Variable angle spinal screw assembly

A variable angle spinal screw and rod assembly comprising:

• a) a body member having an internal region defined by an interior surface and a lower opening that opens onto the body member interior surface;
• the opening having a first keyed surface;
• b) a screw having a lower threaded shaft adapted to implant in a bone and an upper portion;
• the screw upper portion having a second keyed surface;
• the first and second keyed surfaces having an aligned configuration and a non aligned configuration;
• the screw upper portion being uploaded through the opening by manual manipulation when the first and second keyed surfaces are in the alignment configuration;
• and
• c) a bushing positioned in the body member above and in contact with the screw upper portion and in contact with the body member, the bushing being in press fitment about the screw upper portion so that the body member and the bushing do not move freely prior to insertion and securement of the rod.

In a spinal screw assembly having a body member and a pedicle screw adapted to be adjusted to various angles of the pedicle screw relative to the body member during assembly and then locked in position with an elongate fixation member;

• the improvement wherein:
• a) the body member has an interior region defined by an interior surface and a lower opening that opens onto the interior surface;
• the opening having a first keyed surface;
• b) the pedicle screw has a lower threaded shank adapted to implant in a bone and an upper portion;
• the upper portion having a rounded head with an external second keyed surface;
• and wherein:
• c) the first and second keyed surfaces are sized and shaped so as to receive and allow passage of the upper portion through the opening only in an aligned configuration and wherein there is a non-aligned configuration wherein the upper portion cannot pass through the opening such that the pedicle screw upper portion is uploaded through the opening in the aligned configuration and than placed in the non-aligned configuration to allow angular movement of the pedicle screw relative to the body member while securing the pedicle screw upper portion in the body member;
• and
• d) further comprising a bushing having an upper elongate fixation member seating surface, an outer surface and a lower skirt, the outer surface being in contact with the interior surface of the body member, the lower skirt abutting opposed sides of the rounded screw head providing a press fitment about the screw head prior to insertion of the elongate fixation member.

A polyaxial fixation device comprising:

• a) a shank with a spherical head;
• b) an outer receiving member for receiving and polyaxially seating the spherical head of the shank, the receiving member having an axial passage formed therein and a rod receiving channel;
• and
• c) a compression bushing disposed within the receiving member and located between and adjacent the shank head and the rod, the bushing having a concave surface adapted to seat at least a portion of the spherical head of the shank and wherein a portion of the bushing has a diameter that is deformable to frictionally engage the spherical head in press fitment and also engage the receiving member when the fixation rod is not pressing against the bushing, with the shank head, the bushing and the receiving member being unable to move freely with respect to one another, requiring some force to move the shank into different angular orientations with respect to the receiving member when the fixation rod is not locked against the bushing.

A polyaxial fixation assembly comprising:

• a) a shank having a spherical head;
• b) an outer receiving member having a first opening for receiving a spinal fixation rod and a second opening having a diameter sized to permit passage of the shank there through while maintaining the spherical head therein, the receiving member further having a spherical seat adjacent the second opening to polyaxially seat the spherical head of the shank;
• and
• c) a compression bushing for frictionally engaging the spherical head to maintain the shank in a desired angular orientation prior to locking with the spinal fixation rod such that a force greater than a frictional engagement force is required to change the angular orientation of the shank with respect to the receiver member, wherein at least a portion of the compression bushing has a diameter that is deformable to frictionally engage the spherical head and the receiver.

A polyaxial fixation assembly comprising:

• a) a shank having a spherical head;
• b) an outer receiving member having a first opening for receiving a spinal fixation rod and a second opening having a diameter sized to permit passage of the shank there through while maintaining the spherical head therein, the receiving member further having a spherical seating surface adjacent the second opening to polyaxially seat the spherical head of the shank and an interior surface with a first width;
• and
• c) a compression bushing for frictionally engaging the spherical head to maintain the shank in a desired angular orientation prior to locking with the spinal fixation rod such that a force greater than a frictional engagement force is required to change the angular orientation of the shank with respect to the receiver member, wherein at least a portion of the compression bushing has a second width greater than the first width to provide a press fitment between the bushing and the receiver and a frictional engagement between the spherical head and the receiver.