An interpositional arthroplasty system for use in repairing ginglymus joints such as the joints of the ankle, including a tibiotalar implant (124) that provides a first major surface (130) adapted to be positioned against a tibia (120) and a second major surface (132) adapted to be positioned against a talus (108) and a polymeric ankle implant that provides a first major surface adapted to be positioned against a talus and a second major surface adapted to be positioned against a calcaneus. Such an implant can be useful for correcting various deformities of an ankle, as well as increasing articulation of a joint. Also described are biomaterials, including polymeric biomaterials having use in preparing such implants, as well as surgical kits that include implants and other tools adapted for their use.