Abstract:
A prosthetic elbow replacement includes a humeral component having a stem dimensioned to fit within a medullary canal of the humerus and having a yoke connected to the stem wherein the yoke terminates in spaced apart arms. A pivot pin is mounted between the arms for rotational movement with respect to the humeral component. The pivot pin has a transverse throughhole. There is an ulnar component having an ulnar stem including a distal end dimensioned to fit within a medullary canal of the ulna and an opposite proximal end dimensioned to fit within a first end opening of the throughhole. The ulnar component has a mounting cap dimensioned to fit within a second end opening of the throughhole. A fastener connects the ulnar stem and the mounting cap such the proximal end of the ulnar stem is positioned within the first end opening of the throughhole and the mounting cap is positioned within the second end opening of the throughhole. The pivot pin rotates to allow for flexion of the prosthetic elbow replacement, and also allows for axial rotation of the ulna component in the humeral component.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. Provisional Patent Application No. 60/816,947 filed Jun. 28, 2006. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0002]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    The invention relates to a bone joint prosthesis, and more particularly to an elbow joint prosthesis used to replace a dysfunctional elbow joint. 
         [0005]    2. Description of the Related Art 
         [0006]    A variety of devices have been developed for elbow prosthetic reconstruction. Some commercially available prosthetic elbow replacement systems include: the Coonrad/Morrey Total Elbow available from Zimmer Inc., the Solar® total elbow system available from Stryker Orthopaedics, the Texx total elbow system available from Biotek, and the Discovery™ total elbow system available from Biomet. Various U.S. patents and U.S. patent applications also describe elbow joint prostheses, bone joint prostheses, and related instrumentation and procedures. See, for example, U.S. Pat. Nos. 2,696,817, 3,772,709, 3,816,854, 3,868,730, 3,939,496, 3,990,117, 4,008,495, 4,079,469, 4,131,956, 4,280,231, 4,293,963, 4,383,337, 4,538,306, 5,061,271, 5,314,484, 5,376,121, 5,723,015, 5,782,923, 5,954,770, 6,027,534, 6,290,725, 6,379,387, 6,699,290, 6,716,248, 6,767,368, 6,890,357, 6,997,957 and U.S. Patent Application Publication Nos. 2003/0208276, 2003/0232124 and 2005/0043806. 
         [0007]    While these known prosthetic elbow replacement systems may be acceptable for certain applications, under certain circumstances some prosthetic elbow replacement systems have disadvantages. For instance, wear debris is one concern with respect to implant replacement of the elbow. This typically occurs if the humeral and ulnar stems are well fixed. The spectrum of pathology requires that a replacement is sometimes indicated in elbows with gross deformity. Thus, a stable implant that can tolerate the stresses at the stem bone interface and still provide some play at the articulation to lessen the likelihood of loosening is ideal. Yet wear of the articulation can occur under these circumstances. 
         [0008]    Thus, there exists a need for an improved prosthetic elbow replacement system that addresses: (i) the instability of unlinked implants, (ii) the need for better wear characteristics than are now available in current linked implants, (iii) the need for a unique design of the ulnar component that lessens the possibility of malalignment, and (iv) the need for a design that allows the implant to be put in without cement should this be desired. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention addresses the foregoing needs by providing a prosthetic elbow replacement system in which a hinge system is incorporated with the humeral component. In contrast to prior prosthetic elbow replacement systems, the hinged portion is enlarged and a central area is prepared in such a way as to receive the ulnar component. The hinge system includes a pivot pin with a throughhole that is tapered anteriorly and posteriorly. The pivot pin is mounted to the humeral component. Thus, the articulation is different from prior prosthetic elbow replacement systems. Specifically, the articulation may include an ulnar stem portion that is drawn into the throughhole in the pivot pin and secured with a fastener (e.g., a screw) and a posterior fitting element (e.g., an ulnar component mounting cap) which constitute other elements of the articulation. Flexion occurs with rotation of the pivot pin. 
         [0010]    In one feature of the invention, the angular relationships of the humeral component and the ulnar component can be very carefully determined to allow about 7 to about 8 degrees of varus/valgus motion. This allows axial rotation of the ulna component in the humeral component as well. An additional important feature is that the articulation is metallic on metallic, thus lessening the likelihood of wear. Texturing of the humeral component and the ulnar component can be of tantalum (or trabecular metal). On the ulnar component, a plasma spray can be used, or the plasma spray can be replaced with tantalum. 
