Polyaxial bone fixation element

摘要

The present disclosure includes a polyaxial bone fixation element for use in spinal fixation to interconnect a longitudinal spinal rod with a patient's vertebra. The polyaxial bone fixation element preferably includes a bone anchor, a collet, a body, and a locking cap. The polyaxial bone fixation element preferably enables in-situ assembly. That is, the polyaxial bone fixation element is preferably configured so that in use, the bone anchor may be secured to the patient's vertebra prior to being received within the body. Accordingly, the polyaxial bone fixation element enables a surgeon to implant the bone anchor without the body to maximize visibility and access around the anchoring site. Once the bone anchor has been secured to the patient's vertebra, the body can be snapped-onto the bone anchor. The bone anchor preferably also includes a second tool interface so that a surgical instrument can be directly coupled to the bone anchor.

主权项

1. A method for securing a rod to a bone fixation assembly, the method comprising the steps of:
inserting a head of a bone anchor into a collet; after the inserting step, implanting the bone anchor into a vertebral body so that a threaded shaft of the bone anchor is engaged with the vertebral body and the collet is spaced away from the vertebral body; positioning the collet in a bore of a body in a loading position such that the collet is in an enlarged diameter portion of the bore, wherein when the collet is in the loading position, the collet is polyaxially rotatable relative to the bone anchor; and causing the collet to move along a direction from the loading position to a locking position such that the collet is in contact with a spherical undercut of the body that: 1) is in the bore, 2) extends in the direction such that the spherical undercut defines a length measured along the direction, and 3) is spaced from the enlarged diameter portion, wherein when the collet is in the locking position the collet is fixed to the bone anchor with respect to relative polyaxial rotation.