Patent attributes
A pivotal spinal fixation system includes bone anchors comprising capture portions having a partial spherical shape with flat side surfaces, multi-planar receivers with continuous interior circumferential engagement surfaces proximate their bottom openings, and uni-planar receivers with non-continuous interior circumferential engagement surface proximate their bottom openings. The system also includes circular retainers, each having a non-continuous outer circumferential surface configured for non-pivotal engagement with the interior circumferential engagement surfaces of both the multi-planar receivers and the uni-planar receivers, and an inner surface configured to expand and contract around the capture portion and flat side surfaces of a bone anchor so as to capture the bone anchor within a multi-planar or uni-planar receiver. The system provides for pivotal motion of the bone anchors in any of a plurality of angular directions relative to the vertical centerline axes of the multi-planar receivers while limiting pivotal motion to a single pivot plane relative to the vertical centerline axes of the uni-planar receivers.
