A prosthesis for arthroplasty comprises members which can be used for arthrodesis. The prosthesis comprises two prosthesis members (2, 3). The prosthesis members (2, 3) comprises a first screw-like attachment member (4) and a second screw-like attachment member (5) respectively, and a socket member (6) and a head member (7) respectively. The socket member (6) has an attachment pin (16) which is insertable into a hole (8) in the first screw-like attachment member (4) and the head member (7) has an attachment pin (19) which is insertable into a hole (9) in the second screw-like attachment member (5). The hole (8) in the first screw-like attachment member (4) is partly configured to define a press fit with the attachment pin (16) of the socket member (6) and partly threaded to alternatively permit securing by screwing in said hole of a locking member for cooperation with a lockable member which is configured for adjustable setting thereof relative to the locking member and for fixation thereof, in set position, to the locking member, which lockable member is made in one piece with the second attachment member, or for cooperation with a lockable member which replaces the head member in the second screw-like member.Prothèse pour arthrodèse primaire, susceptible d'être utilisée pour une arthroplastie, et prothèse pour arthroplastie comportant des éléments pour arthrodèse. La prothèse (1b) pour arthrodèse primaire comporte un élément (33b) de blocage doté d'une partie (16b) de fixation susceptible d'être insérée dans un trou (8b) pratiqué dans un premier élément (4b) de fixation de la prothèse pour y positionner l'élément de blocage, et un élément blocable (34b) intégré à un deuxième élément (5b) de fixation de la prothèse. L'élément blocable (34b) est configuré pour être posé de façon réglable par rapport à l'élément (33b) de blocage et pour être fixé, en position posée, à l'élément de blocage. En variante, l'élément blocable comporte une partie de fixation susceptible d'
