protect this interface is the patella which is a sesamoid bone within the tendon of the long muscle (quadriceps) on the front of the thigh. This tendon inserts into the tibial tuberosity and the posterior surface of the patella is smooth and glides over the femur. 
     The distal femur is configured with two knob like processes (the medial condyle and the lateral condyle) which are substantially smooth and which articulate with the medial plateau and the lateral plateau of the tibia, respectively. The plateaus of the tibia are substantially smooth and slightly cupped thereby providing a slight receptacle for receipt of the femoral condyles. 
     The hip joint consists of the bone interface of the proximal end of the femur and the acetabulum of the hipbone. The proximal femur is configured with a ball-shaped head, which is received within and articulates against the cup-shaped cavity defined by the acetabulum. 
     When the knee or hip joint is damaged whether as a result of an accident or illness, a prosthetic replacement of the damaged joint may be necessary to relieve pain and to restore normal use to the joint. Typically the entire joint is replaced by means of a surgical procedure, which involves removal of the surfaces of the corresponding damaged bones and replacement of these surfaces with prosthetic implants. This replacement of a native joint of the leg with a prosthetic joint is referred to as primary total-knee arthroplasty and primary total-hip arthroplasty. 
     On occasion, the primary prosthesis fails. Failure can result from many causes, including wear, aseptic loosening, osteolysis, ligamentous instability, arthrofibrosis and patellofemoral complications. When the failure is debilitating, revision surgery may be necessary. In a revision, the primary prosthesis is removed and replaced with components of a revision prosthetic system. 
     Implant systems for both primary and revision applications are available from a variety of manufacturers, including DePuy Orthopaedics, Inc. of Warsaw, Ind. DePuy and others offer several different systems for both primary and revision applications. For example, DePuy Orthopaedics offers the P.F.C. SIGMA® Knee System, the LCS® Total Knee System, and the S-ROM Modular Total Knee System. Each of these orthopaedic knee systems includes several components, some appropriate for use in primary knee arthroplasty and some appropriate for use in revision surgery. 
     DePuy Orthopaedics also offers other orthopaedic implant systems for other applications. One such system is the LPS System. The LPS System is provided for use in cases of neoplastic diseases (e.g., osteosarcomas, chrondrosarcomas, giant cell tumors, bone tumors) requiring extensive resections and replacements of the proximal and/or distal femur, severe trauma, disease (e.g., avascular necrosis, osteoarthritis and inflammatory joint disease requiring extensive resection and replacement of the proximal and/or distal femur, and resection cases requiring extensive resection and replacement of the proximal, distal or total femur or proximal tibia (e.g., end-stage revision). Any of these conditions or a combination thereof can lead to significant amounts of bone loss. The LPS System provides components that can replace all or significant portions of a particular bone, such as the femur or tibia. The DePuy LPS System is described more fully in U.S. patent application Ser. No. 10/135,791, entitled “Modular Limb Preservation System”, filed Apr. 30, 2002 by Hazebrouck et al., U.S. Pat. Publication No. US2003/0204267A1 (published Oct. 30, 2003) which is incorporated by reference herein in its entirety. Other companies also offer systems for similar indications. 
     The LPS system provides a comprehensive set of modular implants capable of addressing a wide range of orthopaedic conditions. Components of the LPS system can be combined in a variety of ways to account for variations in patient anatomy and differences in the amount of native bone remaining. As disclosed in U.S. Pat. Publication No. US2003/0204267A1, the modular components can be combined to replace the proximal or distal femur, total femur, proximal tibia or the mid-shaft of a long bone. Similar systems can be used with other long bones, such as the bones of the upper arm. 
     Many of the combinations of components possible with the LPS system include stem components that are configured for implantation within the intramedullary canal of the remaining bone. Metaphyseal sleeves are available for use in the LPS system, as disclosed, for example, in U.S. Pat. Publication No. US2005/0107883A1, entitled “Modular Implant System with Fully Porous Coated Sleeve” (filed on Apr. 2, 2004 by Goodfried, Hazebrouck, Lester and Brown), which is incorporated by reference herein in its entirety. However, in some instances, the stem components must be used with implant components that have replaced the entire articulating portion of the bone and the metaphysis of the bone. In some indications, the remaining native bone comprises the diaphysis or shaft of the long bone, and a metaphyseal sleeve cannot be used. 
     An example of a long bone is illustrated in  FIG. 1 ; in  FIG. 1 , the bone  10  is the femur.  FIG. 2  illustrates the femur of  FIG. 1  after the distal articulating end  12  and metaphysis  14  of the bone  10  have been removed due to neoplastic disease, trauma, disease or as part of an end-stage revision. The diaphysis of the bone is illustrated at  16  in  FIGS. 1-2 . 
     As shown in  FIG. 2 , the intramedullary canal  18  of the diaphysis  16  of the long bone  10  generally tapers, while the implant stem extensions  20  generally have parallel sides, such as those shown at  22 ,  24 . As a result, the implant stem extension  20  frequently contacts the native bone tissue at the free end or tip  28  of the stem extension  20 , while leaving gaps  30  along much of the length of the stem extension  20 . Although these gaps  30  could be filled with bone cement, for optimal fixation it is desirable to use porous coated stem extensions. Such porous coated stem extensions tend to bind before becoming fully seated. Consequently, in cases where the stem extension is porous coated to encourage bone ingrowth, the bone ingrowth is frequently limited to the free end  28  of the stem. With bone ingrowth limited to the free end of the stem extension, there is stress shielding of the bone surrounding the remainder of the stem extension, and a long lever arm is created; both of these effects can lead to early loosening of the implant. Additionally, when significant ingrowth does occur and the stem extension must subsequently be removed, the procedure can be difficult. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the need for an implant system that can be effectively used in the diaphyseal region of a long bone and for a surgical method for implanting a system in the diaphyseal region of a long bone. 
     In one aspect, the present invention addresses this need by providing a diaphyseal implant component comprising a first end with a bore, a second end with a bore that is co-axial with the bore at the first end, a longitudinal axis extending from the first end to the second end, a collar portion and a porous tapered outer surface. The longitudinal axis extends through the bores at the first end and second end. The collar portion is between the first end and the second end and surrounds at least a portion of the bore at the first end. The collar portion includes an annular surface disposed perpendicular to the longitudinal axis of the implant component. The porous tapered outer surface is adjacent to the annular surface of the collar and extends toward the second end of the implant. The porous tapered outer surface has a maximum outer diameter nearest the annular surface of the collar and a minimum outer diameter at the second end of the implant component. The annular surface of the collar has an outer diameter greater than the maximum outer diameter of the porous tapered outer surface. 
