| 摘要 |
A polyaxial bone anchor includes an anchor head, an anchor member, a bushing, a sleeve and a fastener. The anchor head has a longitudinal bore and an inner spherical surface on a lower portion. The bushing is received within the longitudinal bore adjacent the lower portion and includes an exterior spherical surface for interacting with the inner spherical surface in the anchor head, an internal space defining an inner spherical surface for mating with a spherical head portion of the anchor member and a slot. The inner spherical surface of the bushing has a spherical centerpoint and the exterior spherical surface of the bushing has a spherical centerpoint. The spherical centerpoint of the inner spherical surface is vertically displaced toward the bottom end relative to the spherical centerpoint of the exterior spherical surface. The sleeve is received within the longitudinal bore. The fastener is mountable to the anchor head. |
