Abstract: In a screw device (10; 80) for fixing prostheses to bones, the threaded shank (14) comprises a core (32, 34) of overall frustoconical shape. The screw has a cylindrical neck (12) of diameter equal to or greater than the maximum diameter of the thread. This latter is of two different types, namely a first thread (26) of large pitch for fixing into the trabecular bone tissue (52) and a second thread (28), which can be of the self-tapping type, for fixing into tile cortical bone opposite the point at which the screw is inserted into the bone. The second thread (28) has a number of starts which is a multiple of that of the first thread (26). For orthopedic use the screw (80) can comprise a third thread (128) on a part of the neck (112) for fixing into the relative cortical bone (50). A method for applying the screw device (10; 80) consists of forming a precision hole (40) in the bone, tapping said hole with a tapper (60; 100), and screwing the screw (10; 80) into it.

Abstract: In a screw device (10; 80) for fixing prostheses to bones, the threaded shank (14) comprises a core (32, 34) of overall frusto-conical shape. The screw has a cylindrical neck (12) of diameter equal to or greater than the maximum diameter of the thread. This latter is of two different types, namely a first thread (26) of large pitch for fixing into the trabecular bone tissue (52) and a second thread (28), which can be of the self-tapping type, for fixing into the cortical bone opposite the point at which the screw is inserted into the bone. The second thread (28) has a number of starts which is a multiple of that of the first thread (26). For orthopedic use the screw (80) can comprise a third thread (128) on a part of the neck (112) for fixing into the relative cortical bone (50). A method for applying the screw device (10; 80) consists of forming a precision hole (40) in the bone, tapping said hole with a tapper (60; 100), and screwing the screw (10; 80) into it.