Patent ID: 7445627
Filing Date: 2008-11-04
Classification: A61B

Abstract:
1. A pedicle screw assembly comprising: a threaded screw, the screw having a threaded portion, a spherical head and an interface for driving the screw; a tulip assembly including a tulip body and an inner tulip member slideably disposed within said tulip body, the tulip body having non-circular surface disposed on an outer surface, a fastener coupled to the tulip assembly and positionable to retain the tulip assembly on the head of the screw, wherein said fastener comprises a compression ring including a split in the ring, wherein said fastener is configured to vary from a first diameter to a second diameter to receive and be positioned around at least a part of the head portion of said threaded screw; and a cap having an outer surface and a plurality of graduated compression tabs, wherein said plurality of graduated compression tabs are configured to mateably connect to said non-circular surface to compress said tulip assembly; wherein said cap further comprises a plurality of protruding members on an inner surface of said cap, said protruding members being configured to selectively engage said inner tulip member and impart a translating force on said inner tulip member when said cap is rotated; wherein said tulip body includes an internal wall region defining a bore, said bore being configured to receive said fastener and said inner tulip member, said bore extending from a top region of the tulip to a lower region of the tulip, said bore being sized to receive said spherical head of said screw, and said bore including an expansion channel shaped to facilitate coupling of said fastener to said spherical head of said screw when inserted in said bore, wherein said expansion channel further comprises a seating taper disposed on a lower portion of said expansion channel, and a taper disposed on a lower portion of said fastener corresponding to said seating taper, wherein said seating taper and said taper on said fastener are configured to engage to constrict said fastener about said spherical head of said screw; wherein said inner tulip member is coupled in said tulip body adjacent to said fastener such that a downward translation of said inner tulip member translates said fastener into a seating taper; wherein said protruding members are configured to impart said translating force on said inner tulip member sufficient to seat said fastener in said seating taper to lock an angular position of said tulip assembly relative to said threaded screw; and wherein said cap has a first position and a second retained position, said first cap position engaging said protruding members and said inner tulip member sufficient to lock a relative angle between said tulip assembly and said threaded screw, and said second retained position engaging said graduated compression tabs with said non-circular surface of said tulip body to compress said tulip assembly sufficient to lock a rod within said tulip assembly.