Cervical plate system

A system for securing to a bone a plate having apertures with concave edges, comprising:

• a screw including a head portion and a threaded shank with a distal tip, the head portion having a central opening exposed at the proximal end of the screw and an annular wall with inner and outer surfaces and having a plurality of slots that define a plurality of spaced petals disposed around the central opening, wherein the inner surface of the annular wall includes a plurality of uniformly-spaced recesses, the screw further including an internal bore of defined shape originating in the central opening for engagement to effectuate driving of the screw into the bone;
• a locking disc rotatably disposed within the central opening, the disc including a periphery of non-circular configuration defining a plurality of uniformly-spaced protrusions that can be selectively aligned with recesses in the inner surface of the annular wall of the head, a central aperture that surrounds the internal bore of the screw so as to permit access to the internal bore, and at least a pair of proximally opening notches configured for engagement to effectuate rotation of the disc from a first rotational position to a second rotational position;
• and
• a tool with a handle, a shaft extending from the handle and having a distal end configured to mate with the internal bore of the screw to permit selective rotation of the screw, and a sleeve member axially slideable along and rotatable about the shaft and having a distal end with structure that mates with the pair of proximally opening notches in the locking disc to permit selective rotation of the disc;
• whereupon, when the locking disc is in the first rotational position within the central opening the inner surface of the annular wall is spaced from the protrusions so that at least one of the petals may flex inwardly, and when the locking disc is rotated to the second rotational position within the central opening the inner surface of the annular wall is contacted by the protrusions so that the petals are substantially prevented by the protrusions from flexing inwardly and the head is captured by the concave edges of a plate aperture.

A method of securing to a bone a plate having apertures with concave edges, comprising the steps of:

• positioning a selected aperture of the plate adjacent a desired location on the bone;
• aligning a bone screw through the selected aperture and into contact with the bone at a desired angular orientation, the screw including
• a threaded shank with a distal tip,
• a head portion having a central opening exposed at the proximal end of the screw, and an annular wall with inner and outer surfaces and having a plurality of slots that define a plurality of spaced petals disposed around the central opening, wherein the inner surface of the annular wall includes a plurality of uniformly-spaced recesses,
• an internal bore of defined shape originating in the central opening for engagement by a driving tool, and
• a locking disc rotatably disposed within the central opening, the disc having a periphery of non-circular configuration defining a plurality of uniformly-spaced protrusions that can be selectively aligned with recesses in the inner surface of the annular wall, a central aperture that surrounds the internal bore to thereby permit access to the bore by the driving tool, and at least a pair of proximally opening notches configured for engagement to effectuate rotation of the disc;
• engaging the internal bore of the screw with a driving tool having a handle and a shaft with a distal end configured to mate with the internal bore, driving the distal tip of the screw against the bone and selectively rotating the screw until it penetrates the bone to a desired depth, the driving tool further including
• a sleeve member axially slideable along and rotatable about the shaft, the sleeve member including a flange for effectuating movement of the sleeve relative to the shaft, and a distal end with structure that mates with the pair of proximally opening notches in the locking disc;
• and
• manipulating the flange first to slide the sleeve into mating engagement with the pair of proximally opening notches in the locking disc and second to rotate the locking disc from a first rotational position to a second rotational position, whereupon, when the locking disc is in the first rotational position within the central opening the inner surface of the annular wall is spaced from the protrusions so that at least one of the petals may flex inwardly, and when the locking disc is rotated to the second rotational position within the central opening the inner surface of the inner wall is contacted by the protrusions so that the petals are substantially prevented by the protrusions from flexing inwardly and the head is captured by the concave edges of the selected plate aperture.

A driving tool for manipulating an anchor device and thereby securing an apertured plate to a bone, comprising:

• a handle;
• a shaft extending from the handle and having a distal end configured to mate with an internal bore in a screw component of the anchor device to permit selective rotation of the screw component into the bone;
• and
• a sleeve member axially slideable along and rotatable about the shaft, including a flange for effectuating movement of the sleeve relative to the shaft and a distal end with structure that mates with notches in a locking disc component of the anchor device to permit selective rotation of the disc component from a first rotational position to a second rotational position.