PARTIALLY POROUS BONE IMPLANT KEEL
A method for removing a stem portion of an orthopedic implant from a bone comprises exposing an implanted orthopedic implant having a body portion, a stem portion interconnected to the body and a porous metal section forming an interconnection between the body and the stem portion. A cutting tool is mounted on a holder connected to an exposed surface of the orthopedic implant. The porous section is aligned with the cutting tool mounted on the holder. The entire porous section is cut by moving the cutting tool therethrough in a direction transverse to the stem portion axis. The implant body portion is then removed and then the stem portion is removed from the bone. The cutting tool may be a saw or chisel which may be mounted on a guide fixed to the body portion.
1 . A tibial implant comprising:
a metal baseplate having a bone contacting surface;
an at least partially porous metal spacer section fused to the bone contacting surface of the baseplate;
a fully dense stem portion having an attachment area fused to the at least partially porous metal spacer section of the baseplate, the fully dense stem portion is spaced at least 2 mm from the baseplate bone contacting surface by the at least partially porous metal spacer section.
2 . The tibial implant as set forth in claim 1 wherein the at least partially porous metal spacer area and the fully dense stem portion are in the form of a v-shaped keel.
3 . The tibial implant as set forth in claim 2 wherein the v-shaped porous metal spacer area comprises a plurality of solid struts extending through the at least partially porous area into the fully dense stem portion.
4 . The tibial implant as set forth in claim 1 wherein the porous metal spacer section has a pore size of 100 to 400 μm.
5 . The tibial implant as set forth in claim 1 wherein the porous metal spacer section has pores formed by open polyhedron structures.
6 . The tibial implant as set forth in claim 5 wherein the polyhedron is an octahedron.
7 . The tibial implant as set forth in claim 1 wherein the fully dense stem portion surrounds a porous core.
8 . The tibial implant as set forth in claim 1 wherein the metal is selected from the group consisting of Titanium, Titanium alloy or cobalt chrome molybdenum alloy.
9 . A tibial implant comprising:
a fully dense metal baseplate having a bone contacting surface;
an at least partially porous metal spacer section fused to the bone contacting surface of the baseplate;
a fully dense central stem portion having an attachment area fused to the at least partially porous metal spacer section of the baseplate, the fully dense stem portion is spaced at least 2 mm from the baseplate bone contacting surface by the at least partially porous metal spacer section, the at least partially porous metal spacer section and the fully dense stem portion are in the form of a v-shaped keel having the central stem portion and outwardly extending wings, the wings and central stem separated from the baseplate by the partially porous metal spacer.
10 . The tibial implant as set forth in claim 9 wherein the v-shaped porous metal spacer area comprises a plurality of solid struts extending through the at least partially porous area into the fully dense stem portion.
11 . The tibial implant as set forth in claim 9 wherein the porous metal spacer section has a pore size of 100 to 400 μm.
12 . The tibial implant as set forth in claim 9 wherein the porous metal spacer section has pores formed by open polyhedron structures.
13 . The tibial implant as set forth in claim 12 wherein the polyhedron is an octahedron.
14 . The tibial implant as set forth in claim 9 wherein the fully dense stem portion surrounds a porous core.
15 . The tibial implant as set forth in claim 9 wherein the metal is selected from the group consisting of Titanium, Titanium alloy or cobalt chrome molybdenum alloy.