         [0011]    In one aspect, the invention provides a prosthetic elbow replacement including a humeral component, a pivot pin, an ulnar component, and a fastener. The humeral component can have a humeral stem dimensioned to fit within a medullary canal of the humerus, and a yoke connected to the humeral stem. The yoke can terminate in a pair of spaced apart arms. The humeral stem can have a surface section of a porous material. The pivot pin can be disposed between the arms of the humeral component for rotational movement of the pivot pin with respect to the humeral component. The pivot pin can have a transverse throughhole having a first end opening and an opposite second end opening. The ulnar component can have an ulnar stem including a distal end dimensioned to fit within a medullary canal of the ulna and an opposite proximal end dimensioned to fit within the first end opening of the throughhole of the pivot pin. The ulnar stem can have a surface section of a porous material. The ulnar component can also have a mounting cap dimensioned to fit within the second end opening of the throughhole of the pivot pin. The fastener is for connecting the ulnar stem and the mounting cap such that the proximal end of the ulnar stem is positioned within the first end opening of the throughhole of the pivot pin and the mounting cap is positioned within the second end opening of the throughhole of the pivot pin. 
         [0012]    In the prosthetic elbow replacement, an inner surface of the throughhole of the pivot pin can have an inside diameter that decreases from an outer surface of the pivot pin to an inner region of the pivot pin. The proximal end of the ulnar stem can taper inward toward an end surface of the proximal end of the ulnar stem, and an end of the mounting cap can taper inward toward an end surface of the mounting cap, and the end surface of the proximal end of the ulnar stem and the end surface of the mounting cap can be placed in contact when the fastener connects the ulnar stem and the mounting cap. The outer wall of the proximal end of the ulnar stem and an outer wall of the end of the mounting cap can be spaced from the inner surface of the throughhole of the pivot pin when the fastener connects the ulnar stem and the mounting cap. In one form, the inner surface of the throughhole of the pivot pin has a generally hourglass shape, and the outer wall of the proximal end of the ulnar stem and the outer wall of the end of the mounting cap together have a generally hourglass shape when the fastener connects the ulnar stem and the mounting cap. 
         [0013]    The humeral component can include a flange that is spaced from the humeral stem and that extends away from the yoke. The flange can have a curved end integral with the humeral stem and an elongated stem substantially parallel with the humeral stem. The flange can also have a surface section of a porous material. The mounting cap can have a dome shaped top surface, and an inner surface of the yoke of the humeral component can be concave such that the dome shaped top surface of the mounting cap is spaced from the yoke. Each of the arms of the humeral component can include an outwardly facing recess, and the pivot pin can include a first end that rotates in one of the recesses and a second end that rotates in the other recess. 
         [0014]    The proximal end of the ulnar stem, and the mounting cap, and the throughhole of the pivot pin can each be dimensioned to allow for varus/valgus motion of the ulnar component when the fastener connects the ulnar stem and the mounting cap. Preferably, the proximal end of the ulnar stem, and the mounting cap, and the throughhole of the pivot pin are each dimensioned to allow for about 7 to about 8 degrees of varus/valgus motion of the ulnar component. In one form, surfaces of the humeral component that contact the pivot pin consist essentially of metallic material, surfaces of the pivot pin that contact the ulnar component consist essentially of metallic material, surfaces of the ulnar component that contact the pivot pin consist essentially of metallic material, and surfaces of the mounting cap that contact the pivot pin consist essentially of metallic material. As a result, the articulation will be metallic on metallic, thus lessening the likelihood of wear. 
         [0015]    In another aspect, the invention provides a prosthetic joint replacement including a first component, a pivot pin, a second component, and a fastener. The first component can have a first stem dimensioned to fit within a medullary canal of a first bone and a yoke connected to the first stem. The yoke can terminate in a pair of spaced apart arms. The first stem can have a surface section of a porous material. The pivot pin can be disposed between the arms of the first component for rotational movement of the pivot pin with respect to the first component. The pivot pin can have a transverse throughhole having a first end opening and an opposite second end opening. The second component can have a second stem including a distal end dimensioned to fit within a medullary canal of a second bone and an opposite proximal end dimensioned to fit within the first end opening of the throughhole of the pivot pin. The second stem can have a surface section of a porous material. The second component can also have a mounting cap dimensioned to fit within the second end opening of the throughhole of the pivot pin. The fastener is for connecting the second stem and the mounting cap such that the proximal end of the second stem is positioned within the first end opening of the throughhole of the pivot pin and the mounting cap is positioned within the second end opening of the throughhole of the pivot pin. 
