A prosthesis comprising: an acetabular cup (11) having a surface for fixation in an acetabular cavity in a pelvic bone (4) and a concave surface located opposite the surface for fixation in an acetabular cavity, the concave surface having a acetabular cup stem (9) therein and protruding outwardly with respect to it, an acetabular head part (8) fixed to the acetabular cup stem (9), the acetabular head part (8) having a surface , the concave surface of the acetabular cup (11) and the surface of the part of the acetabular head (8) are separated from each other, thereby defining a space (16) between them, a femoral implant (1) for implantation in a medullary canal of a proximal end of a femur, and a femoral cup (6； 20) fixed to a proximal end of the femoral implant (1), the femoral cup (6； 20) being sized for articulation in space (16) , so that the cup Femoral (6； 20) has a concave surface sized for articulation on the surface of the acetabular head part (8)； characterized in that the acetabular cup stem (9) is fixed to the concave surface of the acetabular cup (11), because the prosthesis is an inverted hip prosthesis, because the part of the acetabular head (8) is a sphere, and because The space (16) is adapted to confine the femoral cup (6) within the space (16), thereby reducing the risk of dislocation.Una prótesis que comprende: una copa acetabular (11) que tiene una superficie para la fijación en una cavidad acetabular en un hueso pélvico (4)y una superficie cóncava situada opuesta a la superficie para la fijación en una cavidad acetabular, teniendo lasuperficie cóncava un vástago de copa acetabular (9) en la misma y que sobresale hacia el exterior con respecto ala misma, una parte de cabeza acetabular (8) fijada al vástago de copa acetabular (9), teniendo la parte de la cabezaacetabular (8) una superficie, la superficie cóncava de la copa acetabular (11) y la superficie de la parte de la cabeza acetabular (8) estánseparadas una de otra, definiendo con ello un es
