US Patent 8066744 Keyed crown orientation for multi-axial screws

A coupling assembly may include an anchor member, a receiver member, and a seat member. The receiver member may have an anchor member end that cooperates with the anchor member and may have an implant receiving aperture for receiving an implant. The seat member may be disposable within the receiver member between the anchor member and the implant receiving aperture. First and second rotation-limiting features may be engageable to limit rotation of the seat member relative to the receiver member.