Endosteal screw (1) for fixing a plate (102) to a bone site (300), comprising a pin (2) at least partially threaded, insertion means for inserting the screw into a bone site (300) and a part ( 33) distal intended to be coupled to said plate (102) to secure it to said bone site (300) and comprising a head (3) having faces (30) defining an external peripheral profile intended for coupling with a key (101) ) of tubular manipulation nuts, to allow the screw (1) to be removed from the bone site (300) in which it has been inserted, in which the faces (30) are curvilinear and the external peripheral profile defined by the same faces (30 ) has a convex cylindrical body shape, in order to allow a stable coupling between the wrench (101) of tubular handling nuts and said profile, which is maintained during the loosening phase of the plate screw, even when said wrench (101) of manipulation nuts Tubular ion is oriented in an inclined direction with respect to the longitudinal axis (x) of the endoosseous screw (1), the faces (30) being even in number characterized in that the faces define a regular polygonal section along a middle section (AA ) of the head (3), said middle section (AA) being a middle cross section located in a plane perpendicular to the longitudinal axis of the screw and dividing each face (30) into two internal and external parts (30a, 30b), respectively , which are arranged specularly with each otherTornillo (1) endoóseo para fijar una placa (102) a un sitio (300) óseo, que comprende una espiga (2) al menos parcialmente roscada, medios de inserción para insertar el tornillo en un sitio (300) óseo y una parte (33) distal prevista para acoplarse a dicha placa (102) para sujetarla a dicho sitio (300) óseo y que comprende una cabeza (3) que tiene caras (30) que definen un perfil periférico externo previsto para su acoplamiento con una llave (101) de tuercas de manipulación tubular, para permitir extraer el tornillo (1) del sitio (300) óseo en el que se ha insertad
