A bone screw (1) having a threaded proximal portion (2), a threaded median portion (3), and a threaded distal portion (4). Threaded proximal portion (2) has a core (11) with a constant diameter and a proximal thread (12) with a constant diameter and a proximal pitch (P2). The threaded median portion (3) has a core (15), which is conical, with a diameter becoming increasingly larger from the distal end of the threaded median portion (3) to the proximal end thereof, and thread (16), which has a constant diameter smaller than the diameter of the thread (12) of the proximal threaded portion (2). The pitch of thread (16) of the threaded median portion (3) becomes increasingly smaller from the distal end of the threaded median portion (3) towards its proximal end. At the proximal end of the threaded median portion (3), the pitch of thread (16) is larger than the pitch (P2) of the thread (12) of the threaded proximal portion (2). The threaded distal portion (4) has a core (17) and thread (18), both having a constant diameter, and with thread (18) having a diameter that is smaller than the diameter of the thread (16). The pitch (P4) of the thread (18) of the threaded distal portion (4) is larger than the pitch of thread (16) at the distal end of the threaded median portion (3).