         [0016]    In the prosthetic joint replacement, an inner surface of the throughhole of the pivot pin can have an inside diameter that decreases from an outer surface of the pivot pin to an inner region of the pivot pin. The proximal end of the second stem can taper inward toward an end surface of the proximal end of the second stem, and an end of the mounting cap can taper inward toward an end surface of the mounting cap, and the end surface of the proximal end of the second stem and the end surface of the mounting cap can be placed in contact when the fastener connects the second stem and the mounting cap. The outer wall of the proximal end of the second stem and an outer wall of the end of the mounting cap can be spaced from the inner surface of the throughhole of the pivot pin when the fastener connects the second stem and the mounting cap. In one form, the inner surface of the throughhole of the pivot pin has a generally hourglass shape, and the outer wall of the proximal end of the second stem and the outer wall of the end of the mounting cap together have a generally hourglass shape when the fastener connects the second stem and the mounting cap. 
         [0017]    The first component can include a flange that is spaced from the first stem and that extends away from the yoke. The flange can have a curved end integral with the first stem and an elongated stem substantially parallel with the first stem. The mounting cap can have a dome shaped top surface, and an inner surface of the yoke of the first component can be concave such that the dome shaped top surface of the mounting cap is spaced from the yoke. Each of the arms of the first component can include an outwardly facing recess, and the pivot pin can include a first end that rotates in one of the recesses and a second end that rotates in the other recess. 
         [0018]    The proximal end of the second stem, and the mounting cap, and the throughhole of the pivot pin can each be dimensioned to allow for varus/valgus motion of the second component when the fastener connects the second stem and the mounting cap. Preferably, the proximal end of the second stem, and the mounting cap, and the throughhole of the pivot pin are each dimensioned to allow for about 7 to about 8 degrees of varus/valgus motion of the second component. In one form, surfaces of the first component that contact the pivot pin consist essentially of metallic material, surfaces of the pivot pin that contact the second component consist essentially of metallic material, surfaces of the second component that contact the pivot pin consist essentially of metallic material, and surfaces of the mounting cap that contact the pivot pin consist essentially of metallic material. As a result, the articulation will be metallic on metallic, thus lessening the likelihood of wear. 
         [0019]    In yet another aspect, the invention provides a kit for assembly into a prosthetic elbow replacement. The kit includes a humeral component, a pivot pin, an ulnar component, a mounting cap, and a fastener. The humeral component can have a humeral stem dimensioned to fit within a medullary canal of the humerus and a yoke connected to the humeral stem. The yoke can terminate in a pair of spaced apart arms. The humeral stem can have a surface section of a porous material. The pivot pin can be dimensioned to be disposed between the arms of the humeral component for rotational movement of the pivot pin with respect to the humeral component. The pivot pin has an axis of rotation, and a throughhole having a first end opening and an opposite second end opening. The throughhole of the pivot pin can be transverse to the axis of rotation of the pivot pin. The ulnar component can have an ulnar stem including a distal end dimensioned to fit within a medullary canal of the ulna and an opposite proximal end dimensioned to fit within the first end opening of the throughhole of the pivot pin. The ulnar stem can have a surface section of a porous material. The mounting cap can have an end section dimensioned to fit within the second end opening of the throughhole of the pivot pin. The fastener is suitable for connecting the ulnar stem and the mounting cap within the throughhole of the pivot pin. 
         [0020]    In one form, the inner surface of the throughhole of the pivot pin can have an inside diameter that decreases from an outer surface of the pivot pin to an inner region of the pivot pin. The proximal end of the ulnar stem can taper inward toward an end surface of the proximal end of the ulnar stem, and the end section of the mounting cap can taper inward toward an end surface of the mounting cap. The end surface of the proximal end of the ulnar stem and the end surface of the mounting cap can be dimensioned to be placed in mating contact when the fastener connects the ulnar stem and the mounting cap. An outer wall of the proximal end of the ulnar stem and an outer wall of the end section of the mounting cap can be dimensioned to be spaced from an inner surface of the throughhole of the pivot pin when the fastener connects the ulnar stem and the mounting cap. In one embodiment, an inner surface of the throughhole of the pivot pin has a generally hourglass shape, and the outer wall of the proximal end of the ulnar stem and the outer wall of the end section of the mounting cap together have a generally hourglass shape when the fastener connects the ulnar stem and the mounting cap. 
