Patent ID: 8685064
Filing Date: 2014-04-01
Classification: A61B,Y10T

Abstract:
1. A polyaxial bone anchor, comprising: a modular housing including an upper housing and a lower housing rotatably coupled to the upper housing, the modular housing having an upper end, a lower end and a bore extending through the modular housing from the upper end to the lower end, the bore opening out at the lower end at a lower opening of the lower housing, the upper housing of the modular housing including a channel configured for receiving an elongate stabilization member therethrough which extends from a first side surface of the upper housing to a second side surface of the upper housing opposite the first side surface transverse to the bore; a bone screw including a spherical head and a shank extending from the spherical head, the spherical head of the bone screw positionable in the lower housing with the shank extending from the lower end of the housing, the lower opening of the bore defining an angulation limit of the bone screw for each azimuthal angle around a longitudinal axis of the bore, wherein a maximum angulation limit relative to the longitudinal axis of the bore is greater at a first azimuthal angle than at a second azimuthal angle; a seat member positioned in the bore, the seat member including a concave lower surface contacting the spherical head of the bone screw; and a wave washer positioned in the bore and pressing against the seat member, the wave washer biasing the concave surface of the seat member against the spherical head of the bone screw to provide frictional engagement between the seat member and the spherical head of the bone screw to resist pivotable movement of the modular housing with respect to the bone screw prior to securing an elongate stabilization member in the channel of the upper housing; wherein the modular housing is configured to provide limited rotational movement between the upper housing and lower housing through less than 360 degrees; and wherein one of the upper housing and the lower housing includes a groove and the other of the upper housing and the lower housing includes a protuberance, the groove having a first end surface and a second end surface and the protuberance traveling in the groove between the first end surface and the second end surface, wherein rotation between the upper housing and the lower housing is limited by the protuberance contacting either the first end surface of the groove or the second end surface of the groove.