     In another aspect, the present invention addresses this need by providing an orthopaedic implant kit for replacing a portion of a long bone, the long bone having an articulation portion, a diaphysis and an intramedullary canal. The kit includes a plurality of modular articulation components, a plurality of modular stems, an adapter and a plurality of modular diaphyseal implant components. The modular articulation components are shaped and sized to replace the articulation portion of the long bone. Each modular articulation component includes a tapered bore. The modular stems are shaped to be received in the intramedullary canal of the long bone. Each stem has a free end and an opposite end capable of being connected to another implant component. The adapter has a tapered end sized and shaped to be received in the tapered bore of a selected articulation component for connecting the adapter to the articulation component. The adapter also has a second tapered end. The diaphyseal implant components are capable of being connected to the modular stems. Each diaphyseal implant component has a first end, a second end, a longitudinal axis extending between the first end and the second end, a porous tapered outer surface and a collar. The first end of each diaphyseal implant component has a tapered bore sized and shaped to receive the second tapered end of the adapter for connecting the diaphyseal implant component to one end of the adapter. Each diaphyseal implant component also has a second end for connection to a selected modular stem. The porous tapered surface of each diaphyseal implant component has a minimum outer dimension at the second end and a maximum outer dimension positioned between the first end and the second end. The collar is adjacent to the porous tapered outer surface. The collar includes an annular surface adjacent to the porous tapered outer surface. The annular surface is transverse to the longitudinal axis of the diaphyseal implant component. 
     In another aspect, the present invention provides a method of replacing a portion of a long bone, the long bone having an articulation portion, a diaphysis, an intramedullary canal and a periosteum. A plurality of modular bone replacement components shaped and sized to replace a portion of the long bone are provided; each modular bone replacement component including a tapered bore. A plurality of modular stems to be received in the intramedullary canal of the long bone are provided; each stem has a free end and an opposite end capable of being connected to another implant component. An adapter having a tapered end sized and shaped to be received in the tapered bore of a bone replacement component is provided; the adapter further comprises a second tapered end. A plurality of modular diaphyseal implant components capable of being connected to the modular stems are provided. Each diaphyseal implant component includes a first end having a tapered bore sized and shaped to receive the second tapered end of the adapter for connecting the diaphyseal component to one end of the adapter. Each diaphyseal implant component also includes a second end for connection to a selected modular stem. A longitudinal axis extends between the first end and the second end. Each diaphyseal implant component has a porous tapered outer surface having a minimum outer dimension at the second end and a maximum outer dimension positioned between the first end and the second end. Each diaphyseal implant component also has a collar adjacent to the porous tapered outer surface. The collars include a porous cylindrical surface surrounding the longitudinal axis of the diaphyseal implant component. The bone is resected to remove a portion of the bone and leave at least a portion of the diaphysis of the bone. A tapered bore is prepared in the diaphysis of the bone. A stem component, diaphyseal component and bone replacement component are selected. An implant assembly is made by connecting the selected stem component to the selected diaphyseal component, inserting one end of the adapter into the tapered bore of the selected diaphyseal component and inserting the other end of the adapter into the tapered bore of the selected bone replacement component. The implant assembly is implanted so that the stem component is received in the intramedullary canal, a substantial part of the diaphyseal component is received in the tapered bore in the diaphysis of the bone and the collar is exposed outside of the bone. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an anterior view of a left femur; 
         FIG. 2  is a cross-section of a portion of the diaphysis of the femur of  FIG. 1 , shown with a stem extension received in the intramedullary canal of the femur; 
         FIG. 3  is an elevation of a set of diaphyseal implant components of one embodiment of a set of orthopaedic implant components embodying the principles of the present invention; 
         FIG. 3A  is an elevation of an adapter for use with the diaphyseal implant components of  FIG. 3 ; 
         FIG. 4  is a longitudinal cross-section of the set of diaphyseal implant components of  FIG. 3 ; 
         FIG. 4A  is a longitudinal cross-section of the adapter of  FIG. 3A ; 
         FIG. 5  is an end view of one of the diaphyseal implant components of  FIGS. 3-4  taken along line  5 - 5  of  FIG. 3 ; 
         FIG. 6  is an end view of the diaphyseal implant component of  FIG. 5 , taken along line  6 - 6  of  FIG. 3 ; 
         FIG. 7  is an elevation of one of the diaphyseal implant components of  FIGS. 3-4 , assembled with the adapter of  FIGS. 3-4  and with a stem extension and intercalary implant component, shown with the diaphyseal implant component and intercalary implant component in longitudinal cross-section; 
         FIG. 8  is an exploded perspective view of a distal femoral implant assembly illustrating use of one of the diaphyseal implant components of  FIGS. 3-4  in use with an adapter and one style of stem extension; 
         FIG. 9  is an exploded perspective view similar to  FIG. 8 , but illustrating use of one of the diaphyseal implant components of  FIGS. 3-4  in use with an adapter and a different style of stem extension; 
         FIG. 10  is a side view of a distal femoral implant assembly including one of the diaphyseal implant components and adapter of  FIGS. 3-4  in use with a different style of stem extension; 
         FIG. 11  is an anterior view of the distal femoral implant assembly of  FIG. 10 ; 
         FIG. 12  is a side view of a proximal femoral implant assembly including one of the diaphyseal implant components and adapter of  FIGS. 3-4 ; 
         FIG. 13  is a perspective view of a proximal tibial implant assembly including one of the diaphyseal implant components and adapter of  FIGS. 3-4 ; 
         FIG. 14  is a side view of an intercalary implant assembly including two of the diaphyseal implant components and two of the adapters of  FIGS. 3-4 ; 
         FIG. 15  is a side view of an intercalary implant assembly including one of the diaphyseal implant components and adapter of  FIGS. 3-4 ; 
         FIG. 16  is a diagrammatic cross-section of a portion of the remaining portion of the diaphysis after a portion of the femur or long bone has been resected; 
         FIG. 17  illustrates the remaining resected diaphysis of  FIG. 16  after a tapered bore has been prepared at the resection site of the bone; and 
         FIG. 18  illustrates the remaining resected diaphysis of  FIG. 17  with an implant assembly including a diaphyseal implant component fully seated in the bone. 
     