         [0021]    The humeral component can include a flange that is spaced from the humeral stem and that extends away from the yoke. The flange can have a curved end integral with the humeral stem and an elongated stem substantially parallel with the humeral stem. The mounting cap can have a dome shaped top surface, and an inner surface of the yoke of the humeral component can be concave such that the dome shaped top surface of the mounting cap is spaced from the yoke. 
         [0022]    Each of the arms of the humeral component can include an outwardly facing recess, and the pivot pin can include a first end dimensioned to rotate in one of the recesses and a second end dimensioned to rotate in the other recess. The pivot pin can include a body having a cylindrical central section and having an end flange extending radially outward from a first end of the body, a disk, and a pin fastener for fastening the disk to an opposite second end of the body. The end flange can rotate in one of the recesses of the arms of the humeral component and the disk can rotate in the other recess. 
         [0023]    In one form, surfaces of the humeral component that contact the pivot pin consist essentially of metallic material, surfaces of the pivot pin that contact the ulnar component consist essentially of metallic material, surfaces of the ulnar component that contact the pivot pin consist essentially of metallic material, and surfaces of the mounting cap that contact the pivot pin consist essentially of metallic material. In another form, the humeral component consists essentially of metallic material, the pivot pin consists essentially of metallic material, and the ulnar component consists essentially of metallic material. As a result, the articulation in the assembled prosthetic elbow replacement will be metallic on metallic, thus lessening the likelihood of wear. 
         [0024]    In still another aspect, the invention provides a kit for assembly into a prosthetic joint replacement. The kit can include a first component, a pivot pin, a second component, a mounting cap, and a fastener. The first component can have a first stem dimensioned to fit within a medullary canal of a first bone and a yoke connected to the first stem. The yoke can terminate in a pair of spaced apart arms. The first stem can have a surface section of a porous material. The pivot pin can be dimensioned to be disposed between the arms of the first component for rotational movement of the pivot pin with respect to the first component. The pivot pin has an axis of rotation, and a throughhole having a first end opening and an opposite second end opening. The throughhole can be transverse to the axis of rotation of the pivot pin. The second component can have a second stem including a distal end dimensioned to fit within a medullary canal of a second bone and an opposite proximal end dimensioned to fit within the first end opening of the throughhole of the pivot pin. The second stem can have a surface section of a porous material. The mounting cap can have an end section dimensioned to fit within the second end opening of the throughhole of the pivot pin. The fastener is suitable for connecting the second stem and the mounting cap within the throughhole of the pivot pin. 
         [0025]    In one form, the inner surface of the throughhole of the pivot pin can have an inside diameter that decreases from an outer surface of the pivot pin to an inner region of the pivot pin. The proximal end of the second stem can taper inward toward an end surface of the proximal end of the second stem, and the end section of the mounting cap can taper inward toward an end surface of the mounting cap. The end surface of the proximal end of the second stem and the end surface of the mounting cap can be dimensioned to be placed in mating contact when the fastener connects the second stem and the mounting cap. An outer wall of the proximal end of the second stem and an outer wall of the end section of the mounting cap can be dimensioned to be spaced from an inner surface of the throughhole of the pivot pin when the fastener connects the second stem and the mounting cap. In one embodiment, an inner surface of the throughhole of the pivot pin has a generally hourglass shape, and the outer wall of the proximal end of the second stem and the outer wall of the end section of the mounting cap together have a generally hourglass shape when the fastener connects the second stem and the mounting cap. 
         [0026]    The first component can include a flange that is spaced from the first stem and that extends away from the yoke. The flange can have a curved end integral with the first stem and an elongated stem substantially parallel with the first stem. The mounting cap can have a dome shaped top surface, and an inner surface of the yoke of the first component can be concave such that the dome shaped top surface of the mounting cap is spaced from the yoke. 
         [0027]    Each of the arms of the first component can include an outwardly facing recess, and the pivot pin can include a first end dimensioned to rotate in one of the recesses and a second end dimensioned to rotate in the other recess. The pivot pin can include a body having a cylindrical central section and having an end flange extending radially outward from a first end of the body, a disk, and a pin fastener for fastening the disk to an opposite second end of the body. The end flange can rotate in one of the recesses of the arms of the first component and the disk can rotate in the other recess. 
