A fixation system adapted for securing bone members (4, 5) together, said fixation system comprising: a fastener adapted for being secured to a first bone member, a plate comprising a spherical hole, and a bearing for securing the fastener in an adjusted angular position in the hole in the plate which plate is adapted for being secured to a second bone member and thereby secure the bone members (4,5) together, said bearing having an outer surface adapted to rotate in the hole in said plate, said bearing having a bore in which the fastener is inserted and can be angularly adjusted by rotation of the bearing in the hole in the plate, wherein said hole narrows in diameter from a widest diameter in a plane running through an equatorial region of the hole to narrower diameters in respective planes along the top and bottom surfaces of the plate, and said bearing is provided with a first end portion having a spherical surface, a second end portion having a spherical surface, and slot means therein to enable radial expansion of the bearing when the fastener is advanced in the bore in the bearing, wherein the slot means is constructed and arranged in the bearing to secure the bearing in the plate, and wherein said slot means comprises a plurality of slots extending from the first end portion of the bearing partially along the length of the bearing to a position more than halfway along the length of the bearing, characterized in that; the slots define lever-like petals around said bearing, the fastener comprising a portion with a diameter that is greater than a diameter of a part of the bore comprising the lever-like petals such that advancement of the bone fastener to said part in said bore causes tips of the lever-like petals to move outwardly to cause the spherical surface at the first end portion of the bearing to bear against a spherical surface of the hole on a first side of the equatorial region while the spherical surface at the second end portion of the bearing bears against a spherical surface of the hole on an opposite side of the equatorial region to develop a non-uniform distribution of forces between the bearing and the plate which resists torque applied to the fastener by migration of bone fragments when the fracture system is securing the bone members (4, 5) together. a fastener adapted for being secured to a first bone member, a plate comprising a spherical hole, and a bearing for securing the fastener in an adjusted angular position in the hole in the plate which plate is adapted for being secured to a second bone member and thereby secure the bone members (4,5) together, said bearing having an outer surface adapted to rotate in the hole in said plate, said bearing having a bore in which the fastener is inserted and can be angularly adjusted by rotation of the bearing in the hole in the plate, wherein said hole narrows in diameter from a widest diameter in a plane running through an equatorial region of the hole to narrower diameters in respective planes along the top and bottom surfaces of the plate, and said bearing is provided with a first end portion having a spherical surface, a second end portion having a spherical surface, and slot means therein to enable radial expansion of the bearing when the fastener is advanced in the bore in the bearing, wherein the slot means is constructed and arranged in the bearing to secure the bearing in the plate, and wherein said slot means comprises a plurality of slots extending from the first end portion of the bearing partially along the length of the bearing to a position more than halfway along the length of the bearing, characterized in that; the slots define lever-like petals around said bearing, the fastener comprising a portion with a diameter that is greater than a diameter of a part of the bore comprising the lever-like petals such that advancement of the bone fastener to said part in said bore causes tips of the lever-like petals to move outwardly to cause the spherical surface at the first end portion of the bearing to bear against a spherical surface of the hole on a first side of the equatorial region while the spherical surface at the second end portion of the bearing bears against a spherical surface of the hole on an opposite side of the equatorial region to develop a non-uniform distribution of forces between the bearing and the plate which resists torque applied to the fastener by migration of bone fragments when the fracture system is securing the bone members (4, 5) together.