    
    
     DETAILED DESCRIPTION 
     A modular orthopaedic knee implant system incorporating the principles of the present invention is illustrated in the accompanying drawings. The illustrated modular orthopaedic knee implant system includes components of several existing orthopaedic knee implant systems, along with new components that provide the orthopaedic-surgeon with greater flexibility in selecting the appropriate components to suit the needs of an individual patient. These patient needs can include factors such as individual anatomy and the condition of the native bone tissue. 
       FIG. 3  illustrates a set  50  of diaphyseal implant components that can be used in the system or kit of the present invention. The illustrated set  50  of diaphyseal implant components includes five sizes of diaphyseal components, labeled  52 A,  52 B,  52 C,  52 D,  52 E. The illustrated diaphyseal components  52 A,  52 B,  52 C,  52 D,  52 E include several common features. In the following description and in the drawings, like parts are identified with the same reference number, followed by a letter designation to identify the particular size of component. 
     Each of the illustrated diaphyseal components  52 A,  52 B,  52 C,  52 D,  52 E has a first end  54 A,  54 B,  54 C,  54 D,  54 E a second end  56 A,  56 B,  56 C,  56 D,  56 E and a longitudinal axis  58 A,  58 B,  58 C,  58 D,  58 E extending from the first end  54 A,  54 B,  54 C,  54 D,  54 E to the second end  56 A,  56 B,  56 C,  56 D,  56 E. Each of the illustrated diaphyseal components  52 A,  52 B,  52 C,  52 D,  52 E also has a collar portion  59 A,  59 B,  59 C,  59 D,  59 E and a tapered outer surface  60 A,  60 B,  60 C,  60 D,  60 E. 
     The tapered outer surface  60 A,  60 B,  60 C,  60 D,  60 E of each diaphyseal implant component  52 A,  52 B,  52 C,  52 D,  52 E in the set  50  is of a different size to accommodate the needs of the individual patient&#39;s anatomy. The illustrated set includes sizes ranging from extra-extra-small  52 A to large  52 E. 
     The tapered outer surface  60 A,  60 B,  60 C,  60 D,  60 E of each diaphyseal implant component  52 A,  52 B,  52 C,  52 D,  52 E in the set  50  has a minimum outer diameter at the second end  56 A,  56 B,  56 C,  56 D,  56 E and a maximum outer diameter spaced from the first end  54 A,  54 B,  54 C,  54 D,  54 E and the second end  56 A,  56 B,  56 C,  56 D,  56 E. The maximum outer diameter is indicated at  66 A,  66 B,  66 C,  66 D,  66 E in  FIG. 3 . 
     The tapered outer surface  60 A,  60 B,  60 C,  60 D,  60 E,  60 F may have a plurality of flats  68 A,  68 B,  68 C,  68 D,  68 E at the maximum outer diameter  66 A,  66 B,  66 C  66 D,  66 E. The flats may be provided to help to limit rotation of the diaphyseal components  52 A,  52 B,  52 C,  52 D,  52 E with respect to the bone after implantation, as described in more detail below. It should be understood that the diaphyseal implant components could be provided without such flats if desired. 
       FIG. 5  illustrates an end view of one of the diaphyseal implant components  52 D of the set  50 , taken from the second end  56 D of the component. As there shown, the tapered outer surface  60 D has four equally spaced flats  68 D connected by curved arcs  70 D. The maximum outer dimensions of the tapered outer surface  60 D are shown at d 1  and d 2  in  FIG. 5 ; in the illustrated embodiments, d 1 =d 2 . Thus, the tapered outer surface  60 D has the same outer dimension d 1 , d 2  along two perpendicular transverse axes at the maximum outer dimension  66 D of the tapered outer surface  60 D. 
     In the smallest size of diaphyseal implant component  52 A most of the tapered outer surface  60 A has a frustoconical shape, shown at  71 A in  FIG. 3 . Frustoconical is intended to mean shaped like the frustum of a cone, that is, it has the shape of the basal part of a solid cone formed by cutting off the top by a plane parallel to the base. The smallest illustrated diaphyseal implant component  52 A also has a first annular step  72 A and a last annular step  74 A. In each of the other sizes of diaphyseal implant components  52 B,  52 C,  52 D,  52 E in the set  50 , the tapered outer surface  60 B,  60 C,  60 D,  60 E comprises a plurality of annular steps: there is a first step  72 B,  72 C,  72 D,  72 E between the first end  54 B,  54 C,  54 D,  54 E and second end  56 B,  56 C,  56 D,  56 E of the diaphyseal implant components, a last annular step  74 A,  74 C,  74 D,  74 E at the second end  56 B,  56 C,  56 D,  56 E of the diaphyseal implant component and a plurality of intermediate steps  76 B,  76 C,  76 D,  76 E between the first step  72 B,  72 C,  72 D,  72 E and last step  74 A, 74 C,  74 D,  74 E. 
     Each step has a substantially cylindrically shaped outer surface and a longitudinal height; the largest diameter steps deviate from a cylindrical shape in the illustrated embodiments because of the presence of the four flats  68 . 
     In each illustrated size of diaphyseal implant component, the first annular step  72 A,  72 B,  72 C,  72 D,  72 E has the greatest maximum outer diameter, and the maximum outer diameter of each step progressively decreases to the last annular step  74 A,  74 A,  74 C,  74 D,  74 E which has the smallest maximum outer diameter. In the illustrated set of diaphyseal implant components  52 A,  52 B,  52 C,  52 D,  52 E examples of sizes and numbers of steps are provided in the following table: 
     