         [0028]    In one form, surfaces of the first component that contact the pivot pin consist essentially of metallic material, surfaces of the pivot pin that contact the second component consist essentially of metallic material, surfaces of the second component that contact the pivot pin consist essentially of metallic material, and surfaces of the mounting cap that contact the pivot pin consist essentially of metallic material. In another form, the first component consists essentially of metallic material, the pivot pin consists essentially of metallic material, and the second component consists essentially of metallic material. As a result, the articulation in the assembled prosthetic joint replacement will be metallic on metallic, thus lessening the likelihood of wear. 
         [0029]    It is therefore an advantage of the invention to provide a prosthetic elbow replacement system that includes improved ulnar articulation. 
         [0030]    It is another advantage of the invention to provide a prosthetic elbow replacement system that includes a rotating pin arrangement such that flexion occurs with rotation of the pivot pin and controlled varus/valgus motion is possible. 
         [0031]    These and other features, aspects, and advantages of the present invention will become better understood upon consideration of the following detailed description, drawings, and appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]      FIG. 1  is an exploded perspective view of the humeral component of a prosthetic elbow replacement according to the invention. 
           [0033]      FIG. 1A  shows the stem of the humeral component of the prosthetic elbow replacement of  FIG. 1  inserted in a humerus. 
           [0034]      FIG. 2  is an exploded perspective view of the ulnar component and the rotating pivot pin of a prosthetic elbow replacement according to the invention. 
           [0035]      FIG. 3  is a perspective view of the ulnar component and the rotating pivot pin of  FIG. 2  in an assembled state. 
           [0036]      FIG. 4  is a side view of the humeral component of  FIG. 1  with the rotating pivot pin assembled in the humeral component. 
           [0037]      FIG. 5  is a partial view of the humeral component and pivot pin taken along line  5 - 5  of  FIG. 4 . 
           [0038]      FIG. 6  is a view taken along line  6 - 6  of  FIG. 5  showing a lateral view of the ulnar component and the rotating pivot pin in an assembled state, the ulnar stem being inserted in the medullary canal of the ulna. 
           [0039]      FIG. 7  is a view taken along line  7 - 7  of  FIG. 4  showing a top view of the ulnar component and the rotating pivot pin in an assembled state, the ulnar stem being inserted in the medullary canal of the ulna. 
       
    
    
       [0040]    Like reference numerals will be used to refer to like parts from Figure to Figure in the following description of the drawings. 
       DESCRIPTION OF THE INVENTION 
       [0041]    Looking first at  FIGS. 1 and 5 , there is shown a humeral component  20  of a prosthetic elbow replacement according to the invention. The humeral component  20  may be formed from: (i) a metal or metal alloy such as a titanium alloy (e.g., titanium-6-aluminum-4-vanadium), a cobalt alloy, a stainless steel alloy, or tantalum; (ii) a nonresorbable ceramic such as aluminum oxide or zirconia; (iii) a nonresorbable polymeric material such as polyethylene; or (iv) a nonresorbable composite material such as a carbon fiber-reinforced polymers (e.g., polysulfone). Preferably, the humeral component  20  is formed from a metal alloy, and most preferably, the humeral component  20  is formed from a cobalt chrome alloy. 
         [0042]    The humeral component  20  has an elongated stem portion  22  with a porous surface section  23  into which bone tissue can grow and/or bone cement can infiltrate. The humeral component  20  also has a J-shaped flange  24  with a porous surface section  25  into which bone tissue can grow and/or bone cement can infiltrate. The flange  24  includes a curved end  24   a  integral with the humeral stem portion  22  and an elongated stem  24   b  spaced from and substantially parallel with the humeral stem portion  22 . Various stem and flange dimensions are possible, including without limitation, 4″ small, 6″ small, 8″ small, 4″ regular, 6″ regular, 8″ regular, 4″ x-small, 6″ x-small, 6″ small with long flange, 8″ small with long flange, 6″ regular with long flange, and 8″ regular with long flange. 
