Bone screw

摘要

A bone fixation system with variable z-axis translation is provided. The system includes an outer tulip coupled to a bone fastener via a screw retainer. An inner tulip is coupled to the outer tulip such that the inner tulip is longitudinally movably relative to the outer tulip. The inner tulip includes a lock that provides a seat for a connecting rod. The inner tulip together with a seated rod is permitted to translate along the z-axis inside the outer tulip when in an unlocked position. Also in the unlocked position, the bone fastener is free to angulate relative to the outer tulip. The z-axis position of the inner tulip and rod relative to the outer tulip is fixed in a locked position. Also, in the locked position, the bone fastener is locked with respect to the outer tulip. The system may be adjusted between the locked and unlocked positions by way of a set screw.

主权项

1. A bone fixation system, comprising:
a bone fastener including:
a bone engaging portion; anda head connected to the bone engaging portion; an outer receiver having a proximal end, a distal end and a longitudinal axis; the outer receiver including:
a sidewall extending between the proximal end and the distal end and having an inner surface and an outer surface;an inner bore extending between a top opening at the proximal end and a bottom opening at the distal end;two oppositely disposed arms defined by the sidewall and at least one rod channel defined between the two arms; the at least one rod channel being interconnected with the top opening and the inner bore; a hole formed in each arm extending from the inner surface to the outer surface; a screw retainer sized to fit inside the outer receiver; the screw retainer including two oppositely disposed arms connected to a bone fastener receiving portion at a distal end; the screw retainer including at least one channel defined between the arms; each arm has an interlocking inner surface; the bone fastener being coupled to the screw retainer in the bone fastener receiving portion such that the bone faster is permitted to angulate in an unlocked configuration; an inner receiver sized to fit inside the outer receiver; the inner receiver including a base and two oppositely disposed arms extending upwardly from the base; the inner receiver includes at least one channel defined between the arms; each arm has an interlocking inner surface; each arm including a passageway having an opening at a proximal end of the inner receiver and extending to an opening at a distal end of the inner receiver; each passageway is sized and configured to receive an arm of the screw retainer within the passageway; the base of the inner receiver includes a lock-receiving portion having two oppositely disposed holes extending from an inside of the inner receiver outwardly into the passageways; the inner receiver being coupled to the outer receiver such that the inner receiver is movable longitudinally relative to the outer receiver; a lock located inside the lock-receiving portion of the inner receiver; the lock including a rod-receiving location having reduced entryway; the rod receiving location being sized and configured to receive a connecting rod; the lock includes two outwardly extending locking prongs having distal interlocking surfaces; the locking prongs being configured to extend into the holes in the inner receiver such that the distal interlocking surfaces of the locking prongs engage the interlocking inner surfaces of the screw retainer in a locked configuration; a set screw located between the arms of the inner receiver and having an interlocking outer surface configured to interlock with the interlocking inner surface of the arms of the inner receiver; an elongate connecting rod located between the channels of the inner receiver; wherein the bone fixation system includes an unlocked position in which the bone fastener angulates with respect to the outer receiver and the inner receiver is free to translate longitudinally with respect to the outer receiver; and a locked position in which the bone fastener and inner receiver are fixed with respect to the outer receiver.