       
         
               
             
               
               
               
               
             
               
             
               
               
               
               
             
               
             
               
               
               
               
             
               
             
               
               
               
               
             
               
             
               
               
               
               
             
           
               
                   
               
             
             
               
                 Extra Extra Small Diaphyseal Implant Component 52A 
               
             
          
           
               
                   
                   
                 Outer 
                   
               
               
                   
                 Height 
                 Diameter 
                 Taper Angle 
               
               
                   
               
               
                 First step 72A 
                 2 mm 
                 12.95 mm 
                 — 
               
               
                 Frustoconical 
                 15.04 mm    
                 12.65 mm 
                 3°      
               
               
                 Portion 71A 
                   
                 maximum 
               
               
                   
                   
                 to 10.67 mm 
               
               
                   
                   
                 minimum 
               
               
                 Last Step 74A 
                 2 mm 
                 9.81 mm 
                 — 
               
               
                   
               
             
          
           
               
                 Extra Small Diaphyseal Implant Component 52B 
               
             
          
           
               
                   
                 Step 
                 Step Outer 
                 Overall 
               
               
                   
                 Height 
                 Diameter 
                 Taper Angle 
               
               
                   
               
               
                 First step 72B 
                 2 mm 
                 15.23 mm 
                 4°52′ 
               
               
                 Second step 
                 4 mm 
                 14.37 mm 
               
               
                 Third step 
                 4 mm 
                 13.51 mm 
               
               
                 Fourth step 
                 4 mm 
                 12.65 mm 
               
               
                 Last step 74B 
                 4 mm 
                 11.79 mm 
               
               
                   
               
             
          
           
               
                 Small Diaphyseal Implant Component 52C 
               
             
          
           
               
                   
                 Step 
                 Step Outer 
                 Overall 
               
               
                   
                 Height 
                 Diameter 
                 Taper Angle 
               
               
                   
               
               
                 First step 72C 
                 2 mm 
                 19.09 mm 
                 4°33′ 
               
               
                 Second step 
                 4 mm 
                 18.37 mm 
               
               
                 Third step 
                 4 mm 
                 17.65 mm 
               
               
                 Fourth step 
                 4 mm 
                 16.93 mm 
               
               
                 Fifth step 
                 4 mm 
                 16.21 mm 
               
               
                 Last step 74C 
                 4 mm 
                 15.49 mm 
               
               
                   
               
             
          
           
               
                 Medium Diaphyseal Implant Component 52D 
               
             
          
           
               
                   
                 Step 
                 Step Outer 
                 Overall 
               
               
                   
                 Height 
                 Diameter 
                 Taper Angle 
               
               
                   
               
               
                 First step 72D 
                 2 mm 
                 22.53 mm 
                 6°35′ 
               
               
                 Second step 
                 4 mm 
                 21.51 mm 
               
               
                 Third step 
                 4 mm 
                 20.49 mm 
               
               
                 Fourth step 
                 4 mm 
                 19.47 mm 
               
               
                 Fifth step 
                 4 mm 
                 18.45 mm 
               
               
                 Sixth step 
                 4 mm 
                 17.43 mm 
               
               
                 Last step 74D 
                 4 mm 
                 16.41 mm 
               
               
                   
               
             
          
           
               
                 Large Diaphyseal Implant Component 52E 
               
             
          
           
               
                   
                 Step 
                 Step Outer 
                 Overall 
               
               
                   
                 Height 
                 Diameter 
                 Taper Angle 
               
               
                   
               
               
                 First step 72E 
                 2 mm 
                 26.51 mm 
                 6°39′ 
               