         [0043]    The porous surface sections  23 ,  25  of the humeral component  20  can be formed using various techniques such as plasma spraying of a metal powder, sintering of metal beads, or diffusion bonding of metal wire mesh. In one form, the porous surface sections  23 ,  25  comprise a porous material, and preferably comprise a porous metallic material having a network of interconnected pores distributed throughout the metallic material chosen to ensure that the resulting interstitial pore size is at least sufficient to permit bone tissue to grow into the porous material. Preferably, the metallic particles are formed from titanium, titanium alloys, cobalt alloys, stainless steel alloys, tantalum, and mixtures thereof, and most preferably, the metallic particles are formed from tantalum. Various methods are known for forming the porous material on the stem  22  and flange  24 , such as the methods described in U.S. Pat. Nos. 5,734,959, 4,206,516 and 3,855,638 and U.S. Patent Application Publication No. 2003/0232124, which are incorporated herein by reference along with all other documents cited herein. The porous surface sections  23 ,  25  may also include a textured surface comprising a plurality of depressions such as grooves, dimples, or the like. Further, the porous surface sections  23 ,  25  may also have a coating of a bone ingrowth promoting material such as hydroxyapatite (Ca 10 (PO 4 ) 6 OH 2 ), a calcium phosphate (e.g., tricalcium phosphate (Ca 3 (PO 4 ) 2 )), growth factors, bone morphogenic proteins, and mixtures thereof. 
         [0044]    The humeral component  20  also has a yoke section  26  with a curved concave inner surface  27  (see  FIG. 5 ). One side of the yoke section  26  has an arm  29  that terminates in a circular section  30  having a central hole  31 . The circular section  30  has an annular end section recess  32  of increased inside diameter in relation to the central hole  31  that allows for rotation of a section of a pivot pin as described below. Another side of the yoke section  26  has an arm  34  that terminates in a circular section  35  having a central hole  36 . The circular section  35  has an annular end section recess  37  of increased inside diameter in relation to the central hole  36  (identical to end section recess  32 , see  FIG. 7 ) that allows for rotation of a section of a pivot pin as described below. 
         [0045]    Looking now at  FIGS. 2 and 3 , there is shown a stem  42  of an ulnar component  40  of a prosthetic elbow replacement according to the invention. The stem  42  of the ulnar component  40  may be formed from: (i) a metal or metal alloy such as a titanium alloy (e.g., titanium-6-aluminum-4-vanadium), a cobalt alloy, a stainless steel alloy, or tantalum; (ii) a nonresorbable ceramic such as aluminum oxide or zirconia; (iii) a nonresorbable polymeric material such as polyethylene; or (iv) a nonresorbable composite material such as a carbon fiber-reinforced polymers (e.g., polysulfone). Preferably, the stem  42  of the ulnar component  40  is formed from a metal alloy, and most preferably, the stem  42  is formed from a cobalt chrome alloy. 
         [0046]    The stem  42  of the ulnar component  40  has a distal end  43  that is inserted in the medullary canal of the ulna. The stem  42  of the ulnar component  40  has a porous surface section  45  into which bone tissue can grow and/or bone cement can infiltrate. Various stem dimensions are suitable for the stem  42  of the ulnar component  40  including without limitation, small left, small right, regular left, regular right, long small left, long small right, long regular left, long regular right, x-long x-small left, x-long x-small right. 
         [0047]    The porous surface section  45  of the stem  42  of the ulnar component  40  can be formed using various techniques such as plasma spraying of a metal powder, sintering of metal beads, or diffusion bonding of metal wire mesh. In one form, the porous surface section  45  comprises a porous material, and preferably comprises a porous metallic material having a network of interconnected pores distributed throughout the metallic material chosen to ensure that the resulting interstitial pore size is at least sufficient to permit bone tissue to grow into the porous material. Preferably, the metallic particles are formed from titanium, titanium alloys, cobalt alloys, stainless steel alloys, tantalum, and mixtures thereof, and most preferably, the metallic particles are formed from tantalum. The porous surface section  45  may also include a textured surface comprising a plurality of depressions such as grooves, dimples, or the like. Further, the porous surface section  45  may also have a coating of a bone ingrowth promoting material such as hydroxyapatite (Ca 10 (PO 4 ) 6 OH 2 ), a calcium phosphate (e.g., tricalcium phosphate (Ca 3 (PO 4 ) 2 )), growth factors, bone morphogenic proteins, and mixtures thereof. 
         [0048]    On the side of the porous surface section  45  opposite the distal end  43  of the stem  42 , the outer surface of the stem  42  of the ulnar component  40  has an outwardly curved section  46  that merges with an inwardly curved section  47  that terminates in a proximal end surface  48  of the stem  42  of the ulnar component  40 . An internally threaded inwardly directed axial hole  49  is centrally located in the end surface  48  of the stem  42  of the ulnar component  40 . 
