| 摘要 |
A top loading polyaxial spinal rod screw assembly is configured for simultaneous or one step lockup of angular orientation of a rod holder portion of the screw assembly relative to a bone screw and of a spinal rod within the rod holder portion of the screw assembly. The spinal rod and the angular orientation of the rod holder holding the spinal rod are thus fixed upon receipt of a lockup component of the present assembly. Components of the present spinal rod screw assembly cooperate to allow reception of a spinal rod in a rod holder that is adapted for pivotal retention on a bone screw and to lock or fix the spinal rod within the rod holder while also locking or fixing the angular orientation of the rod holder relative to the bone screw upon receipt of a lockup cap component of the screw assembly in the rod holder. In one form, the present screw assembly is defined by a three-piece polyaxial screw head assembly for a bone screw. The three-piece polyaxial screw head assembly includes a spine rod holder or head configured for pivotal connection with the bone screw, a head insert configured for reception in the spine rod holder, and a lockup (end) cap configured for reception in the spine rod holder. The lockup cap is configured to interact with the head insert to fix an angular position or orientation of the spine rod holder relative to the bone screw at the same time as fixing a spinal rod that has been received in the spine rod holder relative to the spine rod holder. |