               
                 Second step 
                 4 mm 
                 25.49 mm 
               
               
                 Third step 
                 4 mm 
                 24.47 mm 
               
               
                 Fourth step 
                 4 mm 
                 23.45 mm 
               
               
                 Fifth step 
                 4 mm 
                 22.44 mm 
               
               
                 Sixth step 
                 4 mm 
                 21.42 mm 
               
               
                 Seventh step 
                 4 mm 
                 20.40 mm 
               
               
                 Last step 74E 
                 4 mm 
                 19.38 mm 
               
               
                   
               
             
          
         
       
     
     In the above table, the Overall Taper Angle refers to the angle defined by a line tangent to the steps  72 ,  74 ,  76  and a line parallel to the longitudinal axis  58  in each size. 
     It should be understood that the sizes, numbers of steps and overall taper angles identified in the above tables are provided as examples only. The present invention is not limited to a stepped configuration or to any particular size, number of steps or overall angle of taper unless expressly called for in the claims. Moreover, although five sizes are illustrated in the set  50 , fewer or more sizes could be provided; the invention is not limited to any number of sizes of implant components in a set unless expressly called for in the claims. 
     In each of the illustrated diaphyseal implant components  52 A,  52 B,  52 C,  52 D,  52 E, most of the tapered outer surface is porous: the frustoconical portion  71 A of the small diaphyseal implant component  52 A and its first step  72 A are porous and all of the first and intermediate steps  72 B,  72 C,  72 D,  72 E,  76 B,  76 C,  76 D,  76 E of the other sizes of diaphyseal implant components  52 B,  52 C,  52 D,  52 E are porous. The last or smallest diameter step  74  in each size is not porous in the illustrated embodiment. 
     As used herein, “porous” refers to a surface that is conducive to bone ingrowth for non-cemented fixation, and “smooth” refers to a surface that is not conducive to such bone ingrowth. Suitable porous surfaces can be made by many different methods: casting, embossing, etching, milling, machining, and coating such as by plasma-spraying or by bonding, for example. Bonded materials can comprise sintered metal beads, sintered metal mesh or screen, or sintered metal fibers, for example. Known, commercially available materials and techniques can be used to create the porous surfaces of the diaphyseal components: for example, POROCOAT® coating, available from DePuy Orthopaedics, Inc. of Warsaw, Ind., could be used, as well as other commercially available coatings. In addition, the porous surfaces may include other materials conducive to bone ingrowth, such as hydroxy apatite coatings, for example. It should be understood that the above-identified examples of materials, methods and commercial products are provided as examples only; the present invention is not limited to any particular material, method or commercial product for the porous surfaces unless expressly called for in the claims. In addition, it should be understood that as additional materials and methods become available to create surfaces that promote bony ingrowth, it is believed that such other materials and methods may also be useful with the present invention. 
     Each of the illustrated flats  68 A,  68 B,  68 C,  68 D,  68 E in the illustrated diaphyseal implant components is 6 mm high. The flats are disposed at 90° intervals around the first step and second step in the diaphyseal implant components  52 B,  52 C,  52 D,  52 E that have stepped tapered outer surfaces  60 B,  60 C,  60 D,  60 E and are also disposed at 90° intervals around the tapered frustoconical surface  71 A and first step  72 A of the smallest diaphyseal implant component  52 A. It should be understood that the flats may have different dimensions and different positions. 
     In each size of diaphyseal implant component illustrated in  FIG. 3 , the largest diameter portion  66 A,  66 B,  66 C,  66 D,  66 E of the tapered outer surface  60 A,  60 B,  60 C,  60 D,  60 E is adjacent to the annular collar  59 A,  59 B,  59 C,  59 D,  59 E. The annular collars  59 A,  59 B,  59 C,  59 D,  59 E have outer diameters greater than the maximum outer diameter  66 A,  66 B,  66 C,  66 D,  66 E of the tapered outer surface  60 A,  60 B,  60 C,  60 D,  60 E. In ea of the illustrated sizes, at least a portion of the outer surface of each collar is cylindrical in shape: in the extra extra small component  52 A and extra small component  52 B, all or substantially all of the outer surface of the collar  59 A is cylindrical in shape; in the other larger sizes  52 C,  52 D,  52 E the collars  59 C,  59 D,  59 E include a cylindrical portion  82 C,  82 D,  82 E adjacent to the tapered outer surface  60 C,  60 D,  60 E and a frustoconical portion  84 C,  84 D,  84 E at the first end  54 C,  54 D,  54 E. A portion or all of each collar  59 A,  59 B,  59 C,  59 D,  59 E may be porous; for example, an annular porous strip having a height (longitudinal dimension) of 10 mm may be provided on the cylindrical portions  82 A.  82 B,  82 C,  82 D,  82 E for soft tissue attachment and ingrowth. Variations in the type and characteristics of the porous coating may be made to encourage soft tissue ingrowth, as opposed to bone ingrowth. Moreover, features may be included on the collar to allow for attachment of soft tissue or the periosteum; for example, suture holes may be provided. Preferably, a portion of each collar portion has a surface that is conducive to ingrowth of the periosteum. 