         [0049]    The ulnar component  40  also includes a mounting cap  52  having a dome shaped top surface  53  and a side wall  54  that tapers inwardly from the top surface  53 . The side wall  54  terminates in an end surface  55  of the cap  52  of the ulnar component  40 . An internally threaded throughhole  56  extends from the top surface  53  to the end surface  55  of the cap  52 . The ulnar component  40  also includes a screw  58  that engages the threads of the throughhole  56  of the cap  52  and engages the threads of the axial hole  49  of the stem  42  when the cap  52  is assembled to the stem  42  as shown in  FIG. 3 . thereby creating an interface  59  between the end surface  55  of the cap  52  and the end surface  48  of the stem  42 . 
         [0050]    Looking at  FIGS. 1 to 7 , there is shown a pivot pin  60  of a prosthetic elbow replacement according to the invention. The pivot pin  60  may be formed from: (i) a metal or metal alloy such as a titanium alloy (e.g., titanium-6-aluminum-4-vanadium), a cobalt alloy, a stainless steel alloy, or tantalum; (ii) a nonresorbable ceramic such as aluminum oxide or zirconia; (iii) a nonresorbable polymeric material such as polyethylene; or (iv) a nonresorbable composite material such as a carbon fiber-reinforced polymers (e.g., polysulfone). Preferably, the pivot pin  60  is formed from a metal alloy, and most preferably, the pivot pin  60  is formed from a cobalt chrome alloy. 
         [0051]    As shown in  FIGS. 1 and 7 , the pivot pin  60  includes a main body  61  having a cylindrical central section  62  and having a disk shaped end section  67  that defines an end flange  63 . The cylindrical central section  62  has a transverse throughhole  64  with an inner surface  65  having a generally hourglass shape (see  FIG. 7 ). In one example form, the inner surface  65  of the throughhole  64  has an inside diameter that continuously decreases from the outer surface  66  of the cylindrical central section  62  to the central axis of rotation A of the cylindrical central section  62  of the pivot pin  60  (see  FIG. 7 ). The cylindrical central section  62  also has an internally threaded inwardly directed axial hole  69  centrally located in the end of the cylindrical central section  62  opposite the end section  67 . 
         [0052]    The pivot pin  60  also includes a removable disk  72  having a central throughhole  73 . The pivot pin  60  further includes a pin fastener, screw  76 , that engages the inner surface of the throughhole  73  of the disk  72  and engages the threads of the axial hole  69  of the cylindrical central section  62  of the pivot pin  60  when the disk  72  is assembled to the cylindrical central section  62  as shown in  FIG. 7 . When the pivot pin  60  is assembled to the humeral component  20  as shown in  FIG. 7 , the disk  72  can rotate in the end section recess  37  of the circular section  35  of the humeral component  20  and the end flange  63  can rotate in the end section recess  32  of the circular section  30  of the humeral component  20 . The cylindrical central section  62  of the pivot pin  60  rotates in the other sections of the central holes  31 ,  36 . It should be appreciated that other means for installing the pivot pin on the humeral component  20  are contemplated and that the construction of the pivot pin  60  described herein is one example of a means for installing the pivot pin on the humeral component  20 . 
         [0053]    The surface of the disk  72 , the surface of the end section recess  37 , the surface of the end flange  63 , the surface of the end section recess  32 , the surface of the cylindrical central section  62  of the pivot pin  60 , and the surfaces of the central holes  31 ,  36  are preferably metallic such that the articulation will be metallic on metallic, thus lessening the likelihood of wear. In one form, the humeral component consists essentially of metallic material, the pivot pin consists essentially of metallic material, and the ulnar component consists essentially of metallic material such that the articulation will be metallic on metallic, thus lessening the likelihood of wear. 
         [0054]    Referring to  FIGS. 1A ,  6  and  7 , the prosthetic elbow replacement may be inserted in a patient as follows. First, the mid-portion of the trochlea is removed to facilitate access to the medullary canal of the humerus  80 . The medullary canal of the humerus is then reamed, and a cutting guide is used to provide for accurate removal of the articular surface of the distal humerus. Next, the medullary canal of the ulna  82  is located and then reamed. Cement  84  is then injected down the medullary canal of both the ulna and humerus. Of course, the surgeon may decide to rely on a “press-fit” (sometimes called an “interference fit”) for implantation of the humeral component  20  in the humerus  80  and the ulnar component  40  in the ulna  82  such that the bone cement  84  can be omitted. 
