Pedicle Screw Assembly
First Claim
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1. A pedicle screw assembly, comprising:
- an elongated screw having an enlarged ball end;
an upper housing part having an axial bore therethrough and having a lower counterbore, and a downward facing annular surface joining the bore and the counterbore, the upper housing part having two upward extending arms separated by a central slot for receiving an elongated member transversely through the slot, the slot having a bottom;
a lower housing part having a lower opening through which the screw is received, the lower housing part having a lower seat located above the lower opening, the lower seat being shaped complementary to the ball end for receiving the ball end;
a sleeve having a lower larger diameter end portion received in the counterbore of the upper housing part, and an upper smaller diameter end portion received in the bore of the upper housing part, the sleeve having an upward facing annular shelf joining the larger and smaller diameter portions, the sleeve having an upper seat defined on a lower end of the sleeve, the upper seat being shaped complementary to the ball end for receiving the ball end; and
an annular wave spring disposed concentrically about the upper smaller diameter end portion of the sleeve and sandwiched between the downward facing annular surface of the upper housing part and the upward facing annular surface of the sleeve;
wherein the sleeve is axially slidable relative to the upper housing part and the annular wave spring is dimensioned to provide a frictional pre-load on the ball end sandwiched between the upper and lower seats prior to the fixation of the elongated member in the upper housing part.
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Abstract
A pedicle screw assembly includes an elongated bone screw having an enlarged ball end. First and second seats are disposed on opposite sides of the ball end so that the ball is received between and seated within the first and second seats. An annular wave spring resiliently biases the first seat toward the second seat so as to provide a pre-clamping frictional engagement between the seats and the ball end to hold the seats in a selected position relative to the ball end.
30 Citations
18 Claims
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1. A pedicle screw assembly, comprising:
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an elongated screw having an enlarged ball end; an upper housing part having an axial bore therethrough and having a lower counterbore, and a downward facing annular surface joining the bore and the counterbore, the upper housing part having two upward extending arms separated by a central slot for receiving an elongated member transversely through the slot, the slot having a bottom; a lower housing part having a lower opening through which the screw is received, the lower housing part having a lower seat located above the lower opening, the lower seat being shaped complementary to the ball end for receiving the ball end; a sleeve having a lower larger diameter end portion received in the counterbore of the upper housing part, and an upper smaller diameter end portion received in the bore of the upper housing part, the sleeve having an upward facing annular shelf joining the larger and smaller diameter portions, the sleeve having an upper seat defined on a lower end of the sleeve, the upper seat being shaped complementary to the ball end for receiving the ball end; and an annular wave spring disposed concentrically about the upper smaller diameter end portion of the sleeve and sandwiched between the downward facing annular surface of the upper housing part and the upward facing annular surface of the sleeve; wherein the sleeve is axially slidable relative to the upper housing part and the annular wave spring is dimensioned to provide a frictional pre-load on the ball end sandwiched between the upper and lower seats prior to the fixation of the elongated member in the upper housing part. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A pedicle screw assembly, comprising:
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an elongated bone screw having an enlarged ball end; first and second seats disposed on opposite sides of the ball end, so that the ball end is received between and seated within the first and second seats; an annular wave spring resiliently biasing the first seat toward the second seat so as to provide a pre-clamping frictional engagement between the seats and the ball end to hold the seats in a selected position relative to the ball end; a housing containing the enlarged ball end and the first and second seats and the annular wave spring, the housing having longitudinally extending arms with a slot between the arms, the arms having internal threads; and an externally threaded nut engaged with the internal threads of the arms for simultaneously clamping a reinforcing rod in the slot and clamping the ball end in place between the first and second seats. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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15. A method of manufacturing a pedicle screw assembly, comprising:
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(a) assembling an elongated screw having a ball end between first and second seats shaped complementary to the ball end; and (b) pre-loading the seats toward each other with an annular wave spring to provide a pre-clamping frictional engagement of the ball end with the seats, so that a housing containing the seats will remain in a selected position relative to the ball end prior to applying a final clamping force to the seats. - View Dependent Claims (16, 17, 18)
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Specification