     Each collar  59 A,  59 B,  59 C,  59 D,  59 E includes a transverse annular surface  86 A,  86 B,  86 C,  86 D,  86 E that is perpendicular to the longitudinal axis  58 A,  58 B,  59 C,  58 D,  58 E of the diaphyseal implant component. The transverse annular surfaces  86 A,  86 B,  86 C,  86 D,  86 E are sized and provide surface areas sufficient to bear against the resected end of the bone if the diaphyseal implant component subsides. For example, the transverse annular surface  86 A,  86 B,  86 C,  86 D,  86 E may have an outer diameter in the range of about 1 inch to 1½ inch (25.4 mm to 38.1 mm) and an inner diameter at the first step  72 A,  72 B,  72 C,  72 D,  72 E in the range of about ½ inch to 1 inch (12.7 mm to 25.4 mm), thus providing surface areas in the range of about 0.59 square inches to about 0.98 square inches (about 380 mm 2  to about 633 mm 2 ). With a porous coating, the diameters should increase by about sixty-thousandths of an inch (1.5 mm) It should be understood that these dimensions are provided as examples only; the present invention is not limited to any particular dimension unless expressly called for in the claims. The transverse annular surface  86 A,  86 B,  86 C,  86 D,  86 E may be porous or smooth; if porous, the transverse annular surface may provide a surface conducive to tissue ingrowth. It may be desirable to limit any porous coating to the outer portions of the transverse annular surface. 
     The diaphyseal implant components  52 A,  52 B,  52 C,  52 D,  52 E may be used with an adapter  88  shown in  FIGS. 3A and 4A  and described in more detail below. 
     Representative cross-sections of the diaphyseal implant components  52 A,  52 B,  52 C,  52 D,  52 E are illustrated in  FIG. 4 . Each of the diaphyseal implant components  52 A,  52 B,  52 C,  52 D,  52 E has a throughbore  90 A,  90 B,  90 C,  90 D,  90 E extending longitudinally through the entire length of the component, from the first end  54 A,  54 B,  54 C,  54 D,  54 E to the second end  56 A,  56 B,  56 C,  56 D,  56 E. In the extra-small and small sizes  52 A,  52 B, the throughbore  90 A,  90 B has a threaded portion shown at  92 A and  92 B in  FIG. 4  to receive the threaded end  114  (shown in  FIG. 9 ) of a stem extension  110 . In the other larger sizes  52 C,  52 D,  52 E of diaphyseal implant components, the portion of the throughbore  90 C,  90 D,  90 E near the second end  56 C,  56 D,  56 E comprises a Morse taper bore  94 C,  94 D,  94 E sized and shaped to receive a Morse taper post  108  at the end of a stem extension  104  or at the end of an adapter. In all of the illustrated diaphyseal implant components, the portion of the throughbore  90 A,  90 B,  90 C,  90 D,  90 E near the first end  54 A,  54 B,  54 C,  54 D,  54 E comprises a larger size Morse taper bore  95 A,  95 B,  95 C,  95 D,  95 E sized and shaped to receive a Morse taper post  96  at one end of the adapter  88 . In the larger sizes of diaphyseal implant components, the smaller Morse taper bores  94 C,  94 D,  94 E are co-axial with and connected to the larger Morse taper bores  95 C,  95 D,  95 E by a transition portion and a cylindrical portion.  FIG. 7  illustrates one of the diaphyseal implant components  52 D in cross-section, assembled with an adapter  88 , segmental implant component  102  and stem extension  104 ; both ends  54 D,  56 D are suitable for connection to other implant components. It should be understood that the illustrated longitudinal throughbores are provided as examples only; other designs could be employed, depending on the desired wall thickness for the implant and the type of connection to be employed to the other implant components. 
       FIGS. 8-9  illustrate the large size diaphyseal implant component  52 E in exploded views with other modular implant components that may be included in a kit or system and assembled with the diaphyseal implant component  52 E for implantation. In  FIGS. 8-9 , the assembly is intended for use in replacing a portion of the distal femur. The assemblies of both  FIGS. 8 and 9  include a distal femoral implant  100 , a segmental implant component  102 , a diaphyseal implant component  52 E, adapters  88 ,  116  and a stem extension. Features of the adapter  116  are disclosed in more detail in U.S. patent application Ser. No. 10/817,051 entitled “Modular Implant System with Fully Porous Coated Sleeve”, filed on Apr. 2, 2004 by Goodfried, Hazebrouck, Lester and Brown (U.S. Pat. Publication No. US2005/0107883A1), the complete disclosure of which is incorporated by reference herein. 
     In  FIG. 8 , the stem extension  104  has a coronal-slotted free end or tip  106 , a body  107  and a connection end  108 . The connection end  108  comprises a Morse taper post in the embodiment of  FIG. 8 . The Morse taper post at the connection end  108  is received within and frictionally locks with the Morse taper bore  94 E of the diaphyseal implant component  52 E. In  FIG. 9 , the stem extension  110  has a free end or tip  112 , a body  113  and a connection end  114  that comprises a male threaded member. The embodiment of  FIG. 9  also includes an adapter  116  with a threaded opening (not shown) to receive the male threaded connection end  114  of the stem extension and a Morse taper post  118  to be received in the Morse taper bore  94 E of the diaphyseal implant component  52 E. All of the large size diaphyseal implant components  52 C,  52 D,  52 E can be assembled with stem extensions in the manners illustrated in  FIGS. 8-9 . Due to constraints on the thicknesses of the walls of the tapered outer surfaces  60 A,  60 B of the smaller sized diaphyseal implant components  52 A,  52 B, accommodation is only made for connection to a stem extension with a threaded male end of the type shown in  FIG. 9 . 
     The bodies  107 ,  113  of the stem extensions  104 ,  110  may vary. For example, a substantial part of the length of the body, such as body  107  of  FIG. 8 , can be porous. Alternatively, the body can be sized and shaped for cemented application, like the body  113  of the stem extension  110  of  FIG. 9 . Alternatively, the body of the stem extension can be splined. 
