Abstract: A system for long bone arthroplasty includes humeral head prosthesis components, and an array of humeral head prosthesis components, each humeral head prosthesis component in the array having a convex articulation surface that is hemi-elliptical and defined by a major axis, a minor axis, an apex, and a base having an elliptical cross sectional shape defined by a major diameter along the major axis and a minor diameter along the minor axis. Each humeral head prosthesis component in the array is characterized by a ratio relationship of the minor diameter divided by the major diameter of the base, each having a major diameter and a minor diameter that is different from each of the other prosthesis components in the array, wherein as the major diameter is increased the ratio of the minor diameter to the major diameter is decreased.