Abstract: A multiaxial pedicle screw for vertebral osteosynthesis, including: a pedicle screw comprising a spherical head having a recess for the rotation of said pedicle screw; a socket that is hinged onto the spherical head of the pedicle screw and is provided with two diametrically opposed side grooves for receiving a connection rod; a tightening means for maintaining the position of the connection rod that is engaged into said socket; and a locking means that is positioned between said spherical head of the pedicle screw and the socket. The locking means is formed of a ring, at least the base or distal portion of which consists of a cold-compactible material having a resilient deformation capacity. Said locking means enables the locking of the socket in a desirable direction relative to the spherical head of the pedicle screw according to the position of the pedicle screw after the anchoring thereof.