       FIGS. 10-11  illustrate a stem extension  115  with a coronal slotted free end  117 , a splined body  119 , and a connection end (not shown) comprising a Morse taper post. In the embodiment of  FIGS. 10-11 , the splined body  119  of the stem extension  115  comprises a plurality of cutting flutes. The stem extension  115  of  FIGS. 10-11  is not porous. Although in  FIGS. 10-11  the free end  117  of the stem extension  115  is illustrated as being substantially flat, it may be desirable for the free end  117  to be bullet-shaped. 
     As illustrated in phantom  FIGS. 10-11 , the adapter  88  includes a second Morse taper post  97 , longitudinally aligned with the first Morse taper post  96 . As shown in  FIG. 4A , the adapter also includes a throughbore  99  for pressure relief. The second Morse taper post  97  is sized and shaped to be received within and frictionally lock with a Morse taper bore formed in the femoral component  100 , segmental component  102  or other implant component. U.S. Pat. Publication No. US2003/0204267A1, which is incorporated by reference herein in its entirety, discloses additional details regarding the Morse taper bores in the femoral and segmental components, and of appropriate Morse taper posts for use with such components. 
     As disclosed in U.S. Pat. Publication No. US2003/0204267A1, the distal femoral implant component  100  and segmental component  102  both include tabs  120 . Each of the diaphyseal implant components  52 A,  52 B,  52 C,  52 D,  52 E include corresponding notches  122  to receive the tabs  120  to prevent the diaphyseal implant components from rotating. These notches can also be used to separate the components if necessary; a tool such as that disclosed in U.S. Pat. No. 6,786,931 may be used. 
     It should be understood that a typical implant kit or system would include several sizes of distal femoral implant components  100 , segmental components  102  and stem extensions  104 ,  110 . It should also be understood that depending on the size and shape of the distal femoral component, it may not be necessary to use a segmental component  102 ; the diaphyseal implant component  52 A,  52 B,  52 C,  52 D,  52 E and adapter  88  could be connected directly to the femoral implant component  100 . 
     Use of the diaphyseal implant components  52 A,  52 B,  52 C,  52 D,  52 E of the present invention is not limited to segmental components and femoral components. As illustrated in  FIGS. 12-15 , the diaphyseal implant components of the present invention can be used with other implant components having an articulation portion. For example, as shown in  FIG. 12 , the articulation portion of the implant component could comprise a proximal femoral component  150  (including a femoral head  152 ). As shown in  FIG. 13  the articulation portion of the implant component could comprise a proximal tibia component  154  or other component, such as a proximal humeral component (not shown). 
     As shown in  FIGS. 14-15 , the implant component could be an intercalary implant instead of an articulation component.  FIG. 14  illustrates two large size diaphyseal implant components  52 E in use with a two-piece intercalary implant  156  of the type disclosed in U.S. application Ser. No. 10/403,612 entitled “Intercalary Prosthesis, Kit and Method,” filed Mar. 31, 2003 by Hazebrouck (U.S. Pat. Publication No. US2004/0193268A1), incorporated by reference herein in its entirety, or those disclosed in U.S. application Ser. No. Ser. No. 10/403,357 entitled “Intercalary Implant,” filed on Mar. 31, 2003 by Natalie Heck and Michael C. Jones (U.S. Pat. Publication No. US2004/0193267A1) (also incorporated by reference herein in its entirety). Such implants may be used with intercalary trials such as those disclosed in U.S. patent application Ser. No. 10/952,581, entitled “Orthopaedic Spacer,” filed on Sep. 24, 2004 by Hazebrouck, the complete disclosure of which is incorporated by reference herein.  FIG. 15  illustrates a single diaphyseal implant components in use with the two-piece intercalary component  156  and a standard stem extension  157  for the LPS implant system. 
     In  FIGS. 12-15  the stem extension is shown diagrammatically and indicated generally by reference number  121 , with the free end indicated by reference number  123 . Other than the bullet shape of the free end  123 , no other features are shown for the body  125  of the stem extension. It should be understood that the body  125  of the stem extension  121  in any of  FIGS. 12-15  could have any of the above described features, such as splined cutting flutes, a porous coating, a coronally slotted free end, or could be designed for cemented application. 
     All of the components of the illustrated implant systems can be made of standard materials for such implants, such as titanium and cobalt-chrome alloys. 
     It should be understood that although the principles of the present invention are described and illustrated with reference to implant components available from DePuy Orthopaedics, Inc., the invention is not limited to these components or their features. The principles of the present invention can be applied to other implant components, including those of other manufacturers and those subsequently developed. 
     In use, depending on the condition of the native bone tissue, the orthopaedic surgeon will determine the amount of bone to be resected from the femur (or other long bone). Commercially available instrumentation can be used to resect the bone in the appropriate manner. The diaphysis of a resected bone is illustrated in  FIGS. 16-18  at  200 . If it is desirable to use a diaphyseal implant component  52 A,  52 B,  52 C,  52 D,  52 E to secure the implant in place, the surgeon can then select an appropriate size of diaphyseal implant component  52 A,  52 B,  52 C,  52 D or  52 E for the individual patient. The diaphysis  200  of the bone can then be prepared to receive the selected diaphyseal implant component  52 A,  52 B,  52 C,  52 D or  52 E. The surgeon can use a conical reamer (not shown) of a size and shape matching the size and shape of the selected diaphyseal component to mill or machine the diaphysis  200  of the bone to create a tapered bore that closely matches the size and shape of the tapered outer surface  60 A,  60 B,  60 C,  60 D,  60 E of the selected diaphyseal implant component. A tapered bore is illustrated in  FIGS. 17-18  at  202 . Since the tapered bore is created to match the size and shape of the selected diaphyseal implant component, the implants and techniques of the present invention are adaptable to different patient anatomies. 
