Patent ID: 7410496

Claim:
An implantable orthopedic device comprising: a) a supporting structure comprising: 1) an upper face; 2) a lower face; and 3) at least one housing defined in the supporting structure, each said housing being partially defined by an upper spherical ring and partially closed by a lower holding element, each said upper spherical ring, housing, and lower holding element defining an orifice centered about an axis; b) at least one nut, made in one piece, comprising a female thread and a spherical contact surface, each said nut being shaped so as to be held within a respective one of the housings, between said upper spherical ring and said lower holding element; c) at least one fastening screw, each comprising: 1) a threaded body sized so that the threaded body can pass through the orifice, the threaded body comprising a body thread proportioned to be able to cooperate with bone material; and 2) a head sized to prevent the head from passing through the orifice, the head comprising: A) a collar having a peripheral contour in the form of a spherical contact surface; and B) head thread that is sized to engage the female thread of the nut, an outer diameter of the head thread being greater than or equal to an outer diameter of the body thread, the head thread being disposed between the collar and the body thread; and d) at least one relief and an adapted notch, one of which is disposed on the housing, another of which is disposed on the nut, the nut being, in the absence of engagement of the fastening screw, free to move within a predetermined tilting range to allow an axis of the female thread to be tilted with the respect to the axis of the upper spherical ring; wherein each said upper spherical ring comprises upper and lower spherical contact surfaces, having a same center, the upper and lower spherical contact surfaces being arranged to cooperate with said spherical contact surfaces of said screw head and said nut, respectively; and wherein each said spherical ring, nut, and fastening screw are designed so that each said fastening screw can be passed through a respective one of the orifices and threaded through a corresponding said nut so as to clamp the spherical ring between the nut and the screw head at a selected angle within the tilting range and while keeping contact between said corresponding spherical contact surfaces; and wherein the notch and relief are positioned and sized so that, even when the fastening screw is not engaged with the nut, the nut is locked in the housing to prevent rotation about an axis of the female thread.