Offset connection bone anchor assembly

摘要

A bone anchor assembly for coupling an offset bone anchor with a previously inserted spinal fixation element and method of use is provided. Exemplary embodiments of a bone anchor assembly are particularly suited for use in a rod-first spinal surgical technique in which a bone anchor inserted into a patient vertebra may be separated from a previously inserted spinal fixation element by a separation distance.

主权项

1. A bone anchor assembly for spanning a separation distance to connect laterally with a spinal fixation element, the assembly comprising:
a bone anchor comprising:
a shaft having:
an engagement portion for engaging bone disposed at a distal end of the shaft,an extension portion disposed at a proximal end of the shaft, the extension portion having a length greater than a cross-sectional height of the spinal fixation element; anda central axis extending through the engagement portion of the shaft and the extension portion of the shaft; anda seat element disposed between the engagement portion of the shaft and the extension portion of the shaft, the seat element having:
a profile flared in the direction of the proximal end of the shaft, wherein the profile is flared to provide a continuous angled surface extending from an outer edge of the seat to the shaft; and
an elliptical top surface configured to be substantially flat to seat a previously inserted spinal fixation element separated from the shaft by the separation distance and facing the proximal end of the shaft, the top surface of the seat element having a first seat distance, in a first direction wherein the first seat distance is greater than or about equal to the sum of half of a cross-sectional width of the spinal fixation element, a radius of the shaft and 2 mm, wherein the first seat distance is the radial distance between the central axis of the bone anchor shaft and an outer edge of the top surface of the seat element in the first direction.