The paper describes the design and laboratory testing of a new metacarpophalangeal prosthesis. The novel features of the new design include the joining of pairs of prostheses by common hinge-pins and the inclusion of bearings within the proximal phalanges. The common hinge-pins are designed to prevent the recurrence of ulnar drift by sharing the forces on one finger with a neighbouring joint, and together with the intramedullary bearings to prevent potentially loosening torques from acting on the fixation of the components.