A femoral head arthroplasty system can comprise a femoral prosthesis comprising a mounting plate having a first side and an opposed second side. An adapter can extend from the second side of the mounting plate. An implant body can extend from the first side of the mounting plate. The implant body can extend from the mounting plate by a distance no greater than 90 mm. The femoral head arthroplasty system can further comprise a femoral head replacement having a generally spherical surface and comprising a recess that is shaped to complementarily receive the adapter of the femoral prosthesis.

An implant that couples a first bone and a second bone includes a body that defines a first joint surface, a second joint surface, and a median plane. The first joint surface includes a first central region that articulates with the first bone. The second joint surface includes a second central region that articulates with the second bone, and the second central region is disposed on an opposite side of the median plane of the body relative to the first central region. The first and second central regions correspond to profiles of first and second axial segments, respectively, the first and second axial segments are each one of a cylinder, a cone, and a torus and are centered on first and second axes, respectively, and the first and second axes, as projected on the median plane, are substantially perpendicular to each other. The first joint surface further defines a first peripheral region adjacent the first central region and the first axial segment has a first cross section that has a smaller curvature in the first central region of the first joint surface than in the first peripheral region of the first joint surface.