Multiaxial modular tibia stems

An ankle prosthesis, comprising:

• a tibia stem component including a leading end, a trailing end, and a longitudinal axis defined therethrough with an elongated generally cylindrical shell defining an internal cavity therein that is open at the trailing end and includes one or more openings;
• and
• a tibia tray component configured to be attached to a prosthetic joint articulating surface,
• wherein the tibia tray component extends from the trailing end of the tibia stem component,
• wherein the tibia stem component is sized and configured to be disposed in an intramedullary canal formed in a tibia,
• wherein the tibia stem component comprises:
• one or more retractable members configured to be controllably movable from a retracted position and be extended outward and away from the longitudinal axis through the one or more openings defined in the cylindrical shell and through which the one or more retractable members move from the retracted position and extend outward,
• wherein in the retracted position, the one or more retractable members are contained substantially within the tibia stem component and do not extend outward,
• wherein when the tibia stem component is disposed in the intramedullary canal and the one or more retractable members are extended outward, the one or more retractable members engage the intramedullary canal's surrounding bone and enhance anchoring the tibia stem within the intramedullary canal and further comprises a linear actuator provided within the internal cavity, the linear actuator being configured to be movable within the internal cavity along the longitudinal axis,
• wherein each of the one or more retractable members have a distal end and a proximal end, the proximal end being attached to the linear actuator and the distal end being a free end that is movable through the opening provided in the cylindrical shell of the tibia stem component to engage the intramedullary canal's surrounding bone,
• whereby the one or more retractable members can be moved from the retracted position and extended outward and away from the tibia stem component by moving the linear actuator within the internal cavity;
• wherein the linear actuator comprises a base piece and a moving piece,
• wherein the base piece is positioned in the internal cavity and is configured to be rotated about the longitudinal axis but stationary so that it does not move in axial direction within the internal cavity, and the moving piece is movable along the longitudinal axis of the tibia stem with respect to the base piece,
• wherein the base piece and the moving piece threadedly engage each other for moving the threaded stem within the internal cavity.