Patent ID: 8177842

Claim:
An articular cartilage implant comprising: an articular end for repair of articular cartilage defects, said articular end having a circular perimeter defined by a diameter, a convex upper face, and a concave lower face, the convex upper face having a first spherical radius and the concave lower face having a second spherical radius, wherein the first spherical radius ranges from about 25 to about 30 millimeters if the diameter is greater than about 17 millimeters, wherein the first spherical radius ranges from about 30 to about 40 millimeters if the diameter is less than about 17 millimeters; and a stem extending from the concave lower face away from the convex upper face along a vertical axis, the stem having a plurality of circular perimeters along the vertical axis, wherein the stem has a first stem portion having a maximum stem circular perimeter extending at least one millimeter from the concave lower face away from the convex upper face along the vertical axis, the maximum stem circular perimeter being less than the articular end circular perimeter, and a second stem portion extending from the first stem portion away from the convex upper face along the vertical axis, the second stem portion having a plurality of second stem portion circular perimeters decreasing in stem diameter from the maximum stem circular perimeter of the first stem portion to a lesser second stem portion circular perimeter along the vertical axis of the stem; and wherein the stem has a plurality of circumferential grooves, wherein each circumferential groove extends continuously around at least one of the plurality of second stem portion circular perimeters, wherein at least one circumferential groove is defined between two adjacent second stem portion circular perimeters and has a shape of a partial, non-planar torus extending radially inward of the adjacent second stem portion circular perimeters, wherein the at least one circumferential groove blends into at least one of the two adjacent second stem portion circular perimeters, wherein the stem blends into the concave lower face, and wherein the articular end and the stem each consist essentially of: a graphite core and a pyrocarbon coating.