         [0055]    The ulnar stem  42  of the ulnar component  40  is then inserted in the medullary canal of the ulna  82 . A T-shaped instrument having an elongated shaft with an externally threaded distal end (such as that described in U.S. Pat. No. 5,061,271) can be useful for inserting the ulnar stem  42  in the medullary canal of the ulna  82 . For instance, the externally threaded distal end of the instrument can be threaded into the internally threaded axial hole  49  of the ulnar stem  42  for positioning the ulnar stem  42  in the medullary canal of the ulna  82 . After positioning the ulnar stem  42  in the medullary canal of the ulna  82 , the externally threaded distal end of the T-shaped instrument can be removed from the internally threaded axial hole  49  of the ulnar stem  42 . The T-shaped instrument can insert the ulnar stem  42  to the proper depth and rotation. Extraction of the ulnar stem  42  from the medullary canal of the ulna  82  can also be accomplished using the T-shaped instrument. An alternative for extraction is a vise-grip that grabs the dimples of the proximal ulna as it is exposed in the area of the olecranon articulation. 
         [0056]    Next, a bone graft  87  is prepared. The stem  22  of the humeral component  20  is inserted down the medullary canal of the humerus  80  and the bone graft  87  is positioned to be captured by the flange  24  of the humeral component  20  as shown in  FIG. 1A . A humeral impactor can be used to insert the humerus to its optimum position prior to the articulation with the ulna. 
         [0057]    The assembly of the rotating pivot pin  60  to the humeral component  20  can be done at the time of implantation on the back table. The pivot pin  60  is also able to be disassembled for the purpose of applying a resurfacing implant and then can in turn be easily converted to the linked implant. 
         [0058]    After the humeral component  20  and the ulnar component  40  are inserted in the humerus and ulna, the inwardly curved section  47  of the ulnar stem  42  of the ulnar component  40  is inserted into one end of the throughhole  64  of the cylindrical central section  62  of the pivot pin  60 . The T-shaped instrument shaft can be inserted through the throughhole  64  of the cylindrical central section  62  of the pivot pin  60  and used to capture the stem  42  of the ulnar component  40  and pull the stem  42  into the throughhole  64  of the cylindrical central section  62  of the pivot pin  60 . The outer side wall  54  of the cap  52  of the ulnar component  40  is then inserted into the opposite end of the throughhole  64  of the cylindrical central section  62  of the pivot pin  60 . The screw  58  is then screwed into the throughhole  56  of the cap  52  so that the screw  58  engages the threads of the throughhole  56  of the cap  52  and engages the threads of the axial hole  49  of the stem  42  such that the cap  52  is assembled to the stem  42  as shown in  FIGS. 3 and 7 . 
         [0059]    When the prosthetic elbow replacement is inserted in a patient, flexion occurs by rotation of the disk  72  of the pivot pin  60  in the end section recess  37  of the central hole  36  of the circular section  35  of the humeral component  20  and by rotation of the end flange  63  of the pivot pin in the end section recess  32  of the central hole  31  of the circular section  30  of the humeral component  20  and by rotation of the cylindrical central section  62  of the pivot pin  60  in the other sections of the central holes  31 ,  36 . Of course, different means for installing the pivot pin in the humeral component  20  will provide for different means for rotation of the pivot pin with respect to the humeral component  20 . 
         [0060]    Varus/valgus motion is provided by movement of the inwardly curved section  47  of the end surface  48  of the stem  42  of the ulnar component  40  and by movement of the outer side wall  54  of the cap  52  of the ulnar component  40  within the hourglass-shaped inner surface  65  of the throughhole  64  of the pivot pin  60 . The curved inner surface  27  of the yoke section  26  also provides space for varus valgus movement of the cap  52  of the ulnar component  40 . 
         [0061]    Although the present invention has been described in detail with reference to certain embodiments, one skilled in the art will appreciate that the present invention can be practiced by other than the described embodiments, which have been presented for purposes of illustration and not of limitation. Therefore, the scope of the appended claims should not be limited to the description of the embodiments contained herein. 
       INDUSTRIAL APPLICABILITY 
       [0062]    The invention provides a prosthetic elbow replacement for a dysfunctional elbow joint.