An arthroplasty device for attachment to adjacent first and second bones includes a first member with a base for securing to an extramedullary portion of the first bone and a pin that extends along an axis from the base. A second member has a base for securing to an extramedullary portion of the second bone and a sleeve that extends along an axis from the base and receives the pin of the first member. The pin and sleeve are rotatable relative to one another about the axes when the first and second members are secured to the first and second bones.
