Polyaxial bone screw with multi-part shank retainer and pressure insert
First Claim
Patent Images
1. A polyaxial bone screw assembly comprising:
- a) a shank having an elongate body and an integral upper portion, the body configured for fixation to a bone;
b) a receiver having a top portion and a base, the receiver top portion defining an open channel, the base having a seating surface partially defining a cavity, the channel communicating with the cavity, the cavity communicating with an exterior of the base through an opening sized and shaped to receive at least the shank body therethrough;
c) a retainer structure having at least two discrete parts, each part having a top surface, an inner surface and an outer surface, the inner surface configured to be in contact with the shank upper portion and the outer surface configured to be in polyaxially slidable engagement with the receiver seating surface when the retainer structure is captured between the shank upper portion and the seating surface, the shank upper portion having an upper end surface spaced above the retainer structure top surface; and
d) a compression insert disposed within the receiver also spaced above the retainer structure and configured to frictionally engage the shank upper end surface.
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Abstract
A polyaxial bone screw assembly includes a threaded shank body having an upper portion, a receiver, a compression insert and an articulation structure made from at least two discrete pieces. The shank upper portion cooperates with the compression insert to place the retainer in frictional engagement with the receiver. The geometry of the retainer structure pieces corresponds and cooperates with the external geometry of the shank upper portion to frictionally envelope the retainer structure between the capture structure and an internal surface defining a cavity of the receiver.
184 Citations
22 Claims
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1. A polyaxial bone screw assembly comprising:
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a) a shank having an elongate body and an integral upper portion, the body configured for fixation to a bone; b) a receiver having a top portion and a base, the receiver top portion defining an open channel, the base having a seating surface partially defining a cavity, the channel communicating with the cavity, the cavity communicating with an exterior of the base through an opening sized and shaped to receive at least the shank body therethrough; c) a retainer structure having at least two discrete parts, each part having a top surface, an inner surface and an outer surface, the inner surface configured to be in contact with the shank upper portion and the outer surface configured to be in polyaxially slidable engagement with the receiver seating surface when the retainer structure is captured between the shank upper portion and the seating surface, the shank upper portion having an upper end surface spaced above the retainer structure top surface; and d) a compression insert disposed within the receiver also spaced above the retainer structure and configured to frictionally engage the shank upper end surface. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. In a polyaxial bone screw assembly for surgical implantation and including a shank and a threaded body for inserting into a bone and a receiver having a channel for receiving a longitudinal connecting member within the channel, the improvement wherein
a) the shank has an upper end portion with a first top curvate surface and at least a first exterior surface disposed adjacent to the first top curvate surface; - and further comprising;
b) a two piece retainer structure located between the shank upper end portion and the receiver, the pieces having respective exterior facing second and third curvate surfaces, the pieces having respective opposed second and third surfaces, the retainer structure being in polyaxial slidable engagement with the receiver at the second and third curvate surfaces and at least one of the second and third opposed surfaces being in contact with the shank first exterior surface; and c) a compression insert having a fourth curvate surface in slidable engagement with the shank first top curvate surface. - View Dependent Claims (17, 18, 19, 20)
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21. In a bone screw assembly having a receiver pivotally connected to a bone screw shank, the receiver having an opening for receiving a longitudinal connecting member and a compression insert disposed in the receiver for frictional engagement with the longitudinal connection member, the improvement comprising:
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a) resilient structure extending from the receiver and biasing against the compression insert, the resilient structure prohibiting rotational movement of the compression insert within the receiver; and b) an articulation structure having more than one discrete piece, the articulation structure being disposed between the bone screw shank and the receiver, the articulation structure having outer curvate surfaces in pivotal engagement with the receiver and inner surfaces in contact with the bone screw shank, the articulation structure being located below a top surface of the shank. - View Dependent Claims (22)
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Specification