US Patent 8002806 Bottom loading multi-axial screw assembly

Anchor assemblies are provided to secure one or more implants along the spinal column that include a retainer in a receiver member. The retainer is configured to distribute the forces exerted on the retainer toward the proximal end of the retainer where it may deform without deforming, distorting or altering the retainer where it supports the anchor member in the receiver member. The desired positioning of the anchor member relative to the retainer and receiver member can thus be attained even when the retainer is subject to deformation forces.