A diaphyseal implant kit, which comprises: a diaphyseal implant component (52A, 52B, 52C, 52D, 52E) comprising: a first end (54A, 54B, 54C, 54D, 54E) having a bore (95A, 95B, 95C, 95D, 95E), a second end (56A, 56B, 56C, 56D, 56E) having a bore (94A, 94B, 94C, 94D, 94E) which is co-axial with the bore of the first end, a longitudinal axis (58A, 58B, 58C, 58D, 58E) extending from the first end to the second end, the longitudinal axis extending through the bores at the first end and second end, a collar portion (59A, 59B, 59C, 59D, 59E) between the first end and second end and surrounding at least a portion of the bore at the first end, the collar portion including an annular surface (86A, 86B, 86C, 86D, 86E) disposed perpendicular to the longitudinal axis of the implant component, and a tapered outer surface (60A, 60B, 60C, 60D, 60E) adjacent to the annular surface of the collar portion and extending toward the second end, the tapered outer surface being porous to promote bone ingrowth for non-cemented fixation, and having a maximum outer diameter nearest the annular surface of the collar and a minimum outer diameter at the second end of the implant component, in which the annular surface of the collar portion has an outer diameter greater than the maximum outer diameter of porous tapered outer surface, a stem for positioning in the intramedullary canal of a patient's long bone, having an attachment end which can be received in the bore at the second end of the diaphyseal implant component to attach the stem to the diaphyseal implant component, and an adapter having a tapered first end and a tapered second end, the tapered first end defining a Morse taper post to be received in the bore at the first end of the diaphyseal implant component. a diaphyseal implant component (52A, 52B, 52C, 52D, 52E) comprising: a first end (54A, 54B, 54C, 54D, 54E) having a bore (95A, 95B, 95C, 95D, 95E), a second end (56A, 56B, 56C, 56D, 56E) having a bore (94A, 94B, 94C, 94D, 94E) which is co-axial with the bore of the first end, a longitudinal axis (58A, 58B, 58C, 58D, 58E) extending from the first end to the second end, the longitudinal axis extending through the bores at the first end and second end, a collar portion (59A, 59B, 59C, 59D, 59E) between the first end and second end and surrounding at least a portion of the bore at the first end, the collar portion including an annular surface (86A, 86B, 86C, 86D, 86E) disposed perpendicular to the longitudinal axis of the implant component, and a tapered outer surface (60A, 60B, 60C, 60D, 60E) adjacent to the annular surface of the collar portion and extending toward the second end, the tapered outer surface being porous to promote bone ingrowth for non-cemented fixation, and having a maximum outer diameter nearest the annular surface of the collar and a minimum outer diameter at the second end of the implant component, in which the annular surface of the collar portion has an outer diameter greater than the maximum outer diameter of porous tapered outer surface, a first end (54A, 54B, 54C, 54D, 54E) having a bore (95A, 95B, 95C, 95D, 95E), a second end (56A, 56B, 56C, 56D, 56E) having a bore (94A, 94B, 94C, 94D, 94E) which is co-axial with the bore of the first end, a longitudinal axis (58A, 58B, 58C, 58D, 58E) extending from the first end to the second end, the longitudinal axis extending through the bores at the first end and second end, a collar portion (59A, 59B, 59C, 59D, 59E) between the first end and second end and surrounding at least a portion of the bore at the first end, the collar portion including an annular surface (86A, 86B, 86C, 86D, 86E) disposed perpendicular to the longitudinal axis of the implant component, and a tapered outer surface (60A, 60B, 60C, 60D, 60E) adjacent to the annular surface of the collar portion and extending toward the second end, the tapered outer surface being porous to promote bone ingrowth for non-cemented fixation, and having a maximum outer diameter nearest the annular surface of the collar and a minimum outer diameter at the second end of the implant component, in which the annular surface of the collar portion has an outer diameter greater than the maximum outer diameter of porous tapered outer surface, a stem for positioning in the intramedullary canal of a patient's long bone, having an attachment end which can be received in the bore at the second end of the diaphyseal implant component to attach the stem to the diaphyseal implant component, and an adapter having a tapered first end and a tapered second end, the tapered first end defining a Morse taper post to be received in the bore at the first end of the diaphyseal implant component.