Modular bone implant, tool, and method

1. A tibial component of a knee prosthesis, comprising:

a tibial tray having substantially planar top and bottom surfaces and an axis extending between said surfaces, at least one fin extending radially outwardly along the bottom surface and projecting axially downwardly, the tray further including an outwardly projecting boss extending from the bottom surface, the boss having an outer wall including a cylindrical portion and a tapered portion and an inner wall defining a throughbore;

a tibial keel forming an elongate body having a top end, a bottom end, an outer surface, and an axis from the top end to the bottom end generally parallel to the tray axis, at least one fin extending axially along the outer surface and projecting radially outwardly, the tray and keel fins being generally axially aligned with one another from top to bottom to project as a single fin, the tibial keel further including a first axial bore extending inwardly from said top end and forming a bore wall, the bore wall including a cylindrical portion and a tapered portion, the tibial keel being removably engageable with the tibial tray with the boss received in the first axial bore of the tibial keel, the tapered portion of the boss seating on the tapered portion of the first axial bore to define a first junction between the tibial tray and the tibial keel, and the cylindrical portion of the boss being received by the cylindrical portion of the first bore in press-fit relationship to form a second junction between the tibial tray and tibial keel,

wherein at least one of the first and second junctions includes a rotational alignment means for aligning the tibial tray and the tibial keel in a predetermined relationship for assembly, the alignment means being formed within the junction.

2. The tibial component of claim 1 wherein the tapered portions form a locking taper.

3. The tibial component of claim 1 wherein the rotational alignment means is positioned within the junction relative to the cylindrical press-fit portion so that it is sealed within the junction to prevent migration of material from the rotational alignment means outside of the junction.

4. The tibial component of claim 1 wherein the rotational alignment means comprises a pin received in a hole.

5. The tibial component of claim 4 wherein the pin is located in the first axial bore and the pin is received by a hole formed in the boss.

6. The tibial component of claim 1 wherein the tibial keel includes a second axial bore extending from the bottom end toward the top end to communicate with the first axial bore, the second axial bore forming a tapered inner wall for receiving a stem extension.

7. The tibial component of claim 6 wherein the tray includes a bore extending from the top surface downwardly through the boss in communication with the first axial bore, the tray bore receiving a bolt in engagement with one of the keel and stem extension.

8. The tibial component of claim 1 wherein one of the first and second junctions comprise a sealing junction to prevent the passage of material across the junction.

9. The tibial component of claim 1 wherein the cylindrical press-fit second junction seals a space adjacent the taper first junction to prevent the outward migration of material from the taper first junction.

10. The tibial component of claim 1 wherein the tapered portion of the boss is formed below the cylindrical portion of the boss and the tapered portion of the first axial bore is formed below the cylindrical portion of the first axial bore so that the tapered seating portion of the first junction is below the cylindrical press-fit portion of the second junction.

11. The tibial component of claim 10 wherein the cylindrical press-fit between the boss and first axial bore seals the first axial bore to prevent material from entering or leaving the portion of the first axial bore below the press-fit.

12. The tibial component of claim 1 wherein the tray and keel fins are in an axial spaced relationship so that they do not contact.