Spinal correction system with multi-stage locking mechanism

摘要

In a rod fixation system of the type used to treat various spinal conditions, the same fastener is used to lock both a polyaxial screw and a rod in position. A spinal correction device according to the invention, adapted for use with a rod and a polyaxial screw having a ball-shaped head and a threaded end, comprises a head-body and a cap. The head-body includes a lower internal cavity to receive the ball-shaped head of the screw, an upper bore to receive a fixation rod therethrough, and an upper end configured to receive the cap. The head-body and the cap are configured such that a first rotation of the cap locks the polyaxial screw in position, and a second rotation of the cap locks the rod in position. In the preferred embodiment, the head-body includes one or more gaps to facilitate flexion of the head-body as a rotational torque is placed on the cap. The gap or gaps may be horizontal, vertical or other angles relative to the axis of the entrapped rod.

主权项

1. A spinal correction device adapted for use with a rod and a polyaxial screw having a ball-shaped head and a threaded end, the device comprising:
a head-body and a cap, the head-body having a lower internal cavity to receive the ball-shaped head of the screw, an upper bore to receive a fixation rod therethrough, and an upper end configured to receive the unthreaded cap, wherein the cap comprises a cap rim, wherein the head-body comprises a head-body rim, and wherein the cap rim is configured to mate with and engage the head-body rim, wherein the cap rim varies in thickness around at least a portion of the perimeter of the cap, wherein the cap rim comprises at least one tapering section in which the cap rim thickness gradually varies; wherein the head-body and the unthreaded cap are configured such that:
a first rotation of the unthreaded cap locks the polyaxial screw in position, anda second rotation of the unthreaded cap locks the rod in position.