     The stem extension and part of the diaphyseal implant component of the assembled implant, can then be inserted into the bone as illustrated in  FIG. 18  and positioned with the tip or free end of the stem extension engaging the bone surface of the intramedullary canal  204  and with the tapered outer surface  60 A,  60 B,  60 C,  60 D or  60 E bearing against the tapered diaphyseal bone defining the tapered bore  202 . The stem extension in  FIG. 18  is identified with reference number  121  and its free end is identified with reference number  123 ; as discussed above with respect to  FIGS. 12-15 , the stem extension  121  is illustrated diagrammatically, and can include any of the features of the stem extensions  104 ,  110 ,  115  described above. Because of the shapes and textures of the implant components  121 ,  52 A,  52 B,  52 C,  52 D or  52 E, there should be no binding before the diaphyseal component  52 A,  52 B,  52 C,  52 D or  52 E is fully seated. Accordingly, implantation should be relatively easy. 
     Generally, when implanted, the first step  72 A,  72 B,  72 C,  72 D,  72 E of each of the diaphyseal implant components  52 A,  52 B,  52 C,  52 D,  52 E will be exposed outside of the bone as shown in  FIG. 18 . Subsequently, some subsidence of the implant can occur over time without damage to the bone. The flats  68 E prevent the diaphyseal component  52 E from rotating or turning in the tapered bore  202  that the surgeon created for it. 
     As shown in  FIG. 18 , when fully seated, the implant assembly contacts the bone at both the tip  123  of the stem extension  121  and at the tapered outer surface  60 E of the diaphyseal component  52 E. Bone ingrowth can occur around the entire tapered outer surface  60 E of the diaphyseal implant component  52 E. Depending on the intramedullary canal anatomy and characteristics of the stem extension, bone ingrowth can also occur along all or part of the body of the stem; for example, bone ingrowth could occur at the free end of the stem extension and/or at any area between the diaphyseal component and the free end of the stem. For example, if a cemented stem extension is used, such as the stem extension  110  of  FIG. 9 , there should be no bone ingrowth along the body of the stem. Similarly, no substantial bone ingrowth should occur along the stem with the splined stem extension  115  of  FIGS. 10-11 . If all or part of the stem extension  104  of  FIG. 8  is porous, bone ingrowth can be expected at the porous area. 
     With the stepped designs of the larger diaphyseal implant components, such as diaphyseal implant components  52 B,  52 C,  52 D,  52 E, shear forces are essentially converted to compressive loads, and the compressive loads are spread among the steps  74 ,  76  contacting the diaphyseal bone defining the tapered bore  202 . Accordingly, the implant is immediately stable and capable of bearing weight. In addition, with the bone bearing the axial load at the tapered bore  202 , there is no disadvantageous stress shielding of the bone. Moreover, with the implant assembly contacting the bone at both the tip  106  of the stem extension and at the contacting surfaces diaphyseal bone defining the tapered bore  202  and tapered outer surface  60 , any moment arm is significantly reduced if not eliminated. With bone ingrowth occurring at both spaced locations over time, long term implant stability should be improved. Accordingly, the implant assembly of the present invention should be less likely to loosen over time. 
     As can be seen in  FIG. 18 , there is a small gap  220  between the exposed resected bone surface and the transverse annular surface  86 E of the collar  59 E when implanted. If the implant does subside, this gap can decrease to the point that the transverse annular surface  86 E bears directly against the exposed resected bone surface. If the transverse annular surface is porous, tissue ingrowth can occur in the gap  220  over time to seal the intramedullary canal  204  against debris. 
     With any of the illustrated diaphyseal implant components, the periosteum of the bone should grow into the porous outer surface of the collar portion  59 A,  59 B,  59 C,  59 D,  59 E of the diaphyseal implant component  52 A,  52 B,  52 C,  52 D,  52 E. Essentially, the ingrowth of tissue along the cylindrical outer surface of the collar portion (or along the exposed portion of the transverse annular surface  86 A,  86 B,  86 C,  86 D,  86 E of the collar portion) should effectively seal off the intramedullary canal, to thereby protect the patient from injury or disease resulting from debris entering into the intramedullary canal. 
     With the modular implant system of the present invention, it should be possible to reduce inventory of the necessary parts in an implant system or kit. 
     It should also be understood that a typical surgical kit would also include trial implant components (not shown) like those shown in  FIGS. 3-4  and  8 - 15 . The surgeon would typically assemble a trial implant and temporarily secure the trial implant assembly in place on the prepared diaphyseal bone to ensure that the assembled implant will be the optimum for the individual patient&#39;s needs. The trial components can have features like those described above for the final implant components. 
     In case it is necessary to ultimately remove the implant assembly from the patient, such removal should not require the removal of excessive bone stock, since it should only be necessary to remove the portion of the diaphysis defining the tapered bore  202 . 
     Various modifications and additions can be made to the above-described embodiments without departing from spirit of the invention. All such modifications and additions are intended to fall within the scope of the claims unless the claims expressly call for a specific construction.