Described is a diaphyseal prosthesis designed to be combined with a locked intramedullary nail that is currently available on the market, with the purpose of reconstructing an en bloc resection of a joint or diaphysis in a long bone, which includes a cylindrical-shaped segment of variable length formed by 3 segments, 2 female segments and 1 male segment to which the female segments are attached by threads having different directions each, one left and one right the female segments have serrated the outer edge portions so as to be introduced in an intracortical manner, the central portion thereof being tunneled so as to receive the locked centromedular nail the male segment has 3 nuts, wherein 1 of them is fixed and 2 mobile, which purpose is to avoid a subsequent un-tightening, thereby being tightened against the female segments and symmetrically modifying the length of the prosthesis (fixed nut), each component having symbols for being assembled and producing the desired effect, sh ortening or lengthening. The female components have a different color as well as the end portions of the male segment, which are coincident when assembled. The green female component is coincident with the green end portion of the male segment. The purpose of the present invention is to change the traditional fixing method and improve the reconstruction ability, sometimes avoiding scarifying an undamaged joint, because of technical limitations, or even an amputation. The invention has a file with a cutter for performing the medullar milling and carving the bone where the crowns are to be housed.Se trata de una prótesis diafisiaria diseñada para combinarse con un clavo centromedular bloqueado, ya existente en el mercado con el propósito de reconstruir una resección en bloque de una articulación o diáfisis de un hueso largo consta de un segmento cilíndrico de longitud variable formado por 3 segmentos, 2 hembras y 1 macho, al cual se unen mediante rosca con diferente sentido, una es izquier
