Spinal fixation apparatus and methods for use

An anchor screw assembly for a spinal fixation system, comprising:

• a screw having a first threaded portion, and a second portion;
• a swing bolt pivotally coupled to the second portion of the screw, the swing bolt defining a first axis and comprising a noncircular region extending along the first axis, the noncircular region having a noncircular cross-section;
• a clamp assembly comprising first and second clamp portions, each clamp portion having a noncircular first passage therethrough for receiving the noncircular region of the swing bolt therethrough, the first and second clamp portions having cooperating grooves therein, the cooperating grooves together defining a second passage extending substantially transversely to the first axis when the first and second clamp portions are received on the swing bolt;
• and
• a fastener for securing the clamp assembly on the swing bolt.

A spinal fixation system, comprising:

• a first anchor screw assembly comprising a first screw having a threaded portion, a swing bolt pivotally coupled to the screw and comprising a noncircular region extending along a first longitudinal axis of the swing bolt, a first clamp assembly comprising a first passage for receiving the first swing bolt therethrough, the noncircular region and the first passage having similar cross-sections, and a fastener for securing the first clamp assembly on the swing bolt, the first clamp assembly comprising a second passage therethrough along a second axis substantially transverse to the first axis;
• a second anchor screw assembly comprising a second screw having a threaded portion and a hub, a second clamp assembly receivable on the hub, and defining a third passage therethrough along a third axis substantially transverse to the first axis;
• and
• an elongate member receivable through the second and third passages.

An anchor screw assembly for a spinal fixation system, comprising:

• an anchor screw having a first threaded portion, and a second head portion defining a longitudinal axis, the head portion comprising a noncircular region extending along the longitudinal axis, the noncircular region having a noncircular cross-section, the threaded portion comprising a pull-out portion adjacent the head portion;
• a clamp assembly comprising upper and lower clamp portions, each clamp portion having a noncircular first passage therethrough for receiving the noncircular region of the head portion therethrough to prevent substantial rotation of the clamp assembly with respect to the head portion about the longitudinal axis, the first and second clamp portions having cooperating grooves therein, the cooperating grooves together defining a second passage extending along a second axis substantially transversely to the first axis when the first and second clamp portions are received on the swing bolt, the upper clamp portion comprising a lower surface including one of the cooperating grooves therein, and an upper surface including a raised shoulder above the one of the cooperating groove and a recessed area adjacent the raised shoulder and above the first passage;
• and
• a nut for securing the clamp assembly on the head portion, the nut being received in the recessed area, thereby minimizing a height profile of the anchor screw assembly.

A method for stabilizing vertebrae relative to one another using a plurality of swing bolt anchor screws, each swing bolt anchor screw comprising a swing bolt pivotally coupled to a threaded portion, the vertebrae being disposed adjacent one another along a central spinal axis, the method comprising:

• screwing a threaded portion of a first swing bolt anchor screw into a first vertebra until a first pivot axis of the first swing bolt anchor screw has a predetermined orientation with respect to the spinal axis;
• screwing a threaded portion of a second swing bolt anchor screw into a second vertebra adjacent the first vertebra until a second pivot axis of the second swing bolt anchor screw is substantially transverse to the first pivot axis;
• adjusting an angle of one or more swing bolts on the first and second swing bolt anchor screws about the first and second pivot axes;
• placing lower clamp portions on the swing bolts of the first and second swing bolt anchor screws;
• placing a rod on the lower clamp portions, the rod extending at least between the first and second anchor screws;
• and
• securing upper clamp portions on the swing bolts of the first and second swing bolt anchor screws, thereby securing the rod between the upper and lower clamp portions.