The present invention relates to prostheses for restoring an articulation between first and second O1, O2 bone, as well as an ancillary device for assembling the prosthesis. The prosthesis according to the invention is characterized in that it comprises a first plate 11； a second plate 21； means 30 for mounting the two plates 11, 21 in rotation about an axis 31 constituted by a flexible hinge 40 having a flat cylindrical flexible lamella 41, two cylindrical bulges 42, 43 respectively associated with two edges of the lamella 41, the dimension of the cross section of the two bulges 42, 43, taken in a direction perpendicular to the plane containing the axis of rotation 31 and passing through the two bulges, being greater than the thickness of the blade 41 taken in the same direction, a breakthrough 44, 45 made in each of the two plates 11, 21, having a shape complementary to the two bulges 42, 43 and opening on a first face of the plate； a groove 46, 47 made in each of the two plates 11, 21 and opening into the breakthrough made in this plate, on a second of its faces and on the first face, the flexible hinge 40 and the two plates 11, 21 being mounted in cooperation so that the two bulges 42, 43 and the flexible blade 41 are located respectively in the two openings 44, 45 and in the two grooves 46, 47. Application to the embodiment, in particular, metacarpophalangeal and inter phalangeal joint prostheses proximal.La présente invention concerne les prothèses pour la restauration d'une articulation entre des premier et second os O1, O2, ainsi qu'un ancillaire pour l'assemblage de la prothèse.La prothèse selon l'invention est caractérisée par le fait qu'elle comporte une première platine 11 ； une seconde platine 21 ； des moyens 30 pour monter les deux platines 11, 21 en rotation autour d'un axe 31 constitués par une charnière flexible 40 comportant une lamelle flexible plane 41 cylindrique, deux renflements 42, 43 cylindrique associés respectivement à deux bords de la lam
